JPH1160901A - Epoxy resin composition and semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject composition that shows reduced warpage after molding or on the soldering treatment of the area-mounting package with excellent reliability by allowing the composition to include a specific epoxy resin, a specific curing agent, a curing accelerator and a specific powder. SOLUTION: (A) A crystalline epoxy resin melting at 50-150 deg.C, selected from a biphenyl type epoxy resin, a hydroquinone type epoxy resin of formula II, a stilbene type epoxy resin of formula III, and a bisphenol F type epoxy resin, (B) a phenolic resin type curing agent containing >=20 wt.% of a phenolic resin of formula V (m, n are each 1-10), (C) a curing accelerator as triphenyl phosphine, and (D) molten silica powder are used to give the objective composition that has preferably <=0.15% shrinkage out molding and curing, the coefficient of linear expansion α1 of 8-16 ppm/ deg.C after curing, the glass transition point of >=140 deg.C and the melt viscosity of <=150 poise at 175 deg.C before molding.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin-encapsulated semiconductor device having excellent moldability, reliability, and mountability. More specifically, a semiconductor device is mounted on one side of a printed wiring board or a metal lead frame. In a so-called area mounting type semiconductor device in which substantially only one side of the mounting surface is resin-sealed, the warpage after resin sealing and the warping in the soldering process at the time of board mounting are small, and in a temperature cycle test. Epoxy resin composition for semiconductor encapsulation which has excellent package crack resistance and package crack resistance and exfoliation resistance in a soldering process, and is excellent in moldability, and a semiconductor encapsulated with the epoxy resin composition for semiconductor encapsulation It concerns the device.

[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 semiconductors has been progressing year by year, and surface mounting of semiconductor packages has been promoted. Packaging packages have been developed and are beginning to move away from packages with traditional structures. Typical area mounting packages are BGA (ball grid array) or CSP (chip size package) pursuing further miniaturization, but these are approaching the limit in conventional surface mounting packages such as QFP and SOP. It has been developed to meet the demand for higher pin counts and higher speeds. The structure is as follows: a rigid circuit board represented by a BT resin / copper foil circuit board (bismaleimide / triazine / glass cloth board) or a flexible circuit board represented by a polyimide resin film / copper foil circuit board; An element is mounted, and only the element mounting surface, that is, one side of the substrate is molded and sealed with an epoxy resin composition or the like. In addition, a solder ball is formed two-dimensionally in parallel on the surface opposite to the element mounting surface of the substrate, and has a feature of joining with a circuit board on which a package is mounted. Furthermore,
As a substrate on which the element is mounted, a structure using a metal substrate such as a lead frame has been devised in addition to the organic circuit substrate.

[0003] The structure of these area mounting type semiconductor packages adopts a single-sided sealing form in which only the element mounting surface of the substrate is sealed with a 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 solder ball forming surface, but a sealing resin layer of several hundred μm to several mm on the element mounting surface. Since the layer is formed, one-sided sealing is substantially achieved. For this reason, due to the mismatch of thermal expansion and thermal contraction between the organic substrate or metal substrate and the cured product of the resin composition, or the effect of curing shrinkage during molding and curing of the resin composition, these packages cannot be molded. Warpage tends to occur immediately after. In addition, when soldering is performed on a circuit board on which these packages are mounted, a heating step of 200 ° C. or more is performed. At this time, package warpage occurs.
A large number of solder balls are not flattened and rise from the circuit board on which the package is mounted, which causes a problem that electrical connection reliability is reduced.

Further, when soldering is performed by soldering by means such as infrared reflow, vapor phase soldering, or solder immersion, moisture existing inside the package is rapidly vaporized at high temperature due to moisture absorption from the cured product and the organic substrate. Cracks may occur in the package due to the stress caused by this, and peeling may occur at the interface between the element mounting surface of the substrate and the cured product. Is also required. Further, due to the mismatch between the coefficient of linear expansion of the substrate and the cured product, peeling of the interface between the substrate and the cured product and package cracking occur even in a temperature cycle test, which is a typical example of a reliability test. Conventional QFP and S
For surface mount packages such as OP, to prevent cracks at the time of solder mounting and peeling at the interface between each material, crystalline epoxy resin such as biphenyl type epoxy resin and paraxylylene-modified phenol resin curing agent are typical. As a countermeasure, it has been attempted to reduce the viscosity during molding and increase the amount of the inorganic filler by using a flexible curing agent or a phenol resin and a combination thereof. However, at present, this method cannot solve the problem of warpage in a single-sided sealed package.

In a package in which substantially only one surface of a substrate is sealed with a resin composition, to reduce the warpage, the linear expansion coefficient of the substrate and the linear expansion coefficient of the cured resin composition must be close to each other. Two methods of reducing the cure shrinkage of the composition are important. As the substrate, in the case of an organic substrate, a resin having a high glass transition temperature such as a BT resin or a polyimide resin is widely used, and these have a glass transition temperature higher than around 170 ° C. which is a molding temperature of the epoxy resin composition. Accordingly, in the cooling process from the molding temperature to room contracts only alpha ₁ region of the organic substrate. Therefore, the resin composition is also the same as high and alpha ₁ is a circuit board glass transition temperature, warpage is considered to be substantially zero when further curing shrinkage is zero. Therefore, the glass transition temperature higher by a combination of a polyfunctional epoxy resin and a polyfunctional phenol resin, methods to adjust the alpha ₁ in the amount of the inorganic filler has been proposed.

However, a combination system of a polyfunctional epoxy resin having three or more epoxy groups in one molecule and a polyfunctional phenol resin having three or more phenolic hydroxyl groups in one molecule has a large moisture absorption. That, because each resin viscosity is high, it is not possible to highly fill the inorganic filler and it is difficult to reduce moisture absorption, showing high elasticity even at solder processing temperature,
Due to the high generated stress and the like, the occurrence of package cracks and the occurrence of interface peeling during the soldering process has not been solved. In addition, the gold wire used for electrical connection between the element and the substrate is as thin as tens of μm, and the length of the area mount package is longer than that of the conventional structure package. Due to the high density, the gold wires are deformed unless sealed with a low-viscosity resin composition at the time of molding, and the gold wires come into contact with each other to cause electrical failure. Especially CSP
In such a thin package as described above, it is an essential condition to seal with a resin composition having good filling properties and little deformation of the gold wire.

[0007]

SUMMARY OF THE INVENTION The present invention has a small warpage after molding in an area mounting package or during soldering, and has excellent reliability in a temperature cycle test or soldering.
The object of the present invention is to develop an epoxy resin composition for semiconductor encapsulation having a good filling property and a small deformation of a gold wire, that is, a high fluidity characteristic at the time of molding, and a semiconductor device sealed thereby. .

[0008]

Means for Solving the Problems As a result of intensive studies, the present inventor has found that a combination of a special crystalline epoxy resin and a polyfunctional phenol resin curing agent can reduce the moisture absorption while keeping the glass transition temperature from decreasing. It is possible to increase the filling amount of the inorganic filler because it is possible to achieve a low viscosity,
It is possible to lower moisture absorption and alpha ₁ adjustment, also be possible to reduce the filling improvement and wire deformation amount at the time of molding, the generated stress because it thermal time elastic modulus reduction at soldering temperature decreases, It is clarified that the adhesion to a circuit board is improved.

That is, the present invention relates to (A) a compound represented by the general formula (1):
(B) a crystalline epoxy resin having a melting point of 50 to 150 ° C. represented by (4), (B) a phenol resin curing agent containing at least 20% by weight of the total phenol resin represented by the general formula (5), and (C) curing An epoxy resin composition for semiconductor encapsulation, comprising an accelerator and (D) fused silica powder. More preferably, the curing shrinkage during molding and curing is 0.15% or less, and the linear expansion after curing. coefficient α ₁ is 8~16p
An epoxy resin composition for semiconductor encapsulation, wherein the resin viscosity at pm / ° C., the glass transition temperature is 140 ° C. or more, and the resin viscosity at 175 ° C. before molding is 150 poise or less, and the epoxy resin composition for semiconductor encapsulation It is a semiconductor device sealed with an object.

[0010]

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, which may be the same or different. ]

[0011]

Embedded image [R in the formula (5) is a hydrogen atom, a halogen atom,
And 12 to 12 alkyl groups or hydroxyl groups, which may be the same or different. m and n are positive integers of 1 to 10. ]

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
The (A) crystalline epoxy resin having a melting point of 50 to 150 ° C. used in the present invention is a diepoxy resin having two epoxy groups in one molecule. Since all of these epoxy resins show crystallinity, they are solid at a temperature lower than the melting point, but become a low-viscosity liquid material at a temperature higher than the melting point. For this reason, in the case of a crystalline epoxy resin having a melting point of less than 50 ° C., fusion tends to occur in the production process of the epoxy resin composition, and workability is significantly reduced. In addition, a crystalline epoxy resin having a melting point exceeding 150 ° C. has a problem that the uniformity of the material is poor because the epoxy resin composition is not sufficiently melted in a manufacturing process of kneading under heating. As a method for measuring the melting point, a differential scanning calorimeter [SSC manufactured by Seiko Denshi Co., Ltd.
/ 5200] (heat-up rate of 5 ° C / min).

Examples of the crystalline epoxy resin having a melting point of 50 to 150 ° C. include a biphenyl epoxy resin of the formula (1), a hydroquinone epoxy resin of the formula (2), a stilbene epoxy resin of the formula (3), and a formula (4) Bisphenol F
Type epoxy resins are particularly preferred. Specific examples of these crystalline epoxy resins are shown below, but the invention is not limited thereto.

[0014]

Embedded image

[0015] These crystalline epoxy resins have a small number of epoxy groups in one molecule of two, and can be used alone to obtain a cured product having a low crosslinking density and low heat resistance. However, it has a rigid planar or rod-like skeleton as a structure, and has the property of being crystallized, that is, the molecules are easily oriented. Since the resin composition has a low viscosity in a molten state, the fluidity of the resin composition during molding is high, and the filling property into a thin package is particularly excellent. In addition, due to the feature of being structurally rigid and easy to be oriented, when cured with a polyfunctional phenol resin, it is difficult to lower the heat resistance such as the glass transition temperature even if the crosslink density of the crosslinked structure is reduced. On the other hand, when a normal bifunctional non-crystalline epoxy resin is used in combination with a polyfunctional phenol resin, only the crosslinking density is reduced, and the glass transition temperature is significantly reduced. Furthermore, in the case of a crystalline epoxy resin, a low elastic modulus characteristic of a compound having a low number of functional groups is exhibited in a temperature region once exceeding the glass transition temperature, so that it is effective in reducing stress at a soldering temperature. This has the effect of preventing the occurrence of package cracks in the soldering process and the occurrence of peeling at the interface between the substrate and the resin composition.

The epoxy resin of the present invention may be used in combination with another epoxy resin. Epoxy resins that can be used in combination include all monomers, oligomers, and polymers having an epoxy group, such as bisphenol A epoxy resin, orthocresol novolac epoxy resin, and naphthol epoxy resin. or,
These epoxy resins may be used alone or in combination.

Specific examples of the phenol resin curing agent represented by the formula (5) used in the present invention are shown below.

Embedded image

When these phenolic resins are used, the crosslink density of the cured product is increased, and a cured product having a high glass transition temperature is obtained. The amount of the phenolic resin used is at least 20% by weight based on the balance of the glass transition temperature. It is necessary to. If it is less than 20% by weight, the glass transition temperature decreases, the curing shrinkage increases, and the amount of warpage of the molded package increases. These phenolic resins can be appropriately used in combination with other phenolic resins, and are not particularly limited. Examples thereof include phenol novolak resins, cresol novolak resins, and naphthol novolak resins.

The curing accelerator of the component (C) used in the present invention refers to those which can be a catalyst for a crosslinking reaction between the epoxy resin and the phenol resin curing agent, and specifically, an amine compound such as tributylamine. And organic phosphorus compounds such as triphenylphosphine and tetraphenylphosphonium / tetraphenylborate, and imidazole compounds such as 2-methylimidazole, but are not limited thereto. These curing accelerators may be used alone or as a mixture.

The fused silica powder (D) used in the present invention can be used in any of a crushed form and a spherical form. However, the amount of the fused silica powder is increased and the melt viscosity of the resin composition is increased. In order to suppress this, it is preferable to mainly use 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 resin composition of the present invention may be, if necessary, a brominated epoxy resin, a flame retardant such as antimony trioxide, a coupling agent, or carbon black, in addition to the essential components (A) to (E). Coloring agents, release agents such as natural waxes and synthetic waxes, etc., can be appropriately compounded. In order to obtain a resin composition, the components are mixed, heated and kneaded with a heating kneader or a hot roll, and then cooled and pulverized to obtain a desired resin composition. In addition, using the epoxy resin composition of the present invention to encapsulate electronic components such as semiconductors and manufacture semiconductor devices, curing molding is performed by a conventional molding method such as transfer molding, compression molding, or injection molding. do it.

The semiconductor device of the present invention uses BT as an organic substrate.
When a resin substrate is used, the epoxy resin composition has a cured linear expansion coefficient (α ₁ ) of 8 to 16 ppm / ° C., a glass transition temperature of 140 ° C. or higher measured by a thermomechanical analyzer, and a curing shrinkage of 0. It is particularly preferable that the melt viscosity at 175 ° C. is 150 poise or less.
The linear expansion coefficient of the BT resin substrate is about 14 ppm / ° C., but in a composite substrate in which a metal such as a silicon chip or a copper foil circuit is combined, the linear expansion coefficient is determined by the area ratio of the chip and the area ratio of the copper foil circuit. The coefficient changes. By setting the linear expansion coefficient and the curing shrinkage ratio of the cured product of the resin composition in the above ranges together with the linear expansion coefficient of the substrate, the resin composition can be adjusted according to the heat shrinkage from the molding temperature of the BT resin substrate to room temperature. The heat shrinkage of the cured product becomes almost the same, and the warpage after molding can be reduced. Here, the curing shrinkage ratio refers to the ratio between the size of the mold at the molding temperature and the size of the molded product at the molding temperature.

In the present invention, the glass transition temperature, the coefficient of linear expansion,
The cure shrinkage is measured by the following method. Glass transition temperature (Tg) and coefficient of linear expansion (α ₁ ): 17
The test piece obtained by transfer molding at 5 ° C. for 2 minutes was further cured at 175 ° C. for 8 hours, and measured with a thermomechanical analyzer [TMA-120, manufactured by Seiko Denshi Co., Ltd., heating rate 5 ° C./min]. Curing shrinkage: 180 ° C mold temperature of test piece, 7
Transfer molding was performed at an injection pressure of 5 kg / cm ² for 2 minutes, and post-curing was further performed at 175 ° C. for 8 hours. The cavity dimensions of the mold heated to 180 ° C. and the dimensions of the molded article heated to 180 ° C. were measured with calipers, and the curing shrinkage was represented by the ratio of molded article dimension / mold cavity dimension. -Melt viscosity The melt viscosity was measured at 175 ° C under a load of 10 kg with a high-grade flow tester manufactured by Shimadzu Corporation.

[0024]

The present invention will be specifically described below with reference to examples. << Example 1 >> Biphenyl type epoxy resin having a structure of the above formula (6) as a main component [YX-4000H, melting point 105 ° C, epoxy equivalent 195, manufactured by Yuka Shell Epoxy Co., Ltd.] 8.2 parts by weight Phenolic resin represented by the formula (11) [MEH-750, manufactured by Meiwa Kasei Co., Ltd., softening point 72 ° C, hydroxyl equivalent 138] 5.8 parts by weight Triphenylphosphine 0.2 parts by weight Spherical fused silica 85.0 parts by weight ・ Carnauba wax 0.5 parts by weight ・ Carbon black 0.3 parts by weight After all the above components were mixed by a mixer, the mixture was kneaded 30 times using two rolls having a surface temperature of 90 ° C. and 45 ° C. The obtained kneaded material sheet was cooled and pulverized to obtain a resin composition. The properties of the obtained resin composition were evaluated by the following methods. Table 1 shows the evaluation results.

The properties of the epoxy resins of the formulas (7) to (10) used in the examples and comparative examples are shown below.・ Epoxy resin having a structure of formula (7) as a main component: [melting point 144 ° C., epoxy equivalent 175] ・ Epoxy resin having a structure of formula (8) as a main component: [melting point 52 ° C., epoxy equivalent 225] ・ Formula Epoxy resin having a structure of (9) as a main component: [melting point 82 ° C., epoxy equivalent 190] ・ Epoxy resin having a structure of the formula (10) as a main component: [liquid, viscosity (25 ° C.) 55 Poise, epoxy equivalent 168] Orthocresol novolak epoxy resin: [EOCN-1020 manufactured by Nippon Kayaku Co., Ltd., softening point 62 ° C, epoxy equivalent 200] Paraxylylene-modified phenolic resin: [Meiwa Kasei Co., Ltd.]
MEH-7800, softening point 78 ° C, epoxy equivalent 1
75] ・ Phenol novolak resin: [Gunei Chemical Industry Co., Ltd.
PSM-4261, softening point 81 ° C, equivalent 104

<< 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. Glass transition temperature (Tg) and coefficient of linear expansion (α ₁ ): According to the method described above.・ Heat elastic modulus: Flexural elastic modulus at 240 ° C is JIS-K6
It was measured under the test conditions of 911. Curing shrinkage: According to the method described above. Melt viscosity: According to the method described above. Package warpage: 225-pin BGA package (substrate is a 0.36 mm thick BT resin substrate, package size is 24 × 24 mm, thickness 1.17 mm, silicon chip is 9 × 9 mm, thickness 0.35 mm, chip and circuit board Is bonded with a gold wire having a diameter of 25 μm) at a mold temperature of 180 ° C. and 75 kg /
perform transfer molding for 2 minutes at an injection pressure of cm ^2,
Further post-curing was performed at 175 ° C. for 8 hours. After cooling to room temperature, the displacement in the height direction was measured diagonally from the gate of the package using a surface roughness meter, and the value with the largest variation difference was defined as the amount of warpage. Solder Resistance: The molded product package used for measuring the package warpage was left for 168 hours in an environment of 85 ° C. and 60% relative humidity, and then immersed in a 240 ° C. solder bath for 10 seconds.
The package was observed using an ultrasonic flaw detector, and the number of internal cracks and the number of peels at the interface between the substrate and the resin composition were represented by% of (number of generated packages) / (total number of packages). Gold wire deformation rate: 225 molded by evaluating package warpage
The pin BGA 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) in%.

<< Examples 2 to 5 and Comparative Examples 1 to 4 >> Compounded according to the formulations shown in Tables 1 and 2, a molding material was obtained in the same manner as in Example 1. This molding material was evaluated in the same manner as in Example 1. Table 1 shows the evaluation results.

[0028]

[Table 1]

[0029]

The epoxy resin composition for semiconductor encapsulation of the present invention is also excellent in moldability such as gold wire deformation, and the area mounting type semiconductor device sealed with the epoxy resin composition for semiconductor encapsulation can be used at room temperature. Also, the warpage in the soldering process is small, and the reliability such as solder resistance and temperature cycle resistance is high.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C08K 3/36 C08K 3/36 H01L 23/29 H01L 23/30 R 23/31

Claims (4)

[Claims] 1. A crystalline epoxy resin having a melting point of 50 to 150 ° C. represented by the general formulas (1) to (4), and (B) a phenolic resin represented by the general formula (5) in the total phenolic resin. A phenolic resin curing agent containing at least 20% by weight of
An epoxy resin composition for semiconductor encapsulation comprising (C) a curing accelerator and (D) a fused silica powder. 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, which may be the same or different. ] [R in the formula (5) is a hydrogen atom, a halogen atom,
And 12 to 12 alkyl groups or hydroxyl groups, which may be the same or different. m and n are positive integers of 1 to 10. ] 2. The composition has a curing shrinkage of 0.15% or less during molding and curing, a linear expansion coefficient α1 after curing of ₈ to 16 ppm / ° C.,
The epoxy resin composition for semiconductor encapsulation according to claim 1, wherein the glass transition temperature is 140 ° C or higher. 3. The melt viscosity at 175 ° C. before molding is 1
The epoxy resin composition for semiconductor encapsulation according to claim 1 or 2, wherein the epoxy resin composition is 50 poise or less. 4. 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, 2 or 3. A semiconductor device.