US4446432A
Expired / Lapsed
US
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Method for determining surface contour of piezoelectric wafers
Assignee: CTS Corp
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Filing: 1982-05-27
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Granted: 1984-05-01
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Expires: 2002-05-27
Abstract
Abstract A method utilizing a localized electrical field to precisely determine the surface contour of a substantially flat wafer of piezoelectric material having a slight convexity in its opposing faces.
Inventors
- 👤 Lawrence N. Dworsky
- 👤 Garth R. Kennedy
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 19:36
CPC Classifications
G; G01; G01B; G01B7/00; G01B7/28; G01B7/34; G01B7/345
Claims Analysis
Total Claims: 3
Claim 1
Independent Claim
223 words
A method of determining the radius of curvature, R, of the surface contour of a convex wafer of piezoelectric material, comprising: applying a localized electrical field to an arbitrary location on a face of the wafer while monitoring the frequency response to determine the Oth order frequency of the wafer; traversing the face of the wafer with said localized electrical field while monitoring the amplitude of the response at said Oth frequency until the location of maximum amplitude is found, said location corresponding to the point of maximum thickness, 2h o , of said wafer; moving said localized electrical field from said location of maximum thickness along one of the planar axes of the wafer until an amplitude peak for the next mode is obtained, measuring the distance traversed, a, and solving the following equation for β: ##EQU7## and using the value obtained for β to solve one of the following equations for R: ##EQU8## where N is the mode along the y thickness axis, C 66 =C 66 +e 26 2 /ε 22 where C 66 is an elastic coefficient of the piezoelectric material, e 26 is a piezoelectric coupling coefficient and ε 22 is a dielectric constant of the piezoelectric material in the thickness direction of the wafer, and C 11 , C 55 are elastic coefficients of the piezoelectric material.
Claim 2
Independent Claim
223 words
A method of determining the radius of curvature, R, of the surface contour of a convex wafer of piezoelectric material, comprising: applying a localized electrical field to an arbitrary location on a face of the wafer while monitoring the frequency response to determine the Oth order frequency of the wafer; traversing the face of the wafer with said localized electrical field while monitoring the amplitude of the response at said Oth frequency until the location of maximum amplitude is found, said location corresponding to the point of maximum thickness, 2h o , of said wafer; moving said localized electrical field from said location of maximum thickness along one of the planar axes of the wafer until an amplitude peak for the next mode is obtained, measuring the distance traversed, a, and solving the following equation for β: ##EQU7## and using the value obtained for β to solve one of the following equations for R: ##EQU8## where N is the mode along the y thickness axis, C 66 =C 66 +e 26 2 /ε 22 where C 66 is an elastic coefficient of the piezoelectric material, e 26 is a piezoelectric coupling coefficient and ε 22 is a dielectric constant of the piezoelectric material in the thickness direction of the wafer, and C 11 , C 55 are elastic coefficients of the piezoelectric material.
Claim 3
Dependent Claim
104 words
The method of claim 1 wherein the maximum thickness, 2h o , of the wafer is determined solving the equation: ##EQU9## where ω is the resonant frequency in radians for the Nth y axis overtone, the Mth x axis overtone and the Pth z axis overtone, C 66 =C 66 +e 26 2 /ε 22 where C 66 is an elastic coefficient of the piezoelectric material, e 26 is a piezoelectric coupling coefficient and ε 22 is a dielectric constant of the piezoelectric material in the thickness direction of the wafer, anc C 11 and C 55 are elastic coefficients of the piezoelectric material.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1987-05-01 | 1987-10-31 | 1988-05-01 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1991-05-01 | 1991-10-31 | 1992-05-01 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1995-05-01 | 1995-10-31 | 1996-05-01 | $7700.00 | Window Closed / Lapsed |