• Proceedings of the IEEK Conference
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• 2004.08c
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• pp.872-875
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• 2004

In this paper, thermal response analysis of a temperature controlled three-axis accelerometer for high temperature environments with integrated micro-heaters and temperature sensors is investigated with finite element method (FEM) program, ANSYS and infrared thermal measurement systems. And availability to application fields from a viewpoint about short thermal response time is discussed. In this paper, the time of three-axis accelerometer for high temperatures becoming $300^{\circ}C$ by integrated micro-heaters and temperature sensors to reduce thermal drift characteristics was analyzed as a thermal response time of this device. The simulated thermal response time (time until SOI piezoresistors actually becomes $300^{\circ}C$) of three-axis accelerometer for high temperatures with ANSYS is about 0.6s, and measured result with infrared temperature measurement systems is about 0.64s. Experimental results using infrared thermal measurement systems agreed well with these theoretical results.

• Proceedings of the KSME Conference
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• 2005.11a
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• pp.161.1-161.1
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• 2005

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.1951-1956
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• 2008

Various MEMS accelerometers are used in engineering applications including automobiles, mobile phones, military systems, and electronic devices. Among them, the thermal accelerometer employing the temperature difference induced by the convective flow inside the micro cavity has been a topic of interest. As the convective sensor does not utilize a solid proof mass, it is compact, lightweight, inexpensive to manufacture, sensitive and highly endurable to mechanical shock. However, the complexity of the convective flow and various design constraints make optimization of a device a crucial step before fabrication. In this work, optimization of a 2-axis thermal convective MEMS accelerometer is conducted based on 3-dimensional numerical simulation. Parametric studies are performed by varying the several design variables such as the heater shape/size, the cavity size and types of the gas medium and the position of temperature probes in the sensor. The results of optimal design are presented.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.5
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• pp.570-577
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• 2007

A micromachined convective accelerometer is a recently developed device. Typical micromachined accelerometers use a solid proof mass for measuring acceleration. But a micromachined convective accelerometer does not use a solid proof mass. A micromachined convective accelerometer is composed of a heating resistor and temperature sensors. This device measures acceleration by using convective heat transfer phenomenon. Therefore characteristics of a micromachined convective accelerometer are different as compared with typical micromachined accelerometer. In this research, we analyze the convective accelerometer by using transient convective heat transfer analysis. Based on the results of a convective accelerometer, we propose a new model which has improved performance.

• Journal of Sensor Science and Technology
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• v.9 no.1
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• pp.1-8
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• 2000

One of today's very critical and sensitive accurate accelerometer which can be used higher temperature than $200^{\circ}C$ and corrosive environment, is particularly demanded for automotive engine. Because silicon is a material of large temperature dependent coefficient, and the piezoresistors are isolated with p-n junctions, and its leakage current increase with temperature, the performance of the silicon accelerometer degrades especially after $150^{\circ}C$. In this paper, The temperature characteristic of a accelerometer using silicon on insulator (SOI) structure is studied theoretically, and compared with experimental results. The temperature coefficients of sensitivity and offset voltage (TCS and TCO) are related to some factors such as thermal residual stress, and are expressed numerically. Thermal stress analysis of the accelerometer has also been carried out with the finite-element method(FEM) simulation program ANSYS. TCS of this accelerometer can be reduced to control the impurity concentration of piezoresistors, and TCO is related to factors such as process variation and thermal residual stress on the piezoresistors. In real packaging, The avarage thermal residual stress in the center support structure was estimated at around $3.7{\times}10^4Nm^{-2}^{\circ}C^{-1}$ at sensing resistor. The simulated ${\gamma}_{pT}$ of the center support structure was smaller than one-tenth as compared with that of the surrounding support structure.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.34D no.7
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• pp.30-36
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• 1997

Bump bonded piezoesistive silicon accelerometer was fabricated by the porous silicon micromachining and th eprocess technique of integrated circuit. The output voltage of the accelerometer fabricated on (111)-oreiented Si substrates with n/n$^{+}$n triple layers showed good linear characteristic of less than 1%. The measured sensitivity and the resonant frequency was about 743 .mu.V/g and 2.04 kHz, respectively. And the transverse sensitivity of 5.2% was measured from the accelerometer. Also, to investigate an influence on the output characteristics of the sensor due to bump bonding, the values of the piezoresistors were measured through thermal-cycling test in the temperature variation form -50 to 120.deg. C. Then, there was 0.014% resistance changes about 3.61 k.ohm., so sthe output charcteristics of the sensor was less affected by bump bonding.g.

• Proceedings of the KWS Conference
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• 2007.11a
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• pp.76-78
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• 2007

• Journal of Power System Engineering
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• v.5 no.2
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• pp.36-42
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• 2001

This paper deals with finite element analyses of residual stresses causing popping up which are induced in micromachining processes of a microaccelerometer sensors. The paddle of the micro accelerometer sensor is designed symmetric with respect to the direction of the beam. After heating the tunnel gap up to 100 degree and get it through the cooling process and the additional beam up to 80 degree and get it through the cooling process. We learn the thermal internal stresses of each shape and compare the results with each other, after heating the tunnel gap up to 400 degree during the Pt deposition process. Finally we find the optimal shape which is able to minimize the internal stresses of microaccelerometer sensor. We want to seek after the real cause of this pop up phenomenon and diminish this by change manufacturing processes of microaccelerometer sensor by electrostatic force.

• Proceedings of the KSME Conference
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• 2000.11a
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• pp.516-521
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• 2000

Most of studies, using ESPI method, have handled tension, thermal and vibration analysis, and is limited to isotropic materials. However, tension and vibration simultaneously are loaded in real structure. Also, almost study using ESPI method is locally limited to the analysis on the isotropic materials and a few studies on the anisotropic materials have reported. Existing methods, such as the accelerometer method and FEA method, to analyze vibration have some disadvantages. Using the accelerometer method that is generally used to analyze vibration phenomena, it is impossible to analyze vibration on the oscillating body and one can observe no vibration mode shape during experiment. In case of the FEA method, it is difficult to define boundary conditions correctly if the shape of a body tested is complex, and one can just obtain vibration mode shapes on the peak amplitude in each modes. In this study, plane plate of stainless steel(STS304), isotropic material, that is used as structural steel is analyzed about vibration characteristics under tension. Also, in the study of stainless steel, the characteristics of composite material(AS4/PEEK) used as high strength structural material in aircraft is evaluated about vibration under tension, and studies the effect of tension on vibration.

• Proceedings of the KIEE Conference
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• 1996.11a
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• pp.425-427
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• 1996

New fabrication technique was developed to make three dimensional silicon microstructure with five fold vertical steps through entire wafer thickness. Each step is pre-defined on multiply stacked thermal oxide and silicon nitride (O/N) layers by photolithographies. Multi-stepped silicon microstructure is formed by anisotropic etch in aqueous KOH solution with the patterned nitride film as masking layer. Fabricated microstructure consists of four $16{\mu}m$ thick flexural spring beams, $290{\mu}m$ thick proof mass, mesas for overrange stop with $10{\mu}m$ height from the surface of the proof mass, and the other mesas and V grooves used for assembling this structure to the packaging frame of pendulous servo accelerometer. Using the numerical finite element method (FEM) simulator: ABAQUS, mechanical characteristics of the fabricated microstructure by the developed technique was compared with those of the same structure processed by one step silicon bulk etch followed by oxidation and patterning the etched region.