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Re: Zine migration


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Posted By<" ">J. Futch on December 18, 2001 at 10:56:16:

In Reply to: Zine migration posted byBen on December 17, 2001 at 23:42:50:

: Hi,
: I am an electronic engineer and puzzled by "metal migration" problem on component leads coating. it is highly appreciated if any one can give me some idea on the following phenomenon:
: The lead is copper alloy and coated with tin-lead plating. After a high temperature (~60 - 80C) process for hours, the solderability decreases due to zine migration from the alloy to the surface.
: Here is my questions:
: 1. Does the decrease in solderability be caused by zine migration? Or do those metals can be migrated so easy?
: 2. Does the "high temperature", only 60 - 80C for several hours, cause such metal migration? Or other reason?
: Thank you in advance if any anybody can help.

: Cheers,
: Ben

Ben,

I have seen this as well. I am not sure why or what is going but, we re-tin the leads after the temperature soak to facilitate better solderability. If the component is already on the board then we don't worry about it. Do you have to pre-tin the leads before your temperature cycle? If you get a reason for the decrease in solderability let me know!

Josh




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