AN ALTERNATIVE SURFACE FINISH FOR TIN-LEAD SOLDERS

A novel tin electrodeposition chemistry and process has been developed , This process produces smooth, satin bright tin deposits that have st able, large grain structures. The deposits contain very low organic co ntent and, as a consequence, exhibit excellent ductility, solderabilit y and reflowability. The chemistry is capable of operating at elevated temperatures over a wide range of current densities, and is thus appl icable to rack, barrel and reel-to-reel operations. All chemical compo nents, including breakdown products, are fully analyzable with convent ional analytical methods. Extensive bath life studies show that the de posit appearance and material properties, including grain structures, are stable in relation to the age of the electroplating chemistry, In addition, the grain refiners used are highly stable, and have few brea kdown products as the chemistry ages, All these features imply a robus t process that has been confirmed in various manufacturing environment s, This tin electroplating process has been utilized in plating coatin gs for connectors, solder bumps, PWBs and components for semiconductor applications.