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.

   

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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 (șC)

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

 

 

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