Selective application by electroless plating of a tin-whisker impenetrable metal cap to metals on electronic assemblies

摘要

Since lead-tin solder was outlawed, electronic circuits constructed with lead-free tin solders have been plagued growth of whiskers of tin emanating from the tin soldered and/or tin coated surfaces. Such whiskers often short out the electronic circuits when present. The growth of tin whiskers in such electronic circuits (i.e., those fully or partially populated with components is addressed here by depositing a tin-whisker-impenetrable metal cap on all exposed tin coated surfaces in the circuit.;In the process, metal surfaces where no cap is desired are masked, where after all exposed metal surfaces are cleaned, followed by immersing the entire circuit in an electroless bath, e.g., a nickel electroless bath, for a time sufficient to form a metal cap on all exposed metal surfaces, removing the circuit from the bath, rinsing and de-masking covered surfaces.