Epoxy Mold Compound Characterization for Modeling Packaging Reliability

This paper presents a study on Epoxy Mold Compounds (EMC) used as encapsulant in Quad Flat No-lead (QFN) packages. The goal is to characterize the behaviour of the two different EMCs during thermal cycling to be able to model and predict the lifetime of the package. A 3-point bending (3PB) test in temperature is used for the mechanical characterization of the EMCs. The different III-V dies substrates used in the QFN are also characterized with this method. The flexural modulus and the glass transition temperature (Tg) are characterized for the epoxies. The modulus values match the theoretical data while the mean value of Tg in the transition zone for each material is estimated at 100°C, which is 35-40°C below the values given by the manufacturer and is in the thermal cycling test range. The silica filler rate in the resins is also studied according to the sample position to the resin injection point. Modelling of the flexural experiments has been done with ANSYS Mechanical to make sure to understand how to model the mechanical behaviour of the EMC.