JP2003040979A - Semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an area-mounting semiconductor device having small warpage after a molding and in a soldering process. SOLUTION: The area-mounting semiconductor device is characterized in that a semiconductor device obtained by sealing a semiconductor element with the following epoxy resin compositions has an area of the element 40% or more based on an area of the device. In the epoxy resin composition having (A) an epoxy resin, (B) a phenolic resin, (C) an inorganic filler and (D) a curing promoter as essential components and the filler of 65-95 wt.% based on a total of the composition, a glass transition temperature of a cured material of the composition is less than 130 deg.C, a flexural modulus is (1) less than 20,000 N/mm<2> at a temperature range of 25 deg.C to 'the glass transition temperature + 5 deg.C', (2) less than 8,000 N/mm<2> at a temperature range of 'the glass transition temperature + 5 deg.C' to 140 deg.C and (3) less than 1, 000 N/mm<2> at a temperature range of 140 deg.C to 175 deg.C and a heat shrinkage rate at a range of the glass transition temperature to 25 deg.C is less than 0.2%.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an area mounting type semiconductor device in which a semiconductor element area is at least 40% of a semiconductor device area. 2. Description of the Related Art In recent years, the amount of information processing has become enormous in electronic devices equipped with LSI, and high-speed operation has been strongly demanded. Accordingly, the required number of terminals of the LSI has been rapidly increasing. In order to arrange a large number of external terminals of a semiconductor device at a wide pitch, it is effective to use the lower surface of the semiconductor device.
An area array type surface mounting semiconductor device in which solder bumps are arranged in a matrix in this portion is a BGA (Ball Gr).
id Array). Meanwhile, miniaturization of mobile devices,
As semiconductor devices are becoming thinner and lighter, semiconductor devices are also required to have lower power and higher functionality. Semiconductor devices in which these semiconductor devices are encapsulated are also required to be smaller, thinner, and lighter. CSP has been put to practical use as a result.
(Chip Size Package). Basically, the terminal pitch of the BGA is reduced to the extent that low-cost consumer mounting is possible, and the outer shape of the semiconductor device is reduced to almost the size of a semiconductor element. But,
Currently, the semiconductor device is undergoing a major transformation, and the structure of the CSP has been diversified in pursuit of cost performance. At the same time, demands for epoxy resin compositions for semiconductor encapsulation have been increasing. 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. Very rarely, on a metal substrate such as a lead frame, a sealing resin layer of about several tens of μm may exist even on the surface on which the solder balls are formed, but on a semiconductor element mounting surface, a sealing of several hundred μm to several mm. Since the resin layer is formed, the one side is substantially sealed. Therefore, due to the thermal expansion and thermal contraction mismatch between the organic substrate or metal substrate and the cured product of the epoxy resin composition, or the influence of curing shrinkage during the molding and curing of the epoxy resin composition, these semiconductor devices cannot be molded. Warpage tends to occur immediately after. In addition, when soldering is performed on a circuit board on which these semiconductor devices are mounted,
The semiconductor device goes through a heating process at a temperature of 00 ° C. or higher. However, warping of the semiconductor device occurs at this time, and a large number of solder balls are not flattened. The problem arises. In order to reduce the warpage in an area-mounted semiconductor device having a small semiconductor element area with respect to the semiconductor device area, the linear expansion coefficient of the substrate and the linear expansion coefficient of the cured product of the epoxy resin composition must be close to each other. There is a method of reducing the amount of curing shrinkage of an object. As the substrate, resins having a high glass transition temperature, such as bismaleimide / triazine resins and polyimide resins, are widely used in organic substrates, and these are glass substrates having a temperature higher than 170 ° C., which is the molding temperature of the epoxy resin composition. Since the organic substrate has a transition temperature, in the cooling process from the molding temperature to room temperature, the organic substrate contracts only in a region having a linear expansion coefficient α1 (hereinafter referred to as α1). Therefore, the cured product of the epoxy resin composition also has a high glass transition temperature, α1 is the same as that of the organic substrate, and if the curing shrinkage is zero, the warpage is considered to be almost zero. However, miniaturization and thinning of semiconductor devices,
As the demand for weight reduction increases and the semiconductor element area increases with respect to the semiconductor device area, the difference between the coefficient of linear expansion of the organic substrate and the coefficient of linear expansion of the cured product of the epoxy resin composition and the amount of cure shrinkage of the epoxy resin composition are called It is no longer possible to solve the warpage problem from the viewpoint alone. SUMMARY OF THE INVENTION The present invention relates to an epoxy resin composition having specific flexural modulus and heat shrinkage characteristics, wherein the area of a semiconductor element is 40 to the area of a semiconductor device.
An area mounting type semiconductor device which is obtained by sealing a semiconductor element of not less than% and has a small warpage after molding or soldering. According to the present invention, there is provided [1] a semiconductor device obtained by encapsulating a semiconductor element using the following epoxy resin composition. Hereinafter, the area occupied by the semiconductor element) is 40%.
An area mounting type semiconductor device characterized by the above. An epoxy resin containing (A) an epoxy resin, (B) a phenol resin, (C) an inorganic filler, and (D) a curing accelerator as essential components, and containing 65 to 95% by weight of an inorganic filler in the entire epoxy resin composition. In the composition, the cured product of the epoxy resin composition has a glass transition temperature of less than 130 ° C. and a flexural modulus of less than 20,000 N / mm ² within a temperature range of 25 ° C. to “glass transition temperature + 5 ° C.” Temperature + 5 ° C ”to less than 8000 N / mm ² in the temperature range of 140 ° C, 1000 in the temperature range of 140 ° C to 175 ° C
An epoxy resin composition having a heat shrinkage of less than 0.2% from N / mm ² and from the glass transition temperature to 25 ° C.,
It is. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention relates to a method for sealing a semiconductor device having an area occupied by a semiconductor element of 40% or more, when bending an elastic modulus and a glass transition within a temperature range of 25 ° C. to 175 ° C. By controlling the heat shrinkage when cooled from a temperature (hereinafter, referred to as Tg) to 25 ° C., it was found that warpage after molding and during soldering could be reduced, and a specific range of flexural elasticity was found. This is an area-mounted semiconductor device sealed with an epoxy resin composition having the characteristics of heat shrinkage and heat shrinkage. [0008] The reason that the area occupied by the semiconductor element is 40% or more is that if the area occupied by the semiconductor element is less than 40%, the epoxy resin composition approaches the two-layer structure of the substrate and the cured product of the epoxy resin composition. By increasing the Tg of the cured product of the above to make the coefficient of linear expansion of the substrate close to the linear expansion coefficient of the cured product of the epoxy resin composition, the heat shrinkage after molding and curing is reduced, and the cured product of the epoxy resin composition is reduced. This is because a technique of reducing the curing shrinkage of the resin has already been established. However, when the occupied area of the semiconductor element exceeds 40%,
The area of the semiconductor element occupying the entire area cannot be ignored, and the semiconductor device must be considered as a three-layer structure including the semiconductor element, the substrate, and the cured product of the epoxy resin composition. The linear expansion coefficient of the semiconductor element hardly changes in the range from room temperature to the molding temperature, and has a significantly higher rigidity and a lower linear expansion coefficient than the cured product of the substrate and the epoxy resin composition. Therefore, reducing the warpage means how to suppress the deformation of the semiconductor element, and the rigidity of the cured product of the epoxy resin composition at a molding temperature or lower greatly affects. The cured product of the epoxy resin composition has a flexural modulus of 200 in the temperature range from 25 ° C. to “Tg + 5 ° C.”.
00N / mm ² or more, or 14 from “Tg + 5 ° C”
Flexural modulus 8000 N / mm in the temperature range of 0 ° C
^{When the} bending elastic modulus is 1000 N / mm ² or more in the temperature range of 140 ° C. to 175 ° C. or more, the bending moment of the epoxy resin composition toward the cured product due to heat shrinkage becomes large, so that the solder balls are mounted on the substrate. The concave warpage is likely to occur with the surface facing down. Further, when the Tg of the cured product of the epoxy resin composition is 130 ° C. or higher, the temperature range from Tg to room temperature is widened, the heat shrinkage in the region where the flexural modulus is large is large, and the cured product of the epoxy resin composition is This is because a large bending moment is easily generated on the side. In order to reduce the flexural modulus of the cured product of the epoxy resin composition, the content of the inorganic filler may be reduced. If the components such as epoxy resin, phenolic resin and curing accelerator are the same, the less the content of the inorganic filler,
Flexural modulus tends to be small. However, as the content of the inorganic filler is reduced, the moldability is better but the problem of cracking of the semiconductor device during the soldering process due to expansion of the moisture absorption of the semiconductor device is liable to be caused. If the content of the material is less than 65% by weight, it is not preferable. On the other hand, it is effective to increase the content of the inorganic filler in order to reduce the heat shrinkage of the semiconductor device and improve the solder crack resistance, but the bending elastic modulus is easily increased and the moldability ( Fillability, voids, flow marks, gold wire deformation, etc.) and the content of inorganic filler is 95
If the content exceeds% by weight, this phenomenon becomes remarkable, which is not preferable. The epoxy resin composition used in the present invention contains an epoxy resin, a phenol resin, an inorganic filler and a curing accelerator as essential components. Examples of the epoxy resin include bisphenol A epoxy resin and bisphenol F epoxy resin. , Stilbene 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, terpene modified phenol type epoxy resin, hydroquinone type Examples include, but are not limited to, epoxy resins. Examples of the phenol resin include, but are not limited to, phenol novolak resin, cresol novolak resin, dicyclopentadiene-modified phenol resin, phenol aralkyl resin, terpene-modified phenol resin, and triphenolmethane resin. Examples of the inorganic filler include fused silica, fused spherical silica, crystalline silica, secondary aggregated silica, alumina, titanium white, aluminum hydroxide, and the like, and fused spherical silica is particularly preferred. As the shape of the spherical silica, it is preferable that the shape is infinitely spherical and the particle size distribution is broad in order to improve fluidity. As the curing accelerator, for example, 1,8-diazabicyclo (5,4,0) undecene-7, triphenylphosphine, benzyldimethylamine, 2-methylimidazole, or the like may be used alone or in combination. The epoxy resin composition used in the present invention comprises:
In addition to the components (A) to (D), if necessary, brominated epoxy resins, flame retardants such as antimony oxide, inorganic ion exchangers such as bismuth oxide hydrate, and γ-glycidoxypropyltrimethoxysilane. Coupling agents, colorants such as carbon black and red bean, low-stress components such as silicone oil and silicone rubber, natural wax, synthetic wax,
Release agents such as higher fatty acids and metal salts thereof or paraffin, and various additives such as antioxidants may be appropriately blended. Furthermore, if necessary, the inorganic filler may be pre-treated with a coupling agent, an epoxy resin or a phenol resin and used, and the treatment may be carried out by removing the solvent after mixing with a solvent or directly using the inorganic filler. There is a method of adding to a material and treating using a mixer. The epoxy resin composition used in the present invention comprises:
The components (A) to (D), other additives, and the like are mixed at room temperature using a mixer, melt-kneaded in a kneader such as an extruder such as a roll or a kneader, cooled, and pulverized. In order to manufacture an area-mounted semiconductor device by encapsulating a semiconductor element using the epoxy resin composition of the present invention, it is sufficient to cure and mold by a molding method such as a transfer mold, a compression mold, and an injection mold. BGA, LGA and the like are available as area-mounted semiconductor devices in the present invention.
(Land Grid Array Package
e), QFN (Quad Flatpack Non-1)
Eaded Package). The present invention will be described below with reference to examples, but the present invention is not limited to these examples. Example 1 Fused spherical silica (average particle size: 15 μm, specific surface area: 2.2 m ² / g) 70.00 parts by weight Tetramethylbiphenyl diglycidyl ether (Yuka Shell Epoxy Co., Ltd., YX-4000K, melting point: 108 ° C., epoxy) Equivalent 185) 12.48 parts by weight Phenol aralkyl resin 1 (manufactured by Mitsui Chemicals, Inc., XL-225, softening point 71 ° C., hydroxyl equivalent 174) 6.56 parts by weight Phenolic resin represented by the formula (1) (softening point) 87 ° C., hydroxyl equivalent 210) 6.56 parts by weight 1,8-diazabicyclo (5,4,0) undecene-7 (hereinafter referred to as DBU) 2.00 parts by weight Brominated bisphenol A type epoxy resin 0.50 parts by weight Antimony trioxide 1.00 parts by weight γ -Glycidylpropyltrimethoxysilane 0.20 parts by weight Carnauba wax 0.40 parts by weight Carbon black 0.30 parts by weight is mixed at room temperature with a mixer, kneaded at 70 to 120 ° C with two rolls, cooled and ground. 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 measuring spiral flow according to EMMI-1-66, the measurement was performed at a mold temperature of 175 ° C., an injection pressure of 6.9 MPa, and a curing time of 2 minutes. The unit is cm. Tg: Using a transfer molding machine, mold temperature 175
° C, injection pressure 9.8MPa, curing time 2 minutes, 4mm × 4
When a test piece molded into a size of mm × 15 mm is measured using a thermomechanical analyzer (TMA100, manufactured by Seiko Instruments Inc.) at a measurement temperature range of 0 to 320 ° C. and a heating rate of 5 ° C./min. Α1 and α2 were determined from the chart, and the intersection of the extended lines was defined as Tg. The unit is ° C. Heat shrinkage: Using a transfer molding machine, mold temperature 17
4mm x 5 ° C, injection pressure 9.8MPa, curing time 2 minutes
A test piece molded into a size of 4 mm × 15 mm was subjected to a thermomechanical analyzer (TMA100, manufactured by Seiko Instruments Inc.).
The measurement was carried out at a measurement temperature range of 0 to 320 ° C. and a heating rate of 5 ° C./min. Units%. Flexural modulus: measured in accordance with JIS K 6911 test conditions. The test piece was used at a mold temperature of 175 ° C. and an injection pressure of 9.
Molding was performed using a transfer molding machine at 8 MPa and a curing time of 2 minutes, and post-curing was performed at 175 ° C. for 8 hours to prepare. The test piece was placed on a measuring table (span width 64 mm), preheated in a bath maintained at the measuring temperature for 6 minutes, and then measured. The measurement temperatures were 25 ° C, 130 ° C, 140 ° C, and 175 ° C. The unit is N / mm ² . Warpage: Using a transfer molding machine, mold temperature 175
° C, injection pressure: 7.8 MPa, curing time: 2 minutes, 352 pB
GA (substrate is bismaleimide / triazine resin / glass cloth substrate having a thickness of 0.56 mm, semiconductor device size is 30 mm × 30 mm, thickness 1.17 mm, semiconductor element size is 20 mm × 20 mm, thickness 0.35 mm, The semiconductor element and the bonding pad of the circuit board are bonded with a gold wire having a diameter of 25 μm).
Post-cured in 8 hours. After cooling, the displacement in the height direction was measured diagonally from the gate of the semiconductor device using a surface roughness meter, and the largest value of the displacement was defined as the amount of warpage. Unit is μ
m. Water absorption: Using a transfer molding machine, mold temperature 175
° C, injection pressure 9.8MPa, curing time 2 minutes, diameter 50m
m, a disk having a thickness of 3 mm, and post-cured at 175 ° C. for 8 hours. The obtained molded product is left for 168 hours at an environment of 85 ° C. and a relative humidity of 60%. The rate was determined. The unit is% by weight. Solder crack resistance: 352 pBGA using a transfer molding machine at a mold temperature of 175 ° C., an injection pressure of 7.8 MPa, and a curing time of 2 minutes (substrate is 0.56 mm thick bismaleimide triazine resin / glass cloth substrate, semiconductor device) Has a size of 30 mm × 30 mm, a thickness of 1.17 mm, a size of a semiconductor element of 20 mm × 20 mm, and a thickness of 0.35 m
m, 25 bonding pads between the semiconductor element and the circuit board
Bonding is performed with a gold wire having a diameter of μm. The semiconductor device occupied area was 44.4%) and post-cured at 175 ° C. for 8 hours. After 10 semiconductor devices thus obtained were left in an environment of 85 ° C. and a relative humidity of 60% for 168 hours, IR reflow treatment (240 ° C.) was performed (hereinafter referred to as L2). The presence or absence of internal peeling and cracking after the treatment was observed with an ultrasonic flaw detector, and the number of defective semiconductor devices was counted. When the number of defective semiconductor devices is n, it is indicated as n / 10. Examples 2 to 7, Comparative Examples 1 to 3 Epoxy resin compositions were obtained and evaluated in the same manner as in Example 1 according to the formulations in Tables 1 and 2. Tables 1 and 2 show the evaluation results. The resins used in other than Example 1 are shown below. Phenol aralkyl resin 2 (manufactured by Mitsui Chemicals, Inc., XL
-225, softening point 62 ° C, hydroxyl equivalent 167) Triphenol methane type phenol resin (MEH-7500, manufactured by Meiwa Kasei Co., Ltd., softening point 110 ° C, hydroxyl equivalent 97) Silicone rubber 1 (Shore A hardness 30, maximum particle size) Diameter 10μ
m, average particle size 5 μm) [Table 2] According to the present invention, the area occupied by a semiconductor element with respect to the area of a semiconductor device is reduced to 40 using an epoxy resin composition having a specific Tg, flexural modulus and heat shrinkage characteristic.
%, The area-mount type semiconductor device in which the semiconductor element is sealed is less warped after molding or soldering, and is industrially useful.

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Claims (1)

Claims 1. A semiconductor device obtained by sealing a semiconductor element using the following epoxy resin composition has a semiconductor element area of 40% or more of the semiconductor device area. Area-mounted semiconductor device. An epoxy resin containing (A) an epoxy resin, (B) a phenol resin, (C) an inorganic filler, and (D) a curing accelerator as essential components, and containing 65 to 95% by weight of an inorganic filler in the entire epoxy resin composition. In the composition, the cured product of the epoxy resin composition has a glass transition temperature of less than 130 ° C. and a flexural modulus of less than 20,000 N / mm ² within a temperature range of 25 ° C. to “glass transition temperature + 5 ° C.” Temperature + 5 ° C ”to less than 8000 N / mm ² in the temperature range of 140 ° C, 1000 in the temperature range of 140 ° C to 175 ° C
An epoxy resin composition having an N / mm ^{2 of} less than 0.2% and a heat shrinkage from the glass transition temperature to 25 ° C. of less than 0.2%.