Voltage switchable dielectric material containing conductor-on-conductor core shelled particles

• US 9,208,931 B2
• Filed: 12/15/2009
• 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:
  US12/638,360
• Publication Number:
  US 20100090176A1
• Time in Patent Office: 2,184 Days
• Field of Search: 361/117, 361/126, 338/21, 977/773, 977/774, 252/518.1, 252/519.3, 252/519.33
• 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: H01B 1/24 the conductive material comprising carbon-silicon compounds, carbon or silicon
• CPC Class Codes: H01C 7/108 Metal oxide
• CPC Class Codes: H01L 2224/05099 Material
• CPC Class Codes: H01L 2224/05599 Material
• CPC Class Codes: H01L 2224/13099 Material
• CPC Class Codes: H01L 2224/13599 Material
• CPC Class Codes: H01L 2224/29099 Material
• CPC Class Codes: H01L 2224/29599 Material
• CPC Class Codes: H01L 2924/00013 Fully indexed content
• CPC Class Codes: H01L 2924/01013 Aluminum [Al]
• CPC Class Codes: H01L 2924/01029 Copper [Cu]
• CPC Class Codes: H01L 2924/01046 Palladium [Pd]
• CPC Class Codes: H01L 2924/01058 Cerium [Ce]
• CPC Class Codes: H01L 2924/01078 Platinum [Pt]
• CPC Class Codes: H01L 2924/01079 Gold [Au]
• CPC Class Codes: H05K 1/0257 Overvoltage protection
• CPC Class Codes: H05K 1/0259 Electrostatic discharge [ESD] protection
• CPC Class Codes: H05K 1/0373 containing additives, e.g. fillers H05K1/036 takes precedence
• CPC Class Codes: H05K 2201/0218 : Composite particles, i.e. first metal coated with second metal
• CPC Class Codes: H05K 2201/0738 : Use of voltage responsive materials, e.g. voltage switchable dielectric or varistor materials

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 conductor shell, so as to form a conductor-on-conductor core shell particle constituent for the VSD material.

Claims

1. A substrate comprising:

a first conductive layer;

a second conductive layer;

a voltage switchable dielectric (VSD) material between the first conductive layer and the second conductive layer, the VSD comprising;

a polymer binder; and

a quantity of particles dispersed in the binder, the quantity of particles including nano-dimensioned particles and a set of core shell particles, each core shell particle of the set including (i) a core formed from conductive material, and (ii) at least one shell layer, the at least one shell layer comprising shell material formed from at least two metal oxides, the nano-dimensioned particles comprising at least one of metal oxide, nanorods, or nanowires,

wherein the VSD material is dielectric in the absence of an applied voltage that exceeds a characteristic level and conductive in the presence of the applied voltage that exceeds the characteristic level.

2. The substrate of claim 1, wherein the at least one shell layer comprises multiple shell layers, the multiple shell layers including an exterior layer formed from conductive material that is different than the conductive material of the core, the conductive material of at least one of the multiple shell layers includes copper.

3. The substrate of claim 1, wherein the quantity of particles are dispersed in the polymer binder in a concentration that is at or above a percolation level of the VSD material.

4. The substrate of claim 1, wherein the at least one shell layer includes a nickel oxide layer.

5. The substrate of claim 1, wherein at least one of the core or the at least one shell layer is surface modified to include a polymer.

6. The substrate of claim 1, wherein at least one of the core or the at least one shell layer is surface modified to include a cross-linked polymer.

7. The substrate of claim 1, wherein the quantity of particles further comprises non-core shell particles that include at least one of:

conductive particles, semiconductor particles and the nano-dimensioned particles.

8. The substrate of claim 7, wherein the quantity of particles further comprises active varistor particles.

9. The substrate of claim 1, wherein the nano-dimensioned particles do not include nanowires or nanorods.

10. The substrate of claim 1, wherein the nano-dimensioned particles do not include metal oxide.

11. The substrate of claim 1, wherein the quantity of particles further comprises non-core shell particles that include Boron.

12. The substrate of claim 1, wherein the polymer binder comprises a conductive polymer.

13. The substrate of claim 1, wherein the at least one shell layer includes the at least one layer of conductive material as an exterior-most layer.

14. The substrate of claim 1, wherein the at least one shell layer includes at least one layer of material that is comprised of nickel.

15. The substrate of claim 1, wherein the conductor core is formed from material that includes copper.

16. The substrate of claim 1, wherein the at least one shell layer include a first layer of a first material, and a second layer of a second material that is different than the first material.

17. The substrate of claim 16, wherein each of the first material and the second material is a metal.

18. The substrate of claim 1, wherein current flows from the first conductive layer to the second conductive layer when the applied voltage exceeds the characteristic level.

19. A composition of a substrate comprising:

a first conductive layer;

a second conductive layer;

a voltage switchable dielectric (VSD) material between the first conductive layer and the second conductive layer, the composition of the VSD material comprising;

a polymer binder; and

a quantity of particles dispersed in the binder, the quantity of particles including nano-dimensioned particles and a set of core shell particles, each core shell particle comprising (i) a conductive or semi-conductive core, and (ii) at least one shell layer, the at least one shell layer comprising shell material formed from at least two metal oxides, the at least one shell layer including an exterior layer formed from a metal oxide, the nano-dimensioned particles comprising at least one of metal oxide, nanorods, or nanowires,

wherein the composition of VSD material is dielectric in the absence of an applied voltage that exceeds a characteristic level and conductive in the presence of the applied voltage that exceeds the characteristic level.

20. The substrate of claim 19, wherein the at least one shell layer of the VSD material include nickel.

21. The substrate of claim 19, wherein the at least one shell layer of the VSD material include a nickel layer and a nickel oxide layer.

22. The substrate of claim 19, wherein the core of the VSD material is conductive and formed from copper.

23. The substrate of claim 19, wherein at least one of the core or one of the at least one shell layer of the VSD material is surface modified to include a polymer.

24. The substrate of claim 19, wherein the core of the VSD material is semiconductive and formed form a metal oxide of a first type, and where the at least one shell layer of the shell are formed from a metal oxide of a second type.

25. The substrate of claim 24, wherein the core of the VSD material is formed from Titanium dioxide (TiO₂).

26. The substrate of claim 24, wherein the at least one shell layer of the VSD material include Antimony tin oxide (ATO).

27. The substrate of claim 24, wherein the core of the VSD material is formed from Titanum dioxide (TiO₂).

28. The substrate of claim 19, wherein current flows from the first conductive layer to the second conductive layer when the applied voltage exceeds the characteristic level.