The Effect of Reflow Process on the Physical Properties of Die Attach Adhesives

Suitable selection of packaging materials is critical for microelectromechanical system (MEMS) devices to maintain their performance and to provide physical protection, mainly to the electrical connections. Several different materials can be used in MEMS packaging and different properties are required from these materials. Temperature can markedly influence the properties of polymer materials used in the packaging of MEMS devices, which may critically affect their performance. For die attach adhesives (DAA) the mechanical moduli of the material are typically key properties to ensure their compatibility with different MEMS components. Another critical parameter is the coefficient of thermal expansion (CTE). It is common that the temperature changes during the assembly and use of MEMS components, which can easily lead to thermo-mechanical stresses in the packages and thereby to failures. The main sources of these stresses are the mismatches between the CTEs of different materials and the unsuitable mechanical properties of materials. In addition to the mechanical properties, the electrical properties of the DAAs are critical for the functionality of MEMS devices. They may also be easily changed due to temperature. Consequently, it is essential to investigate the stability of both mechanical and electrical properties of DAAs at various environments. In this study, the effect of the high temperature during a reflow process on the properties of two DAAs was investigated.