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BGA solder joint integrity

Romain

#18651

BGA solder joint integrity | 15 January, 2002

Dear all We have since few weeks problems with BGA solder joint integrity on ENIG finish. Under relatively very flexible of the FR4, the joint breaks between ball and PWB. When we take off the BGA for analysis, some of the pads seem very flat, totaly exempt from solder and the color is "semi-dark grey". the solderability is also very poor.

The gold thickness is ok (~0.25�m). The reflow profile has been checked. Many date code (BGA or PWB)are impacted.

I have hear of the "black-pad" phenomenon. Could it be the problem ? I don't know what is exactly the problem (physico-chemical) and how I can detect it on PCW before assembly. If it's not black-pad phenomenon, what could it be ?

Thanks for your help Romain

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#18652

BGA solder joint integrity | 15 January, 2002

Ah, that�s the problem with ENIG. Isn�t it? You have to solder to nickel, rather than copper. Search the fine SMTnet Archives for background discussion and references on �black pad�.

How can you "detect it on PCW before assembly"? => Here's two choices.

1 Before accepting a lot of boards from your supplier: * Print some paste on a board * Reflow the paste * Inspect the quality of the solder connection * Make a decision on accpting the board based on that observation.

2 Have your supplier include a soldered board with the shipment.

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CFraser

#18653

BGA solder joint integrity | 15 January, 2002

This sounds like it could possibly be a case of Black Pad. We have had a few issuses with this in the past as well. Who the PWB vendor? I also recommend searching the archives and doing some solder samples with nonpopulated boards

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Romain

#18783

BGA solder joint integrity | 1 February, 2002

the PCB vendor is Multek in germany he made some measures about P content in Ni layer. What is the normal level of Phosporous and what is the upper limit ? thanks Romain

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