Substrate device or package using embedded layer of voltage switchable dielectric material in a vertical switching configuration

• US 8,203,421 B2
• Filed: 04/02/2009
• Issued: 06/19/2012
• Est. Priority Date: 04/14/2008
• Status: Active Grant

• Current Assignee: Littelfuse Incorporated
• Original Assignee: Shocking Technologies, Inc.
• Inventors: Kosowsky, Lex, Fleming, Robert, Graydon, Bhret
• Primary Examiner(s): HARVEY, JAMES R
• Application Number:
  US12/417,589
• Publication Number:
  US 20090256669A1
• Time in Patent Office: 1,174 Days
• Field of Search: 338/20, 338/21
• 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

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 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.

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

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

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

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

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

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

9. The method of claim 1, wherein forming the opening into the electrically isolative layer includes precision depth drilling the opening using a YAG laser.

10. The method of claim 1, wherein forming the opening into the electrically isolative layer includes drilling the opening.

11. The method of claim 1, wherein forming the opening into the electrically isolative layer includes laser drilling the opening.

12. The method of claim 1, 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 precision depth drilling the opening includes using a feedback component to detect transition in drilling from the electrically isolative layer to the VSD material.