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98 PCB007 MAGAZINE I FEBRUARY 2022 Article by Clyde Coombs A story went around Hewlett-Packard in 1961 that when Dave Packard looked inside a newly designed transistorized electronic instrument, he was surprised, even shocked, to see—instead of wires—a motherboard and a row of printed circuit boards. Given a very bad corporate experience with single-sided boards a couple years earlier, printed circuits had a very bad reputation for quality and reliabil- ity, not only at HP, but in electronics generally. However, Dave (as he preferred to be called) realized that the size of the transistor, and the number used in the instrument, required this "new" interconnection technology, and that was alarming. So, he asked if there was any- body in the company who actually knew about printed circuits. at was how I first met Dave Packard. When the "transistor revolution" started in the 1950s, HP was one of the earliest non-con- sumer companies to design products using this new technology. By 1960, all new HP products were being designed this way. One of the early "transistorized" products was a line of elec- tronic "counters" that would become HP's best-selling product for several years. is was the instrument that Packard was inspecting, and the future of the company was suddenly linked to these boards, like it or not. Packard had a right to be concerned. e production problems of using printed circuits in HP products had not been thought out. HP engineers knew how to design these instru- ments, but there was literally no thought given to how to assemble them. We couldn't do the same things in the same way, only smaller. It was clear that we had to do some different things, and some things differently. But which was what? While the extended argument at HP over the construction and fabrication of the board itself played out, there was an equally important and controversial issue of how to solder the assem- bled boards. At the time, the electronics indus- try had a long history of using rosin fluxes to avoid destructive conductive paths created The Origin of HP's Printed Circuit Solder Process