US Patent 7341949 Process for forming lead-free bump on electronic component

A process for forming a lead-free bump on an electronic component includes preparing the electronic component with at least one bond pad and a passivation layer formed thereon; forming an under bump metallurgy (UBM) structure on the passivation layer and the bond pad; applying a photoresist over the passivation layer, the photoresist having at least one opening corresponding to the bond pad; depositing a thick copper layer (about 1 to 10 μm thick) in the opening by electroplating; applying a copper-free or low-copper-content solder material on the copper layer; and performing a reflowing procedure under a suitable reflow temperature profile to allow copper ions to diffuse from the copper layer to the solder material so as to form the lead-free bump. This increases the copper content in the solder material but not raising the reflow temperature profile, thereby preventing deterioration of the photoresist due to over heat.