Manufacturability and reliability study of ALX polymers for WLP applications

We present the results of study on the manufacturability and reliability of ALX211 polymer in wafer level packaging processes and structures. Previously, we studied the processing windows of ALX211 polymer, where process parameters were studied in lab conditions. The typical manufacturing environment differs from the laboratory environment in that delays between processing steps are typical and unavoidable. Determining the impact of these delays on the stability of the process is critical for determining how the material will perform in a manufacturing line. In this paper, we present new data on the impact of hold times between the main process sequences for the ALX211 process and show that the process is stable with hold times up to 24 hours between process steps. In addition, we present reliability results comparing the performance of polyimide, BCB, and ALX211 as evaluated in a bump-on-polymer test structure. Results of bump shear tests after process completion and after exposure to multiple reflow cycles are presented, as well as results of board level temperature cycling testing.