Quality ensured by AOI
01 October 2010
UK-based BAE Systems is a global defense, security, and aerospace company with approximately 107,000 employees worldwide that supports the armed forces with head-up displays for civil and military jets and flight control computers for aeroplane landing and take-off.
All PCBs for electronic equipment are designed and produced at the company’s base in Rochester, Kent, but as the product portfolio of BAE is so wide, it means that about 90 different types of PCBs are manufactured each year. This also places high demands on their product quality, as precision, functional reliability and system stability play a critical role on these products.
BAE Systems runs three production lines, and until 2008, PCB inspection was executed manually in addition to In-Circuit Test and Functional Test.
The test engineers at BAE Systems decided on utilising a system for AOI. In particular, the ability to check solder joints was critical for this decision.
The BAE Systems engineers considered and evaluated a number of systems and finally focussed on four AOI vendors. Even though most systems were similar, the test engineers, after intense evaluations, decided upon an AOI system by GOEPEL electronic.
Robert Driscoll, Test Engineer at BAE Systems says: “It was the best system available.” Apparently, the machine’s advantage was its ease of programming, fast test times, robustness and reliability as well as ‘painless installation’, comments Steve Rodwell, Test Engineering Team Leader of the PCB department.
BAE Systems decided on the stand-alone machine OptiCon BasicLine, because the system had to take the output from all three production lines. After six months when production and complexity increased, the off-line machine’s capacities no longer matched the requirements. “Hundreds of boards a day were simply too much to be tested with the OptiCon BasicLine”, says Driscoll; so the decision was made to opt for another AOI system, but this time with in-line capabilities.
Again, a system from GOEPEL electronic was purchased; an OptiCon AdvancedLine that is employed in the production line of high-volume batches. But the OptiCon BasicLine is still used for SMD inspection and presence of THT components for the other two lines.
Additionally, the stand-alone system is used for test program generation. More than 180 programs have been generated at BAE Systems. Test programming is therefore executed at the offline machine and transferred to the inline system. Furthermore, there’s no time for rewriting programs when system changes occur. Such tasks coupled with program fixing/updating are done with the OptiCon BasicLine offline.
Now, all possible inspection tasks are done with the AOI systems; most importantly device ID checks and polarities (including diodes and capacitors). Historically, about 75% of all defects found by In-Circuit Test and Functional Test were related to SMD faults. These are now captured in real time at the end of the line, with a false-call-rate of less than 1%. The AOI systems clearly identify where the faults are occurring and the defects are stored in a library for traceability. Rodwell states: “Every project or product demands short test processes, and the GOEPEL systems meet them.”
In terms of software, the recently introduced SPC (Statistic Process Control) module is efficiently used to optimise the production process. For example, the BAE Systems engineers needed to know what kinds of faults occur most frequently. After utilising the AOI system they found that it was solder defects, which finally resulted in changes in the manufacturing process.
“As it is, it’s efficient, easy-to-use, user friendly and fast”, states Driscoll. “It exceeded our expectations, and is great to work with,” concludes Rodwell, who adds: “We’re happy with the machine, its reliability and the great support here in the UK.”
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