Self-limiting electrical triggering for initiating fracture of frangible glass

• US 10,026,579 B2
• Filed: 07/26/2016
• Issued: 07/17/2018
• Est. Priority Date: 07/26/2016
• Status: Active Grant

• Current Assignee: SRI International, Inc.
• Original Assignee: Palo Alto Research Center, Inc. (Xerox Holdings Corp.)
• Inventors: Whiting, Gregory, Limb, Scott J., Chua, Christopher L., Garner, Sean, Smullin, Sylvia J., Wang, Qian, Lujan, Rene A.
• Primary Examiner(s): CHOI, CALVIN Y
• Application Number:
  US15/220,164
• Publication Number:
  US 20180033577A1
• Time in Patent Office: 721 Days
• Field of Search: None
• CPC Class Codes: H01H 85/0052 Fusible element and series heating means or series heat dams
• CPC Class Codes: H01L 21/78 with subsequent division of the substrate into plural individual devices cutting to change the surface-physical characteristics or shape of semiconductor bodies H01L21/304
• CPC Class Codes: H01L 23/57 Protection from inspection, reverse engineering or tampering
• CPC Class Codes: H03K 19/17768 for security

Abstract

A transient electronic device includes electronic elements (e.g., an SOI- or chip-based IC) and a trigger mechanism disposed on a frangible glass substrate. The trigger mechanism includes a switch that initiates a large trigger current through a self-limiting resistive element in response to a received trigger signal. The self-limiting resistive element includes a resistor portion that generates heat in response to the trigger current, thereby rapidly increasing the temperature of a localized (small) region of the frangible glass substrate, and a current limiting portion (e.g., a fuse) that self-limits (terminates) the trigger current after a predetermined amount of time, causing the localized region to rapidly cool down. The frangible glass substrate is engineered such that a stress profile produced by the rapid heating/cooling of the localized region generates an initial fracture force that subsequently propagates throughout the glass substrate, whereby sufficient potential energy is released to powderize the electronic elements.

Claims

1. A transient electronic device including:

a frangible glass substrate;

one or more electronic elements disposed on the frangible glass substrate such that fracturing of the frangible glass substrate causes fracturing of the electronic elements; and

a trigger mechanism comprising;

a self-limiting resistive element comprising a resistive material disposed over a localized region of said frangible glass substrate, the self-limiting resistive element comprising first and second resistor structures; and

a switch element coupled to the self-limiting resistive element, wherein said self-limiting resistive element is configured such that;

during a first time period after said switch element is actuated to initiate a trigger current from a power source through said self-limiting resistive element, heat generated by said self-limiting resistive element increases a localized temperature of said localized region from an initial temperature toward a first temperature level, and

a current limiting portion of said self-limiting resistive element, comprising a fuse element connected between the first and second resistor structures, independently controls the flow of said trigger current such that said trigger current flow is terminated when said localized temperature of said localized region reaches said first temperature level, thereby causing said localized temperature to decrease from said first temperature level to a second temperature level,

wherein said frangible glass substrate is configured such that a stress profile generated in said localized region by a thermal pulse comprising said thermal increase and said thermal decrease is sufficient to produce an initial fracture force in said localized region.

2. The transient electronic device according to claim 1, wherein said resistive material of said self-limiting resistive element comprises one or more of magnesium, copper, tungsten, aluminum, molybdenum and chrome that is disposed directly onto a surface of said frangible glass substrate.

3. The transient electronic device according to claim 1,

wherein said self-limiting resistive element is connected in series with said current-limiting portion between first and second terminals,

wherein said first terminal is coupled by way of said switch element to a direct current (DC) power source, and

wherein said second terminal is connected to ground.

4. The transient electronic device according to claim 3,

wherein said fuse element is configured to break after said first time period, thereby terminating flow of said trigger current through said first and second resistor structures.

5. The transient electronic device according to claim 4, wherein said self-limiting resistive element comprises a patterned metal layer structure disposed directly on a surface of said frangible glass substrate with said first and second resistor structures respectively including first and second downward-tapered sections, and said fuse element comprising a narrow structure connected between the first and second downward-tapered sections.

6. The transient electronic device according to claim 5, wherein said narrow portion comprises a straight rectangular structure extending between tapered ends of said first and second downward-tapered sections and having a width that is greater than a thickness of said frangible glass substrate.

7. The transient electronic device according to claim 6, wherein said thickness of said frangible glass substrate is approximately 0.25 mm, and said width of said narrow portion is approximately 0.3 mm or greater.

8. The transient electronic device according to claim 1, wherein said trigger mechanism further comprises a sensor configured to detect a predetermined transmitted wave signal, and configured to generate said trigger signal upon detection of said predetermined transmitted wave signal.

9. The transient electronic device according to claim 8, wherein said sensor comprises one of a light wave sensor, a radio-frequency wave sensor, and an acoustic wave sensor.

10. The transient electronic device according to claim 8, wherein said switch element comprises one of a silicon controlled rectifier, a single transistor and a multiple-element circuit.

11. The transient electronic device according to claim 8, wherein at least one of said switch element and said sensor is disposed directly on said frangible glass substrate.

12. The transient electronic device according to claim 8, wherein said one or more electronic elements are disposed on a semiconductor structure that is fixedly attached to said frangible glass substrate, and wherein at least one of said switch element and said sensor is disposed on said semiconductor structure.

13. The transient electronic device according to claim 1, wherein said frangible glass substrate comprises one of a stressed glass substrate, a thermally tempered glass substrate, and an ion-exchange treated glass substrate.

14. The transient electronic device according to claim 9, wherein said one or more electronic elements comprise an integrated circuit fabricated on one of a silicon-on-insulator layer and a silicon die integrated circuit chip fixedly disposed on said frangible glass substrate.

15. A triggering method for initiating fracturing of electronic elements disposed on a frangible glass substrate comprising glass having a melting point temperature, said method comprising:

generating a thermal increase in a localized region of said frangible glass substrate by actuating a switch element coupled between a power source and a self-limiting resistive element comprising a fuse element connected between first and second resistor structures, such that a direct current flows from the power source through the switch element and the self-limiting resistive element, thereby causing the self-limiting resistive element to generate and transmit heat into said localized region at a sufficiently high rate to cause a localized temperature of said localized region to increase from an initial temperature to a first temperature, said first temperature being higher than said melting point temperature; and

generating a thermal decrease such that said localized temperature in said localized region decreases from said first temperature to a second temperature, said second temperature being lower than said first temperature, wherein a thermal pulse generated by said thermal increase and said thermal decrease generates an initial fracture force in the localized region,

wherein a duration of said thermal increase is independently controlled by said self-limiting resistive element.

16. The method of claim 15, further comprising detecting a wave signal, and wherein generating said thermal increase comprises controlling said switch element in response to said detected wave signal.

17. The method of claim 16, wherein detecting said wave signal comprises detecting one of a light wave signal, a radio-frequency wave signal, and an acoustic wave signal.

18. The method of claim 16, wherein detecting said wave signal comprises utilizing a photodiode to detect a light signal, and wherein controlling said switch element comprises controlling a silicon controlled rectifier using a current passing through said photodiode.

19. A transient electronic device including:

a frangible glass substrate;

one or more electronic elements disposed on the frangible glass substrate; and

a trigger mechanism comprising;

a self-limiting resistive element including a fuse element disposed between a first resistor structure and a second resistor structure disposed on said frangible glass substrate; and

a switch element coupled between the self-limiting resistive element and a power source such that actuation of said switch element initiates a trigger current from said power source through said self-limiting resistive element,

wherein said self-limiting resistive element is configured such that passing said trigger current from said power source through said self-limiting resistive element produces a thermal pulse in said frangible glass substrate, and

wherein said frangible glass substrate is configured such that a stress profile generated by said thermal pulse causes an initial fracture force in said localized region, and said frangible glass substrate is further configured such that said initial fracture force causes propagating fracture forces that result in fracture of said frangible glass substrate and said one or more electronic elements.

20. The transient electronic device according to claim 19, wherein said switch element comprises one of a silicon controlled rectifier, a single transistor and a multiple-element circuit.

21. The transient electronic device according to claim 19, wherein said trigger mechanism further comprises a sensor configured to detect a predetermined transmitted wave signal, and configured to actuate said switch element by generating a trigger signal upon detection of said predetermined transmitted wave signal.