In recent years, electronic devices have been used in each of which an electronic component that may be of various types is mounted on a circuit member of a heat dissipation base, examples of the component including semiconductor elements such as an insulating gate bipolar transistor (IGBT) element, a metal oxide semiconductor field effect transistor (MOSFET) element, a light emitting diode (LED) element, a freewheeling diode (FWD) element and a giant transistor (GTR) element, a sublimation-type thermal printer head element, and a thermal ink-jet printer head element.
As the heat dissipation base, on which a circuit member on which an electronic component is to be mounted is set up, there is used a heat dissipation base wherein a copper plate is joined, as a circuit member, to one of the main surfaces of a ceramic substrate and further a copper plate is joined, as a heat dissipation member good in heat dissipating property, to the other main surface. For joining the ceramic substrate to the circuit member and the heat dissipation member, a brazing material is used.
For this reason, the brazing material, which is used to join the circuit member and the heat dissipation member to the ceramic substrate, is required to have a high joining strength. The heat dissipation base, wherein the circuit member and the heat dissipation member are joined to the ceramic substrate through a joining layer made of the brazing material, is required to have an excellent heat dissipation property, and a high reliability that permits the base to be used for a long term.
As such a heat dissipation base, for example, Patent Literature 1 suggests a ceramic circuit board wherein metal circuit plates are joined to a ceramic substrate through a silver-copper based brazing material layer containing carbon powder and at least one active metal selected from Ti, Zr, Hf and Nb. Additionally, it is stated that when at least one element selected from In, Zn, Cd and Sn is further incorporated into the silver-copper based brazing material layer, the melting point of the brazing material is made low to lower the temperature for joining the metal circuit plates.