Methods of making ceramic heaters with power terminals

1. A method of securing a terminal to a ceramic heater, the ceramic heater including a ceramic substrate and a resistive heating element, the method comprising:

forming a recess in the ceramic substrate to expose a portion of the resistive heating element, the recess defining an interior surface, the interior surface including a side surface defining a periphery of the recess and a bottom surface on which the resistive heating element is disposed;

applying a material on the side surface of the interior surface of the recess to form an intermediate layer, the material being in a form selected from a group consisting of a paste, a powder and a tape;

applying an active brazing material on at least one of the intermediate layer and the bottom surface; and

bonding the terminal to the intermediate layer by the active brazing material to electrically connect the terminal to the resistive heating element through the intermediate layer, a portion of the terminal being surrounded by the intermediate layer and the active brazing material.

2. The method according to claim 1 , wherein the material is applied on the entire interior surface of the recess.

3. The method according to claim 1 , wherein the material has a variable composition selected from a group consisting of molybdenum/aluminum nitride (Mo/AlN) and tungsten/aluminum nitride (W/AlN).

4. The method according to claim 1 , further comprising sintering the material to form the intermediate layer.

5. The method according to claim 4 , wherein the sintering step is performed at about 1700° C. to about 1950° C. for about 0.5 to about 10 hours.

6. The method according to claim 4 , further comprising machining the intermediate layer to a size that fits the terminal after the sintering step.

7. The method according to claim 1 , further comprising heating the active brazing material to about 950° C. to about 1100° C. and maintaining the temperature for about 5 to about 60 minutes.

8. The method according to claim 1 , further comprising applying a nickel coating on the terminal.

9. The method of claim 1 , further comprising drying the paste to form the intermediate layer.

10. The method of claim 9 , further comprising sintering the intermediate layer and the ceramic substrate to form a sintered ceramic substrate.

11. The method of claim 1 , further comprising drying the active brazing material.

12. The method of claim 1 , wherein the material has a coefficient of thermal expansion between that of the ceramic substrate and that of the active brazing material and has higher mechanical strength and fracture toughness than that of the ceramic substrate over the range of operating temperatures of the ceramic heater.

13. A method of securing a terminal to a ceramic heater including a ceramic substrate and a resistive heating element, the method comprising:

forming a recess in the ceramic substrate to expose a portion of the resistive heating element, the recess defining an interior surface, the interior surface including a side surface defining a periphery of the recess and a bottom surface on which the resistive heating element is disposed;

forming an intermediate layer in a form of paste on the side surface of the interior surface and the portion of the resistive heating element, the intermediate layer being selected from a group consisting of Mo/AlN and W/AlN;

sintering the intermediate layer, the resistive heating element, and the ceramic substrate;

adjusting the intermediate layer to a size for receiving the terminal;

applying an active brazing material on at least one of the intermediate layer and the bottom surface;

placing the terminal within the recess, a portion of the terminal being surrounded by the intermediate layer and the active brazing material; and

heating the active brazing material under vacuum, thereby bonding the terminal to the intermediate layer.

14. A method of securing a terminal to a ceramic heater, the ceramic heater including a ceramic substrate and a resistive heating element, the method comprising:

sintering a material in a recess of the ceramic substrate at least on a side surface of the recess that defines a periphery of the recess to form an intermediate layer;

applying an active brazing material on the intermediate layer; and

bonding the terminal to the intermediate layer to electrically connect the terminal to the resistive heating element through the intermediate layer, wherein a portion of the terminal is surrounded by the intermediate layer and the active brazing material.

15. The method of claim 14 , further comprising applying the active brazing material in the form of a paste on the intermediate layer.

16. The method of claim 15 , further comprising drying the active brazing material to bond the terminal to the intermediate layer.

17. The method of claim 15 , wherein the intermediate layer has a variable composition selected from a group consisting of molybdenum/aluminum nitride (Mo/AlN) and tungsten/aluminum nitride (W/AlN), and has a coefficient of thermal expansion between that of the ceramic substrate and that of the active brazing material and has higher mechanical strength and fracture toughness than that of the ceramic substrate over the range of operating temperatures of the ceramic heater.