Method for forming metallized layer on an aluminum nitride sintered body

A method of increasing the peel strength between a metallized layer and a surface of an aluminum nitride sintered body, comprising the steps of:

• (a) forming and sintering an aluminum nitride body to provide a sintered aluminum nitride body;
• (b) preparing a metal paste of tungsten and oxide components including at least SiO.sub.2, CaO, and Al.sub.2 O.sub.3 present in said metal paste within the range of at least 10 percent by weight and not more than 40 percent by weight of said metal paste, said oxide components including said SiO.sub.2 in a content of at least 1 percent by weight and not more than 30 percent by weight of said oxide components, said CaO being present in a weight ratio of at least 0.5 and not more than 2.0 relative to said Al.sub.2 O.sub.3 ;
• (c) applying said metal paste onto said surface of said aluminum nitride sintered body;
• and
• (d) firing said aluminum nitride sintered body coated with said metal paste in a non-oxidizing atmosphere at a temperature of at least 1500.degree. C. and less than 1600.degree. C., whereby said peel strength between said metallized layer and said aluminum nitride sintered body is at least 1.47 kg/mm.sup.2.