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June 2011

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TechNet E-Mail Forum <[log in to unmask]>, Pete <[log in to unmask]>
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Thu, 9 Jun 2011 09:36:43 -0500
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Can it still be "Black Pad" after soldering, if it isn't, prior to soldering?  

All of the "Black" in thoses photos is after the wave solder has had it's way with the plating.  If the reflow side is fine, I'd focus on what's going on in the wave.  Contaminents in the solder?   Is this a high-P ENiG?  If the wave is applying more heat for a longer period of time than reflow, are some of the metals separating?

I've seen this before, not nearly as extreme, but I know our wave process was rather agressive and not well maintained.  It's actually somewhat common on our PTH parts.  The black tends to appear on pad areas where it appears solder wetted, then surface tension pulled the solder off the gold onto the lead.  Sometimes it appears in the craters of the filleted solder.  But otherwise, the joints seem robust.   AFAIK, we haven't experienced failures from this.  I may have a few old boards laying around, I'll see if I can find a sample.

Pete

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