Abstract
The thermal cycling life of direct bonded aluminum (DBA) and active metal brazing (AMB) substrates with two types of plating—Ni electroplating and Ni–P electroless plating—was evaluated by thermal shock tests between −50 and 250 °C. AMB substrates with Al2O3 and AlN fractured only after 10 cycles, but with Si3N4 ceramic, they retained good thermal stability even beyond 1000 cycles, regardless of the metallization type. The Ni layer on the surviving AMB substrates with Si3N4 was not damaged, while a crack occurred in the Ni–P layer. For DBA substrates, fracture did not occur up to 1000 cycles for all kind of ceramics. On the other hand, the Ni–P layer was roughened and cracked according to the severe deformation of the aluminum layer, while the Ni layer was not damaged after thermal shock tests. In addition, the deformation mechanism of an Al plate on a ceramic substrate was investigated both by microstructural observation and finite element method (FEM) simulation, which confirmed that grain boundary sliding was a key factor in the severe deformation of the Al layer that resulted in the cracking of the Ni–P layer. The fracture suppression in the Ni layer on DBA/AMB substrates can be attributed to its ductility and higher strength compared with those of Ni–P plating.
Highlights
Power electronic modules, such as converter and inverter systems, have been widely used in transportation, including electric vehicles, aircraft, and high-speed railroads
With the increasing use of wide-bandgap (WBG) semiconductor devices, such as silicon carbide (SiC) and gallium nitride (GaN), which provide great opportunities to develop power electronic systems with increased power densities, high reliability in extreme environments, and higher integration, the development of high-temperature-operating power devices allows for the use of power electronic modules at high temperatures (>250 ◦ C) [1,2]
A power electronic substrate is located between a semiconductor die and heat sink and transfers the heat generated in the semiconductor to cooling plates [3,4,5]
Summary
Power electronic modules, such as converter and inverter systems, have been widely used in transportation, including electric vehicles, aircraft, and high-speed railroads. DBA/AMB basically has a ceramic insulator plate composed of materials such as Al2 O3 , AlN, and Si3 N4 Both sides of an insulator plate are metalized by aluminum (Al) or copper (Cu) to function as a thermal and electrical conductor layer [8]. Thermomechanical stress in DBA/AMB substrates at high temperatures depends on the material properties of the ceramic and metal components. The material design of the DBA/AMB substrates became an important issue, since it determines their thermal cycling reliability in the power electronic module. A thermal shock cycling test of DBA/AMB substrates with various ceramics plated with Ni and Ni–P layers was implemented to investigate their high-temperature reliability for a WBG power electronic module. The fracture suppression mechanism in the Ni layer on the DBA/AMB substrate was examined with a stress analysis by finite element method (FEM) simulation
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