Kester - Lead-free SMT Soldering Defects - How to Prevent Them

Our thanks to Kester for allowing us to reprint the following article.
By Peter Biocca, Key Accounts Technical Manager, Kester

Tin-Silver-Copper alloys are the primary choice for leadfree SMT assembly. Although there are other options available such as alloys containing bismuth or indium and other elements, tin-silver-copper solders, also known as SAC alloys are by far the most popular. They are used by approximately 65% of users, as last surveyed in 2011.

The lead-free SMT process differs from a 63/37 process in numerous ways. A good understanding of these differences when using SAC alloys, will enable process engineers to bring about the necessary changes to the SMT process and reduce soldering defects, increase lead-free assembly reliability and maintain production yields.

Often when a manufacturer transitions to lead-free soldering an increase in defects is noticed. This is often the result of a not properly implemented process. A welldefined, optimized and controlled lead-free process will not augment defect rates...

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