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84 PCB007 MAGAZINE I NOVEMBER 2021 Many years ago, when electrical test (ET) was necessary on a bare printed circuit board (PCB) you would build a dedicated fixture with spring pins and mount the box fixture to a machine interface and perform the test. However, back then there were no precon- figured netlists, and the machines were only capable of "learning" the board. is was known as the "self-learn" or "learn compari- son" test. At the time, all you could do is prove that all the boards of the test lot were the same. e risk was that if there was a film defect and all boards had the same fault, the test would still pass even though all boards were defective. As ET evolved, test machines gained the capability to save learned programs. Although still a "learn," we gained the ability to compare lot to lot for consistency. It wasn't the best The New Electrical Test: Riding the Wave solution but for the day, we worked with what we had. As evolution progressed, the front-end sys- tems began development of ET-related mod- ules that could provide CNC drill files and pro- grams that would support a handful of the test machines available. is was monumental as the self-learn was replaced by predetermined intelligence of the PCB. is raised the confi- dence level of electrical test significantly and unintentional scrap of product due to unde- tectable defects was greatly reduced. Fast forward to today and electrical test, or test and measurement, has made signif- icant advances. No longer self-learning (in most cases), ET now includes a battery of test options. It is not just "opens and shorts" but TDR, IR, buried passives, 4-wire Kelvin, and even buried inductance. Testing Todd by Todd Kolmodin, GARDIEN SERVICES USA

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