Ceramic circuit board and method of making the same

Abstract

A ceramic circuit board for use in packaging an electronic element includes a ceramic-copper plate, and a heat-dissipating unit that is adapted for dissipating heat from the electronic element. The ceramic-copper plate includes a ceramic substrate that has opposite first and second surfaces, and a through-hole formed through the first and second surfaces, a top copper pattern that overlies the first surface of the ceramic substrate and that has at least two conducting portions spaced apart from each other, and a bottom copper layer that underlies the second surface of the ceramic substrate. The heat-dissipating unit includes a heat-dissipating layer that is disposed in the through-hole of the ceramic substrate above the bottom copper layer and that has a thermal conductivity larger than that of the ceramic substrate. A method of making the ceramic circuit board is also disclosed.

1 . A ceramic circuit board for use in packaging an electronic element, comprising:
 a ceramic-copper plate including a ceramic substrate that has opposite first and second surfaces, and a through-hole formed through said first and second surfaces, a top copper pattern that overlies said first surface of said ceramic substrate and that has at least two conducting portions spaced apart from each other, and a bottom copper layer that underlies said second surface of said ceramic substrate; and   a heat-dissipating unit adapted for dissipating heat from the electronic element, and including a heat-dissipating layer that is disposed in said through-hole of said ceramic substrate above said bottom copper layer and that has a thermal conductivity larger than that of said ceramic substrate.   
     
     
         2 . The ceramic circuit board of  claim 1 , wherein said heat-dissipating unit further includes a ceramic layer that lies between said heat-dissipating layer and said bottom copper layer of said ceramic-copper plate, and that has a thickness ranging from 0.02 mm to 0.2 mm, a thickness of said ceramic substrate of said ceramic-copper plate being larger than 0.2 mm, the thermal conductivity of said heat-dissipating layer being larger than 170 Wm −1 K −1 . 
     
     
         3 . The ceramic circuit board of  claim 2 , wherein said heat-dissipating layer of said heat-dissipating unit is made of copper, said ceramic layer of said heat-dissipating unit being formed by a thermal spraying technique. 
     
     
         4 . The ceramic circuit board of  claim 2 , wherein said ceramic layer of said heat-dissipating unit and said bottom copper layer of said ceramic-copper plate are sinter-bonded to each other. 
     
     
         5 . The ceramic circuit board of  claim 1 , wherein said top copper pattern further has a gap that separates said two conducting portions and that completely exposes said through-hole of said ceramic substrate of said ceramic-copper plate. 
     
     
         6 . The ceramic circuit board of  claim 1 , wherein said top copper pattern further has a gap that separates said two conducting portions and that partially exposes said through-hole of said ceramic substrate of said ceramic-copper plate, one of said conducting portions of said top copper pattern contacting said heat-dissipating layer of said heat-dissipating unit. 
     
     
         7 . A method of making a ceramic circuit board for use in packaging an electronic element, comprising:
 (a) providing a ceramic-copper plate that includes top and bottom copper layers, a ceramic substrate between said top and bottom copper layers, and a through-hole formed in the ceramic substrate; and   (b) providing a heat-dissipating unit on the bottom copper layer and within the through-hole for dissipating heat from the electronic element.   
     
     
         8 . The method of  claim 7 , wherein the top copper layer is formed into a top copper pattern that has at least two conducting portions separated from each other. 
     
     
         9 . The method of  claim 8 , wherein the top and bottom copper layers are sinter-bonded to the ceramic substrate, and the heat-dissipating unit is sinter-bonded to the bottom copper layer. 
     
     
         10 . The method of  claim 7 , wherein step (a) includes:
 (a1) forming the through-hole that extends through first and second surfaces of the ceramic substrate;   (a2) sinter-bonding the top and bottom copper layers respectively to the first and second surfaces of the ceramic substrate after step (a1); and   (a3) patterning the top copper layer to form two conducting portions after step (a2); and   wherein, in step (b), the heat-dissipating unit is provided on the bottom copper layer in the through-hole of the ceramic substrate by a sinter-bonding process; and   wherein a gap between the two conducting portions exposes the through-hole entirely.   
     
     
         11 . The method of  claim 10 , wherein the heat-dissipating unit has a heat-dissipating layer with a thermal conductivity larger than that of the ceramic substrate, and a ceramic layer that underlies the heat-dissipating layer, the ceramic layer of the heat-dissipating unit being sinter-bonded to the bottom copper layer within the through-hole and having a thickness ranging from 0.02 mm to 0.2 mm, the ceramic substrate having a thickness larger than 0.2 mm, the thermal conductivity of the heat-dissipating layer of the heat-dissipating unit being larger than 170 Wm −1 K −1 . 
     
     
         12 . The method of  claim 11 , wherein the heat-dissipating layer of the heat-dissipating unit is made of copper, the ceramic layer of the heat-dissipating unit being formed by a thermal spraying technique. 
     
     
         13 . The method of  claim 7 , wherein step (a) includes:
 (a1) sinter-bonding the top copper layer to a first surface of the ceramic substrate;   (a2) patterning the top copper layer to form two conducting portions after step (a1);   (a3) forming the through-hole in the ceramic substrate after step (a2); and   (a4) sinter-bonding the bottom copper layer to a second surface of the ceramic substrate opposite to the first surface after step (a3); and   wherein, in step (b), the heat-dissipating unit is provided on the bottom copper layer in the through-hole of the ceramic substrate by a sinter-bonding process.   
     
     
         14 . The method of  claim 13 , wherein the heat-dissipating unit includes a heat-dissipating layer that has a thermal conductivity larger than that of the ceramic substrate, and a ceramic layer that underlies the heat-dissipating layer, the ceramic layer of the heat-dissipating unit being sinter-bonded to the bottom copper layer and having a thickness ranging from 0.02 mm to 0.2 mm, the ceramic substrate having a thickness larger than 0.2 mm, the thermal conductivity of the heat-dissipating layer of the heat-dissipating unit being larger than 170 Wm −1 K −1 . 
     
     
         15 . The method of  claim 11 , wherein the heat-dissipating layer of the heat-dissipating unit is made of copper, the ceramic layer of the heat-dissipating unit being formed by a thermal spraying technique. 
     
     
         16 . The method of  claim 7 , wherein step (a) includes:
 (a1) forming the through-hole extending through opposite first and second surfaces of the ceramic substrate;   (a2) sinter-bonding the top and bottom copper layers respectively to the first and second surfaces of the ceramic substrate after step (a1); and   (a3) patterning the top copper layer to form two conducting portions after step (a2); and   wherein, in step (b), the heat-dissipating unit is provided on the bottom copper layer in the through-hole of the ceramic substrate by a sinter-bonding process simultaneously with the sinter-bonding of the top and bottom copper layers to the ceramic substrate.   
     
     
         17 . The method of  claim 16 , wherein the heat-dissipating unit includes a heat-dissipating layer that has a thermal conductivity larger than that of the ceramic substrate, and a ceramic layer that underlies the heat-dissipating layer, the ceramic layer of the heat-dissipating unit being sinter-bonded to the bottom copper layer, the ceramic layer having a thickness ranging from 0.02 mm to 0.2 mm, the ceramic substrate having a thickness larger than 0.2 mm, the thermal conductivity of the heat-dissipating layer being larger than 170 Wm −1 K −1 . 
     
     
         18 . The method of  claim 17 , wherein the heat-dissipating layer of the heat-dissipating unit is made of copper, the ceramic layer of the heat-dissipating unit being formed by a thermal spraying technique.