Surface Mount Technology

✍ Scribed by Rudolf Strauss

• Publisher: Butterworth-Heinemann
• Year: 1994
• Tongue: English
• Leaves: 390
• Category: Library

✦ Synopsis

Surface mount technology has had a profound influence on the electronics industry. Changes have involved the use of new materials, techniques and manufacturing processes, and have resulted in a significantly new approach to electronics assembly. This guide covers SMDs, soldering (including reflow and wave soldering), component placement, cleaning and quality control. This book aims to explain the principles of surface mount technology for practical application, rather than dwelling on theory, and so should find use in any facility employing SMT as well as those considering switching to it.

✦ Table of Contents

Contents......Page 6
Preface to the first edition......Page 13
Preface to the second edition......Page 15
Glossary......Page 17
1 Why SMDs?......Page 20
References......Page 24
2.1.1 Melfs and chips......Page 25
2.1.2 LCCCs......Page 27
2.2 High-pincount components......Page 28
2.2.1 TABs......Page 29
2.2.2 Flip-chips and BGAs......Page 30
2.3 Multichip modules......Page 32
2.4.1 Melfs and chips......Page 33
2.4.2 Components with legs......Page 34
2.6 The popcorn effect......Page 35
2.7 References......Page 37
3.1.1 The roles of solder, flux and heat......Page 39
3.1.2 Soldering methods......Page 40
3.2.1 Constituents, melting behaviour and mechanical properties......Page 43
3.2.2 Composition of solders for use in electronics......Page 46
3.2.3 Lead-free solders......Page 48
3.2.4 Solder impurities......Page 50
3.3.1 Soldering as a surface reaction between a molten and a solid metal......Page 56
3.3.2 Structure and characteristics of the soldered joint......Page 57
3.3.3 Mechanical properties of soldered joints......Page 59
3.3.4 Soldering on surfaces other than copper......Page 60
3.3.5 Long-term behaviour of soldered joints......Page 62
3.3.6 Long-term reliability of soldered joints......Page 63
3.4.1 Tasks and action of the soldering flux......Page 64
3.4.2 Wetting and interfacial tension......Page 66
3.4.3 Properties required in a flux......Page 67
3.4.4 Rosin fluxes......Page 69
3.4.5 Low-solids and no- clean fluxes......Page 71
3.4.6 Watersoluble fluxes......Page 72
3.4.8 Flux standards......Page 73
3.4.9 Testing soldering fluxes......Page 76
3.5.1 Heat requirements and heat flow......Page 79
3.5.2 Heating options......Page 80
3.6.1 Wetting and dewetting......Page 82
3.6.3 Capillarity and joint configuration......Page 84
3.6.5 Oxide layers......Page 88
3.6.6 Solderability-enhancing surface coatings......Page 90
3.6.7 Leaching effect of molten solder......Page 92
3.6.8 Measuring solderability......Page 93
3.7 References......Page 100
4.1.2 Wavesoldering after SMDs......Page 103
4.2 Applying the flux......Page 104
4.2.1 Types of fluxer......Page 106
4.2.2 Monitoring and controlling flux quality......Page 115
4.3.1 Heat requirements......Page 117
4.3.2 Heat emitters and their characteristics......Page 119
4.3.3 Temperature control......Page 121
4.4.1 Construction of the soldering unit......Page 122
4.4.2 Thermal role of the solderwave......Page 123
4.4.3 Interaction between molten solder and the circuit board......Page 124
4.4.4 Chipwaves......Page 129
4.4.5 Formation and control of dross......Page 133
4.5.1 Origins and development......Page 137
4.5.2 Wavesoldering in nitrogen......Page 138
4.6.2 Board-handling systems......Page 145
4.7.1 Operating parameters and their role......Page 149
4.7.2 Choosing and monitoring operating parameters......Page 150
4.7.3 Optimizing machine parameters......Page 155
4.7.4 Machine maintenance......Page 156
4.7.6 Dealing with dross......Page 157
4.7.7 Hygiene and safety......Page 158
4.8.2 Storage and handling behaviour of adhesives......Page 160
4.8.3 Applying the adhesive......Page 162
4.8.4 Curing the adhesive joint......Page 164
4.8.5 The glass transition temperature......Page 165
4.9 References......Page 166
5.1.1 SMDs and reflowsoldering......Page 167
5.1.2 Reflowsoldering versus wavesoldering......Page 173
5.2.1 Operational requirements......Page 177
5.2.2 Standard specifications......Page 178
5.2.3 Solderpowder......Page 179
5.2.4 The flux and its residue......Page 183
5.2.5 Printing and dispensing properties......Page 184
5.2.6 The solderball test......Page 186
5.3.1 Single-spot dispensing......Page 188
5.3.2 Stencilling and screen printing......Page 190
5.3.3 Depots of solid solder......Page 197
5.4.1 The basic concept......Page 198
5.4.3 The physics of vapourphase soldering......Page 199
5.4.4 Vapourphase soldering equipment......Page 203
5.4.5 'New-generation' vapourphase soldering systems......Page 205
5.5.1 Working principle......Page 208
5.5.2 The physics of heat transfer by radiation......Page 210
5.5.3 The physics of heat transfer by convection......Page 219
5.5.4 Operation of infrared ovens......Page 220
5.5.5 Oven design......Page 222
5.5.6 Infrared soldering in a controlled atmosphere......Page 227
5.6.1 Convection versus radiation......Page 228
5.6.3 Convection reflow ovens......Page 229
5.6.4 Development potential of convection reflowsoldering......Page 231
5.6.5 Convection soldering of single components......Page 233
5.7 Laser soldering......Page 236
5.7.2 Nd: YAG and CO2 lasers......Page 237
5.7.3 Laser soldering in practice......Page 239
5.7.4 Laser-soldering equipment......Page 240
5.8.1 Operating principle......Page 242
5.8.2 The solder depot......Page 243
5.8.3 The thermode and its heating cycle......Page 244
5.8.4 Impulse-soldering equipment......Page 246
5.9 SMD soldering methods - A survey......Page 247
Vapourphase soldering......Page 248
Convection soldering of single components......Page 249
Impulse soldering of single components......Page 250
5.10 References......Page 251
6.2 SMD-specific demands on a circuit board......Page 253
6.3 Thermal management......Page 255
6.3.2 Effects of temperature differences between components and board......Page 256
6.4 Solderable surfaces......Page 257
6.4.2 Hot tinning......Page 258
6.4.3 Organic coatings......Page 260
6.4.4 Flat solder depots......Page 261
6.6.1 Layout for wavesoldering......Page 263
6.6.2 Layout for reflowsoldering......Page 266
6.7 References......Page 268
7.1 The task......Page 269
7.2 Reliability of placement......Page 270
7.3.1 Fully manual placement......Page 272
7.3.2 Semi- automatic placement......Page 274
7.3.3 Fully automatic sequential systems......Page 275
7.3.4 Simultaneous placement systems......Page 276
7.4.1 The range of choice......Page 277
7.4.2 Classes of placement machines......Page 278
7.5 Reference......Page 279
8.1 Basic considerations......Page 280
8.1.1 Reasons for cleaning......Page 282
8.1.2 Designing for cleanability......Page 285
8.1.3 What must be removed?......Page 286
8.2.1 The physics of cleaning......Page 288
8.2.2 The chemistry of cleaning......Page 293
8.3 The practice of cleaning......Page 295
8.3.1 Organic solvents......Page 296
8.3.2 Solvent-cleaning installations......Page 301
8.3.3 In-line cleaning plants......Page 307
8.3.4 Halogenated solvents: safety and health......Page 310
8.3.5 The three environmental threats......Page 312
8.3.6 Restrictions on solvent usage......Page 316
8.3.7 Non-flammable organic solvents with reduced environmental risks......Page 317
8.3.8 Flammable solvents......Page 318
8.4.1 Chemical and physical aspects......Page 321
8.4.2 Water quality......Page 322
8.4.3 Water recycling and effluent problems......Page 324
8.4.5 Removal of residue from resinous fluxes......Page 325
8.4.6 Water washing installations......Page 326
8.5.1 The concept......Page 329
8.5.2 The cleaning solvents......Page 330
8.5.3 Semi-aqueous washing installations for water- immiscible solvents......Page 332
8.5.4 Semi-aqueous washing installations for water- miscible solvents......Page 334
8.6.1 The meaning of cleanliness......Page 337
8.6.2 Measuring ionic contamination (MIL test)......Page 338
8.6.3 Measuring surface insulation resistance (SIR)......Page 340
8.7 The future of cleaning and of fluxing......Page 341
8.8 References......Page 342
9.1.1 Product quality and product reliability......Page 344
9.1 The meaning of ‘quality’......Page 0
9.1.2 Classification according to reliability requirements......Page 345
9.2.1 Soldering success and soldering faults......Page 346
9.2.2 Soldering perfection and soldering imperfections......Page 349
9.5 Inspection......Page 351
9.5.1 When to inspect......Page 354
9.5.2 Visual inspection......Page 356
9.5.4 X-ray inspection......Page 357
9.6 References......Page 359
10.1.1 Rework in the production process......Page 361
10.2.1 Metallurgical and mechanical consequences of rework......Page 362
10.2.3 Lessons to be learned......Page 363
10.3.1 Heat sources......Page 364
10.3.2 Rework stations......Page 366
10.4.2 Desoldering SMDs......Page 367
10.4.3 Filling empty joints......Page 372
10.4.4 Resoldering SMDs......Page 375
10.4.5 Cleaning after rework......Page 377
10.4.6 Semi-mechanized work stations......Page 378
10.5.1 Rework personnel......Page 379
10.6 References......Page 380
Index......Page 382