Additives for grain fragmentation in Pb-free Sn-based solder

摘要

In one embodiment of the present invention, inert nano-sized particles having dimensions from 1 nm to 1,000 nm are added into a solder ball. The inert nano-sized particles may comprise metal oxides, metal nitrides, metal carbides, metal borides, etc. The inert nano-sized particles may be a single compound, or may be a metallic material having a coating of a different material. In another embodiment of the present invention, a small quantity of at least one elemental metal that forms stable high melting intermetallic compound with tin is added to a solder ball. The added at least one elemental metal forms precipitates of intermetallic compounds with tin, which are dispersed as fine particles in the solder.

主权项

1. A method of forming a semiconductor structure comprising:
applying a solder ball on a metallic pad, wherein said solder ball comprises Sn at an atomic concentration of at least 95% and at least one of:
at least one elemental metal that does not form a solid solution with Sn and is selected from Ti, Mo, Co, Ta, and a combination thereof, andinert nano-sized particles having dimensions from 1 nm to 1,000 nm in all directions and comprising a metal oxynitride, a metal carbide, or a metal boride; and reflowing said solder ball at an elevated temperature, wherein said at least one elemental metal or said inert nano-sized particles induce formation of Sn-containing grains as nucleation centers within said solder ball.