Plastic Molding Compounds

        

Materials used for encapsulating semiconductor devices are known as plastic molding compounds.  Molding compounds are generally composite materials consisting of epoxy resins, phenolic hardeners, silicas, catalysts, pigments, and mold release agents. 

 

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Critical properties considered when selecting a molding compound include its glass transition temperature, Tg, moisture absorption rate, flexural modulus/strength, coefficient of thermal expansion, thermal conductivity, and adhesion properties.

       

There are many types of molding compounds used in the semiconductor industry today. General-purpose molding compounds with relatively high flexural strengths but exert relatively larger stresses to the device may be used for large and thick packages such as the PDIP and PLCC. Low to ultra-low stress molding compounds are preferred for the encapsulation of thin packages. High-thermal conductivity molding compounds, on the other hand, are required to encapsulate high-power devices. Molding compounds used for surface mount devices may have a low moisture absorption rate, or a high flexural strength at board-mounting temperatures, or a combination of both in order to prevent popcorn cracking.

     

Proper molding compound selection will prevent problems associated with manufacturability, package stress, package cracking, and interfacial delaminations.

    

Table 1. Formulations of Molding Compounds from Sumitomo Bakelite Co., Ltd.

 

EME-6650

EME-6600

EME-6300H

Filler Content

Higher than 6600

Higher than 6300H

Standard

Epoxy Type

Low Vis. ECN

DCPD

ECN

Hardener Type

Standard

Standard

Standard

Catalyst Type

Standard

Standard

Standard

LSA Type

New II

New I

Standard

     

Table 2. Characteristics of Molding Compounds from Sumitomo Bakelite Co., Ltd.

ITEM

Unit

6650R

6600R

6300H

Spiral Flow

cm

110

70

90

Gel Time

sec

30

30

40

Koka's vls.

poise

110

280

300

Alpha1

1/deg  C

1.1

1.2

1.7

Alpha 2

1/deg  C

4.5

4.5

6.6

Tg

deg  C

160

150

165

Flexural Strength(25C)

kgf/mm2

16

17

12

Flexural Strength(240C)

kgf/mm2

2.2

2.0

1.7

Flexural Modulus(25C)

kgf/mm2

1900

2000

1200

Flexural Modulus(240C)

kgf/mm2

120

95

75

Specific Gravity

-

1.95

1.94

1.81

Water Absorption

%

0.22

0.18

0.30

Shore D Hardness

-

86

86

82

Flame Resistance

UL -94

V-0

V-0

V-0

     

Table 3. Properties of ARATRONIC 2184 Variants from Ciba-Geigy

ARATRONIC

 

Spiral Flow

175C/1000PSI

(Inches)

Gel Time

@ 175C

(seconds)

Viscosity

@ 175C

(poises)

2184

Obsolete

30

22

200-300

2184H

Obsolete

24

16

250-350

2184HH

Obsolete

18

12

380-500

2184HHH

Obsolete

16

8

400-500

2184-4 (formerly 2184)

Updated

30

22

200-260

2184-3 (formerly 2184H)

 Updated

25

18

220-300

2184HH

Updated

18

12

300-450

2184HHH

Updated

16

8

350-500

2184-2

New

45

22

80-150

2184-8

New

35

18

120-200

            

See Also:  Semiconductor Materials Encapsulation IC Manufacturing

 

 

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