IMC integrity for Sn96.7-Ag3.7 polymer core solder ball in BGA package

Abstract

Since the high-pin count package is strongly desired from the high performance of commercial electronic products, the ball-grid-array (BGA) assembly is indeed suitable to fit this need. Using the polymer core solder ball in lead-free BGA package instead of solid solder ball is a promising choice due to the lighter weight benefiting the self-alignment in solder adhesion reducing the shift ball issue and the good elasticity protecting the clamping substrates, avoiding the leakage or open phenomenon in circuit operation. Comparing the constitution and the IMC thickness among the solid solder ball and polymer core ball groups, the polymer core solder ball demonstrates not only the similar structure, but the better stability in adhesion. By the way, adopting the polymer core solder ball as a bump replacing the conventional SnPb solder bump is also a feasible method in flip-chip package requiring the adhesion metal medium with a lower melting point.