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Silver sulfide.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Ashok Dhawan
Sent: Tuesday, August 31, 2010 6:18 PM
To: [log in to unmask]
Subject: [TN] Black material under plating
Anyone encountered black coating like material under plating of heatsink ?
The package is TO 220. Upon desoldering the package or plying off the board
with a nose plier, it sheared off at plating. A portion of plating stayed on the
board while remaining on heatsink plate. The surface on parts' heatsink where
plating peeled off is black in color. On scratching with sharp tool, it appears to
have copper under.
The surface is tin lead plated. Any guesses what this black surface could be ?
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