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Hello Technetters:
(Put on your metallurgical hats for a moment.)
I ran into an unusual circumstance the other day that has me baffled. We
soldered down a surface mount glass diode using conventional processes (Sn63
water soluble solder paste, convection reflow). The components were
mis-oriented therefore had to be removed. To our dismay, the components
wouldn't separate from the board (polyimide multilayer). Even though the
solder was molten, the components wouldn't budge. Finally, the pads lifted off
the board so I tried to remove the pads from the component, to no avail.
It turns out that the component's base metal is pure silver which is then
solder coated. The cross section looks like the silver dissolved with the
solder, with the resultant alloy in contact with the copper pad (which was
originally solder coated).
Could the soldering process have created a metallurgical bond between the
silver and the copper?
Thanks for your assistance,
Jim Marsico
(516) 595-5879
[log in to unmask]
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