Method of thermally coupling a flow tube or like component to a thermal sensor and sensor systems formed thereby

• US 20070044554A1
• Filed: 08/26/2005
• Published: 03/01/2007
• Est. Priority Date: 08/26/2005
• Status: Active Grant

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Higashi, Robert, Satren, Ernest
• Granted Patent: US 7,408,133 B2
• Time in Patent Office: Days
• US Class Current: 73/204.250
• CPC Class Codes: G01F 1/6845 Micromachined devices
• CPC Class Codes: G01F 1/6847 where sensing or heating elements are not disturbing the fluid flow, e.g. elements mounted outside the flow duct
• CPC Class Codes: H01L 2224/81801 Soldering or alloying
• CPC Class Codes: Y10T 29/49004 including measuring or testing of device or component part

Abstract

A method of thermally coupling a flow tube or like component to a thermal sensor comprises bonding the component to the thermal sensor such that thermally conductive portions formed on the component are thermally coupled to corresponding sensing/heating elements disposed on the thermal sensor. The method can be employed to form a capillary mass flow sensor system. Thermally conductive portions, such as metal bands, can be formed on the outer surface of a capillary tube for bonding with corresponding resistive heat sensing and heating elements disposed on the substrate of a micro mass flow sensor. Bonding metal pads can be formed on the sensor surface preparatory to solder bonding the tube metal bands to the resistive sensing and heating elements.

Claims

1. A method of thermally coupling a component to a thermal sensor comprising:

applying a bonding material to the thermal sensor,

aligning at least one heat sensing/heating element disposed on said thermal sensor to a corresponding location on a component, and

bonding the component to said thermal sensor such that the or each heat sensing/heating element is thermally coupled to said corresponding location on said component surface.

2. The method of claim 1, wherein said thermal sensor comprises a microstructure having at least one heating sensing element disposed on the surface of said microstructure.

3. The method claim 2, wherein said microstructure has a plurality of heat sensing/heating elements disposed on said microstructure surface, the method further comprising

forming a plurality of thermally conductive attachment portions on said component surface, said attachment portions being formed for alignment with said corresponding heat sensing/heating elements disposed on said microstructure surface,

aligning said component attachment portions to the corresponding heat sensing/heating elements, and

bonding said component attachment portions to said heat sensing/heating elements such that said component portions are thermally coupled to said separate corresponding heat sensing/heating elements.

4. The method of claim 3, further comprising depositing thermally conductive bonding pads or layers on respective sensing/heating elements of said sensor for adhering said elements to said bonding material.

5. The method of claim 4, wherein forming said bonding pads comprises depositing nickel layers on said sensing/heating elements, and depositing gold layers on said nickel layers.

6. The method of claim 4, wherein bonding the component to the sensor comprises solder bonding said component attachment portions to said respective bonding pads.

7. The method of claim 4, wherein forming each bonding pad comprises depositing a pair of pads spaced apart such that a gap extends therebetween and whereby, when said tube is bonded to said bonding pads, the lower most part of the tube cross-section is seated in said gaps.

8. The method of claim 1, wherein said thermal sensor comprises a microstructure sensor having a microbrick or microfill structure providing a substantially solid structure beneath said heating/sensing element(s).

9. The method of claim 8, wherein said component comprises a capillary flow tube.

10. The method of claim 9, wherein forming a plurality of thermally conductive attachment portions comprises

forming partial or complete thermally conductive bands on the tube outer surface and substantially concentric with the tube for alignment with said bonding pads or layers.

11. The method of claim 1, further comprising

forming a plurality of thermally conductive attachment portions on the component surface, said attachment portions being formed for alignment with separate corresponding sensing/heating elements disposed on said thermal sensor surface, and

wherein applying said bonding material to said sensor comprises applying thermally conductive bonding material on said sensing/heating elements,

wherein aligning said component comprises aligning said component attachment portions to the corresponding sensing/heating elements, and

wherein bonding said component to said sensor comprises bonding said component attachment portions to said corresponding sensing/ heating elements.

12. The method of claim 11, further comprising

forming at least two attachment points spaced apart either side of said sensing element(s) for further aligning said component along said thermal sensor surface,

forming at least two attachment portions on said component surface for alignment with said attachment points,

applying bonding material to said attachment points,

aligning said attachment portions to said attachment points and

bonding said at least two attachment portions to said corresponding attachment points.

13. A method of forming a thermal flow sensor system comprising

providing a thermal sensor having upstream and downstream sensing elements and a heating element disposed on the upper surface of a substrate,

providing a capillary tube,

forming thermally conductive attachment portions on the surface of the capillary tube for alignment with the corresponding sensing and heating elements on said sensor bridge,

applying thermally conductive bonding material on said sensing and heating elements and/or said tube attachment portions

aligning said attachment portions with said corresponding sensing and heating elements to align said tube on the surface of said substrate, and

bonding said attachment portions to said corresponding sensing and heating elements such that said capillary tube is thermally coupled to said heating/sensing element(s).

14. The method of claim 13, wherein forming thermally conductive attachment portions comprises forming partial or complete metal bands about the outer surface of said tube.

15. The method of claim 13, further comprising forming metal bonding pads on said sensing and heating elements preparatory to bonding said attachment portions to said corresponding sensing and heating elements.

16. The method of claim 15, where bonding said tube attachment portions comprises solder bonding said attachment portions to respective said bonding pads.

17. A thermal flow sensor system comprising

a thermal sensor comprising a substrate and at least one heating and/or sensing element disposed on said substrate for sensing properties of a fluid,

a capillary flow tube bonded to said thermal sensor, said flow tube having formed thereon at least one thermally conductive area for alignment with a corresponding said sensing or heating element,

wherein the or each of said thermally conductive areas of said tube is bonded to said substrate by means of thermally conductive material such that the or each sensing/heating element is thermally coupled to a specific area of said capillary tube.

18. The system of claim 17, sensor wherein said thermal sensor further comprises an upstream sensing element, a down stream sensing element, and a resistive heating element disposed between said upstream and down stream sensing elements, said thermally conductive areas of said tube being separately bonded to said upstream and downstream sensing elements and said heating element.

19. The system of claim 17, wherein said substrate a microbrick or microfill structure providing a substantially solid structure beneath said heating/sensing element(s).

20. The system of claim 17, further comprising one or more metal bonding pads formed on said sensing and heating element(s) and wherein said tube thermally conductive areas are bonded to said metal pads.