Surface mountable electrical device comprising a PTC and fusible element

• US 6,023,403 A
• Filed: 11/26/1997
• Issued: 02/08/2000
• Est. Priority Date: 05/03/1996
• Status: Expired due to Fees

• Current Assignee: Littelfuse Incorporated
• Original Assignee: Littlefuse Incorporated
• Inventors: McGuire, Katherine M., Luciano, Honorio
• Primary Examiner(s): SHERRY, MICHAEL JUDE
• Application Number:
  US08/978,657
• Time in Patent Office: 804 Days
• Field of Search: 361/103, 361/104, 361/106, 361/111, 361/58, 338/22 R, 337/142
• US Class Current: 361/106
• CPC Class Codes: H01C 1/1406 Terminals or electrodes formed on resistive elements having positive temperature coefficient
• CPC Class Codes: H01C 1/142 the terminals or tapping points being coated on the resistive element
• CPC Class Codes: H01C 7/027 consisting of conducting or semi-conducting material dispersed in a non-conductive organic material
• CPC Class Codes: H01H 2085/0414 Surface mounted fuses
• CPC Class Codes: H01H 2085/0483 with temperature dependent resistor, e.g. thermistor
• CPC Class Codes: H01H 85/0411 Miniature fuses

Abstract

The present invention is a device for protecting an electrical circuit. The device includes a resistive element having a first and a second surface. A first electrode is in electrical contact with the first surface of the resistive element and a second electrode is in electrical contact with the second surface of the resistive element. A first end termination electrically connects the circuit and the first electrode. A second end termination electrically connects the second electrode and the circuit. An electrically insulating layer is interposed between the first and second end terminations and is in contact with the first and second electrodes. The end terminations allow for an electrical connection to be made to both electrodes from the same side of the electrical device.

Claims

1. A device for protecting an electrical circuit comprising:

a resistive element having a first and a second surface connected to a first and a second side wall;

a first electrode disposed on the first surface of the resistive element and a second electrode disposed on the second surface of the resistive element;

a first end termination wrapping around the first side wall of the resistive element and electrically connecting the circuit and the second electrode;

a second end termination wrapping around the second side wall of the resistive element and electrically connecting the first electrode and the circuit; and

an electrically insulating layer disposed on the first and second electrodes and interposed between the first end termination and the first electrode and interposed between the second end termination and the second electrode.

2. The device of claim 1, wherein the resistive element exhibits PTC behavior.

3. The device of claim 1, wherein the resistive element is comprised of a conductive polymer.

4. The device of claim 1, wherein the electrically insulating layer is in contact with the first and the second surfaces of the resistive element.

5. The device of claim 1, wherein first end termination is disposed on a portion of the first and second surfaces of the resistive element.

6. The device of claim 1, wherein the first end termination is in direct physical contact with the second electrode.

7. The device of claim 1, wherein the second end termination is in direct physical contact with the first electrode.

8. The device of claim 1, wherein the first end termination is disposed on the first side wall and the second end termination is disposed on the second side wall.

9. The device of claim 1, wherein the first and second end terminations are comprised of a first and a second conductive layer, respectively.

10. The device of claim 9, wherein the first conductive layer comprises a metal selected from the group consisting of tin, silver, copper, nickel, gold and alloys thereof.

11. The device of claim 9, wherein the second conductive layer comprises tin.

12. The device of claim 9, wherein the first conductive layer comprises copper and the second conductive layer comprises solder.

13. The device of claim 1, wherein the electrically insulating layer comprises a material selected from the group consisting of photo resist, dielectric, ceramic and solder mask.

14. The electrical device of claim 1, wherein the electrodes comprise a metallic foil.

15. A device for protecting an electrical circuit comprising:

a PTC element having a first and a second surface connected to a first and a second side wall;

a first electrode disposed on the first surface of the PTC element and a second electrode disposed on the second surface of the PTC element;

a first end termination wrapping around the first side wall of the PTC element and providing electrical connection between the circuit and the second electrode;

a first electrically insulating layer disposed on the first electrode;

a fusible element disposed on the first insulating layer, the fusible element electrically connected in series with the PTC element; and

a second end termination wrapping around the second side wall of the PTC element and providing electrical connection between the fusible element and the circuit.

16. The device of claim 15, wherein the PTC element is comprised of a conductive polymer.

17. The device of claim 15 further including a conductive member electrically connecting the PTC element with the fusible element.

18. The device of claim 17, wherein the fusible element is in direct contact with the conductive member and the second end termination.

19. The device of Claim 15, wherein the first electrically insulating layer comprises a main portion and a sub-portion, and a conductive member electrically connects the resistive element and the fusible element through an opening in the first electrically insulating layer at a point intermediate the sub-portion and the main portion of the first electrically insulating layer.

20. The device of Claim 15 further including a second electrically insulating layer disposed on the second electrode.

21. The device of claim 20, wherein the second electrically insulating layer acts as a barrier to direct current flow from the second electrode to the second end termination.

22. The device of claim 20, wherein the second electrically insulating layer comprises a material selected from the group consisting of photo resist, dielectric, ceramic and solder mask.

23. The device of claim 15 further including a protective layer covering the fusible element.

24. The device of claim 15, wherein the first and second end terminations are comprised of a first and a second conductive layer, respectively.

25. The device of claim 24, wherein the first conductive layer comprises a metal selected from the group consisting of tin, silver, copper, nickel, gold and alloys thereof.

26. The device of claim 24, wherein the second conductive layer comprises tin.

27. The device of claim 26, wherein the first conductive layer comprises copper and the second conductive layer comprises solder.

28. The device of claim 15, wherein the first electrically insulating layer comprises a material selected from the group consisting of photo resist, dielectric, ceramic and solder mask.

29. A device for protecting an electrical circuit comprising:

a conductive polymer PTC element having a first and a second surface and a first and a second side wall;

a first electrode in electrical contact with the first surface of the PTC element and a second electrode the second surface of the PTC element;

a first end termination disposed on the first side wall of the PTC element and electrically connecting the circuit and the first electrode;

a second end termination disposed on the second side wall of the PTC element and electrically connecting the second electrode and the circuit; and

an electrically insulating layer disposed on the first and second electrodes and creating a physical barrier between the second end termination and the first electrode and a physical barrier between the first end termination and the second electrode.

30. An electrical device for protecting a circuit comprising:

a conductive polymer PTC element having a first and a second surface and a first and a second side wall;

a first electrode in electrical contact with the first surface of the PTC element and a second electrode in electrical contact with the second surface of the PTC element;

a first end termination disposed on the first side wall of the PTC element and providing an electrical connection between the circuit and the first electrode;

a fusible element electrically connected in series with the PTC element; and

a second end termination disposed on the second side wall of the PTC element and providing an electrical connection between the fusible element and the circuit.