Index – Advanced Adhesives in Electronics

Index

A

a-terp-epoxide, 143
ABAQUS FEM software, 37
acrylate, 217–18
acrylic, 2
adhesive curing, 222–3
adhesive dispensing, 221–2
adhesive strength, 216–17
adhesives joining technology, 1–11
classification of adhesives used in electronic packaging, 2–6
chemical formulation, 2–3
curing process, 4
functions, 5–6
linear (thermoplastic) and cross-linked (thermosetting) polymer, 3
molecular structure, 3–4
physical form, 2
electronic assemblies overview, 6–10
board level integration of packages, 8
DIP and PGA, 9
electronic packaging hierarchy, 7
SOP, QFP and BGA package, 10
photonics, 214–55
applications, 218
characteristics, 215–17
fabrication of photonic devices, 235–55
photonic devices, 228–35
photonic packaging, 218–28
types used, 217–18
typical uses in electronics, 10–11
direct bonded chip on board, 11
wire bond BGA package cross- sectional view, 11
alignment technique, 221
alumina, 31
aluminium nitride (AlN), 30–1
anisotropic conductive adhesives, 2, 5, 53–104, 66, 176
accelerated testing, 78, 80–4
daisy chain resistance, 81
failure after 560 hours in HAST, 83
failure from damp heat test, 81
single bump resistance, 82
Weibull failure distributions, 82, 84
anisotropic conducting film vs non-conducting film, 97–9
model showing bridge of conducting particles, 98
probability of forming a bridge of conductive particles in flip chip, 98
case studies, 88–99
critical loading, 74–86
bonding, 74–5
contact resistance evolution during bonding process, 74
evaluation methods, 86–8
resistance drift during cyclic humidity test, 87
resistance drift vs square root of time, 86
response and hysteresis of contact resistance to cyclic damp heat conditions, 88
heat seal connector, 88–90
log-normal failure distributions, 90
resistance drift of heat-seal connectors, 89
top view in triple-bond test structure, 89
materials, 64–8, 69, 70
96 single-contact resistance values, 67
anisotropic adhesive contact of die, 67
conducting adhesives physical properties, 68
die with Au-bumps bonded on flexible foil, 69
die with Au-stud bumps bonded on flexible foil, 69
die with NiAu-bumps bonded on flexible foil, 68
foil design for flip chip with 100 µm pitch, 65
footprint of flip chip, 65
four-wire resistance measurement for heat seal connectors, 66
four-wire structure to measure black interconnect resistance, 64
geometrical data of dies used in flip chip on foil assemblies, 70
moisture absorption, 71–3
flexible foils and adhesives moisture absorption and diffusion coefficients, 73
moisture uptake in foil with two different adhesives, 72
water desorption from flexible foil, 73
nature of adhesive bond, 54–64
literature overview, 57–61
in situ measured resistance of daisy-chained adhesive interconnection, 55
soldered and adhesive interconnection, 55
on-line vs off-line monitoring, 84–6
contact resistance drift in accelerated damp-heat test, 84
effect of periodic opening of accelerated humidity chamber, 86
resistance drift during thermal shock test, 85
processing, 68–71, 72
curing conversion of ACF type H-3, 72
curing conversion of ACF type S-1, 71
thinned die cracked during bonding, 71
resistance to reflow soldering, 75–8, 79
ACF-interconnection failed after MSL2-test, 80
ACF-interconnection good after MSL2-test, 79
assembly before MSL-test with thin metal stiffener, 79
daisy chain resistance, 77
moisture sensitivity levels according to JEDEC, 76
normalised resistance, 78
ultra-thin fine pitch ball grid array package, 90–7
ACF-based assembly, 94
with conducting adhesive and solder balls, 91
NCF-based assembly, 94
single-bump resistance, 91, 95
Weibull failure distributions, 92, 93, 96
anisotropic conductive film, 5, 179, 203–4
flip chip and structure of a conductive particle, 204
micro–macro modelling approach, 205
vs non-conducting film, 97–9
ANSYS 8.0, 35
Asymtech, 144

B

ball grid array, 9
Berthelot relation, 168
bisphenol-A diglycidyl ether, 123
bond thermal resistance, 23–6
Bruggeman symmetric and asymmetric models, 18

C

capillary underfill process, 140
carbon nanotubes, 27–30
isotropic conductive adhesives, 125
catalyst, 4
chip scale packaging, 9, 137, 138, 145
coefficient of thermal expansion, 66, 139, 207, 227–8
computational electromagnetics, 200
computational fluid dynamics, 200, 202
computational modelling, 199
computational solid mechanics, 200
conductive adhesives
anisotropic conductive adhesives, 53–104
future trends, 209–11
fast calculations, 211
integration with optimisation tools, 211
life cycle considerations, 211
materials data, 211
modelling through the supply chain, 211
multi-discipline analysis, 210
multi-physics modelling, 209
multi-scale modelling, 211
variation risk mitigation, 211
isotropic conductive adhesives, 105–26
modelling applied to packaging processes, 201–5
ACF flip chip and structure of conductive particle, 204
bonding components using conductive adhesive, 203–5
conductive adhesive materials deposition, 201–3
flow of solder materials in stencil printing, 203
micro–macro modelling approach for bonding ACF particles, 205
modelling techniques to assess conductive properties, 199–212
modelling thermal, electrical and mechanical performance, 205–9
flip chip computer model, 209
flow of solder material in stencil printing, 207
mechanical performance and reliability, 206–9
predicted lifetime of flip chip solder joint, 210
thermal and electrical performance, 205–6
numerical modelling techniques, 200–1
commercial software codes and capabilities, 201
predicting reliable packaging, 202
thermally conductive adhesives, 15–46
Controlled Collapse Chip Connection (C4 technology), 137–8
crosslinks, 31
cure schedule, 215–16
curing process, 4
curing profile, 215–16
curing shrinkage, 226–7
cyclic humidity test, 87

D

damp heat test, 92, 95
data-driven methods, 209
degradation temperature, 217
degree of cure, 178
‘delamination toughness factor, ’, 62
Delco Electronics, 138
diamond fillers, 30
‘die down’ layout, 90
differential scanning calorimetry, 4, 122, 178–9
direct chip attachment technology, 137–9
advantages, 138–9
high performance, 138–9
smaller, thinner, and lighter packages, 138
direct laser writing, 233–5
dispersive (London) interactions, 164
dual cure, 215
dual-in-line packages, 9
Dupre’s equation, 158
dynamic mechanical analyser, 36

E

electrically conductive adhesives (ECA), 105, 191–4
electrically insulating fillers, 30–1
electro-optic coefficient, 216
electroless-Ni/immersion-Au, 117
electronic packaging, 7–8, 209
hierarchy, 7
embossing, 233
encapsulant materials, 150–2
entrapped air bubbles, 225
epoxy, 2, 217
ester epoxy, 143

F

face-centred cubic (FCC), 35
film adhesives, 2
finite element method, 200, 208
finite element modelling, 120
flash method, 41
flip chip
direct chip attachment technology, 137–9
advantages, 138–9
‘no-flow’ pre-applied underfill process, 143–5
no-flow packaging process, 144
process advances and encapsulant materials
capillary underfill process, 140–1
‘Known Good Die’ issue and reworkability, 141–3
localised chip removal and underfill cleanup procedure, 142
reactive thermoplastic vs thermosetting chemistry, 142
reliability challenge, 139
underfill adhesive materials, 137–53
new material challenges to lead-free solder, 143
underfill process and encapsulant materials, 139–43
wafer level dual encapsulation process, 149–52, 153
dual-material wafer process, 150
liquid Type-II encapsulant, 153
wafer level pre-applied underfill process, 145–9
aligning and attaching, 148
depositing underfill onto the wafer, 147
dicing, 147
eutectic solder temperature–time reflow profile, 149
flip chip/CSP packaging process, 146
reflow of the solder and forming the interconnect, 148
reliability of underfill, 149
solidifying the underfill, 147
storage, 147–8
underfill encapsulant curing, 148–9
underfill material requirements, 146
Fourier transform infrared spectroscopy, 4, 122, 178–9
Fourier’s law, 16
Fowkes’s equation, 158, 168, 173
fusion techniques, 209

G

galvanic corrosion, 115–19
gelation, 31
glass transition temperature, 35–7, 217
glassy modulus, 36
guarded hot plate method, 39–40

H

heat seal connector, 88–90
hexagonal close-packed, 35
highly accelerated stress testing, 81
hot-wire technique, 40
hydrogen bonds, 165–8

I

IBM, 137, 139
immersion-Ag, 117
immersion-Sn, 117
integral blend method, 174
integrated chip (IC), 6–7
isotropic conductive adhesives, 2, 5, 66, 105–26, 179
bi-modal filler distribution, 106
contact joints, 107
cured at 150°C
PLCC68, 114
SO20GT, 113
cured at 175°C
PLCC68, 114
S020GT, 113
general properties, 108–11
electrical properties, 109–10
environmental properties, 110–11
mechanical properties, 110
percolation threshold, 108
structure, 108–9
thermal properties, 110
modelling, 121–4
cure modelling, 121–4
electrical modelling, 121
flow modelling, 124
nanotechnologies, 124–5
carbon nanotubes, 125
nanoparticles, 124–5
reliability, 111–21
Ag ICA contact resistance changes at 85/85, 116–17
contact resistances of two different Ag-based ICAs, 118–19
drop-test survival using aluminium blocks, 112
galvanic corrosion, 115–19
impact resistance, 111–15
other reliability problems, 119–21

J

JEDEC-MSLA test, 62
JEDEC standard, 75

L

laser ablation, 235
Lewis acid, 159, 168, 169
Lewis base, 159, 169
linear cure shrinkage, 35
Lorenz constant, 17

M

Manson–Coffin equation, 63
master curve, 36
maximum continuous operating temperature, 217
maximum intermittent temperature, 217
Maxwell–Garnett effective medium model, 18
metal–polymer adhesive interfaces
adhesives, 176–80
adhesive joints fracture modes, 178
degree of conversion and glass transition temperature relationship in ICA, 179
internal stress generated, 176–7
internal stress generation mechanism, 176
shrinkage behaviour during curing and cooling processes, 177
and substrates mechanical behaviour, 178–80
adhesives joints shear and peel strengths temperature dependence, 184–5
schematic illustration, 185
variation with adhesives elastic modulus, 185
chemical and physical intermolecular interactions at interfaces, 162–76
bonding energy for hydrogen bonds vs other chemical and physical bonds, 167
dispersive and polar components, 163–8
general view, 162–3
H(1)–O(2) and O(1)–O(2) bond orders, 166
hydrogen bonds, 165–8
interaction energy between H2O molecules, 166
interfacial free energy analysis, 168–71
polymer films surface free energy, 170
primitive model for ab initio molecular orbital simulation, 165
solubility parameters for analysing intermolecular interactions, 171–2
total electron density contour diagram between H2O molecules, 167
van der Waals bonds, 163–4
van der Waals interactions coefficient of attractive potential, 164
coupling agents, 172–4
interfacial interactions improvement, 172–4
molecular structure, 173
cross-sectional microstructure
anisotropic conductive adhesive, 193
isotropic conductive adhesives, 192
electrical conduction in situ monitoring result
epoxy-based ACF joint, 194
epoxy-based ICA specimen, 192
environmental factors effect, 184–91
epoxy-based ACF specimens
glass transition temperature variation, 189
near-infrared absorption spectrum, 187
variation in weight, 189
interconnections using electrically conductive adhesives, 191–4
model ACF joints 90° peel strength profiles
bonded at 140, 180 and 200 °C for 15s, 184
bonded at 180 °C for 15s, 183
variation covered with Cu foil bonded at 180 °C for 15s, 190
variation with interdigitated Cu pattern bonded at 140 and 180 °C for 15s, 191
moisture absorption effects, 186–91
anisotropic conductive film mechanical properties variation, 188–91
free volume spaces in polymers, 186
general remarks, 186–8
other influential factors determining bond strength of real adhesive joints, 176–84
bonding interface between ACF and polyimide, 182
model joints 90° peel strength, 180
physical factors relationship to bonding strength, 180–4
polyimide-based flex, 182
test speed dependence of, 90° peel strength of model ACF joints, 181
self-assembled monolayers for surface and interfacial modifications, 174–6
formation mechanism on a solid surface, 175
molecular structure, 175
typical self-assembly systems, 174
structural integrity in microelectronics, 157–95
surface free energy variation
Cu foil with surface finishing, 170
polished Ag, Cu and Ni sheets, 171
work of fracture and adhesive joints bonding strength theoretical considerations, 157–62
concept of thermodynamic work of adhesion, 158
dispersive and polar components magnitude of surface free energy, 161
ideal adhesive strength and adhesive joints bonding strength, 160–1
interfacial interaction energy estimated from ab initio simulations, 159–60
interfacial potential and ideal adhesive strength between surfaces, 160
interfacial tension and surface tensions balance on a solid surface, 159
relationship between work of adhesion and adhesive joints work of fracture, 161–2
thermodynamic work of adhesion, 157–9
micro-Brownian motion, 177
microelectronics
metal-polymer adhesive interfaces structural integrity, 157–95
chemical and physical intermolecular interactions at interfaces, 162–76
environmental factors effect, 184–91
interconnections using electrically conductive adhesives, 191–4
other influential factors determining bond strength of real adhesive joints, 176–84
work of fracture theoretical considerations and adhesive joints bonding strength, 157–62
micrometer-sized fillers, 26
microwave curing, 4
model-driven methods, 209
moisture resistance, 217
Mulliken’s method, 165
multi-discipline analysis, 210
multi-physics modelling, 209–10

N

nanometer-sized fillers, 26–30
nanoparticles, 124–5
nanotechnologies, 124–5
National Center for Manufacturing Science (NCMS) criterion, 111
Navier–Stokes equations, 202
‘no-flow’ underfill processes, 139, 143–5
packaging processes, 144
non-conductive adhesives, 66
non-conductive film, 66
vs anisotropic conductive film, 97–9
non-conductive paste, 66
numerical modelling software, 211

O

operating temperature, 217
optic coefficient, 216
organic solderability preservative (OSP), 117

P

passive optical power splitter, 218
pastes, 2
percolation, 18
percolation models, 18–19
percolation threshold, 18, 108
photoacoustic technique, 41
photolithography, 233
photonic devices
adhesives used, 228–35
materials issues, 229–30
curing degree of spin-coated polymeric films
factors affecting curing rate, 238–40
example, 228–9
fully buried or embedded optical waveguide, 229
fabrication, 235–55
curing degree of spin-coated polymeric films, 236–40
interfacial failure in a channel waveguide, 236
interfacial failure of thin polymer film, 236
spin-coated adhesive film surface photography, 239
spin-coated adhesive films measurement locations, 237
spin coating on curing behaviour, 237
interfacial adhesion
different substrates, 251–3
heat treatment, 253–5
spin-coated polymeric adhesive films, 246–51
packaging process, 221–3
adhesive curing, 222–3
adhesive dispensing, 221–2
alignment methods, 221
bonding process of eight-channel fibre array, 222
planar polymeric photonic devices fabrication techniques, 233–5
direct laser writing, 233–5
embossing, 233
laser ablation, 235
photolithography, 233
polymer channel waveguide, 234
processing issues in fabrication, 231–3
curing conditions, 231
mechanical strength, 232
stability, 231–2
surface condition of adherend, 232–3
thin film deposition, 231
spin-coated polymeric adhesive films stability, 240–6
chemical stability, 242–3
cured epoxy after immersion in chromium metal etchant, 244
cured epoxy after immersion in nickel, 243
epoxy adhesive that was not spin coated, 241
influencing factors, 243–6
refractive index, 244
spin coating on thermal stability, 242
thermal stability, 240–2
thermal stability changes, 242
photonic packaging, 218–28
adhesive bonding advantages, 220
example, 218–20
bonded PLC optical splitter, 220
physical properties of materials used in optical splitter, 220
unpacked and packed PLC optical splitter, 219
failure issues, 223–8
coefficient of thermal expansion mismatch, 227–8
contamination-induced delamination, 223
curing shrinkage, 226–7
delaminated fibre in a V-groove, 227
entrapped air bubbles, 224, 225
misalignment, 224–6
packaged fibre in V-groove, 225
surface contamination, 223–4
uneven curing of adhesive, 226
packaging process of photonic devices, 221–3
adhesive curing, 222–3
adhesive dispensing, 221–2
alignment methods, 221
bonding process of eight-channel fibre array, 222
photonics
adhesive characteristics, 215–17
adhesive strength, 216–17
curing profile, 215–16
moisture resistance, 217
operating temperature, 217
optic coefficient, 216
refractive index, 216
transparency, 216
viscosity, 215
adhesive technology, 214–55
applications, 218
challenges for photonic devices fabrication, 235–55
photonic devices, 228–35
photonic packaging, 218–28
types used, 217–18
heat treatment on interfacial adhesion, 253–5
damp heat, 254–5
interfacial adhesion of spin-coated polymeric adhesive films, 246–51
after heat exposure, 247
average shear strength with and without plasma treatment, 250
different adhesion strength at different location, 246–7
free-body diagram of bi-material structure, 248
plasma-treated substrates, 248–51
shear strength with and without heat exposure, 247
silicon substrate surface roughness, 249
untreated and plasma-treated substrate surface, 249
interfacial adhesion on different substrates, 251–3
chromium surface, 253
different surface structure and processing, 251
silica surface, 253
silicon surface, 253
substrate surface, 252
processing issues in device fabrication, 231–3
pigtailing, 218
pin grid arrays, 9
planar lightwave circuits, 218–19
plasma surface treatments, 115
plasticisation, 187–8
Poisson distribution, 97
polyimide, 3
polymer adhesive technology, 1
polymeric adhesives, 214
polyurethane, 3
‘pre-applied’ underfill processes, 139
printed circuit board, 8
process modelling
conductive adhesive properties assessment, 199–212
future trends, 209–11
numerical modelling techniques, 200–1
packaging processes, 201–5
thermal, electrical and mechanical performance, 205–9

Q

quad flat package (QFP), 9

R

reduced time scale, 36
refractive index, 216
‘room temperature sintering’ process, 125
self-alignment, 108
self-assembled monolayers, 120, 174–6
silicon, 6
silver, 26, 106
silver-epoxy, 31
small outline package (SOP), 9
spin-coated adhesive films
measurement locations, 237
surface photography, 239
steady state accelerated humidity test, 87
stencil printing, 201–2
storage modulus, 66
surface active bonding process, 171
surface contact metallisation, 119–20
surface mount technology, 151
System-in-Package, 6
System-on-Chip, 6

T

‘thermal contact resistance, ’, 16
thermal cycling test, 56, 62
thermal resistance, 19–20
thermal shock test, 92, 95
thermal stability, 240–2
thermally conductive adhesives, 15–46
bond thermal resistance, 23–6
participation in total thermal resistance, 25
temperature gradient on whole joint and on individual layers, 24
2D model with spherical silver particles, 34
heat conductance model, 16–18
heat transfer through a layer, 17
heat transport, 18–26
conductive paths between joining surface, 19
models, 18–19
polymer base materials, 31–8
contact pressure between filler particles, 38
estimated parameters for WLF equation, 37
influence of shrinkage on contact between filler particles, 34
influence on contact pressure between filler particles, 37–8
resistance changes of electrically-conductive adhesives, 33
role of cure shrinkage, 32–5
types, 31–2
viscoelasticity, 35–7
volume shrinkage of epoxy resin vs curing time, 32
thermal conductivity and its measurement methods, 38–44
measuring set-up based on guarded hot plate method, 40
steady-state methods, 39–40
thermal conductivity, 42
thermal conductivity of adhesives, 41–4
transient methods, 40–1
thermal resistance of adhesives, 19–23
cylindrical filler particles, 21
normalised thermal conductivity of adhesive vs filler volume content, 20
thermal constriction resistance, 22
thermally conductive fillers, 26–31
adhesive containing silver flakes and bundles of carbon nanotubes, 28
diamond fillers, 30
electrically insulating fillers, 30–1
micro-size silver particles, 27
micrometer-sized fillers, 26
nanometer-sized fillers, 26–30
thermally conductive fillers, 26–31
thermo-optic coefficient, 216
thermogravimetric analysis, 240–1
thermomechanical analysis, 4
thermoplastics, 3, 31
thermosets, 31
thermosetting, 4
three-layer foils, 64
tin–lead (Sn-Pb) eutectic solder, 143
transient dipoles, 164
transparency, 216
two-layer foils, 64
type-I encapsulant, 150–2
type-II encapsulant, 150–2

U

ultra-thin fine pitch ball grid array package, 90–7
underfill adhesive materials
flip chip applications, 137–53
direct chip attachment technology advantages, 138–9
flip chip and direct chip attachment technology, 137–8
flip chip technology reliability challenge, 139
flip chip underfill process and encapsulant materials, 139–43
new material challenges to lead-free solder, 143
‘no-flow’ pre-applied underfill process, 143–5
wafer level dual encapsulation process, 149–52, 153
wafer level pre-applied underfill process, 145–9
unit cell, 34–5

V

van der Waals bonds, 163–4
Variable Frequency Microwaves, 4
virtual prototyping, 199
viscosity, 215
vitrification, 31

W

3ω method, 41
wafer level dual encapsulation process, 149–52, 153
wafer level pre-applied underfill process, 139, 145–9
Weibull distributions, 92
Wiedemann–Franz’s law, 17
Williams–Landel–Ferry equation, 36

Y

Young’s equation, 158