Voltage variable material for direct application and devices employing same

• US 7,202,770 B2
• Filed: 04/08/2003
• Issued: 04/10/2007
• Est. Priority Date: 04/08/2002
• Status: Active Grant

• Current Assignee: Littelfuse Incorporated
• Original Assignee: Littelfuse Incorporated
• Inventors: Davidson, Scott, Perry, David, Harris, Edwin James, Whitney, Steven J.
• Primary Examiner(s): HOANG, TU BA
• Application Number:
  US10/410,393
• Publication Number:
  US 20030218851A1
• Time in Patent Office: 1,463 Days
• Field of Search: 338/20, 338/21, 338/13, 338/22.R, 338/221, 338/260, 361/56, 361/126, 361/127
• US Class Current: 338/21
• CPC Class Codes: H01L 23/62 Protection against overvoltage, e.g. fuses, shunts
• 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: H01L 2924/09701 Low temperature co-fired ceramic [LTCC]
• CPC Class Codes: H01L 2924/12044 OLED
• CPC Class Codes: H01L 2924/3011 Impedance
• CPC Class Codes: H02H 9/044 Physical layout, materials not provided for elsewhere varistors H01C7/12; spark-gaps H01T; Ovshinsky devices H10N70/00
• CPC Class Codes: H05K 1/0257 Overvoltage protection
• CPC Class Codes: H05K 1/0259 Electrostatic discharge [ESD] protection
• CPC Class Codes: H05K 1/0298 Multilayer circuits
• CPC Class Codes: H05K 1/167 incorporating printed resistors
• CPC Class Codes: H05K 2201/0738 Use of voltage responsive materials, e.g. voltage switchable dielectric or varistor materials

Abstract

The present invention provides overvoltage circuit protection. Specifically, the present invention provides a voltage variable material (“VVM”) that includes an insulative binder that is formulated to intrinsically adhere to conductive and nonconductive surfaces. The binder and thus the VVM is self-curable and may be applied to an application in the form of an ink, which dries in a final form for use. The binder eliminates the need to place the VVM in a separate device or for separate printed circuit board pads on which to electrically connect the VVM. The binder and thus the VVM can be directly applied to many different types of substrates, such as a rigid (FR-4) laminate, a polyimide or a polymer. The VVM can also be directly applied to different types of substrates that are placed inside a device.

Claims

1. An overvoltage protection circuit comprising:

a printed circuit board having a substrate surface;

an electrical circuit formed on the substrate surface, the electrical circuit including;

a plurality of electrode pairs formed along the electrical circuit;

a gap formed between each of the plurality of electrode pairs; and

a voltage variable layer including a self-curing adhesive binder configured to adhere to the substrate surface, the voltage variable layer applied to contact each of the plurality of electrode pairs across each corresponding gap;

wherein the voltage variable layer is directly applied to the surface of the substrate by way of an ink that dries to its final form.

2. The circuit of claim 1, wherein the printed circuit board is a flexible circuit board.

3. The circuit of claim 1, wherein the printed circuit board includes at least two layers.

4. The circuit of claim 1, wherein the printed circuit board is manufactured from a material chosen from the group consisting of:

rigid laminate, polyimide, polymer, glass, ceramic and any combination thereof.

5. The circuit of claim 1, wherein the printed circuit board is configured to cooperate with a piece of electrical equipment.

6. The circuit of claim 5, wherein the electrical equipment is a connector.

7. The circuit of claim 1, wherein the self-curing adhesive binder is an insulative binder that supports a material chosen from the group consisting of:

conductive particles, insulating particles, semiconductive particles, doped semiconductive particles and any combination thereof.

8. The circuit of claim 7, wherein the conductive particles individually include an inner core and an outer shell.

9. A protection circuit comprising:

a printed circuit board having a layered substrate;

a plurality of electrical circuits having a plurality of electrodes pairs each separated by a gap, the plurality of electrical circuits disposed on the layered substrate; and

a voltage variable layer having an adhesive binder, the voltage variable layer adhered adjacent to each of the gaps corresponding to each of the electrodes pairs and applied to contact each of the plurality of electrode pairs across each corresponding gap;

wherein the voltage variable layer is directly applied to the layered substrate by way of an ink that dries to its final form.

10. The circuit of claim 9, wherein the printed circuit board is a flexible circuit board.

11. The circuit of claim 9, wherein the printed circuit board is manufactured from a material chosen from the group consisting of:

rigid laminate, polyimide, polymer, glass, ceramic and any combination thereof.

12. The circuit of claim 9, wherein the printed circuit board is adapted to cooperate with a piece of electrical equipment.

13. The circuit of claim 12, wherein the piece of electrical equipment includes one of:

a telecommunications device and an input/output connector.

14. The circuit of claim 9, wherein the adhesive binder is an insulative binder that provides the self-curing property and supports a material chosen from the group consisting of:

conductive particles, insulating particles, semiconductive particles, doped semiconductive particles and any combination thereof.

15. The circuit of claim 14, wherein the conductive particles individually include an inner core and an outer shell.

16. A printed circuit board assembly comprising:

a circuit board substrate having a substrate surface;

an electrical circuit disposed on the substrate surface, wherein the electrical circuit includes;

a first electrode;

a second electrode; and

a gap separating the first electrode from the second electrode;

a voltage variable layer applied to the gap defined within the electrical circuit and configured to contact the first and second electrodes, the voltage variable layer including a polymeric self-curable insulative binder;

wherein the voltage variable layer is directly applied to the surface of the substrate by way of an ink that dries to its final form.

17. The assembly of claim 16, wherein the polymeric self-curable insulative binder is an adhesive binder.

18. The assembly of claim 16, further comprising a coating that covers the first and second electrodes.

19. The assembly of claim 16, wherein the circuit board substrate and the first and second electrodes form part of a multi-layered printed circuit board.

20. The assembly of claim 16, wherein the circuit board substrate is a flexible substrate.

21. The assembly of claim 16, wherein one of the first and second electrodes is a ground electrode.

22. A protection circuit comprising:

a circuit board substrate having a substrate surface;

a plurality of electrical circuits disposed on the substrate surface, each of the plurality of electrical circuits including;

a first electrode;

a second electrode; and

a gap separating the first electrode from the second electrode;

a voltage variable layer including a polymeric adhesive binder that has been dissolved in a solvent and thickened with an agent, the voltage variable layer applied directly to the substrate surface as an ink that dries to its final form and contacts the first and second electrodes.

23. The assembly of claim 22, wherein the polymeric adhesive binder is self-curable.

24. The assembly of claim 22, wherein the solvent includes carbitol acetate.

25. The assembly of claim 22, wherein the agent includes a fumed silica.

26. The assembly of claim 22, wherein the voltage variable layer includes conductive particles having an aluminum core and an aluminum oxide shell.