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Solderjoint microvoiding is a very hot topic in the industry these days. All the whispering in the hallways has turned into a flurry of technical papers and marketing. What is the low-down on this topic? Microvoids are very small voids which sit just above the intermetallic. They occur very infrequently, but when found, they are most noticeable in fine-pitch, soldermask defined BGA's. When a large number of them sit together at the PCB interface, they can pose a reliability concern. There seems to be a connection to the immersion silver PCB surface finish.
Watch a brief video explaining some of the issues surrounding Microvoids.Some OEM's have been studying them for years, and the industry has seen changes in the silver processes offered by the leading immersion silver contenders. The short story goes like this: aggressive chemistry, made in poorly controlled plating processes, can set up non-uniform silver deposition. If this occurs, "caves" can form in the copper which traps chemicals and/or moisture, leading to voids after soldering.
What's the fix, and where's the proof? Click here to download a comprehensive technical article on this subject.