SUBSTRATE DEVICE OR PACKAGE USING EMBEDDED LAYER OF VOLTAGE SWITCHABLE DIELECTRIC MATERIAL IN A VERTICAL SWITCHING CONFIGURATION

• US 20090256669A1
• Filed: 04/02/2009
• Published: 10/15/2009
• Est. Priority Date: 04/14/2008
• Status: Active Grant

• Current Assignee: Littelfuse Incorporated
• Original Assignee: Shocking Technologies, Inc.
• Inventors: Graydon, Bhret, Kosowsky, Lex, Fleming, Robert
• Granted Patent: US 8,203,421 B2
• Time in Patent Office: Days
• US Class Current: 338/21
• 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 2201/0738 Use of voltage responsive materials, e.g. voltage switchable dielectric or varistor materials
• CPC Class Codes: H05K 2203/105 Using an electrical field; Special methods of applying an electric potential electroplating H05K2203/0723

Abstract

A substrate device includes an embedded layer of VSD material that overlays a conductive element or layer to provide a ground. An electrode, connected to circuit elements that are to be protected, extends into the thickness of the substrate to make contact with the VSD layer. When the circuit elements are operated under normal voltages, the VSD layer is dielectric and not connected to ground. When a transient electrical event occurs on the circuit elements, the VSD layer switches instantly to a conductive state, so that the first electrode is connected to ground.

Claims

1. A device comprising:

a first electrode;

a second electrode vertically spaced from the first electrode;

a layer of voltage switchable dielectric (VSD) material that is positioned between the first electrode and the second electrode, the layer of VSD material being in contact with the second electrode;

a layer of electrically isolative material provided between the layer of VSD material and the first electrode; and

wherein the first electrode extends vertically into the layer of electrically isolative material so as to make contact with the layer of VSD material.

2. The device of claim 1, wherein the first electrode makes surface contact with the layer of VSD material.

3. The device of claim 1, wherein the first electrode makes intermediate contact with the layer of VSD material.

4. The device of claim 1, wherein the first electrode is shaped to match an opening that is formed in the layer of electrically isolative material.

5. The device of claim 1, wherein the electrically isolative material is epoxy impregnated glass cloth.

6. The device of claim 1, wherein the electrically isolative material is a B-stage resin.

7. The device of claim 1, wherein the electrically isolative material has a high dielectric constant.

8. The device of claim 1, wherein the electrically isolative material is a polyimide.

9. A method for forming a substrate device, the method comprising:

forming a substrate stack comprising (i) an electrically isolative layer, (ii) voltage switchable dielectric (VSD) material that underlies the electrically isolative material, and (iii) a grounding electrode, the VSD material overlaying the grounding electrode;

forming an opening into the electrically isolative layer without extending the opening through the layer of VSD material; and

forming conductive material on at least a portion of the opening in order to form a first electrode that is in contact with VSD material.

10. The method of claim 9, wherein forming the opening into the electrically isolative layer includes drilling the opening.

11. The method of claim 9, wherein forming the opening into the electrically isolative layer includes laser drilling the opening.

12. The method of claim 9, wherein forming the opening into the electrically isolative layer includes precision depth drilling the opening so as to form the opening without substantially affecting a thickness of the VSD material.

13. The method of claim 9, wherein forming the opening into the electrically isolative layer includes precision depth drilling the opening using a YAG laser.

14. The method of claim 13, wherein precision depth drilling the opening includes using a feedback component to detect transition in drilling from the electrically isolative layer to the VSD material.

15. A substrate device comprising:

a grounding electrode;

a layer of voltage switchable dielectric (VSD) material overlaying the grounding electrode, wherein the VSD material is triggerable to switch from a non-conductive state into a conductive state with application of energy that exceeds a designated threshold level;

a layer of electrically isolative material formed over the layer of VSD material; and

a first electrode that extends in a vertical dimension through the layer of electrically isolative material to at least contact, but not extend through, the layer of VSD material, so as to provide a grounding path from the first electrode to the second electrode in presence of a transient electrical event that supplies energy in excess of the designated threshold to at least a portion of the layer of VSD material.

16. The substrate device of claim 15, wherein the first electrode extends to make contact with the layer of VSD material without affecting a thickness of the layer of VSD material by more than 20%.

17. The substrate device of claim 15, wherein the first electrode extends to make contact with the layer of VSD material without affecting a thickness of the layer of VSD material by more than 100 nanometers.

18. The substrate device of claim 15, wherein the electrically isolative material is prepregnated material.

19. The substrate device of claim 15, wherein the layer of VSD material includes either organic or inorganic high aspect ratio particles.

20. The substrate device of claim 15, wherein the layer of VSD material includes carbon nanotubes.

21. A multi-layered substrate device comprising:

a plurality of core layers, including an interior core layer and an exterior core layer;

one or more grounding planes embedded within a thickness of the substrate device, between at least two core layers;

one or more layers of VSD material overlaying and in contact with the grounding plane;

one or more layers of electrically isolative material separating each of the one or more layers of VSD material from at least one of the core layers;

wherein the exterior core layer includes a grounding electrode and overlays one of the layers of electrically isolative material;

wherein the one or more layers of VSD material include an exterior layer of VSD material underlying the layer of electrically isolative material that underlies one of the exterior core layers;

wherein grounding electrode extends through the underlying layer of electrically isolative material to reach the underlying layer of VSD material, in order to enable at least a portion of conductive elements of the exterior core layer to be grounded when an electrical transient event occurs that exceeds a characteristic voltage of the layer of VSD material.

22. The multi-layered substrate device of claim 21, wherein the electrically isolative material is epoxy impregnated glass cloth.