| 摘要 |
PROBLEM TO BE SOLVED: To obtain Mg or Ca borate particles having high thermal conductivity, large electric insulating property and excellent heat radiating property by coating the particles with hexagonal boron nitride. SOLUTION: A mixture of melamine, boric acid and inorg. compds. selected from hydroxides and carbonates of Mg and Ca is used as the starting material. The compsn. of the mixture ranges in the area in the ternary compsn. diagram by molar percentages defined by lines connecting the points A(35, 60, 5), B(25, 70, 5), C(5, 80, 15) and D(5, 5, 90). The source material mixed in a ball mill or the like is kept in an atmosphere at 40 to 100 deg.C and >5% relative humidity for 1 to 100 hours to produce a mixture containing melamine borate and hydroxides and/or carbonates of Mg and/or Ca. The mixture is compacted under pressure preferably of <=100 kgf/cm2, and calcined in a nonoxidizing atmosphere such as nitrogen at 1,700 to 2,000 deg.C for 2 to 10 hours to obtain mixture powder containing hBN-coated borate particles and boron nitride particles. The obtd. powder is suitable as a filler for a heat radiating member of electronic parts.
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