Surface mountable device

• US 6,806,519 B2
• Filed: 10/07/2002
• Issued: 10/19/2004
• Est. Priority Date: 10/08/2001
• Status: Expired due to Fees

• Current Assignee: Polytronics Technology Corporation
• Original Assignee: Polytronics Technology Corporation
• Inventors: Wang, David Shau-Chew, Chu, Edward Fu-Hua, Ma, Yun-Ching
• Primary Examiner(s): LE, DUNG ANH
• Application Number:
  US10/265,540
• Publication Number:
  US 20030067054A1
• Time in Patent Office: 743 Days
• Field of Search: 257/266-234, 257/470, 438/48
• US Class Current: 257/234
• CPC Class Codes: H01C 1/1406 Terminals or electrodes formed on resistive elements having positive temperature coefficient
• CPC Class Codes: H01C 7/02 having positive temperature coefficient ceramics C04B
• CPC Class Codes: H01C 7/027 consisting of conducting or semi-conducting material dispersed in a non-conductive organic material

Abstract

The present invention discloses a surface mountable device comprising a current-sensitive element and two electrodes. The current-sensitive element is composed of a PTC conductive composite, comprising at least one polymer and a conductive filler. The feature of the present invention is that the current-sensitive element is a three-dimensional bent structure so that the shape, length and height of the device can be varied according to the space of the circuit board and the resistance of the surface mountable device. Therefore, the mountable surface of the circuit board can be used more efficiently. Moreover, the area of the current-sensitive element of the present invention is larger than that of the conventional surface mountable device. Consequently, the normal resistance of the surface mountable device of the present invention is smaller than that of the conventional surface mountable device and the voltage endurance of the surface mountable device of the present invention is increased.

Claims

1. A surface mountable device comprising:

a current-sensitive element having a sinuous shape for reducing normal resistance;

a first electrode connected to one surface of said current-sensitive element; and

a second electrode connected to another surface of said current-sensitive element.

2. The surface mountable device of claim 1, wherein said first electrode and said second electrode are made of conductive material.

3. The surface mountable device of claim 2, wherein said conductive material is selected from the group consisting essentially of copper, gold, nickel and alloy thereof.

4. The surface mountable device of claim 1, wherein said current-sensitive element is composed of a conductive composite material exhibiting a positive temperature coefficient behavior.

5. The surface mountable device of claim 4, wherein said conductive composite material comprises:

a crystalline polymer; and

a conductive filler dispersed in said crystalline polymer.

6. The surface mountable device of claim 5, wherein said crystalline polymer is selected from the group consisting essentially of polyethylene, polypropylene, polyoctylene, polyvinylidene fluoride, polytetrafluoroethylene, and the mixture thereof.

7. The surface mountable device of claim 5, wherein said conductive filler is selected from the group consisting essentially of carbon black, metal power, carbonized ceramic powder and the mixture thereof.

8. The surface mountable device of claim 5, wherein said conductive composite material further comprises a photo initiator, a cross-linking agent, a coupling agent, a dispersing agent, a stabilizer, a flame retardant, a plasticizing agent, an anti-oxidizing agent and a non-conductive filler to improve its sensitivity and physical property.

9. The surface mountable device of claim 1, wherein said current-sensitive element is S-shaped.

10. The surface mountable device of claim 1, wherein said current-sensitive element is bow-shaped.

11. The surface mountable device of claim 1, wherein vacant spaces enclosed by said current-sensitive element are filled by an insulating material to avoid a current leakage.

12. The surface mountable device of claim 1, wherein the first and second electrodes follow the sinuous shape of the current-sensitive element.