Reflow soldering processes : SMT, BGA, CSP and flip chip technologies

Preface......Page 11
1.1.2 Surface mount components......Page 12
1.1.3 Types of surface mount assembly technology......Page 15
1.1.4 Surface mount soldering process......Page 16
1.1.5 Advantages of solder paste technology in SMT......Page 17
1.2.1 Technology driving force......Page 19
1.2.2 Area array packages......Page 22
1.3 Conclusion......Page 28
2.1.1 Spreading......Page 30
2.1.2 Fluid flow......Page 31
2.1.3 Dissolution of base metal......Page 32
2.1.4 Intermetallics......Page 33
2.2 Effect of elemental constituents on wetting......Page 36
2.3 Phase diagram and soldering......Page 37
2.4.1 Deformation mechanisms......Page 39
2.4.3 Effect of impurities on soldering......Page 41
2.5 Conclusion......Page 44
Appendix 2.1 Effect of flux surface tension on the spread of molten solder......Page 45
3.1 Fluxing reactions......Page 47
3.1.2 Oxidation– reduction reactions......Page 0
3.2.1 Resins......Page 49
3.2.2 Activators......Page 50
3.2.4 Rheological additives......Page 52
3.3.1 Atomization......Page 53
3.3.2 Particle size and shape......Page 54
3.4 Solder paste composition and manufacturing......Page 55
3.5.1 Rheology basics......Page 59
3.5.2 Solder paste viscosity measurement......Page 60
3.6 Solder paste rheology requirement......Page 61
3.6.1 Effect of composition on rheology......Page 63
3.7 Conclusion......Page 64
4.1.2 Paste deposition......Page 66
4.2 Printer level consideration......Page 70
4.2.1 Stencil......Page 72
4.2.2 Squeegee......Page 79
4.2.3 Printing and inspection process......Page 82
4.3 Pick-and-place......Page 84
4.4 Reflow......Page 86
4.4.2 Vapor phase reflow......Page 88
4.4.4 In-line-conduction reflow......Page 89
4.4.6 Laser reflow......Page 90
4.6.2 Reflow-alloying......Page 91
4.7 Solder joint inspection......Page 93
4.8 Cleaning......Page 94
4.10 Principle of troubleshooting reflow soldering......Page 96
4.11 Conclusion......Page 97
5.3 Paste hardening......Page 99
5.4 Poor stencil life......Page 100
5.5 Poor paste release from squeegee......Page 101
5.6 Poor print thickness......Page 103
5.7 Smear......Page 105
5.8 Insufficiency......Page 107
5.9 Needle clogging......Page 108
5.10 Slump......Page 109
5.11 Low tack......Page 111
5.12 Short tack time......Page 112
5.13 Conclusion......Page 113
6.2 Nonwetting......Page 114
6.3 Dewetting......Page 116
6.4 Leaching......Page 117
6.5 Intermetallics......Page 118
6.5.1 General......Page 119
6.5.2 Gold......Page 121
6.6 Tombstoning......Page 124
6.7 Skewing......Page 128
6.8 Wicking......Page 129
6.9 Bridging......Page 131
6.10 Voiding......Page 134
6.11.2 Other openings......Page 138
6.11.4 Projected solder......Page 139
6.12 Solder balling......Page 140
6.13 Solder beading......Page 142
6.14 Spattering......Page 146
6.15 Conclusion......Page 148
7.1 White residue......Page 150
7.3.1 Flux residue content......Page 152
7.3.4 Residue hardness......Page 153
7.3.7 Soft-residue versus low-residue......Page 154
7.3.9 Multiple cycles probing testability......Page 155
7.4.2 Electrochemical migration (EM)......Page 156
7.4.3 Effect of flux chemistry on IR values......Page 157
7.4.4 Effect of soldering temperature......Page 161
7.4.7 Effect of interaction between flux and solder mask......Page 162
7.5.2 Delamination......Page 163
7.6 Conclusion......Page 164
8.1.2 Alloys used in BGA and CSP solder bumping and soldering......Page 165
8.2 Solder bumping and challenges......Page 166
8.2.1 Build-up process......Page 167
8.2.2 Liquid solder transfer process......Page 168
8.2.3 Solid solder transfer processes......Page 170
8.2.4 Solder paste bumping......Page 186
8.3 Conclusion......Page 192
9.1.1 General stencil design guideline......Page 194
9.1.2 BGA/CSP placement......Page 196
9.1.4 Inspection......Page 197
9.2.1 Process flow......Page 198
9.2.5 Site preparation......Page 199
9.3.1 Starved solder joint......Page 200
9.3.2 Poor self-alignment......Page 202
9.3.3 Poor wetting......Page 203
9.3.4 Voiding......Page 205
9.3.5 Bridging......Page 211
9.3.6 Open......Page 213
9.3.8 Solder webbing......Page 215
9.4 Conclusion......Page 216
10.1.1 Conventional flip chip attachment......Page 219
10.1.3 Epoxy flux......Page 224
10.1.5 SMT......Page 225
10.1.6 Fluxless soldering......Page 226
(WLCFU)......Page 227
10.2.1 Misalignment......Page 228
10.2.2 Poor wetting......Page 229
10.2.3 Solder voiding......Page 230
10.2.4 Underfill voiding......Page 232
10.2.6 Open......Page 235
10.2.7 Underfill crack......Page 236
10.2.8 Delamination......Page 238
10.2.9 Filler segregation......Page 239
10.3 Conclusion......Page 241
11.1.1 Time/temperature requirement for the fluxing reaction......Page 242
11.3.4 Deformation of joints......Page 243
11.4.2 Solder beading......Page 244
11.5.2 Soaking zone......Page 245
11.6.2 Engineering the optimized profile......Page 246
11.7.2 Background of conventional profiles......Page 248
11.8 Discussion......Page 249
11.8.5 Nitrogen reflow atmosphere......Page 250
11.8.7 Adjustment of optimal profile......Page 251
11.9 Implementing linear ramp-up profile......Page 252
11.10 Conclusion......Page 253
12.1 Initial activities......Page 254
12.3 Impact of Japanese activities......Page 255
12.7.3 Sn/Ag/Cu......Page 256
12.9 PCB finishes......Page 257
12.14 Opinions of consortia......Page 258
12.18 Summary of lead-free adoption......Page 259
12.19.2 Fillet lifting......Page 260
12.19.3 Conductive anode filament......Page 262
12.19.4 Grainy surface......Page 263
12.20 Conclusion......Page 264
Index......Page 266