Increased high-temperature stiffness of an epoxy-based molding compound through high-temperature storage

Abstract

This paper investigates the tensile mechanical properties of epoxy-based molding compound (EMC) films containing 88 % silica filler. The EMC material was molded under 175 °C at 13.8 MPa pressure for 2 min and cured at 175 °C for 5 h to form 200 μm films. The films were cut into a dog-bone shape, whose stress–strain (SS) curves were measured by quasi-static tensile test at a test temperature (T_te) of room temperature (RT), 100 °C, and 150 °C. As T_te increased, all the initial curves changed from brittle-like to ductile-like. Next, the films were subjected to storage at a temperature of 150 °C (T_st⁰) for 24, 168, and 500 h. With increasing storage time, the stiffness of the films at T_te = 150 °C increased, while their RT counterpart did not show significant changes. This T_te-dependent difference in mechanical property was likely caused by oxidation as revealed by Fourier transform infrared spectroscopy analysis, and consequently resulted in a difference in stress distribution between 150 °C and RT in an EMC-on-metal assembly, which was confirmed by finite element method stress simulation.