JPH09176294A - Liquid sealing material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a liquid sealing material which can greatly improve the reliability of semiconductors in accelerated tests such as a pressure cracker test and a thermal shock test by using a specific composition. SOLUTION: This liquid sealing material is composed of, as major components, (A) a liquid epoxy resin, (B) an alkylated diamino diphenyl methane which is a liquid aromatic amine hardener at room temp., (C) a polybutadiene compound having an epoxy group(s), (D) a silane coupling agent having not less than one functional group selected from among epoxy, amino and mercapto groups and an inorganic filler of which average particle size is 3-10μm and in which particles with their sizes of not more than 1μm account for 6-45wt.% and particles with their sizes of not less than 30μm account for not more than 25wt.% respectively of the total inorganic filler component, and the blending weight ratio of each component is given in the formula. ratios.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid sealing material used for sealing a semiconductor.

[0002]

2. Description of the Related Art A liquid sealing material is used for plastic pin grid array (hereinafter referred to as PPGA) type semiconductor encapsulation, but it is not sufficient in reliability as compared with a hermetically sealed type using ceramics. The spread of plastic packages has been delayed compared to the dual in-line (hereinafter referred to as DIP) type. The cause of the decrease in reliability of the PPGA type semiconductor is that [moisture enters from the packaged organic printed wiring board. Unlike the transfer molding of the DIP type package, the liquid encapsulating material flows into the package without pressure and is molded, so that air bubbles remain in the resin and cracks occur when heat stress is applied. Since the resin, the semiconductor chip, and the organic substrate have different linear expansion coefficients, when heat stress is applied, peeling occurs at the interface, which facilitates moisture infiltration. And the like.

[0003]

DISCLOSURE OF THE INVENTION The present invention is a liquid that can greatly improve the reliability of semiconductors in accelerated tests such as a pressure cooker test (hereinafter referred to as PCT) and a thermal cycle test (hereinafter referred to as T / C). The present invention provides a sealing material.

[0004]

Therefore, as a result of intensive studies for solving the above problems, the present invention has revealed that liquid epoxy resins and aromatic amine curing agents that are liquid at room temperature are alkylated. A composition obtained by blending diaminodiphenylmethane, an epoxy group-containing polybutadiene compound, and a silane coupling agent with an inorganic filler having a specific particle size distribution was subjected to a pressure cooker test (hereinafter, referred to as PC
The present invention has been completed by finding that it can be used as a sealing material that can greatly improve the reliability of semiconductors in accelerated tests such as T) and thermal cycle tests (hereinafter referred to as T / C). . That is, the present invention includes (a) a liquid epoxy resin, (b) an aromatic amine curing agent alkylated diaminodiphenylmethane that is liquid at room temperature, (c) a polybutadiene compound having an epoxy group, (d) an epoxy group, an amino group, A silane coupling agent having one or more functional groups selected from the group of mercapto groups in the molecule, and (e) a liquid sealing material containing an inorganic filler having a specific particle size distribution as a main component The mixing ratio is (c) / {(a) + (b) + (c)} = 0.03 to 0.
10, (d) / {(a) + (b) + (c)} = 0.02
˜0.10, and (e) / {(a) + (b) + (c)
+ (D) + (e)} = 0.50 to 0.80,
The inorganic filler (e) has an average particle size of 3 to 10 μm,
An inorganic filler having a particle size of 1 μm or less in an amount of 6 to 45% by weight in the total inorganic filler component and an inorganic filler having a particle size of 30 μm or more in an amount of 25% by weight or less in the total inorganic filler component was blended. Since it is a liquid encapsulating material, the reliability of a PPGA type semiconductor using an organic printed wiring board can be significantly improved.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The liquid epoxy resin (a) used in the present invention contains 50% by weight or more of its components at 25 ° C.
It is preferable that the viscosity at 10 is 10 Pa · s or less. If 50% by weight or more of the epoxy resin component is not a low-viscosity liquid epoxy, the viscosity of the composition will be high, and when encapsulating the PPGA package with a liquid encapsulation material, air bubbles will be trapped or corner corners will be filled. It is not preferable because defects easily occur and reliability is lowered. As a method for measuring the viscosity of an epoxy resin, in the case of a liquid material at room temperature,
It is measured with an E-type viscometer manufactured by Toki Sangyo Co., Ltd. at 25 ° C. There is no particular limitation as long as it is an epoxy resin that satisfies this requirement, but specific examples thereof include bisphenol A diglycidyl ether type epoxy resin, bisphenol F diglycidyl ether type epoxy resin, bisphenol S diglycidyl ether type epoxy resin. Resin, 3,
3 ', 5,5'-tetramethyl-4,4'-dihydroxybiphenyl diglycidyl ether type epoxy resin,
4,4'-dihydroxybiphenyl diglycidyl ether type epoxy resin, 1,6-dihydroxybiphenyl diglycidyl ether type epoxy resin, phenol novolac type epoxy resin, bromine type cresol novolac type epoxy resin, bisphenol D diglycidyl ether type epoxy resin, etc. There is. These may be used alone or in combination. Further, in order to obtain a highly reliable liquid encapsulating material, it is preferable that the epoxy resin that can withstand use has as little ionic impurities as Na ⁺ and Cl ⁻ as much as possible.

The aromatic amine curing agent (b) used in the present invention is alkylated diaminodiphenylmethane, which is a liquid at room temperature. Amines having no aromatic ring are poor in heat resistance and have a fatal drawback of poor storage stability because they are highly reactive even in an atmosphere of zero degree or less, and are not suitable for the present invention. In addition, in order to obtain a highly reliable liquid encapsulating material, amine-based curing agents that can be used are Na ⁺ and Cl ^−.
It is preferable that the amount of ionic impurities, such as The aromatic amine type curing agent of (b) can provide a material having very good fluidity by combination with the liquid epoxy resin of (a). Even when flowing into the package under no pressure and curing, no air bubbles remain, and problems with fluidity such as voids and unfilling hardly occur. The compounding molar ratio {(a) / (b)} of the epoxy resin of (a) which is the main agent and the aromatic amine curing agent alkylated diaminodiphenylmethane of (b) which is the curing agent is 0.9 to 1. 2 is desirable.
When the amount of the curing agent is less than 0.9 and the curing agent is excessive, unreacted amino groups remain excessively, which leads to a decrease in moisture resistance and a decrease in reliability. On the other hand, if it exceeds 1.2, that is, if the amount of epoxy resin increases, the curing becomes insufficient, leading to a decrease in reliability.

Examples of the elastomer used in the present invention include polybutadiene compounds having an epoxy group (c), which have good compatibility with the epoxy resin (a) and are expected to have low stress and toughness. Elastomers generally lack compatibility with epoxy resins, and therefore have the property of being reduced in moldability due to bleeding after injection curing. However, by incorporating an epoxy group into a part of the molecule, the compatibility increases, and the epoxy compound partially reacts with the curing agent (b) to crosslink,
It is considered that the bleeding property is improved and the low stress and toughness peculiar to polybutadiene having an epoxy group can be exhibited. The polybutadiene compound having an epoxy group preferably has a number average molecular weight of 1,000 to 2,000. If it is less than 1000, bleeding tends to occur, and if it exceeds 2000, the viscosity becomes high, and both are not preferred. Further, the epoxy content (main chain addition mole fraction%) is preferably 3 to 10%.
If it is less than 3%, the compatibility is poor, and if it exceeds 10%, it crosslinks with the curing agent, so that a so-called sea-island structure cannot be obtained, so that a reduction in stress cannot be expected. For example, a 3-point bending test can be used to confirm the reduction of stress, and a KIC measurement can be used to confirm the toughness. Excellent results can be obtained by any of the test results. The polybutadiene compound having an epoxy group can maximize its low stress property and toughness by adjusting the addition amount thereof. The addition amount is (c)
/{(A)+(b)+(c)}=0.03-0.10 is desirable, but if it is less than 0.03, the effects of low stress and toughness cannot be expected, and especially T / C (temperature This may cause surface cracks during the cycle test) and lead to poor reliability. On the other hand, if it exceeds 0.10, the compatibility with the epoxy resin (a) deteriorates, which causes a drop in moldability such as oil floating on the package surface and bleeding. Further, with a random copolymer silicone-modified epoxy resin, a random copolymer silicone-modified phenol resin, or an epoxy group-containing polyolefin, which has a lower stress effect and is compatible with the epoxy group-containing polybutadiene compound of (c). May be combined.

Examples of the silane coupling agent (d) having one or more functional groups selected from the group consisting of epoxy group, amino group and mercapto group in the molecule include epoxy silanes (for example, manufactured by Shin-Etsu Chemical Co., Ltd.). KBM-403) is preferred. Further, if it is desired to enhance the adhesion to the substrate depending on the application, aminosilane and mercaptosilane may be added in part or in whole with respect to the total amount of the coupling agent, if necessary.

As the inorganic filler (e) (hereinafter, simply referred to as a filler), crystalline silica, fused silica or the like is used. The shape generally has a spherical shape, a crushed shape, a flake shape, and the like, but the linear expansion coefficient can be reduced by adding more filler, and a spherical inorganic filler is best for improving the effect. The addition amount is (e) / {(a) +
(B) + (c) + (d) + (e)} = 0.50 to 0.8
0 is desirable. If it is less than 0.50, the above-mentioned effect of reducing the linear expansion coefficient is small, and if it exceeds 0.80, the viscosity of the resulting liquid sealing material becomes too high, which is not a practical level, which is not preferable. Further, by adjusting the particle size distribution of the filler, it is possible to maximize flow characteristics such as viscosity. It is generally known that a filler having a wide particle size distribution and a filler having a large particle size tend to have a lower viscosity. However, a filler having only a large particle size of, for example, 50 μm or more for the purpose of lowering the viscosity certainly lowers the viscosity, but the filler having a relatively high specific gravity sinks during curing, and the composition is above and below the cured product. So-called filler sedimentation occurs with different proportions. Another drawback of using a filler having a large particle size is that it does not flow into a narrow gap. As typified by a PPGA type package, there is a tendency toward a package with a large number of pins and space saving, and as an example, the pitch between wires has become narrower recently. The particle size of the filler must be reduced in order to allow the liquid encapsulating material to flow in under such a tendency without any pressure and to prevent the fluidity problems such as voids and unfilling from occurring. However, reducing the particle size also increases the problem that the fluidity is impaired. Therefore, the average particle size of the filler is set to 3 to 10 μm, which is smaller than that of the conventional liquid sealing material, and the particle size of 30 μm or more is reduced to 25% by weight or less in all the filler components. Therefore, the fluidity is not impaired. In addition, the amount of 1 μm or less is 6 to 45% by weight in all the filler components, and an appropriate amount of fine filler is added to control the particle size distribution to prevent the fine filler from sinking during curing. You can The particle size distribution and the average particle size referred to in the present invention are laser type (Ho
riba, LA-500). The average particle diameter was the median diameter. The liquid encapsulating material of the present invention includes, in addition to the above-mentioned essential components, other resins and catalysts for accelerating the reaction as necessary, a diluent, a pigment, a coupling agent, a flame retardant, a leveling agent, and a quenching agent. Additives such as foaming agents may be used.
The liquid encapsulating material is produced, for example, by dispersing and kneading each component, additive, etc. with a three-roll and defoaming treatment under vacuum.

[0010]

The present invention will be described below with reference to the following examples and comparative examples. Bisphenol F diglycidyl ether type epoxy resin: (epoxy equivalent 155, 1.6 Pa · s / 25 ° C.) 100 parts by weight Naphthalene F diglycidyl ether type epoxy resin: (equivalent weight 135, 124 Pa · s or less / 25 ° C.) Alkylated diaminodiphenylmethane curing agent: (Amino equivalent 65) 42 parts by weight Polybutadiene rubber having an epoxy group: 5 parts by weight (number average molecular weight 1500, epoxy content 5 mol%) Glycidyltrimethoxysilane: 6 parts by weight Melting Silica: 350 parts by weight Carbon black: 1 part by weight The above raw materials were dispersed and kneaded by a three-roll mill and defoamed under vacuum to obtain a liquid sealing material. A PPGA package was encapsulated using the obtained liquid encapsulating material and cured in an oven at 165 ° C. for 3 hours to obtain a semiconductor package.

<< Evaluation Method >> Viscosity: The value was measured by an E-type viscometer (25 ° C.) at 2.5 rpm. The higher the value, the worse. When the viscosity exceeds 50 Pa · s, workability at the time of dispensing deteriorates. -Thixo ratio: 0.5 rpm and 2.5 rpm with the above viscometer
The ratio of the viscosity in m was taken as the value. -Storage property: Time was taken for the viscosity to be twice the initial viscosity. ○: 72 hours or more, △: 24-72 hours, ×: 24 hours or less ・ Curable: Injecting a liquid sealing material into PPGA package piece parts and curing under curing conditions of 165 ° C./3 hours,
The number of voids on the package surface and filler separation were observed. The number of voids on the surface of the package was observed with a microscope, and voids of several μm or more were taken as luck. The unfilled package is
It was observed with an ultrasonic killer (hereinafter referred to as SAT). For the filler separation, the cross section of the package was polished, and the thickness of the resin layer on the surface was measured. Those having a size of 5 μm or more were indicated as having filler separation. 1 PPGA package evaluated
There are zero.・ Peeling / cracking after curing Before treatment PCT treatment (125 ° C / 2.3 atm) 720 hours later T / C treatment (-65 ° C / 30 minutes ← → 150 ° C / 30
Min) After 1000 cycles, the presence or absence of cracks and peeling between the semiconductor chip and the printed circuit board interface was confirmed using SAT. The number of evaluated PPGA packages is 10
Individual.

Table 1 Silica ABC D E F Average particle size (μm) 5.4 4.2 7.8 2.5 3.2 7.3 1 μm or less weight% 30 39 20 40 48 10 1-30 μm weight% 55 52 62 55 51 61 30 μm or more weight% 15 9 18 5 1 29

Table 2 Example 1 2 3 4 5 compounding (parts by weight) bisphenol F type glyceryl ether epoxy resin 100 100 100 100 60 naphthalene type glyceryl ether-terepoxy resin 40 alkylated diaminodiphenylmethane 42 42 42 42 42 47 polybutadiene rubber 5 5 5 5 5 Glycidyltrimethoxysilane 6 6 6 6 6 Carbon black 1 1 1 1 1 Fused silica A 350 500 350 Fused silica B 350 Fused silica C 350 Characteristic viscosity (Pa · s) 30 45 36 24 38 Thixo ratio 1.2 1.2 1.3 1.1 1.3 Storability ○ ○ ○ ○ ○ Number of curable voids 0 0 0 0 0 Unfilled 0 0 0 0 0 Filler separation No No No No No Peeling after curing Peeling 0 0 0 0 0 0 PCT Treatment Peeling 0 0 0 0 0 Crack 0 0 0 0 0 0 After T / C treatment Peeling 0 0 0 0 0 0 Crack 0 0 0 0 0

Table 3 Comparative Example 1 2 3 4 5 Compounding (parts by weight) Bisphenol F type glyceryl terepoxy resin 100 100 100 100 30 Naphthalene type glyceryl tereoxy resin 70 Alkylated diaminodiphenylmethane 42 42 42 42 42 42 Polybutadiene rubber 5 5 5 5 5 Glycidyltrimethoxysilane 6 6 6 6 6 Carbon black 1 1 1 1 1 Fused silica A 200 350 Fused silica D 350 Fused silica E 350 Fused silica F 350 Characteristic viscosity (Pa · s) 43 54 27 17 76 Thixo ratio 1.1 1.2 1.3 1.1 1.3 Storability ○ ○ ○ ○ × Number of curable voids 2 15 0 0 3 Unfilled 1 2 0 0 20 Filler separation Yes No Yes No No No Peeling after curing 0 0 0 0 0 PCT Crack 0 0 0 0 0 PCT Peeling after treatment 0 0 0 10 4 Crack 0 0 0 6 2 T / C Peeling after treatment 0 0 0 10 10 Crack 0 0 0 0 10 0

[0014]

Industrial Applicability When the semiconductor package is encapsulated with the liquid encapsulating material of the present invention, a highly reliable semiconductor free from peeling cracks can be obtained even in a pressure cooker test or a thermal cycle test, which is an industrial advantage. Is.

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Claims (2)

[Claims] 1. A liquid epoxy resin, (b) an aromatic amine curing agent alkylated diaminodiphenylmethane which is liquid at room temperature, (c) a polybutadiene compound having an epoxy group, (d) an epoxy group, an amino group, A silane coupling agent having one or more functional groups selected from the group of mercapto groups in the molecule, and (e) a liquid encapsulating material containing an inorganic filler having a specific particle size distribution shown below as a main component, The mixing ratio of each component is (c) / weight ratio
{(A) + (b) + (c)} = 0.03-0.10,
(D) / {(a) + (b) + (c)} = 0.02-0.
10 and (e) / {(a) + (b) + (c) +
(D) + (e)} = 0.50-0.80, The liquid sealing material characterized by the above-mentioned. 2. The (e) inorganic filler has an average particle size of 3 to 10.
6 μm with a particle size of 1 μm or less in all inorganic filler components
The liquid encapsulating material according to claim 1, which has a particle size distribution of not more than 45% by weight and a particle size of 30 μm or more in all inorganic filler components of 25% by weight or less.