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Bulk Foil Pt-Rh Micro-Relays for High Power Rf and Other Applications

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Bulk Foil Pt-Rh Micro-Relays for High Power Rf and Other Applications BULK FOIL PT-RH MICRO-RELAYS FOR HIGH POWER RF AND OTHER APPLICATIONS by Fatih Mert Ozkeskin A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy (Mechanical Engineering) in The University of Michigan 2011 Doctoral Committee: Professor Yogesh B. Gianchandani, Chair Professor Kamal Sarabandi Associate Professor Katsuo Kurabayashi Assistant Professor Mina Rais-Zadeh © Fatih Mert Ozkeskin 2011 To father, Tayfur Ozkeskin ii ACKNOWLEDGEMENTS First of all, I would like to thank and express my deepest gratitude to my research advisor Professor Yogesh B. Gianchandani for his endless support, mentoring and encouragement throughout my doctoral study. Second of all, I would like to thank Professor Kamal Sarabandi for his invaluable guidance. I would also like to thank Professor Katsuo Kurabayashi and Professor Mina Rais-Zadeh for being in my dissertation committee. I would like to thank Dr. Tao Li and Dr. Mark Richardson for being great mentors and for training me on the µEDM which I have used extensively. I would also like to thank to Sangjo Choi, for spending a great deal of effort and countless of hours for RF design and testing. I would like to thank to Dr. Adip Nashashibi for helping with RF testing equipment. I am also indebted to all the WIMS and SSEL staff especially to Trasa Bukhardt and Fran Doman for taking care of all my administrative work and research purchases. I would like to thank my research group members Tao, Naveen, Karthik, Christine, Scott Wright, Scott Green, Allan, Heidi, Erwin, Jun, Ravish, Seungdo and Xin. It has been a wonderful experience working with them all along. I would also like to thank my friends, Erkan, Razi, Angelique, Ali, Jae Yoong, Daniel, Jeff, James, Seow Yuen, Tzeno, Yonghyun, Zhengzheng, Vikrant, Vikram, Morteza, Fikadu, Meysam, iii Mehrnoosh, Jungsuek and many others who have made my years at The University of Michigan memorable ones. Finally, I would like to thank my parents and my sister for their unlimited love, support and encouragement without which I would have never reached this day. iv TABLE OF CONTENTS DEDICATION .............................................................................................................. ii ACKNOWLEDGEMENTS ......................................................................................... iii LIST OF FIGURES ................................................................................................... viii LIST OF TABLES ....................................................................................................xviii ABSTRACT ................................................................................................................ xix Chapter 1. INTRODUCTION ........................................................................................... 1 1.1 Types of micro-relays ........................................................................ 2 1.1.1 DC micro-relays ................................................................. 2 1.1.2 RF micro-relays .................................................................. 4 1.2 Performance measures of MEMS switches ........................................ 7 1.2.1 Figure of merit .................................................................. 10 1.2.2 Actuation voltage ............................................................. 12 1.2.3 Power handling ................................................................. 16 1.2.4 Switching speed ................................................................ 16 1.3 Contact resistance and material considerations in ohmic-contact micro-relays........................................................................................18 1.3.1 Theoretical model ............................................................. 18 1.3.2 Contact metal selection ..................................................... 21 1.4 Micro electro-discharge machined bulk foil Pt-Rh relays for high power applications ................................................................... 22 1.4.1 Platinum-rhodium ............................................................. 23 1.4.2 Micro electro-discharge machining ................................... 24 1.5 Hybrid assembly and packaging on the printed circuit boards .......... 28 1.6 Goals and approach…. .................................................................... 30 1.7 Outline................................................................................................31 v 2. POWER HANDLING OF MEMS SWITCHES .......................................... 32 2.1 Failure mechanisms and power handling of MEMS switches .......... 33 2.1.1 Low-medium power failure mechanisms for MEMS capacitive switches….. ..................................................... 33 2.1.2 Low-medium power failure mechanisms for MEMS ohmic-contact switches ..................................................... 36 2.1.3 High power failure mechanisms for MEMS capacitive switches………….. ........................................................ ..36 2.1.4 High power failure mechanisms for MEMS ohmic- contact switches ................................................................ 38 2.2 Quantitative benchmarking ............................................... 40 3. MICROMACHINED Pt-Rh AND STAINLESS STEEL RELAYS FOR HIGH POWER DC APPLICATIONS ................................................ 43 3.1 Design…. ........................................................................................ 43 3.2 Fabrication and assembly…. ............................................................ 53 3.3 Experimental evaluation…. ............................................................. 58 3.3.1 Electrical testing ............................................................... 58 3.3.2 Thermal testing ................................................................. 61 3.3.3 Lifetime testing ................................................................ 65 3.4 Discussion and conclusions…. ........................................................ 66 4. AN ALL-METAL MICRO-RELAY WITH BULK FOIL Pt-Rh CONTACTS FOR HIGH POWER RF APPLICATIONS .......................... 69 4.1 Design…. ........................................................................................ 70 4.2 Fabrication and assembly…. ............................................................ 79 4.3 Experimental evaluation…. ............................................................. 83 4.3.1 Electrical testing ............................................................... 83 4.3.2 Thermal testing ................................................................. 88 4.3.3 Lifetime testing ................................................................ 90 4.4 Discussion and conclusions…. ........................................................ 91 5. BATCH FABRICATED HIGH POWER RF MICRO-RELAYS WITH DIRECT ON-PCB PACKAGES ....................................................... 93 5.1 Design…. ........................................................................................ 93 5.2 Fabrication and assembly…. .......................................................... 104 5.3 Experimental evaluation…. ........................................................... 108 vi 5.3.1 Electrical testing ............................................................. 108 5.3.2 Lifetime testing .............................................................. 117 5.3.3 Package testing ............................................................... 117 5.4 Discussion and conclusions…. ...................................................... 118 6. CONCLUSIONS AND FUTURE WORK .................................................. 123 6.1 Conclusions…. .............................................................................. 123 6.2 Future work…. .............................................................................. 127 APPENDIX ................................................................................................................ 131 BIBLIOGRAPHY ...................................................................................................... 147 vii LIST OF FIGURES Figure 1.1: The SEM photographs of the micro-relays with different structures (a) A micro-relay with plate electrodes, (b) a micro-relay with a single beam and a single comb drive, (c) a micro-relay with a double-fold beam and a pair of comb drives [Li00]……………………………………………………………………………………...3 Figure 1.2: Orthogonal MEMS-series switches with (a) one electrode, (b) two electrodes, and (c) inline MEMS-series switches [Reb01] …………………………………………...9 Figure 1.3: Raytheon MEMS capacitive shunt switch: (a) cross-section view and (b) electrical RLC model [Gol96, Gol98]………………………………………………….....9 Figure 1.4: S-parameters of a MEMS capacitive shunt switch, (a) up-state position and (b) down-state position [Mul00]…………………………………………………………12 Figure 1.5: (a) A MEMS fixed-fixed (suspended) beam, (b) cantilever beam [Reb03] ……………………………………………………………………………………………12 Figure 1.6: The beam height versus the applied voltage for exemplary values of W=w=100 µm, g0=3 µm and k=10 N/m. The pull-in voltage is 30 V. Dashed line is the unstable portion of the beam height [Reb03]……………………………………...……..15 Figure 1.7: (a) Cross section of a miniature switched capacitor, (b) SEM picture a miniature switched capacitor [Lac06]……………………………………………………17 Figure 1.8: (a) Surface profile of contact having multiple asperities, (b) calculated contact radius versus contact force for a gold contact [Maj97]
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