Thermal and mechanical properties of sintered Ag layers for power module assembly

Abstract

Purpose -The purpose of our paper is to investigate thermal and mechanical properties of Ag sintered layers used for assembly of SiC diode to Direct Bonding Copper (DBC) interposer. How SiC devices are assembled to ceramic package defines efficiency of heat transfer and mechanical support. Design/methodology/approach -Ag microparticles, sized 2-4 m and flake shaped, were used as joining material. The parameters of sintering process were as follows: temperature 400°C, pressure 10 MPa and time 40 min. It was found that after sintering and long-term aging in air at 350°C the adhesion is in the range of 10 MPa, which is enough from a practical point of view. The thermal properties of the SiC die assembled into a ceramic package were also investigated. In the first step, the calibration of the temperature-sensitive parameter VF (IF ϭ 2 mA) was done and the relation between VF and temperature was found. In the next step, the thermal resistance between junction and case was determined knowing junction and case temperature. Findings -For SiC diode with Au bottom metallization joined to the DBC interposer by Ni/Au metallization by Ag microparticle layer, R th j-c is in the range of 2-3.5°C/W, and for SiC diode with Ag bottom metallization joined to DBC interposer with Ag metallization by Ag microparticle layer, R th j-c is in the range of 4.5-5.5°C/W. Research limitations/implications -In the future, research on thermal resistance of SiC diodes assembled onto the DBC interposer with Au and Ag metallization in the temperature range up to 350°C needs to be carried out. To do this, it necessary to find a solution for the attaches that leads to ceramic package able to work at such high temperature. Originality/value -Obtained results are comparable with results mentioned by other studies for eutectic Au/Sn or SAC solder joints; however, the solution proposed by us can properly work at significantly higher temperatures.

Technological aspects of silver particle sintering for electronic packaging

“…However, there is lack of discussion on errors and accuracy of the method. There is only a belief that accuracy may depend on the calibration of the measurement system (Sabbah et al , 2012) and location of the thermocouple (Myśliwiec and Kisiel, 2015).…”

Joints realized by sintering of pressureless Ag paste

“…This new nanoscale high thermal conductive die attach silver paste is promising low-temperature sintering material because of its possibility not only to improve the performance and reliability of power electronic devices but because of its possibility for increasing the density of integrated circuits and decreasing the dimension of interconnections in microelectronic systems as well (Lukacs et al, 2017;Liu et al, 2018aLiu et al, , 2018bSiow, 2012). This high electrical and mainly thermal conductive material has great potential for new generation of joints in power electronics.…”

Material and technological aspects of high-temperature SiC device packages reliability

“…The second problem that needs to be solved is the technology of SiC die assembly to the ceramic package. We propose Ag sintering technology (Myśliwiec and Kisiel, 2015). The Ag flake-shaped 2-4-m microparticles were used as the joining material.…”