A manufacturing method of a high-thermal conductive silicon nitride substrate

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PROBLEM TO BE SOLVED : To provide a high-thermal conductive silicon nitride substrate suitable for a substrate for a power module by manufacturing a silicon nitride sintered compact having both of excellent mechanical characteristics and high thermal conductivity using low grade silicon powder containing a large quantity of impurity oxygen as a starting raw material and using a conventional forming and firing process. SOLUTION : A plate-like silicon nitride sintered compact is obtained by mixing 0.5-7 mol% oxide of a rare earth element and 1-7 mol% magnesium mixture with silicon powder in the ratio when silicon is expressed by a value expressed in terms of silicon nitride so that total of the impurity oxygen contained in the silicon powder and oxygen originating from the magnesium compound becomes 0.1-1.8 mass%, forming and nitriding the mixture, heating the resultant nitride in ≥0.1 MPa nitrogen atmosphere to densify it so as to have ≥95% relative density. A metallic plate is joined to at least one surface of the resultant plate-like silicon nitride sintered compact with a brazing filler metal containing at least one kind of magnesium, titanium and zirconium. COPYRIGHT : (C)2007, JPO&INPIT