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Pilot Factory for 3D High Precision MID Assemblies

Final Report Summary - 3D-HIPMAS (Pilot Factory for 3D High Precision MID Assemblies)

Executive Summary:
The collaborative FP7-CP-FP 3D-HiPMAS targets the development of a platform for manufacturing of low cost and 3D high precision MID Assemblies. 3D-HiPMAS addresses important branches like e.g. communication, transportation, life sciences and energy. MID technology was improved far beyond state-of-the-art focusing on 4 key technological building blocks:
• Plastic materials and injection molding for 3D high precision plastic micro parts.
• Ultrafine pitch metal line patterning.
• High precision 3D assembling of electronic and micro devices.
• Robust monitoring and quality inspection.
For 3D system carriers new LDS materials (LCP, PEEK, PPA) suited for patterning of ultrafine pitch metal lines were developed and characterized comprehensively by physical, rheological and microstructure analysis as well as injection molding of plastic test devices. Additional processes as e.g. heat & cool technology were used to set up an innovative 2-shot mold to enhance the quality of the final parts. Fine metal line pitches and vias could be realized by 2-shot injection molding process.
For 3D metal patterning of the 3D system carriers, a new laser system for fine pitch metal patterning for LDS (70 µm in 2D, 150 µm in 3D) was developed using a processing unit at 532 nm and a focus diameter of about 20 µm. Performance and accuracy of the LDS machine tool was improved with an alternative beam deflection system resulting in the specified accuracy of <10 µm. A multi processing unit system was set up to improve processing time of laser structuring. New processes for fine pitch metal deposition on MID have been developed using improved cleaning processes (chemical, CO2 snow jet) as well as electroless plating processes for Cu/Ag and Cu/Pd/Au. Suitable adhesion and roughness values of the fine pitch metal lines on the new LDS materials were obtained.
For achieving high precision and high throughput in 3D high precision assembling of complex MID new handling and processing modules and a new base machine OurPlantX3 were developed. A laser soldering tool and sorting process for loose material was implemented in existing machinery. For 3D joining a flip chip assembly process for 80 µm pitch and an SMD assembly process for lead free oven soldering as well as laser soldering of 0201 devices and 500 µm pitch QFN was successfully developed. High accuracy assembly of micro optical devices could be verified with molded micro lenses on new MID substrates.
For process and quality control an innovative X-ray inspection system was developed. An advanced software platform for engineers to develop MID products including process and quality management was set up. For advanced process and product quality control of MID an approach was developed.
Using the new developed hardware and processes a pilot line for MID production was set up at HAHN-SCHICKARD. For demonstration and characterization of the pilot line 4 demonstrators representing 4 different branches were developed: Fuel cell, 3D micro hearing aid device, micro switch and pressure sensor. All demonstrators were fabricated on the pilot line and comprehensively characterized. For platform building block deployment in Europe guidelines for pilot production were worked out. Furthermore a daughter platform was created in France (http://www.s-2p.com). Finally a contest for MID products to be manufactured on the pilot line was organized. The winner of the contest was the LEGO Group.

Project Context and Objectives:
Due to the high potential of miniaturization and integration, with regard to the innovation degree, quality and sustainability requirements, the 21st century looks forward to the integration of new functions on plastic parts to produce smart plastic products. Molded Interconnected Devices (MID) combine all the features of molded plastic parts with electrical circuitry and electronic components assembled directly on the plastic package and are well suited for fabrication of smart plastic based 3D high precision assemblies. MID do not replace conventional PCB but open new possibilities for advanced products and provide e.g. the following advantages:
• Miniaturisation
• 3D design freedom
• Integration of new, complex and additional functions
• Versatile options for assembly of SMD and bare dies (sensors, actuators, signal processing,...)
• Reduction of components
• Reduction of process steps and tolerance chain
In Figure 2 1 versatile functions of MID in hybrid miniaturised mechatronic systems are summarized.

Compared to PCB technology there are some differences in MID technology. The usage of thermoplastics as substrate materials results in geometry depending properties and anisotropic properties of the 3D system carrier which has to be considered in the product design phase as well as the thermal stability of the materials. Also the comparatively high coefficients of thermal expansion of some MID substrate materials compared to PCB have to be considered. Compared to PCB the metal lines on MID are usually rougher and have a lower thickness because normally electroless plating technologies are used for generating the circuitry. Due to the 3D geometry of the MID the assembly process needs some adaption. Individual handling equipment and machine setup is required as assembly has often to be carried out on inclined or uneven surfaces, into cavities or near barriers. The process flow is more complex with additional and different process steps as well as referencing has often to be carried out on molded plastic structures.
3D-HiPMAS targets on improving MID technology far beyond state of the art focusing on 4 key technological building blocks:
• Plastic materials and injection molding for 3D high precision plastic micro parts.
• Ultrafine pitch metal line patterning.
• High precision 3D assembling of electronic and micro devices.
• Robust monitoring and quality inspection.
Beside the progress in technological performance significant improvements in yield and quality, consumption of energy and materials, waste and production time reduce product cost. Progress achieved in 3D-HiPMAS was demonstrated by setting up a pilot factory for 3D high precision MID assemblies and fabricating demonstrators of upcoming innovative products for important branches of the industry: Energy, Medical, Telecom and Automotive.

The objectives of the project focus on improving MID fabrication technology by:
• Plastic materials for Laser Direct Structuring (LDS), e. g. for lower pitch and roughness of metal lines, lower wall thickness and good adhesion.
• Improved injection molding for LDS and 2-shot MID with lower wall thickness and reduced feature sizes.
• Laser equipment for high resolution, high accuracy, high speed machining.
• Metal deposition for ultrafine pitch MID metal lines at reduced chemicals and metals consumption.
• Assembling machinery and processes with improved 3D capability and accuracy at higher throughput.
• X-ray inspection for defect monitoring of high precision MID assemblies.
• Workbench software tools for design and monitoring of MID assembly production.

Using the improved fabrication technology 4 advanced demonstrator devices were developed:
• Fuel cell using MID assembly for integration of electronics, sensors and mechanical packaging.
• Hearing aid using MID based connector device with spring loaded contacts and electric circuitry.
• Micro switch using MID based assembly for improved RF performance, reduced number of parts and assembling cost.
• MID based pressure sensor for automotive applications.

3D-HiPMAS fabrication technology and the innovative demonstrators were characterized to make the technology available to European industry:
• Set up of a pilot factory for 3D high precision MID assemblies in Stuttgart.
• Fabrication and characterization of the demonstrator devices.
• Assessment of the new 3D-HiPMAS technology.
• Preparation for use by industry and for spin off daughter pilot lines in France and other locations in Europe.

Project Results:
3.1 Work Package 1: Technical specifications and design concepts
The main objectives of work package 1 are:
• To define the specifications and constraints of each demonstrator.
• To define the needed building blocks related to different demonstrators.
• To define industrial validation protocols to be used for demonstration in work package 6.
• To define design concepts for the demonstrators.
First, the requirements and constraints of all demonstrators (fuel cell (PRAGMA), hearing aid (SONOVA), micro switch (RADIALL), pressure sensor (RAYCE)) were compiled to do the links between end users and process suppliers. The requirements covered e.g. mechanical, thermal, electrical and environmental aspects. The specifications were associated to the key technological building blocks to be developed in 3D-HiPMAS.
On this basis the first design concept of each demonstrator was worked out. The main role of the demonstrators is to prove the processes used in fabricating an MID based assembly:
• 3D system carrier
• 3D fine pitch tracks realization
• 3D assembling of components
As the 3D design has a high complexity with necessary tolerance constraints on assembly parts, the demonstrators will also allow validating the control process.
Figure 3 1 shows the final design concept of the fuel cell MID assembly. This concept allows to realize an on the shelf electrical connector. It is totally isolated from hydrogen so that there is no risk of leakage.

Figure 3 1: Final concept fuel cell MID assembly
The main technical challenges for the MID based hearing aid demonstrator concept were summarized in Figure 3 2. In order to assess those challenges and to minimize the risks for the demonstrator in work package 6 a test part for preliminary analyses was designed. The design concept for a hearing aid demonstrator was finalized as a connector part for an audio shoe. The main findings and conclusions can be summarized as follows:
• The design and manufacture of an injection molding tool for a test part allowed to prototype most of the challenging features of the final demonstrator in order to reduce risks. Main focus was on the manufacturing of vias and the design of contact spring elements made from LDS structured plastic.
• Mechanical testing of the contact elements showed that the design concept works and that such an electromechanical connector is possible to realize in MID technology. The conductive tracks did not show any mechanical degradation (cracks, abrasion,...) after the specified cycling.
• Exposure to synthetic sweat in a laboratory environment confirmed that possible corrosion remains the largest risk for an application of MID technology in a hearing aid.

Figure 3 2: Concept for MID based hearing aid demonstrator
The micro switch demonstrator concept is composed by RF access lines. The goal of the project is to improve the RF performance of the micro switch. The design of the part is based on several criteria:
• The microwave block could have the same footprint as the existing product which is done in classical PCB technology.
• The RF lines must be isolated from the environment to reduce the RF leakage towards the external environment and from the other lines in order to have better RF performances at high frequency.
• Each access must be isolated from the other to permit a good isolation between accesses.
• The RF line must be matched from the beginning (as soon as the signal leaves the board and enters in the micro switch) until the end (when the signal leaves the micro switch to return on the board).
• Avoidance of all parasitic elements (e.g. capacity, inductivity or stub) if possible.
A first design has been proposed (Figure 3 3) to validate all criteria.

Figure 3 3: Micro switch concept developed in 3D-HiPMAS
For a new optical pressure sensor demonstrator three main parts were identified:
• Optical simulation and design
• Electronics interface conception
• Mechanical and electronics conception
The design was done in accordance with the specifications. At the end of the different design phases on optical, mechanical, packaging and electronics, it was proved that the main risks for industrialization are:
• Global size of the packaging
• Miniaturization of the electronics interface board
• Temperature limit of existent components for the optical receiver
• Necessity to redefine constraints on MID part
• Economic constraints
The optical studies confirmed that the tolerance needs for the system could not be realized cost efficiently by molding technology so that from market point of view the optical principle for the pressure sensor is not suitable. Therefore a demonstrator concept based on a capacitive principle was worked out. Furthermore a concept of an MID based strain gauge was worked out.
The mechanical design used to validate the concept of the capacitive pressure sensor is shown in Figure 3 4. Test parts were built up and characterized.

Figure 3 4: First concept of an MID based pressure sensor
In summary the following steps were validated for the pressure sensor demonstrator:
• Packaging and mechanical definition
• Sealing and assembly concept definition
• Electronic function development
• Setup of functional demonstrators
• Characterization
The concept of an MID based strain gauge is shown in Figure 3 5. Fine metal line pitches enable the design of smaller conductive tracks. The meander structure itself acts as a classical resistive strain gauge which is placed on the surface of a plastic body. A deformation of the plastic body will create a change of the MID track resistivity. Thereby analysing of internal stress is possible. The aim is to be able to make a strain gauge on polymer parts for composite parts monitoring and design validation for automotive.

Figure 3 5: Concept of an MID based strain gauge for composite application (left) and design validation application (right)

3.2 Work Package 2: 3D system carrier
The main objectives of work package 2 are:
• To improve metal line pitch capability of the LDS plastic material (70 µm in 2D and 150 μm in 3D) including roughness, adhesion, thermal expansion and thermal conductivity.
• To optimize and upscale the compounding process of the new LDS materials for economic production of larger quantities with regard to reproducibility of the material properties.
• To keep the cost level of state-of-the-art plastic material at significantly improved performance.
• To improve mold and injection molding process of 3D system carriers for fine metal line pitches.
New LDS materials for 3D micro parts
Based on the overall project objectives as well as on the requirements of the demonstrators developed in 3D-HiPMAS the high performance thermoplastics PPA, LCP and PEEK were chosen as base polymers for the new LDS materials (Figure 3 6). To reduce thermal expansion of the plastic materials an enhanced amount of mineral filler was incorporated in the polymers. To meet the special requirements for laser direct structuring, special laser active additives were used as further component in the compounds.

Figure 3 6: Selection of matrix polymers for new LDS materials

In order to deliver carrier materials for fine pitch LDS structures, new LDS additives have been developed during 3D-HiPMAS. Basic research was done on the effect of different filler materials, such as nanotubes, ceramics and mineral fillers. The effects of chemical structure and particle size distribution of the fillers on the LDS performance was investigated. The compound materials were comprehensively characterized by plating tests after laser structuring and by measuring the adhesion strength and roughness of metal lines on the polymer surface. In addition, the mechanical properties as well as the thermal material properties like thermal expansion and thermal conductivity were determined. By applying microscopic analysis very fine dispersion of the additives and fillers was verified (Figure 3 7).

Figure 3 7: Fine dispersion of additives and fillers in the polymer matrix of new LDS materials

Besides material development, a focus was the development of a compounding process technology for fine pitch materials. The result is a special compounding technology that enables the manufacturing of high temperature polymer compounds with a special morphology to ensure realization of fine metal lines by LDS technology. The material quality is controlled by applying online measurements of filler degree and additive dispersion during compounding.
The results of the material development described above are new high performance compounds for the LDS technology with enhanced fine pitch capability. On the new materials very fine metal line pitches can be realized by LDS technology (Figure 3 8). Edge and surface roughness was significantly reduced compared to state of the art LDS plastics.

Figure 3 8: Fine metal lines on new LDS material

Especially the new developed LCP based material shows a very low thermal expansion, leading to high reliability of the polymer/metal-interface also during temperature changes. The data for thermal expansion at different temperature regions is given in Figure 3 9.

Figure 3 9: Coefficient of thermal linear expansion of new LDS materials

Figure 3 10: Thermal conductivity of new LDS materials
The new LDS materials based on PPA show enhanced thermal conductivity. As shown in Figure 3 10 the thermal conductivity is 5 – 10 times higher than the thermal conductivity of unfilled polymers. Therefore these plastic materials can also be used for heat management in for example LED lightings or as heat sinks in electronic applications.

Table 3 1 shows an overview of the new LDS materials developed in 3D-HiPMAS.

Table 3 1: Overview on new LDS materials from ENSINGER
Mold and injection molding technology for 3D micro parts
Within 3D-HiPMAS molds and injection molding technologies were developed in order to produce 3D micro parts. One of the goals of the injection molding technology development for 3D micro parts was to evaluate the process ability of the new LDS compounds developed in work package 2. Injection molding trials showed good behavior of the new compounds.
A second major objective was the development of a 2-shot molding process for manufacturing 3D-MID parts with small features. PEP developed a specific mold for 2-shot molding development associated to a specific test vehicle. The design of the test vehicle was defined in order to include the various objectives of the project in terms of metalized structures dimensions. The specifications were also related to the needs of the partners’ demonstrators. A first design of the test vehicle was made and simulation tools were used for the optimization of its design before manufacturing the 2-shot molding tool. First, a simulation tool was used for filling analysis, especially for the filling of the smallest structures. Shrinkage and solutions to transfer and center the insert in the overmolding cavity were also optimized by modifying the part design.

Figure 3 11: Filling simulation of optimized 1st shot

In order to have better control in the production of MID parts, sensor integration in the tool offers the opportunity to have a better control of the molding process. The good positioning of the sensor is directly related to the critical area to be controlled. For the test vehicle thermal sensors were integrated to control the end of filling. The evaluation of the different innovative technologies (rapid heat and cool, vacuum, etc.) for optimizing the replication of the small features was performed in association with the 2-shot molding process. The transfer on 2-shot molding was very challenging due to the small place available in the 2-shot tool and the LCP and PPA materials used. “Fluidic” heat and cool technology was selected. In order to optimize the heat and cool effect, the tool insert was made with conformal cooling channels. Cooling channels were optimized using simulation to ensure good flow in each channel. The manufacturing was done at PEP with Selective Laser Melting technology.

Figure 3 12: Tool for 2-shot demonstrator and fluidic analysis after channels optimization

First injection trials produced good results, i.e. no distortion of the first injected part, fully opened vias down to 0.15 mm in diameter and fully filled structures with 0.15 mm width, but also revealed some defects, e. g. the weakness of several areas of the first injected part inducing some distortion during the overmolding step. In order to overcome these defects, several modifications of the first injection molded part were performed: modification of the runner geometry, increasing of the thickness of several areas, stiffening of some microstructures, etc.
Several injection molding trials were performed with the modified mold with several combinations of materials. In the case of LCP (catalyst doped) / LCP combination, the injection temperature of the overmolding material was shown to be too high. As a consequence, the first injection molded part was still unacceptably distorted during the overmolding step. In order to overcome this limitation, new combinations of materials were tested. Materials with lower injection temperature were selected for the overmolding step, e.g. PC, ABS, PET, etc. Thereby it was possible to produce satisfactory 2-shot parts without noticeable distortion of the first injection molded part. Electroless plating was performed on the overmolded samples using an optimized metallization process. The metalized samples were characterized electrically and geometrically (Figure 3 13).

Figure 3 13: 2-shot molded LCP (catalyst doped) / ABS part after electroless plating (left) and 3D view of a metallized dot by 2-shot moulding (20X) (right)

With these 3D micro parts the possibility to create fine metalized structures by 2-shot molding was shown to be feasible. Fine pitches below 0.4 mm (0.2 mm line and 0.2 mm space) and fine vias below Ø 0.5 mm have been realized.

3.3 Work Package 3: 3D metal patterning
The main objectives of work package 3 are:
• To develop a new laser direct structuring machine for fine pitch sizes of 70 μm at 2D and 150 μm at 3D.
• To develop a new improved beam deflection system for improved positioning accuracy below 10 μm in combination with high scan speeds.
• To work out machining parameter sets for generating the metal lines on 3D system carriers from the new LDS material from work package 2 using the new LDS machine.
• To work out cleaning processes and parameters for fine pitch using new LDS material.
• To develop an enhanced plating process for fine pitch applications suited for high precision assembly using new LDS material with reduced consumption of chemicals and metals.
New laser system and process development
The heart of a LPKF LDS machine tool is the so called processing unit (PU). Every LDS machine tool can be equipped with up to three processing units. The PU incorporates the laser source, beam forming and beam deflection unit as well as a mechanically and thermally stable housing. Processing units of the state of the art are using a fibre laser with a wavelength of 1070 nm. This offers two advantages: due to the fibre set up a very compact design of the PU is possible. Additionally, fibre laser are inherently stable, the properties of the laser radiation at the output of the transport is very constant over a wide range of operating conditions.
The ultra-fine pitch LDS process requires a machine tool that provides a laser focus diameter half the size of the focus diameter in standard LDS. The focus diameter is proportional to three system parameters: the focal length of the focusing optics, the wavelength of the laser radiation and the inverse of the diameter of the input laser beam before focusing.
The input beam diameter is limited by the size of the mirrors inside the scanner unit used for beam deflection. The focal length of the focusing optics is proportional to the size of the scanning field, which creates a lower limit for this value. Therefore, the best way to reduce the focus size is to decrease the wavelength.
LPKF developed a processing unit for laser radiation of a wavelength of 532 nm. Before the actual system development started, processing tests with that wavelength were carried out. These tests showed only a slightly lower plating performance on a variety of materials especially on the highly interesting LCP than the standard wavelength of 1064 nm. Relatively low average laser power of below 1 W is sufficient to structure these polymers with a spot diameter of approximately 25 µm.
Figure 3 14 shows a concept drawing of the PU and a photograph of the finished system inside the 3D-HiPMAS base machine. In standard PUs, the laser source is integrated into the granite base of the machine and the radiation is guided to the PU by a glass fibre. In the finished ultra-fine pitch PU, the laser head is mounted onto the processing unit, which reduces footprint and complexity of the system. The laser head is passively cooled to avoid vibrations inside the processing unit. The beam is guided through the focus shifter unit into the galvanometer scanner. The combination of scanner and focus shifter allows a three-dimensional positioning of the beam in a volume of (x,y,z) 60x60x10 mm³ with a scanning speed of up to 1000 mm/s. The coaxial vision system consists of a polarization sensitive beam splitter and a CCD camera. It is used to control the position of the beam on the work piece.

Figure 3 14: Concept drawing of the ultra-fine pitch PU and photograph of the finished system inside the 3D HiPMAS base machine

The system implemented in the pilot line in work package 5 is based on the LPKF Fusion 1100. Apart from power supplies and electronics, it consists of a granite base, a housing with laser safety window, a work table attached to a manual z-axis with a digital position indicator and an exhaust unit. The processing speed is limited to 400 mm/s by the repetition rate of the laser source (max. 150 kHz) and the spatial pulse overlap required by the structuring process. This results in low processing speeds, especially for larger hatched areas.
The performance of the processing unit was evaluated by preparing metal features on plane work pieces using the LDS process. Most importantly, the accuracy of the system in three dimensions was measured. In summary, the ultra-fine pitch system achieved the specifications defined in the project:
• Diameter of focus: 20-25 µm
• Work space: 60 x 60 x 10 mm³
• Lateral accuracy at 40 X 40 mm² scanning field: < +/-10 µm
• Lateral accuracy at 60 X 60 mm² scanning field: < +/-20 µm
• Accuracy in z < +/- 150 µm (tolerances in ftheta)
• Scanning speed: 200 mm/s (limited by max. repetition rate)
• Repeatability < +/-10 µm
To improve the system’s throughput, LPKF set up and tested a system combining the new ultra-fine pitch PU for the generation of very fine metal lines with a standard PU for larger pads and other large structures (Figure 3 15). In addition, the ultra-fine pitch PU is improved by integrated a galvanometer scanner with better accuracy.

Figure 3 15: Multi PU system combining fine pitch (left) and standard processing units (right)

The performance of the multi PU system was tested using a structure made of a meander of lines with a pitch of 70 µm and two contact pads (Figure 3 16). The structuring of the contact pads is very slow with the ultra-fine pitch PU due to the small focus diameter. On the other hand, the pitch of the meander is too small for the standard PU.

Figure 3 16: Test structure for performance tests using the multi PU system

The system improvements result in an eightfold reduction of the processing time. The improved accuracy of the new system and process was also studied. Using the new galvo scanner and a CO2 snow jet cleaning step after laser processing to reduce surface roughness a 40 µm pitch was achieved on some substrate materials without any overplating (Figure 3 17). In addition, the new galvo scanner can potentially achieve speeds of 600 mm/s without reducing accuracy.

Figure 3 17: Best structuring results achieved in 3D-HiPMAS with a pitch of 40 µm
Cleaning and plating process development
For characterization of the cleaning and electroless plating processes developed at HAHN-SCHICKARD a test layout with a meander / comb structure with pads for electrical tests, circles for pull test and metal lines for roughness measurement and wire bonding test was developed (Figure 3 18).

Figure 3 18: Test layout on injection molded test plate

For cleaning of the laser patterned substrates wet chemical cleaning with ultrasonic support and CO2 snow jet cleaning have been investigated. The choice of the cleaning media for the wet chemical cleaning process was performed regarding that the catalytic activity of the laser patterned area was not significantly reduced. The CO2 snow jet cleaning is a dry process for removing the laser debris and also well suited to reduce surface roughness as well as to reduce edge roughness of the metal lines. As metal plating processes for fine pitch metal lines are needed, Cu/Ag was investigated as alternative to the well-known Cu/Ni/Au due to the less lateral growth of the finish layer. Furthermore, by using Cu/Ag process time is reduced as well as the consumption of chemicals and noble metals. Because of its advantageous properties for medical technology also Cu/Pd/Au was investigated.
First investigations were carried out on a state-of-the-art laser system with a focus of 65 µm. Finally the plating and cleaning process was investigated on substrates which have been laser patterned with the newly developed fine focus laser system.
For development of the Cu/Ag plating process on LDS substrates different electrolytes have been investigated. First the effect of a micro etching step as used for PCB plating after copper plating and before silver plating was investigated. Concerning adhesion between Cu and Ag it was found that best results were achieved by wet in wet processing without micro etching. The process parameters for the Ag plating process were optimized. Cross section-polishes showed that sub-surface migration and corrosion effects occurred when the Ag plating time is extended (Figure 3 19). Especially for fine metal lines adhesion is drastically reduced by such effects. But for the optimized process an adhesion of ca. 10 N/mm² (pull test with Dage 4000Plus) could be obtained.

Figure 3 19: Cross section-polish of Cu/Ag metal line on LDS LCP substrate: Ag plating time 2 min (left), Ag plating time 4 min (right)

The metal layers were characterized by SEM and EDX (Figure 3 20). No copper was detected on the metal lines and pads of the test structure surface.

Figure 3 20: EDX analysis of Cu/Ag on LDS LCP substrate

Also the Cu/Pd/Au plating process has been investigated on LDS substrates. Homogeneous Pd/Au layers could be obtained on Cu lines with low roughness as SEM and EDX analysis show (Figure 3 21). To reduce the roughness of the Cu lines CO2 snow jet cleaning after laser structuring was used.
Figure 3 22 shows a cross section-polish.

Figure 3 21: EDX analysis of Cu/Pd/Au on LDS LCP substrate

Figure 3 22: Cross section-polish of Cu/Pd/Au metal line on LDS LCP substrate
Based on the previous results cleaning and plating experiments were carried out on substrates laser patterned with the new ultra fine pitch laser machine. Different laser parameters were investigated. Adhesion values of ca. 8-10 N/mm² (pull test with Dage 4000Plus) were obtained on LCP together with roughness Rz values below 10 µm. Cross-section polishes are shown in Figure 3 23. CO2 snow jet cleaning enables smoother metal line surfaces compared to wet chemical cleaning. The realized metal line pitches on 2D and 3D substrates are shown in Figure 3 24. Special attention has to be turned on the surface quality of the injection molded substrates when ultrafine metal pitches are applied, e.g. blister and scratches have to be avoided.
Beside TECACOMP LCP black 4107 also for TECACOMP PEEK black 3980 and the TECACOMP PPA types laser parameter screening was carried out.

Figure 3 23: Cross section-polish of Cu/Ag metal line depending on cleaning process: CO2 snow jet cleaning parameter 1 (left), CO2 snow jet cleaning parameter 2 (left), wet chemical cleaning (right)

Figure 3 24: Metal lines with 70 µm pitch on 2D (left: Cu/Ag; middle: Cu/Pd/Au) and with 150 µm pitch on 3D LDS substrates (right)

3.4 Work Package 4: 3D high precision assembling
The main objectives of work package 4 are:
• To develop high precision and high throughput 3D assembly machinery with enhanced vertical stroke of 150 mm including new manipulating concepts for complex 3D system carriers, sorting process for loose material work parts and laser soldering tool.
• To develop new processes for joining of bare dies and SMD at fine pitch contact pad level and for joining of micromechanical/micro optical components at improved positioning precision.
New 3D assembly machinery
The new 3D assembly machine OurPlant X3 developed by HAECKER (Figure 3 25) is the first micro assembly platform, which can be customized to new production requirements. Several machining processes can run on one machine. All process functions are outsourced in mechatronic module units. These include all components and control panels that are required for the process function. Standardized interfaces allow a combination of all the process modules without any structural changes. This enables real plug & play capability. Main applications of the OurPlant X3 are micro assembly, micro dispensing and micro laser soldering.

Figure 3 25: New design of OurPlant X3

The benefits for the user are:
• Realization of complex processes through modularity
• Flexible and quick adaptation to process requirements
• Plug & play capability enables quick and easy conversion
• Open and standardized interfaces enable integration of in-house developments
• Double portal system enables short cycle times
• Saves acquisition, maintenance and repair costs by combining several machining processes in one machine
Joining process development
The new MID system carrier technology with fine pitch metal lines on substrates developed in work package 2 and 3 enables the assembly of smaller components like fine pitch bare dies and SMD as well as the high accuracy assembly of micromechanical/micro optical devices. The joining processes needed to be developed in order to achieve highest accuracy and reproducibility.
Based on appropriate test chips investigations on the chip and wire process for the fine pitch substrates have been carried out. First experiments on Al wire bonding on Cu/Ag were conducted using MID substrates with large pads. The experimental results showed that bondability on LDS MID with Cu/Ag is more critical than on Cu/Ni/Au. The process window is small. The small process window seems to be due to the decreased stability of the metal layer because of the reduced thickness. Despite that it could be found, that wire bondability on MID with Cu/Ag metallization is feasible in general, but fine pitch metal lines showed limited wire bondability.
Based on appropriate test chips also investigations on adhesive based flip chip bonding for the fine pitch substrates have been carried out. For the investigations on MID with 160 µm metal line pitch chips with Au stud bumps were used. Furthermore investigations on MID with 80 µm metal line pitch with chips with electroless plated Ni/Au bumps were carried out (Figure 3 26). Independent of the different setups, the flip chip assembly on MID proved to be a process with a wide process window, good reproducibility and good reliability.

Figure 3 26: Adhesive based flip chip assembly (80 µm pitch) on LDS MID substrate

In order to evaluate fine pitch SMD capability the whole process chain on 3D-HiPMAS MID was tested. MID substrates with the metal layer systems Cu/Ni/Au, Cu/Pd/Au and Cu/Ag were used. The reproducible application of solder paste was made by dispensing small depots of solder paste with maximum diameter of 300 µm suitable for assembly of 500 µm pitch devices. For characterization of the solder depot size a method for 3D measurement of the depots using confocal metrology with a chromatic sensor was developed. Figure 3 27 shows solder depots on metal lines of a typical LDS MID substrate and typical 3D measurement data of one depot.

Figure 3 27: Solder depots on metal lines of an LDS MID substrate (left) and typical 3D measurement data of one solder depot (right)

The pick and place process of 0201 SMD and 500µm QFN was setup fully automated. Lead-free reflow soldering under nitrogen in a convection oven was used. The results showed clearly that the assembly of such small SMD on MID is feasible (Figure 3 28).

Figure 3 28: 0201 SMD and 500 µm QFN on LDS MID substrates

In order to investigate the feasibility of laser soldering for SMD assembly on MID substrates detailed experiments were conducted on the new assembly machinery. The results showed that the assembly and laser soldering of small SMD on MID substrates is feasible.
Based on the developed alignment strategy, for investigating the achievable accuracy of the machinery in the assembly process for micromechanical and micro optical devices in an experimental setup molded lenses have been used. The experimental setup was designed to investigate the influence of the pick and place process with its elementary steps axis reproducibility, optical referencing before pick up, pick up of the device, placing the device and fixation by light curing adhesive. The lenses were assembled in 3x3 arrays (Figure 3 29). Afterwards for all lenses the deviations from measured positions to theoretically correct positions were determined. The results showed a mean deviation of 5 ± 3 µm. This proves the general capability of the 3D-HiPMAS pilot line machinery for high accuracy assembly of micromechanical and micro optical devices.

Figure 3 29: Molded lenses assembled on MID substrate

3.5 Work Package 5: Flexible 3D high precision MID platform
The main objectives of work package 5 are:
• To design the advanced flexible 3D high precision MID platform (pilot line) and optimize implementation in the existing facilities.
• To integrate the new hardware building blocks “3D system carrier”, “3D metal patterning”, “3D high precision assembly” and “process and quality control” and to start operation.
• To develop the tooling for low level automation and to develop tools for loading and unloading work pieces using carriers and loose materials.
• To optimize 3D-HiPMAS technology by setting up the pilot platform at Stuttgart.
First the design of the pilot line at the facilities of HAHN-SCHICKARD was worked out. The pilot line uses the processes existing at HAHN-SCHICKARD as well as the new and improved technologies developed in 3D-HiPMAS. An overview of the flow plan illustrates which processing options the 3D-HiPMAS pilot line offers to customers who are interested in MID production (Figure 3 30). The pilot line offers customers also to make use of single process building blocks instead of running the complete process sequence.

Figure 3 30: Overview flow plan for MID production

Detailed floor plans have been worked out showing how the pilot line equipment had been implemented in the HAHN-SCHICKARD facilities. The new fine focus laser developed by LPKF and the X-ray inspection machine developed by PSL were installed regarding effective sample transfer as well as optimised floor space consumption. Furthermore assembly machines installed at HAHN-SCHICKARD were rebuilt by HAECKER for the following features and implemented in the pilot line:
• laser protection class 1 and a working head for laser soldering
• vibration feeder for sorting loose material
• pick and place with a z-stroke of 150 mm
• 3D manipulator for handling 3D MID
• needle dispensing of dots with a diameter of 300 µm
Four demonstrators developed in work package 6 were used to set up the pilot line processes and to demonstrate advanced 3D MID production on the pilot line. For these demonstrators flow plans, flow charts and process sheets were worked out. All machines were put into operation and the personal at HAHN-SCHICKARD was trained on the new machines.
For low automated sample handling for the processes in pilot line production flexible work piece carriers (WPC) have been worked out fulfilling the following requirements:
• The WPC must be flexible and easily adaptable for a wide range of 3D MID.
• The WPC must fit to standard conveyor belts of assembling equipment at HAHN-SCHICKARD.
• The WPC carrier must be suitable for 2D and 3D assembling.
• The WPC must enable vacuum suction to hold 3D MID during assembling processes.
For every demonstrator a special fixture was developed and fabricated. Exemplarily the WPC for the pressure sensor demonstrator is shown in Figure 3 31.

Figure 3 31: WPC for pressure sensor demonstrator

For automated sorting of loose material a fully automated sorting process was integrated in the 3D assembly machine (Figure 3 32). Furthermore a process strategy for a fully automated sorting process was developed. All process steps have been successfully tested.

Figure 3 32: Vibration feeder for sorting loose material integrated in the 3D assembly machine

3.6 Work Package 6: Demonstration
The main objective of work package 6 is to demonstrate and characterize the new production platform using the new building blocks for developing, manufacturing and characterizing 4 demonstrators typical for 4 different branches:
• To design, manufacture and assess the fuel cell demonstrator.
• To design and manufacture the 3D micro hearing aid device demonstrator and to integrate the new MID carrier to hearing aid, verify and validate.
• To design, manufacture and characterize the micro switch demonstrator.
• To design, manufacture and characterize the pressure sensor demonstrator.
• To make an environmental assessment of the platform.
• To support the deployment of the platform and her building blocks.
• To transfer the 3D-HiPMAS results by creating a daughter platform at PEP.
Fuel cell demonstrator
PRAGMA developed a new fuel cell geometry using a roll-to-roll assembly process instead of a stacking process to reduce time and cost for production of fuel cells. MID technologies allow electronic components integration directly on the core of the fuel cell (Figure 3 33). Integration of sensors, smart fuel cell management and data logging functions increases the performance and reduces the need of external components.

Figure 3 33: MID integration into the “PowerCAN” fuel cell

The plastic part was injection molded with TECACOMP PPA LDS BLACK 4109 from ENSINGER by PEP. Laser structuring, cleaning and electroless plating with Cu/Ni/Au, electronic components assembly and inspection were realized by HAHN-SCHICKARD on the pilot line (Figure 3 34).

Figure 3 34: MID demonstrator

To challenge this solution, a second demonstrator using a screen printing process with Ag ink from CEA was investigated (Figure 3 35). It appears that this technology cannot be effectively applied to the needed fine metal lines.

Figure 3 35: Ag ink deposition results from CEA
3D Micro hearing aid device demonstrator
SONOVA developed an MID based connector for a miniature FM receiver to a hearing instrument and by doing so realized a highly integrated part. Compared to conventional electronic interconnection technology five individual parts like a frame, three springs and a flex print have been combined into only one part thus reducing several manual assembly steps (Figure 3 36).

Figure 3 36: MID based connector

Materialization of the MID part was done in the newly developed TECACOMP PEEK black 3980 with subsequent electroless plating with Cu/Pd/Au. This material combination was shown to perform best with regard to environmental reliability. Laser structuring, cleaning and electroless plating, SMD assembly and X-ray inspection of the MID were carried out in the pilot line at HAHN-SCHICKARD (Figure 3 37). In the next step the MID was assembled into the hearing aid (Figure 3 38). Functional verification of the MID demonstrator was finally done by successfully electrical and mechanical testing.

Figure 3 37: 3D Micro hearing aid device demonstrator after electroless plating (left), SMD assembly (middle) and X-ray inspection (right)

Figure 3 38: MID demonstrator part assembled in audio shoe and mounted onto a hearing aid
Micro switch demonstrator
A new concept of a micro switch based on LDS technology was realized and patented (Figure 3 39) by RADIALL. The new micro switch has good RF performances until 20 GHz in VSWR, insertion loss and isolation. It is compatible with a reflow soldering process and can be assembled on a PCB like a SMT component (Figure 3 40).

Figure 3 39: New micro switch using LDS technology

Figure 3 40 : Assembly of new micro switch on PCB
Laser structuring, cleaning and electroless plating, and X-ray inspection of the micro switch demonstrators were carried out in the pilot line at HAHN-SCHICKARD (Figure 3 41).

Figure 3 41: Micro switch demonstrators after laser structuring and electroless plating (left) and X-ray inspection (right)
Pressure sensor demonstrator
A new concept of a pressure sensor integrated in a Quick Connector (QC) with capacitive measurement technology (MID based capacitive pressure sensor) was developed by RAYCE (Figure 3 42). Therefore the pressure sensor design developed by HAHN-SCHICKARD was integrated on a QC with 13 mm internal diameter. MID technology was used for miniaturization and integration of the pressure sensor function on the clipping part. Thus value is added to the plastic by integrating fastening and measurement functions. The sensor was developed for 5 bars and 10 bar applications.

Figure 3 42: Capacitive pressure sensor integrated in QC
Figure 3 43: MID based strain gauge integrated on cable holder

Furthermore RAYCE worked on developing an MID based strain gauge (Figure 3 43) thanks to the improvement of metal line pitch done in the 3D-HiPMAS project. Laser structuring, cleaning and electroless plating, SMD assembly and X-ray inspection of the MID were carried out in the pilot line at HAHN-SCHICKARD (Figure 3 44).

Figure 3 44: Pressure sensor demonstrator after SMD assembly (left) and X-ray inspection (middle: top side with assembled SMD; right: bottom side with assembled membrane)
Environmental assessment of the platform
To evaluate 3D-HiPMAS technology regarding environmental aspects two demonstrator devices were compared:
• strain gauge “type 1” fabricated with state-of-the-art MID technology
• strain gauge “type 2” fabricated with 3D-HiPMAS MID technology
Thereby the miniaturization potential of 3D-HiPMAS technology was exemplarily shown, in particular by reducing metal line pitch by a factor of 2 (Figure 3 45). Furthermore wall thickness reduction can also contribute to miniaturization and reduction of material and energy consumption along the whole MID process chain.

Figure 3 45: Two types of strain gauges on tensile bars
Daughter platform
The daughter platform of the 3D-HiPMAS platform at HAHN-SCHICKARD was created at PEP. Based on the various technologies already available at PEP, this daughter platform enables the development of MID products either by LDS or by 2-shot molding. The goal of this daughter platform is to give to the industrial companies an easy access to different technologies for developing new MID products.
In terms of equipment, the daughter platform benefits from the broad range of injection molding machines available at PEP. Additional technologies for the improvement of the injection molding process are also available on the platform (heat and cool technology, vacuum technology etc.). For LDS technology the daughter platform uses a Microline 3D 160i equipment from LPKF. The chemical plating line is at laboratory level, allowing the production of MID prototypes or small series.
In order to increase the national and European visibility of the daughter platform, a start-up has been created, based on this activity: S2P (Smart Plastic Products). This start-up was officially created in November 2014 by two former researchers from PEP. S2P aims at providing in France the full process flow of a “Smart Plastic Product”, providing solutions for designing, manufacturing, qualification and technology transfer of the whole value chain of a product development: technological feasibility/proof of concept, prototyping, pre-series and industrialization. S2P also provides training services on MID technologies. In addition to the technologies of the daughter platform itself, S2P can benefit from the technologies available in the pilot line at HAHN-SCHICKARD.
In its strategy, S2P will continue to improve the daughter platform, in particular by developing new technologies, like plasma based technologies. These improvements will increase the capabilities of the platform and offer to companies more possibilities for developing new Smart Plastic Products. New plating lines with industrial size will also be built in order to enable the production of larger quantities of devices.
For the time being, the activity of the daughter platform is steadily increasing, with more and more industrial customers wishing to evaluate the various MID technologies on their own products. As most of the industrial customers are not yet familiar with these new technologies, the qualification of the new MID products is a long process. As a consequence, for the time being, opportunities for building blocks transfer into industrial production plants did not appear yet. This transfer will be only possible once the technologies have been fully validated by the industrial customers, and the market big enough to justify the integration of the manufacturing building blocks in their own production plants.

3.7 Work Package 7: Online process and quality control
The main objectives of work package 7 are:
• To provide an advanced software platform for engineers to develop MID products.
• To provide a relevant process and product quality inspection strategy for MID products.
• To provide a non-destructive 3D metrology tool enabling feedback on production process / quality.
Software platform
Development of MID usually faces some “cross concerns” difficulties because different fields of expertise (e.g. injection molding, metal patterning, assembly) are simultaneously involved when a new product/process is designed. The workbench software is a client-server application designed to help different actors to collaborate efficiently. Based on OBEO™ technology it offers for each “viewpoint” a specific interface suited to his need. The software implements a knowledge base to store “know-how” and best practices coming from experience. This base is not only configurable but also extensible. New rules can be specified as experience grows.
The main goal of the workbench software is to provide a tool that will help developers to specify the product, develop the best manufacturing technologies, compute and compare the manufacturing costs, and make the best choices using the knowledge base.
An MID model was developed by PEP, including processes, equipment, specifications and design rules. Regarding the design rules, some product properties were utilized to handle the technology selection, e.g. tracks dimensions, part dimensions, vias, circuit shape, etc. Two manufacturing routes were identified to manufacture MID products: LDS and two-shot molding. For each route the software offers graphical tools to specify the workflow through diagrams (Figure 3 45).
The 3D-HiPMAS workbench development led to the full implementation of the following functionalities:
• Dashboard view: to follow the activity stream of the project, open and edit data
• Knowledge base editor: to edit materials, equipment, personnel, costs, processes and design rules
• Requirements editor: to edit requirements and rate the design concepts
• Bill of material editor: to specify the products by components
• Process advisor view: to find the best process for the product to be manufactured
• Flow chart editor: to graphical graphically edit the processes
• Purchasing view: to identify the products to supply and display investment costs
• MID processes cost calculator: to evaluate the cost of the MID processes
• Validation rules report: to check the data consistency
The HAHN-SCHICKARD MID cost model was implemented in the workbench, as well as the validation rules previously defined in close collaboration with HAHN-SCHICKARD. At the end of the project the workbench has reached a pre-industrial maturity.

Figure 3 45: Process flow chart
Process and product quality control
Regarding the quality inspection system it can be divided in two main categories: product quality specifications and process control specifications.
The product quality needs the definition of critical criteria for each manufacturing step. It will help to define intermediate and final tests to avoid scraps on the final control. Different categories of product quality are classically used in MID manufacturing: geometric dimensioning and tolerancing, morphological injection defects, metallization defects, SMD assembly. All these critical criteria have to be defined in the consortium between demonstrator providers and manufacturing partners.
The process control is also an important way to produce MID with high level of quality. Each manufacturing step has more or less relevant process parameters that could be controlled during the cycle. It has to be defined which parameters could be controlled for each process and product, and it has to be checked the influence of each parameter on critical criteria.
An offline process control system for fabrication of MID was implemented by PEP in the pilot line which included:
• Identification of the most influent operating parameters for MID quality.
• Establishment of a model governing the relationships between the parameters and the quality criteria.
This work was done through statistical analysis of experimental tests conducted at HAHN-SCHICKARD using an existing MID and fully dedicated to tests. At the end the main result was a predictive model able to predict layer thickness, layer resistance, track width and edge roughness for LCP substrate material. When other substrate materials are used this approach can be applied and easily adapted. The developed method is valid for any MID product.
X-ray inspection tool
In the first stages of the project PSL carried out various technology surveys and investigations with the aim of identifying the most appropriate technologies and techniques to achieve the above objectives. The main system components that were researched and tested were as follows:
X-ray source: For micron scale inspection of small MID components that provide a relatively low degree of X-ray attenuation, a small spot size X-ray source is required and very high power output is not necessary. A “microfocus” source with spot size less than 10 microns would provide highest resolution. A range of sources were reviewed and tested, and units from Thermo Kevex selected for the project.
X-ray cameras: The important performance criteria for an X-ray camera are resolution, noise, sensitivity, and signal to noise ratio / dynamic range. A survey of the expected ratio between component size and feature or defect sizes for the MID demonstrator samples showed that a 2k x 2k resolution detector would be appropriate for the project. The new SCMOS sensor technology provides state of the art noise levels and dynamic range and was therefore selected for the development of an X-ray camera design for the 3D-HiPMAS project. High efficiency fibre optic coupling between the sensor and an optimised scintillator would ensure high sensitivity for the X-ray detector.
X-ray cabinet: A study was carried out to identify the optimum X-ray cabinet construction given the expected X-ray flux and energy levels expected to be used. It concluded that an enclosure constructed from approximately 1mm thick lead is the most effective and the lightest way of achieving full X-ray safety to international standards. Sandwiching the lead between MDF facings supports and protects the lead, and allows the resulting composite to be treated like ordinary sheet material. Early in the project it was decided in conjunction with HAHN-SCHICKARD that samples to be X-ray inspected would be manually placed in the cabinet in for X-ray inspection. The cabinet would thus be a standalone item requiring a door that can be opened manually by the user, as opposed to being an enclosure built around an existing component conveyor, requiring dual shielded entrance and exit doors for the samples.
Sample manipulators: At the conception of the project it was expected that the X-ray camera and source would be mounted on robot arms, to be arbitrarily positioned around the MID component to allow multiple X-ray views of the items to be acquired. However, a study carried out into the candidate technologies for the camera/source/sample support mechanics showed that linear and rotational stages give much higher positional accuracy and repeatability than large robot arms, especially when the arms are carrying several-kilo loads such as X-ray sources. This positional accuracy is important when small samples are to be imaged at micrometer scale resolution. In addition, the mounting of the sample on a precision rotation stage allows computed tomography (CT) routines to be employed to create full 3D reconstructions of the sample.
Software: The high degree of automation required of the whole X-ray imaging and defect detection process required that all controllable system components (sources, cameras, stages) be interfaced to a PC to provide coordination and control. To simplify the interface to the user, it was decided to design the software architecture in such a way that all of the various software controls are integrated as plug-in modules into a single application that provides a simple graphical user interface to the operator. Furthermore, it was decided to develop a macro or scripting language, to allow the functions available in the high level application to be automated via a pre-prepared text-based script. This would allow the whole inspection process for a component to be initiated by a single software command or mouse click.
Early discussions with HAHN-SCHICKARD revealed that the primary need for the X-ray inspection machine is in fast throughput inspection, typically concentrating on a few key areas in each component where known common defects could occur or critical features are located. While full 3D reconstruction of an item via computed tomography is valuable as a research and development tool, it is too slow and insufficiently targeted as a routine production line operation. It was therefore decided that the 3D-HiPMAS inspection machine should provide CT as planned, and CT reconstruction and visualisation routines would be developed and included as software modules, but that as its primary functionality it would also provide the facility for fast acquisition of multiple, arbitrary, targeted 2D views of the sample.
This latter requirement resulted in the 3D-HiPMAS system being designed to include two independent X-ray inspection stations within the same cabinet. One inspection station is designed to operate at 1:1 magnification, the other with variable magnification. When combined with linear and rotation stages that can position the sample in a wide range of orientations in front of each station, the ability is created to acquire a complex set of detailed views of a sample in a short cycle time. A fast linear stage moves the sample from one station to the other, inside the cabinet. This stage in fact mimics the action of a component conveyor in a production line setting, moving the samples from one station to another. In such a configuration the operation of the two inspection stations could be in parallel, to further reduce inspection times.
Much hardware and software development was required to meet the project aims. The main development work carried out has been as follows:
X-ray source controller: The higher-power, minifocus source in inspection station 1 does not include any form of controller, and so a control unit was developed to allow the X-ray voltage and current to be set, and to be integrated with the cabinet safety interlocks and X-ray beacon. The unit was also designed to include a PC interface, to allow the top level user application to enable and disable the source via software.
X-ray cabinet: A large cabinet was designed to accommodate the two inspection stations. X-ray testing was carried out to ensure compliance with European safety standards. A mains distribution unit was designed and integrated into the supporting bench, together with an emergency stop switch.
X-ray cameras: A complete new camera design was developed to drive the new SCMOS 2k x 2k sensors. This included electronic hardware and firmware design, together with mechanical design of the camera housings and software development of the DLLs that interface the unit to the PC. To provide X-ray sensitivity with high efficiency the SCMOS sensor has to be coupled to an X-ray scintillator through a technique that involves bonding a coherent fibre optic bundle to the sensor surface. Unfortunately this bonding process proved to be of very low yield, and resulted in unreliability: sensors would stop functioning hours or days after an apparently successful bonding operation.
Fortunately within the project as a backup for the new-technology SCMOS PSL had also been developing a camera around a newly introduced alternative sensor from Sony, which can provide higher resolution than the SCMOS but with slightly lower signal to noise ratio for low amplitude signals. We therefore switched the 3D-HiPMAS camera designs to this alternative sensor. Ironically, this sensor also proved difficult to bond to fibre optics, but for a different reason, the difficulty of removing its covering window without damaging the sensor. With a new technique we have solved this problem however, which allowed the cameras for the project to be built.
Software: An end user application has been developed that integrates the two X-ray cameras, the two X-ray sources, and the manipulation stages that move the sample. In turn this has required the development of low-level driver DLLs that interface the various system components to the PC. In the application the user can manually select camera exposure, X-ray power settings, and sample position and magnification and then view the resulting live X-ray images directly within the application. Image enhancement routines have been included, to provide an optimised X-ray image free of real-world hardware artefacts such as shading, geometric distortion, and scintillator non-uniformity. A new technique has been developed to optimise image quality when imaging through absorbing materials such as MID substrates.
Routines have been written that acquire a sequence of images of a component and perform a CT reconstruction to produce a full 3D model, which can be viewed via a reconstruction module. This allows, for example, a sliced view of a component to be generated or internal volumes of the sample to be visualised.
Defect detection routines have been devised and coded to identify breaks in tracks, substrate non-uniformities, etc. These routines compare the image of the components with a perfect reference image: to accommodate tolerances in the sample holders a software registration technique has been developed to allow pixel-accurate image comparisons. As part of the defect detection facility, routines have been included that can measure the size of image features, for example track widths, and report the measurement data on the screen and via a text file. To provide extremely high resolution images an image stitching technique has been developed that seamlessly combines images acquired as the sample is translated by the linear stages, to provide both huge imaging area and very fine resolution. Finally, a scripting facility allows the whole inspection process, from placement of component in the X-ray cabinet to receipt of results and coordinates of any defects, to be fully automated and initiated by a single button click.
Modelling: A study was carried out to model the X-ray imaging process, in order to optimise the camera and source characteristics for the 3D-HiPMAS system. This resulted in a set of equations that could be used to predict the sensitivity, resolution, and signal to noise ratio of an X-ray imaging system as a function of its system components and operating settings. On the basis of this study the optimum type and thickness of the X-ray scintillators for the two 3D-HiPMAS cameras were calculated, and the expected resolution predicted.
After the various components were developed the complete 3D-HiPMAS system was assembled and tested prior to shipping to HAHN-SCHICKARD. Performance of the two inspection stations was found to meet or exceed expectations. Key parameters of note include the following:
Sensitivity - typically an exposure time of no more than 1 to 2 seconds is required to acquire an X-ray image of a MID component suitable for defect detection.
Resolution - the 1:1 magnification system provides a resolution at the sample of 20 microns, with a fixed field of view of 12 mm diagonal. The variable magnification system provides a highest sample resolution of 6 microns, with a field of view of 3mm. For large samples, at the low magnification setting it has a resolution of 38 microns, with a field of view of 45 mm.
Defect detection – the routines developed can successfully identify a range of defect types, from breaks or short circuits in tracks to variations in substrate density. HAHN-SCHCKARD samples were used for testing this facility at PSL, by synthetically introducing defects of a range of sizes and densities into a sample X-ray image, and allowing the software facility to find them. This technique demonstrated that defects down to a few pixels in size can be detected, with the limiting size being determined by the contrast of the defect in the X-ray image. Typically, for any particular sample type and imaging conditions, it is necessary to adjust the thresholds the software uses to discriminate between a defect and natural variation in the material. These thresholds are set manually or in the scripting macro, and will then apply for all subsequent inspections of this sample view. When defects are present very close to a sharp intensity edge in the image, typically corresponding to a silhouette edge of the sample or transition between material types, the defect may not always be detected if of low contrast. Selecting a different pose of the sample, to move the defect location away from the obscuring edge, eliminates this effect.

Potential Impact:
4.1 Potential Impact of Results

4.1.1 Work Package 1: Technical specifications and design concepts
Until now there is no reference for using MID technology for fuel cell applications. The main advantage of a MID based design concept is to reduce size and cost. An MID based design concept enables integration of electrical, mechanical and thermal functions in hearing aids with regard to miniaturization aspects. For the micro switch MID technology permits to improve the actual performances, i.e. RF performance up to higher frequency (12 GHz) and mechanical performance, and also to reduce size and cost compared to competitors. An MID based pressure sensor integrated in a quick connector enables added value to the plastic by integrating fastening and measurement functions and therefore high potential for simplification of the assembly and reduction of cost.

4.1.2 Work Package 2: 3D system carrier
For the state of the art plastic materials the MID technology was limited with respect to realization of fine metal line pitches. By using the new LDS thermoplastic materials developed in 3D-HiPMAS MID technology can enter new applications, especially in the field of miniaturization and highly integrated electronic systems. Due to the optimization of thermal expansion of the new LDS materials there is also the possibility to realize applications with high requirements concerning reliability of electrical functions, for example in automotive industry.
Additionally the new LDS materials with enhanced thermal conductivity will allow the usage of MID technology for applications where thermal management plays an important role. In addition to the electrical function of the MID carrier, the new materials can act as heat sinks, for example in lighting applications or in high power electronics.
The 2-shot molding process developed within 3D-HiPMAS enables manufacturing of MID parts with small features, e.g. pitches below 0.4 mm. The injection process was optimized in parallel with the metallization process in order to achieve the targeted dimensions. This result paves the way for manufacturing of new MID products with large production volumes. Indeed, 2-shot moulding is well suited for very large volume applications.

4.1.3 Work Package 3: 3D metal patterning
LDS technology has in the past helped to drastically reduce the size of mobile phones, because it is widely used for the generation of antennas directly on the phone's body. However, these antennas are on the lower end of complexity and functionality. With the development of the ultra-fine pitch laser system and the corresponding laser, cleaning and electroless plating processes, 3D-HiPMAS enables new applications for the LDS technology, with a stronger focus on highly integrated components. Up to this day, the market for MID has remained small due to high costs and low reliability, but 3D-HiPMAS developments will help to soften the sharp edges of these issues.
The metal plating processes developed in 3D-HiPMAS enlarge the portfolio of available metal surface finishes for MID. Thereby new applications e.g. in medical technology are accessible by using Cu/Pd/Au metal lines. Cu/Ag enables the realization of MID components at lower cost because less chemicals and noble metals are needed compared to the state-of-the-art Cu/Ni/Au.
MID potentially allow highly complex components combining electronic and mechanical functions in a small volume. The main goal is the ability to integrate such functions into everyday items and thus improve the quality of daily life. The trend toward miniaturization is fastest in electronics, and the results achieved in this work package, like the new laser system technology and the improved process chain will help to address the requirements of next generation MID.

4.1.4 Work Package 4: 3D high precision assembling
Due to the new 3D assembly machine HAECKER has the opportunity to offer customers a new highly efficient machine for mass production. HAECKER expects additional business growth in the future. Additional turnover of 5-10 M€ could be achieved with the machine per year in the next 5 years. That would mean the number of employees will increase in the near future. Already at the end of the 3D-HiPMAS project HAECKER increased the number of employees by five people in the production department to overcome the workload.
The joining processes developed in 3D-HiPMAS will allow new applications, e.g. micro optical devices where high accuracy is needed. Further miniaturization of MID components from different branches can be achieved by using smallest SMD and fine pitch bare dies.

4.1.5 Work Package 5: Flexible 3D high precision MID Platform
In 3D-HiPMAS a pilot line at HAHN-SCHICKARD in Stuttgart for fabricating high precision 3D MID based micro assemblies was set up by implementing of the newly developed technological building blocks. As 3D-HiPMAS technology is an enabling technology for developing a variety of new innovative products different branches can be addressed. The pilot line is ready to offer services for development as well as production of prototypes and small series especially for SME in Europe. The pilot line enables broad dissemination of the technology for realisation of new miniaturized and highly integrated components at low production cost. Furthermore the customers are able to access the know-how of different partners at different locations. Know-how transfer to institutions and industrial companies is enabled by platform building block deployment in Europe.
The 3D-HiPMAS building blocks implemented in the pilot line which address miniaturization aspects in next generation MID enable also a significant reduction of emissions, energy and material consumption compared to state-of-the-art technology.

4.1.6 Work Package 6: Demonstration
3D-HiPMAS enabled RAYCE to design a capacitive pressure sensor integrated in their Quick Connector from the beginning to the proof of concept (demonstrator). The MID based capacitive pressure sensor answers to the initial functional and economic specifications. The characterization results are very promising for future product development. A first rough cost estimation for the MID based capacitive pressure sensor for a small annual volume (10000 pieces/year) including components and process costs for MID carrier amounts to approx. 6.50 € in total.
Furthermore the feasibility to use an MID based strain gauge for composite monitoring could be validated. The fine pitch of 70 µm developed in 3D-HiPMAS allowed to reduce the strain gauge size by a factor of 2. Also, the fine pitch device offered better resolution. The characterization results of the MID based strain gauge showed good performance correlation between a standard strain gauge and the new MID based strain gauge enabling new solutions.
The new MID process offers to PRAGMA products a new level of performance. The integration of electronic functions directly into the fuel cell core permits a better accuracy of sensors and to increase drastically feedback experience by introducing a data log file and a unique identification tag. MID technology reduces the number of assembly operations and power consumption during production stage that has a positive effect on environmental impact. Due to low production volume, the cost of this technology is roughly three times the cost of standard PCB. However, the 3D shape on MID part allows an obviously better integration level.
SONOVA aims to be the most respected hearing care company in the world and, as such, has a social as well as a business goal: to help people with hearing impairment by creating innovative, high-quality, safe products that meet people’s needs while adding social value and reducing environmental impact. SONOVA´s products are by their very nature subject to ever higher demand for miniaturization and increased functionality. LDS MID enable SONOVA to develop components for their products that integrate electrical, mechanical and thermal functions in one contribution for miniaturization and reducing environmental impact. The demonstrator realized in 3D-HiPMAS is an example how further integration of structural, mechanical and electrical functionalities can potentially be realized by MID technology.
For the micro switch from RADIALL MID technology permits to improve the actual performances, i.e. RF performance up to higher frequency and mechanical performance (life time), and also to reduce size compared to competitors. MID technology enables reducing the number of parts and facilitates the assembling process. The new micro switch will allow RADIALL to enter a new market range (telecommunication) because of better RF performances.
The characterization of the pilot line at HAHN-SCHICKARD using the developed demonstrators shows the applicability of the pilot line for offering services for development as well as production of prototypes and small series. Guidelines facilitate the usage of the pilot line by interested customers.
The set-up of the 3D-HiPMAS daughter platform in PEP enables the spreading of 3D-HiPMAS technologies among potential industrial customers. This platform gives them an easy access to the new technologies and allows them to evaluate these technologies on their own MID products. The start-up S2P was created by PEP in order to increase the national and European visibility of the daughter platform.

4.1.7 Work Package 7: Online process and quality control
The workbench created by PEP within 3D-HiPMAS is an effective tool, enabling the optimization of technical choices within the development of new MID products. This tool is meant to ease the collaboration between several processes or technical domains. It leads to an effective time-to-market reduction for new developments. The workbench has mainly two levels of impact. Internally, i.e. at the level of the pilot lines, the workbench will be applied for future developments of new MID products. The databases of the workbench will be filled with inputs from previous and future developments. Externally, the workbench can be efficiently applied in industrial customers’ offices and plants in order to improve their cost-effectiveness. This requires a preliminary adjustment of the tool to specific applications or processes.
The development work carried out by PSL in creating the 3D-HiPMAS X-ray inspection system has resulted in an enlargement of the product range PSL can offer to their customers, together with an increase in their capabilities. In particular, the SCMOS 2k x 2k camera which was designed within this project has proved to be successful in a number of applications. Many of these were initially optical imaging applications, where it was not necessary to bond the sensor to a fibre optic, a process found to be unreliable. However, with further development of this bonding process PSL has successfully made a number of X-ray cameras based around this sensor. This has benefitted a number of research institutions around the world, who are now using such detectors at synchrotrons and neutron sources for diffraction and crystallography applications.
The development and integration of both X-ray controllers and sample positioning stages into the same application that interfaces with the X-ray detector has also opened up further opportunities for PSL. For example, PSL has been able to manufacture a solar cell inspection system that incorporates an X-ray source and X-ray diffraction camera, and includes linear stages to scan the solar cell through the X-ray beam, to acquire via analysis of the diffraction pattern a map of the individual crystal grain orientations within the solar cell wafer. This is currently benefitting both European and Far Eastern solar cell manufacturers.
3D-HiPMAS has helped to keep Photonic Science, a UK-based SME, at the forefront of X-ray detector development, and has helped to introduce a system-level capability in the company’s portfolio.

4.2 Exploitation of Results
During the 3D-HiPMAS project, CEA investigated several techniques for characterization polymers developed and components. Characterization (microstructure, thermal and mechanical properties) results are available for scientific publication distribution with other partners of the project. Some techniques developed at the end of project, e.g. Cu circuit on polymers by screen printing, should be improved and made reliable through other projects. To date, no work part led by CEA will be patented for a licensing exploitation.

In 3D-HiPMAS ENSINGER has developed 4 new LDS materials. These materials will be a part of the product portfolio of ENSINGER. The materials as well as the overall results of the project will be presented to potential customers for 3D micro parts. Market development for the LDS materials of ENSINGER will focus on applications in automotive, medical and electronics industry. There are already about 20 interested parties for the new LDS materials. ENSINGER will also continue to work on customized LDS materials based on the project results to expand the usage of MID technology in Europe further.

HAECKER has a good standing in the 3D MID community and as a 3D assembly expert also before the 3D-HiPMAS project. The strength is the high flexible assembly platform which can be modified by HAECKER or the customer within short time to realize new products. The main challenge was to overcome the high assembly costs due to lower cycle time.
During 3D-HiPMAS HAECKER found out that the assembly speed is mainly driven by processing time such as dispensing of the solder paste, pick and place or soldering. To increase the speed of the axis would not gain significant benefit. In 3D-HiPMAS HAECKER developed a machine which can do two process steps in one time and increase the speed of the axis portal system. The processing time is at least two times faster than before the project. The machine is the solution for mass production needs in 3D assembly and is offered for all customers as a new possibility to get more output on small footprint at the production floor.

HAHN-SCHICKARD is a leading edge development partner in MID technology and will operate the pilot line with the new building blocks for offering prototyping and fabrication services of small series especially for SME in Europe. In addition to the participation to collaborative research projects, HAHN-SCHICKARD also provides development services to industrial partners whereby transfer of knowledge and / or know-how to industry is enabled. The new process developments in 3D-HiPMAS in metal plating and joining technologies enable the generation of new applications for different branches.

LPKF will continue to develop the ultra-fine pitch PU toward a commercial product. However, until the end of 3D-HiPMAS, no customers could be acquired yet, mainly due to little commercial need for ultra-fine pitch metal structures. The main selling points of LDS in the past have been antennas for mobile phones directly integrated into the body. Due to the switch to metal bodies, LDS antennas are currently more and more replaced by flexible printed circuit boards. While LDS is highly relevant for MID in general, the market for MID applications is still very small. LPKF is now working on new applications for LDS, also with a focus on smaller structures, lower costs and higher productivity.

PEP has obtained several exploitable results from its tasks within 3D-HiPMAS. These results mainly deal with the manufacturing of 3D MID parts with fine pitches using 2-shot molding process, the development of the workbench for process and quality management, and the setting-up of the daughter platform.
PEP has several ways to exploit these results. As a private technical center, PEP’s activities are mostly oriented towards collaborative research programs. On the basis of 3D-HiPMAS results, PEP has already started to look for new opportunities of R&D projects related to the 3D MID technologies. In addition to the participation to collaborative research projects, PEP also provides services to industrial partners. In this case, the exploitation of 3D-HiPMAS results is performed via direct services, and transfer of knowledge and / or know-how to industry.
One of the main achievements for PEP within the 3D-HiPMAS project in terms of exploitation of results is the creation of the start-up S2P (Smart Plastic Products). The creation of this start-up gives more visibility to the 3D-HiPMAS daughter platform at national and European levels. S2P aims at providing in France the full process flow of a “Smart Plastic Product”, providing solutions for designing, manufacturing, qualification and technology transfer of the whole value chain of a product development: technological feasibility/proof of concept, prototyping, pre-series and industrialization. S2P also provide training services on 3D MID technologies.

The main objective for SONOVA to join 3D-HiPMAS was an assessment of the capabilities and limitations of the 3D MID technology by LDS for potential applications in a hearing aid or accessory. The most important aspects were to assess integration of electrical and mechanical components with the goal of complexity/size reduction, alternative metallization strategies with the promise of better environmental reliability and assembly of SMD components on 3D substrates. During the ideation phase of the hearing aid demonstrator several new concepts for MID based hearing aid architecture were found, which led to a published IP filing (WO 2015139749 A1) although it was deemed too risky for realization as demonstrator in the scope of the project.
In view of trends moving to 2.4 GHz radio technology which allows direct streaming from Bluetooth enabled devices to hearing instruments, the complexity and integrated functionality of the instrument increases. LDS MID can play an important role in achieving this.

PLASTIPOLIS is the French competitiveness cluster of the plastic industry. PLASTIPOLIS is a non-profitable organization. The PLASTIPOLIS exploitable results are different from the others. The services that PLASTIPOLIS offers to his members are based on four main pillars: network, innovation, technology watch and business. PLASTIPOLIS organized the 3D-HiPMAS contest which was a totally new concept. PLASTIPOLIS has now a set of best practices. This know-how could be transferred in other innovation projects. PLASTIPOLIS has also extended his network in the field of MID. Thanks to the project PLASTIPOLIS has gained new knowledge in the field of MID. The cluster will be able to better support his current and future members in the setting-up of innovations projects on MID. Moreover, PLASTIPOLIS will be more efficient and relevant to perform technology watch on MID.

PRAGMA has joined 3D-HiPMAS in a constant process of innovation research. This project showed the advantage of MID technology to increase integration and reliability of their products and reduce production time and environmental impact. Indeed, the new fuel cell interconnection needs now only a unique cable instead of four cables by the past. The integration of sensors into the fuel cell core increases the reliability and the speed of measurements and reduces external component need. An embedded memory module allows to trace all events happened in this fuel cell and constitute a precious data base for experience feedback. Also, the use of this innovative technology into our innovative product consolidates the leadership of PRAGMA on low power PEM fuel cell market.
Long term test will be performed on demonstrators to evaluate life time and a cost assessment for serial production is being studied. A view on this project will be integrated in the next corporate website update as an advantage to push our fuel cell technology on the market.

As an SME, PSL’s exploitation activities have primarily been in promoting the 3D-HiPMAS system capabilities to potential customers. Our website contains details of the new camera products we are offering, as well as our capabilities in being able to offer complete turnkey systems including X-ray sources and sample stages. Our sales staff are regularly quoting and offering both cameras and systems to potential customers.
Several systems have been produced in the last year that could not have been offered before we undertook the 3D-HiPMAS developments. For example, we have supplied two systems to a European R and D centre for both 2D and 3D X-ray imaging. The 3D system uses the CT routines developed in 3D-HiPMAS for reconstructing and visualising the samples. In a further example, we have manufactured systems for a medical application that stitches together a 2D array of X-ray images, acquired as the sample is scanned automatically by two linear stages similar to the 3D-HiPMAS geometry. This is providing enormous images over 30k x 20k in resolution, at micron resolution, of thin medical samples. Publicity and marketing of our capabilities in these new application areas also represents exploitation of the capabilities acquired in the 3D-HiPMAS project.

RADIALL has patented the new concept of the micro switch (FR 1454676) and extended to other countries. The new concept can increase the market share of RADIALL. The final product will be on the market between one to three years after the end of the 3D-HiPMAS project.

3D-HiPMAS was for RAYCE an opportunity to realize innovations on real market demand. In fact there are more and more sensors in automotive. On the market there is a demand of integration and improved measurement performance. The results in 3D-HiPMAS address directly this need. At RAYCE the concepts developed in 3D-HiPMAS were presented internally to the management. The feedback was very positive and the MID based capacitive pressure sensor is in accordance with the market needs, as also a direct feedback from a customer showed. As MID technology is an innovative and new technology, RAYCE is further working on:
• Process constraints
• Serial product cost estimation
• Quality and risks linked to MID

List of Websites:
www.3d-hipmas.eu

Contact: Dr. Wolfgang Eberhardt
Address: Hahn-Schickard, Allmandring 9 b, 70569 Stuttgart, Germany
Tel: +49 711 68583717
Fax: +49 711 68583705
E-mail: Wolfgang.Eberhardt@Hahn-Schickard.de