A study of the effect on deformations for ACF applications

Abstract

This research uses the validated finite element analyses to study the thermo-mechanical behaviors of the anisotropic conductive films (ACFs) under thermal test with a temperature range of 120degC to -40deg C for three cycles. The CAE software, ANSYS, is used to investigate the reliability assessment of ACF in a flip-chip on flexible substrate (FCOF) with a quarter model under thermal cyclic loading. Owing to fact that the edge effect of the ACF results on the different shapes in manufacture; therefore the edge of the ACF in FCOF package is modeled to be straight and concave shape in order to obtain the warpage and stress results. Moreover, this paper also considers the effects of height of bump and thickness of ACF, because they are the key dimensions for design. The behavior and reliability of components on the FCOF will be studied in detail under the thermal cyclic loading. It is obvious that the maximum von Mises in the devices always happens at the interface near the bump, pad and ACF which may bring about crack initiation. In particular, at a higher temperature, the maximum stress still happens at the interface between the bump- ACF and the ACF-pad at corner of package. That is, a delaminated failure might easily happen during the thermal cyclic testing. The different edged shapes of ACF have similar behavior and the warpage range will be enhanced with the ACF height. Such influencing factors in modeling dimensions are very important for the design of finite element model and packaging process.