Patent ID: 7662736

Claim:
A substrate comprising a high thermal conductive aluminum nitride sintered body having: a thermal conductivity of 220 W/m·K or more; and a three point bending strength of 250 MPa or more; wherein a ratio (I Al 2 Y 4 O 9 /I AlN ) of X-ray diffraction intensity (I Al 2 Y 4 O 9 ) of Al 2 Y 4 O 9 (201 plane) with respect to X-ray diffraction intensity (I AlN ) of aluminum nitride (101 plane) is 0.002 to 0.03, and said aluminum nitride sintered body comprises 0.14-1.5 mass % of Y element and 0.05-0.5 mass % of oxygen, a mass ratio (O/Y) of oxygen (O) with respect to Y element is 0.5 or less, an average diameter of aluminum nitride crystal grains is 4 μm or more, a number of crystal grains existing in arbitrary crystal structure area of 100 μm×100 μm is 200 or less, and a maximum diameter of grain boundary phase is 0.5 μm or less.