Fabrication of bumping mask for flip-chip process on stainless steel using through mask electrochemical micro machining(TMEMM)

Abstract

In order to fabricate bumping mask which is used for making bump during flip-chip package, the TMEMM process was used. The TMEMM process uses electrochemical reaction between electrode surface and electrolyte. In this study, we optimized the TMEMM process to fabricate bumping mask by controlling the process parameters such as electrolyte temperature, cathode size, exposed cathode area and agitation speed. By controlling process parameters, the effect of current density distribution and mass transport could be investigated. After the TMEMM process, Optical Microscope and Field Emission Scanning Electron Microscope were used to analyze the result. As a result, the bumping mask which has 250.6 μm of average hole diameter with 2.8% of CV value and smooth surface was fabricated. © The Electrochemical Society.