IS21.3 - Ceramics Substrates for Next Generation Heat Dissipation from Electric Devices

This paper will provide the ceramics substrates for heat dissipation from electric devices such as power electronics, high-speed communications and so on. Ceramics substrates such as Alumina and Silicon Nitride are currently used as circuit substrates and heat dissipation board because of having high insulation property, thermal stability and thermal conductivity. Recently, the devices are needed in the cutting-edge industrial area which can apply to higher power conversion and higher speed communication, therefore heat dissipation substrates are required much higher performances. In this review, aluminum nitride (AlN) substrates having high mechanical strength with high thermal conductivity and diamond-nickel substrates having extremely high thermal conductivity are introduced.

AlN has been already used for the heat dissipation substrates of optical devices such as LED and LD. It is expected to use for power electronics however the low fracture strength is issued to decrease the mechanical reliability for the devices. In the usage of thermal dissipation substrate for power electronics, copper bases are combined on both sides of AlN substrates by active metal brazing. The thermal expansion deference between aluminum AlN substrates and cupper bases causes mechanical stress during thermal cycles and the stress causes cracks into the substrates. In this work, the high fracture strength was achieved by adding AlN fibers to AlN substrate matrix. Fiber rein-forced AlN substrates achieved same value of fracture strength as silicon nitride substrates which have already applied to power electric devices for various industrial machines and automotives as thermal dissipation substrates. Additionally, thermal conductivity of fiber rein-forced AlN substrates was same as conventional AlN substrates.
Diamond that has extremely high thermal conductivity (1,000-2,000W/(m・K)) is expected as a material for heat-dissipation substrates. However, lots of cost and longer processing time is required in order to produce the large size of diamond substrates. Therefore, it is very important to innovate new processes to produce the large size diamond substrates in an inexpensive method. In this work, it was successfully developed to produce large size diamond-nickel heat dissipation substrates with high thermal conductivity by closely packed single layered diamond particles were combined with high density by nickel plating method. Diamond-nicked substrates in this work showed extremely high thermal conductivity of 1,200 W/(m・K). The diamonds are densely bonded with nickel using a unique plating technology that was cultivated through manufacturing of griding tools of NORITAKE.