Cu Pillar flip chip assembly: Chip attach process failure mode study

An experiment is conducted to study failure mechanism during flip chip attach process for Cu Pillar bumped Si device that uses mass reflow assembly technology. A three-leg design of experiment (DOE) is conducted, which includes two UBM sizes, two different Cu pillar height, and with / without polyimide option to collect basic failure information. Finite element software is used to correlate the failure mode and identify the Si - Cu pillar bump - substrate interactions. Based on the experiment and finite element analysis results, a simple shallow beam mechanical model was recommended to be a basic start point of Cu Pillar flip chip assembly technology application. Results are discussed in details.