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The BEST BGA Technical Symposium, held August 21 at Arlington Heights in Illinois, was a success, according Bob Wettermann, MIT. This year’s topic focused on on one of the greatest package problem areas: Ball grid arrays (BGAs).
The conference began with Wetterman challenging the participants to make the attainment of knowledge the “15-mile march” of their careers. “Like Roald Amundsen, we all need to have discipline to reach our goals,” he said. One of those disciplines is making sure that one's knowledge quiver is continually loaded with better and better arrows.
The symposium featured Shea Engineering’s Chrys Shea, who presented “Better Yields of BGAs through SPI." One takeaway was that electronic assemblers should be sure to check stencils at incoming inspection. Shea suggested a few simple print tests and solder paste volume checking with SPI to see if volume percentages are within range.
Kyzen’s Mike Bixenman, the “Cleaningologist,” presented "Cleaning Underneath BGAs," providing very practical suggestions on getting underneath low standoff parts. Bixenman suggested going to non-solder mask defined pads underneath BGAs and increasing the standoff height underneath LGAs by “bumping.” He also explained clearly what it takes to clean underneath parts--it’s a combination of creating the “channel” for cleaning and having enough energy in the cleaning system to break the “dam” underneath parts, making sure the parts were exposed for the proper time to the cleaning agent.
Don Naugler from VJElektronix presented "X-Ray Inspection of BGAs," walking participants through basic X-ray principal building up to “3D X-ray” systems, explaining what they can and cannot do. He also recommended that engineers consider CT X-ray for diagnostics and troubleshooting soldering and assembly problems.
Mario Salzo, a black belt from Indium, presented "Pad Cratering and Graping," discussing the graping and head-in-pillow phenomenon.
Finally, Dale Lee of Plexus discussed DFM and BGAs. He noted that the pitch of modern devices is now on the order of magnitude of the weave of the PCB laminate and, as such, assemblers have to make sure stencils matched the artwork, and that they should know how to do the routing of BGAs from the IO, and how to get around the via dilemma, among others.
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