CPS’s aluminum silicon carbide (AlSiC) is a metal-matrix composite ideally suited for base-plate material for IGBTs used in high-power applications. The low isotropic coefficient of thermal expansion (CTE) value of AlSiC-9 (8 ppm/°C for 30°C to 100°C) is compatible with the thermal expansion value of the die or substrate used in IGBT applications. The device-compatible CTE of AlSiC eliminates the need for stress compensation material layers that are required in Cu (CTE = 17 ppm/°C) baseplate assemblies. This CTE compatibility reduces the mechanical stresses on IGBT die and substrates that are induced by thermal power cycling, which improves reliability of the substrate attachment and reduces die-cracking failures.
In high-power applications (greater than 1200 V, 400 A), IGBT modules assembled with AlSiC baseplates are found to have a service reliability of many tens of thousands of thermal power cycles over that of Cu-based equivalent systems. AlSiC is also a lightweight material (one-third that of Cu), which makes it ideal for cooling weight-constrained IGBT applications. Furthermore, AlSiC has both a higher strength and stiffness than Cu, which, combined with its lower weight, makes AlSiC assemblies more tolerant of shock and vibration. CPS fabricates standard of 190-mm x 140-mm, 140-mm x 130-mm and 140-mm x 70-mm baseplate formats, as well as custom formats.