JPH10158366A - Liquid injection sealing underfill material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a liquid injection sealing underfill material for semiconductor packages that does not cause exfoliation and cracks even in pressure cracker test and thermal cycle test. SOLUTION: This liquid injection sealing underfill material contains, as main components, (a) a liquid epoxy resin, (b) an aromatic amine-based curing agent, an alkylated diaminodiphenylmethane, (c) a silane coupling agent having one or more functional groups selected from epoxy, amino and mercapto groups in one molecule, and (d) an inorganic filler having a specific particle size distribution, in such conditions that compounding ratios of respective components by weight is in relationships of (c)/[(a)+(b)+(c)]=0.01 to 0.05 and (d)/[(a)+(b)+(c)+(d)]=0.50 to 0.80, and that the inorganic filler has an average particle size of 4-6μm, and contains 20-70wt.% of particles of 1μm or smaller size, and 30wt.% or less of particles of 30μm or larger size up to 50μm, with larger particle sizes than 50μm cut out.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art With the progress of high-density and high-integration IC chips, a flip-chip packaging system, which has a short wiring length, is suitable for high frequency use, and has a large number of pins, has been increasingly used. This mounting is almost the size of the chip size,
Furthermore, since a chip can be directly mounted on a printed circuit board, it is possible to reduce the size, weight, and thickness. Bare chip technology has also been established, but it is difficult to obtain perfectly good chips, so filling reinforcement with an injection-sealed underfill material is necessary.

A liquid sealing material is used for the flip-chip mounting type semiconductor encapsulation, but it is not sufficient in terms of reliability as compared with a hermetic encapsulation type using ceramics. ) Plastic packages were less popular than dies. The causes of the decrease in the reliability of the flip-chip mounted semiconductor are as follows: (1) Insufficient filling of the injection-sealing underfill material
Impurities and moisture from outside air enter. (2) Moisture enters from the organic printed wiring board. (3) Impurities enter from the solder bumps. (4) Since the liquid injection sealing underfill material flows into the package under no pressure and is hardened, bubbles remain in the sealing material and cracks occur when thermal stress is applied. (5) When thermal stress is applied due to the difference in the coefficient of linear expansion between the sealing material and the semiconductor chip, the organic substrate, and the solder bumps, peeling occurs at the interface to facilitate moisture penetration. (6) Mechanical damage to the chip due to the same thermal stress,
Loss occurs. And the like.

[0004]

SUMMARY OF THE INVENTION Accordingly, the present inventors
As a result of diligent studies to solve such conventional problems, liquid epoxy resin, aromatic amine-based curing agent alkylated diaminodiphenylmethane, and silane coupling agent, a non-permanent filler having a specific particle size distribution is used. The blended composition was tested under a pressure cooker test (hereinafter, PC
The present invention has been found to be a package material that can significantly improve the reliability of a semiconductor even in accelerated tests such as a thermal cycle test (hereinafter referred to as T / C) and a thermal cycle test (hereinafter referred to as T / C), thereby completing the present invention.

[0005]

The present invention is selected from the group consisting of (a) a liquid epoxy resin, (b) an alkylated diaminodiphenylmethane of an aromatic amine curing agent, and (c) an epoxy group, an amino group, and a mercapto group. In a silane coupling agent having at least one functional group in a molecule, and (d) a liquid injection underfill material mainly composed of an inorganic filler having a specific particle size distribution, the mixing ratio of each component is weight. By ratio
(c) / {(a) + (b) + (c)} = 0.01-0.05, and (d) / {(a) + (b)
+ (c) + (d)} = 0.50 to 0.80, and the inorganic filler of (d) has an average particle size of 0.4 to 6 μm and a particle size of 1 μm or less is 20 to 100% of the total inorganic filler component. 50% by weight and less than 30% by weight of the total inorganic filler component
It is a liquid injection-sealed underfill material containing an inorganic filler having a particle size distribution cut to m or more, and can greatly improve the reliability of a flip-chip mounted semiconductor using an organic printed wiring board.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The liquid epoxy resin (a) used in the present invention preferably has a viscosity at 25 ° C. of 10 PA · s or less for at least 50% by weight of its components. Unless 50% by weight or more of the epoxy resin component is a low-viscosity liquid epoxy, the viscosity of the composition becomes high, and when flowing in and sealing the inside of the flip-chip mounting package with the liquid injection sealing underfill material, bubbles may be involved or corners may be generated. This is not preferable because poor filling at the end is likely to occur, leading to a reduction in reliability.

As a method for measuring the viscosity of an epoxy resin, in the case of a material which is liquid at room temperature, the temperature is measured at 25 ° C. by Toki Sangyo Co., Ltd.
It is measured with an E-type viscometer or Brookfield viscometer.
As long as the epoxy resin satisfies this requirement, it is not particularly limited, but specific examples include bisphenol A diglycidyl ether type epoxy and bisphenol F
Diglycidyl ether type epoxy, bisphenol S diglycidyl ether type epoxy, 3,3 ', 5,5'-tetramethyl-4,4'-dihydroxybiphenyl diglycidyl ether type epoxy, 4,4'-dihydroxybiphenyl diglycidyl ether Type epoxy, 1,6-dihydroxybiphenyl diglycidyl ether type epoxy, phenol novolak type epoxy, bromine type cresol novolak type epoxy, bisphenol D diglycidyl ether type epoxy and the like. These may be used alone or in combination.
Further, in order to obtain a liquid injection sealing underfill material having excellent reliability, it is preferable that the epoxy resin that can be used has as little ionic impurities as possible, such as Na ⁺ and Cl ⁻ .

The aromatic amine curing agent (b) used in the present invention is an alkylated diaminodiphenylmethane. 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 liquid injection underfill material with excellent reliability, it is preferable that the amine hardener that can be used has as little ionic impurities as possible, such as Na ⁺ and Cl ⁻ . The aromatic amine curing agent referred to herein is 3,3 ', 5,5'-tetramethyl-
4,4'-diaminodiphenylmethane, 3,3'-diethyl-4,4'-
And diaminodiphenylmethane. The combination of the aromatic amine curing agent (b) and the liquid epoxy resin (a) can provide a material having extremely good fluidity. 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 mixing molar ratio of the epoxy resin (a) as the main ingredient and the alkylamine diaminodiphenylmethane as the curing agent (b) is preferably 0.9 to 1.2. If the curing agent is 0.9 or less and the amount of the curing agent is excessive, unreacted amino groups will remain excessively, leading to a decrease in moisture resistance and a decrease in reliability. Conversely, when the ratio is 1.2 or more, that is, when the amount of the epoxy resin increases, the curing becomes insufficient, which leads to a decrease in reliability.

[0010] As the inorganic filler (hereinafter simply referred to as a filler) of (d), for example, 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 (d) / {(a) + (b) + (c) +
(d)} = 0.50 to 0.80 is desirable. If it is less than 0.50, the above-described effect of reducing the coefficient of linear expansion is small. If it exceeds 0.80, the viscosity of the resulting liquid injection underfill material becomes too high, which is not a practical level.

The flow characteristics such as viscosity can be maximized by adjusting the particle size distribution of the filler. In general, fillers with a broad particle size distribution,
It is known that a filler having a larger particle size tends to have a lower viscosity. However, for the purpose of lowering the viscosity, fillers with only a large particle size of, for example, 50 μm or more, although the viscosity surely decreases, the relatively heavy filler of specific gravity sinks during curing, and the top and bottom of the cured product So-called filler sedimentation having a different composition ratio occurs. A disadvantage of using a filler having a large particle size is that it does not flow into a narrow gap. There is also a tendency for packages to be multi-pin and space-saving, and the height (Stand OFF) between the substrate and the chip is becoming narrower. In order to flow the liquid-filled sealing underfill material under no pressure and to form such that there is no fluidity defect such as void or unfilled under such pressure, the particle size of the filler must be minimized. 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 0.4 to 6 μm.
And smaller than that of the conventional liquid sealing material, and the particle size
20% or more of the total filler component is 30% by weight or less of the total filler component. By cutting 50μm or more and reducing the particle size, the fluidity is not impaired and the gap between the chip and the substrate can be sewn and filled. It became. In addition, the particles having a particle size of 1 μm or less can be uniformly filled by adjusting the particle size distribution to 20 to 100% by weight of the total filler components.

[0013] In addition to the above-mentioned essential components, the liquid injection sealing underfill material of the present invention may further comprise other resins or catalysts, diluents, pigments, elastomers, and coupling agents for accelerating the reaction. Additives such as a flame retardant, a leveling agent and an antifoaming agent may be used.

As the elastomer, a polybutadiene compound having an epoxy group, which has good compatibility with the epoxy resin (a) and is expected to have low stress and toughness, a random copolymerized silicone modified epoxy, and a random copolymer Examples thereof include a polymerized silicone-modified phenolic resin and an epoxy group-containing polyolefin, and may be used alone or in combination. In general, elastomers have a property of being poor in moldability due to bleeding after injection curing due to lack of compatibility with an epoxy resin. However, the above elastomer incorporating an epoxy group in a part of the molecule is compatible, partially reacts with the curing agent (b) and crosslinks, so that the bleeding property is improved, and the stress and toughness are also reduced. It is thought that it can be expressed.

To confirm the reduction of stress, for example, a three-point bending test,
Confirmation of toughness includes, for example, KIC measurement, and excellent results can be obtained from any of the test results.
By adjusting the amount of the elastomer, low stress and high toughness can be obtained. The amount of addition is 0.
1% to 1.0% is desirable, but if less than 0.1%, the effects of lowering the stress and increasing the toughness cannot be expected. In particular, surface cracks occur during T / C, leading to poor reliability. Also, 1.
If it is more than 0%, the compatibility with the epoxy resin (a) will be poor, and the oil will float on the package surface and cause bleeding, which will cause a reduction in moldability. The liquid injection sealing underfill material is produced by, for example, dispersing and kneading each component, additive, and the like with a three-roll, two-heat roll, and a vacuum mixer, and then performing a defoaming process under vacuum.

[0016]

The present invention will be described below with reference to the following examples and comparative examples. [Example 1] Bisphenol F type epoxy resin (equivalent weight: 155, 1.6 Pa · s @ 25 ° C) 100 parts by weight Diethyldiaminodiphenylmethane 21 parts by weight Tetramethyldiaminodiphenylmethane 21 parts by weight Glycidyltrimethoxysilane 3 parts by weight Fused silica A 200 parts by weight Part Carbon black 1 part by weight The characteristics of the fused silica used are shown in Table 1.

[0017]

[Table 1]

The above raw materials were dispersed and kneaded with three rolls and subjected to a defoaming treatment under vacuum to obtain a liquid injection-sealed underfill material. The obtained liquid injection sealing underfill material is injected into a flip-chip mounting package for 5 minutes on a hot plate at 80 ° C., and then at 120 ° C. for 1 hour and further for 1 hour.
Cured in an oven at 65 ° C. for 2 hours to obtain a semiconductor package. The viscosity was measured at 5 rpm with a BrookField viscometer (@ 25C).
The value measured in was used as a value. The higher the value, the worse. If the viscosity exceeds 500 poise, the workability at the time of dispensing becomes poor. The thixotropic ratio was 0.5 rpm with the above viscometer.
The ratio of the viscosity at 5 rpm was taken as the value. Storage time was taken to be twice the initial viscosity. Using an ultrasonic flaw detector (hereinafter referred to as C-SAM), the presence or absence of voids in the package (expressed in terms of package filling properties), the separation between the semiconductor chip surface and the printed circuit board bump interface, and the presence or absence of cracks were confirmed. PCT treatment (125 ° C / 2.3atm), T / C treatment (-65 ° C / 30atm)
Min. →→ 150 ° C./30 min.) And the presence or absence of peeling and cracking between the semiconductor chip and the printed circuit board interface was confirmed by SAT.
No such phenomenon was observed at all until the 00 cycle, and it was found that the device had good reliability. The number of flip-chip mounting packages used for each evaluation is ten. The size of the chip is 15 mm square, and the gap with the substrate is 100 μm. Table 2 shows the evaluation results.

Examples 2 to 5 and Comparative Examples 1 to 5
A liquid injection sealing underfill material was obtained in the same manner as in Example 1 except for the compounding of. Using the obtained liquid injection underfill material, a semiconductor package was obtained in the same manner as in Example 1. Table 2 shows the evaluation results.

[0020]

[Table 2] (Naphthalene F-type epoxy resin (equivalent to 135, 124 Pa
25C))

[0021]

When a semiconductor package is sealed with the liquid injection sealing underfill material of the present invention, a highly reliable semiconductor without peeling cracks can be obtained even in a pressure cooker test or a thermal cycle test. Is a great merit.

Claims (1)

[Claims] 1. A compound selected from the group consisting of (a) a liquid epoxy resin, (b) an alkylated diaminodiphenylmethane, an aromatic amine-based curing agent, and (c) an epoxy group, an amino group, and a mercapto group.
In a silane coupling agent having at least two functional groups in the molecule, and (d) a liquid injection underfill material containing an inorganic filler as a main component, the mixing ratio of each component is (c) / { (a) + (b) + (c)} = 0.01-0.05, and (d) / {(a) +
(b) + (c) + (d)} = 0.50 to 0.80, and the inorganic filler is
Those having an average particle size of 0.4 to 6 μm and a particle size of 1 μm or less account for 20 to 100% by weight of all the inorganic filler components and a particle size of 20 μm.
A liquid-filled sealing underfill material characterized in that at least 30% by weight of the total inorganic filler component is an inorganic filler having a particle size distribution cut at 50 μm or more.