Patent ID: 8252677
Filing Date: 2012-08-28
Classification: B22F,B23K,H01L,H05K

Abstract:
1. A method of forming solder bumps on a substrate, comprising: forming a plurality of contact points on the substrate; depositing a layer of a surface finish material over and directly in contact with the plurality of contact points, the surface finish material comprising nickel and phosphorous; depositing a layer of a flux material on the layer of the surface finish material; forming a ball mounting mask having a plurality of openings each aligned with a respective one of the contact points on the substrate; disposing a plurality of solder balls in direct contact with the layer of flux material, each solder ball of the plurality of solder balls having a solder material comprising a lead free solder alloy and phosphorus; applying a solder reflow process to the plurality of solder balls disposed on the layer of flux material to configure a plurality of solder bumps on the substrate; forming an inter metallic compound layer comprising at least a portion of the surface finish material dissolved in at least a portion of the solder material.