Patent ID: 8362400

Claim:
A ceramic joining unit, comprising: a ceramic base member having a leading end side and a rear end side, said ceramic base member extending in a longitudinal direction; an electrode pad formed of at least one of tungsten and molybdenum, as a main component thereof, provided on a surface of the ceramic base member; a coupling terminal for electrical connection to an external circuit; and a joining portion which joins the electrode pad to the coupling terminal by means of a solder joint, wherein the electrode pad includes: a first layer in contact with the ceramic base member; and a second layer having an upper surface and a bottom surface, the bottom surface of the second layer being laminated on an upper surface of the first layer and in contact with the joining portion, wherein each of the first layer and the second layer contains a ceramic material as a main component among ceramic materials forming the ceramic base member, a content (wt %) of the ceramic material in the first layer is greater than a content (wt %) of ceramic material in the second layer, and a contour of the upper surface of the first layer is located outside of a contour of the bottom surface of the second layer at an entire periphery of the first layer.