Method for making embedded electrical traces

• US 6,591,496 B2
• Filed: 08/28/2001
• Issued: 07/15/2003
• Est. Priority Date: 08/28/2001
• Status: Expired due to Term

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Miller, Michael N., Jing, Naiyong, Koskenmaki, David C.
• Primary Examiner(s): Arbes, Carl J.
• Application Number:
  US09/941,058
• Publication Number:
  US 20030042045A1
• Time in Patent Office: 686 Days
• Field of Search: 298/52, 298/40, 298/32, 298/46, 298/33, 298/25
• US Class Current: 29/846
• CPC Class Codes: G02F 1/13439 characterised by their electrical, optical, physical properties; materials therefor; method of making
• CPC Class Codes: G02F 1/155 Electrodes
• CPC Class Codes: H05B 2203/017 Manufacturing methods or apparatus for heaters
• CPC Class Codes: H05B 3/286 the insulating material being an organic material, e.g. plastic
• CPC Class Codes: H05B 3/86 the heating conductors being embedded in the transparent or reflecting material H05B3/845 takes precedence
• CPC Class Codes: H05K 2201/0133 Elastomeric or compliant polymer
• CPC Class Codes: H05K 2201/09036 Recesses or grooves in insulating substrate
• CPC Class Codes: H05K 2201/091 Locally and permanently deformed areas including dielectric material
• CPC Class Codes: H05K 2201/09827 Tapered, e.g. tapered hole, via or groove
• CPC Class Codes: H05K 2203/0278 Flat pressure, e.g. for connecting terminals with anisotropic conductive adhesive
• CPC Class Codes: H05K 2203/1105 Heating or thermal processing not related to soldering, firing, curing or laminating, e.g. for shaping the substrate or during finish plating
• CPC Class Codes: H05K 3/102 by bonding of conductive powder, i.e. metallic powder H05K3/12 takes precedence
• CPC Class Codes: H05K 3/107 by filling grooves in the support with conductive material H05K3/045, H05K3/101, H05K3/1258 and H05K3/465 take precedence
• CPC Class Codes: H05K 3/1258 by using a substrate provided with a shape pattern, e.g. grooves, banks, resist pattern
• CPC Class Codes: Y10S 428/901 Printed circuit
• CPC Class Codes: Y10T 29/49128 Assembling formed circuit to base
• CPC Class Codes: Y10T 29/49155 Manufacturing circuit on or in base
• CPC Class Codes: Y10T 29/49165 by forming conductive walled aperture in base
• CPC Class Codes: Y10T 428/24917 including metal layer

Abstract

A method for making a fine electrically conductive grid embedded in a polymer substrate. The method includes the steps of providing a polymer substrate, forming a pattern of grooves in the substrate, filling the grooves with electrically conductive powder, and then applying heat and/or pressure to the substrate. The application of heat and/or pressure to the substrate causes the grooves to collapse inward against the conductive powder. Collapsing the grooves compacts the conductive powder within the groove, thereby establishing a continuously conductive grid line or circuit. The narrow grid lines that result allow more light to transmit through the substrate. The method allows grid lines to be made with higher aspect ratios (ratio of line depth to line width) than is possible by previous methods.

Claims

1. A method for fabricating a plurality of electrically conducting traces in a polymer substrate, the method comprising the steps of:

providing a polymer substrate;

forming a pattern of channels in a surface of the substrate;

placing conductive particles into the channels;

collapsing the sides of the channels inward against the conductive particles to form a conductive trace in the substrate.

2. The method of claim 1, wherein the conductive particles are metal.

3. The method of claim 1, wherein the conductive particles are organic.

4. The method of claim 1, wherein the conductive particles are inorganic.

5. The method of claim 1, wherein the conductive particles are photo-conductive.

6. The method of claim 5, wherein the photo-conductive particles are selenium.

7. The method of claim 1, wherein the polymer substrate is a thermoformable material.

8. The method of claim 1, wherein the polymer substrate is an elastomeric material.

9. The method of claim 1, wherein the step of forming a pattern of channels in the surface of the substrate includes deforming the substrate at a temperature below the glass transition of the substrate.

10. The method of claim 9, wherein the channels are formed with a triangular cross section.

11. The method of claim 9, wherein the step of collapsing the sides of the channels includes the step of applying force to the surface of the substrate.

12. The method of claim 9, wherein the step of collapsing the sides of the channels includes the step of applying heat to the surface of the substrate.

13. The method of claim 9, wherein the step of collapsing the sides of the channels includes the steps of applying force and heat to the surface of the substrate.

14. The method of claim 1, wherein the step of collapsing the sides of the channels includes the step of applying force to the surface of the substrate.

15. The method of claim 1, wherein the step of collapsing the sides of the channels includes the step of applying heat to the surface of the substrate.

16. The method of claim 1, wherein the step of collapsing the sides of the channels includes the steps of applying force and heat to the surface of the substrate.

17. The method of claim 2, further comprising the step of melting and coalescing the metal particles.

18. The method of claim 2, wherein the metal particles include dendritic particles.

19. The method of claim 2, wherein the particles are selected from the group of copper, tin, silver, lead, or bismuth.

20. The method of claim 1, wherein collapsing the side walls causes only a fraction of the particles to melt.

21. The method of claim 1, wherein the substrate is a fluoropolymer.

22. The method of claim 1, wherein the substrate is a perfluorinated polymer.

23. The method of claim 1, wherein the substrate is a partially fluorinated polymer.

24. The method of claim 1, wherein prior to collapsing the sides of the channels, the channels have a ratio of depth to width greater than 1.

25. The method of claim 1, wherein the channels are formed perpendicular to the surface of the substrate.

26. The method of claim 1, wherein the channels are formed at an angle of less than 90 degrees with the surface of the substrate.

27. The method of claim 1, wherein the particle size is in the range of 10-25% of the width of the channel.

28. The method of claim 1, wherein the trace is less than 2 microns wide.

29. The method of claim 1, wherein the trace has a ratio of depth to width of greater than 5.

30. The method of claim 1, wherein the trace has a ratio of depth to width of greater than 10.

31. The method of claim 1, further including the step of laminating a polymer cover layer over the patterned surface of the substrate after collapsing the sides of the channels.