Real time strain sensing solution

• US 9,086,267 B2
• Filed: 08/29/2013
• Issued: 07/21/2015
• Est. Priority Date: 08/29/2013
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Ahmad, Mudasir, Xie, Weidong, Wang, Qiang
• Primary Examiner(s): Caputo, Lisa
• Assistant Examiner(s): DUNLAP, JONATHAN M
• Application Number:
  US14/013,103
• Publication Number:
  US 20150059487A1
• Time in Patent Office: 691 Days
• Field of Search: 737/69, 73774-778, 737/88, 737/80, 738/624.74, 738/51
• US Class Current: 1/1
• CPC Class Codes: G01B 7/22 using change in capacitance
• CPC Class Codes: G01L 1/06 by measuring the permanent deformation of gauges, e.g. of compressed bodies
• CPC Class Codes: G01L 1/142 using capacitors
• CPC Class Codes: H05K 1/0268 for electrical inspection or testing
• CPC Class Codes: H05K 2201/10151 Sensor
• CPC Class Codes: H05K 3/3442 having edge contacts, e.g. leadless chip capacitors, chip carriers

Abstract

Strain sensing may be provided. First, a strain threshold for a circuit board may be determined. Then a strain capacitor may be selected that will fail when the circuit board is subjected to the strain threshold while the strain capacitor is mounted on the circuit board. The strain capacitor may be ceramic and may be in a commercially available size. The strain capacitor may then be mounted to the circuit board and monitored for failure.

Claims

1. A method comprising:

determining a strain threshold for a circuit board, the strain threshold corresponds to an amount of flexing the circuit board will tolerate without failing at least one of the following;

the circuit board;

a solder joint on the circuit board; and

a trace on the circuit board;

selecting a strain capacitor that will fail when the circuit board is subjected to the strain threshold while the strain capacitor is mounted on the circuit board;

mounting the strain capacitor to the circuit board; and

monitoring the strain capacitor for failure.

2. The method of claim 1, wherein determining the strain threshold for the circuit board comprises determining the strain threshold between 3,000μ

ε and

5,000μ

ε

inclusively.

3. The method of claim 1, wherein selecting the strain capacitor comprises selecting the strain capacitor comprising a ceramic capacitor.

4. The method of claim 1, wherein selecting the strain capacitor comprises selecting the strain capacitor comprising a ceramic strain capacitor in a commercially available size.

5. The method of claim 1, wherein selecting the strain capacitor comprises selecting the strain capacitor comprising a ceramic strain capacitor in a commercially available size between 1812 and 2225 inclusively.

6. The method of claim 1, wherein selecting the strain capacitor that will fail when the circuit board is subjected to the strain threshold while the strain capacitor is mounted on the circuit board comprises selecting the strain capacitor that will crack when the circuit board is subjected to the strain threshold while the strain capacitor is mounted on the circuit board.

7. The method of claim 1, wherein mounting the strain capacitor to the circuit board comprises mounting the strain capacitor in a high strain region on the circuit board.

8. The method of claim 1, wherein monitoring the strain capacitor for failure comprises determining that the strain capacitor has failed.

9. The method of claim 8, wherein monitoring the strain capacitor for failure comprises recording a time when the strain capacitor failed.

10. An apparatus comprising:

a circuit board having a predetermined strain threshold wherein the predetermined strain threshold corresponds to an amount of flexing the circuit board will tolerate without failing at least one of the following;

the circuit board;

a solder joint on the circuit board; and

a trace on the circuit board;

a strain capacitor mounted to the circuit board, the strain capacitor comprising a commercially available ceramic strain capacitor and comprising a commercially available size that will fail by cracking when the circuit board is subjected to the predetermined strain threshold; and

a monitor configured to detect when the strain capacitor fails.

11. The apparatus of claim 10, wherein the monitor is configured to record when the strain capacitor failed.

12. The apparatus of claim 10, wherein the monitor comprises:

a memory; and

a timer configured to record, in the memory, the time the strain capacitor failed.

13. The apparatus of claim 10, wherein the strain capacitor comprises a size between 1812 and 2225 inclusively.

14. The apparatus of claim 10, wherein the predetermined strain threshold is between 3,000μ

ε and

5,000μ

ε

inclusively.

15. A method comprising:

monitoring a strain capacitor on a circuit board, the strain capacitor comprising a prefabricated ceramic strain capacitor and comprising a size that will fail when the circuit board is subjected to a predetermined strain threshold wherein the predetermined strain threshold corresponds to an amount of flexing the circuit board will tolerate without failing at least one of the following;

the circuit board;

a solder joint on the circuit board; and

a trace on the circuit board;

determining that the strain capacitor has failed; and

recording a time when the strain capacitor failed.

16. The method of claim 15, wherein monitoring the strain capacitor on the circuit board comprises mounting the strain capacitor in a high strain region on the circuit board.

17. The method of claim 15, wherein monitoring the strain capacitor on the circuit board comprises monitoring the strain capacitor wherein the predetermined strain threshold comprises between 3,000 μ

ε and

5,000 μ

ε

inclusively.

18. The method of claim 15, wherein determining that the strain capacitor has failed comprises determining that the strain capacitor has failed by a strain monitor located on the circuit board.

19. The method of claim 15, wherein recording the time when the strain capacitor failed comprises recording the time in a memory located on the circuit board.