Method and apparatus for fabricating a thermoelectric array

• US 4,493,939 A
• Filed: 10/31/1983
• Issued: 01/15/1985
• Est. Priority Date: 10/31/1983
• Status: Expired due to Fees

• Current Assignee: Litton Systems Incorporated
• Original Assignee: Varo, Inc. (Northrop Grumman Corporation)
• Inventors: Hendricks, Terry J., Blaske, T. Allen
• Primary Examiner(s): Sebastian, Leland A.
• Application Number:
  US06/547,066
• Time in Patent Office: 442 Days
• Field of Search: 29/573, 29/588, 29/841, 62/3, 136/201, 136/203, 136/204, 136/212, 136/224, 136/225, 136/230, 357/55, 357/81, 357/87
• US Class Current: 136/212
• CPC Class Codes: H10N 10/01 Manufacture or treatment
• CPC Class Codes: Y10S 257/93 Thermoelectric, e.g. peltier effect cooling
• CPC Class Codes: Y10T 29/49146 with encapsulating, e.g., potting, etc.

Abstract

A method and apparatus for fabricating a thermoelectric device includes forming a matrix board (12) with an array of orifices (100) formed therein. A plurality of P-type thermoelements (96) are formed and then a vacuum chuck (92) is utilized to dispose alternating ones of the elements (96) into the alternating ones of the orifices (100). A plurality of N-type elements (108) is formed and a vacuum chuck (104) is utilized to dispose alternating ones of the elements (108) into the remaining orifices (100) of the matrix (12). This forms an assembled array (52). A plurality of conductive tabs (114) is placed onto the P-type elements (98) and N-type elements (108) by a vacuum chuck (116). A second set of conductive tabs (120) is disposed on the opposite side of the assembled array by a vacuum chuck (124). A solder flow oven (54) and a solder flow oven (76) are utilized to reflow the solder on the tabs between the two operations. After connecting the tabs, the assembly (78) is moved to an epoxy station (80) to form an epoxy layer around the peripheral surfaces thereof to form a void (146) in the center portion thereof.

Claims

1. A method of fabricating a thermoelectric device comprising:

simultaneously depositing a plurality of first conductivity type thermoelements in a matrix member in a first spaced apart configuration;

simultaneously depositing a plurality of second conductivity type thermoelements in the matrix member in a second spaced apart configuration to form an alternately disposed array of first and second conductivity type thermoelements within the matrix member; and

depositing and securing in a predetermined pattern a plurality of conductive members on opposite sides of said array of first and second type thermoelements in order to connect the thermoelements in series.

2. The method of claim 1 and further comprising:

removing the matrix member from the array; and

encapsulating said array such that a void area is defined within the central portion of the encapsulated array.

3. The method of claim 2 and further comprising providing the void area with a pressure less than atmospheric.

4. The method of claim 2 wherein the matrix member is removed by dissolving with a chemical which does not affect the array.

5. The method of claim 1 wherein the steps of simultaneously depositing comprise:

picking up a plurality of thermoelements prearranged in the spaced apart configuration;

transporting the thermoelements in the prearranged spaced apart configuration to a location above the matrix member; and

lowering the thermoelements into the matrix member.

6. The method of claim 5 wherein the thermo elements are held in the prearranged spaced apart configuration by vacuum.

7. A method of fabricating a thermoelectric device comprising:

forming a supporting matrix with a plurality of orifices therein in an array configuration;

forming a plurality of thermoelectric elements of a first conductivity type dimension to fit in the orifices;

disposing in one step the first type elements into alternate ones of the orifices in the matrix array;

forming a plurality of thermoelectric elements of a second conductivity type dimensioned similar to the first type element;

disposing in one step the second type elements into remaining ones of the orifices in the matrix array; and

disposing and securing a plurality of conductive bridges on opposite sides of the array of first and second type elements in a pattern that connects the distal ends of adjacent ones of the first and second type elements together to form an electrical series connection.

8. The method of claim 7 wherein the orifices are of equal size and equal spacing therebetween.

9. The method of claim 7 wherein the first and second type elements are of an elongated configuration having a length greater than the width of the supporting matrix and disposed in the supporting matrix such that the supporting matrix is about the midportion of each of the first and second type elements.

10. The method of claim 7 wherein the first type elements are of an N-type conductivity and the second type elements are of a P-type conductivity.

11. The method of claim 7 wherein the step of forming the first type elements comprises:

forming a wafer of the first conductivity type; and

dicing the wafer into a plurality of rectangular first type elements, the orifices in the supporting matrix being of a rectangular type also.

12. The method of claim 11 wherein the step of disposing the first or second type elements into the matrix array comprises:

selectively attaching desired ones of the first or second type elements, respectively, on the upper portions thereof to a mobile platform;

moving the mobile platform over the supporting matrix board such that the first or second type elements attached thereto are aligned over the respective ones of the orifices; and

releasing the respective ones of the first or second type elements into the respective orifices.

13. The method of claim 12 wherein the step of attaching comprises applying a vacuum to the respective ones of the first or second type elements and the step of releasing comprises releasing the vacuum.

14. The method of claim 12 wherein the step of attaching comprises applying a vacuum to the respective ones of the first or second type elements and the step of releasing comprises releasing the vacuum applied to the respective ones of the first or second type elements and creating a positive pressure thereto.

15. The method of claim 7 wherein the step of disposing and securing the conductive bridges comprises:

forming an array of first conductive bridges in a first predetermined pattern, the conductive bridges dimensioned to bridge between adjacent first and second type elements on the distal ends thereof with respect to the supporting matrix;

disposing in one step the first conductive bridges on one side of the array of first and second type elements, the first predetermined pattern bridging pairs of first and second type elements;

securing the first array of conductive bridges to the respective surfaces of the first and second type elements;

forming a second array of conductive bridges in a second predetermined pattern, the conductive bridges in the second array dimensioned similar to the conductive bridges in the first array;

disposing in one step the second array of conductive bridges on the opposite side of the array of first and second type elements, the second predetermined pattern bridging pairs of first and second type elements to bridge between elements that were not bridged between on the one side of the array of first and second type elements; and

securing the second array of conductive bridges to the surfaces of the first and second type elements.

16. The method of claim 7 further comprising encapsulating the array of first and second type elements disposed in the supporting matrix board.

17. The method of claim 7 further comprising encapsulating the peripheral surfaces of the array of first and second type elements disposed in the supporting matrix board to form a void in the center thereof.

18. The method of claim 17 wherein the supporting matrix is removed prior to final encapsulation of the peripheral surfaces of the array of first and second type elements.

19. The method of claim 17 further comprising disposing a low thermal conductance material within the void.

20. The method of claim 17 further comprising creating a vacuum within the void during formation of the peripheral surfaces.

21. The method of claim 7 further comprising removing the supporting matrix by dissolving thereof.

22. A method for fabricating a thermoelectric device, comprising:

forming a supporting matrix with a plurality of orifices formed therein in an array configuration;

forming a plurality of thermoelectric elements of a P-type conductivity dimensioned to fit in the orifices;

arranging the P-type elements in a subarray, the subarray configured identical to the supporting matrix array;

selecting alternate ones of the P-type elements in the subarray and transporting them as a single unit over the supporting matrix and simultaneously disposing the selected ones of the P-type elements in alternate ones of the orifices;

forming a plurality of thermoelectric elements of an N-type conductivity;

arranging the N-type elements in a subarray identical to the supporting matrix array;

selecting alternate ones of the N-type elements in the subarray and transporting them as a single unit over the supporting matrix with the P-type elements therein and disposing the selected N-type elements into the remaining ones of the orifices;

forming a first array of conductive bridges in a first predetermined pattern, the conductive bridges dimensioned to bridge between adjacent P and N-type elements on the distal ends thereof with respect to the supporting matrix;

disposing in one step the first array of bridges on one side of the array of P and N-type elements, the first array bridging alternate pairs of P and N-type elements;

securing the first array of bridges to the surfaces of the P and N-type elements;

forming a second array of conductive bridges in a second predetermined pattern, the bridges therein dimensioned identical to the bridges in the first array;

disposing in one step the second array of bridges on the opposite side of the array of the P and N-type elements, the pattern of the second array bridging between the pairs bridged by the first array of bridges such that a series circuit of alternating P and N-type elements is formed; and

securing the second array of bridges to the respective surfaces of the P and N-type elements in the supporting matrix.

23. The method of claim 22 further comprising encapsulating the P and N-type elements in the supporting matrix.

24. The method of claim 22 further comprising encapsulating the peripheral boundaries of the array of first and second type elements to form a void in the center thereof.

25. The method of claim 24 wherein the void in the center of the array has a vacuum formed therein.

26. The method of claim 24 wherein a gas is disposed in the void.

27. A method of fabricating a multi-stage thermoelectric device, comprising:

forming a plurality of thermoelectric stages comprising the steps of;

simultaneously depositing a plurality of first conductivity type thermoelements in a matrix member in a first spaced apart configuration,

simultaneously depositing a plurality of second conductivity type thermoelements in the matrix member in a second spaced apart configuration to form an alternately disposed array of first and second conductivity type thermoelemenets within the matrix member, and

depositing and securing in a predetermined pattern a plurality of conductive members on opposite sides of said array of first and second type thermoelements in order to connect the thermoelements in series;

disposing at least one of the thermoelectric stages adjacent another one of the thermoelectric stages such that respective members are proximate each other;

providing high thermal conductivity between the adjacent stages which electrically insulate the adjacent stages from each other; and

attaching the adjacent stages together.

28. A system for fabricating thermoelectric arrays comprising:

means for separating a body of a first conductivity type material into a plurality of first type elements;

a matrix defining a plurality of cells;

first means for transporting selected ones of said first type elements to said matrix and simultaneously depositing said first type elements in alternate ones of said cells;

means for separating a body of a second conductivity type material into a plurality of second type elements;

second means for transporting selected ones of said second type elements to said matrix and simultaneously depositing said second type elements in alternate ones of said cells, wherein said matrix is filled with alternating first and second type elements; and

means for electrically connecting contacts to said alternating first and second type elements to form a thermoelectric array.

29. The system of claim 28 wherein said matrix is formed of a rectangle of rectangular cells wherein said bodies of first and second type conductivity material are separated to form elements dimensioned similar to said cells, said first transporting means removing alternating ones of said elements from said first type body for deposit in said matrix and said second transporting means removing alternating ones of said elements from said second-type body for deposit in said matrix.

30. The system of claim 28 wherein said first conductivity type is a semiconductor material having a P-type doping and said second conductivity type is a semiconductor material having an N-type doping.

31. The system of claim 28 wherein said first and second means for transporting comprises a vacuum chuck with a plurality of orifices disposed therein for being disposed adjacent the selected ones of said first or second type elements, respectively, that are to be selected, said vacuum chuck mobile to transport the respective ones of said first or second type elements to said matrix.

32. The system of claim 28 further comprising means for encapsulating the array of first and second type elements in said matrix board.

33. The system of claim 28 further comprising means for encapsulating the peripheral surfaces of the array of said first and second type elements disposed in said matrix such that a void is formed in the center portion thereof.

34. The system of claim 33 further comprising means for drawing a vacuum on said void.

35. The system of claim 33 further comprising means for introducing a low thermal conductivity material into said void

36. The system of claim 28 further comprising means for removing the matrix by dissolving thereof after said first and second type elements are electrically connected.

37. A thermoelectric device comprising:

a plurality of P-type and N-type conductivity elements arranged in an alternating array;

contacts electrically connecting said elements together to form a series of P-N junctions;

encapsulating material sealing the exterior surfaces of said elements to form a unitary body; and

a central void area being defined within said unitary body and communicating with central portions of each of said elements, said void area having a low thermal conductance.

38. A system for fabricating a thermoelectric device, comprising:

a matrix having a plurality of orifices disposed in a planar array;

means for forming a plurality of P-type conductivity thermoelectric elements;

means for arranging said P-type elements in a subarray, said subarray similar to said matrix array;

means for selectively transporting alternating ones of said P-type elements in said subarray to said matrix array and simultaneously depositing said selected P-type elements therein;

means for forming a plurality of N-type conductivity thermoelectric elements;

means for arranging said N-type elements into a subarray similar to said matrix array;

means for selectively transporting alternating ones of said N-type elements to said matrix array and simultaneously depositing said selected N-type elements into the remaining ones of said orifices in said matrix array wherein selected P and N-type elements are disposed in said matrix array in an alternating pattern, said matrix array disposed about the midportions of said selected P and N-type elements; and

means for electrically connecting alternating ones of said P and N-type elements in a series configuration to form a P-N thermoelectric device.

39. The system of claim 38 wherein said means for connecting comprises:

a plurality of conductive bridges;

solder for being disposed on said thermoelectric elements;

means for arranging a portion of said conductive bridges in a first predetermined array;

means for transporting said bridges in said first array to one side of the array of selected P and N-type elements to conductively bridge between adjacent ones of said P and N-type elements;

means for reflowing said solder to attach said conductive bridges to the surfaces of the said selected P and N-type elements;

means for arranging said conductive bridges in a second array;

means for transporting said conductive bridges in said second array to the opposite side of the array of said selected P and N-type elements to bridge between said selected P and N-type elements to form a series connected circuit thereof; and

means for reflowing the solder on said connective conductive bridges in said second array for securing thereof.

40. The system of claim 38 further comprising means for encapsulating the peripheral surfaces of the array of said P and N-type elements to form a void in the center portion thereof.

41. The system of claim 38 further comprising means for removing the matrix array from the secured ones of said selected P and N-type elements.

42. A thermoelectric device, comprising:

a first stage having a plurality of alternating P-type and N-type elements connected together in a series configuration to provide a thermoelectric effect;

a second stage having a plurality of P-type and N-type thermoelements connected together in a series configuration to provide a thermoelectric effect;

a thermally conducting plate disposed between said first and second stages; and

means for attaching said first and second stages together with said plate disposed therebetween, said attaching means providing electrical insulation between said first and second stages.

43. The device of claim 42 wherein said means for attaching comprises a layer of thermally conductive epoxy disposed between said first stage and one surface of said plate and a layer of thermally conductive epoxy disposed between said second stage and the other surface of said plate.