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June 29, 2011 - Updated
June 27, 2011 - Originally Posted
ENIG and Black Pad
We have noticed a problem on ENIG boards in our WAVE process. The problem looks similar to Black Pad. We do not know how to identify the problem, or where to begin to find a resolution to the problem. Here are some facts: - Black residue is on the vias and this on the solder side.
- Component side SMT parts do not exhibit the problem.
- Boards are processed Pb-free - SAC305, with no-clean water based flux.
- THTs will not wet after residues appear (for touch up process)
- Blowholes appear to accompany the defect but are not always present.
Hope you can help identify the problem and how to eliminate it.
G. R.
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| Expert Panel Responses |
You likely have a sulfur contamination issue. Sulfur residues can occur when there is ineffective cleaning after the nickel plating process.
Dr. Craig D. Hillman
CEO & Managing Partner
DfR Solutions
Dr. Hillman's specialties include best practices in Design for Reliability, strategies for transitioning to Pb-free, supplier qualification, passive component technology and printed board failure mechanisms.
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