PCB007 Magazine

PCB007-Mar2022

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84 PCB007 MAGAZINE I MARCH 2022 Although flying probe testers have become commonplace in today's manufacturing the- atre, one must wonder if the fixture tester, spe- cifically the universal grid or "pin in hole" fix- ture, has any valuable use in the electrical test arena. e advancements in flying probe tech- nology are undisputed with the new abilities to do many of the tests that benchtop testing histori- cally required. Fly- i n g p r o b e t e s t e r s can provide stan- da r d c o n t i n u i t y tests, Hi-Pot, bur- ied passives, induc- tance, impedance, and e ven I R te st ing . Many of these tests his- torically required hard- ware mock-ups to pro- vide the footprint to administer these tests effectively. Of course, the main advantage regarding fly- ing probe testers is the cost. ey provide lower capital investment while providing a large solution platform to many of today's requirements. ere are some who make the argument that flying probe testers remove the necessity of fixture testing altogether. While this may be true to some extent, it is not altogether accurate. It can be argued that some of the earlier universal fixture solu- tions may be obsolete. For example, the earlier 1-inch and 2-inch pin-in-hole fixture solutions cannot provide test solutions for today's com- plex designs. Density issues of modern designs don't allow the use of headed pins. Historically, headed chisel pins were optimal for plated through-hole (PTH) probing, but were a haz- ard when direct-probing surface mount (SMT) pads. Over-compression of the fixture tester to the test fixture could cause damage to the SMT pad, ultimately scrapping the PCB. So, in that example some of the older fixture solutions may be obsolete. However, we had to evolve. Headed chisel pins gave way to fea- tureless music wire technology. ese pins, either crimped or non-crimped, still allowed probing of PTH features while allowing a safer direct probe to SMT pads. ese new pins also allowed direct prob- ing of more complex designs while keeping the fixture to a single pass solution. is was a hindrance in the earlier headed pin designs, as complex designs required multi- ple passes (multiple fixtures) to accomplish the same result. is required extra drilling time and increased cost. Further, the headed chisel pins had a limitation to the size avail- able. e newer featureless pins did not have such a limitation. Unfortunately, the caveat is that more guide plates are required to translate the pin successfully from the probe plate to the universal grid electronics. However, it can be Has Universal Fixture Testing Gone the Way of the Dodo? Testing Todd by Todd Kolmodin, GARDIEN SERVICES USA

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