JPH1149933A - Epoxy resin molding material and semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide highly reliable semiconductor sealing epoxy resin molding materials with retarded reaction during storage at normal room temperatures and the hardly lowered flowability at the time of molding during storage at normal room temperatures and excellent in moldability, and soldering resistance as well. SOLUTION: In an epoxy resin molding material to be obtained by kneading a composition comprising, as the essential components, an epoxy resin, a phenolic resin curing agent, an curing accelerator and an inorganic filler under heating, the glass transition starting temperature of the molding material prior to mold-curing is not lower than 10 deg.C and the glass transition completing temperature is not higher than 50 deg.C and particularly, the epoxy resin is at least one member selected from the group consisting of crystalline epoxy resins having a melting point of 50-150 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an epoxy resin molding material for semiconductor encapsulation which is excellent in storage stability at room temperature, and further excellent in moldability, soldering resistance after moisture absorption and temperature cycle resistance. And a semiconductor device using the same.

[0002]

2. Description of the Related Art In recent years, in the market trend of miniaturization, weight reduction, and high performance of electronic devices, semiconductor integration has been progressing year by year, and surface mounting of semiconductor packages has been promoted. Demands on anti-stop materials are becoming more stringent. In particular, in the current situation where surface mounting of semiconductor packages is becoming common, a semiconductor package that has absorbed moisture is exposed to a high temperature during soldering, and cracks occur in the package due to the explosive stress of vaporized water vapor, or the semiconductor element is damaged. And the occurrence of peeling at the interface between the lead frame and the semiconductor encapsulating material causes defects that greatly impair electrical reliability. Prevention of these defects, that is, improvement of solder resistance, has become a major issue. In order to improve the solder resistance, the semiconductor encapsulating material contains a large amount of an inorganic filler to reduce the moisture absorption of the semiconductor package.
Low thermal expansion and high strength have been achieved. For this reason, low-viscosity epoxy resins and crystalline epoxy resins that are crystalline at room temperature but exhibit extremely low viscosity above the melting point are used. A method for preventing a decrease in fluidity during molding of a molding material (hereinafter referred to as molding material) is generally adopted.

However, a molding material using a low-viscosity epoxy resin or a crystalline epoxy resin causes a reaction to proceed gradually not only at the time of molding but also at ordinary temperature, and the viscosity increases with time. For this reason, the value of the spiral flow, which is an index indicating the fluidity during molding of the molding material, also decreases with time. In an extreme case, the value may be reduced to about half of the initial value even when left at room temperature for 24 hours. When the fluidity of the molding material is reduced when sealing the semiconductor element, the semiconductor element is pushed up and exposed on the package surface, so-called chip shift occurs, or the circuit of the semiconductor element is connected to the lead frame. A so-called gold wire deformation in which the gold wire is deformed or cut may occur, or a molding material may not be sufficiently filled in the mold, or a molding defect such as a so-called unfilling may occur. Generally, this molding material is stored at a low temperature of 0 to 10 ° C. until it is used in order to prevent the progress of the reaction at room temperature.
However, when used for molding semiconductor packages,
At present, the molding material is left at room temperature where the molding machine is installed until the end of use. Therefore, if the molding material is reduced in fluidity while being left at room temperature for several days, even if there is no problem in moldability in the early stage of use, the fluidity will be reduced after several days, Insufficient molding will occur frequently. For this reason, there has been a demand for the development of a molding material that does not decrease in fluidity during molding due to being left at room temperature, that is, has excellent storage stability at room temperature, excellent fluidity during molding, and excellent soldering resistance.

[0004]

SUMMARY OF THE INVENTION The present invention provides an epoxy resin molding compound for semiconductor encapsulation which has excellent storage stability at room temperature, excellent filling property of a thin semiconductor package, and excellent solder resistance, and a semiconductor device using the same. Things.

[0005]

According to the present invention, a composition comprising (A) an epoxy resin, (B) a phenolic resin curing agent, (C) a curing accelerator, and (D) an inorganic filler is heated. In the epoxy resin molding material obtained by kneading,
The glass transition start temperature of the molding material before molding and curing is 10 ° C.
Above, and the glass transition end temperature is 50 ° C. or less,
Particularly, the epoxy resin is represented by the general formulas (1) to (5),
The epoxy resin molding material for semiconductor encapsulation is at least one selected from the group consisting of crystalline epoxy resins having a melting point of 50 to 150 ° C.

Embedded image

[0006]

Embedded image

[0007]

Embedded image

[0008]

Embedded image

[0009]

Embedded image (R in the formulas (1) to (4) represents a hydrogen atom, a halogen atom, or an alkyl group having 1 to 12 carbon atoms, and may be the same or different from each other. In the formula (5), R is
It represents a halogen atom or an alkyl group having 1 to 12 carbon atoms, which may be the same or different. In the formula (5), l is a positive integer of 1 to 10, and m is 0 or 1.
And n is a positive integer of 0 or 1-4. )

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The epoxy resin used in the present invention refers to all monomers, oligomers and polymers having an epoxy group, such as bisphenol A type epoxy resin, phenol novolak type epoxy resin, orthocresol novolak type epoxy resin, Naphthol novolak type epoxy resin, triphenolmethane type epoxy resin, dicyclopentadiene modified phenol type epoxy resin, phenol aralkyl type epoxy resin, terpene modified phenol type epoxy resin, biphenyl type epoxy resin represented by general formula (1), general formula Hydroquinone type epoxy resin represented by (2), stilbene type epoxy resin represented by general formula (3), bisphenol F type epoxy resin represented by general formula (4), aralkyl modified represented by general formula (5) Phenyl type epoxy resin and the like, but not limited thereto. These epoxy resins may be used alone or as a mixture. Increase the amount of the inorganic filler in the molding material for the purpose of improving the soldering resistance of the semiconductor package, and achieve low moisture absorption, low thermal expansion, and high strength of the cured product of the molding material. In this case, it is particularly preferable to use, as the epoxy resin, a crystalline epoxy resin represented by any of the general formulas (1) to (5), which exhibits crystallinity at room temperature and becomes a liquid having a very low viscosity when the melting point is exceeded. Further, the melting point of these crystalline epoxy resins is preferably from 50 to 150 ° C. If the melting point is less than 50 ° C., fusion tends to occur in the manufacturing process, and workability is significantly reduced. On the other hand, when the melting point exceeds 150 ° C., the molding material is not sufficiently melted in the production step of heating and kneading, so that the produced molding material is not uniform, which is not preferable. The melting point of the crystalline epoxy resin is determined by using a differential scanning calorimeter [SSC / 5200 manufactured by Seiko Denshi Co., Ltd.] at the apex of the crystal melting peak when the temperature is raised from normal temperature at a rate of 5 ° C./min. Is shown. Specific examples of the crystalline epoxy resins of the general formulas (1) to (5) having a melting point of 50 to 150 ° C are shown below, but are not limited thereto.

Embedded image

[0011]

Embedded image

[0012]

Embedded image

[0013]

Embedded image

[0014]

Embedded image

The phenol resin used in the present invention includes phenol novolak resin, cresol novolak resin, xylylene-modified phenol resin, xylylene-modified biphenol resin, terpene-modified phenol resin, dicyclopentadiene-modified phenol resin, naphthol novolak resin, triphenolmethane Examples include, but are not limited to, a mold resin and a bisphenol compound. Further, these phenol resins may be used alone or in combination.

The curing accelerator used in the present invention includes:
A substance that can serve as a catalyst for a cross-linking reaction between the epoxy resin and the phenol resin. Specific examples include amine compounds such as tributylamine and 1,8-diazabicyclo (5,4,0) undecene-7, and triphenylphosphine. ,
Examples include organic phosphorus compounds such as tetraphenylphosphonium / tetraphenylborate salts, and imidazole compounds such as 2-methylimidazole, but are not limited thereto. These curing accelerators may be used alone or as a mixture.

The inorganic filler used in the present invention includes, for example, fused silica, crystalline silica, alumina, silicon nitride, aluminum nitride and the like. When the amount of the inorganic filler is particularly large, it is common to use fused silica. Fused silica can be used in either crushed or spherical form. However, in order to increase the blending amount of the fused silica and suppress an increase in the melt viscosity of the molding material, it is preferable to mainly use a spherical form. In order to further increase the blending amount of the spherical silica, it is desirable to adjust the particle size distribution of the spherical silica to be wider.

The molding material of the present invention contains the components (A) to (D) as essential components, but if necessary, a flame retardant such as a brominated epoxy resin or antimony trioxide, or a silane coupling agent. , Colorants such as carbon black, release agents such as natural wax and synthetic wax, silicone oil,
Low stress additives such as silicone rubber and synthetic rubber may be appropriately compounded. The molding material of the present invention is obtained by mixing the components (A) to (D), other additives, and the like, kneading with heat using a heating kneader or a hot roll, and then cooling and pulverizing.

The most important point in the present invention is to keep the glass transition temperature of the molding material of the present invention before molding and curing within a certain range. In the conventional concept, the glass transition temperature,
That is, the transition temperature of a substance from a glassy state to a rubbery state has been discussed for cured products of molding materials. That is, the glass transition temperature (usually 100 to 200 ° C.) of a cured product obtained by molding and curing a molding material is used as a scale representing the heat resistance of the cured product. The glass transition temperature of these cured products is determined by thermomechanical analyzer, dynamic viscoelasticity analyzer,
It is measured by a differential scanning calorimeter or the like. However, the correlation between the glass transition temperature of the molding material before molding and curing and the characteristics such as the room temperature storage characteristics has hardly been studied. In the molding material, besides epoxy resin, phenolic resin, and curing accelerator, if necessary, a silane coupling agent,
Organic compound components such as liquid silicone compound, solid silicone rubber, liquid organic synthetic rubber, solid organic synthetic rubber, natural or synthetic wax, etc. are compounded, and these are heated and kneaded together with inorganic filler to form a homogeneous molten mixture. It has become. The epoxy resin, phenolic resin, and curing accelerator in the molten mixture react by heating and curing during molding to give a cured product. On the other hand, the reaction gradually proceeds even in a temperature range of room temperature or lower. The reason for this is that each component in the molten mixture undergoes molecular motion even in a low-temperature region, thereby causing collision between molecules and reacting. The reactivity is controlled by the difficulty of the molecular motion. Normally, molding materials are stored at a low temperature of 10 ° C. or lower except for handling at room temperature during molding. However, by storing at a low temperature, the molecular motion is suppressed and the reactivity between molecules is reduced. This is to prevent the viscosity at the time of molding from changing over time during storage. The present inventor has examined the correlation between the properties of the molding material and the room temperature storage property in detail, and as a result, when the molten mixture of the organic compound component in the molding material is in a glass state at ordinary temperature, compared with a case where the molten mixture is in a rubber state, It has been found that molecular motion is extremely suppressed and the reaction hardly proceeds. In other words, it was found that when the glass transition temperature of the molding material was higher than room temperature, the reaction at room temperature was extremely suppressed, and even when stored at room temperature, the change over time in viscosity during molding over a long period of time was reduced. It is desirable that the room-temperature preservability of the molding material be maintained as long as possible. However, in practice, the ambient temperature at which the molding machine is installed (generally 25
The change in spiral flow after storage for 3 days at
0% or less, in other words, the remaining spiral flow rate is 90%
% Is preferable. For this purpose, it is preferable that the glass transition start temperature before molding and curing of the molding material is 10 ° C. or more and the glass transition end temperature is 50 ° C. or less. If the glass transition start temperature is less than 10 ° C., the residual spiral flow at 25 ° C. becomes less than 90%, while if the glass transition end temperature exceeds 50 ° C., the viscosity of the molding material at the time of molding increases, It is not preferable because chip exposure and gold wire deformation easily occur. Factors affecting the glass transition temperature of the molding material before molding and curing are roughly classified into two: the characteristics of the raw material resin to be compounded and the method of manufacturing the molding material. The softening temperature of the epoxy resin or phenol resin, which is the raw material of the molding material, is a characteristic value that is a measure of the molecular motion of the molten mixture of the organic compound components in the molding material. Generally, a resin having a high softening temperature has a high molecular weight and a softening temperature. Molecular motion is suppressed as compared to a resin having a lower temperature. However, the softening temperature shows only an average value for a resin having a certain molecular weight distribution, and does not always correspond to the proportion of low molecular weight components that react easily during storage of a molding material at room temperature.
For this reason, even if only the softening temperature of the raw material resin to be compounded is specified, the intended room temperature storage stability of the molding material cannot be achieved. Further, in the crystalline epoxy resin, since the proportion of the component having a single molecular weight is large, its melting point can be a measure of the molecular motion of the crystalline epoxy resin alone, but in the molding material, as described above. Since all organic compounds exist as a homogeneous molten mixture, the melting point determined by the strength of orientation of the crystalline epoxy resin alone can be a measure of the molecular motion of the crystalline epoxy resin in these molten mixtures. Absent. In fact, the use of a crystalline epoxy resin to achieve low viscosity and high fluidity during molding of a molding material is due to the low viscosity due to the disappearance of crystallinity of the crystalline epoxy resin in this molten mixture. It is believed that there is. Furthermore, even in the step of heating and kneading the molding material, the epoxy resin and the phenol resin react with each other, so that the molecular weight in the molding material changes according to the degree of the reaction, and therefore, the degree of difficulty in molecular motion at room temperature also changes. In general, in high-temperature, long-time kneading, the reaction proceeds and the molecular weight of the epoxy resin and the phenol resin increases, so that the molecular motion at room temperature is suppressed, and therefore, the glass transition temperature before molding and curing tends to increase. . To measure the glass transition temperature of the molding material before molding and curing, a vibration temperature mode differential scanning calorimeter (hereinafter referred to as M
It is preferable to use DSC). In a normal differential scanning calorimeter, the temperature of the sample is changed linearly with respect to time during the measurement, and the change in the calorific value of the sample is detected. On the other hand, in the MDSC, the temperature of the sample is linear and wavy. Are performed in combination. That is, by changing the temperature by a sinusoidal curve with a constant amplitude and a constant cycle, the reversible transition and the irreversible transition of the sample are detected and separated,
The glass transition temperature can be determined from the reversible transition. The measurement was carried out using a vibration temperature mode differential scanning calorimeter (TA Instruments 2910 MDSC type) in a nitrogen stream at a temperature rising rate of 2 ° C / -25 ° C to 150 ° C.
And an amplitude of ± 2 ° C./min.

[0020]

The present invention will be specifically described below with reference to examples.
The unit of the compounding amount is part by weight. Example 1 7.9 parts by weight of an epoxy resin A having a structure represented by the formula (6) as a main component (YX4000H, melting point 105 ° C, epoxy equivalent 195, manufactured by Yuka Shell Epoxy Co., Ltd.)

Embedded image

A phenolic resin J represented by the formula (7) (1 is an integer of 1 or more, XL225-LL, manufactured by Mitsui Toatsu Chemicals, Inc., softening point 75 ° C., hydroxyl equivalent 175) 7.1 parts by weight

Embedded image 1,8-diazabicyclo (5,4,0) undecene-7 (hereinafter referred to as DBU) 0.2 parts by weight Spherical fused silica 84.0 parts by weight Carbon black 0.3 parts by weight Carnauba wax 0.5 parts by weight After mixing using, the surface temperature is 90 ° C and 2
The mixture was kneaded 20 times using a biaxial roll at 5 ° C., and the obtained kneaded material sheet was cooled and pulverized to obtain a molding material. The properties of the obtained molding material were evaluated by the following methods. Table 1 shows the results.

Evaluation method Spiral flow: Using a mold for measuring spiral flow according to EMMI-I-66, using a mold temperature of 175 ° C.
The measurement was performed at an injection pressure of 70 kg / cm ² and a curing time of 2 minutes. Initial spiral flow: the measured value (in cm) of the molding material immediately after production. Spiral flow residual ratio: 2
The value obtained by dividing the spiral flow value measured after storage at 5 ° C. for 3 days by the initial spiral flow value (unit%). Glass transition temperature (hereinafter, referred to as Tg): The glass transition start temperature and the glass transition end temperature before molding and curing of the molding material were measured by the methods described above (unit: ° C.). Deformation amount of gold wire, chip shift amount: 144p QFP package (package size 20 × 20 × 1.4 mm, chip size 9 × 9 mm, gold wire: 25 μm diameter, lead frame: copper), mold temperature 175 ° C., molding pressure 75 kgf / c
m ² , molded in 2 minutes. The obtained package was observed with a soft X-ray fluoroscope, and the deformation rate of the gold wire was represented by (flow amount) / (gold wire length) (unit%). Further, the package was cut along the diagonal line from the gate, the distance from the package surface to the upper surface of both ends of the chip was measured, and the difference was defined as the chip shift amount (unit: μm).

Examples 2 to 6 A molding material was obtained in the same manner as in Example 1 except that the composition of Example 1 was used as a basic compound, the type of the crystalline epoxy resin was changed, and the amounts of the epoxy resin and the phenol resin were changed. . Evaluation was performed in the same manner as in Example 1. Table 1 shows the formulation and results. Examples 7 and 8, Comparative Examples 1 and 2 Example 1 was used as a basic formulation and the softening temperature of the phenol resin was determined.
A molding material was obtained in the same manner as in Example 1 except that the number of roll kneading was changed. Evaluation was performed in the same manner as in Example 1. The formulations and results are shown in Tables 1 and 2. Examples 9 and 10 and Comparative Examples 3 and 4 A molding material was obtained in the same manner as in Example 1 except that Example 1 was used as a basic compound and the types of the epoxy resin and the phenol resin and the number of times of kneading the rolls were changed. Evaluation was performed in the same manner as in Example 1. The formulations and results are shown in Tables 1 and 2. Examples 11 and 12 and Comparative Example 5 A molding material was obtained in the same manner as in Example 1 except that Example 1 was used as a basic compounding agent and the types and amounts of the epoxy resin and the phenol resin were changed. Evaluation was performed in the same manner as in Example 1. The formulations and results are shown in Tables 1 and 2.

The structures and properties of the epoxy resin and phenol resin used in the above Examples and Comparative Examples are shown below.

Embedded image

[0025]

Embedded image

[0026]

Embedded image

[0027]

Embedded image

[0028]

Embedded image

[0029]

Embedded image

[0030]

Embedded image The epoxy resin B is a 50/50 mixture of an epoxy resin having a structure represented by the formula (6) as a main component and an epoxy resin having a structure represented by the formula (8) as a main component (oil). Shell Epoxy Co., Ltd. YL6121H,
130 ° C, epoxy equivalent 170). Epoxy resin C
Is an epoxy resin having a structure represented by the formula (9) as a main component (melting point: 144 ° C., epoxy equivalent: 175). The epoxy resin D is a mixture of an epoxy resin having a structure represented by the formula (10) as a main component and an epoxy resin having a structure represented by the formula (11) as a main component at a weight ratio of 60/40 (melting point: 132 ° C, epoxy equivalent 210). The epoxy resin E is an epoxy resin having a structure represented by the formula (12) as a main component (1 is an integer of 1 or more, a melting point of 82 ° C., and an epoxy equivalent of 190). The epoxy resin F is an epoxy resin having a structure represented by the formula (13) as a main component (l is 1
The above integer, melting point 133 ° C., epoxy equivalent 182). Epoxy resin G has a softening temperature of 55 ° C. and an epoxy equivalent of 195.
Orthocresol novolak type epoxy resin.
Epoxy resin H has a softening temperature of 75 ° C. and an epoxy equivalent of 20.
0 orthocresol novolak type epoxy resin. The epoxy resin I is an epoxy resin having a structure represented by the formula (14) as a main component (n is an integer of 1 or more, HP-7200 manufactured by Dainippon Ink and Chemicals, softening temperature 60 ° C, epoxy Equivalent 260). Phenol resin K
Is represented by the formula (7) (1 is an integer of 1 or more, XL225-L, manufactured by Mitsui Toatsu Chemicals, Inc., softening temperature: 85 ° C., hydroxyl equivalent: 180). The phenolic resin L is represented by the formula (7) (1 is an integer of 1 or more, manufactured by Mitsui Toatsu Chemicals, Inc.)
XL-4L, softening temperature 62 ° C, hydroxyl equivalent 170). Phenol resin M has a softening temperature of 60 ° C. and a hydroxyl equivalent of 105.
Phenol novolak resin. Phenol resin N
Is a phenol novolak resin having a softening temperature of 110 ° C. and a hydroxyl equivalent of 104.

[0031]

[Table 1]

[0032]

[Table 2]

[0033]

The epoxy resin molding material for semiconductor encapsulation of the present invention has good storage stability at room temperature, so that even when stored at room temperature, the fluidity during molding hardly decreases over time.
It is excellent in formability without generating gold wire deformation and chip shift, and is excellent in soldering resistance.

Claims (3)

[Claims] 1. An epoxy resin molding obtained by heating and kneading a composition containing (A) an epoxy resin, (B) a phenol resin curing agent, (C) a curing accelerator, and (D) an inorganic filler as essential components. An epoxy resin molding material for semiconductor encapsulation, wherein the molding material has a glass transition start temperature before molding and curing of 10 ° C. or more and a glass transition end temperature of 50 ° C. or less. 2. The epoxy resin according to any one of the general formulas (1) to (5)
The epoxy resin molding material for semiconductor encapsulation according to claim 1, which is at least one selected from the group consisting of crystalline epoxy resins having a melting point of 50 to 150 ° C. Embedded image Embedded image Embedded image Embedded image Embedded image (R in the formulas (1) to (4) represents a hydrogen atom, a halogen atom, or an alkyl group having 1 to 12 carbon atoms, and may be the same or different from each other. In the formula (5), R is
It represents a halogen atom or an alkyl group having 1 to 12 carbon atoms, which may be the same or different. In the formula (5), l is a positive integer of 1 to 10, and m is 0 or 1.
And n is a positive integer of 0 or 1-4. ) 3. A semiconductor device which is sealed using the epoxy resin molding material for semiconductor sealing according to claim 1.