Exothermic activation for high vacuum packaging
View Patent ↗An approach to obtain localized heat within a sealed vacuum cavity is disclosed. The approach uses an exothermic reaction between two reactants to generate heat in the vicinity of a structure, such as a getter material or a bondline that is heat activated. The exothermic reaction can be initiated by application of laser light, or application of current to a current-carrying conductor in the vicinity of the reactants.
1. A device, comprising:
a first layer of a first reactant formed on a first substrate;
a second layer of a second product material which includes at least a portion of the first reactant and a second reactant, wherein the first reactant is exothermically reactive with the second reactant to form the second product material;
a third layer of a third, activated material formed over the second material; and
a microdevice formed on the first substrate or a second substrate, the microdevice being encapsulated in a device cavity defined by the first substrate and the second substrate, wherein the third material alters the environment surrounding the device inside the device cavity.
2. The device of claim 1 , wherein the first reactant comprises aluminum.
3. The device of claim 1 , wherein the second product material comprises alumina.
4. The device of claim 2 , wherein the third, activated material comprises at least one of a hermetic adhesive material and a getter material.
5. The device of claim 1 , further comprising:
a second cavity disposed in the substrate below the first layer of the first reactant, wherein the cavity is devoid of solid material under a substantial portion of the first layer of the first reactant.
6. The device of claim 4 , wherein the adhesive material comprises a metal alloy containing at least two elemental metals in an alloy.
7. The device of claim 6 , wherein that at least two metals comprises gold (Au) and indium (In), in a stoichiometry of AuIn x , wherein x is about 2.
8. The device of claim 6 , further comprising:
a second cavity disposed in the substrate under the first layer of the first reactant, wherein the cavity is devoid of solid material under a substantial portion of a surface of the first layer, and wherein the second cavity is in fluid communication with the device cavity.
9. The device of claim 4 , further comprising an activation layer disposed underneath the first layer of the first reactant, which applies heats to the first reactant and the second reactant to initiate an exothermic reaction.
10. The device of claim 4 , further comprising a current-carrying conductor disposed beneath the first layer, wherein one portion of the current-carrying conductor has a larger lateral dimension than a smaller, adjacent portion of the current-carrying conductor, and further having a choke point between the larger portion and the smaller portion.
11. The device of claim 1 , further comprising an activation layer formed beneath the first layer of the first reactant, wherein the activation layer has two contiguous regions, and a lateral extent of one region is greater than a lateral extent of an adjacent region, and wherein the activation layer comprises at least one of a magnetically permeable material and a current-carrying conductor material.