| 摘要 |
PURPOSE:To equalize thermal expansion coefficients of the metal substrate and heat sink and to ease difference between thermal expansion coefficients of the heat sink and semiconductor device, by laminating the metal substrate and heat sink into three layers respectively. CONSTITUTION:The semiconductor device has a power semiconductor element 3 fixed through a heat sink 2 laminated into three layers, on a metal substrate 1 laminated into three layers. The metal substrate 1 and heat sink 2 consist of plates of copper 4 and invar 5 respectively. The thermal expansion coefficient of invar 5 is as small as 1.5X10<-6>/ deg.C. By selecting ratios of thicknesses of the three layers of the heat sink 2 being 1:1:1, the thermal expansion coefficient becomes 11X10<-6>/ deg.C, being smaller than that of copper 4. As a result, difference between the thermal expansion coefficient of the heat sink 2 and silicon power semiconductor element 3 can be reduced. Moreover, by the selecting ratios of thicknesses of the three layers of the metal substrate 1 being 1:1:1, difference between thermal expansion coefficients of the metal substrate 1 and heat sink 2 can be perfectly eliminated, not resulting in cracks in wax for fixing the heat sink 2 to the metal substrate 1. |
