Systems, method and apparatus for curing conductive paste

• US 10,074,765 B2
• Filed: 07/12/2017
• Issued: 09/11/2018
• Est. Priority Date: 05/24/2016
• Status: Active Grant

• Current Assignee: Tesla Inc.
• Original Assignee: Tesla Inc.
• Inventors: Sung, Edward, Zu-Yi Liu, James
• Primary Examiner(s): Sarkar, Asok K
• Application Number:
  US15/647,776
• Publication Number:
  US 20170345963A1
• Time in Patent Office: 426 Days
• Field of Search: None
• CPC Class Codes: H01L 21/67115 mainly by radiation
• CPC Class Codes: H01L 21/6776 Continuous loading and unloading into and out of a processing chamber, e.g. transporting belts within processing chambers
• CPC Class Codes: H01L 25/50 Multistep manufacturing processes of assemblies consisting of devices, each device being of a type provided for in group H01L27/00 or H01L29/00 H01L21/50 takes precedence
• CPC Class Codes: H01L 31/0512 made of a particular material or composition of materials
• CPC Class Codes: H01L 31/1864 Annealing
• CPC Class Codes: Y02E 10/50 Photovoltaic [PV] energy

Abstract

One embodiment can provide a system for curing conductive paste applied on photovoltaic structures. The system can include a wafer carrier for carrying a plurality of photovoltaic structures and a heater. The wafer carrier can include a surface element that is in direct contact with the photovoltaic structures and is substantially thermally insulating. The heater can be positioned above the wafer carrier. The heater can include a heated radiation surface that does not directly contact the photovoltaic structures.

Claims

1. A system for curing a conductive paste applied to two adjacent photovoltaic structures, comprising:

a wafer carrier for carrying the two adjacent photovoltaic structures on a first side of the wafer carrier, wherein the two photovoltaic structures are coupled in a cascaded manner by the conductive paste;

wherein the wafer carrier includes a surface element that is in direct contact with the photovoltaic structures and is substantially thermally insulating; and

a heater positioned adjacent to the first side of the wafer carrier, wherein the heater includes a heated radiation surface that faces the photovoltaic structures without directly contacting the photovoltaic structures, and wherein the heated radiation surface is configured to radiate heat to the two photovoltaic structures for a predetermined duration to cure the conductive paste.

2. The system of claim 1, wherein the surface element comprises polybenzimidazole (PBI) plastic.

3. The system of claim 1, wherein a surface of the surface element is patterned such that a fraction of the surface is in contact with the photovoltaic structures.

4. The system of claim 1, wherein the surface element includes a number of components separated by air gaps to allow an individual component to expand when heated.

5. The system of claim 1, wherein the heated radiation surface has a temperature between 200 and 600°

C.

6. The system of claim 1, wherein the heater includes a radiation block, and wherein the heated radiation surface of the radiation block is coated with a substantially dark colored coating.

7. The system of claim 6, wherein the substantially dark colored coating includes an anodizing coating or a high-emissivity coating, and wherein a thickness of the dark colored coating is between 1 and 100 microns.

8. The system of claim 6, wherein other surfaces of the radiation block are polished or covered with a layer of thermal insulation material.

9. The system of claim 6, wherein the radiation block is made of a material having a thermal conductivity of at least 50 W/(m·

k).

10. The system of claim 1, further comprising a conveyor system configured to transfer the wafer carrier.

11. The system of claim 1, wherein the predetermined duration is between 25 and 60 seconds.

12. A solar module fabrication method, comprising:

obtaining a plurality of photovoltaic structures, wherein a photovoltaic structure includes a first edge busbar on a first edge of a first surface and a second edge busbar on an opposite edge of an opposite surface;

applying conductive paste on the first edge busbar of each photovoltaic structure;

aligning the photovoltaic structures on a wafer carrier in such a way that the first edge busbar of a first photovoltaic structure overlaps the second edge busbar of an adjacent photovoltaic structure with the conductive paste sandwiched in between;

positioning the wafer carrier to a vicinity of a heated radiation surface for a predetermined duration such that heat transferred from the heated radiation surface to the photovoltaic structures cures the conductive paste, thereby mechanically bond the photovoltaic structure to form a string.

13. The solar module fabrication method of claim 12, further comprising:

placing the wafer carrier on a conveyer; and

controlling movement of the conveyor to position the wafer carrier to the vicinity of the heated radiation surface.

14. The solar module fabrication method of claim 12, wherein the wafer carrier includes a surface element that is in direct contact with the photovoltaic structures and is substantially thermally insulating.

15. The solar module fabrication method of claim 14, wherein the surface element of the wafer carrier comprises polybenzimidazole (PBI) plastic.

16. The solar module fabrication method of claim 14, wherein the surface element includes a number of components separated by air gaps to allow an individual component to expand when heated.

17. The solar module fabrication method of claim 12, wherein the heated radiation surface is maintained at a predetermined temperature between 200 and 600°

C.

18. The solar module fabrication method of claim 12, wherein the heated radiation surface of the heating block is coated with a substantially dark colored coating.

19. The solar module fabrication method of claim 18, wherein the substantially dark colored coating includes an anodizing coating or a high-emissivity coating, and wherein a thickness of the dark colored coating is between 1 and 100 microns.

20. The solar module fabrication method of claim 18, wherein other surfaces of the heating block are polished or covered with a layer of thermal insulation material.