PTC electrical device having fuse link in series and metallized ceramic electrodes

• US 5,663,702 A
• Filed: 06/07/1995
• Issued: 09/02/1997
• Est. Priority Date: 06/07/1995
• Status: Expired due to Term

• Current Assignee: Littelfuse Incorporated
• Original Assignee: Littelfuse Incorporated
• Inventors: Stein, Paul Charles, Shaw, Philip C. Jr.
• Primary Examiner(s): Phillips, Michael W.
• Assistant Examiner(s): Gandhi, Jayprakash N.
• Application Number:
  US08/476,094
• Time in Patent Office: 818 Days
• Field of Search: 337/102, 337/107, 337/140, 337/232, 337/401-405, 337/142, 337/182, 337/183, 337/184, 338/22 R
• US Class Current: 337/183
• CPC Class Codes: H01C 1/1406 Terminals or electrodes formed on resistive elements having positive temperature coefficient
• CPC Class Codes: H01C 7/027 consisting of conducting or semi-conducting material dispersed in a non-conductive organic material
• CPC Class Codes: H01H 2085/0483 with temperature dependent resistor, e.g. thermistor
• CPC Class Codes: H01H 85/463 with printed circuit fuse

Abstract

Electrical devices with a PTC element including a polymer having conductive particles dispersed therein and at least one metallized ceramic electrode. The devices are made by dispersing conductive particles into a polymer to form a polymer PTC composition. The metallized ceramic electrodes include a ceramic substrate having a conductive layer deposited on its surface. The metallized ceramic electrodes are brought into contact with the PTC element, and heated while applying pressure to form a laminate. The laminate is then diced into a plurality of PTC electrical circuit protection devices.

Claims

1. An electrical fuse assembly including a plurality of electrical circuit protection devices which can be used to protect a number of electrical circuits, the fuse assembly comprising:

a first and second substrate, each substrate having an inner surface and an outer surface;

a plurality of conductive terminal pads deposited on the outer surfaces of the first and second substrates;

a plurality of fuse links deposited on the outer surface of the first substrate;

a plurality of first conductive layers deposited on the inner surface of the first substrate;

a plurality of second conductive layers deposited on the inner surface of the second substrate;

a plurality of PTC elements interposed between the first and second substrates, each PTC element in electrical contact with a single first conductive layer and a single second conductive layer, each PTC element also electrically connected in series with a single fuse link; and

,

the PTC elements electrically insulated from one another by a plurality of dividing substrates.

2. An electrical fuse assembly according to claim 1, wherein the first and second substrate comprise ceramic.

3. An electrical fuse assembly according to claim 1, wherein the first and second substrate are comprised of a material selected from the group consisting essentially of alumina, silica, beryllia, and aluminum nitride.

4. An electrical fuse assembly according to claim 1, wherein the first and second substrate are comprised of glass and ceramic.

5. An electrical fuse assembly according to claim 1, wherein the plurality of first and second conductive layers comprise a conductive thick film ink.

6. An electrical fuse assembly according to claim 1, wherein the plurality of first and second conductive layers comprise a metal selected from the group consisting essentially of silver, copper, zinc, nickel, gold, palladium, and platinum.

7. The electrical device of claim 1, wherein the device has an electrical resistance at approximately 25°

C. of less than 1 ohm.

8. The electrical device of claim 1, wherein the device has an electrical resistance at approximately 25°

C. of less than 0.5 ohm.

9. The electrical device of claim 1, wherein the device has an electrical resistance at approximately 25°

C. of less than 0.1 ohm.

10. An electrical device comprising:

a first and second laminar substrate, each laminar substrate having an inner surface and an outer surface;

at least one conductive terminal pad deposited on the outer surface of the first laminar substrate;

at least two conductive terminal pads deposited on the outer surface of the second laminar substrate;

a fuse link electrically connecting the two conductive terminal pads deposited on the second laminar substrate, the entire fuse link being deposited on the outer surface of the second laminar substrate;

first and second conductive layers deposited on the inner surfaces of the first and second laminar substrates, respectively;

the first conductive layer electrically connected to at least one conductive terminal pad deposited on the outer surface of the first laminar substrate and the second conductive layer electrically connected to only one terminal pad deposited on the outer surface of the second laminar substrate; and

a PTC element interposed between the first and second substrates and in electrical contact with the first and second conductive layers such that the PTC element is electrically connected in series with the fuse link.

11. The electrical device of claim 10, wherein the first and second laminar substrates comprise ceramic.

12. The electrical device of claim 10, wherein the first and second laminar substrates are comprised of a material selected from the group consisting essentially of alumina, silica, beryllia and aluminum nitride.

13. The electrical device of claim 10, wherein the first and second laminar substrates comprise a glass-ceramic material.

14. The electrical device of claim 10, wherein the first and second conductive layers comprise a polymer thick film ink.

15. The electrical device of claim 10, wherein the first and second conductive layers comprise a metal selected from the group consisting essentially of silver, copper, zinc, nickel, gold, palladium and platinum.

16. An electrical device comprising:

a PTC element composed of a polymer having electrically conductive particles dispersed therein;

at least one metallized ceramic electrode; and

,

a fuse link electrically connected in series with the PTC element, the entire fuse link deposited on the metallized ceramic electrode.

17. An electrical device according to claim 16, wherein the metallized ceramic electrode has a pair of conductive terminal pads deposited on its surface, the conductive terminal pads electrically connected by the fuse link.

18. An electrical device according to claim 16, wherein the metallized ceramic electrode comprises a ceramic substrate having a conductive layer deposited on its surface.

19. An electrical device according to claim 16, wherein the metallized ceramic electrode comprises a ceramic substrate and a layer of conductive thick film ink.

20. An electrical device according to claim 16, wherein the metallized ceramic electrode comprises a material selected from the group consisting of alumina, silica, beryllia, and aluminum nitride.

21. An electrical device according to claim 16, wherein the metallized ceramic electrode comprises glass and ceramic.

22. An electrical device according to claim 16, wherein the metallized ceramic electrode comprises a ceramic substrate composed of Al₂ O₃, a layer of conductive thick film ink, and a layer of conductive particles.