Low power high voltage thermopile

• US 4,032,363 A
• Filed: 01/27/1975
• Issued: 06/28/1977
• Est. Priority Date: 01/27/1975
• Status: Expired due to Term

• Current Assignee: Syncal Corporation
• Original Assignee: Syncal Corporation
• Inventors: Raag, Valvo
• Primary Examiner(s): Hunt, Brooks H.
• Application Number:
  US05/544,363
• Time in Patent Office: 883 Days
• Field of Search: 136/202, 136/239, 136/201, 136/211, 136/212, 136/205, 29/573
• US Class Current: 136/211
• CPC Class Codes: H10N 10/00 Thermoelectric devices comprising a junction of dissimilar materials, i.e. devices exhibiting Seebeck or Peltier effects integrated devices or assemblies of multiple devices H10N19/00
• CPC Class Codes: H10N 10/01 Manufacture or treatment
• CPC Class Codes: H10N 10/17 characterised by the structure or configuration of the cell or thermocouple forming the device
• CPC Class Codes: H10N 10/80 Constructional details
• CPC Class Codes: H10N 10/817 the junction being non-separable, e.g. being cemented, sintered or soldered
• CPC Class Codes: H10N 10/82 Connection of interconnections
• CPC Class Codes: H10N 10/855 comprising compounds containing boron, carbon, oxygen or nitrogen

Abstract

An electrical power generating array of a semiconductor, laminar structured thermopile for producing low values of electrical power at high values of direct output voltage and a method for its manufacture including the step of lapping opposed semiconductor layers bonded on opposite sides of a glass layer to achieve a predetermined thinness.

Claims

1. A method of manufacturing a thermopile using silicon-germanium alloys comprising the steps of sawing n- and p-type silicon-germanium alloy materials into parallelepipeds, cutting the n- and p-type silicon-germanium alloy parallelepipeds into slices, surface finishing both large faces of each slice so that both of the large faces of each slice are parallel to each other, cleaning the slices, coating at least one large face of each slice with a glass powder, the glass having a softening point above the intended operational temperature of the thermopile, a high resistivity, and a linear thermal expansion coefficient which approximately matches that of the silicon-germanium alloy, sintering each glass-coated slice at a temperature close to the softening temperature of the glass to locally bond the glass powder particles to each other and to the slice, stacking each glass-coated slice with another slice so that a glass layer occurs between the two silicon-germanium alloy slices to form a sandwich stack, heating each sandwich stack to a temperature at which the glass bonds the two slices together with an intermediate glass layer, surface finishing at least one of the outer, large faces of each heat-bonded sandwich stack down to the point that the total sandwich stack has a predetermined desired thickness, covering at least one face of each surface-finished sandwich stack with glass powder, stacking a plurality of the glass powder-covered individual sandwich stacks in a predetermined arrangement of conductivity types depending upon the type of thermopile desired to form a first seal assembly, heating this first seal assembly until the intermediate glass layers fuse and hold the silicon-germanium alloy layers together, slicing this fused structure perpendicularly to the laminations to produce a laminate structure, and interconnecting the ends of the laminated silicon-germanium elements of opposite conductivity types to form a thermopile having a predetermined voltage and power output.

2. The method as recited in claim 1 further comprising the steps of reprocessing the laminate structure prior to the interconnecting step according to the method steps of claim 1 as though the laminate structure were the original silicon-germanium alloy material, with all of the slicing being done perpendicularly to the laminations.

3. The method as recited in claim 1 further comprising the steps of coating the silicon-germanium alloy material prior to each glass coating operation with a special wetting agent to enhance the wetting adherence between the glass and the silicon-germanium alloy.

4. The method as recited in claim 3 wherein the wetting agent coating step comprises chemical vapor depositing silicon-nitride, Si₃ Ni₄, on all of the large surfaces of the slices.

5. The method as recited in claim 4 further comprising the step of chemically vapor depositing a coating of silicon-dioxide, SiO₂, on top of the silicon-nitride layer.

6. The method as recited in claim 1 wherein prior to the interconnecting step the ends of the thermopile are lapped and then coated with a glass powder which is thereafter heat bonded to the structure and relapping the glass coated thermopile ends and repeating the glass coating and lapping steps until no voids or imperfections are uncovered during the lapping process in order to prevent bridging between the interconnections on the ends of the thermopile.

7. The method as recited in claim 1 wherein the interconnecting step comprises bonding separate silicon containing elements to the ends of the thermopile elements.

8. The method as recited in claim 1 wherein the interconnecting step comprises bonding metal elements to the ends of the thermopile elements, the metal elements having thermal coefficients of expansion at least twenty percent different than the thermal coefficient of expansion of the silicon-germanium alloy.

9. The method as recited in claim 1 wherein the interconnecting step comprises affixing metal elements to the ends of the thermopile elements and heating the assembly to a temperature sufficient to at least partially react the metal with the silicon-germanium alloy to develop a low electrical resistance, ohmic contact between the metal and the thermoelements.

10. The method as recited in claim 1 further comprising the step of potting the entire thermopile in an electrical insulator to provide insulation and to protect the thermopile from deleterious substances in the environment.

11. The method as recited in claim 1 further comprising the step of slotting one side of the thermopile, placing metal wires or ribbons in the slots, and heating the thermopile and the metal wires to the temperature at which the metal forms a eutectic with the silicon-germanium alloy.

12. The method as recited in claim 1 further comprising the steps of bonding separate metal leads to at least one side of the thermopile such that one end of each lead is flush with one end of the thermopile and connecting the flush end of each lead to separate thermoelements.

13. A semiconductor thermopile constructed by the method recited in claim 1 such that the thickness of each silicon-germanium alloy thermopile element is on the order of 1.5 mils, which thickness is obtained during the step of surface finishing the two slice sandwich stacks.

14. A method of manufacturing a thermopile using silicon-germanium aloys comprising the steps of sawing n- and p-type silicon-germanium alloy material into parallelepipeds, cutting the n- and p-type silicon-germanium alloy parallelepipeds into slices, surface finishing both large faces of each slice so that both of the large faces of each slice are parallel to each other, cleaning the slices, coating one large face of each slice with an insulator, the insulator having a high resistivity, bonding the insulator to the slice, surface finishing the outer, uncoated large face of each bonded, insulator coated slice down to the point that the slice has a predetermined desired thickness, stacking a plurality of the insulator covered individual slices so that the slices are separated from one another by a layer of the insulator between them and in a predetermined arrangement of conductivity types depending upon the type of thermopile desired to form a first seal assembly, bonding this first seal assembly so that the intermediate insulator layers hold the silicon-germanium alloy layers together, and interconnecting the ends of at least a portion of the laminated silicon-germanium elements of opposite conductivity types to form a thermopile having a predetermined voltage and power output.