▎ 摘　　要

NOVELTY - Indirect braze welding of aluminum nitride ceramic copper-clad plate involves ultrasonically cleaning aluminum nitride ceramic substrate in alcohol or acetone for 20-30 minutes; drying and pickling with 10-15 wt.% sulfuric acid for 5-10 minutes; ultrasonically cleaning in alcohol or acetone for 20-30 minutes; drying to obtain pretreated ceramic substrate; uniformly mixing silver powder, copper powder, copper-plated low-expansion ceramic powder and copper-plated graphene powder to prepare composite solder; adding composite solder with 5-20 wt.% organic binder; uniformly stirring to obtain composite solder slurry; depositing active metal elements on surface of pretreated ceramic substrate via vacuum magnetron sputtering or ion plating; applying composite solder on surface ceramic substrate; applying composite solder slurry to ceramic substrate; compounding two surfaces of substrate with oxygen-free copper sheet; drying; and subjecting to vacuum furnace brazing. USE - The method is used for indirect braze welding of aluminum nitride ceramic copper-clad plate. ADVANTAGE - The method introduces ceramic particles with low expansion coefficient into brazing filler metal to make thermal expansion coefficient gradient transition of joint, thus reducing residual stress level of joint. It introduces graphene with high thermal conductivity and high strength into composite brazing material, which can increase strength of brazing material and improve its thermal conductivity. DETAILED DESCRIPTION - Indirect braze welding of aluminum nitride ceramic copper-clad plate comprises ultrasonically cleaning aluminum nitride ceramic substrate in alcohol or acetone for 20-30 minutes to remove surface oil; drying and pickling with 10-15 wt.% sulfuric acid for 5-10 minutes to remove surface oxide film; ultrasonically cleaning in alcohol or acetone for 20-30 minutes; drying to obtain pretreated ceramic substrate; uniformly mixing silver powder, copper powder, copper-plated low-expansion ceramic powder and copper-plated graphene powder to prepare composite solder; adding composite solder with 5-20 wt.% organic binder; uniformly stirring to obtain composite solder slurry; depositing active metal elements consisting of titanium, zirconium, hafnium, or chromium on surface of pretreated ceramic substrate via vacuum magnetron sputtering or ion plating; applying composite solder on surface ceramic substrate deposited with active metal elements; applying composite solder slurry to ceramic substrate; compounding two surfaces of substrate with oxygen-free copper sheet to obtain oxygen-free copper sheet/composite solder/active metal element/aluminum nitride/active metal element/composite solder/oxygen-free copper sheet assembly; drying assembly in vacuum drying box at 50-100 degrees C for 20-60 minutes to remove organic binder; putting dried assembly into vacuum furnace for brazing under vacuum degree of 1x 10-2 to 1x 10-4 Pa to obtain aluminum nitride ceramic copper-clad plate. DESCRIPTION OF DRAWING(S) - The drawing shows a schematic diagram of aluminum nitride ceramic copper-clad plate assembled structure (Drawing includes non-English language text).