Characterization, modelling, and parameter sensitivity study on electronic packaging polymers

Abstract

Thermosetting polymers are widely used in electronic packaging. For instance, epoxy molding compound is extensively used as an encapsulant for electronic packages to protect the IC chips from mechanical and chemical hazards. It is well known that molding compounds show not only strong temperature dependent but also time dependent behavior. The thermo-mechanical behavior of these polymer constituents determines the performance, such as functionality and reliability, of the final products. In this paper, experimental characterization was carried out to investigate the time and temperature dependent properties of the selected molding compound. Thermal Mechanical Analysis (TMA) was applied to measure the CTE of the materials. Dynamical Mechanical Analysis (DMA) measurement was performed using temperature and frequency sweep modes. Finite element modeling was conducted on typical QFN (Quad Flat Nonlead) package device. Three material models, i.e., full viscoelastic model, temperature-dependent elastic model (1Hz DMA data) and constant elastic model, are used respectively to describe the behavior of the molding compound. The output responses of the simulations are von Mises stress distribution, package warpage and interlaminar stresses. The results show that the von Mises stress and package warpage are significantly different when considering the EMC as full viscoealstic, temperature-dependent elastic and constant elastic. IntroductionAccording to the developing trends of microelectronics, the development and application of polymers becomes one of the bottlenecks for the microelectronic industry. With the introduction of new packaging materials there are many new requirements to improve devices reliability. Therefore, understanding the thermo-mechanical behavior of packaging polymers is critical for the development of packages. In order to be able to conduct process and structure optimization and to predict thermo-mechanical reliability more accurately and further to provide a base for virtual thermo-mechanical prototyping of electronic packaging, a fundamental understanding of the thermo-mechanical behavior of the packaging polymers and its influence on the reliability of the packages is imperative. Therefore, an appropriate material model should be established, and material characterization and numerical implementation should be carried out.In thesis [1], the authors used DMA experiments and timetemperature superposition to verify WLF equation and the viscoelastic model were available to characterize the electronic packaging polymers. Z. Xiong [2] point out that the epoxy molding compound is often modeled as an elastic material in the analysis of plastic-encapsulated IC package. However, many polymers