Circuit substrate

Abstract

A circuit substrate which has a ceramic substrate and an Al circuit comprising Al or an Al alloy bonded to said ceramic substrate via a layer comprising Al and Cu.

What is claimed is:  
     
         1 . A circuit substrate which has a ceramic substrate and an Al circuit comprising Al or an Al alloy bonded to said ceramic substrate via a layer comprising Al and Cu.  
     
     
         2 . The circuit substrate according to  claim 1 , wherein the ceramic substrate is an aluminum nitride substrate or a silicon nitride substrate.  
     
     
         3 . The circuit substrate according to  claim 1 , wherein the ceramic substrate is an aluminum nitride substrate having a thermal conductivity of at least 130 W/mK and having such a X-ray diffraction peak intensity ratio that 2≦Y 2 O 3 .Al 2 O 3 ×100/AlN≦17 and 2Y 2 O 3 .Al 2 O 3 ×100/AlN≦2 on the surface.  
     
     
         4 . The circuit substrate according to  claim 1 , wherein the Al circuit comprising Al or an Al alloy is formed by using Al having a purity of at least 99.85 wt %.  
     
     
         5 . The circuit substrate according to  claim 1 , wherein the Al circuit comprising Al or an Al alloy is formed by using a rolled Al having a purity of at least 99.99 wt %.  
     
     
         6 . The circuit substrate according to  claim 1 , wherein the proportion of Cu in the layer comprising Al and Cu is from 1 to 6 wt %.  
     
     
         7 . The circuit substrate according to  claim 1 , wherein the Al circuit comprising Al or an Al alloy has a thickness of at least 100 μm and a Vickers hardness of at most 15 kgf /mm 2 .  
     
     
         8 . The circuit substrate according to  claim 1 , which has a heat-radiating plate comprising Al or an Al alloy formed on the ceramic substrate on the side (back side) opposite to the side on which the Al circuit is formed.  
     
     
         9 . The circuit substrate according to  claim 8 , wherein the volume ratio of the Al circuit to the heat-radiating plate is from 0.80 to 1.2.  
     
     
         10 . The circuit substrate according to  claim 8 , wherein the Al circuit has a Vickers hardness of at most 16 kgf /mm 2 , and the heat-radiating plate has a Vickers hardness of from 19 to 30 kgf/mm 2 .  
     
     
         11 . A circuit substrate which has a ceramic substrate and an Al circuit comprising Al or an Al alloy bonded to said ceramic substrate by using, as a bonding material, an Al—Cu type alloy or a mixture containing Al and Cu.  
     
     
         12 . The circuit substrate according to  claim 11 , wherein the bonding material is an Al—Cu type alloy foil.  
     
     
         13 . The circuit substrate according to  claim 11 , wherein the ceramic substrate is an aluminum nitride substrate or a silicon nitride substrate.  
     
     
         14 . The circuit substrate according to  claim 11 , wherein the ceramic substrate is an aluminum nitride substrate having a thermal conductivity of at least 130 W/mK and having such a X-ray diffraction peak intensity ratio that 2≦Y 2 O 3 .Al 2 O 3 ×100/AlN≦17 and 2Y 2 O 3 .Al 2 O 3 ×100/AlN≦2 on the surface.  
     
     
         15 . The circuit substrate according to  claim 11 , wherein the Al circuit comprising Al or an Al alloy is formed by using Al having a purity of at least 99.85 wt %.  
     
     
         16 . The circuit substrate according to  claim 11 , wherein the Al circuit comprising Al or an Al alloy is formed by using a rolled Al having a purity of at least 99.99 wt %.  
     
     
         17 . The circuit substrate according to  claim 11 , wherein the bonding material comprises at least 86 wt % of Al, from 1 to 6 wt % of Cu and at most 3 wt % of Mg (not including 0).  
     
     
         18 . The circuit substrate according to  claim 11 , wherein the Al circuit comprising Al or an Al alloy has a thickness of at least 100 μm and a Vickers hardness of at most 15 kgf/mm 2 .  
     
     
         19 . The circuit substrate according to  claim 11 , which has a heat-radiating plate comprising Al or an Al alloy formed on the ceramic substrate on the side (back side) opposite to the side on which the Al circuit is formed.  
     
     
         20 . The circuit substrate according to  claim 19 , wherein the volume ratio of the Al circuit to the heat-radiating plate is from 0.80 to 1.2.  
     
     
         21 . The circuit substrate according to  claim 19 , wherein the Al circuit has a Vickers hardness of at most 16 kgf/mm 2 , and the heat-radiating plate has a Vickers hardness of from 19 to 30 kgf/mm 2 .  
     
     
         22 . A process for producing a circuit substrate, which comprises disposing an Al or Al alloy plate, pattern or both on a ceramic substrate by means of, as a bonding material, an Al—Cu type alloy or a mixture containing Al and Cu, and heating the resulting assembly at a temperature of from 540 to 640° C. while applying a pressure of from 1 to 100 kgf/cm 2  thereto in a direction perpendicular to the ceramic substrate to bond the Al or Al alloy plate, pattern or both to the ceramic substrate, followed by etching as the case requires.  
     
     
         23 . The process for producing a circuit substrate according to  claim 22 , wherein the bonding material is an Al—Cu type alloy foil.  
     
     
         24 . The process for producing a circuit substrate according to  claim 23 , wherein the bonding material is an Al—Cu type alloy foil having a thickness of from 15 to 35 μm, the Al or Al alloy plate, pattern or both, having a thickness of at least 100 μm, is disposed on either side of the ceramic substrate by means of said bonding material, and the resulting assembly is held under heating at a temperature of at least 590° C. for at least 20 minutes while applying a pressure of from 8 to 50 kgf/cm 2  thereto in a direction perpendicular to the ceramic substrate.  
     
     
         25 . The process for producing a circuit substrate according to  claim 23 , wherein the Al—Cu type alloy foil is an Al—Cu—Mg type alloy foil comprising at least 86 wt % of Al, from 1 to 6 wt % of Cu and at most 3 wt % of Mg (not including 0).  
     
     
         26 . The process for producing a circuit substrate according to  claim 24 , wherein the Al—Cu type alloy foil is an Al—Cu—Mg type alloy foil comprising at least 86 wt % of Al, from 1 to 6 wt % of Cu and at most 3 wt % of Mg (not including 0).