Reflowable thermal fuse

Patent metadata

Field	Value
Publication number	US-10446345-B2
Application number	US-201815865698-A
Country	US
Kind code	B2
Filing date	Jan 9, 2018
Priority date	Jan 9, 2018
Publication date	Oct 15, 2019
Grant date	Oct 15, 2019

Abstract

A reflowable thermal fuse including a fuse body, a conductive composite element disposed within the fuse body, first and second conductive terminals connected to the conductive composite element and extending out of the fuse body, a removable barrier covering a surface of the conductive composite element and in electrical communication with the first and second conductive terminals, and a solvent element disposed on the removable barrier and separated from the conductive composite element by the removable barrier, wherein the removable barrier has a fusing temperature that is greater than a reflow temperature of the reflowable thermal fuse.

First claim

The invention claimed is:

1. A reflowable thermal fuse comprising:
a fuse body;
a conductive composite element disposed within the fuse body;
first and second conductive terminals connected to the conductive composite element and extending out of the fuse body;
a removable barrier covering a surface of the conductive composite element and in electrical communication with the first and second conductive terminals; and
a solvent element disposed on the removable barrier and separated from the conductive composite element by the removable barrier.

2. The reflowable thermal fuse of claim 1 , wherein the removable barrier has a fusing temperature that is greater than a reflow temperature of the reflowable thermal fuse.

3. The reflowable thermal fuse of claim 1 , wherein the solvent element is formed of a precision melting organic compound (PMOC).

4. The reflowable thermal fuse of claim 3 , wherein the PMOC includes at least one of bisphenol A, triphenylene, tetrabromobisphenol A, bisphenol S, Bisphenol P, 4,4′-Sulfonyldiphenol, 4-Hydroxybenzaldehyde, 4-Nitroaniline, 4-Aminobenzoic acid, 4-Nitrophenol, Resorcinol, Benzoin, and Aspartic acid.

5. The reflowable thermal fuse of claim 1 , wherein the conductive composite element is formed of a positive temperature coefficient (PTC) material including conductive particles suspended in a polymer matrix.

6. The reflowable thermal fuse of claim 1 , wherein the conductive composite element is adapted to absorb the solvent element to cause a resistance of the conductive composite element to increase.

7. The reflowable thermal fuse of claim 1 , wherein the solvent element is adapted to melt upon the occurrence of an overcurrent condition in the reflowable thermal fuse.

8. The reflowable thermal fuse of claim 1 , wherein the removable barrier is adapted to fuse upon the occurrence of an overcurrent condition in the reflowable thermal fuse, whereby the solvent element is allowed to come into contact with the conductive composite element.

9. The reflowable thermal fuse of claim 1 , wherein the removable barrier is a laminar element formed of a layer of copper disposed on a layer of polyimide.

10. The reflowable thermal fuse of claim 1 , wherein the removable barrier is a first removable barrier covering a first surface of the conductive composite element and wherein the solvent element is a first solvent element, the reflowable thermal fuse further comprising:
a second removable barrier covering a second surface of the conductive composite element opposite the first surface, the second solvent element disposed on the second removable barrier and separated from the conductive composite element by the second removable barrier.

11. A reflowable thermal fuse comprising:
a fuse body;
a conductive composite element disposed within the fuse body;
first and second conductive terminals connected to the conductive composite element and extending out of the fuse body;
a substrate covering a surface of the conductive composite element and having an opening formed therein;
a removable barrier disposed on the substrate and having a fusible area bridging the opening, the removable barrier disposed in electrical communication with the first and second conductive terminals;
a solvent element disposed on the removable barrier and separated from the conductive composite element by the removable barrier; and
a biasing element biasing the substrate and the removable barrier against the solvent element;
wherein the removable barrier is adapted to be fused at the fusible area when subjected to a predetermined activation current.

12. The reflowable thermal fuse of claim 11 , wherein the removable barrier has a fusing temperature that is greater than a reflow temperature of the reflowable thermal fuse.

13. The reflowable thermal fuse of claim 11 , wherein the solvent element is formed of a precision melting organic compound (PMOC).

14. The reflowable thermal fuse of claim 13 , wherein the PMOC includes at least one of bisphenol A, triphenylene, tetrabromobisphenol A, bisphenol S, Bisphenol P, 4,4′-Sulfonyldiphenol, 4-Hydroxybenzaldehyde, 4-Nitroaniline, 4-Aminobenzoic acid, 4-Nitrophenol, Resorcinol, Benzoin, and Aspartic acid.

15. The reflowable thermal fuse of claim 11 , wherein the conductive composite element is formed of a positive temperature coefficient (PTC) material including conductive particles suspended in a polymer matrix.

16. The reflowable thermal fuse of claim 11 , wherein the conductive composite element is adapted to absorb the solvent element to cause a resistance of the conductive composite element to increase.

17. The reflowable thermal fuse of claim 11 , wherein the solvent element is adapted to melt and to flow through the removable barrier and through the opening in the substrate upon the occurrence of an overcurrent condition in the reflowable thermal fuse.

18. The reflowable thermal fuse of claim 11 , wherein the removable barrier is a laminar element formed of a layer of copper disposed on a layer of polyimide.

19. The reflowable thermal fuse of claim 11 , wherein the opening in substrate comprises a plurality of opening in the substrate, and the fusible area of the removable barrier comprises a plurality of fusible areas bridging respective ones of the openings in the substrate.

20. The reflowable thermal fuse of claim 11 , wherein the biasing element comprises a coil spring extending through the conductive composite element.

Assignees

• Littelfuse Inc

Inventors

• Galla Matthew P
• Chen Jianhua

Classifications

• H01C7/027

  consisting of conducting or semi-conducting material dispersed in a non-conductive organic material · CPC title

• H01C7/02

  having positive temperature coefficient · CPC title

• H01C1/08 Primary

  Cooling, heating or ventilating arrangements · CPC title

• H02H3/085

  making use of a thermal sensor, e.g. thermistor, heated by the excess current (also responsive to the temperature of the protected device H02H5/041, thermal images H02H6/00) · CPC title

• H01H85/1755

  composite casing · CPC title