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|Microstructure Modeling and Reliability Analysis of TLPS Joining Technology for High Power Electronics|
|Keywords: modeling, TLPS, High power electronics|
|The continuous increase in application temperature of power electronic devices, due to the growing power density, miniaturization, and functionality in military and commercial applications, requires new packaging technologies with high temperature and reliability capabilities. Currently, the traditional maximum allowable temperature of power electronics (125 ̊C) is a limiting factor for high temperature applications such as space exploration, drilling, avionics, and electronic vehicles. Over the last several years, substitution of wide bandgap compound semiconductor (e.g., SiC, GaN) devices for silicon ones has improved the efficiency of these power electronic systems and extended the maximum allowable temperatures to 475 ̊C. However, this increase in device operating temperature creates the need for robust high temperature packaging materials, especially interconnects and attachments. High temperature solders are often too expensive, too brittle, or too environmentally toxic to be used, leading to increased study of low temperature joining techniques, such as solid phase sintering and transient liquid phase sintering (TLPS), for producing high temperature stable attachments. TLPS is an emerging electronic interconnect technology enabling the formation of high temperature robust joints between metallic surfaces at low temperatures by the consumption of a transient, low temperature, liquid phase to form high temperature stable intermetallic compounds (IMCs). The performance and durability of these materials is strongly dependent on their microstructure, which, in turn, is determined by their processing. The complicated process of IMC formation through eutectic solidification and the extensive number of parameters affecting the final microstructure, including joining temperatures, durations, and pressures, makes it impractical to experimentally study the effect of each factor. Phase-field modeling (PFM) is a powerful thermodynamic consistent method in mesoscale modeling that simulates the evolution and formation of intermetallic compounds during the solidification process, providing considerable insight into the final microstructure. In this paper a modified PFM method is introduced to analyze and simulate microstructure evolution during liquid-phase sintering. This method has the great potential to model the IMC formation during solid-liquid interactions in a transient liquid phased sintering. Application of this method facilitates the manufacturing and can optimize the influential factors to prepare higher quality interconnections. Optimized TLPS interconnection can be an outstanding substitute for hazardous high lead containing solders which are widely used in most of power electronics applications. The objective of this paper is to provide the insight into the processing of a reliable high temperature TLPS and facilitate their application in power electronics industries.|
|Ali Moeini, PhD Student
University of Maryland CALCE Lab.
College Park, MD