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|Reliability of transient liquid phase sintered (TLPS) joints under temperature and power cycling loads|
|Keywords: power cycling, reliability, TLPS sinter joint|
|With the recent development of a wide range of highly efficient, wide bandgap (WBG) semiconductor-based, power electronic devices that are able to manage ever larger power levels at higher frequencies over wider temperature ranges with lower power loss, there is the potential for improved performance of power electronics with a sizeable reduction in cost, size and weight. However, these advantages can only be realized if approaches can be developed for reliably packaging and integrating these devices into systems. These packaging approaches must be stable at these high temperatures and not adversely impact system efficiency and performance. As the traditional high temperature die attach solution of high lead solder is being phased out by the expanding ban on lead containing materials, the demand for a new technology is growing. Transient liquid phase sintered (TLPS) joints have the potential for reliable application in high temperature and dynamic environments. In this paper, the durability of TLPS joints under power and temperature cycling conditions is investigated. Two diode types are attached to three types of substrates by TLPS and cyclically tested under a maximum allowable current condition, with the device temperature measured in-situ for condition monitoring. Two types of diodes from different manufacturers were attached to three types of power substrates (DBC, DBC with Ni plating and DBA) by TLPS. Samples were tested by power cycling at maximum rated current capacity of the diodes. The dwell time (25 s) in the on-state was selected so that the diodes reached their maximum steady-state temperature conditions and the dwell time (35 s) in the off-state was selected to ensure that the diodes cooled to room temperature. The packages were tested until failure of the diodes or an increase in the component temperature to a predefined criterion. The diode failure mode is short circuit which results in a temperature decrease and any failure in the substrate or TLPS joints results in temperature increase. We eliminated the use of wire bonded interconnection on the top surface of the diode and replaced it with a spring-type press connection to decrease the number of possible failure mechanisms in the package. Initial results show cracking of the die and fatigue of the die attach. Temperature cycling from -55C to 200C is also being conducted.|
|Patrick McCluskey, Professor
University of Maryland, College Park
College Park, MD