IWLPC (Wafer-Level Packaging) Conference Proceedings

Development of Bump Support Film (BSF) For Improving Package Reliability of WlCSP

Authors: Masanori Yamagishi, Shinya Takyu, Naoya Saiki, Akinori Sato, Kazuyuki Tamura and Rey Alvarado
Company: Lintec Corporation and Qualcomm Technologies, Inc.
Date Published: 10/18/2016   Conference: IWLPC (Wafer-Level Packaging)

Abstract: Solder joint crack is increasing with increasing of warpage caused by larger Wafer Level Chip Size Package (WLCSP). We already proposed Bump Support Film (BSF) which composed of base film layer and Pressure Sensitive Adhesive (PSA) layer and Bump Support Layer (BSL) which covers beside the bumps with heat lamination. In this study, we succeeded in forming the BSL without voids beside the bumps by optimizing the thickness of BSL. We also succeeded in removing BSL residues at the top of the bumps with top-cutting or plasma etching. In addition, the top-cut IC chip with BSL showed higher reliability than the IC chip without BSL after Thermal Cycle Test (TCT).

In order to apply to various pitches, bump heights and patterns, we studied changing PSA into bump absorption layer which was controlled elastic modulus at the large deformation region. As a result, we achieved a reducing the plasma etching time dramatically for removing BSL residues at the top of the bumps.

Key Words: 

Thermosetting Resin, Bump Absorption Layer, Elastic Modulus at the Llarge Deformation Region

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