Method for forming fine-pitched solder bumps

摘要

A method for forming solder balls that have larger spacings between them and electronic devices containing such solder balls are disclosed. In the method, an additional layer of a leachable metal such as gold or silver is used between an under bump metallurgy layer and a solder bump subsequently formed. This allows the formation of the under bump metallurgy layer prior to the deposition of the solder material into a window formed in a photoresist layer. The present invention allows the underfill of a solder window, instead of an overfill which is normally required in a conventional method.