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High Performance Laser-based Additive Manufacturing

Periodic Reporting for period 2 - HIPERLAM (High Performance Laser-based Additive Manufacturing)

Reporting period: 2018-05-01 to 2020-01-31

The HiperLAM project featured a laser-based additive manufacturing process in two key applications requiring high resolution printed conductive metallic lines: Laser printed RFID antenna, and Laser printed fingerprint biosensor. These two applications have major differences in sizes and production technologies, making the bio-sensor application more challenging than the RF antenna. The demonstrated manufacturing process was based on Laser Induced Forward Transfer (LIFT) of high viscous nanoparticle inks, followed by Selective Laser Sintering (SLS) and Shaping. New materials, tools and process were developed during this project’s timeline. At the end, a fully functional RFID circuit was demonstrated.

While the fingerprint biosensor demonstrated several functional transistors, and not the entire array, the demonstrated processes proved that LIFT-printing and Laser sintering are applicable also for such type of challenging application, especially if the characteristics of laser additive manufacturing are considered during the design of the sensor. The HiperLAM project proved that the suggested method is an attractive option for the industry of organic and large area electronics, as it can process large areas at high printing speeds, while offering high flexibility and compatibility with all substrates.

For more details see the final public report see at Deliverable D7.4.
The HiperLAM 3-year project’s objectives were set to demonstrate superior throughput and lower cost of LIFT-printed, Laser-sintered and Laser-patterned RFID antenna and Fingerprint biosensor, using high viscosity Nano-silver and Nano-copper inks.

The Consortium involved 8 partners. The end users, whose products were selected as case studies, were the UK-based PragmatIC (PRAG) and FlexEnable (FLEX). PRAG produces RFID circuits, and FLEX produces Biosensors. Israel-based PV Nano Cell (PVN) develops NP-inks for the industry, and their high capability of ink adaptation per application was chosen to be used in this project. The NP-ink development was an iterative process, in order to meet the technical and manufacturing requirements of the project. As part of WP3, the Netherland’s Organization for Applied Scientific Research (TNO), and the Israel-based Orbotech (ORBX), developed the process for producing ink donor substrates, the LIFT-printing tools, and the printing processes. TNO concentrated on PRAG’s application (RFID antenna), and ORBX concentrated on FLEX’s application (Fingerprint Biosensor). The Greece-based National Technical University of Athens (NTUA), The School of Applied Mathematical and Physical Sciences, as the owner of WP1, translated the end user’s requirements into technical specifications and developed a costs model and mathematical predictive models for LIFT. In addition, NTUA made significant contributions to the development of inks and to the LIFT and sintering processes. UK-based Oxford Lasers (OX) received printed patterns from both TNO, ORBX and NTUA, and developed the appropriate Selective Laser Sintering and the laser ablation processes for each of the applications. Finally, UK-based MODUS, as part of Dissemination and Exploitation of the project’s outcomes, has developed media and training packages, and was responsible for relevant publications and workshops. The project was administratively and financially coordinated, as well as managed, by Orbotech.

New Silver (Ag) and Copper (Cu) based NP-Inks were specially developed and tailored for the specific applications by PVN during this project. The inks were fully customized during the project for the two specific applications, as well as for all the LIFT-related production processes, assuring a good donor layer quality, jettability and sintering performances. The INK donor layer creation process was also continuously improved, along with the ink development, until stability and reproducibility were reached. Some pinhole formation in the donors was observed and will be mitigated in the future. High speed camera imaging of the jets of ink was used to complement the results of the Finite Elements simulation of non-Newtonian fluid behavior, which was developed during the project.
Advanced lab setups were built by NTUA, TNO, ORBX and OX in order to meet the process requirements, in particular addressing the high speed (> 1m/s) and the high repetition rate (>100kHz) requirements.
LIFT printing process of the 2x2mm2 UHF antennas resulted yields of above 95%. Also the sintering process provided good resistance values and good adhesion with substrate. Since there was no IC that was available to be used with this 2x2mm2 antenna, a new 10x10mm HF antenna was designed specially for the project - and was demonstrated for functionality.
For the fingerprint bisensor, a total of ~8m unprecedented length of <1um thick conductors was needed to be LIFT-printed for each sensor. Since the OTFT gate layer lays on top of already existing layers, both LIFT-printing and Laser shaping needed to be precisely aligned with the underlaying pattern. LIFT printing with <10 defects was achieved. Sintering the 1μm thick lines over the semiconductor pads caused cracks in the conductors, due to sharp 0.7um rises in the end-user application’s surface topology. These cracks dramatically increased the conductors’ resistivity to above the specified levels. Trying to apply a thicker LIFT-printed layer of the conductors solved this issue but caused new challenges during the Laser ablation of the gate’s relief hole, and most of the top pixels were shorted to the gate layer due to spikes at the edges of the holes.despite not being able to obtain a fully functional fingerprint biosensor, individual transistors were found functional. This result proves that LIFT-based techniques are suitable for usage in OTFT production, but that more time is required for these techniques to become more mature for such a delicate application.
LIFT is an attractive emerging technology which is not commercialized yet. The window of opportunity for HiperLAM beneficiaries to go to market with a novel technology capable of superior printing resolution, throughput and lead-time compared to current technologies is still very much alive. The HiperLAM has succeeded demonstrating superior cost and throughput for RFID antenna production, and significantly shorter time-to-market advantage for the fingerprint biosensor. The project’s results can be exploited to achieve significant impact in the target sectors. The achievement of low-cost RFID antenna on-a-chip promises to open up a large consumer-led market not currently accessible by higher cost RFID antenna systems. Similarly the reduction in lead-time by the adoption of a mask-less printing system for Fingerprint sensors would create a significant opportunity in large-scale consumer-driven markets.
A set of LIFT printed on-chip RFID antennas on PragmatIC's substrates.
An array of long thin quality lines printed by LIFT for the fingerprint sensor.