Voltage variable material for direct application and devices employing same

• US 20030218851A1
• Filed: 04/08/2003
• Published: 11/27/2003
• Est. Priority Date: 04/08/2002
• Status: Active Grant

• Current Assignee: Littelfuse Incorporated
• Original Assignee: Littelfuse Incorporated
• Inventors: Perry, David, Davidson, Scott, Whitney, Stephen J., Harris, Edwin James
• Granted Patent: US 7,202,770 B2
• Time in Patent Office: Days
• US Class Current: 361/118
• 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 electrical circuit comprising:

a substrate;

a plurality of electrodes secured to the substrate and separated by at least one gap; and

a quantity of a voltage variable material (“

VVM”

) intrinsically secured, without a covering, to the electrodes and to the substrate across the gap.

2. The circuit of claim 1, wherein the substrate includes a material chosen from the group consisting of:

rigid laminate;

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

3. The circuit of claim 1, wherein the circuit is provided in a piece of electrical equipment.

4. The circuit of claim 3, wherein the electrical equipment is a connector.

5. The circuit of claim 1, wherein the VVM includes an insulative binder that provides the self-securing property plus a material chosen from the group consisting of:

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

6. The circuit of claim 5, wherein the conductive particles individually include an inner core and an outer shell.

7. An electrical circuit comprising:

a substrate;

a quantity of a voltage variable material (“

VVM”

) in a self-curable form intrinsically secured, without a covering, to the substrate; and

a plurality of electrodes separated by at least one gap contacting the VVM.

8. The circuit of claim 7, wherein the substrate includes a material chosen from the group consisting of:

rigid laminate;

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

9. The circuit of claim 7, wherein the circuit is provided in a piece of electrical equipment.

10. The circuit of claim 9, wherein the equipment includes one of:

a telecommunications device and an input/output connector.

11. The circuit of claim 7, wherein the VVM includes an insulative binder that provides the self-securing property plus a material chosen from the group consisting of:

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

12. The circuit of claim 11, wherein the conductive particles individually include an inner core and an outer shell.

13. An electrical circuit comprising:

a substrate;

a plurality of electrodes secured to the substrate and separated by at least one gap; and

a quantity of a voltage variable material (“

VVM”

) in a self-curable form intrinsically secured, without a covering, to the electrodes.

14. The circuit of claim 13, wherein the substrate includes a material chosen from the group consisting of:

rigid laminate;

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

15. The circuit of claim 13, wherein the circuit is provided in a piece of electrical equipment.

16. The circuit of claim 15, wherein the equipment is a connector.

17. The circuit of claim 13, wherein the VVM includes an insulative binder that provides the self-securing property plus a material chosen from the group consisting of:

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

18. The circuit of claim 17, wherein the conductive particles individually include an inner core and an outer shell.

19. An electrical circuit comprising:

a substrate;

first and second electrodes separated by a gap, the first electrode secured to the substrate; and

a quantity of a voltage variable material (“

VVM”

) that includes a polymeric self-curable insulative binder, the quantity intrinsically secured to the first and second electrodes.

20. The electrical circuit of claim 19, wherein the VVM quantity is self-secured to the first and second electrodes and the substrate.

21. The electrical circuit of claim 19, which includes a coating that covers the first and second electrodes.

22. The electrical circuit of claim 21, wherein the substrate, electrodes and coating form part of a multi-layered printed circuit board.

23. The electrical circuit of claim 19, wherein the first and second electrodes are secured to the substrate.

24. The electrical circuit of claim 23, which includes a third electrode placed onto the VVM and spaced apart from the first and second electrodes.

25. The electrical circuit of claim 24, wherein the third electrode is spaced closer to the first and second electrodes than the first and second electrodes are spaced with respect to each other.

26. The electrical circuit of claim 23, which includes a coating that covers the first and second electrodes.

27. The electrical circuit of claim 23, wherein one of the first and second electrodes is a ground electrode.

28. The electrical circuit of claim 23, wherein the substrate is a first substrate and which includes a second substrate, and wherein the first and second electrodes are disposed between the first and second substrates.

29. The electrical circuit of claim 28, wherein the first and second substrates are layers of a multi-layered printed circuit board or a flexible circuit.

30. The electrical circuit of claim 19, wherein the substrate is a first substrate and which includes a second substrate, and wherein the second electrode is secured to the second substrate.

31. The electrical circuit of claim 30, wherein the first and second substrates are layers of a multi-layered printed circuit board or a flexible circuit.

32. An electrical circuit comprising:

a substrate;

first and second electrodes separated by a gap, the first electrode secured to the substrate; and

a quantity of voltage variable material (“

VVM”

) that includes a polymeric insulative binder that has been dissolved in a solvent and thickened with an agent, the quantity secured to the first and second electrodes.

33. The electrical circuit of claim 32, wherein the insulative binder is self-curable.

34. The electrical circuit of claim 32, wherein the solvent includes carbitol acetate.

35. The electrical circuit of claim 32, wherein the agent includes a fumed silica.

36. The electrical circuit of claim 32, wherein the VVM includes conductive particles having an aluminum core and an aluminum oxide shell.

37. An electrical device comprising:

first and second signal conductors;

a shield; and

at least one tab defined by the shield, the at least one tab biased towards the first and second conductors; and

at least one quantity of voltage variable material (“

VVM”

) disposed between the first and second signal conductors and the at least one tab.

38. The device of claim 37, which includes first and second tabs defined by the shield, wherein a first quantity of VVM is disposed between the first signal conductor and the first tab and a second quantity of VVM is disposed between the second signal conductor and the second tab.

39. The device of claim 37, which includes a capacitor disposed between the first signal conductor and the at least one tab.

40. The device of claim 37, wherein the VVM includes a self-curable insulative binder.

41. The device of claim 37, wherein the VVM is intrinsically adhered to at least one of the conductors and the at least one tab.