Methods of fabricating vacuum housings with hermetic solder seals using capillary solder wicks
Hermetically sealed electronic devices and methods for fabricating the hermetically sealed electronic devices are provided. The devices include a solder sealed vacuum housing. The solder seal is formed using a solder wick having an external solder reservoir. When the reservoir is filled with molten solder, the solder is drawn via capillary action into a precisely defined narrow gap between two components of the housing where it forms an airtight and vacuum-tight seal.
1. A hermetically sealed electronic device comprising:
an electronic device hermetically sealed within a volume of a vacuum housing, the vacuum housing comprising:
a cover having an external surface and a vacuum surface;
a base having an external surface and a vacuum surface;
a sidewall that separates the cover from the base, the sidewall having a vacuum surface and an external surface and comprising one or more sidewall segments, wherein the vacuum surfaces of the cover, the base, and the sidewall enclose the vacuum volume;
at least one spacer, the at least one spacer defining a gap between a first housing component and a second housing component, the first and second housing components comprising: the sidewall and the cover; the sidewall and the base; or two sidewall segments;
a hermetic solder seal formed in the gap, wherein the hermetic solder seal joins a sealing surface of the first housing component to a sealing surface of the second housing component; and
a solder wick extending from the external surface of the sidewall at least partially into the gap, the solder wick comprising a reservoir external to the gap, but in capillary communication with the gap.
2. The device of claim 1 , wherein the cover is a window comprising a material that is transparent to electromagnetic radiation having wavelengths in at least one of the visible, infrared, and ultraviolet regions of the electromagnetic spectrum.
3. The device of claim 2 , wherein the first housing component is the window and the second housing component is the sidewall.
4. The device of claim 1 , wherein the sealing surface of the first housing component, the sealing surface of the second housing component, or the sealing surfaces of both the first and the second housing components comprise a metal layer that is wettable by the solder of the solder seal.
5. The device of claim 4 , wherein the metal layer comprises a tie metal sublayer adjacent to a passivation metal sublayer.
6. The device of claim 1 , wherein the cover, the base, and the sidewall are constructed from ultra-high vacuum compatible materials.
7. The device of claim 6 , wherein the ultra-high vacuum compatible materials are metals, glasses, or ceramics.
8. The device of claim 1 , wherein the spacer is an integral part of the first housing component or the second housing component.
9. The device of claim 1 , wherein the spacer is an integral part of the solder wick.
10. The device of claim 1 , further comprising a voltage source that is external to the vacuum housing and in electrical communication with the solder wick.
11. The device of claim 10 , wherein the solder wick provides an electrical connection between the voltage source and an electrical component of the electronic device.
12. The device of claim 1 , wherein the electronic device is a radiation detector.
13. The device of claim 12 , wherein the solder wick provides an electrical connection between the voltage source and an electrical component of the electronic device, and the electrical component comprises an electrical grid, a mesh, a foil, a wire plane, a dynode, and/or a secondary emitting layer.
14. The device of claim 10 , wherein the solder wick provides an electrical connection between the voltage source and the vacuum surface of the cover, the vacuum surface of the base, and/or the vacuum surface of the sidewall.
15. The device of claim 1 , further comprising a heat source that is external to the vacuum housing and in thermal communication with the solder wick.
16. A method of forming a hermetically sealed electronic device, the method comprising:
placing an electronic device in an unsealed vacuum housing, the vacuum housing comprising:
a cover having an external surface and a vacuum surface;
a base having an external surface and a vacuum surface;
a sidewall that separates the cover from the base, the sidewall having a vacuum surface and an external surface and comprising one or more sidewall segments, wherein the vacuum surfaces of the cover, the base, and the sidewall enclose the vacuum volume; and
at least one spacer, the at least one spacer defining a gap between a first housing component and a second housing component, the first and second housing components comprising: the sidewall and the cover; the sidewall and the base; or two sidewall segments;
inserting a solder wick comprising a solder reservoir partially into the gap, such that the solder reservoir is external to the external surface of the sidewall;
melting solder in the solder reservoir, wherein the melted solder is drawn into the gap by capillary action and forms a hermetic solder seal between a sealing surface of the first housing component and a sealing surface of the second housing component, thereby sealing the vacuum housing; and
evacuating the vacuum volume of the sealed vacuum housing to a pressure below atmospheric pressure.
17. The method of claim 16 , wherein the cover is a window comprising a material that is transparent to electromagnetic radiation having wavelengths in at least one of the visible, infrared, and ultraviolet regions of the electromagnetic spectrum.
18. The method of claim 17 , wherein the first housing component is the window and the second housing component is the sidewall.
19. The method of claim 16 , further comprising metallizing the sealing surface of the first housing component, the sealing surface of the second housing component, or the sealing surfaces of both the first and the second housing components with a metal that is wettable by the melted solder.
20. The method of claim 16 , wherein the cover, the base, and the sidewall are constructed from ultra-high vacuum compatible materials, and the vacuum pressure is no greater than 10 −5 .