US Patent 7776734 Barrier layer for fine-pitch mask-based substrate bumping

A structure that may be used in substrate solder bumping comprises a substrate (110), a solder resist layer (120) disposed over the substrate, a plurality of solder resist openings (121) in a surface (122) of the solder resist layer, a conformal barrier layer (130) having a first portion (131) over the surface of the solder resist layer and a second portion (132) in the solder resist openings, a mask layer (140) over the first portion of the conformal barrier layer, and a solder material (150) in the solder resist openings over the metal layer. The conformal barrier layer acts as a barrier against interaction between the solder resist layer and the mask layer during solder reflow.