Thermomechanical behavior of flexible substrates

Abstract

This paper investigates the driving mechanisms causing the deformation of thin flexible substrates used for multi-chip technology. A finite element model was created and simulated to analyze the deformation of the substrate when subjected to high temperature processing. Modeling results and assumptions were successfully validated via a temperature dependent Shadow Moire. Results show a 13.23% error difference from modeling vs actual data. Based from the established model, a 2³ factorial design of experiment was conducted to explore three parameters such as symmetry of the substrate stacking sequence, presence of metal structures in the substrate and presence of a rigid holder attached on the substrate. It was found that the main contributor is the presence of the rigid holder on the substrate. In addition, results show that there are two driving mechanisms: a) a local mismatch of properties among the materials comprising the substrate, and b) a global mismatch of properties between the substrate and its adjacent structure, with the latter having the greatest impact.