Methods for fabricating apparatus having a hermetic seal
Methods for fabricating a hermetic seal to seal a portion of an apparatus, for example and without limitation, a portion having a MEMS sensor. One such method uses crimping devices to compress a seal in a cavity formed in a housing that includes a MEMS sensor attached to a stress isolator. Under such compression, the seal deforms to hermetically seal surfaces around the inside, outside and bottom of the stress isolator.
1. A method for sealing a sensor to a housing comprising:
providing a housing with a top and bottom and a hole that passes through the housing from the top to the bottom wherein the housing further comprises a first cavity that extends down into the housing from the top and is coaxial with the hole and wherein the housing further comprises a second cavity that extends down into the housing from the top and surrounds, and is coaxial with, the first cavity such that a cavity wall is formed between the first cavity and the second cavity;
pressing a cylindrically shaped radial seal with an axial height greater than a radial thickness inside the first cavity such that an outer wall of the radial seal fits against an inside surface of the cavity wall;
providing an isolation member coupled to the sensor;
placing the isolation member down into the radial seal within the first cavity;
placing a collar down into the second cavity of the housing and pressing the collar down such that it deforms the cavity wall and seals the housing to the isolation member.
2. The method of claim 1 , wherein the radial seal is a soft metal seal.
3. The method of claim 2 wherein the soft metal is soft copper.
4. The method of claim 3 wherein the housing is comprised of one or more of stainless steel, brass and aluminum.
5. The method of claim 2 wherein the soft metal is a soft copper alloy.
6. The method of claim 2 wherein the radial seal fits snugly inside the cavity wall.
7. The method of claim 6 wherein the sensor is a pressure sensor.
8. The method of claim 2 wherein the collar is pressed down with approximately 2 tons per square inch of pressure.
9. The method of claim 8 wherein the sensor is a pressure sensor.
10. The method of claim 1 wherein the seal is pressed down with approximately 0.5 tons per square inch of pressure.
11. The method of claim 10 wherein the collar is comprised of steel.
12. The method of claim 11 wherein the steel is high strength stainless steel.
13. The method of claim 1 wherein the sensor is a MEMS sensor.
14. The method of claim 1 wherein the housing is cylindrically shaped.
15. A method for sealing a sensor to a housing comprising:
providing a housing with a top and bottom and a hole that passes through the housing from the top to the bottom wherein the housing further comprises a first cavity that extends down into the housing from the top and is coaxial with the hole and wherein the housing further comprises a second cavity that extends down into the housing from the top and surrounds, and is coaxial with, the first cavity such that a cavity wall is formed between the first cavity and the second cavity;
pressing a cylindrically shaped radial seal inside the first cavity such that an outer wall of the radial seal fits against an inside surface of the cavity wall;
providing an isolation member coupled to the sensor;
placing the isolation member down into the radial seal within the first cavity;
placing a collar down into the second cavity of the housing and pressing the collar down such that it crimps the cavity wall against the isolation member and seals the housing to the isolation member with the radial seal.
16. The method of claim 15 , wherein the cavity wall is cylindrically shaped.
17. The method of claim 15 wherein the collar is pressed down with approximately 2 tons per square inch of pressure.
18. A method for sealing a sensor to a housing comprising:
providing a housing with a top and bottom and a hole that passes through the housing from the top to the bottom wherein the housing further comprises a first cavity that extends down into the housing from the top and is coaxial with the hole and wherein the housing further comprises a second cavity that extends down into the housing from the top and surrounds, and is coaxial with, the first cavity such that a cylindrical vertical cavity wall is formed between the first cavity and the second cavity;
pressing a cylindrically shaped radial seal with a thickness less than a width of the second cavity inside the first cavity such that an outer wall of the radial seal fits against an inside surface of the cavity wall;
providing an isolation member coupled to the sensor;
placing the isolation member down into the radial seal within the first cavity;
placing a collar down into the second cavity of the housing and pressing the collar down such that it deforms the cavity wall and deforms the seal and seals the housing to the isolation member.
19. The method of claim 18 wherein the collar is pressed down with approximately 2 tons per square inch of pressure.
20. The method of claim 18 wherein the radial seal is made of copper.