Air-gap insulator for short-term exposure to a high temperature environment

• US 20050052844A1
• Filed: 09/08/2003
• Published: 03/10/2005
• Est. Priority Date: 09/08/2003
• Status: Active Grant

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Ehlers, Wayne L., Skarlupka, Michael J., McCollum, Dave R.
• Granted Patent: US 7,023,695 B2
• Time in Patent Office: Days
• US Class Current: 361/689
• CPC Class Codes: H05K 5/0209 Thermal insulation, e.g. for fire protection or for fire containment or for high temperature environments
• CPC Class Codes: H05K 5/0213 Venting apertures; Constructional details thereof
• CPC Class Codes: H05K 7/1434 for electronics exposed to high gravitational force; Cylindrical housings

Abstract

A packaging system for electronic circuitry is provided. The electronic circuitry may be disposed upon a substrate, which can be encased or otherwise surrounded by one or more components of the packaging system. The packaging system may include (i) an inner housing that can encase or otherwise enclose the substrate within its confines; (ii) an outer housing that in turn encases or encloses the combination of the inner housing and the substrate within its confines; and (iii) one or more gaps positioned between the electronic circuitry, inner housing and outer housing. The gaps may be filled with fluid or solid insulating media. The combination of the inner housing, outer housing, and gaps can insulate the electronic circuitry from the detrimental and destructive heating effects when the packaging system experiences short-term exposure to a high temperature, which thereby allows operability before, during and after such exposure.

Claims

1. A packaging system for electronic circuitry, wherein the electronic circuitry is disposed on a substrate, the packaging system comprising in combination:

an inner housing surrounding the substrate;

an outer housing surrounding the inner housing and the substrate; and

a gap positioned between the inner and outer housings, the gap filled with insulating media, whereby when the packaging system experiences short term exposure to a high temperature, the combination of the inner housing, the outer housing, and the gap allow the electronic circuitry to maintain operability.

2. The system recited in claim 1, wherein the insulating media is a fluid.

3. The system recited in claim 2, wherein the fluid is air.

4. The system recited in claim 1, wherein the substrate having the electronic circuitry disposed thereon comprises a substrate selected from the group of substrates consisting of a silicon-based substrate, a ceramic-based substrate, and a circuit-board-based substrate.

5. The system recited in claim 1, wherein the electronic circuitry comprises sensing electronics.

6. The system recited in claim 5, wherein the sensing electronics comprises a proximity sensor.

7. The system recited in claim 6, wherein the proximity sensor comprises a sensing element selected from the group consisting of a hall-effect sensing element, a magnetoresistive-sensing element, a potentiometric-sensing element, and an ultrasound-sensing element.

8. The system recited in claim 1, wherein the inner housing is fabricated from a material having low thermal conductivity.

9. The system recited in claim 1, wherein the inner housing is fabricated from a material selected from the group consisting of plastic, ceramic, and metallic materials.

10. The system recited in claim 1, wherein the outer housing is fabricated from a material having high thermal conductivity.

11. The system recited in claim 1, wherein the outer housing is fabricated from a material selected from the group consisting of steel, plastic, and ceramic materials.

12. The system recited in claim 1, wherein the gap has a first thickness if the inner housing is fabricated from a material having a low conductivity and the outer housing is fabricated from a material having a high thermal conductivity, wherein the gap has a second thickness if the inner and outer housings are fabricated from a material having a low conductivity, and wherein the first thickness is greater than the second thickness.

13. The system recited in claim 1, wherein the high temperature comprises a temperature of up to about 425 degrees Celsius.

14. The system recited in claim 1, wherein the short-term exposure comprises a period up to about 15 seconds.

15. The system recited in claim 1, wherein the electronic circuitry maintains operability during and after the short-term exposure to a high temperature.

16. The system recited in claim 1, further comprising a second gap positioned between the inner housing and the substrate, the second gap filled with insulating media, wherein the second gap provides an additional insulating layer.

17. A packaging system for electronic circuitry, wherein the electronic circuitry is disposed on a substrate, the packaging system comprising in combination:

an inner housing fabricated from material having low thermal conductivity, the inner housing defining a first cavity for accepting the substrate, the inner housing including an outer surface having at least one protrusion extending away from the outer surface;

an outer housing defining a second cavity for accepting the inner housing and substrate, the second cavity including an inner surface for contacting the at least one protrusion extending from the outer surface of the inner housing; and

a gap positioned between the outer surface of the inner housing and the inner surface of the outer housing, the gap filled with an insulating media, whereby when the packaging system experiences short term exposure to a high temperature, the combination of the inner housing, the outer housing, and the gap allow the electronic circuitry to maintain operability.

18. The system recited in claim 17, wherein

the inner housing is substantially cylindrical and has distal and proximate ends, the proximate end having an opening for the first cavity,

at least one protrusion from the outer surface of the inner housing defines (i) at least one first pedestal located on the distal end, (ii) a plurality of second pedestals located axially on the outer surface of the inner housing close to the distal end, and (iii) at least one ring located radially on the outer surface of the inner housing close to the proximate end,

the inner surface of the second cavity of the outer housing defines a cylindrical portion having distal and proximate ends, the proximate end having an opening for the second cavity, wherein when the inner housing is inserted in the outer housing, (i) at least one first pedestal contacts the distal end of the second cavity, (ii) the plurality of second pedestals contact the inner surface of the second cavity, and (iii) the at least one ring contacts the inner surface of the second cavity, and

the gap filled with insulating media defines a region between the outer surface of the inner housing and the inner surface of the outer housing when the inner housing is inserted in the outer housing.

19. The system recited in claim 18, wherein the substrate has distal and proximate ends, wherein when the substrate is accepted into the first cavity, the distal end of the substrate is close to the distal end of the first cavity and the proximate end of the substrate is close to the proximate end of the first cavity, and wherein the electronic circuitry comprises sensing electronics having a termination cable for coupling the sensing electronics to an external device, the termination cable protruding from the proximate end of the first cavity when the substrate is accepted into the first cavity.

20. The system recited in claim 19, further comprising at least one seal for sealing (i) the substrate within the first cavity, and (ii) the proximate ends of the inner and outer housings to each other, and wherein the termination cable passes through the seal.

21. The system recited in claim 17, further comprising a second gap positioned between the first cavity and the substrate, the second gap filled with insulating media, and the second gap providing an additional insulating layer.

22. The system recited in claim 21, further comprising an electromagnetic interference shield positioned between the outer surface of the inner housing and the substrate, the electromagnetic interference shield surrounding at least a portion of the substrate.

23. The system recited in claim 17, further comprising an electromagnetic interference shield positioned between the outer surface of the inner housing and the substrate, the electromagnetic interference shield surrounding at least a portion of the substrate.

24. A kit comprising:

the packaging system for electronic circuitry of claim 21, and

mounting hardware.