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Study on silicon-based MEMS acceleration switch with low threshold acceleration
낮은 임계 가속도를 가지는 실리콘 기반 MEMS 가속도 스위치에 관한 연구

DC Field Value Language
dc.contributor.advisor김용권-
dc.contributor.author황정기-
dc.date.accessioned2017-10-27T16:44:00Z-
dc.date.available2017-10-27T16:44:00Z-
dc.date.issued2017-08-
dc.identifier.other000000145605-
dc.identifier.urihttps://hdl.handle.net/10371/136827-
dc.description학위논문 (박사)-- 서울대학교 대학원 공과대학 전기·컴퓨터공학부, 2017. 8. 김용권.-
dc.description.abstractAbstract

In this paper, MEMS acceleration switch with low threshold acceleration below 10 g and fine environmental characteristics are developed. Limits of the previously reported low-g MEMS switches were addressed in terms of environmental test issues and the solutions for them were suggested and integrated in the proposed low-g MEMS acceleration switch. Fabrication process consists of one silicon-on-insulator substrate and two glass substrates for base and package, respectively. Single-crystalline silicon was chosen as the structural material for high thermal stability and stress-free structure. After the fabrication, height profiles of the free-hanging proof masses were measured to show that the fabricated switches does not suffer from stress problems. The size of single switch was measured as 2150 x 4240 x 1180 µm3 and the average proof mass, initial gap, and the spring constant was 307.38 µg, 6.39 µm, and 3.29 N/m, respectively. The calculated threshold acceleration thus was 6.98 g. In the electrostatic operation test, the response time of the switch was measured to be shorter than 1.2 ms and the minimum contact resistance was 8.5 Ω at the contact force of 284 µN. Life cycle test was carried out to show that the developed switch could operate more than 10,000 cycles without failure. Rotation-table experiment was carried out in sequence to reveal that the switch operates at 6.61 g. The error analysis was carried out in the consideration of the off-axis force generated during the rotation-table experiment. From the experimental values, the off-axis force was calculated as 2.091 μN and the resulting reduction in the initial switching gap was simulated as 0.236 μm. The reduced threshold acceleration thus was estimated to be 6.512 g, which agrees well with the measured threshold acceleration value of 6.61 g. Rotation-table test using another switch was conducted to model the relation between the off-axis force and the operating acceleration of the developed switch. Least squares method was used in the analysis and the original threshold acceleration (a_th) of the switch was calculated as 6.16325 g. The error rate (ε) due to the off-axis force was calculated as -0.22693 g/µN. The modeled operating acceleration of the switch in terms of the off-axis force matched well with the measurements, showing the maximum error less than 1.6%. Heating, sealing, high-g, and impact tests were conducted in sequence to validate the environmental characteristics of the switch. Test condition of 80 °C for 6 hours were adopted for heating test and the tested switch operated more than 200 cycles normally after the test. For sealing test, gross leak test using penetrant dye (Rhodamine B) and fine leak test using tracer gas (helium) were conducted sequentially. 10 samples were put into both of the tests. In the gross leak test, no signs of dye penetration were observed after pressurizing the samples in the dye solution. The tested switches were then put into the fine leak test. In the fine leak test, helium leak rates were measured and all of the tested samples showed leak rate lower than 5.8x10-8 atm cc/s He, which is the reject limit provided by MIL-STD-883E. High-g test and drop impact test were also performed to validate the effectiveness of the displacement-restricting structure. As a result of the high-g test, the developed switch was able to operate without breaking after experiencing the acceleration of 300 g in the ±x ̂, ±y ̂, and ±z ̂ axes. In addition, the drop impact test has proved that the developed switch can withstand an impact as high as 1000 g. The MEMS acceleration switch developed throughout this study is the first to attain low threshold and good environmental characteristics at the same time. Therefore, the author believes that the switch developed in this study is the most suitable one for safety arm unit application among the low-g switches developed so far.
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dc.description.tableofcontents1. Introduction 1
1.1. Sensing of acceleration 1
1.2. Safety arm unit and MEMS acceleration switches 8
1.3. Literature review 14
1.4. Motivation and purpose 19
1.5. Contribution 20
1.6. Composition of thesis 22
2. Theory and design of low-g MEMS acceleration switch 23
2.1. Basic theories on acceleration switch 23
2.1.1 Static threshold acceleration 23
2.1.2 Determining the initial gap 25
2.1.3 Serpentine spring 27
2.1.4 Parallel plate damper 31
2.2. Model description 34
2.2.1 Base glass substrate 36
2.2.2 SOI substrate 36
2.2.3 Packaging glass substrate 37
2.3. FEM simulation 38
2.3.1 Force, displacement, stress simulation 38
2.3.2 Modal analysis Resonant frequency 40
2.4. MATLAB code for MEMS switch 45
3. Fabrication of low-g MEMS acceleration switch 63
3.1. Overall fabrication process 63
3.2. Base glass substrate 65
3.3. SOI substrate 69
3.4. Bonded susbtrate & packaging 72
3.5. Fabrication results 79
4. Characterization of low-g MEMS acceleration switch 84
4.1. DC operation test & lifecycle test 84
4.2. Rotation-table experiments 93
4.3. Effect of the off-axis force on the operating acceleration 101
4.4. Heating test 111
4.5. Sealing test 112
4.6. High-g test & drop impact test 118
5. Conclusion 125
References 128
Abstract (Korean) 136
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dc.formatapplication/pdf-
dc.format.extent4519822 bytes-
dc.format.mediumapplication/pdf-
dc.language.isoen-
dc.publisher서울대학교 대학원-
dc.subjectMEMS (Microelectromechanical Systems)-
dc.subjectAcceleration Switch-
dc.subjectInertial Switch-
dc.subjectLow-g-
dc.subjectLow Threshold Acceleration-
dc.subjectSafety Arm Unit-
dc.subject.ddc621.3-
dc.titleStudy on silicon-based MEMS acceleration switch with low threshold acceleration-
dc.title.alternative낮은 임계 가속도를 가지는 실리콘 기반 MEMS 가속도 스위치에 관한 연구-
dc.typeThesis-
dc.contributor.AlternativeAuthorJeongki Hwang-
dc.description.degreeDoctor-
dc.contributor.affiliation공과대학 전기·컴퓨터공학부-
dc.date.awarded2017-08-
Appears in Collections:
College of Engineering/Engineering Practice School (공과대학/대학원)Dept. of Electrical and Computer Engineering (전기·정보공학부)Theses (Ph.D. / Sc.D._전기·정보공학부)
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