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102 PCB007 MAGAZINE I FEBRUARY 2022 Given the time it was taking to develop the plated-through process, we had time to debug the soldering process. Fortunately, the Alpha solder and flux actually did the job as adver- tised. Looking back, I think other solders and fluxes could probably have been successful as well. Given the approaching start of produc- tion for the new instruments, however, my priority was to get a process in place, which worked. It took some experimenting to fit it all into our process, but our ability to use a water wash was the key. It also took some time to do the accelerated life testing, but we could see no reliability problem. In addition, we learned how much gold was needed to be an effective etching resist and reduced the gold in the sol- der joint. e result was a basic process used by HP for decades, until surface-mount tech- nology changed everything. e process was eventually mechanized and automated, but the solder and flux remained the same. Another unintended consequence con- cerned the gold plating of the board's con- nector fingers, without a nickel underplate. is required special mating connectors. All this changed when subsequent process engi- neers revisited the process. A nickel under- plate, with a small gold flash, was substituted for thick gold, and HP stopped buying gold in Canada. Standard connectors could be used, and with all of this, they kept the quality look Dave Packard wanted. PCB007 Clyde Coombs is the editor of the Printed Circuits Handbook, which was first published in 1967. The seventh edition, published in 2016, was co-edited by Happy Holden, who, like Clyde, retired from HP after many decades. Trevor Polidore of Rogers Corporation discusses with I-Connect007 guest editor Tara Dunn the introduction of their new materials for 3D printing. They also look at the trends in materials for additive manufacturing. Real Time with... IPC: New Materials and Additive Manufacturing

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