Optimization of adhesive bond strength to tin plated PWBs: synergy between plating conditions and adhesive formulation

摘要

The fabrication of certain types of amplifier circuits for wireless base stations requires RF circuit boards to be adhesively bonded to metal heat sinks. Large differences in the coefficients of thermal expansion (CTEs) between the two materials, combined with outdoor temperature extremes, impose significant demands on adhesive bond performance. To insure long-term system reliability, adhesive bond strength was optimized at the PWB-adhesive interface through control of both the PWB plated metallization, as well as the adhesive formulation. Tin was selected as the PWB finish for this study because of its compatibility with PWB processing, generally favorable bond strengths with adhesives and environmental compatibility. Peel strength measurements were used to quantitatively measure adhesive bond strength as a function of tin plating conditions and modification of the adhesive formulation.