Brazed wick for a heat transfer device and method of making same

• US 7,137,443 B2
• Filed: 02/10/2005
• Issued: 11/21/2006
• Est. Priority Date: 06/26/2003
• Status: Expired due to Fees

• Current Assignee: Thermal Corporation (Roper Technologies, Inc.)
• Original Assignee: Thermal Corporation (Roper Technologies, Inc.)
• Inventors: Rosenfeld, John H., Minnerly, Kenneth G.
• Primary Examiner(s): DUONG, THO V
• Application Number:
  US11/054,825
• Publication Number:
  US 20050167086A1
• Time in Patent Office: 649 Days
• Field of Search: 165/104.21, 165/104.26, 165/133, 165/907, 298/900.32, 295/272, 419/2, 419/6, 419/38, 419/65
• US Class Current: 165/104.26
• CPC Class Codes: B22F 2201/013 Hydrogen
• CPC Class Codes: B22F 2201/20 Use of vacuum
• CPC Class Codes: B22F 2998/00 Supplementary information concerning processes or compositions relating to powder metallurgy
• CPC Class Codes: B22F 3/1103 with particular physical characteristics
• CPC Class Codes: F28D 15/0233 the conduits having a particular shape, e.g. non-circular cross-section, annular F28D15/0241, F28D15/0266 take precedence
• CPC Class Codes: F28D 15/046 characterised by the material or the construction of the capillary structure
• CPC Class Codes: F28F 2275/04 by brazing
• CPC Class Codes: H01L 23/427 Cooling by change of state, e.g. use of heat pipes by liquefied gas H01L23/445
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: Y10T 29/49353 Heat pipe device making

Abstract

A capillary structure for a heat transfer device, such as a heat pipe is provided having a plurality of particles joined together by a brazing compound such that fillets of the brazing compound are formed between adjacent ones of the plurality of particles. In this way, a network of capillary passageways are formed between the particles to aid in the transfer of working fluid by capillary action, while the plurality of fillets provide enhanced thermal transfer properties between the plurality of particles so as to greatly improve over all heat transfer efficiency of the device. A method of making the capillary structure according to the invention is also presented.

Claims

1. A method for making a capillary structure on an inside surface of a container, comprising the steps of:

(a) providing a slurry of metal particles that are mixed with a brazing compound wherein said metal particles comprise a first melting temperature and said brazing compound comprises a second melting temperature that is lower than said first melting temperature;

(b) mixing two drops of an organic liquid binder with said slurry of metal particles to create an adhesive quality on their surface;

(c) coating at least portion of said inside surface of said container with said slurry;

(d) drying said slurry to form a green wick; and

(e) heating said green wick to a temperature that is no less than said second melting temperature and below said first melting temperature so that said brazing compound is drawn by capillary action toward adjacent of said metal particles so as to form heat-distribution fillets between said adjacent metal particles thereby to yield a brazed wick.

2. A capillary structure formed according to the method of claim 1.

3. The method of claim 1 wherein said organic liquid binder comprises isobutyl methacrylate lacquer.

4. The method of claim 1 wherein step (a) comprises mixing six percent weight of copper/gold in a ratio of 65%/35% of finely divided minus three hundred and twenty-five mesh with an organic liquid binder coated copper powder and allowing said mixture to thoroughly air dry.

5. The method of claim 1 wherein step (c) comprises coating a copper surface with an organic binder;

sparsely coating said copper surface with brazing compound comprising six percent weight of copper/gold in a ratio of 65%/35% of finely divided, minus three hundred and twenty-five mesh; and

removing excess brazing compound from said copper surface.

6. The method of claim 1 wherein step (c) further comprises placing a mandrel on top of said slurry so as to form a plurality of grooves in said green wick.

7. The method of claim 1 wherein step (d) comprises vacuum firing said green wick at 1020°

C. for five minutes wherein said vacuum is no more than 5×

10−

5 torr.

8. A method for making a heat pipe wick on an inside surface of a heat pipe container, comprising the steps of:

(a) positioning a mandrel having a grooved contour and a plurality of recesses within a portion of said container;

(b) providing a slurry of metal particles having an average particle diameter and that are mixed with a brazing compound wherein said metal particles comprise a first melting temperature and said brazing compound comprises a second melting temperature that is lower than said first melting temperature;

(c) coating at least portion of the inside surface of said container with said slurry so that said slurry conforms to said grooved contour of said mandrel and forms a layer of slurry between adjacent grooves that comprises no more than about six average particle diameters;

(d) drying said slurry to form a green wick; and

,

(e) heating said green wick to a temperature that is no less than said second melting temperature and below said first melting temperature so that said brazing compound is drawn by capillary action toward adjacent of said metal particles so as to form heat-distribution fillets between said adjacent metal particles thereby to yield a brazed wick.

9. A heat pipe wick formed according to the method of claim 8.

10. A heat pipe wick formed according to the method of claim 8 wherein said layer of slurry comprises a thickness that is less than about three average particle diameters.

11. A heat pipe wick formed according to the method of claim 8 wherein said layer of slurry comprises particles that are formed substantially of copper.

12. A heat pipe wick formed according to the method of claim 8 wherein six of said average particle diameters is within a range from about 0.05 millimeters to about 0.25 millimeters.