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

• US 7,408,133 B2
• Filed: 08/26/2005
• Issued: 08/05/2008
• Est. Priority Date: 08/26/2005
• Status: Expired due to Fees

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Higashi, Robert E., Satren, Ernest A.
• Primary Examiner(s): Paschall; Mark H
• Application Number:
  US11/213,556
• Publication Number:
  US 20070044554A1
• Time in Patent Office: 1,075 Days
• Field of Search: 219/497, 219/499, 219/505, 219/508, 219483-487, 219/504, 219/541, 219/553, 338/13, 338/25, 732/042.5, 374/101, 374/107, 374/20
• US Class Current: 219/497
• 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, wherein said thermal sensor comprises a microstructure having a plurality of heat sensing/heating elements disposed on the surface of said microstructure,

affixing a plurality of separate thermally conductive bands to the outer surface of said component, said thermally conductive bands being separated from one another, substantially concentric with said component, and formed for alignment with the corresponding heat sensing/heating elements disposed on said microstructure surface,

aligning said separated thermally conductive bands on said component to the corresponding heat sensing/heating elements, and

bonding said separated thermally conductive bands affixed to said component to said heat sensing/heating elements such that said thermally conductive bands are thermally coupled to said corresponding heat sensing/heating elements.

2. The method claim 1, 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.

3. The method of claim 2, further comprising forming additional thermally conductive bonding pads at or adjacent diagonally opposing corners of said microstructure and away from and in alignment with said sensing/heating elements for bonding to corresponding component thermally conductive bands.

4. The method of claim 3, wherein forming said bonding pads comprises

depositing nickel layers on said sensing/heating elements, and depositing gold layers on said nickel layers.

5. The method of claim 3, wherein bonding the component to the sensor comprises solder bonding said component thermally conductive bands to said respective bonding pads.

6. The method of claim 3, wherein said component comprises a flow tube, and 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.

7. 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).

8. The method of claim 7, wherein said component comprises a capillary flow tube.

9. The method of claim 1, wherein said component comprises a flow tube, and

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,

wherein bonding the flow tube to the sensing/heating elements comprises solder bonding the separated thermally conductive bands to said respective bonding pads;

further comprising solder reflowing, subsequent to bonding the flow tube to the sensing/heating elements, in order to self-align the thermally conductive bands to the bonding pads such that the flow tube is correctly aligned on the microstructure.

10. The method of claim 9, further comprising

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

forming at least two thermally conductive bands separated from one another on said flow tube surface and concentric with said tube for alignment with said attachment points,

applying bonding material to said attachment points,

aligning said thermally conductive bands to said corresponding attachment points and

bonding said at least two thermally conductive bands to said corresponding attachment points.

11. 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,

affixing thermally conductive metal bands to the surface of the capillary tube, said metal bands being separated from one another and substantially concentric with said 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 metal bands

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

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

12. The method of claim 11, further comprising forming metal bonding pads on said sensing and heating elements and at or adjacent diagonally opposing corners of said microstructure away from and in alignment with said sensing/heating elements preparatory to bonding said metal bands to said corresponding bonding pads.

13. The method of claim 12, where bonding said tube metal bands comprises solder bonding said tube metal bands to respective said bonding pads.

14. The method of claim 13, further comprising solder reflowing, subsequent to bonding the capillary tube to the microstructure, in order to self-align the metal bands to the respective bonding pads such that the tube is correctly aligned on the microstructure.

15. A thermal flow sensor system comprising

a thermal sensor comprising a substrate and at least one heating and 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 a plurality of metal bands affixed thereon separated from one another and substantially concentric with said flow tube for alignment with a corresponding said sensing or heating element,

wherein said metal bands affixed to said tube are separately bonded to said substrate by means of thermally conductive material such that said sensing and heating elements are thermally coupled to specific separate areas of said capillary tube.

16. The system of claim 15, 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 metal bands affixed to said tube being separately bonded to said upstream and downstream sensing elements and said heating element.

17. The system of claim 15, wherein said substrate a microbrick or microfill structure providing a substantially solid structure beneath said heating/sensing element(s).

18. The system of claim 15, further comprising one or more metal bonding pads formed on said sensing and heating element(s) and wherein said metal bands affixed to said tube are bonded to said metal pads.