Making an aluminum nitride heater
A method of making a heater includes an aluminum nitride base having equal to or less than 1% impurities, particularly one embodiment having none of polybrominated biphenyl, polybrominated diphenyl ether, hexabromocyclododecane, polyvinyl chloride, chlorinated paraffin, phthalate, cadmium, hexavalent chromium, lead, and mercury. The base is fired in a heating unit before any layering. Thereafter, on a topside and backside of the base a conductor layer is layered and allowed to settle and dry before firing. Next, a resistive layer is layered on the base from a resistor paste such that the resistive layer connects to the conductor layer on the topside. The resistor paste is allowed to settle and dry and then the base with the conductor and resistor layers is fired. At least four layers of glass are layered next over the resistive layer, each instance thereof including layering a glass, drying the glass and firing.
1. A method of making a heater, comprising:
on an aluminum nitride base having equal to or less than 1% impurities, firing the base before layering any layers on the base;
layering on a topside and backside of the base a conductor layer from a conductive paste and letting dry the conductor layer on each side of the base;
firing the base having the conductor layers on each side of the base;
layering a resistive layer from a resistor paste on the base such that the resistive layer connects to the conductor layer on the topside of the base and letting dry the resistive layer;
firing the base having the resistive layer and the conductor layers on each side of the base; and
layering at least four layers of glass over the resistive layer, each instance of said layering the at least four layers of glass including layering a glass, drying the glass and firing the base including the glass said layered.
2. The method of claim 1 , wherein the layering the glass includes layering two consecutive layers of a glass having a solid content of 65% or more and a viscosity of 100 Pa·s or less.
3. The method of claim 1 , wherein each instance of firing the base for the conductor and resistive layers includes heating a heating unit having the base therein to a first peak temperature of about 850° C. and for said each instance of said firing the base including the glass heating the heating unit having the base therein to a second peak temperature of about 830° C., each instance of the heating at one of the first and second peak temperatures occurring for at least 5 minutes.
4. The method of claim 1 , further including letting settle the conductor and resistive pastes before said letting dry the conductor and resistive layers, the letting settle including a period of time of about 5 to about 10 minutes at about 20° C. to about 25° C.
5. The method of claim 1 , wherein each instance of said letting dry the conductor and resistive layers further includes drying in a drying unit for a period of time of about 30 total minutes at a temperature profile of the drying unit having the base therein beginning at about 25° C. and ramping up to about 80° C. for about 10 minutes, ramping up again to about 160° C. for about 10 minutes and cooling down to below 50° C.
6. The method of claim 1 , further including providing a mesh stencil for each instance of said layering.
7. The method of claim 6 , further including leveling through the mesh stencil the conductor and resistor pastes and the glass.
8. The method of claim 1 , further including oxidizing a surface of the aluminum nitride base or plasma treating the surface before said firing the base before said layering any layers on the base.