08-16-2017, 08:51 PM
MODERN STRAIN MEASUREMENT USING POLYSILICON GAUGE
VIKAS P
Roll no 69
S7 AEI,
College Of engineering, Trivandrum
Outline
General Overview of STRAIN GAUGE
Strain gauge, Classification ,Why Thin Polysilicon Strain Gauge?,
Miniaturation, Conventional strain gauge vs. polysilicon gauge
Fabrication Process of Thin Polysilicon Gauge
Fabrication steps,glass frit bonding,..
Experimental Analysis and Results
Performance evaluation
Conclusion
Strain Gauge
Distribution of stress in structures are measured by strain measurement techniques(using strain gauge) since strain can be measured by Hooke s law.
Basic principle-length change of a wire causes a resistance change, which is measured by a strain gauge.
To provide a means of comparing the performance of various gage materials, the gage factor, or strain sensitivity, of a gage is defined as
Classification
-Mechanical
-optical
-acoustic
-electrical
-semiconductor
Semiconductor Strain Gages
Strain-gage technology advanced in the 1960s with the introduction of the semiconductor strain-gage elements
Silicon gages are formed from single-crystal silicon whose orientation and doping are the most important design parameters.
Semiconductor gages are made by slicing sections from specially processed silicon crystals and are available in both n and p types. The high gage factor is accompanied by high-temperature sensitivity, nonlinearity, and mounting difficulties.
Polysilicon gages utilize the diffusion process employed in integrated-circuit manufacture. Lower manufacturing costs in some designs, since a large number of devices can be made on a single silicon wafer. The deviation from linearity is approximately 1%
Why SC strain gauge?
Improved performance
Batch fabrication-Reduced manufacturing cost and time
Miniaturization
Low power consumption
Higher speed & hence less delay
Higher resonant frequency
Reliability
Portability
Ruggedness
Nonlinearity 0.21%FS & hysteresis 0.17%FS
Improved Gauge factor (20-50)
Fabrication
Fabricated thin polysilicon gauge
Experimental Analysis & Results
Endpoint deflection of cantilever beam was measured by IR displacement sensor ,strain is given by
Length & thickness of cantilever beam is 200 & 3mm
Observe characteristics with changes in temperature, constant temperature chamber was installed around the polysilicon strain gauge.
GF, TCR, Nonlinearity, Hysteresis were measured
Conclusion
Proposed Thin Polysilicon Strain Gauge have all the desirable quality of good strain gauge.
Excellent linearity
Sensitivity is much higher than that of a conventional metal-foil strain gauge, and the TCR is significantly lower than that of monosilicon
strain gauges.
MEMS fabrication technology were used.
Use of glass frit bond improves mechanical properties of Hysteresis, Repeatability and Durability.
Minimum Nonlinearity
References
IEE SENSORS JOURNAL, VOL. 10,NO. 8,AUGUST 2010 THIN POLYSILICON GAUGE FOR STRAIN MEASUREMENT OF STRUCTURAL ELEMENTS BY YONGDAE KIM, YOUNGDEOK KIM, CUULSUB LEE, SEJIN KWON.
IEE MICRO & NANO LETTERS,2010 ,VOL. 5, ISS. 3- RESISTIVITY DEPENDENCE OF GAUGE FACTOR OF POLYSILICON STRAIN GAUGE.
Wafer bonding A/P Francis Tay ,Dr. Ciprian Iliescu
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