Edwards Angell Palmer & Dodge LLP
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.
Siliconware Precision Industries Co., Ltd.
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Huang-Chuan Feng-Lung Chun-Sheng
Chang Chien Ho