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Design007-Oct2020

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88 DESIGN007 MAGAZINE I OCTOBER 2020 to the future. Surface mount was and still is a good thing, but those seeking to provide a roadmap for future component termination pitches decided—by fiat—that every future lead pitch would be 80% of the previous one. Thus, 1.25 mm went to 1.0 mm, 0.8 mm, 0.65 mm, and 0.5 mm. While this is completely arbitrary and seemingly harmless, it has had a knock-on effect, which had negative implications that are encountered daily by PCB designers. The myriad component pitches and formats cause uncounted headaches as designers try to inter- connect devices with mixed pitches, land design rules, and redistribution of circuits to get through the maze of wires and termina- tions required to operate. While it was a sad fact of life for peripher- ally leaded SMT components, carrying it over to area array component lead pitches was an even sadder oversight. With area array compo- nents, only a single common base lead pitch was required, and it could be depopulated as needed. However, since area array components followed the same defined roadmap path and progression, we have as many lead pitches for area array as for peripherally leaded devices. At the end of the day, it is completely unneces- sary and even illogical. Today, there are a few hundred-thousand package types and variations. Could it have been course-corrected in the process? Probably not. Business-oriented technologists were too wedded to the 80% rule convention, as defi- cient as it is from a design perspective. Could it still be changed? Perhaps. It remains to be seen whether the allure of the benefits of a standard grid is ever again fully understood and appreciated. There is nothing stopping any package sup- plier from providing IC packages with termina- tions only on a fundamental grid pitch (includ- ing peripherally leaded components, but that takes a bit more care). At the end of the day, it is only a matter of desire and will on the part of the purveyors and the demand from enlight- ened customers. (If interested in digging into this topic, I recommend downloading a copy of Solderless Assembly for Electronics: The SAFE Approach.) The Black Swan: The Impact of the Highly Improbable by Nassim Nicholas Taleb is a good book that should be read by anyone who desires to create a roadmap for an uncertain technological future (many great individuals in history have stated the difficulty associated with prediction, especially about the future). According to Taleb, a black swan is "a highly improbable event with three principal char- acteristics: It is unpredictable, carries a mas- sive impact, and, after the fact, we concoct an explanation that makes it appear less random, and more predictable, than it was." The expe- rience of chip-scale packaging seems to me to fit the description, perhaps the Occam Process idea will as well one day. In the world of roadmapping, black swans are something we should always keep an eye out for; however, they have a way of sneaking in the door from time to time. I can only hope that we will welcome them rather than bar them at the door and hope they will go away. Roadmaps are, after all, about trying to forecast change, not to force or prevent change. FLEX007 Joe Fjelstad is founder and CEO of Verdant Electronics and an interna- tional authority and innovator in the field of electronic interconnection and packaging technologies with more than 185 patents issued or pending. To read past columns or contact Fjelstad, click here. Download your free copy of Fjelstad's book Flexible Circuit Technology, 4 th Edition, and watch Joe's in-depth workshop series, 'Flexible Circuit Technology.' While it was a sad fact of life for peripherally leaded SMT compo- nents, carrying it over to area array component lead pitches was an even sadder oversight.

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