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Flexible Fixturing System for In-Circuit Test
Production Floor |
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Authored By:Rob Jukna, Jabil, Inc. Harry Jin, Checksum TranscriptLarge printed wiring assemblies exceeding 7000 circuit nets create significant quality, cycle time and cost issues at structural test in the new product introduction phase. Traditional in-circuit test and its requirement for expensive "bed of nails" fixtures impose high tooling costs and long cycle times. While flying probers do not require test fixtures, thereby reducing those cost and time impediments, testing large boards impose extremely long test time and lower test coverage. In this paper the authors describe a "flexible fixturing system" which overcomes the cost and tooling cycle times inherent with traditional "bed of nails" fixtures while simultaneously providing the high throughput rates and test coverage of traditional in-circuit testers. SummaryLarge printed wiring assemblies (PWB) exceeding 7000 circuit nets create significant quality, cycle time and cost issues at structural test in the new product introduction (NPI) phase. Traditional in-circuit test and its requirement for expensive bed-of-nails (BoN) fixtures impose high tooling costs and long cycle times. While flying probers (FP) do not require test fixtures, thereby reducing those cost and time impediments, testing large board imposes extremely long test time and lower test coverage. We describe a "Flexible Fixturing System" which overcomes the cost and tooling cycle times inherent with traditional BoN fixtures while simultaneously providing the high throughput rates and test coverage of traditional in-circuit testers. Moreover, this is accomplished at an attractive capital cost. ConclusionsNotwithstanding numerous predictions over the years of its imminent demise, in-circuit bed-of-nails structural test still remains the best means of achieving the "Holy Grail" mix of cost, time and quality than any alternative structural test method for PWBs. We have proved this truism again with the Flexible Fixture System, albeit with several significant changes compared to traditional ICT and traditional custom-wired BoN fixtures. We accomplished this by being able to abandon both traditional wired and wireless fixtures, which have proven inefficient at best an inappropriate at worst in the large board new product release process. We have been able to demonstrate with actual boards in an actual NPI process that the Flexible Fixture System is a fresh approach to the in-circuit paradigm. First, we have achieved the promise of radically reduced fixture costs for the NPI process without the time and coverage shortcomings of flying probers. Second, we have dramatically reduced fixture and test program development and verification cycle time compared to both traditional ICT and flying probers by steering a "third course" between the expense and tooling time of traditional BoN fixtures and the lengthy test times and inadequate test coverage of fixtureless test. Third, we have achieved power-off test coverage equal to - and in some cases - exceeding that of traditional ICT at far lower cost and substantially less fixture development time. So, even as other test organizations try to write yet another obituary for in-circuit test, creative thinking and adroit execution by Jabil and its in-circuit test electronics and software partner has again pushed the boundaries of technical feasibility and compelling economics to enable manufacturer s to again produce and structurally test extremely large and complex PWBs at higher coverage on time and on budget. Initially Published in the IPC Proceedings |
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