INTEGRATED THERMISTOR AND METALLIC ELEMENT DEVICE AND METHOD

• US 20090027821A1
• Filed: 07/26/2007
• Published: 01/29/2009
• Est. Priority Date: 07/26/2007
• Status: Abandoned Application

• Current Assignee: Littelfuse Incorporated
• Original Assignee: Littelfuse Incorporated
• Inventors: Whitney, Stephen, Yaosheng, Du, Colby, James A.
• Application Number:
  US11/828,844
• Publication Number:
  US 20090027821A1
• Time in Patent Office: Days
• US Class Current: 361/104
• CPC Class Codes: H01C 7/02 having positive temperature coefficient ceramics C04B
• 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 85/0418 with ferrule type end contacts
• CPC Class Codes: H01H 85/046 Fuses formed as printed circuits
• CPC Class Codes: H01H 85/048 Fuse resistors
• CPC Class Codes: H02H 5/048 additionally responsive to excess current due to heating of the switch
• CPC Class Codes: H03K 17/687 the devices being field-effect transistors
• CPC Class Codes: H03K 17/72 having more than two PN junctions; having more than three electrodes; having more than one electrode connected to the same conductivity region
• CPC Class Codes: H03K 17/74 by the use, as active elements, of diodes by the use of more than one type of semiconductor device H03K17/567; by the use of tunnel diodes H03K17/58; by the use of negative resistance diodes H03K17/70

Abstract

A circuit protection device includes a fuse element placed in parallel with a PTC thermistor layer. The element and PTC thermistor layer are provided on one or more insulating substrate, such as an FR-4 or polyimide substrate. First and second conductors connect the fuse element and PTC thermistor layer electrically in parallel, such that current (i) initially under normal flows mainly through the fuse element and PTC thermistor layer at a lower drop in voltage and (ii) after an opening of the fuse element flows under normal operation through the PTC thermistor layer at a higher drop in voltage.

Claims

1. A circuit protection device comprising:

an electrically insulating substrate;

a fuse element located on the substrate;

a positive temperature coefficient (“

PTC”

) thermistor layer connected to the substrate the fuse element having a lower resistance than the PTC thermistor layer, and

first and second conductors connected electrically to the fuse element and the PTC thermistor layer in parallel, such that current (i) initially under normal operation flows through the fuse element and the PTC thermistor layer and (ii) after an opening of the fuse element flows under normal operation through the PTC thermistor layer.

2. The circuit protection device of claim 1, wherein the fuse element and PTC thermistor layer have at least similar current ratings.

3. The circuit protection device of claim 1, wherein the fuse element is of at least one a type selected from the group consisting of:

(i) a wire, (ii) surface mounted, (iii) of a single metal, and (iv) of multiple metals.

4. The circuit protection device of claim 1, wherein the first and second terminals include at least one attribute selected from the group consisting of:

(i) first and second end terminations, (ii) extend onto first and second sides of the electrically insulating substrate, and (iii) are made of different metals.

5. The circuit protection device of claim 1, wherein the fuse element and PTC thermistor layer are located on opposite sides of the insulating substrate.

6. The circuit protection device of claim 1, wherein the substrate is made of a material selected from the group consisting of:

FR-4, polyimide and glass.

7. The circuit protection device of claim 1, the PTC thermistor layer being of a type selected from the group consisting of:

polymeric and ceramic.

8. The circuit protection device of claim 1, which includes a plurality of insulating substrates and a plurality of the PTC thermistor layers.

9. The circuit protection device of claim 8, wherein the first and second conductors are each connected electrically to each of the PTC thermistor layers.

10. A circuit protection device comprising:

a first electrically insulting substrate;

a fuse element located on a first side of the first insulating substrate;

a first positive temperature coefficient (“

PTC”

) thermistor layer having a first side contacting a second side of the first substrate;

a second electrically insulating substrate having a first side contacting a second side of the first PTC thermistor layer;

a second PTC thermistor layer contacting a second side of the second insulating substrate; and

first and second conductors connected electrically in parallel to the fuse element and the first and second PTC thermistor layers.

11. The circuit protection device of claim 10, the fuse element having at least one attribute selected from the group consisting of:

(i) being a surface mount element;

(ii) having dissimilar metals;

(iii) being of a wire bond type; and

(iv) having a rating at least similar to that of a collective rating of the first and second PTC thermistor layers.

12. The circuit protection device of claim 10, which includes a third electrically insulating substrate, the second PTC thermistor layer having a first side contacting the second side of the second insulating substrate and a second side contacting the third electrically insulating substrate.

13. The circuit protection device of claim 10, wherein the first and second conductors each include at least one electrode contacting the fuse element and the first and second PTC thermistor layers.

14. The circuit protection device of claim 10, wherein each of the first and second conductors includes an electrode extending at least halfway across one of the first and second PTC thermistor layers.

15. The circuit protection device of claim 14, wherein the first and second conductors each include at least one end cap metallization contacting the electrodes.

16. A circuit protection device comprising:

a ceramic positive temperature coefficient (“

CPTC”

) thermistor layer;

a fuse element carried by the CPTC thermistor layer, the fuse element having a lower resistance than the CPTC thermistor layer; and

first and second conductors connected electrically to the fuse element and CPTC thermistor layer in parallel, such that current (i) initially under normal operation flows through the fuse element and the CPTC thermistor layer and (ii) after an opening of the fuse element flows under normal operation through the CPTC thermistor layer.

17. The circuit protection device of claim 16, wherein the fuse element is a surface mount fuse element applied to the CPTC thermistor layer.

18. The circuit protection device of claim 16, wherein the fuse element is a wire element affixed to electrodes applied to the CPTC thermistor layer.

19. A circuit protection method comprising:

protecting a first electrical pathway in a device with a non-resettable fusing apparatus having a relatively lower electrical resistance; and

protecting a second electrical pathway in the device, and in parallel with the first electrical pathway, with a resettable fusing apparatus having a relatively higher electrical resistance, such that current (i) initially under normal operation flows through both the resettable and non-settable fusing apparatuses at a lower drop in voltage, and (ii) after an opening of the non-resettable fusing apparatus flows under normal operation through the resettable fusing apparatus at a higher drop in voltage.

20. The circuit protection method of claim 19, wherein the resettable fusing apparatus includes a plurality of positive temperature coefficient layers.

21. The circuit protection method of claim 19, including configuring the device for operation in a tip or ring line of a telecommunications circuit.

22. The circuit protection method of claim 19, including configuring the device for operation in a voltage supply line between a data bus controller and a data bus connector.

23. The circuit protection method of claim 19, including configuring the device for operation in a charging line of a battery pack.