Die Attach
Adhesives and Materials
Die attach materials
or adhesives do more than attach the die to the
die pad, substrate, or cavity. They also provide thermal and/or
electrical conductivity between the die and the package, essentially
affecting the performance of the device while operating in the field. As
such, proper selection of the most suitable die attach material for a
semiconductor product and application is very important.
Polymer Adhesives
Polymer adhesives, which are organic adhesives that
consist of long chains of thermosetting polymers, are widely used as die
attach material. Most polymer adhesives used in semiconductor
assembly also contain a large percentage of silver fillers for
electrical conductivity.
Polymer adhesives initially contain solvents that allow
easy dispensation, and are cured by exposure to high temperature in the
presence of catalysts. Curing basically consists of two steps: 1)
outgassing of the solvents and 2) polymerization of the paste into
a cross-linked thermoset material.
'Thermosetting' refers to the characteristic of a
material to remain solid once cured even if subjected further to high
temperatures. On the other hand, 'thermoplastic' materials have the
ability to reflow at a high enough temperature, even if curing has
previously occurred.
Polymer adhesives also come in several forms, two of
which are epoxy and polyimides.
Polymides
are high temperature cure, highly rigid polymer adhesives that is
formed from polyamic acid through condensation polymerization.
Polyimides contain a large percentage of solvent and generally need at
least two steps of curing at different temperatures for effective
cross-linking.
Epoxies
are low
temperature cure, high strength polymer adhesives that allow a one-step,
quick cure. One drawback of epoxies though is its relatively
higher ionic content. Polyimides, on the other hand, apply more
stress to the die than epoxies.
Eutectic Die Attach
Material
Eutectic die attach, which is commonly employed in hermetic
packages, uses a eutectic alloy to attach the die to the cavity. A
eutectic alloy is an alloy with the lowest melting point possible for the metals
combined in the alloy. The Au-Si eutectic alloy is the most commonly used
die attach alloy in semiconductor packaging.
|
|
Table
1. Properties of Some Die Attach Alloys from
Semiconductor Packaging Materials
(SPM)
|
Alloy |
Melting Temp.(oC) |
Application |
Advantages/Disadvantages |
|
80Au-20Sn |
280 |
Die
attachment; Chip packaging. |
High thermal conductivity and
creep resistance/
expensive. |
|
88Au-12Ge |
356 |
Die
attachment; Chip packaging. |
High thermal conductivity and
creep resistance/
expensive. |
|
97Au-3Si |
370 |
Die
attachment; Chip packaging. |
High thermal conductivity and
creep resistance/
expensive. |
|
97.5Pb-1Sn-1.5Ag |
309 |
Die
attachment; Chip packaging. |
It is a eutectic alloy having
fast heat response/
contains Pb. |
|
63Sn-37Pb |
183 |
Die
attachment; Chip and board packaging. |
The most widely used in PCB
packaging having fast heat response and high wetting power;
reliability well established/ contains Pb. |
|
62Sn-36Pb-2Ag |
179 |
Die
attachment; Chip and board packaging. |
Widely used in PCB packaging
having fast heat response and high wetting power and compatible
with Ag metallization/ contains Pb. |
|
97.3Bi-2.5Ag-0.2Cu |
260 |
Die
attachment. |
High temperature packaging
ability and low cost/ no
reliability study. |
|
96.5Sn-3.5Ag |
221 |
Die
attachment; Chip and board packaging. |
Widely targeted as a PCB
packaging solder and reliability well established / melting temperature
still relatively high. |
|
99.3Sn-0.7Cu |
227 |
Die
attachment; Chip and board packaging. |
Widely targeted as a PCB wave
soldering solder and reliability well established / melting temperature
still relatively high. |
|
94.7Sn-3.3Ag-2Cu |
217 |
Die
attachment; Chip and board packaging. |
The most widely targeted as a
PCB packaging solder and very stable eutectic point/
melting temperature
still relatively high. |
|
58Bi-42Sn |
138 |
Temperature sensitive device packaging. |
Targeted as low cost PCB
packaging solder and reliability well established / plasticity
still relatively low. |
|
52In-48Sn |
118 |
Temperature sensitive device packaging. |
Will absorb package thermal
strain due to its low strength and high ductility/ expensive. |
Table
2. Properties of Some Die Attach Alloys from Loctite
|
Product |
Application |
Resin/
Filler |
Viscosity
5
rpm/
25C (cps) |
Thixo.
Index
.5/5
rpm |
Thermal
Cond'vity
(W/m
K) |
Mod
of Elasticity
(GPa)
|
Oven
Cure (15 min @)
|
|
QMI506 |
BGA,
CSP |
BMI/Silver |
8500 |
4.9 |
1.1 |
0.35 |
150C |
|
QMI516 |
BGA,
CSP |
BMI/Silver |
8000 |
3.0 |
3.0 |
0.8 |
150C |
|
QMI526 |
BGA,
CSP, Cavity-down BGA |
BMI/Silver |
9000 |
5.8 |
2.5 |
2.5 |
150C |
|
QMI527 |
BGA,
CSP |
BMI/Silver |
6800 |
5.5 |
2.6 |
2.6 |
150C |
|
QMI536 |
Stacked
CSP |
BMI/Teflon |
9000 |
5.5 |
0.2 |
0.2 |
150C |
|
QMI536HT |
Lid
Attach, PBGA |
BMI/B-N |
13000 |
5.5 |
0.76 |
0.76 |
150C |
|
QMI546 |
Stacked
CSP |
BMI/Teflon |
7500 |
5.5 |
0.28 |
0.28 |
150C |
|
QMI547 |
Stacked
CSP |
BMI/Teflon |
6500 |
5.5 |
0.8 |
0.8 |
150C |
|
QMI505MT |
Leadframes |
BMI/Silver |
12000 |
4.3 |
2.4 |
0.92 |
150C |
|
QMI518 |
Cavity-down
BGA
|
BMI/Silver
|
8500
|
4.7
|
1.4
|
300
|
180C
|
|
QMI519 |
Pre-plated
Leadframes
|
BMI/Silver
|
9000
|
4.2
|
2.61
|
850
|
180C
|
|
QMI534 |
Various
Substrates
|
BMI/Teflon
|
9000
|
5
|
0.4
|
850
|
150C
|
|
KO111
|
Conventional
|
Epoxy/Silver
|
7500
|
4.9
|
3.7
|
850
|
10m@165C
|
|
KO125
|
Conventional
|
Epoxy/Silver
|
52000
|
5.8
|
2.1
|
_
|
10m@165C
|
Table
3. Properties of Some Die Attach Adhesives from
Ablestik
|
|
Adhesive Type
|
Conductivity
|
Cure Time (min)
|
Modulus (MPa)
|
Tg (ºC)
|
Viscosity (cps)
|
Work Life (hrs)
|
|
ABLEBOND 16-1LV
|
Paste
|
Electrically conductive
|
30
|
N/A
|
N/A
|
N/A
|
2
|
|
ABLEBOND 2000B
|
Paste
|
Electrically conductive
|
45
|
2800
|
N/A
|
8700
|
24
|
|
ABLEBOND 2025
|
Paste
|
Electrically insulating
|
15
|
720
|
N/A
|
10500
|
24
|
|
ABLEBOND 3003
|
Paste
|
Thermally conductive
|
150
|
4000
|
49
|
30000
|
10
|
|
ABLEBOND 3230
|
Paste
|
Electrically conductive
|
15
|
2900
|
37
|
9000
|
24
|
|
ABLEBOND 826-1DS
|
Paste
|
Electrically conductive
|
30
|
5300
|
67
|
19000
|
24
|
|
ABLEBOND 8322A
|
Paste
|
Electrically conductive
|
1
|
1630
|
30
|
9000
|
24
|
|
ABLEBOND 8340A
|
Paste
|
Electrically conductive
|
15
|
910
|
25
|
9400
|
24
|
|
ABLEBOND 8360
|
Paste
|
Electrically conductive
|
60
|
4980
|
88
|
8000
|
20
|
|
ABLEBOND 8361HE
|
Paste
|
Electrically conductive
|
30
|
N/A
|
N/A
|
8500
|
24
|
|
ABLEBOND 8361J
|
Paste
|
Electrically conductive
|
90
|
2870
|
40
|
9400
|
24
|
|
ABLEBOND 8385
|
Paste
|
Electrically conductive
|
5
|
200000
|
14
|
9500
|
6
|
|
ABLEBOND 8390A
|
Paste
|
Electrically conductive
|
1
|
2300
|
53
|
9600
|
24
|
|
ABLEBOND 8390C
|
Paste
|
Electrically conductive
|
4
|
1800
|
19
|
9500
|
16
|
|
ABLEBOND 84-3J
|
Paste
|
Electrically insulating
|
60
|
6100
|
87
|
20000
|
336
|
|
ABLEBOND 84-3MVB
|
Paste
|
Non-conductive
|
120
|
6200
|
80
|
31000
|
48
|
|
ABLEBOND 8509
|
Paste
|
Electrically conductive
|
45
|
3800
|
40
|
8700
|
24
|
|
ABLEBOND 8510AA
|
Paste
|
Electrically conductive
|
15
|
2760
|
38
|
8800
|
N/A
|
|
ABLEBOND 8515
|
Paste
|
Non-conductive
|
15
|
1300
|
39
|
11500
|
24
|
|
ABLEBOND MA-2
|
Paste
|
Electrically conductive
|
30
|
N/A
|
108
|
N/A
|
24
|
|
ABLEBOND MC723
|
Paste
|
Electrically insulating
|
15
|
7000
|
75
|
55000
|
16
|
|
ABLEBOND OA-1S
|
Paste
|
Non-conductive
|
135
|
1100
|
60
|
325
|
10
|
|
ABLEFILL JM8806
|
Paste
|
Electrically insulating
|
90
|
8000
|
144
|
6000
|
24
|
|
ABLEFILL UF8802B
|
Paste
|
Electrically insulating
|
90
|
10000
|
142
|
7500
|
24
|
|
ABLEFILL UF8807
|
Paste
|
Electrically insulating
|
30
|
10000
|
147
|
17000
|
8
|
|
ABLETHERM 2600BT
|
Paste
|
Electrically conductive
|
15
|
4300
|
41
|
9300
|
24
|
|
UF8806LP
|
Paste
|
Non-conductive
|
90
|
1
|
144
|
6500
|
24
|
|
ABLEBOND 2025D
|
Paste
|
Electrically insulating
|
15
|
640
|
42
|
12200
|
24
|
|
ABLEBOND 2100A
|
Paste
|
Electrically conductive
|
15
|
1500
|
60
|
9000
|
24
|
|
ABLEBOND 2200
|
Paste
|
Electrically conductive
|
30
|
166
|
-15
|
9000
|
24
|
|
ABLEBOND 3902
|
Paste
|
Electrically conductive
|
60
|
2800
|
N/A
|
20000
|
2
|
|
ABLEBOND 71-1
|
Paste
|
Electrically conductive
|
60
|
3400
|
240
|
14000
|
N/A
|
|
ABLEBOND 789-3
|
Paste
|
Non-Conductive
|
30
|
N/A
|
126
|
N/A
|
N/A
|
|
ABLEBOND 8207
|
Paste
|
Electrically conductive
|
60
|
4800
|
63
|
11000
|
24
|
|
ABLEBOND 8340
|
Paste
|
Electrically conductive
|
30
|
710
|
25
|
9000
|
24
|
|
ABLEBOND 8390
|
Paste
|
Electrically conductive
|
2
|
4650
|
73
|
8800
|
48
|
|
ABLEBOND 84-1LMISR4
|
Paste
|
Electrically conductive
|
60
|
3940
|
120
|
8000
|
18
|
|
ABLEBOND 84-3MV
|
Paste
|
Non-Conductive
|
60
|
N/A
|
N/A
|
29000
|
N/A
|
|
ABLEBOND 868-7
|
Paste
|
Non-Conductive
|
15
|
N/A
|
N/A
|
N/A
|
1
|
|
ABLEBOND 8806
|
Paste
|
Non-Conductive
|
10
|
N/A
|
240
|
60000
|
N/A
|
|
ABLEBOND 965-1L
|
Paste
|
Electrically conductive
|
60
|
4800
|
85
|
12000
|
24
|
|
ABLEBOND 967-3
|
Paste
|
Thermally conductive
|
5
|
N/A
|
85
|
7000
|
48
|
|
ABLEBOND 979-1A
|
Paste
|
Electrically conductive
|
1
|
3800
|
193
|
15000
|
24
|
|
ABLEBOND 9902
|
Paste
|
Thermally conductive
|
240
|
N/A
|
N/A
|
20000
|
3
|
|
ABLEBOND BF-2
|
Paste
|
Non-conductive
|
60
|
3800
|
98
|
25000
|
48
|
|
ABLEBOND BF-4
|
Paste
|
Non-conductive
|
30
|
N/A
|
94
|
22500
|
24
|
|
ABLEBOND JM1032A
|
Paste
|
Electrically conductive
|
5
|
1000
|
73
|
6500
|
24
|
|
ABLEBOND JM2500
|
Paste
|
Electrically conductive
|
120
|
400
|
60
|
4500
|
12
|
|
ABLEBOND JM7000LV
|
Paste
|
Electrically conductive
|
30
|
10000
|
240
|
5000
|
8
|
|
ABLEBOND JM7000NC
|
Paste
|
Non-conductive
|
N/A
|
10500
|
220
|
8000
|
8
|
|
ABLEBOND JM7800
|
Paste
|
Electrically conductive
|
30
|
5000
|
184
|
11000
|
8
|
|
ABLEBOND LS-1
|
Paste
|
Non-conductive
|
30
|
2900
|
90
|
54500
|
24
|
|
ABLEBOND MA-1
|
Paste
|
Electrically conductive
|
30
|
700000
|
78
|
15000
|
24
|
|
ABLEFILL JM8801
|
Paste
|
Electrically insulating
|
90
|
10000
|
146
|
6000
|
24
|
|
ABLELUX LS-2
|
Paste
|
Non-conductive
|
60
|
2600
|
50
|
30000
|
24
|
|
ABLETHERM 2600K
|
Paste
|
Thermally conductive
|
45
|
3670
|
68
|
8100
|
24
|
|
ABLETHERM 3185
|
Paste
|
Electrically conductive
|
150
|
285
|
39
|
44000
|
16
|
|
See Also:
Semiconductor
Materials; Die Attach Process;
Semiconductor
Manufacturing
|
Books recommended for you: |
|
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