KR100479853B1 - Method for preparing epoxy resin composition for semiconductor encapsulant and the composition - Google Patents

Abstract

The present invention relates to a method for producing an epoxy resin composition for sealing semiconductor elements excellent in reliability and releasability with a mold, and more particularly, to (i) a phenol novolak in a reaction tank maintained at a temperature of 120 to 140 ° C. After completely melting the curing agent, 50 to 130 parts by weight of the biphenyl epoxy resin is gradually added per 200 parts by weight of the phenol novolac curing agent, and 5 to 20 parts by weight of low molecular weight per 200 parts by weight of the phenol novolac curing agent. Adding wax, melt-mixing for 20 to 60 minutes within the temperature range, and then quenching at low temperature to obtain a resin masterbatch; And (ii) melt kneading the resin masterbatch with an orthocresol novolak resin, a curing accelerator, a low stress agent and an inorganic filler to obtain a final resin composition. The epoxy resin composition prepared according to the method of the present invention has improved releasability with a mold while maintaining excellent adhesion, thereby reducing workability deterioration due to adhesion of a mold and an encapsulant during molding of a semiconductor device package. .

Description

Manufacturing method of epoxy resin composition for semiconductor element sealing, and its composition {METHOD FOR PREPARING EPOXY RESIN COMPOSITION FOR SEMICONDUCTOR ENCAPSULANT AND THE COMPOSITION}

The present invention relates to a method for producing an epoxy resin composition for sealing semiconductor elements with excellent reliability and releasability with a mold, and to a composition thereof. More specifically, a low viscosity biphenyl-based epoxy resin is combined with a phenol novolak-based curing agent and a low molecular weight wax. The present invention relates to a method for producing an epoxy resin composition for sealing semiconductor elements, and an epoxy resin composition produced by the above method, characterized in that the melt master batch is used together.

In recent years, the degree of integration of semiconductor devices has been improved day by day, and thus, the size of wirings, the size of devices, and multilayer wirings are rapidly progressing. On the other hand, packages that protect semiconductor devices from the external environment are accelerating their size and thickness from the viewpoint of high-density mounting on a printed board, that is, surface mounting. In addition, due to environmental problems, lead-containing Sn-Pb-based solder, which is used to fuse a semiconductor package during a semiconductor mounting process, is replaced with another material that does not contain lead, and as a result, the reflow temperature is 20 ° C. The degree has risen. This further increased the internal stresses received inside the package.

As described above, in a resin-sealed semiconductor device in which a large semiconductor device is sealed in a small and thin package, the frequency of failure such as package crack or corrosion of an aluminum pad may increase due to thermal stress caused by temperature and humidity changes in the external environment. . Therefore, as a solution of this, high reliability of the epoxy resin molding material for sealing has been raised, and in detail, methods for lowering the stress have been introduced, such as lowering the modulus of elasticity, lowering the coefficient of thermal expansion, and high purity for suppressing the occurrence of corrosion. The use of an epoxy resin or a curing agent or the application of an ion trapper reduces the impurity content, and the method of high filling the inorganic filler to reduce the moisture absorption.

For example, as a method of lowering the elastic modulus, modification by various rubber components (see Japanese Patent Application Laid-Open Nos. 63-1894 and 5-291436) is studied, and a silicone polymer having excellent thermal stability is blended and modified. Epoxy resin molding materials are widely adopted. In this method, the silicone oil is incompatible with the epoxy resin, which is the base resin of the molding material, and a curing agent, and thus fine particles are dispersed in the base resin, thereby achieving a low modulus while maintaining heat resistance. On the other hand, for low thermal expansion, the method of increasing the filling amount of the inorganic filler having a low coefficient of thermal expansion is best, but the low flowability and high elasticity of the epoxy resin molding material caused by the increase of the filling amount of the inorganic filler are a problem. In Korean Patent Publication No. 64-11355, a technique for incorporating a large amount of spherical fillers through the control of particle size distribution and particle size has been introduced.

However, even when high reliability is ensured by the above-described methods, the phenomenon that workability is degraded due to poor releasability with a mold is often a problem. In particular, in the case of a thin thin thin outline package (TSOP), the chip breakage is a serious problem due to poor releasability with the mold after molding. That is, when the low viscosity biphenyl-based epoxy resin is used in order to secure reliability, the adhesive force is excellent, but this greatly deteriorates the releasability with the mold, which is a work characteristic.

The present invention is to solve the problems of the prior art as described above, by dispersing the low molecular weight wax component in the low viscosity biphenyl epoxy resin fine and excellent adhesion with the biphenyl epoxy resin and the mold by the wax component An object of the present invention is to provide an epoxy resin composition for sealing semiconductor elements having mold release properties.

That is, one aspect of the present invention provides a method for preparing an epoxy resin composition for sealing a semiconductor device comprising the following steps:

(i) After completely melting the phenol novolak-based curing agent in a reaction tank maintained at 120 to 140 ° C, 50 to 130 parts by weight of biphenyl-based epoxy resin is gradually added per 200 parts by weight of the phenol novolak-based curing agent. 5 to 20 parts by weight of a low molecular weight wax per 200 parts by weight of the phenol novolac curing agent, followed by melt mixing for 20 to 60 minutes in the temperature range, and then quenching at low temperature to obtain a resin masterbatch. Doing; And

(ii) melt kneading the resin masterbatch with an orthocresol novolak resin, a curing accelerator, a low stress agent and an inorganic filler to obtain a final resin composition.

Another aspect of the present invention provides an epoxy resin composition for sealing a semiconductor device produced by the above method.

In order to improve the high temperature crack resistance of the epoxy resin composition for semiconductor element sealing, the adhesion between the resin and the chip and the resin and the lead frame should be improved. For this purpose, it is common to use a low viscosity biphenyl epoxy resin. Biphenyl-based epoxy resin has a very low viscosity compared to the conventional orocresol novolak resin, it is known that the adhesion strength is greatly improved due to excellent wettability with the surface of the chip and lead frame. In addition, due to the low curing density of the biphenyl-based epoxy resin, the resistance to impact is improved to have excellent crack resistance. However, when the biphenyl-based epoxy resin is used, the releasability with the mold worsens as the adhesive force is improved, and in particular, the chip breakage in the thin package cannot be avoided. The present inventors use a low-viscosity biphenyl epoxy resin as an epoxy resin, but before blending the resin with other components, first, melt mixing with a phenol novolac curing agent and a low molecular weight wax so that the wax component is contained in the resin component. By producing and using the masterbatch in the finely dispersed state, it was possible to secure good release property with the mold while maintaining the excellent adhesive strength which is an advantage of the biphenyl epoxy resin.

Hereinafter, the present invention will be described in more detail.

According to the present invention, the biphenyl epoxy resin is melt mastered together with the phenol novolac curing agent and low molecular weight wax as described above. The specific mixing method is as follows. First, the phenol novolak-based curing agent is completely melted in a reactor maintained at a constant temperature of 120 to 140 ° C, preferably 130 ° C, and then 50 to 130 parts by weight of biphenyl per 200 parts by weight of the phenol novolak-based curing agent. The epoxy resin is slowly added. Subsequently, 5-20 weight part of low molecular weight wax per 200 weight part of said phenol novolak-type hardening | curing agents is thrown into the said reaction tank. After the wax addition is completed, the melt melting master batch in the form of an amorphous mixture (hereinafter, referred to as a resin masterbatch or resin MMB) is melt-mixed for 20 to 60 minutes, preferably 30 minutes in the above temperature range, and then quenched at a low temperature. (called melt master batch).

The resin masterbatch thus prepared has a softening point of 70 to 75 ° C and a viscosity (150 ° C) of 1.2 to 1.3 poise. If the viscosity is 1.3 or higher, the fluidity of the final resin composition is affected, so care should be taken not to increase the viscosity. For this purpose, the temperature, the feed rate of the raw material, and the mixing time are appropriately controlled within the above range during the melt mixing process. It is very important to.

The biphenyl epoxy resin used in the present invention is a low viscosity biphenyl epoxy resin as mentioned above, and the viscosity measured at 150 ° C. using a CONE & PLATE viscometer is preferably 0.1 to 0.3. Is 0.2 poise.

The low molecular weight wax melt-mixed with the low viscosity biphenyl epoxy resin is a higher fatty acid or ester wax having a molecular weight of 300 to 400. In the meantime, the wax in the molecular weight range has high compatibility with the biphenyl epoxy resin, and It has been known to remain in the encapsulant even after molding without being separated, leading to a decrease in mold release properties. That is, the wax component is bleeded out to the surface of the package after molding to form a thin film on the surface of the package to ensure mold release property. A low molecular weight wax may be used as a release agent in an encapsulant including a biphenyl epoxy resin. In this case, due to the high compatibility between the wax and the resin, the wax component could not bleed out to the outside of the encapsulant, and as a result, a release property-improving effect could not be obtained. When wax amount is increased or high molecular weight (molecular weight 2000 or more) wax is used to secure mold release property, mold release property is secured, but adhesive strength is significantly deteriorated instead. However, in the present invention, the low molecular weight wax is pre-melted and mixed with a low viscosity biphenyl epoxy resin and a phenol novolak-based curing agent, and the master batch is usually used in epoxy resin compositions for semiconductor element sealing. By melt-kneading together with other components such as a curing accelerator, an inorganic filler, and other additives to prepare a final resin composition, it was possible to greatly improve mold release properties while maintaining excellent adhesive force during package molding. On the other hand, the phenol novolak-based curing agent used in the production of the resin MMB is not particularly limited, the phenol novolak resin having a hydroxyl equivalent of 100 ~ 200 can be used.

In the preparation of the epoxy resin composition for semiconductor element sealing of the present invention, the resin MMB (component 1) is used in an amount corresponding to 3.0 to 7.0% by weight of the total composition.

Moreover, in this invention, in addition to the said resin MMB, ortho cresol novolak resin (component 2) is used together as an epoxy resin component. The orthocresol novolak resin usable in the present invention is also not particularly limited in its kind, and an ordinary orthocresol novolak resin having an epoxy equivalent of 100 to 300 may be used. When using orthocresol novolak resin together with the said resin MMB, it is preferable that the content is 5-12 weight% with respect to the whole resin composition.

As the curing accelerator (component 3) usable in the epoxy resin composition of the present invention, tertiary amines such as benzyldimethylamine, triethanolamine, triethylenediamine, dimethylaminoethanol and tri (dimethylaminomethyl) phenol; Imidazoles such as 2-methylimidazole and 2-phenylimidazole; Organic phosphines such as triphenylphosphine, diphenylphosphine and phenylphosphine; And tetraphenylboron salts such as tetraphenylphosphonium tetraphenylborate, triphenylphosphine tetraphenylborate and the like, and one of these may be used alone or two or more thereof may be used in combination. It is preferable that the usage-amount of a hardening accelerator is 0.1 to 0.3 weight% with respect to the whole epoxy resin composition. If the content of the curing accelerator is less than 0.1% by weight, the curing rate is slowed to decrease the productivity. If the content of the curing accelerator is more than 0.3% by weight, it is not only difficult to secure moldability but also poor storage stability of the resin composition.

In the epoxy resin composition of the present invention, as the low stress agent (component 4), a silicone polymer having excellent heat resistance is used, and preferably a silicone oil having an epoxy functional group, a silicone oil having an amine functional group, and a silicone oil having a carboxyl functional group. At least one selected from the group consisting of is used within the range of 0.4 to 1.5% by weight based on the total composition. When the silicone oil is used in excess of 1.5% by weight, surface contamination is likely to occur and the resin bleed may be prolonged, and when used at less than 0.4% by weight, sufficient low modulus may not be obtained.

In the epoxy resin composition of the present invention, as the inorganic filler (component 5), it is preferable to use molten or synthetic silica having an average particle size of 0.1 to 35.0 µm, and the filling amount is used to be 80% by weight or more based on the total composition. When the inorganic filler is used in an amount of less than 80% by weight, sufficient strength and low thermal expansion cannot be realized, and the penetration of moisture becomes easy, which is fatal to reliability characteristics. On the other hand, the upper limit of the filling amount of the inorganic filler should be selected in consideration of the moldability, preferably 90% by weight or less.

In addition to the components of (1) to (5) described above, the epoxy resin composition of the present invention includes a flame retardant such as bromo epoxy; Flame retardant aids such as antimony trioxide, alumina hydroxide and antimony pentoxide; Coloring agents such as carbon black and organic and inorganic dyes; And coupling agents such as epoxy silane, amino silane, alkyl silane and the like can be further added as necessary within the range not contrary to the object of the present invention.

The preparation of the epoxy resin composition of the present invention does not require a separate device or method, and in general, each component is uniformly mixed firstly using a Henschel mixer or a Rödige mixer in a predetermined amount, and then using a roll mill or a kneader. Melt kneading is followed by cooling and grinding to obtain the final powder product.

As a method of sealing a semiconductor device using the epoxy resin composition prepared in the present invention, a low pressure transfer molding method is most common, but it can also be molded by an injection molding method or a casting method.

Hereinafter, the present invention will be described in more detail with reference to examples, but these examples are for illustrative purposes only and should not be construed as limiting the present invention. In the following Examples and Comparative Examples, the physical property evaluation method is as follows.

[Property evaluation method]

1) Spiral Flow

Mold is manufactured based on EMMI standard and flow length is evaluated under molding temperature of 175 ℃ and molding pressure of 70kgf / cm ² .

2) Glass transition temperature (Tg)

    Assessed by TMA (Thermomechanical Analyser)

3) coefficient of thermal expansion (α)

    Rated according to ASTM D696

4) adhesion

    Evaluated with UTM (Universal Test Machine)

5) dysplasia

   After using the melamine resin, the mold release force test mold was cleaned by three moldings at 175 ° C for 300 seconds, and then each epoxy resin composition according to the Examples and Comparative Examples was molded twice at 120 ° C for 120 seconds. A pull gauge was used to measure the release force with the mold. All release force values listed in Table 2 below are averages obtained from 40 or more tests.

6) Reliability (Crack Resistance)

   After molding for 45 seconds at 180 ℃ using an APIC YAMADA (Multi Plunger System) molding machine, after curing for 4 hours at 175 ℃ to produce a TSOP-type semiconductor device. After preconditioning the semiconductor device, IR reflow was performed at 260 ° C., and then cracking was evaluated using a non-destructive tester, SAT (Scanning Acoustic Tomograph).

    ※ Preconditioning Condition

       After drying the TSOP-type semiconductor device molded with each epoxy resin composition according to the Examples and Comparative Examples for 24 hours at 125 ℃, and then subjected to a thermal shock test of 5 cycles and left for another 192 hours under 30 ℃ / 60% relative humidity conditions Then, three passes of IR reflow for 10 seconds at 260 ° C were used to evaluate the presence of package cracks under preconditioning conditions.

7) formability

   Visually measuring the number of voids in the package (visual inspection)

Example  1 and 2 and Comparative example  1 ~ 2

First, the phenol novolak-based curing agent (HF-1, MEWEI KASAI Co., Ltd.) is completely melted in a reaction tank at which the internal temperature is constantly maintained at 130 ° C., and then 100 parts by weight of biphenyl is used per 200 parts by weight of the phenol novolak-based curing agent. The epoxy resin (YX-4000H, YUKA SHELL Co., Ltd.) was slowly added. Subsequently, 10 parts by weight of a low molecular weight wax (CAR-2442, Kahl & Co.) was added per 200 parts by weight of the phenol novolac curing agent. After the addition was completed, the temperature in the reaction vessel was heated to 130 ℃ and mixed for 30 minutes, and then quenched at 10 ~ 15 ℃ to obtain a resin MMB (melt master batch).

As shown in Table 1 below, each component including the resin MMB was weighed, and then uniformly mixed using a Henschel mixer to prepare a powder-based primary composition, followed by mixing at 100 ° C. using a mixing 2-roll mill. After melt-kneading for a minute, the final epoxy resin composition was obtained by cooling and pulverizing.

Basic properties, releasability, reliability, and moldability were evaluated by the above-described method for the epoxy resin composition, and the results are shown in Table 2 below. Table 3 shows a separate summary of the release force according to the number of mold operations, it is also shown graphically in FIG.

From the results of Tables 2 and 3 above, it can be seen that the epoxy resin composition according to the embodiment maintains equivalent to or better adhesion and reliability than the comparative example, while the releasability with the mold is greatly improved. In addition, it was confirmed that the number of voids was also reduced, and it was found that the moldability of the final resin composition could also be improved by melt-mixing the resin with wax and using a master batch according to the method of the present invention.

As described in detail above, the epoxy resin composition prepared according to the method of the present invention greatly improved the releasability with the mold while maintaining excellent adhesion, thereby reducing workability due to adhesion of the mold and the encapsulant during molding of the semiconductor device package. Can be reduced.

1 is a graph showing a change in the release force according to the number of mold operations of the epoxy resin composition according to the comparative example and the embodiment.

Claims (5)

Method for producing an epoxy resin composition for sealing a semiconductor device comprising the following steps: (i) After completely melting the phenol novolak-based curing agent in a reaction tank maintained at 120 to 140 ° C, 50 to 130 parts by weight of biphenyl-based epoxy resin is gradually added per 200 parts by weight of the phenol novolak-based curing agent. 5 to 20 parts by weight of a low molecular weight wax per 200 parts by weight of the phenol novolac curing agent, followed by melt mixing for 2 to 60 minutes within the temperature range, followed by quenching at low temperature to quench (quench) the resin masterbatch. Obtaining; And (ii) melt kneading the resin masterbatch with an orthocresol novolak resin, a curing accelerator, a low stress agent and an inorganic filler to obtain a final resin composition. The method according to claim 1, wherein the biphenyl epoxy resin is a low viscosity resin having a viscosity (150 ° C) of 0.1 to 0.3 poise. The method according to claim 1, wherein the softening point of the resin masterbatch is 70 to 75 ° C, and the viscosity (150 ° C) is 1.2 to 1.3 poise. An epoxy resin composition for sealing a semiconductor device manufactured according to any one of claims 1 to 3. The method of claim 4, wherein (1) 3.0 to 7.0 wt% resin masterbatch; (2) 5-12% by weight of orthocresol novolak resin; (3) 0.1 to 0.3 wt% of a curing accelerator; (4) 0.4 to 1.5 weight percent of a low stress agent; And (5) 80 ~ 90 wt% inorganic filler Epoxy resin composition for sealing semiconductor elements comprising a.