A new bonding technique of copper and SiC ceramics having high thermal conductivity was developed, and thermal characteristics of the bonded elements were evaluated.
SiC ceramics used in the experiments were hotpress-sintered material containing a small amount of BeO. It has high thermal conductivity (270W/m·k) and also high electrical resistivity (1013Ω·cm or above).
It was concluded from this study that,
(1) 50 mm×50 mm square SiC blocks were successfully bonded to copper blocks within 20 second without cracking by using both Cu-35wt%Mn foil as a brazing material and the copper-35vol% carbon fiber composite material of 2 mm in thickness as the compliant material to relieve the thermal stress.
(2) Manganese silicides (Mn6Si) and manganese carbides (Mn23C6) were observed in the SiC/Cu bonded zone by using Cu-35wt% Mn brazing foil.
(3) Peel strength between a SiC block and 100μm thick copper foil was above 2 kgf/mm and fracture occurred in copper foil.
(4) Tensile strength of a bonded element of SiC block/Cu-35vol% carbon fiber compliant material/ copper block was about 2 kgf/mm2. Fracture occurred in the composite material. The element can be heat resistant and used up to 300°C.
(5) Thermal reliability of the bonded element (using a 35 mm square SiC block) was evaluated by normal thermal cycle test and rapid thermal cycle test using a 1.5 MW splash test machine. Maximu allowable heat fluxes were about 500 W/cm2 and 400 W/cm2 respectively.
