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Lead Free Immersion SIlver PCB-->Creeping Corrosion

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#59781

Lead Free Immersion SIlver PCB-->Creeping Corrosion | 3 September, 2009

Hi All,

I have few questions about creeping corrosion that potentially happen on lead free immersion silver PCB as below:

1) What test that we can conducted to verify whether the failure we seen is due to creeping corrosion? 2) I heard that lead free Immersion silver PCB has high potential of getting this creeping corrosion if subjected to high humidity and sulfur environment for a few months.....If this the cause of the failure, who should responsible for that..PCB supplier or PCBA assembly house? 3) Any way that we can practice to avoid this creeping corrosion? 4) Is there any way that we can choose to rework this defective board?

Many thanks, Sean

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#59783

Lead Free Immersion SIlver PCB-->Creeping Corrosion | 3 September, 2009

Creeping corrosion occurs on bare metal. Most commonly, it is seen on boards with thin protective coatings [eg, bare copper, immersion silver, organic solderability preservative]. Look here: * enthone.com/docs/AlphaSTARCreeping.pdf * circuitree.com/.../BNP_GUID_9-5-2006_A_10000000000000550300

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#59787

Lead Free Immersion SIlver PCB-->Creeping Corrosion | 4 September, 2009

Dear Davef,

Thanks for sharing with me..I observed this creeping corrosion tend to appear on PCB via hole rather than other PCB location. Why this problem did not appear on PCB traces?

Besides, I also notice that this problem only appear on the PCBA bottom side..Why its like that?

Thanks again, Sean

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#59808

Lead Free Immersion SIlver PCB-->Creeping Corrosion | 8 September, 2009

Maybe your solder mask supplier can provide additional background

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#59884

Lead Free Immersion SIlver PCB-->Creeping Corrosion | 17 September, 2009

All,

We know that incomplete immersion silver could potentially lead this creeping corrosion. Is there any way to check bare PCB for incomplete immersion silver coverage, especially on the via hole area?

Thanks, Sean.

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