Dynamic peeling process of IC chip from substrate based on a 3D analytical model

Abstract

A 3D analytical approach is proposed to investigate the peeling mechanism of IC chip from substrate, which is important for reliable electronic packaging. Chip-adhesive-substrate system is considered as a composite structure composed of a rectangular plate of free edges and a clamped circular plate bonded with an interfacial layer. Peeling a chip from substrate is treated as the interfacial fracture of this structure. Based on the theory of elasticity, the problem of interfacial fracture is reduced to a set of coupled integral and differential equations. An analytical scheme is developed to solve these equations. With the approach, dynamic evolution process of peeling is analyzed due to various needle ejecting and vacuum absorption. Stress distributions of both chip and adhesive at different stages of peeling process are obtained. It is shown that stresses of both chip and adhesive are nonuniformly distributed in the whole region. As a result, peeling initiates from four corners, and propagates toward the center of interface with a very complex advancing front. For a definite displacement of needle point, peeling process is determined by both the magnitude and application time of vacuum absorption. When these two parameters locate in a specific region, a chip can be separated completely from substrate without damage. Furthermore, peeling process is sensitive to the position deviation of needle point. In case the position deviation is beyond a certain range, peeling process is incomplete.