Bonded metal and ceramic plates for thermal management of optical and electronic devices
View Patent ↗A ceramic assembly includes one or more electrically and thermally conductive pads to be thermally coupled to a heat generating device, each conductive pad is electrically isolated from each other. The ceramic assembly includes a ceramic layer to provide this electrical isolation. The ceramic layer has high thermal conductivity and high electrical resistivity. A top surface and a bottom surface of the ceramic layer are each bonded to a conductive layer, such as copper, using an intermediate joining material. A brazing process is performed to bond the ceramic layer to the conductive layer via a joining layer. The joining layer is a composite of the joining material, the ceramic layer, and the conductive layer. The top conductive layer and the joining layer are etched to form the electrically isolated conductive pads. The conductive layers are bonded to the ceramic layer using a bare ceramic approach or a metallized ceramic approach.
1. A device comprising:
a. a first copper layer;
b. a ceramic layer;
c. a second copper layer;
d. a first active brazing alloy layer bonded between the first copper layer and the ceramic layer to form a first joining layer, wherein the first copper layer and the first joining layer are configured to form a plurality of electrically isolated conductive pads, wherein each of the plurality of electrically isolated pads includes an etched wall extending from a first surface of the first copper layer through the first copper layer and the first joining layer to a first surface of the ceramic layer, the first surface of the first copper layer is distal from the first joining layer, and the first surface of the ceramic layer is proximate to the first joining layer, further wherein a slope of the etched wall through the first joining layer is steeper than a slope of the etched wall through the first copper layer; and
e. a second active brazing alloy layer bonded between the ceramic layer and the second copper layer to form a second joining layer.
2. The device of claim 1 wherein the first copper layer and the first joining layer are etched to form a plurality of electrically isolated conductive pads, further wherein each of the plurality of electrically isolated pads are electrically isolated from each other and from the second copper layer by the ceramic layer.
3. The device of claim 1 wherein the ceramic layer comprises beryllium oxide, aluminum oxide, or aluminum nitride.
4. The device of claim 1 wherein the first active brazing alloy layer and the second active brazing alloy layer comprise a copper-based active brazing alloy, a copper-silver-based active brazing alloy, or an indium-copper-silver-based active brazing alloy.
5. The device of claim 1 wherein the first active brazing alloy layer is comprised of an active joining material paste and the second active brazing alloy layer is comprised of the active joining material paste, or the first active brazing alloy layer is comprised of an active joining material foil and the second active brazing alloy layer is comprised of the active joining material foil.