US4593245A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Eddy current method for detecting a flaw in semi-conductive material
Assignee: General Electric Co
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Filing: 1983-12-12
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Granted: 1986-06-03
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Expires: 2003-12-12
Abstract
Abstract An eddy current probe, excitable at frequencies equal to or greater 7 mhz., includes a substantially planar, spiral-like, unilaminar coil mounted on an insulative substrate. A protective layer covers the coil and is adapted to present only a minimal mechanical barrier between the coil and a region of material under test. The coil is a continuous run of copper having an effective diameter no greater than 2 mils. The coil, substrate and protective layer are a printed circuit board. A method of detecting flaws is also disclosed.
Inventors
- 👤 John R. M. Viertl
- 👤 Mederic E. Auger
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 19:55
CPC Classifications
G; G01; G01N; G01N27/00; G01N27/72; G01N27/82; G01N27/90; G01N27/9006
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
204 words
A method for detecting a flaw in a surface and/or sub-surface region of a semi-conductive material, the semi-conductive material including a conducting material disposed in the sub-surface region at a predetermined distance from the surface of the semi-conductive material, comprising the steps of: providing a continuous run of metal configured spiral-like on a substantially planar insulative substrate as a unilaminar coil; exciting said coil to produce an electromagnetic field extending from said coil, the electromagnetic field for inducing eddy currents in the surface and/or sub-surface region of the semi-conductive material when said coil is positioned adjacent said semi-conductive material; establishing a reference signal corresponding to the impedance of said coil when said coil is adjacent an unflawed region of said material; juxtapositioning said coil adjacent the surface and/or sub-surface region of the semi-conductive material to induce an electromagnetic field therein, while inhibiting induction of eddy currents in the conducting material; and comparing a signal representative of the impedance of said coil during said juxtapositioning step with said reference signal to provide an output signal indicative of the integrity of said surface and/or sub-surface region of the semi-conductive material, whereby the flaw in the surface and/or sub-surface region of the semi-conductive material may be detected.
Claim 2
Independent Claim
204 words
A method for detecting a flaw in a surface and/or sub-surface region of a semi-conductive material, the semi-conductive material including a conducting material disposed in the sub-surface region at a predetermined distance from the surface of the semi-conductive material, comprising the steps of: providing a continuous run of metal configured spiral-like on a substantially planar insulative substrate as a unilaminar coil; exciting said coil to produce an electromagnetic field extending from said coil, the electromagnetic field for inducing eddy currents in the surface and/or sub-surface region of the semi-conductive material when said coil is positioned adjacent said semi-conductive material; establishing a reference signal corresponding to the impedance of said coil when said coil is adjacent an unflawed region of said material; juxtapositioning said coil adjacent the surface and/or sub-surface region of the semi-conductive material to induce an electromagnetic field therein, while inhibiting induction of eddy currents in the conducting material; and comparing a signal representative of the impedance of said coil during said juxtapositioning step with said reference signal to provide an output signal indicative of the integrity of said surface and/or sub-surface region of the semi-conductive material, whereby the flaw in the surface and/or sub-surface region of the semi-conductive material may be detected.
Claim 3
Independent Claim
206 words
A method for detecting a flaw in a surface and/or sub-surface region of a semi-conductive material, the semi-conductive material including a conducting material disposed in the sub-surface region at a predetermined distance from the surface of the semi-conductive material, comprising the steps of: providing a continuous run of metal configured spiral-like on a substantially planar but cambered flexible insulative substrate as a uilaminar coil; exciting said coil to produce an electromagnetic field extending from said coil, the electromagnetic field for inducing eddy currents in the surface and/or sub-surface region of the semi-conductive material when said coil is positioned adjacent said material; establishing a reference signal corresponding to the impedance of said coil when said coil is adjacent an unflawed region of said material; juxtapositioning said coil adjacent the surface and/or sub-surface region of the semi-conductive material to induce an electromagnetic field therein, while inhibiting induction of eddy currents in the conducting material; and comparing a signal representative of the impedance of said coil during said juxtapositioning step with said reference signal to provide an output signal indicative of the integrity of said surface and/or sub-surface region of the semi-conductive material, whereby the flaw in the surface and/or sub-surface region of the semi-conductive material may be detected.
Claim 4
Independent Claim
206 words
A method for detecting a flaw in a surface and/or sub-surface region of a semi-conductive material, the semi-conductive material including a conducting material disposed in the sub-surface region at a predetermined distance from the surface of the semi-conductive material, comprising the steps of: providing a continuous run of metal configured spiral-like on a substantially planar but cambered flexible insulative substrate as a uilaminar coil; exciting said coil to produce an electromagnetic field extending from said coil, the electromagnetic field for inducing eddy currents in the surface and/or sub-surface region of the semi-conductive material when said coil is positioned adjacent said material; establishing a reference signal corresponding to the impedance of said coil when said coil is adjacent an unflawed region of said material; juxtapositioning said coil adjacent the surface and/or sub-surface region of the semi-conductive material to induce an electromagnetic field therein, while inhibiting induction of eddy currents in the conducting material; and comparing a signal representative of the impedance of said coil during said juxtapositioning step with said reference signal to provide an output signal indicative of the integrity of said surface and/or sub-surface region of the semi-conductive material, whereby the flaw in the surface and/or sub-surface region of the semi-conductive material may be detected.
Claim 5
Dependent Claim
25 words
The method as in claim 1 or 2, wherein said metal is substantially copper and said coil and said substrate is a printed circuit board.
Claim 6
Dependent Claim
28 words
The method as in claim 1 or 2, wherein exciting includes coupling an excitation signal at a frequency equal to or greater than 7 megahertz to said coil.
Claim 7
Dependent Claim
30 words
The method as in claim 4, wherein the step of establishing a reference signal includes using a substantially balanced impedance bridge circuit having the coil as one of its legs.
Claim 8
Dependent Claim
59 words
The method as in claim 1 or 2, wherein said semi-conductive material consists essentially of carbon and said flaw to be detected is a harline crack in said surface and/or sub-surface region of said semi-conductive material, and further wherein a copper pigtail is disposed in said semi-conductive material at the predetermined distance from the surface of the semi-conductive material.
Claim 9
Dependent Claim
30 words
The method as in claim 6, wherein the step of inhibiting includes exciting said coil at a frequency high enough to inhibit induction of eddy currents in the copper pigtail.
Claim 10
Dependent Claim
15 words
The method as in claim 6, wherein the carbon is in the form of graphite.
References Cited (Backward Citations)
US2955253A
Cited
US3132299A
Cited
US3568049A
Cited
US3901368A
Cited
US3988665A
Cited
US4107605A
Cited
US4109201A
Cited
SU700830A1
Cited
SU824020A1
Cited
US4437062A
Cited
DE3137222A1
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1989-06-02 | 1989-12-02 | 1990-06-03 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1993-06-02 | 1993-12-02 | 1994-06-03 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1997-06-02 | 1997-12-02 | 1998-06-03 | $7700.00 | Window Closed / Lapsed |