About the Author ............................................. xiii
Foreword ....................................................... xv
Prefece ...................................................... xvii
Acknowledgment ................................................ xxi
Symbols ..................................................... xxiii
CHAPTER 1 Introduction ......................................... i
1.1 Micromachining and Nanofabrication ......................... 1
1.1.1 Micromachining ...................................... 1
1.1.2 Nanofabrication ..................................... 3
1.2 MEMS and Microsystems ...................................... 4
1.3 Conditions for Micromachining and Nanofabrication .......... 6
1.3.1 Conditions for Micromachining ....................... 6
1.3.2 Conditions for Nanofabrication ...................... 7
1.4 Types of Micromachining Processes .......................... 8
1.4.1 Microcutting ........................................ 8
1.4.2 Abrasive Micromachining ............................. 9
1.4.3 Microgrinding ....................................... 9
1.4.4 Micro-USM .......................................... 10
1.4.5 Micro-EDM .......................................... 11
1.4.6 Micro-LBM .......................................... 12
1.4.7 Micro-PAM .......................................... 13
1.4.8 Micro-IBM .......................................... 14
1.4.9 Micro-EBM .......................................... 14
1.4.10 Micro-CM ........................................... 15
1.4.11 Micro-ECM .......................................... 17
1.5 Electrochemical Micromachining ............................ 17
1.5.1 Advantages and Limitations .......................... 19
1.6 Electrochemical Technology for Microsystems and
Nanofabrication ........................................... 21
References ................................................ 22
CHAPTER 2 Electrochemical Machining: Macro to Micro ........... 25
Introduction .............................................. 25
2.1 Background of ECM ......................................... 25
2.1.1 Historical Development of ECM ...................... 26
2.1.2 Basic Features of ECM .............................. 26
2.1.3 Versatility of Today's ECM Techniques .............. 28
2.2 Fundamentals of Anodic Dissolution ........................ 29
2.2.1 Basic Definitions and Laws .......................... 29
2.2.2 Equilibrium Electrode Potentials ................... 36
2.2.3 Irreversible Electrode Potentials .................. 41
2.2.4 Current and Power Efficiency ....................... 43
2.3 Important Influencing Factors of ECM for Micromachining ... 44
2.3.1 Inter-electrode Gap ................................ 45
2.3.2 Double-layer Capacitance ........................... 45
2.3.3 Warburg Impedance .................................. 46
2.3.4 Charge Transfer Resistance ......................... 46
2.3.5 Limiting Current Density ........................... 47
2.3.6 Flushing of Sludge and Gas Bubbles ................. 47
2.3.7 Cavitation ......................................... 48
2.3.8 Passivation ........................................ 48
2.3.9 Deposition on Tool ................................. 49
2.3.10 Electrolyte Boiling ................................ 49
2.3.11 Sparking ........................................... 49
2.4 EMM: Present Status ....................................... 50
References ................................................ 52
CHAPTER 3 Principle of Material Removal in Electrochemical
Micromachining ................................................. 53
3.1 Mechanism of Material Removal ............................. 53
3.1.1 Anodic Reaction and Current Efficiency ............. 53
3.1.2 Mass-Transport-Controlled Anodic Dissolution ....... 54
3.1.3 Current Distribution and Shape Evolution ........... 55
3.2 Equivalent Electrical Circuit for EMM ..................... 56
3.2.1 Basic Equivalent Electrical Circuit for Single
Electrode .......................................... 56
3.2.2 Equivalent Electrical Circuit for Two Electrodes ... 57
3.3 MRR Model ................................................. 60
3.3.1 Basic Formulation of MRR for EMM ................... 61
3.3.2 Formulation of MRR Based on Equivalent Electrical
Circuit Model ...................................... 63
3.3.3 Comparison of Basic Model and Electrical Circuit
Model of MRR for EMM ............................... 65
References ................................................ 67
CHAPTER 4 Types of EMM ........................................ 69
Introduction .............................................. 69
4.1 Through-mask EMM .......................................... 69
4.1.1 One-Sided Through-mask EMM ......................... 72
4.1.2 Two-Sided Through-mask EMM ......................... 73
4.2 MasklessEMM ............................................... 74
4.2.1 Jet EMM ............................................ 75
4.2.2 Microdrilling ...................................... 77
4.3 Three-dimensional EMM ..................................... 79
4.3.1 Die-sinking EMM .................................... 79
4.3.2 EMM by Scanning .................................... 79
References ................................................ 82
CHAPTER 5 Electrochemical Micromachining Setup ................ 83
5.1 Details of EMM Setup ...................................... 83
5.1.1 Mechanical Machining Unit .......................... 83
5.1.2 Other Supporting Subunits .......................... 86
5.2 Current Status of Developments in EMM Setup ............... 87
5.3 lEG Control Strategy ................................. 94
References ................................................ 99
CHAPTER 6 Design and Developments of Microtools .............. 101
Introduction ............................................. 101
6.1 Types of EMM Tools ....................................... 101
6.2 Microtool Design for EMM ................................. 102
6.3 Methods of Microtool Fabrication ......................... 103
6.3.1 Electrodischarge Machining ........................ 103
6.3.2 Reverse EDM ....................................... 104
6.3.3 Single Pulse EDM .................................. 105
6.3.4 Focused Ion Beam Machining ........................ 107
6.3.5 Reverse ECM ....................................... 108
6.4 EMM for Microtool Fabrication ............................ 109
6.4.1 Electrochemical Etching ........................... 109
6.4.2 Drop-off Method ................................... 109
6.4.3 Selective Electrochemical Dissolution ............. 114
6.4.4 Electrochemical Deposition ........................ 115
6.5 Different Features of Microtools Fabricated by EMM .. 116
6.5.1 Shape and Size of Cylindrical Microtools .......... 117
6.5.2 Surface Quality of Microtools ..................... 118
References ............................................... 120
CHAPTER 7. Influencing Factors of EMM ......................... 123
Introduction ............................................. 123
7.1 EMM Power Supply ......................................... 123
7.1.1 Pulse D.C. Power Supply ........................... 124
7.1.2 Configuration of Pulse Power Supply Unit .......... 125
7.1.3 Influence of Power Parameters ..................... 127
7.2 Electrolyte for EMM ...................................... 134
7.2.1 Types of Electrolyte .............................. 134
7.2.2 Eco-friendly Electrolyte .......................... 136
7.3 Influence of IEG ......................................... 136
7.4 Influence of Temperature, Concentration, and Electrolyte
Flow ..................................................... 138
7.4.1 Temperature ....................................... 138
7.4.2 Concentration ..................................... 139
7.4.3 Electrolyte Flow .................................. 140
7.5 Influence of Tool Feed Rate .............................. 141
References ............................................... 142
CHAPTER 8 Improvement of Machining Accuracy .................. 145
Introduction ............................................. 145
8.1 Tool Insulation .......................................... 145
8.2 Electrolyte Circulation .................................. 149
8.3 Shape of the Microtool ................................... 150
8.4 Tool Movement Strategy ................................... 151
8.5 Stray Current and Microsparks Phenomena in EMM ........... 152
8.6 Hybrid EMM ............................................... 155
8.7 Selection of Combination of Machining Parameters ......... 157
References .................................................... 164
CHAPTER 9 Advantages, Limitations, and Applications
of EMM ........................................................ 167
Introduction ............................................. 167
9.1 Advantages ............................................... 167
9.1.1 Material and Product Advantages ................... 167
9.1.2 Machine Advantages ................................ 168
9.1.3 Development and Usability of Microtools ........... 168
9.1.4 Economics of Operation ............................ 168
9.2 Applications ............................................. 169
9.2.1 Machining Applications ............................ 169
9.2.2 Finishing Applications ............................ 173
9.2.3 Surface Engineering Applications .................. 177
9.3 Limitations and Remedies ................................. 180
9.3.1 Oxide Layer Formation ............................. 180
9.3.2 Metal Deposition on Microtool ..................... 181
9.3.3 High Aspect Ratio Microfeatures ................... 181
9.3.4 Stray Current Effect .............................. 182
9.3.5 Machining Time .................................... 182
9.3.6 Online Monitoring ................................. 182
9.3.7 Microtool Handling ................................ 183
References .................................................... 183
CHAPTER 10 Microdevices Fabrication for
Microelectromechanical Systems and Other Microengineering
Applications .................................................. 185
Introduction ............................................. 185
10.1 Microelectromechanical Systems ........................... 185
10.1.1 Microfeatures by EMM for MEMS ..................... 186
10.1.2 High-Aspect-Ratio Features for MEMS ............... 194
10.2 Semiconductor Micromachining by EMM ...................... 197
10.2.1 Back-Side Illumination EMM Technique for Silicon .. 197
10.3 Microengineering Applications ............................ 198
10.3.1 Metal Mask ........................................ 199
10.3.2 Fabrication of Bipolar Plate ...................... 199
10.3.3 Profiled Microhole, Spiral Beam, and Array of
Square Columns .................................... 201
10.3.4 Generation of Helical Microrecesses ............... 201
10.3.5 Fabrication of Complex Internal Microfeature ...... 202
References ............................................... 204
CHAPTER 11 Electrochemical Microsystem Technology ............ 205
Introduction ............................................. 205
11.1 Features of EMST ......................................... 205
11.2 Scaling Down and Scaling Up .............................. 206
11.3 Electrochemical Microcell and Microelectrode ............. 207
11.3.1 Microcell ......................................... 207
11.3.2 Microelectrode .................................... 208
11.4 Electrochemical Reactions in EMST ........................ 210
11.5 Applications of EMST in Microsystem Technology ........... 211
11.5.1 Phosphating Process ............................... 212
11.5.2 Ultrahigh Density Magnetic Recording .............. 213
11.5.3 Micropump and Dosing System ....................... 214
11.5.4 Miscellaneous Applications of EMST ................ 215
References ............................................... 216
CHAPTER 12 Recent Advancements in EMM for Micro and
Nanofabrication ............................................... 219
Introduction ............................................. 219
12.1 Wire EMM ................................................. 220
12.2 Solid-State EMM .......................................... 222
12.3 Surface Structuring ...................................... 224
12.3.1 Surface Structuring of Aluminum ................... 227
12.3.2 Surface Structuring of Titanium ................... 229
12.4 Electrochemical Wet Stamping ............................. 231
12.5 Electrochemical Patterning by EnFACE Technology .......... 233
12.6 Nanofabrication by EMM ................................... 236
References ............................................... 238
CHAPTER 13 Nanofeatures on Metals and Semiconductors for
Nanotechnology Applications ................................... 241
Introduction ............................................. 241
13.1 Electrochemical Nanotechnology ........................... 241
13.1.1 Principle of ENT .................................. 242
13.1.2 Localization of Reactions for Nanostructure
Formation ......................................... 242
13.1.3 Electrochemical Nanocell .......................... 244
13.2 Nanofeatures on Metals and Semiconductors ................ 246
13.2.1 Electrochemical Printing .......................... 246
13.2.2 Electrochemical Etching of Nanotrench on
Semiconductors .................................... 247
13.2.3 Electrochemical Nanostructuring by SPM ............ 248
13.2.4 Electrochemical Nanofabrication by AFM Tip ........ 252
References ............................................... 256
Index ......................................................... 259
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