JP2000327884A - Underfill material for flip-chip semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an underfill material which is excellent in preservation stabilty and penetration into gaps and gives a highly reliable cured item by incorporating a liquid epoxy resin, spherical silica prepared by heating and burning spherical polyorganosilsesquioxane particles, and a cure accelerator into the same. SOLUTION: This underfill material for flip-chip semiconductor devices contains 100 pts.wt. liquid epoxy resin; 100-300 pts.wt. spherical silica which is prepared by heating and burning spherical polyorganosilsesquioxane particles, has a max. particle size of 50 μm or lower and an average particle size of 0.5-10 μm, and contains 0.005-0.1 wt.% carbon particles on the surface; and 0.01-10 pts.wt. cure accelerator. A flip-chip semiconductor device has such a structure that a semiconductor chip 3 is mounted, via a plurality of bumps 2, on the wiring pattern face of an organic substrate 1; the gaps between the organic substrate 1 and the semiconductor chip 3 are filled with the underfill material 4; and the side is sealed with a fillet material 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an underfill material for a flip-chip type semiconductor device.

[0002]

2. Description of the Related Art With the miniaturization, weight reduction, and enhancement of functions of electric equipment, semiconductor mounting methods have become the mainstream from pin insertion type to surface mounting. And one of bare chip mounting is flip chip (FC)
There is an implementation. FC mounting is a method in which several to thousands of electrodes called bumps having a height of about 10 to 100 μm are formed on the wiring pattern surface of an LSI chip, and the electrodes on the substrate are joined by a conductive paste or solder. For this reason, it is necessary that the sealing material used to protect the FC penetrates into a gap of about several tens of μm formed by bumps or the like of the substrate and the LSI chip. The liquid epoxy resin composition used as the conventional underfill material for flip chips is composed of an epoxy resin, a hardener and an inorganic filler. In order to achieve the same, a formulation incorporating a large amount of an inorganic filler has become mainstream.

[0003] However, in the underfill material for a flip chip in which such a filler is highly filled, there is no longer any problem in the stress characteristics, but on the other hand, the viscosity increases due to the increased filling of the filler. There is a problem that the speed of entering the gap between the chip and the substrate is remarkably reduced, and the productivity is extremely deteriorated. It is desired to improve this problem.

It is well known that when a large amount of an inorganic filler is filled, the particle size distribution of the filler and the state of the filler surface greatly affect the viscosity of the final product. Therefore, conventionally, the spherical silica obtained by flame melting has been subjected to air classification or a sieve to remove coarse particles and fine powder, or the optimum particle size distribution has been adjusted by combining spherical silica having different particle sizes. This method has a problem that the raw material price increases because the yield is very poor.

Further, conventionally, in order to improve the affinity between the silica surface and the epoxy resin and the adhesive strength, a surface modifier such as a silane coupling agent is usually used. However, in the case of the underfill material, since it is heated and hardened in a very narrow gap, there is a problem that even a small amount of a volatile component causes a void.

The present invention has been made in view of the above circumstances. Even if a large amount of an inorganic filler is compounded, the viscosity can be made to penetrate into the gap with low viscosity, and excellent reliability without generation of voids or the like can be obtained. An object of the present invention is to provide an underfill material for a flip-chip type semiconductor device which gives a cured product.

[0007]

Means for Solving the Problems and Embodiments of the Invention The present inventors have conducted intensive studies to achieve the above object, and as a result, have found that an epoxy resin composition used as an underfill material of a flip-chip type semiconductor device has: As an inorganic filler, spherical silica obtained by heating and burning polyorganosilsesquioxane spherical particles, particularly having a maximum particle size of 50
μm or less, the average particle size is 0.5 to 10 μm, and by using spherical silica containing carbon atoms on the surface, the affinity with the epoxy resin is improved, and a large amount of the inorganic filler (the above-mentioned spherical silica) can be used. It has been found that even if it is blended, the gap penetration into the narrow portion is remarkably improved and the reliability of the semiconductor device can be improved, and the present invention has been accomplished.

Accordingly, the present invention relates to: (A) 100 parts by weight of a liquid epoxy resin; and (B) spherical silica obtained by heating and burning polyorganosilsesquioxane spherical particles: 100 to 3 parts.
The present invention provides an underfill material for a flip-chip type semiconductor device, characterized by comprising: 00 parts by weight (C) a curing accelerator: 0.01 to 10 parts by weight.

Hereinafter, the present invention will be described in more detail. As the liquid epoxy resin of the component (A) used in the present invention, any one can be used as long as it has two or more epoxy groups in one molecule. In particular, bisphenol A epoxy resin and bisphenol F epoxy resin can be used. Bisphenol type epoxy resin such as epoxy resin, phenol novolak type epoxy resin, novolak type epoxy resin such as cresol novolak type epoxy resin, triphenol methane type epoxy resin, triphenol alkane type epoxy resin such as triphenol propane type epoxy resin, naphthalene Epoxy resin, biphenyl epoxy resin,
A cyclopentadiene type epoxy resin is exemplified.
Among these, epoxy resins that are liquid at room temperature are used, and in particular, bisphenol A epoxy resin, bisphenol F
A bisphenol type epoxy resin such as a type epoxy resin is desirable. There is no problem even if an epoxy resin having the following structure is added to these epoxy resins within a range that does not affect the infiltration property.

[0010]

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The total chlorine content in the liquid epoxy resin is preferably 1500 ppm or less, more preferably 1000 ppm or less. The extraction water chlorine in 20 hours at 120 ° C. and 50% epoxy resin concentration was 5 pp.
m or less. Total chlorine content is 1500
If the content exceeds 1 ppm and the amount of extracted water chlorine exceeds 5 ppm, the reliability of the semiconductor element, particularly, the moisture resistance may be adversely affected.

Next, the spherical silica as the component (B) of the present invention is obtained by heating and burning polyorganosilsesquioxane spherical particles. In this case, examples of the polyorganosilsesquioxane include polyalkylsilsesquioxanes represented by polymethylsilsesquioxane, polyethylsilsesquioxane, and the like. Among these, the polyorganosilsesquioxane spherical powder is particularly preferable as the polyorganosilsesquioxane spherical powder.

Here, polyorganosilsesquioxane which is a raw material of the spherical silica used in the present invention is disclosed in
According to the method described in JP-A-33337, a mixture of a trifunctional organoalkoxysilane or a partial hydrolyzate thereof and an organic solvent is subjected to hydrolytic condensation with stirring in an aqueous solution containing an alkaline substance. It can be easily obtained by neutralization, and polyorganosilsesquioxane particles having a narrow particle size distribution can be obtained by this method. In this case, the trifunctional organoalkoxysilane may be methyltrimethoxysilane, methyltriethoxysilane, methyltripropoxysilane, or other lower alkyl group such as ethyl group, propyl group, butyl group, etc. And a silane substituted with a monovalent hydrocarbon group. Among them, alkyltrialkoxysilanes such as methyltrialkoxysilane and ethyltrialkoxysilane can be preferably used.

The polyorganosilsesquioxane particles have an average particle size of 0.5 to 10 μm, particularly 1 to 5 μm, and the ratio of particles having a particle size distribution in the range of ± 30% of the average particle size is as follows. It is preferably at least 80% (% by weight, the same applies hereinafter). This polyorganosilsesquioxane is
By burning and sintering at a temperature of 00 to 1000 ° C., spherical silica having the same particle size distribution (maximum particle size, average particle size) as the raw material polyorganosilsesquioxane can be easily obtained. Is what you can do.

In this case, in the present invention, the oxidative decomposition of the silicon-carbon bond is suppressed by controlling the amount of oxygen during combustion in air, and an appropriate amount of carbon is left on the silica surface to form a liquid. The affinity between the epoxy resin and the filler surface can be increased. As carbon remaining on the surface, 0.005 to
0.1%, desirably 0.01 to 0.08%.
If the amount is less than 0.005%, sufficient affinity may not be obtained. On the other hand, if the amount is more than 0.1%, the amount of SiC increases and the film becomes conductive, and thus is not suitable as an insulating material. There is a fear. Therefore, it is more preferable to use one in which even a little carbon remains than in the case where no carbon is present, since it is possible to cause the resin to penetrate into the narrow gap of the flip-chip type semiconductor device in a short time. Even those that do not exist are manufactured by the above method,
If the particle size distribution is in the above range, it can be used without any problem.

By using the silica spherical particles containing the carbon obtained by this method, preferably containing the above-mentioned specific amount, the same cured product characteristics as those obtained by the conventional method can be obtained with a smaller amount of the coupling agent than before and the volatile components Is less likely to occur, and high reliability as a semiconductor device can be secured. In addition, since the affinity between the resin and the filler is improved, it is possible to reduce the viscosity of the epoxy resin composition, and it is possible to achieve both improved penetration and high filling for low linear expansion. Becomes

As for the characteristics of these silicas, the average particle size is preferably about 1/10 or less and the maximum particle size is 1/2 or less with respect to the flip chip gap width in order to improve the penetration property.
Usually, the maximum particle size is 50 μm or less, preferably 25 μm or less, more preferably 10 μm or less. Average particle size is 1
0 μm or less (usually 0.5 to 10 μm), preferably 5 μm
μm or less, more preferably 1 to 5 μm.

The amount of the spherical silica is 100 to 300 parts by weight based on 100 parts by weight of the liquid epoxy resin, and especially 100 to 250 parts by weight based on 100 parts by weight of the liquid epoxy resin.
A range of parts by weight is preferred. If the compounding amount is small, the expansion coefficient is large, and the generation of cracks is induced in the thermal test. On the other hand, if the compounding amount is large, the viscosity becomes high, and the penetration of the thin film is reduced.

In the present invention, the surface carbon content of the spherical silica was measured at 1300 ° C. using a carbon content analyzer.
Is a value measured by quantifying the carbon dioxide gas generated by heating the silica in the above, and is usually the amount of carbon on the particle surface. The average particle diameter can be determined as a weight average value (or median diameter) by a laser light diffraction method or the like.

The underfill material of the present invention may contain other inorganic fillers in addition to the spherical silica obtained by heating and firing the above polyorganosilsesquioxane. Examples of the inorganic filler include spherical or crushed fused silica, crystalline silica, silica fine powder such as spherical silica obtained by a sol-gel method, alumina, boron nitride, aluminum nitride, silicon nitride, magnesia, magnesium. Silicates and the like can be mentioned, and among them, spherical fused silica is preferable. In this case, the inorganic filler as the optional component is also similar to the spherical silica of the component (B),
The maximum particle size is 50 μm or less, preferably 25 μm or less, more preferably 10 μm or less, and the average particle size is 10 μm.
In the following, it is preferable to use those having a thickness of usually 0.5 to 10 μm, preferably about 1 to 5 μm.

When the inorganic filler of the optional component is used in combination with the spherical silica of the component (B), the mixing ratio of the component (B) to the entire inorganic filler including the component (B) is 6
0% by weight or more (that is, 60 to 100% by weight), particularly 65% by weight.
It is preferable that the content be in the range of from 99 to 99% by weight, especially 80 to 99% by weight.

The component (C) of the present invention is a curing accelerator,
Known curing accelerators can be used. Specifically, one or two or more selected from an imidazole compound, a tertiary amine compound, and an organic phosphorus compound can be blended. Here, as the imidazole compound, 2-methylimidazole, 2-ethylimidazole, 4-methylimidazole, 4-ethylimidazole, 2-phenylimidazole, 2-phenyl-4-imidazole
Methylimidazole, 2-phenyl-4-hydroxymethylimidazole, 2-ethyl-4-methylimidazole, 1-cyanoethyl-2-methylimidazole, 2-
Phenyl-4-methyl-5-hydroxymethylimidazole, 2-phenyl-4,5-dihydroxymethylimidazole and the like. Further, as the tertiary amine compound, triethylamine, benzyltrimethylamine,
amine compounds having an alkyl group or an aralkyl group as a substituent bonded to a nitrogen atom such as α-methylbenzyldimethylamine, 1,8-diazahycyclo [5.4.0] undecene-7 and its phenol salt, octylate, Examples thereof include a salt of a cycloamidine compound such as an oleate and an organic acid thereof, and a salt or a complex salt of a cycloamidine compound such as a compound of the following formula and a quaternary boron compound.

[0023]

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Examples of the organic phosphorus compounds include triorganophosphine compounds such as triphenylphosphine, and quaternary phosphonium salts such as tetraphenylphosphonium tetraphenylborate.

The compounding amount is 0.01 to 10 parts by weight, desirably 0.5 to 100 parts by weight of the epoxy resin.
-5 parts by weight. If the amount is less than 0.01 part by weight, the curability is reduced. If the amount is more than 10 parts by weight, the curability is excellent, but the storage stability tends to be reduced.

Here, the epoxy resin can be cured with the curing accelerator alone, but if necessary, a curing agent such as tetrahydrophthalic anhydride,
Methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, hexahydrophthalic anhydride, methylhymic anhydride, pyromellitic dianhydride, benzophenonetetracarboxylic dianhydride, 3,3 ', 4,4'-biphenyl Tetracarboxylic dianhydride, bis (3,4-dicarboxyphenyl) ether dianhydride, bis (3,4
-Dicarboxyphenyl) methane dianhydride, 2,2-bis (3,4-dicarboxyphenyl) propane dianhydride, etc., preferably having one aliphatic or aromatic ring in the molecule.
Or two, and an acid anhydride group (that is, -CO-
An O—CO— group) having 1 or 2 carbon atoms,
It is possible to use about 25, preferably about 8 to 20 acid anhydrides and carboxylic acid hydrazides such as dicyandiamide, adipic hydrazide, and isophthalic hydrazide.

When an acid anhydride is used as a curing agent, the ratio of the acid anhydride group in the curing agent to the mol of epoxy group in the epoxy resin is in the range of 0.3 to 0.7 mol. It is desirable. If it is less than 0.3 mol, the curability is insufficient, and if it exceeds 0.7 mol, unreacted acid anhydride remains and the glass transition temperature may be lowered. More preferably, it is in the range of 0.4 to 0.6 mol.

The composition of the present invention may be blended with a thermoplastic resin such as silicone rubber, silicone oil, liquid polybutadiene rubber, or methyl methacrylate-butadiene-styrene copolymer, for the purpose of reducing stress. Preferably, the alkenyl group of the alkenyl group-containing epoxy resin or phenol resin and the number of silicon atoms in one molecule represented by the following formula (1) are 20 to 400, preferably 40 to 200, and the number of SiH groups is It is preferable to blend a copolymer obtained by an addition reaction of the organopolysiloxane with SiH groups of 1 to 5. H _a R _b SiO _{(4-ab) / 2} (1) (wherein, R is a substituted or unsubstituted monovalent hydrocarbon group, a is 0.005 to 0.1, b is 1.8 to 2. 2, 1.81 ≦
It indicates a positive number satisfying a + b ≦ 2.3. )

The monovalent hydrocarbon group of R preferably has 1 to 10 carbon atoms, particularly 1 to 8 carbon atoms.
Ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, tert-butyl group, hexyl group, cyclohexyl group, octyl group, alkyl group such as decyl group, vinyl group, allyl group, propenyl group, butenyl group, hexenyl group Alkenyl groups such as phenyl group, xylyl group, and tolyl group; aralkyl groups such as benzyl group, phenylethyl group, and phenylpropyl group; and a part or all of hydrogen atoms of these hydrocarbon groups. A chloromethyl group substituted by a halogen atom such as fluorine, bromine,
Examples thereof include a halogen-substituted monovalent hydrocarbon group such as a bromoethyl group and a trifluoropropyl group. Among the above copolymers, those having the following structures are particularly desirable.

[0030]

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[0031]

Embedded image (In the above formula, R is the same as above, R ¹ is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and R ² is —CH ₂ CH ₂ CH ₂ —, −
OCH ₂ —CH (OH) —CH ₂ —O—CH ₂ CH ₂ CH ₂
— Or —O—CH ₂ CH ₂ CH ₂ —. n is 4 to 19
9, preferably an integer of 19 to 99, p is an integer of 1 to 10, and q is an integer of 1 to 10. )

In the above copolymer, the diorganopolysiloxane unit is contained in an amount of 0 to 20 parts by weight, preferably 2 to 20 parts by weight, based on 100 parts by weight of the total amount of the liquid epoxy resin and the curing agent (when blended).
By blending so as to contain 15 parts by weight, the stress can be further reduced.

The sealing material (liquid epoxy resin composition) of the present invention may further contain, if necessary, pigments such as carbon-functional silane for improving adhesion, carbon black, dyes, antioxidants,
A surface treating agent (such as a silane coupling agent such as γ-glycidoxypropyltrimethoxysilane) and other additives can be blended.

The epoxy resin composition of the present invention is, for example,
Epoxy resin, curing agent, curing accelerator, inorganic filler simultaneously or separately stirring while adding heat treatment as necessary,
It can be produced by dissolving, mixing and dispersing. The apparatus for mixing, stirring, and dispersing these mixtures is not particularly limited, but a stirring and heating apparatus equipped with a heating device,
A three roll, ball mill, planetary mixer or the like can be used. These devices may be used in appropriate combination.

In the present invention, the viscosity of the underfill material, that is, the liquid epoxy resin composition used as a sealing material for the underfill portion, is 10,000 at 25 ° C.
Those having 0 poise or less are preferred. In addition, the underfill material of the present invention preferably has an expansion coefficient of 20 to 40 ppm / ° C. or less, particularly 20 to 30 ppm / ° C. or lower at a glass transition temperature or lower, in view of gap filling properties and thermal shock resistance.

Although the underfill material of the present invention is used for flip-chip type semiconductor devices, the flip-chip type semiconductor device according to the present invention, as shown in FIG. Multiple bumps 2
The semiconductor chip 3 is mounted via
A gap between the organic substrate 1 and the semiconductor chip 3 (a gap between the bumps 2) is filled with an underfill material 4, and a side portion thereof is sealed with a fillet material 5.

The fillet material is not particularly limited, and an epoxy resin composition, particularly an epoxy resin composition having the same components as the above-described underfill material, can be used (however, as an inorganic filler, Is
In addition to the above-mentioned spherical silica, fused silica, crystalline silica, alumina, boron nitride, aluminum nitride, silicon nitride, magnesia, magnesium silicate, etc. are used, but the expansion coefficient below the glass transition temperature is 20 ppm.
/ C, preferably 5 to 19 ppm / C, more preferably 10 to 18 ppm / C.

The molding method and molding conditions of the above-mentioned underfill material may be conventional methods, but it is preferable to cure and mold the material at 150 ° C. for 0.5 hour or more using a hot oven.

[0039]

EXAMPLES The present invention will be described below in detail with reference to examples and comparative examples, but the present invention is not limited to the following examples.

Examples and Comparative Examples Eight types of epoxy resin compositions were obtained by uniformly kneading the components shown in Tables 1 and 2 with a three-roll mill. The following tests were performed using these epoxy resin compositions. The results are shown in Tables 1 and 2.

[Viscosity] 20 r using a BH type rotational viscometer
The viscosity at 25 ° C. was measured at a rpm of pm. [Thixo ratio] Using a BH-type rotational viscometer at 2 rpm and 20 rpm
The ratio of the viscosity at rpm was the thixo ratio at 25 ° C. [Gelling time] The gelling time of the composition was measured on a hot plate at 150 ° C. [Tg]: glass transition temperature T using a cured product sample of 5 mm × 5 mm × 15 mm
The value when the temperature was raised at a rate of 5 ° C./min by an MA (thermomechanical analyzer) was measured. [CTE-1]: Expansion coefficient of Tg or less [CTE-2]: Expansion coefficient of Tg or more In the above measurement of the glass transition temperature, CTE-1 was 50.
The temperature in the temperature range of ８０80 ° C. and the value of CTE-2 in the temperature range of 200 to 230 ° C. were determined. [Intrusion Test] and [Void Failure] As shown in FIGS. 2A and 2B, the lower slide glass 12 is placed on the hot plate 11 and two 80 μm-thick glass plates are placed thereon. The polyimide films 13 and 13 are set at an interval of 1 cm, and the upper slide glass 14 is put on the polyimide films 13 and 13. The two slide films 12 and 14 and the two polyimide films 13 and 13 are 1 cm wide and 80 μm high. Gap 1
5 was formed. When the epoxy resin composition 16 was placed on the lower slide glass 12 and the hot plate 11 was set at 100 ° C., the time required for the composition 16 to penetrate and reach the gap 15 up to a distance of 20 mm into the gap 15 was measured. . [Observation of Void by Ultrasonic Flaw Detector] A 10 mm × 10 mm silicon chip having 400 bumps was subjected to BT.
After being mounted on a substrate and allowed to stand in an atmosphere of 23 ° C./60% RH for 2 hours, each composition was dropped on a piece of the device with a dispenser and sealed. After sealing and heat curing, use an ultrasonic flaw detector to form voids (internal voids).
Was detected. The evaluation was shown by the total area ratio of voids to the sealing area of the cured underfill material. [Defective rate of thermal shock resistance] An epoxy resin composition was uniformly applied on a copper frame, and a 0.6 mm-thick silicon wafer cut into 10 mm × 10 mm was placed on the resin.
A test specimen obtained by curing at 0 ° C. for 4 hours was −55 ° C. × 1
A heat cycle of 30 min.
After 0 cycles, those having cracks and peeling of the epoxy resin composition were regarded as defective, and the defective rate was measured (number of tests = 20).

[0042]

[Table 1]

[0043]

[Table 2]

Raw Materials Used (1) RE310: Bisphenol A epoxy resin (Nippon Kayaku Co., Ltd.) (2) RE304: Bisphenol F epoxy resin (Nippon Kayaku Co., Ltd.) (3) MH700: Methyltetrahydro Phthalic anhydride (manufactured by Nippon Rika Co., Ltd.) (4) Silica shown in Table 3 below (5) KBM403: γ-glycidoxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd.) (6) 2P4MZ: 2 -Phenyl-4-methylimidazole (manufactured by Shikoku Chemicals) (7) HX3741: a microencapsulated catalyst containing an imidazole compound (manufactured by Asahi Ciba Co., Ltd.)

[0045]

[Table 3] * SO32H: manufactured by Admatechs Co., Ltd.

[0046]

The underfill material for a flip-chip type semiconductor device according to the present invention is excellent in thin film penetration and storage stability, and a semiconductor device using this underfill material is very reliable. .

[Brief description of the drawings]

FIG. 1 is a schematic view illustrating an example of a flip-chip type semiconductor device.

FIG. 2 shows a test piece used in the penetration test, (A)
Is a side view, and (B) is a plan view.

[Description of Signs] 1 Organic substrate 2 Bump 3 Semiconductor chip 4 Underfill material 5 Fillet material 11 Hot plate 12 Lower slide glass 13 Polyimide film 14 Upper slide glass 15 Gap 16 Epoxy resin composition

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08K 7/18 C08K 7/18 9/00 9/00 H01L 21/56 H01L 21/56 E 21/60 311 21/60 311S 23/29 23/30 R 23/31 (72) Inventor Kazumasa Sumida 1-10 Hitomi, Matsuida-machi, Usui-gun, Gunma Prefecture 10 Silicone Electronic Materials Technology Laboratory, Shin-Etsu Chemical Co., Ltd.

Claims (3)

[Claims] (A) Liquid epoxy resin: 100 parts by weight (B) Spherical silica obtained by heating and burning polyorganosilsesquioxane spherical particles: 100 to 3
An underfill material for a flip-chip type semiconductor device, comprising: 00 parts by weight (C) a curing accelerator: 0.01 to 10 parts by weight. 2. The spherical silica as component (B) has a maximum particle size of 50 μm or less, an average particle size of 0.5 to 10 μm, and contains 0.005 to 0.1% by weight of carbon atoms on the surface. The underfill material according to claim 1, wherein 3. An inorganic filler other than the spherical silica as the component (B) is contained, and the content of the spherical silica as the component (B) is 60% by weight or more based on the whole inorganic filler including the component (B). The underfill material according to claim 1.