JP2002212393A - Epoxy resin composition and semi-conductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an epoxy resin composition which is used for sealing semiconductors, is hardly bent after molded and after sealed with a solder, and is suitable for area-packing semiconductor devices. SOLUTION: This epoxy resin composition containing (A) an epoxy resin, (B) a phenol resin, (C) a curing accelerator, (D) an organic filler, and (E) a glycerol trifatty acid ester comprising glycerol and a 24 to 36C saturated fatty acid as essential components is characterized in that the component (E) and the inorganic filler are contained in amounts of 0.05 to 0.5 wt.% and 80 to 94 wt.%, respectively, based on the total epoxy resin composition.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a so-called area mounting type semiconductor device in which a semiconductor element is mounted on one surface of a printed wiring board or a metal lead frame, and substantially only one of the mounting surfaces is resin-sealed. The present invention relates to a suitable epoxy resin composition for semiconductor encapsulation 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 equipment, high integration of semiconductor elements has been progressing year by year, and surface mounting of semiconductor devices has been promoted. In recent years, area-mounted semiconductor devices have been developed, and are beginning to shift from semiconductor devices having conventional structures. Area mounting type semiconductor devices include BGA (ball grid array),
Alternatively, a CSP (chip scale package) or the like pursuing further miniaturization is a typical example.
The surface mount type semiconductor device represented by the SOP and the like has been developed in order to meet the demand for multi-pin and high-speed, which is approaching the limit. The structure is as follows: on one side of a hard circuit board represented by a BT resin / copper foil circuit board (bismaleimide / triazine resin / glass cloth board) or a flexible circuit board represented by a polyimide resin film / copper foil circuit board A semiconductor element is mounted, and only the semiconductor element mounting surface, that is, only one side of the substrate is molded and sealed with an epoxy resin composition or the like. Further, on the surface opposite to the semiconductor element mounting surface of the substrate, solder balls are formed two-dimensionally in parallel, and are characterized in that they are joined to a circuit board on which a semiconductor device is mounted. Further, as a substrate on which a semiconductor element is mounted, a structure using a metal substrate such as a lead frame has been developed in addition to the above-described organic circuit substrate.

The structure of these area-mounted semiconductor devices is as follows:
A single-sided sealing configuration is adopted in which only the semiconductor element mounting surface of the substrate is sealed with the epoxy resin composition and the solder ball forming surface is not sealed. On a metal substrate such as a lead frame, a sealing resin layer of about several tens of μm may be present even on the surface on which the solder ball is formed, but several hundred μm on the surface on which the semiconductor element is mounted.
Since a sealing resin layer having a thickness of about several mm is formed, substantially single-sided sealing is achieved. For this reason, these semiconductor devices may be affected by mismatch of thermal expansion and thermal shrinkage between the organic substrate or the metal substrate and the cured product of the epoxy resin composition, or the effect of curing shrinkage during molding and curing of the epoxy resin composition. In this case, warpage tends to occur immediately after molding. Further, when soldering is performed on a circuit board on which these semiconductor devices are mounted, 200
The semiconductor device goes through a heating step of ℃ or more. At this time, warpage of the semiconductor device occurs, and many solder balls do not become flat, and float up from the circuit board on which the semiconductor device is mounted, thereby lowering the reliability of electrical bonding. There is also a problem to do.

In a semiconductor device in which substantially only one surface on a substrate is sealed with an epoxy resin composition, in order to reduce warpage, the thermal expansion coefficient of the substrate and the thermal expansion coefficient of a cured product of the epoxy resin composition are determined. Two approaches are important: approaching and reducing curing shrinkage during molding and curing of the epoxy resin composition. As a substrate, an organic substrate has a high glass transition temperature (hereinafter, referred to as BT resin or polyimide resin).
Resins having a Tg) are widely used, and have a Tg higher than around 170 ° C., which is the molding temperature of the epoxy resin composition. Accordingly, during the cooling process from the molding temperature to room temperature, the organic substrate contracts only in the region of α1. Therefore, if the cured product of the epoxy resin composition has a high Tg and the same α1 as that of the organic substrate, and if the curing shrinkage during molding and curing becomes zero, the warpage is considered to be almost zero. For this reason, a method has already been proposed in which Tg is increased by combining a polyfunctional epoxy resin and a polyfunctional phenol resin, and α1 is adjusted by the amount of the inorganic filler.

[0005] When soldering is performed by soldering by means such as infrared reflow, vapor phase soldering, or solder immersion, the epoxy resin composition is present inside the semiconductor device due to moisture absorption from a cured product and an organic substrate. Cracks occur in semiconductor devices due to stress caused by rapid evaporation of moisture at high temperatures, and peeling may occur at the interface between the semiconductor element mounting surface of the organic substrate and the cured epoxy resin composition. In addition to reducing the stress and moisture absorption of the resin composition, the resin composition is required to have adhesiveness to an organic substrate. Furthermore, due to the thermal expansion mismatch between the organic substrate and the cured product of the epoxy resin composition, peeling and cracking of the interface between the organic substrate and the cured product of the epoxy resin composition are likely to occur even in a temperature cycle test, which is a typical example of a reliability test. Occurs. Conventional QFP and S
In a surface-mount type semiconductor device such as an OP, a crystalline epoxy resin represented by a biphenyl type epoxy resin and a flexible skeleton are used to prevent cracks at the time of solder mounting and peeling at an interface with each material. In order to reduce Tg and moisture absorption by using a combination of a phenolic resin having a phenolic resin and increasing the blending amount of an inorganic filler, measures have been taken. However, at present, this method cannot solve the problem of warpage in a single-sided encapsulated semiconductor device.

[0006]

SUMMARY OF THE INVENTION The present invention provides an epoxy resin composition which is small in warpage after molding or soldering and is suitable for sealing an area-mounted semiconductor, and a semiconductor device using the same. is there.

[0007]

The present invention comprises (A) an epoxy resin, (B) a phenolic resin, (C) a curing accelerator,
(D) an inorganic filler, and (E) glycerin and carbon number 24.
In the epoxy resin composition containing a glycerin trifatty acid ester with a saturated fatty acid as an essential component, the component (E) is 0.05 to 0.5% by weight in the total epoxy resin composition, and the inorganic filler is 8 in all epoxy resin compositions
An epoxy resin composition for encapsulating a semiconductor in an area mounting type, wherein the semiconductor element is mounted on one side of a substrate, and substantially only one side of the substrate side on which the semiconductor element is mounted; Is a semiconductor device characterized by being sealed using the epoxy resin composition.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors consider that it is necessary to reduce the curing shrinkage during the molding and curing and the heat shrinkage from the molding temperature to room temperature in the epoxy resin composition in order to reduce the warpage. As a result of diligent studies, the present inventors have found that an epoxy resin composition using a specific wax has a small curing shrinkage during molding and curing, and is excellent in reducing warpage in an area-mounted semiconductor device. Reached.

The epoxy resin used in the present invention refers to all monomers, oligomers and polymers having two or more epoxy groups in one molecule. For example, ortho-cresol novolak epoxy resin, phenol novolak epoxy resin, biphenyl epoxy resin, bisphenol epoxy resin, stilbene epoxy resin, triphenolmethane epoxy resin, phenol aralkyl epoxy resin (phenylene skeleton, biphenylene skeleton, etc. Naphthol type epoxy resin, alkyl-modified triphenol methane type epoxy resin, triazine nucleus-containing epoxy resin, dicyclopentadiene-modified phenol type epoxy resin, and the like. These may be used alone or in combination of two or more. Good. Among these, in particular, a crystalline epoxy resin that has a low melt viscosity, can be highly filled with an inorganic filler, and thus enables low moisture absorption of the epoxy resin composition, and can improve solder crack resistance is preferable. .

The phenolic resin used in the present invention comprises 1
It refers to all monomers, oligomers and polymers having two or more phenolic hydroxyl groups in the molecule. For example, phenol novolak resin, cresol novolak resin,
Phenol aralkyl resins (including phenylene skeleton, biphenylene skeleton, etc.), naphthol aralkyl resins (including phenylene skeleton, biphenylene skeleton, etc.), triphenolmethane resin, terpene-modified phenolic resin, dicyclopentadiene-modified phenolic resin, and the like. May be used alone or in combination of two or more.

[0011] The curing accelerator used in the present invention includes:
It refers to a compound that can serve as a catalyst for a cross-linking reaction between the epoxy resin and the phenol resin, for example, amine compounds such as 1,8-diazabicyclo (5,4,0) undecene-7, tributylamine, triphenylphosphine, and tetraphenylphosphine. Examples include, but are not limited to, organophosphorus compounds such as phonium tetraphenylborate salts, and imidazole compounds such as 2-methylimidazole. These may be used alone or in combination of two or more.

The type of the inorganic filler used in the present invention is not particularly limited, and those generally used for a sealing material can be used. For example, fused silica,
Examples thereof include crystalline silica, secondary aggregated silica, alumina, titanium white, aluminum hydroxide, talc, clay, and glass fiber, with fused silica being particularly preferred. Fused silica can be used in any of a crushed form and a spherical form. However, in order to increase the blending amount and suppress an increase in the melt viscosity of the epoxy resin composition, it is more preferable to mainly use the spherical silica. In order to further increase the content of the spherical silica, it is desirable to adjust the particle size distribution of the spherical silica to be wider. The content of the inorganic filler is preferably 80 to 9 in the total epoxy resin composition in view of the balance between moldability and reliability.
4% by weight is preferred. If the content is less than 80% by weight, the curing shrinkage during the molding and curing and the thermal shrinkage from the molding temperature to room temperature increase, so that the warpage increases, and the moisture absorption rate increases, so that the solder crack resistance decreases, which is not preferable. If it exceeds 94% by weight, the fluidity is reduced, and the moldability is deteriorated. If necessary, the inorganic filler may be treated in advance with a coupling agent, an epoxy resin, a phenol resin curing agent, or the like, and may be used. As a treatment method, for example, after mixing using a solvent, the solvent is removed. There is a method of removing, a method of directly adding to the inorganic filler, and treating using a mixer.

Glycerin used in the present invention and carbon number 2
Glycerin trifatty acid esters with saturated fatty acids of 4 to 36 have been conventionally used as mold release agents, but the present inventor has newly found an effect of reducing the warpage of the area-mounted semiconductor device. Incidentally, the carbon number of the saturated fatty acid in the present invention,
It refers to the sum of the carbon numbers of the alkyl group and the carboxyl group in the saturated fatty acid. If the number of carbon atoms of the saturated fatty acid used for the esterification in the present invention is 23 or less, the effect of reducing warpage is insufficient, and sufficient release properties cannot be obtained, which is not preferable. If the number of carbon atoms is 37 or more, the molecular weight is too large to lower the fluidity, or excessively seeping out may cause mold contamination, which is not preferable. Examples of the saturated fatty acids having 24 to 36 carbon atoms of the present invention include lignoceric acid, cerotic acid, montanic acid, and the like, and these may be used alone or in combination of two or more. The same or different ones may be used in combination. Monoesters and diesters are not preferable because the moisture resistance of the cured product of the epoxy resin composition is reduced due to the influence of the remaining hydroxyl groups, and as a result, the solder crack resistance is adversely affected. The glycerin trifatty acid ester of the present invention may be used alone or in combination of two or more. The content of the glycerin trifatty acid ester of the present invention is 0.05 to 0.5 in all epoxy resin compositions.
% By weight is preferred. If the content is less than 0.05% by weight, the effect of reducing warpage is low. If the content is more than 0.5% by weight, problems such as curability and moldability such as appearance of a molded product are caused, and solder cracking resistance due to reduced adhesion. Is undesirably reduced. The epoxy resin composition of the present invention may be used in combination with a mold release agent such as a natural wax, a synthetic wax, a higher fatty acid and its metal salts or paraffin, to the extent that moldability such as curability is not impaired. May be used alone or in combination of two or more.

The epoxy resin composition of the present invention comprises (A)
In addition to the component (E), if necessary, an inorganic ion exchanger, a coupling agent, a coloring agent represented by carbon black, a brominated epoxy resin, a flame retardant such as antimony oxide, a phosphorus compound, a silicone oil, a rubber, etc. Various additives such as a low stress component and an antioxidant can be appropriately compounded. The epoxy resin composition of the present invention is obtained by mixing the components (A) to (E) and other additives using a mixer or the like, and then heating the kneader.
Heat kneading with a kneading machine such as a hot roll or extruder, cooling,
Obtained by grinding. Using the epoxy resin composition of the present invention to encapsulate electronic components such as semiconductor elements and manufacture semiconductor devices, transfer molding, compression molding, injection molding and other conventional molding methods such as curing molding Good. In particular, the epoxy resin composition of the present invention is suitable for an area mounting type semiconductor device.

[0015]

The present invention will be specifically described below with reference to examples.
The mixing ratio is by weight. Example 1 Biphenyl type epoxy resin (melting point 105 ° C, epoxy equivalent 185) 6.40 parts by weight Phenol novolak resin (softening point 81 ° C, hydroxyl equivalent 105) 4.00 parts by weight Triphenylphosphine 0.15 parts by weight Spherical fused silica (Average particle size: 15 μm) 86.75 parts by weight Glycerin trimontanate (the carbon number of the saturated fatty acid before esterification is 29) 0.20 parts by weight Carnauba wax 0.20 parts by weight Carbon black 0.30 parts by weight Brominated phenol Novolak type epoxy resin (epoxy equivalent: 273) 1.00 parts by weight After mixing 1.00 parts by weight of antimony trioxide with a mixer, kneading using two rolls having a surface temperature of 90 ° C. and 45 ° C., cooling and pulverizing. Thus, an epoxy resin composition was obtained. The obtained epoxy resin composition was evaluated by the following method. Table 1 shows the results.

Evaluation method Spiral flow: Using a mold for spiral flow measurement in accordance with EMMI-1-66, a mold temperature of 175 ° C.
The measurement was performed at an injection pressure of 6.9 MPa and a curing time of 120 seconds.
The unit is cm. Shore D hardness: mold temperature 175 ° C, injection pressure 6.9MP
a, Molding was performed with a curing time of 120 seconds, and the value of Shore D hardness measured 10 seconds after opening the mold was defined as curability. Shore D hardness is an index of curability, and the larger the numerical value, the better the curability. Package warpage (before soldering): Using a transfer molding machine, mold temperature 175 ° C, injection pressure 6.9MP
a, with a curing time of 90 seconds, 225 pBGA (thickness 0.36
mmBT resin substrate, chip size 12mm × 12mm ×
0.35mm thickness, package size 24mm x 24m
m, thickness of sealing resin 1.17 mm), and 175
Post-cured at 2 ° C. for 2 hours. After cooling to room temperature, displacement in the height direction was measured using a surface roughness meter in the diagonal direction from the gate of the package, and the largest value of the displacement difference was defined as the amount of package warpage. The unit is μm. Solder crack resistance: The above 225pBGA was molded and
Post-curing was performed at 75 ° C. for 2 hours to obtain 10 samples.
168 hours or 8 in an environment of 60 ° C. and 60% relative humidity
The treatment was performed for 168 hours in an environment of 5 ° C. and a relative humidity of 60%, and then for 10 seconds by IR reflow (240 ° C.). Observation was performed using an ultrasonic flaw detector to check for internal cracks and various interface peelings. When the number of defective packages is n, n / 10 is displayed. Package warpage (after soldering): 225 pBG described above
A was molded and post-cured at 175 ° C. for 2 hours to obtain a sample. The treatment was performed for 168 hours in an environment at 60 ° C. and a relative humidity of 60%, and then for 10 seconds by IR reflow (240 ° C.). After cooling to room temperature, a package having no defect was selected, and the displacement in the height direction was measured diagonally from the gate using a surface roughness meter, and the value of the largest displacement difference was defined as the amount of package warpage. The unit is μm.

Examples 2 to 5 and Comparative Examples 1 to 5 Epoxy resin compositions were prepared according to Table 1 in the same manner as in Example 1, and evaluated in the same manner as in Example 1. Table 1 shows the results. The properties of the epoxy resin and phenol resin used in Examples and Comparative Examples are shown below. Dicyclopentadiene type epoxy resin (softening point 53 ° C, epoxy equivalent 244), naphthol aralkyl resin (softening point 87 ° C,
Hydroxyl equivalent 210), glycerin tristearate (saturated fatty acid having 18 carbon atoms before esterification).

[Table 1]

[0018]

According to the present invention, an epoxy resin composition suitable for encapsulating an area-mounted semiconductor can be obtained, and a semiconductor device using the same has a small warpage after molding or soldering.

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Claims (2)

[Claims] 1. A glycerin trifatty acid comprising (A) an epoxy resin, (B) a phenolic resin, (C) a curing accelerator, (D) an inorganic filler, and (E) glycerin and a saturated fatty acid having 24 to 36 carbon atoms. In the epoxy resin composition containing an ester as an essential component, the component (E) is 0.05 to 0.5% by weight in the total epoxy resin composition, and the inorganic filler is 80 to 94% in the total epoxy resin composition. An area-mount type epoxy resin composition for encapsulating a semiconductor, characterized in that the content is in weight%. 2. A semiconductor device is mounted on one surface of a substrate, and substantially only one surface on the substrate surface side on which the semiconductor device is mounted is sealed with the epoxy resin composition according to claim 1. A semiconductor device characterized by the above-mentioned.