Interface-Mechanical and Thermal Characteristics of Ag Sinter Joining on Bare DBA Substrate During Aging, Thermal Shock and 1200 W/cm2 Power Cycling Tests

Abstract

In this article, an SiC die was directly attached on a bare DBA (Al/AlN/Al) substrate via micron-sized Ag sintering at 250 °C without pressure. The micron-sized structure of the Ag–Al joint revealed robust bonding (33.6 MPa), which was attributed to the excellent sinterability of the Ag paste. A high-temperature storage test was conducted for 1000 h at 250 °C, and the thermal shock test was conducted from −50 to 250 °C for 2000 cycles. The shear strength was >30 MPa even after 1000 h of high-temperature storage. Furthermore, the online thermal resistance (R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sub> ) of the direct bonding of SiC–DBA was measured during the power cycling test employing an n-doped 4 H-SiC thermal engineering group (TEG) chip. The SiC–TEG chip exhibited ultra-high power density (1200 W/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ) and ensured that the junction temperature reached 200 °C. The total R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sub> increased from 0.58 to 0.7 K/W after 10 000 power cycles at a swing temperature, ΔTj, of 175 °C, indicating that the increase in the R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sub> was 20.7% at such a large power density. The results revealed that the SiC–DBA power module structure exhibited very good bonding and thermal-resistance reliability, which can be employed as a new structure for next-generation SiC power modules.