US Patent 7345260 Heater and method of manufacturing the same

A heater including a plate-shaped substrate having a heating surface for heating an object and a heater element provided in the substrate or on its surface. A central axis C2 of a circumscribed circle of the heater element and a central axis C1 of the substrate are not on the same axis and a gap exists between the axes. When manufacturing the heater, a central axis C1 of a resistant heater is specified, thermal uniformity of the heating surface of a preliminary substrate is evaluated, and a central axis C2 of the substrate is specified. The central axis C2 is specified at a position where the thermal uniformity of the heating surface is superior to a case where the central axis C2 of the substrate is located on the central axis C1. Then a substrate having the central axis C2 is formed by subjecting the preliminary substrate to grinding processing.