Power module
A power module includes a base plate, a ceramic insulating substrate bonded on the base plate, and a semiconductor element bonded on the ceramic insulating substrate, wherein a surface of the base plate on a side opposite to the ceramic insulating substrate has a warp with a convex shape, and a linear thermal expansion coefficient α1 (×10 −6 /K) of the base plate and a linear thermal expansion coefficient α2 (×10 −6 /K) of the ceramic insulating substrate when a temperature decreases in the range of 25° C. to 150° C. satisfy the following Expression (1). α 1 - α 2 ( α 1 + α 2 ) / 2 × 100 ≤ 10 ( 1 )
1. A power module comprising:
a base plate;
a ceramic insulating substrate bonded on the base plate; and
a semiconductor element bonded on the ceramic insulating substrate, wherein
a surface of the base plate on a side opposite to the ceramic insulating substrate has a warp with a convex shape, and
a linear thermal expansion coefficient α1 (×10 −6 /K) of the base plate and a linear thermal expansion coefficient α2 (×10 −6 /K) of the ceramic insulating substrate when a temperature decreases from 150° C. to 25° C. satisfy the following Expression (1).
α
1
-
α
2
(
α
1
+
α
2
)
/
2
×
100
≤
10
(
1
)
2. The power module according to claim 1 , wherein a difference between a size of the warp of the base plate bonded to the ceramic insulating substrate and the size of the warp of the base plate before being bonded to the ceramic insulating substrate is 20 μm or less per a length of 10 cm.
3. The power module according to claim 1 , wherein the ceramic insulating substrate comprises a ceramic base material and metal layers provided to both surfaces of the ceramic base material,
the ceramic base material is formed of AlN, Si 3 N 4 , or Al 2 O 3 ,
the metal layers are formed of at least one selected from the group consisting of Cu, Al, Mo, an alloy comprising Cu and Mo, and an alloy comprising Cu and W, and
the linear thermal expansion coefficient α2 of the ceramic insulating substrate is 5 to 9 (×10 −6 /K).
4. The power module according to claim 1 , wherein
the base plate comprises
a metal matrix composite comprising a metal comprising Al or Mg and at least one selected from the group consisting of SiC, Si 3 N 4 , Al 2 O 3 , SiO 2 , and AlN,
an alloy comprising Cu and Mo or Cu and W, or
a multilayer metal plate formed of Cu and Mo or Cu and W, and
the linear thermal expansion coefficient α1 of the base plate is 5 to 9 (×10 −6 /K) and a heat transfer rate of the base plate is 150 W/mK or more.
5. The power module according to claim 1 , wherein the surface of the base plate on the side opposite to the ceramic insulating substrate is machined or ground.
6. The power module according to claim 1 , wherein a flatness of the surface of the base plate on the side opposite to the ceramic insulating substrate when a heat radiation component is attached to the surface is 30 μm or less.
7. The power module according to claim 1 , wherein the semiconductor element is formed of any one of Si, SiC, or GaN.
8. The power module according to claim 1 , the power module being used as a driving inverter for a train or an automobile.