Plastic Molding Compounds for Semiconductor Packaging

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.

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

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