JP2002338230A - Silica particles and resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce spherical silica excellent in adhesiveness to a resin and ensuring high fluidity and low hygroscopicity of the resin when the resin is blended with the silica. SOLUTION: The spherical silica particles have 6 μmol/g to 5 mmol/g silanol groups and the volume of pores of <=10 nm pore diameter in the particles occupies >=50% of the total pore volume. The spherical silica particles are treated with an adequate amount of a silane coupling agent and a resin composition containing the treated spherical silica particles as a filler is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to spherical silica particles used as a filler for a resin composition such as a semiconductor encapsulant and a resin composition containing the same.

[0002]

2. Description of the Related Art As a method for encapsulating semiconductor elements such as ICs and LSIs, it has been a long time since a method of encapsulating a resin with an epoxy resin composition has been adopted as a method suitable for mass production at low cost. Reliability has been improved by improving the curing catalyst, the filler and the like. However, on the other hand, semiconductor packages have become thinner in recent market trends of miniaturization, weight reduction, and high performance of electronic devices, and the thickness of the resin composition occupying in the package has been further reduced. Further improvement in the strength and toughness of the cured resin is required.

[0003] In a conventional resin composition for semiconductor encapsulation, in order to increase the thermal shock strength, a method is employed in which silica particles having a coefficient of thermal expansion close to that of a silicon chip are filled as much as possible as a sealing resin filler. The filling ratio reaches 60-90% by weight of the whole resin composition. It is now common sense that it is effective to make the shape of the silica particles spherical to increase the filling rate, and to add and use a silane coupling agent to increase the strength of the cured product. (For example, Japanese Patent Laid-Open No.
5). However, the spherical silica filler originally had no shape as a filler and did not have the strength of the cured product, and was usually fired at a high temperature just before melting or melting in the manufacturing process. Silanol groups on the surface have disappeared by the dehydration condensation reaction until the concentration becomes approximately 2 μmol / g or less, and there is almost no reaction site with the silane coupling agent. There was a problem that the adhesiveness was not sufficiently improved and the moisture resistance was poor.

On the other hand, as an example of silica having abundant silanol groups, there is a so-called silica gel produced by a wet method such as neutralization of sodium silicate with sulfuric acid. Due to its formation mechanism that silica particles aggregate to form secondary particles, the resulting silica gel becomes a porous body with extremely high oil absorption and hygroscopicity, and is remarkable when kneaded with resin as a filler. There has been a problem that a decrease in fluidity and an increase in hygroscopicity occur. In addition, in practice, even when a silane coupling agent is used in combination, the strength of the cured resin hardly increases, and there is a problem that moisture absorption remains.

[0005]

The conventional silica filler used in the resin composition for semiconductor encapsulation has almost no silanol groups to react with the silane coupling agent. Even if added, the adhesion between the silica filler and the resin was not sufficiently improved. On the other hand, silica gel having many silanol groups has a problem of reduced fluidity of the resin and hygroscopicity.

[0006]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, they have a highly reactive isolated silanol of at least 6 μmol / g and also impair the fluidity of the resin composition. When silica having no large pores is used as a resin filler together with a silane coupling agent, the fluidity of the resin composition is high, and the strength of the cured product is increased. I knew you were there.

In general, in the conventional silica filler production technology, in consideration of the strength and the like of the silica particles, sintering proceeds at a high temperature of 1200 ° C. or more until the silanol group becomes 2 μmol / g or less. . At this time, irrespective of the original method of producing silica, the pores are sealed, so that the pores hardly have a pore volume, and even when kneaded with a resin, the fluidity is not adversely affected. However, since there is almost no silanol group to be reacted with the silane coupling agent, when mixed with the resin and cured, the interface between the silica and the resin is easily separated, and sufficient strength cannot be obtained.

On the other hand, the present inventors have increased the reactivity between silica and a silane coupling agent by having only a special silanol group on the silica surface, and improve the adhesion between the filler and the resin. As a result of examining the relationship between the firing temperature of silica and the concentration of silanol groups, it was found that firing specific silica at a specific temperature resulted in 3400 cm
Silica rich in isolated silanol groups, which has almost no hygroscopic silanol with an infrared absorption peak near -1 and has an absorption peak near 3740 cm-1 with high reactivity with silane coupling agents , And found that when this was used in combination with a silane coupling agent, the strength of the cured adhesive was improved. Furthermore, even among such silicas, by using a specific silica having only a small pore diameter such that the resin does not enter,
The present invention was completed by finding that an excellent resin composition having high fluidity as a resin composition and at the same time having high strength of a cured product can be realized.

Hereinafter, the present invention will be described in detail. The silanol group in the silica filler of the present invention can be easily adjusted by the calcination temperature of the silica, and the silica before calcination can be produced by a known method. Specifically, an aqueous solution of an alkali metal silicate such as water glass or sodium silicate is mixed with an inorganic acid such as sulfuric acid, nitric acid, phosphoric acid, or hydrochloric acid, or an ammonium salt of an inorganic acid such as ammonium sulfate, ammonium nitrate, ammonium phosphate, or ammonium chloride. It can be produced by a method of performing neutralization polymerization with an aqueous solution or a method of hydrolyzing and condensing an alkyl silicate such as methyl silicate, ethyl silicate or isopropyl silicate in the presence of an acid such as hydrochloric acid or acetic acid or a base such as aqueous ammonia. However, when it is used as a filler for an IC encapsulant epoxy resin, it is preferable to use sodium silicate, which causes corrosion of wiring, or an alkyl silicate, which has a low content of α-ray emitting nuclide, which causes loss of memory, as a raw material. Even when an aqueous solution of a metal silicate is used as a raw material, it is possible to reduce impurities in the completed silica by repeatedly washing silica gel and purifying the raw material solution by ion exchange or the like, but it is complicated and costly. It becomes a manufacturing method.

Of these methods, the most suitable is a method of hydrolyzing and condensing an alkyl silicate. Since the original pore diameter is small, most of the pores can be converted into resin fluidity only by firing at an appropriate temperature. Since the pore diameter is 10 nm or less, which does not affect the viscosity, the fluidity of the resin composition is not impaired even if an appropriate amount of silanol groups is left without completely melting the silica. Particularly excellent is a case where spherical silica particles are synthesized from the beginning by a method using an alkyl silicate as a raw material by a sol-gel method or an emulsion method, in which case the pore distribution and the amount of silanol are more easily controlled.

In the method of neutralizing an alkali metal silicate, a porous silica gel having a large pore diameter is basically produced. If the amount is too large, the fluidity of the resin is impaired, but at high temperatures enough to melt, the silanol groups are lost. In this case, silanol can be generated on the silica surface by a method such as heating at a temperature high enough to melt once to seal, and then causing hydrolysis condensation of the alkyl silicate on the surface again. Alternatively, there is a method in which hydrolytic condensation of alkyl silicate is caused on the surface of a conventional fused spherical silica as a raw material.

The preferred range of the pore distribution which does not impair the fluidity of the resin composition is as follows:
The total volume of the pores of 0 nm or less is 50% or more, more preferably 70% or more. Since the preferred pore size is 10 nm or less that does not increase the resin viscosity, the mode size of the pore size is preferably 10 nm or less. When the lower limit is 0, the mode diameter is 0 because there is no pore.
A pore size larger than 10 nm and especially a mode diameter between 2 nm and 8 nm is preferable as a pore size that can be easily realized and does not affect the resin viscosity.

Since the pore volume corresponds to the sum of the volumes of all the pores, the smaller the pore diameter, the smaller the pore volume. Preferred pore volume values are greater than 0 and 0.3
cm3 / g or less, more preferably 0.001 cm3 / g or more and 0.05 cm3 / g or less.

The preferred average particle size of the silica is as follows:
If it is too large, it adversely affects the fluidity and moldability of the resin mixture, and if it is too small, it causes an increase in viscosity and thixotropic properties of the resin mixture, which also has an adverse effect on fluidity and moldability. The average particle diameter is particularly preferably 0.1 μm to 10 μm.

If the amount of the isolated silanol in the silica filler is too small, a substantially remarkable effect cannot be obtained if the amount is too small. Therefore, the amount is preferably 6 μmol / g or more, more preferably 10 μmol / g or more. As the amount of silanol groups increases, the number of functional groups that can react with the silane coupling agent increases, so the strength of the cured adhesive resin increases.However, the silane coupling agent has a silica surface called the minimum coating area. Therefore, silanol groups that cannot be reacted even if the amount is too large remain. Therefore, the preferable upper limit of the amount of isolated silanol is 5 mmol.
/ g or less, more preferably 1 mmol / g or less

Silanol groups contained in silica exist in various forms, and their infrared absorption spectra are assigned as shown in Table 1.

[0017]

[Table 1]

Of these, silanol groups derived from surface-adsorbed water are silanol groups generated by the coordination of water molecules adsorbed on silica, and exhibit reversible adsorption and desorption of water molecules, exhibiting hygroscopicity. When this silica is added to the semiconductor encapsulant, it causes a reduction in the moisture resistance reliability.

Since the surface adsorbed water is strongly bonded to the silanol group by hydrogen bonding, it does not volatilize at the boiling point of water,
It adheres to high temperature of ℃. When a silane coupling agent is applied to silica having silanol derived from adsorbed water with an infrared absorption peak at 3400 cm- ¹ , the silane coupling agent reacts exclusively with surface adsorbed water and condenses only near silica. Although a slight improvement in strength may be observed due to the crosslinking effect between the silane coupling agents,
It does not cause a chemical bond between the coupling agent and the silica. Further, adjacent silanol groups are too close to each other and cannot react with the coupling agent at the same time, and the effect of the coupling agent is not sufficiently exhibited.

On the other hand, isolated silanol groups have high reactivity,
Because there is no silanol group nearby, there is enough space for the coupling agent to fit in. When the isolated silanol and the silane coupling agent react directly, a direct chemical bond of resin-coupling agent-silica is generated and strong adhesion occurs. Will bring sex. Therefore, the silanol group of silica is preferably an isolated silanol group, and among the absorption peaks of various silanols appearing in at least the infrared absorption spectrum, the absorption peak of the isolated silanol group having an absorption wavelength near 3740 cm-1 is observed as the maximum peak. 3400 cm derived from adsorbed water or the like is more preferable.
-1 is hardly observed. Specifically, the absorption area around 3740 cm-1 is 5% of the absorption peak around 3400 cm-1 in the peak area when the abscissa is taken as the wave number cm-1. Most preferably, it is twice or more.

As a method for quantifying the silanol group, a method for spectroscopically measuring the silanol in Table 1 by infrared absorption is preferably used. Specifically, the FT-IR, the FT-IR,
This is a method in which the absorption amount of a specific wavelength by silanol is measured by an infrared absorption spectrometer such as FT-NIR, and the absolute value of the silanol amount is determined in combination with an absolute measurement method such as a titration method or a scoop loss method. Among them, the IR diffuse reflection method can be used particularly preferably as a method capable of directly measuring powder and more selectively measuring the composition of the powder surface.

Regarding a calcination apparatus for obtaining silica having a preferable silanol, any apparatus can be used as long as the apparatus can be maintained at a temperature lower than 1050 ° C. for several hours, preferably 1 hour to 8 hours, and the heat source is an electric joule. Heat or combustion heat of oil or gas may be used.

When the obtained silica is applied to a resin composition, known silane coupling agents can be used. When silica is used as the filler for the epoxy resin, the functional group of the silane coupling agent is preferably an epoxy-based, amino-based, chloropropyl-based, or mercapto-based, and particularly preferably an epoxy-based or amino-based. Preferred silane coupling agents such as vinyl-based polyolefin-based resins and methacryl-based acrylic-based resins are determined according to a standard method.

The method of treatment with a coupling agent includes an integral blending method in which a silane coupling agent is simultaneously added and mixed when a resin and silica are mixed, and a pretreatment method in which silica is treated before mixing with a resin. Can choose any method. In order to easily obtain the effect of the coupling treatment, the pretreatment method is more preferable. The treatment amount may be equal to or more than the equivalent of the silanol group, but if added in excess, there is a possibility of aggregation, so the amount is preferably 1 to 5 times, preferably 1 to 3 times the equivalent of the silanol group.

The resin used in the present invention is an epoxy resin, a polyolefin resin, an acrylic resin, a polyester resin,
Any material such as a silicone resin can be preferably used.
Specifically, for example, a bisphenol-type epoxy compound, a biphenyl-type epoxy compound, a stilbene-type epoxy compound, a phenol novolak-type epoxy resin, a cresol novolak-type epoxy resin, a triphenolmethane-type epoxy compound, an alkyl-modified triphenolmethane-type epoxy resin, a polyethylene resin, Polypropylene resin,
Vinyl chloride resin, acrylic resin, methacrylic resin, PE
T resin, nylon resin, polyimide resin, silicone resin and the like can be mentioned, or those obtained by brominating these for flame retardation of the resin can also be used. These may be used singly or as a mixture, and in the case of mixing, the mixing amount of each component is arbitrary, and the optimum mixing ratio is determined depending on the purpose. When using an epoxy resin, a monoepoxy compound may be appropriately used in combination. Specific examples of the monoepoxy compound include styrene oxide,
Examples include cyclohexene oxide, methyl glycidyl ether and other alkyl glycidyl ethers.

As the curing agent for the epoxy resin, one corresponding to the epoxy resin is used. For example, an amine curing agent, an acid anhydride curing agent, a phenol novolak type curing agent and the like are used. Is preferable in terms of moldability and moisture resistance of the composition. Specific examples of the phenol novolak type curing agent include a phenol novolak resin, a cresol novolak resin, and a dicyclopentadiene-modified phenol resin. The compounding amount in the resin composition can be arbitrarily determined so that the strength of the cured product is maximized. As a curing accelerator, at least one kind of an imidazole compound, an undecene compound, a phosphine compound such as triphenylphosphine, and a tertiary amine is used by a conventional method. The amount of the curing accelerator used is not particularly limited, and a normal amount may be used.

The amount of silica to be mixed should be determined by comprehensively judging the combination with the resin to be used, but in general, the larger the amount of silica, the lower the coefficient of thermal expansion of the cured product. Since it is closer to a semiconductor silicon chip than to a semiconductor silicon chip, it is preferable that the number is larger in a semiconductor sealing application. Therefore, it is preferable that the weight accounts for 30% or more of the entire resin composition,
More preferably it is between 60% and 95%. For non-semiconductor applications, use an appropriate amount as needed. In addition to the silica, other fillers such as crushed silica, magnesium hydroxide, and calcium carbonate may be blended.

In general, resin compositions include, in addition to silica, flame retardants, low stress agents, waxes, release agents such as fatty acids such as stearic acid and metal salts thereof, pigments such as carbon black, dyes, oxidants, and the like. It is known that an inhibitor, an ion scavenger, and other additives can be compounded, but the amount of these additives can be a normal amount as long as the effects of the present invention are not impaired. .

In order to produce the resin composition of the present invention as a molding material, each component and other additives are sufficiently mixed by a mixer or the like, and then kneaded by a three-roll mill, a hot roll or a kneader. And a molding material. When the molding material after kneading is solid at room temperature, it can be pulverized into a powdery sealing material, and when it is liquid, it can be used by filling it into an arbitrary container such as a syringe or a pot.
These molding materials can be used to coat electrical or electronic components,
In addition to protection, insulation, sealing, and the like of an integrated circuit and the like, the present invention can be applied as any member such as a mechanical component and a structural material.

[0030]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. [Example 1] Dodecylbenzene 90k in a 200L reactor
g, emulsifier (Tetraglyn 1-O manufactured by Nikko Chemicals Co., Ltd.)
0.8 kg, 30 kg of pure water and 0.1 kg of 25% aqueous ammonia were charged, and the liquid temperature was maintained at 60 ° C. and 100 rp.
m while stirring with tetramethoxysilane (Colcoat Co., Ltd.)
35 kg of methyl silicate 39) was supplied within 5 minutes. Thereafter, the temperature was maintained at 60 ° C. for 1 hour, and then heated to 150 ° C. Then, the reaction solution was separated by filtration, washed with acetone, and calcined at 600 ° C. for 4 hours to obtain a white powder. Observation of this powder with a scanning electron microscope revealed that each powder had an independent spherical shape.

When the infrared absorption spectrum of this powder was measured by the FT-IR diffuse reflection method, the chart shown in FIG. 2 was obtained. In this spectrum, the highest peak in the absorption spectrum by silanol was a peak based on isolated silanol at 3740 cm @ -1. As the absolute amount of the isolated silanol, the amount of the reduced trimethoxysilane was measured by gas chromatography after 24 hours from the introduction into a 10% toluene solution of trimethoxysilane, and the reduced amount of the isolated silanol group reacted with an equimolar amount of the isolated silanol group. As a result, the amount of silanol groups was determined to be 1.4 mmol / g. Next, the pore distribution of the silica was measured with a nitrogen adsorption type pore distribution meter, and the result was as shown in FIG. The volume of pores having a pore diameter of 10 nm or less was 96.8% of the total pore volume.

1 part by weight of γ-glycidoxypropyltrimethoxysilane was partially hydrolyzed with 100 parts by weight of this silica until it became a uniform liquid with an equal weight of pure water. After stirring for further 5 minutes, the mixture was dried at 150 ° C. for 24 hours and used as silica treated with a coupling agent.
No aggregation or discoloration was observed in the treated silica.

The silica treated with the coupling agent thus obtained is mixed with an epoxy resin mixture (bisphenol A type epoxy resin (oiled shell epoxy epicoat 828)) / acid anhydride curing agent (Nippon Rika Chemicals MT-500) / amine curing catalyst (DMP-30) was mixed at a weight ratio of 100/80 / 0.1.) 30 parts by weight, 70 parts by weight, and an epoxy resin composition having a silica content of 70% by weight Was prepared. The viscosity of this epoxy resin composition was measured with an E-type viscometer and found to be 40 Pa · s at 35 ° C.

The epoxy resin composition was placed in a mold and placed in a mold.
Heat-cured at 0 ° C for 2 hours and at 140 ° C for 4 hours to produce a cured product, and the head speed was 2 m according to JIS K-6911.
The bending strength was measured at m / min. As a result, the average value of n = 5 was 203 MPa.

[Example 2] Silica was produced and evaluated in the same manner as in Example 1 except that the sintering temperature was 800 ° C. No aggregation or discoloration was observed in the silica that had been treated with the coupling agent. Table 2 shows the amount of silanol groups of the silica and the results of various evaluations.

Example 3 Silica was produced and evaluated in the same manner as in Example 1 except that the firing temperature was 980 ° C. No aggregation or discoloration was observed in the silica that had been treated with the coupling agent. Table 2 shows the amount of silanol groups of this silica and the results of various evaluations. Example 4 Production and evaluation of silica were performed in the same manner as in Example 1 except that the silane coupling agent treatment was not performed. Table 2 shows the amount of silanol of this silica and the results of various evaluations.

[Comparative Example 1] Silica was produced in the same manner as in Example 1, and evaluation was performed at a firing temperature of 1400 ° C. No discoloration was observed in the silica that had been treated with the coupling agent, but since it was aggregated into granules of about 1 mm in total, it was used after crushing with a ball mill for 12 hours. Table 2 shows the amount of silanol groups of the silica and the results of various evaluations.
3740cm-1, 3400cm-1 by IR measurement before coupling treatment
In both cases, no IR absorption peak was observed, and in the same reaction with trimethoxysilane as in Example 1, no reaction was observed within an error range, so the silanol amount was set to 0.

[Comparative Example 2] FIG. 1 shows the result of measuring the pore distribution after baking at 600 ° C. for 4 hours using commercially available spherical silica gel (Asahi Glass Sunsphere H53). Pore size
The pore volume of 10 nm or less was 29.0% of the total pore volume. Then, evaluation was performed in the same manner as in Example 1. No aggregation or discoloration was observed in the silica that had been treated with the coupling agent. Table 2 shows the results. The viscosity of the epoxy resin composition could not be measured with a viscometer because the resin component became too hard due to oil absorption by silica and became solid. As shown in FIG. 3, there was no peak at 3740 cm-1 in the IR measurement, and a broad absorption peak near 3400 cm-1 derived from surface adsorbed water was largely observed. From the same reaction with trimethoxysilane as in Example 1, the amount of silanol was determined to be 8.2 mmol / g.

[0039]

[Table 2]

[0040]

As is clear from the results of the examples, the silica in the present invention has an active silanol group of 6 μmol / g or more, and the silica has good reactivity with the silane coupling agent. The epoxy resin composition filled with the silane-coupled silica filler has excellent fluidity and mechanical strength.

[Brief description of the drawings]

Fig. 1 Pore distribution

FIG. 2 is an IR measurement chart of Example 1.

FIG. 3 is an IR measurement chart of Comparative Example 2.

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Claims (3)

[Claims] (1) The volume of pores having a silanol group of 6 μmol / g or more and 5 mmol / g or less and having a pore diameter of 10 nm or less is 50% of the total pore volume.
% Silica particles. 2. In the infrared absorption spectrum of the spherical silica particles, there is substantially no infrared absorption peak near 3400 cm @ -1 derived from adsorbed water and the like, and the infrared absorption peak derived from an isolated silanol group is not present.
2. The spherical silica particles according to claim 1, wherein the infrared absorption peak near 740 cm @ -1 is the largest among the infrared absorption peaks derived from silanol groups. 3. A resin composition comprising a filler obtained by subjecting the spherical silica particles according to claim 1 or 2 to an appropriate amount of a silane coupling agent treatment.