Voltage switchable dielectric material containing conductive core shelled particles

• US 9,208,930 B2
• Filed: 09/30/2009
• Issued: 12/08/2015
• Est. Priority Date: 09/30/2008
• Status: Active Grant

• Current Assignee: Littelfuse Incorporated
• Original Assignee: Littelfuse Incorporated
• Inventors: Kosowsky, Lex, Fleming, Robert, Wu, Junjun, Saraf, Pragnya, Ranganathan, Thangamani
• Primary Examiner(s): Nguyen, Khanh Tuan
• Assistant Examiner(s): NGUYEN, HAIDUNG D
• Application Number:
  US12/571,318
• Publication Number:
  US 20100090178A1
• Time in Patent Office: 2,260 Days
• Field of Search: 252/500, 252/518.1, 252/519.3, 252/519.33, 257/536
• US Class Current: 1/1
• CPC Class Codes: H01B 1/20 Conductive material dispersed in non-conductive organic material organic macromolecular compounds or compositions C08
• CPC Class Codes: H01B 1/22 the conductive material comprising metals or alloys
• CPC Class Codes: H01C 7/10 voltage responsive, i.e. varistors

Abstract

A composition of voltage switchable dielectric (VSD) material that comprises a concentration of core shelled particles that individually comprise a conductor core and a shell, the shell of each core shelled particle being (i) multilayered, and/or (ii) heterogeneous.

Claims

1. A voltage switchable dielectric (VSD) material comprising:

a binder; and

a set of core shelled particles dispersed in the binder, wherein each core shell particle in the set comprises;

(i) a conductor core; and

(ii) a shell comprising a plurality of layers, including a first layer of a first material and a second layer of a second material that is different than the first material.

2. The VSD material of claim 1, wherein the set of particles are dispersed in the binder in a concentration that is at or above a percolation level of the composition.

3. The VSD material of claim 1, further comprising non-core shelled particles that are conductors or semi-conductors.

4. The VSD material of claim 1, further comprising non-core shelled particles that are nano-dimensioned particles.

5. The VSD material of claim 4, wherein the nano-dimensioned particles are high-aspect ratio particles.

6. The VSD material of claim 4, wherein the nano-dimensioned particles are organic.

7. The VSD material of claim 4, wherein the nano-dimensioned particles include carbon nano-tubes.

8. The VSD material of claim 4, wherein the nano-dimensioned particles include high-aspect ratio metal particles.

9. The VSD material of claim 1, further comprising Boron particles other than the set of core shelled particles.

10. The VSD material of claim 1, further comprising active varistor particles other than the set of core shelled particles.

11. The VSD material of claim 1, wherein the binder is formed from a conductive polymer.

12. The VSD material of claim 1, wherein the shell of at least some of the core shell particles in the set includes a semi-conductive or resistive material.

13. The VSD material of claim 1, wherein the conductor core of at least some of the core shelled particles in the set includes a metal particle.

14. The VSD material of claim 13, wherein the shell of at least some of the core shelled particles in the set includes one or more kinds of oxides.

15. The VSD material of claim 14, wherein the shell of at least some of the core shell particles in the set includes one or more kinds of oxides formed on the metal particles.

16. The VSD material of claim 13, wherein the shell of at least some of the core shelled particles in the set includes one or more kinds of metal-oxides.

17. The VSD material of claim 1, wherein at least one of the first layer or the second layer of the shell of one or more of the core shelled particles in the set is comprised of a layer that is formed from two or more types of material.

18. The VSD material of claim 1, wherein at least one of the first layer or the second layer of the shell of one or more core shelled particles in the set is non-uniform, so as to expose the conductor core or an underlying shell.

19. The VSD material of claim 1, wherein at least some of the core shelled particles in the set comprise a nickel core and a metal oxide shell.

20. A VSD material comprising:

a polymer binder;

a set of core shelled particles that individually comprise a metal core and a shell, wherein the shell is multi-layered, and is comprised of multiple kinds of material, including a metal oxide.

21. The VSD material of claim 20, wherein the set of particles are dispersed in the binder in a concentration that is at or above a percolation level of the composition.

22. The VSD material of claim 20, further comprising non-core shelled particles that are conductors or semi-conductors.

23. The VSD material of claim 20, further comprising non-core shelled particles that are nano-dimensioned particles.

24. The VSD material of claim 23, wherein the nano-dimensioned particles are high-aspect ratio particles.

25. The VSD material of claim 23, wherein the nano-dimensioned particles are organic.

26. The VSD material of claim 23, wherein the nano-dimensioned particles include carbon nano-tubes.

27. The VSD material of claim 23, wherein the nano-dimensioned particles include high-aspect ratio metal particles.

28. The VSD material of claim 20, wherein at least one of the first layer or the second layer of the shell of at least some of the core shelled particles in the set is non-uniform, so as to expose the conductor core or an underlying shell.