Tin plating on heat sink appears to be melting during wave soldering

May 30, 2013

Q. Dear colleages

I have an issue with a part, a heat sink (material: CDA110, hard copper) matte tin plated per ASTM B545, with nickel under plating barrier of 1.9 to 3.8 µm). My concern is this part meets the specification of plating thickness, but when the part passes through the soldering wave, the surface of the part (the plating) seems to be"melting", and causes a "splash" effect and contamination into some components of the PCBA. According to the plating standard, the parts meet with that; also, the temperature of the soldering wave is between 105 to 239 °C. Why are parts failing? I cannot find another reason for this. If have some recommendation, it will be great; thanks in advance!

Guillermo

Guillermo Espinoza
- Guadalajara, Jalisco, Mexico

Junior Quality Engineer [Santa Clara, CA]
Plating Process Engineer [Wenatchee, WA]
Plating Supervisor [Chicago]
Plating Quality Inspector [Chicago]

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