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Our newest columnist takes on the myths of the solder bath.
Wave soldering, or flow soldering (as it was called in its early days), has been around for about 50 years1. Over its lifetime, the once "simple" process has been continuously refined, bringing it to a highly sophisticated practice today. One could easily argue that wave soldering is the most complex of all soldering processes. Now it faces the biggest change in its history: new alloys with different flow behaviors and processing characteristics.
When wave solder alloy conversion issues emerged a few years ago, a number of rumors about the new process began circulating. Some were based on fact, some early speculation, and some just pure fiction. Two years later, with many mainstream assembly processes having converted to Pb-free, it was a surprise to find that many of the Pb-free wave soldering myths still circulated. It's time to set the record straight.
Myth 1 : Pb-free dross sinks to the bottom of the solder pot. Pure fiction. As with SnPb or any metal oxide, dross becomes less dense than is the molten metal and rises to the top. Around the globe, tens of thousands of wave solder operations have been converted to Pb-free alloys, and none has demonstrated dross sinking to the pot bottom. Similar to SnPb, it is typical for some dross to circulate in the melt, and a portion will cling to internal parts of...