MECHANISMS FOR DETECTING TAMPERING OF AN ELECTRONIC DEVICE

• US 20110031985A1
• Filed: 03/10/2010
• Published: 02/10/2011
• Est. Priority Date: 08/10/2009
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Johnson, Timothy M.
• Granted Patent: US 8,278,948 B2
• Time in Patent Office: Days
• US Class Current: 324/681
• CPC Class Codes: G01R 1/10 Arrangements of bearings
• CPC Class Codes: G06F 21/86 Secure or tamper-resistant housings
• CPC Class Codes: G08B 13/128 the housing being an electronic circuit unit, e.g. memory or CPU chip protecting computer components in secure or tamper resistant housings G06F21/86; protecting computer input devices, e.g. keyboards G06F21/83
• CPC Class Codes: G08B 13/1418 Removal detected by failure in electrical connection between the appliance and a control centre, home control panel or a power supply
• CPC Class Codes: G08B 13/1445 with detection of interference with a cable tethering an article, e.g. alarm activated by detecting detachment of article, breaking or stretching of cable furniture, e.g. shelves for displaying merchandise, incorporating tethers to prevent theft A47F7/024, A47F5/0861
• CPC Class Codes: H05K 1/0215 Grounding of printed circuits by connection to external grounding means
• CPC Class Codes: H05K 1/0268 for electrical inspection or testing
• CPC Class Codes: H05K 1/0275 Security details, e.g. tampering prevention or detection
• CPC Class Codes: H05K 1/0293 Individual printed conductors which are adapted for modification, e.g. fusable or breakable conductors, printed switches
• CPC Class Codes: H05K 2201/10151 Sensor
• CPC Class Codes: H05K 2201/10409 Screws
• CPC Class Codes: H05K 5/0208 Interlock mechanisms; Means for avoiding unauthorised use or function, e.g. tamperproof
• CPC Class Codes: H05K 7/1417 having securing means for mounting boards, plates or wiring boards H05K7/1461 takes precedence

Abstract

An electronic device has a chassis, and a printed wiring board (PWB) having a hole. A fastener is installed in the hole thereby securing the PWB to the chassis. A pair of conductive traces is formed in the PWB. A cap, being an amount of conductive glue, covers a part of the fastener and fills an electrically insulating gap between the two traces, to thereby form a conductive path that connects the two traces. A sensing circuit is coupled to the traces, to detect a change in impedance of the path and signal a tamper event alert. Other embodiments are also described and claimed.

Claims

1. An electronic device comprising:

a chassis;

a printed wiring board (PWB) having a hole, a fastener installed in the hole thereby securing the PWB to the chassis, the PWB having formed therein a pair of conductive traces, and a cap being an amount of conductive glue covering a part of the fastener and filling an electrically insulating gap between the two traces to thereby form a conductive path that connects the two traces; and

a sensing circuit coupled to the pair of traces to detect a change in impedance of the path.

2. The electronic device of claim 1 wherein as installed, a tool end of the fastener is below a surface of the PWB that is outside the hole, and the amount of conductive glue fills a part the hole.

3. The electronic device of claim 2 wherein the amount of conductive glue is in contact with said end of the fastener.

4. The electronic device of claim 2 wherein the pair of conductive traces are formed in the same plane of the PWB and above said end of the fastener.

5. The electronic device of claim 1 wherein as installed, a tool end of the fastener is above a surface of the PWB in which the pair of conductive traces are formed, and the amount of conductive glue is in contact with said end of the fastener.

9. The electronic device of claim 1 further comprising:

the PWB having another hole, a further fastener installed in said another hole thereby securing the PWB to the chassis, the PWB having formed therein a further pair of conductive traces, and a further cap being a measured amount of conductive glue covering a part of the further fastener and filling an electrically insulating gap between the further pair of traces to thereby form a further conductive path that connects the further pair of traces,

the sensing circuit being coupled to the further pair of traces to detect changes in impedance of the further path, and wherein said path and said further path are connected to each other in series.

6. An electronic device comprising:

a chassis having a conductive portion;

a printed wiring board (PWB) having a hole, a conductive fastener having a tool end, the fastener being installed in the hole thereby securing the PWB to the chassis'"'"' conductive portion, the PWB having formed therein a circuit trace, and a cap being a measured amount of conductive glue in contact with and covering the tool end of the fastener and filling an electrically insulating gap between the circuit trace and the tool end to thereby form a conductive path that connects the circuit trace to the chassis'"'"' conductive portion via the fastener; and

a sensing circuit coupled to the circuit trace and the chassis'"'"' conductive portion to detect a change in impedance of the conductive path.

7. The electronic device of claim 6 wherein the chassis'"'"' conductive portion is grounded.

8. The electronic device of claim 6 wherein the chassis'"'"' conductive portion is a grounded metal plate or bracket.

10. An electronic device comprising:

a chassis;

a printed wiring board (PWB) having a plurality of holes, and a plurality of fasteners installed in the holes, respectively, thereby securing the PWB to the chassis,

wherein for each hole the PWB has formed therein a respective pair of conductive traces and a respective cap, being a measured amount of conductive glue, covering a part of the fastener that is in the hole and filling an electrically insulating gap between the respective pair of traces to thereby form a respective conductive path with the pair of traces, said respective conductive paths being coupled to each other in series; and

a sensing circuit coupled to said series-coupled respective conductive paths to detect a change in impedance therein and in response signal an alert to a data processor that evaluates and logs tamper events in The electronic device.

11. The electronic device of claim 10 wherein the sensing circuit is coupled to the series-coupled respective conductive paths at only two nodes.

12. The electronic device of claim 10 wherein as installed, a tool end of the fastener is below a surface of the PWB within the hole, and the measured amount of conductive glue fills a part the hole.

13. The electronic device of claim 12 wherein the measured amount of conductive glue is in contact with said end of the fastener.

14. The electronic device of claim 10 wherein the pair of conductive traces are formed in the same plane of the PWB and above said end of the fastener.

15. The electronic device of claim 10 wherein as installed, a tool end of the fastener is above a surface of the PWB in which the pair of conductive traces are formed, and the measured amount of conductive glue is in contact with said end of the fastener.

16. An electronic device comprising:

a chassis;

a printed wiring board (PWB) having a plurality of holes, and a plurality of fasteners installed in the holes, respectively, thereby securing the PWB to the chassis,

wherein for each hole the PWB has formed therein a respective pair of conductive traces and a respective cap, being a measured amount of conductive glue, covering a part of the fastener that is in the hole and filling an electrically insulating gap between the respective pair of traces to thereby form a respective conductive path with the pair of traces, said respective conductive paths being connected as a randomly accessible sensor array; and

a selection and sensing circuit coupled to said randomly accessible sensor array, to pass a current through any one of the respective conductive paths at a time and then detect a change in impedance therein, the selection and sensing circuit to, in response to detecting the change in impedance, signal an alert to a data processor that evaluates and logs tamper events in The electronic device, wherein the alert identifies said one of the respective conductive paths in which the impedance change was detected.

17. The electronic device of claim 16 wherein as installed, a tool end of the fastener is below a surface of the PWB within the hole, and the measured amount of conductive glue fills a part the hole.

18. The electronic device of claim 17 wherein the measured amount of conductive glue is in contact with said end of the fastener.

19. The electronic device of claim 16 wherein the pair of conductive traces are formed in the same plane of the PWB and above said end of the fastener.

20. The electronic device of claim 16 wherein as installed, a tool end of the fastener is above a surface of the PWB in which the pair of conductive traces are formed, and the measured amount of conductive glue is in contact with said end of the fastener.

21. A method for manufacturing an electronic device comprising:

securing an assembled printed wiring board (PWB) to a chassis of the electronic device by installing a fastener through a hole in the PWB, wherein the PWB includes at least one circuit trace formed in a metal layer of the PWB adjacent to the hole; and

depositing an amount of conductive glue onto the installed fastener that is sufficient to cover a tool end of the fastener and fill an electrically insulating gap between the at least one circuit trace and the tool end to thereby form a tamper sensor.

22. The method of claim 21 further comprising:

testing the tamper sensor by evaluating output of the sensing circuitry in the assembled PWB, wherein the sensing circuitry is coupled to the circuit trace through a signal line formed in a metal layer of the PWB; and

recording an untampered state of the tamper sensor based on the evaluation.

23. The method of claim 22 further comprising setting a window or threshold in the sensing circuitry that defines a tamper event for the tamper sensor, wherein the sensing circuitry used to apply a voltage or current to the tamper sensor and compare an output of the tamper sensor to the set window or threshold to determine whether to signal a tamper event alert.