Heater
A heater comprising a ceramic heater element and at least two fins for dissipating heat from the ceramic heater element, wherein the ceramic heater element extends along a plane in one dimension and the at least two fins extend away from the plane, and wherein the at least two fins are connected to the ceramic heater element via discrete connecting portions.
1. A heater comprising a ceramic heater element that comprises a ceramic substrate and at least two fins for dissipating heat from the ceramic heater element, wherein the ceramic substrate extends along a plane in one dimension and the at least two fins extend away from the plane, and wherein each fin of the at least two fins is connected to the ceramic substrate along a length of the fin via discrete connecting portions of the fin such that the fin is not connected to the ceramic substrate along an entire length of the fin, wherein the discrete connecting portions are a plurality of uniform areas of contact between the ceramic substrate and the at least two fins.
2. The heater of claim 1 , wherein the discrete connecting portions are each separated by a gap.
3. The heater of claim 2 , wherein the fin has a thickness and the gap is between 0.8 and 1.2 times the fin thickness.
4. The heater of claim 1 , wherein the at least two fins are disposed on each side of the ceramic heater element.
5. The heater of claim 1 , wherein the heater comprises a plurality of fins extending from both sides of the ceramic heater element.
6. The heater of claim 5 , wherein the plurality of fins vary in height from a first edge to a second edge of the plurality of fins.
7. A method of attaching a metal fin to a ceramic heater element, the method comprising:
(a) applying a filler material to a ceramic surface of the ceramic heater element;
(b) positioning a metal fin over the filler material to produce a heater template; and
(c) brazing the heater template in a furnace at a temperature of between 750° C. and 900° C. to melt the filler and cause the filler and the ceramic surface of the ceramic heater element to react together.
8. The method of claim 7 , wherein the fin is made from one of copper, stainless steel, and kovar.
9. The method of claim 7 , further comprising:
(i) coating the ceramic surface of the ceramic heater element with a metallisation paste;
(ii) sintering the coated ceramic heater element;
(iii) electroless plating of a nickel layer on the sintered coated ceramic heater element to produce a primary metallised surface; and
(iv) applying a flux to the primary metallised surface, wherein steps (i) to (iv) are carried out prior to step (a) and wherein step (c) additionally melts the flux located between the metal fin and the primary metallised surface and is carried out at a temperature of around 600° C.
10. The method of claim 9 , wherein the metallisation paste is a mixture of the ceramic material used to form the ceramic heater element and a refractory material.
11. The method of claim 10 , wherein the metallisation paste is applied to the ceramic heater element at a thickness of 10 to 12 microns.