Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Immersion Tin over Copper Pad Deterioration/Corrosion

#25680

Immersion Tin over Copper Pad Deterioration/Corrosion | 9 September, 2003

Anyone have any experience with immersion white tin over copper plating? We are seeing opens develop under BGAs after we bake and conformal coat. And when we lift the parts the pads are 60% of the original size. Need some advice on possible causes. Thanks in advance for your help.

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mantis

#25681

Immersion Tin over Copper Pad Deterioration/Corrosion | 9 September, 2003

We have also seen A similar issue were by the pad would completly come away from the bga land , when lightly scratched with your finger.These boards hadnt even been through our process yet and where fresh out of the pack.These issue was seen at incoming inspection.I belive this to be a vendor related problem and am waiting ot hear back from them some time next week. Regards,

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#25685

Immersion Tin over Copper Pad Deterioration/Corrosion | 9 September, 2003

Greg: Where do the pads go? Do you mean the copper disappears? Or do you mean that 'only 60% of the metal is solderable'? Er, watt?

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Dennis O'Donnelll

#25687

Immersion Tin over Copper Pad Deterioration/Corrosion | 10 September, 2003

This is a problem of contamination in the plating bath. Most prominent with white tin and some gold over nickel plating processes. Rather than argue with your vendor over the issue, and to avoid future recurring problems, I use either HASL or electrolytic gold over electrolytic nickel. These two processes will not produce this defect. Feel free to call me if you need details on this. Regrds, Dennis O'Donnell Precision PCB Services, Inc. (408) 436-4790 http://www.pcb-repair.com

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