Over-voltage protection device and method for making same

• US 6,172,590 B1
• Filed: 10/01/1997
• Issued: 01/09/2001
• Est. Priority Date: 01/22/1996
• Status: Expired due to Term

• Current Assignee: Littelfuse Incorporated
• Original Assignee: SurgX Corp. (Littelfuse Incorporated)
• Inventors: Olla, Mike, Shrier, Karen P., Intrater, James B., Joshi, Kailash C., Behling, Gerald R., Felps, Jimmie D.
• Primary Examiner(s): Bradley, Paula
• Assistant Examiner(s): Davis, Katrina
• Application Number:
  US08/941,917
• Time in Patent Office: 1,196 Days
• Field of Search: 361/111, 361/91.1, 257/355, 338/20, 338/21, 338/309, 439/86, 439/90, 439/91
• US Class Current: 338/20
• 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]

Abstract

A mass-producible, cost-effective discrete electrical protection device utilizing a precision gap between two electrically conductive members attached to an electrically insulating substrate to provide over-voltage protection to an electrical device. In one aspect, the electrical protection device is a surface mountable device. In another aspect, the device has through-holes for accommodating leads on an electrical connector. Methods are provided also for making the electrical protection device.

Claims

1. An electrical protection device comprising:

a substrate having a first surface and a second surface;

a first pad attached to the second surface of the substrate;

a second pad spaced from the first pad and attached to the second surface of the substrate;

a third pad attached to the first surface of the substrate and being in electrical communication with the first pad;

a fourth pad spaced from the third pad by a gap and attached to the first surface of the substrate, the fourth pad being in electrical communication with the second pad,

wherein the gap operates to substantially electrically isolate the fourth pad from the third pad except in the presence of an overvoltage event.

2. The electrical protection device of claim 1, wherein the space between the third pad and the fourth pad is 3.0 mils or less.

3. The electrical protection device of claim 1, wherein the space between the third pad and the fourth pad is 12 microns or less.

4. The electrical protection device of claim 1, wherein the space between the third pad and the fourth pad is in a range not greater than 3.0 mils and not less than 3 microns.

5. The electrical protection device of claim 1 further comprising a non-linear dielectric in the space between the third pad and the fourth pad.

6. The electrical protection device of claim 1 further comprising an non-linear resistance material in the space between the third pad and the fourth pad.

7. The electrical protection device of claim 6 further comprising a passivation layer extending over the non-linear resistance material and at least a portion of the third pad and the fourth pad.

8. An electrical protection device comprising:

a substrate having a first surface and a second surface;

a first pad attached to the second surface of the substrate;

a second pad spaced from the first pad and attached to the second surface of the substrate;

a third pad attached to the first surface of the substrate and being in electrical communication with the first pad; and

a fourth pad spaced from the third pad by a gap and attached to the first surface of the substrate, the fourth pad being in electrical communication with the second pad,

wherein the gap operates to substantially electrically isolate the fourth pad from the third pad except in the presence of an overvoltage event; and

wherein the electrical communications between the first pad and the third pad and the second pad and the fourth pad are through-holes in the substrate.

9. The electrical protection device of claim 8 wherein the through-holes are filled.

10. The electrical protection device of claim 8 wherein the substrate is an electrically insulating material from the group consisting of aluminum oxide, fire retardant grade 4 laminate, polyimide, bismaleimide triazine, high temperature epoxy or polyester.

11. The electrical protection device of claim 8 wherein the through-holes are plated.

12. The electrical protection device of claim 11 further comprising:

a trace extending from the fourth pad toward the third pad, a distal end of the trace being spaced from the third pad.

13. The electrical protection device of claim 12, wherein the space between the distal end of the trace and the third pad is 3.0 mils or less.

14. The electrical protection device of claim 12, wherein the space between the third pad and the distal end of the trace is 12 microns or less.

15. The electrical protection device of claim 11 further comprising:

a first trace extending from the third pad;

a second trace extending from the fourth pad, a distal end of the second trace being spaced from the first trace.

16. The electrical protection device of claim 15, wherein the space between the first trace and the distal end of the second trace is in a range not greater than 3.0 mils and not less than 3 microns.

17. The electrical protection device of claim 15 further comprising a non-linear resistance material in the space between the first trace and the distal end of the second trace.

18. A method for making at least one electrical protection device, comprising the steps of:

providing an electrically insulating substrate having electrically conductive layers on opposite sides thereof;

forming at least two through-holes in the electrically insulating substrate and the electrically conductive layers;

forming electrically conductive paths between the electrically conductive layers through the through-holes; and

forming electrically conductive pads around the through-holes, the electrically conductive pads being spaced from each other by at least one gap which operates to substantially electrically isolate a pair of conductive pads from each other except in the presence of an overvoltage event.

19. The method of claim 18 further comprising filling the space between the electrically conductive pads on one side of the electrically insulating substrate with a non-linear resistance material.

20. The method of claim 18 further comprising filling the space between the electrically conductive pads on one side of the electrically insulating substrate with a dielectric.

21. The method of claim 20 further comprising dividing the electrically insulating substrate having electrically conductive pads thereon into discrete devices having at least two electrically conductive paths between the electrically conductive layers.

22. The method of claim 21 wherein the electrically insulating substrate having electrically conductive pads thereon is divided between two adjacent through-holes.

23. A method for making at least one electrical protection device, comprising the steps of:

providing an electrically insulating substrate having electrically conductive layers on opposite sides thereof;

forming at least two through-holes in the electrically insulating substrate and the electrically conductive layers;

forming electrically conductive paths between the electrically conductive layers through the through-holes;

forming electrically conductive pads around the through-holes, the electrically conductive pads being connected by a trace; and

forming a gap in the trace, said gap operating to substantially electrically isolate a first portion of the trace from a second portion of the trace except in the presence of an overvoltage event.

24. The method of claim 23 wherein the gap is formed in the trace with a laser to produce a gap in a range not greater than 3.0 mils and not less than 3 microns.

25. The method of claim 23 further comprising filling the gap with a dielectric.

26. The method of claim 23 further comprising filling the gap with a non-linear resistance material.

27. The method of claim 23 further comprising forming a passivation layer over at least one side of the electrically insulating substrate having the trace thereon.

28. The method of claim 23 further comprising dividing the electrically insulating substrate having electrically conductive pads thereon into discrete devices having at least two electrically conductive paths between the electrically conductive layers.

29. The method of claim 23 further comprising forming a ground bar wherein the gap is formed in at least one trace connected to the ground bar.

30. The method of claim 29, wherein the gap is formed in the trace with a laser to a dimension in a range not greater than 3.0 mils and not less than 3 microns.

31. The method of claim 29 further comprising filling the gap with a dielectric.

32. The method of claim 29 further comprising filling the gap with a non-linear resistance material.

33. The method of claim 29 further comprising forming a passivation layer over at least one side of the electrically insulating substrate having the trace thereon.

34. The method of claim 29 further comprising dividing the electrically insulating substrate having electrically conductive pads thereon into discrete devices having at least two electrically conductive paths between the electrically conductive layers.