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Black Tar on ENIG

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#72933

Black Tar on ENIG | 20 October, 2014

I have seen a couple of references to Black Tar, Not Black Pad. Apparently, it occurs only on the solder side of PTH's after wave solder and primarily on the edges of the land. It is characterized by a black coloration (Not Ni corrosion?) and non-wetting. The component side does not exhibit any problems. Except for a couple of references in the NPL Solder Defects database, I haven't been able to find any info.

Anyone have any input? Thanks, Rick

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#72939

Black Tar on ENIG | 21 October, 2014

"Electroless Nickel Immersion Gold and Black Tar. What Is It and How Can It Be Prevented?" James Trainor, OM Group Electronic Chemicals, LLC SMTAI 2014 SUB2

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#72940

Black Tar on ENIG | 21 October, 2014

Thanks for the input. I read that paper. I'm not convinced the Pb stabilizer and bath MTO's are a cause of the Black Tar defect. If that were the case, given the history of Pb stabilizers and ENIG, I would have thought that there would have been many more examples of the occurrence of this defect. In addition, I don't see that this addresses the occurrence of the defect only on the wave side of the PCB. I say this because of 2 actual examples I have examined plus the 2 examples given by the NPL Solder defects Database.

Thanks, Rick

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