Patent ID: 8343617

Claim:
A ceramic substrate, comprising: a ceramic main body; and a planar buffer layer on the ceramic main body, wherein the relationship between the coefficient of thermal expansion of the ceramic main body CTEm and the coefficient of thermal expansion of the planar buffer layer CTEp is represented by the following equation: |CTEm−CTEp|≦3×10 −6 /° C., wherein a softening point of the ceramic main body is more than 800° C. and a softening point of the planar buffer layer is more than 700° C., wherein the planar buffer layer consists of: 30-75 parts by weight of SiO 2 ; 5-40 parts by weight of Al 2 O 3 ; 0-35 parts by weight of B 2 O 3 , P 2 O 5 alkaline earth metal oxide, or combinations thereof; and 25-46 parts by weight of ZrO 2 , Y 2 O 3 , WO x , SnO 2 , GeO 2 , or combinations thereof, wherein x is 2 or 3.