Reflowable circuit protection device

• US 9,620,318 B2
• Filed: 08/06/2012
• Issued: 04/11/2017
• Est. Priority Date: 08/12/2011
• Status: Active Grant

• Current Assignee: Littelfuse Incorporated
• Original Assignee: Littlefuse Incorporated
• Inventors: Matthiesen, Martyn A., Chen, Jianhua, Galla, Matthew P., Vranicar, Anthony, Montoya, Wayne, Pasma, Christopher
• Primary Examiner(s): Vortman, Anatoly
• Application Number:
  US13/567,784
• Publication Number:
  US 20130200984A1
• Time in Patent Office: 1,709 Days
• Field of Search: 337401, 337402, 337407-408, 337297, 337152, 337153, 337186
• CPC Class Codes: H01H 2037/768 characterised by the composition of the fusible material
• CPC Class Codes: H01H 37/761 with a fusible element forming part of the switched circuit H01H37/767 takes precedence

Abstract

A circuit protection device includes a substrate with first and second electrodes connected to the circuit to be protected. The circuit protection device also includes a heater element. A sensing element facilitates an electrical connection between the first and second electrodes. A flux material is provided around the sensing element. In a preferred embodiment, the flux contains a first component that is a polar material and a second component that is a non-polar material. A spring element exerts a force on the sensing element. The sensing element resists the force applied by the spring element. Upon detection of an activation, or fault, condition, the sensing element loses resilience and no longer resists the force exerted by the spring element, resulting in the spring element severing the electrical connection between the first and second electrodes. The flux allows the spring element to sever the electrical connection without dragging the sensing element.

Claims

1. A circuit protection device comprising:

a substrate comprising a first electrode and a second electrode;

a sliding contact disposed on the substrate;

a sensing element electrically coupled to the first electrode, the second electrode and the sliding contact;

a flux disposed around the sensing element in the form of a film; and

a spring element, wherein the spring element is disposed in an opening of the substrate and held in tension by the sliding contact;

wherein the sensing element resists a force exerted on the sliding contact by the spring element on the sensing element until, upon detection of an activation condition, the sensing element loses resilience and the force exerted on the sliding contact by the spring element causes the spring element to sever the electrical connection.

2. The circuit protection device of claim 1, wherein the flux comprises carboxylic acid.

3. The circuit protection device of claim 1, wherein the flux has a melting point that is less than a melting point of the sensing element.

4. The circuit protection device of claim 1, wherein the flux has a viscosity of less than approximately 150 centipoise.

5. The circuit protection device of claim 1, wherein the flux has an acid number of at least approximately 30.

6. The circuit protection device of claim 1, wherein the flux comprises a mixture of carboxylic acid and a polyethylene wax.

7. The circuit protection device of claim 6, wherein the mixture has a melting point less than a melting point of the sensing element.

8. A circuit protection device, comprising:

a substrate comprising a first electrode and a second electrode;

a sliding contact disposed on the substrate;

a sensing element electrically coupled to the first electrode, the second electrode and the sliding contact;

a flux disposed around the sensing element in the form of a film, said flux comprising a first component that is a polar material and a second component that is a non-polar material; and

a spring element, wherein the spring element is disposed in an opening of the substrate and held in tension by the sliding contact;

wherein the sensing element resists a force exerted on the sliding contact by the spring element on the sensing element until, upon detection of an activation condition, the sensing element loses resilience and the force exerted on the sliding contact by the spring element causes the spring element to sever the electrical connection.

9. The circuit protection device of claim 8, wherein the first component of the flux comprises carboxylic acid.

10. The circuit protection device of claim 8, wherein the second component of the flux comprises a wax.

11. The circuit protection device of claim 10, wherein the wax comprises a polyethylene wax.

12. The circuit protection device of claim 8, wherein the flux comprises a mixture of carboxylic acid and a polyethylene wax.

13. The circuit protection device of claim 12, wherein the mixture has a melting point that is less than a melting point of the sensing element.

14. The circuit protection device of claim 8, wherein the flux has a viscosity of less than approximately 150 centipoise.

15. The circuit protection device of claim 8, wherein the flux has an acid number of at least approximately 30.