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Solder of tin plating over copper or brass

Dear ALL,

I had my copper pins Tin plated and put them on PCB then re-flow. Sometimes these pins cannot be soldered well to the PCB and I believe the combination ratio of Tin and Lead should be a main effect for this matter. Could someone give me an idea to improve this issue? By the way, I used 90% of Tin and 10% of Lead to plate these pins and the solder that I put on the PCB is 63% of Tin and 37% of Lead, can different combinations of Tin and Lead alloy melt together?

Best regards,

Su Chen-Chen
- Taipei, China

Find a 'phase diagram' for Lead-Tin alloys. Su. It should be in almost any metallurgy book. There you will see that the melting point depends on the alloy, and a 60-40 melts at a lower temperature than a 90-10. Best of luck.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

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