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FP6

MICROSCAN Résumé de rapport

Project ID: 508613
Financé au titre de: FP6-SME
Pays: United Kingdom

Final Report Summary - MICROSCAN (Development of comprehensive in-line quality control system for printed circuit board assemblies)

The aim of the MICROSCAN project was to produce a powerful tool in the total quality control of printed circuit board (PCB) assemblies. This was to be achieved by combining inspection techniques not normally used in an in-line environment.
Through the development of four prototypes, the principle of using advance automated imaging (AOI), X-ray, thermography and acoustic inspection, together and in-line, had been developed and a successful proof in principle had been demonstrated.

From the start of the project, it was expected that the space and cost savings obtained by combining all of the technologies in one comprehensive machine, could be outweighed by the compromises the combination would bring to the performance of each separate inspection technology. For example, when all the inspection prototypes are used together a compromise may have to be made with inspection throughput as X-ray inspection is slower than AOI. In addition using a combined system may not always be convenient and depending on the manufacturing process some stages in the PCB manufacturing line may only necessitate a specific inspection process. These compromising factors depend to an extent on the given PCB configuration that is to be inspected and may or may not pose an issue to the PCB manufacturer.

By good cooperation between the partners developing the prototypes, each of the prototypes had been designed around a common electrical, mechanical and software communications infrastructure. This allows the inspection modules to be used separately, together, interchanged or in different stages of the PCB manufacturing process to give the best results in terms of inspection coverage and inspection throughput. In this way a highly flexible system had been developed.

The strategic objectives of this project were:
1. to overcome current problems encountered in PCB inspection by developing four non-destructive testing (NDT) inspection systems;
2. combine the developed systems within a PCB assembly system to produce new innovative in-line inspection techniques, which will provide full quality control of the PCB assembly process.

These were realised by the achievement of the following technical objectives:
- development of an X-ray system for the real-time identification and quantification of defects in PCBs;
- development of acoustic systems for potential in-line inspection of PCBs;
- improvement of automated optical inspection (AOI) systems and data recognition;
- development of thermal/infrared systems for potential in-line inspection of PCBs;
- provision of feedback mechanisms for the real-time control of the PCB assembly process;
- development of features which allow the NDT systems to be complimentarily integrated;
- development of the above systems for use on the new lead-free solder alloys.

In the MICROSCAN project an in-line inspection system comprising four different inspection techniques had been developed and a proof in principle has been demonstrated. This was the first time that this had ever been done. There were a number of achievements in this project that could be considered novel against the state of the art:
- the combination of the inspection techniques offered the capability for 100 % defect coverage;
- the inspection prototypes had been designed in such a way that they could be used either independently or together;
- a generic software framework had been developed that allowed defect detection algorithms to be tested across different inspection techniques including AOI, X-ray and scanning acoustic microscope (SAM);
- it was the first time that a water irrigation probe, used to minimise water contact with the PCB, had been included in an in-line SAM for PCB inspection;
- defect detection algorithms for detection of poor wetting of balls had been implemented; -
the use of leaded tunnels enclosing the entry and exit conveyors of the X-ray inspection module, allowing the X-ray source to be continually on and thereby increasing the maximum inspection throughput.

As far as the impact of the MICROSCAN project on the PCB manufacturing industry is concerned when utilising all four inspection prototypes of the MICROSCAN system it was suited for high-return PCBs, particularly PCBs manufactured for products in medical use and aerospace, rather than high-throughput production work. Nevertheless, depending on the number and type of components present, the total inspection process for a PCB could take approximately a minute.

Already at the start of the project it was expected that the space and cost savings obtained by combining all of the technologies in one comprehensive machine, could be outweighed by the compromises the combination would bring to the performance of each separate inspection technology. For example when all the inspection prototypes were used together a compromise had to be made with respect to inspection throughput. In addition depending on a given stage in the manufacturing process it might not be necessary or convenient to apply all inspection techniques. These compromising factors depend to an extent on the given PCB configuration and complexity that was to be inspected and might or might not pose an issue to the PCB manufacturer.

Since each of the prototypes had been designed around a common electrical, mechanical and software communications infrastructure it enabled the inspection modules to be used separately, together, interchanged or in different stages of the production process to give the best results in terms of inspection coverage and inspection throughput.

Given the ever increasing complexity of PCB assemblies, and the trend to increase the population density of components driving the move to more complex surface mount assembly technology such as BGA and other small foot print devices, there will be increased demands on NDT examination for quality assurance. It is key that two of the inspection prototypes in the system catered for inspection of BGAs.

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Contact

Ian HAIG
Tél.: +44-1442828700
Fax: +44-1442828118
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