| Actually, solder paste adds about 12% to the joint volume for PBGAs, or about 31% for MicroBGAs -- assuming standard (recommended) pad sizes and stencil thicknesses, and paste with 90% metal content (50% metal by volume).
Michael,
In the "real world" I agree. In my current world it is as I said and the solder joints are acceptable with less than "outside world" solder volume.
I still don't know reliability here. I do know some of it outside and it's getting better.
Thanks,
Earl Moon
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| | | I'd like to find some technical papers on the reliability of reworked BGAs. If you know of any, please let me know. | | | | | | I have a concern about this because our current rework process does not apply solder paste to the pads prior to placing the part; this results in a lower standoff and reduced fatigue life...but reduced how much?. | | | | | The humungous company for whom I am now working has had the wisdom and foresite to allow me to support manufacturing efforts in various areas. Wonderful as this sounds to me, the one area I am working, and am most interested, is repair/rework - especially BGA and beyond. We employ the SRT 1000 to do this. | | | | As Steve said, we and many like us, do not apply solder paste as this adds about less than 7% to the solder joint volume and provides a mechanism for other problems not associated with normal reflow operations. Eutectic balls are used. You know, the standard stuff my balls are made of (63/37). Sometimes during reflow, high temp balls are positioned at the corners to prevent collapse and on it goes. | | | | Oh yes, about reliability, all I can say is initial quality is very well established during X-Ray, but these guys won't let me near their long term reliability stuff. I can only guess, but I guess pretty well after running so many rework cycles. | | | | Earl Moon | | | | | |
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