| Hello Ya'll, | I've got what may be a silly question, but why does it seem so important to everybody that you have x-ray capability if you're thinking about doing BGA? | I know what most people will tell me; "Steve, that's a pretty silly question, it's because ya' can't see the solder joints ya' big boomerang!" | Is that the only reason? Because if you stop and think about it, we were building boards with hidden solder joints a long time ago on SIMM's (the caps beneath the DRAM's), it never seemed like a big deal back then...and nobody was rushing out to spend $200,000 on a x-ray machine back then either... | So what's the real reason?
I applaud everyone's positive attitude and approach to the inspection issue (these are issues - not problems as I learned at Ford Motors). Design for manufacturing and process instead of results (as defect) management is supposed to preclude the need for inspection. The real world teaches otherwise and will continue to do so until true concurrent engineering is a reality. Having started with BGA many years before the technology was acceptable, I learned what you cannot see will hurt you - unless everyone involved in effective process management works together to prevent such pain. Concurrence means engineering, component, component engineering, design, solder paste, PCB, equipment, and manufacturing people all working together to prevent defect at the design level. Well, as nice as this sounds, it ain't happening all the time. It did not happen when we placed chip caps under memory chips as SIMMS. Voiding was excessive to the point of failure even before shipment. Many memory suppliers scratched their domes trying to correct customer complaints concerning memory failures because they were either DOA or failed shortly after insertion. Part of the problem was solder joint defect due to excessive voiding. We still spec and buy components with excessive solder termination contamination as dirt, grease, oxidation, and other crud preventing solder wetting. Most of us don't even do wetting balance or PCB solder wetting testing. We still have solder paste and other solder medium suppliers practicing we won't tell you because we know it won't hurt you. This is true whether solder wetting problems or those concerning cleanliness are discussed. Just look at this forum and you will see the same questions asked over and over again about solders, solderability, and solder process management. I do not advocate constant, 100% inspections, or purchasing two hundred thousand dollar machines of any sort. Far from it - I do advocate simple, sample level inspections and testing so design and process improvement is assured. This gets back to SPC and what it is supposed to do. Without some type inspection or test, before customer validation, we cannot improve. Inspections, when used with SPC, provide the mechanism for continuous design and manufacturing process improvement. Therefore, quality improves - constantly. In line, gray scale X-Ray inspections are not always necessary. High resolution, black and white X-Ray often provides much clearer evidence of excessive BGA solder joint voiding, though not in "real time." This type inspection can be provided on the "outside" as there are many non- destructive test labs available to render sample level inspection data that can be used for SPC and CPI. In fact, black and white often is superior to any other type. Again, I abhor attempting inspecting quality into anything as we all know it can't be done. We have come too far for that nonsense. However, we must continue inspection on a sample level basis and take ISO 9000 (as a poor example of a complete quality system) to where it should be - continuous process improvement and total process management. Sincerely, Earl Moon - Proof Of Design | -Steve Gregory-
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