Electro-wetting enhanced bonding strength

A novel method to enhance bonding strength by using electro-wetting-on-dielectric (EWOD) technique for electronic packaging is described in this paper. The method of liquid treatment is herein employed to enhance bonding strength due to that the low melting point of Sn has been widely used in electronic packaging. Based on the principle of EWOD, we have experimentally changed the contact angle of the molten Sn balls or ring-structure by varying electric energy across the thin dielectric film between the molten Sn and conducting Si substrate. The contact area between the Sn and the substrate can be enlarged due to the decrease of the contact angle. In our experiment, the bonding shear-strength is enhanced by at least 50% with the EWOD technique used. The significant enhancement of the bonding strength has been experimentally verified and has shown promise in flip-chip bonding and microsystem cavity hermetic packaging.