JP3292456B2 - Epoxy resin composition and semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an epoxy resin composition for semiconductor encapsulation and a resin-encapsulated semiconductor device having excellent moldability, reliability, and mountability, and more particularly to a printed wiring board and a metal lead frame. The semiconductor element is mounted on one side of
In a so-called area mounting type semiconductor device in which only one surface on the mounting surface side 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. The present invention relates to an epoxy resin composition for semiconductor encapsulation, which has excellent package crack resistance and package crack resistance and peeling resistance in a soldering step, and is excellent in moldability, and a semiconductor 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. A typical area mounting package is a BGA (ball grid array) or a CSP (chip size package) pursuing further miniaturization.
The surface-mount package represented by is developed to meet the demand for higher pin count and higher speed, which is approaching the limit. 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. Also, on the surface opposite to the element mounting surface of the substrate, solder balls are formed two-dimensionally in parallel so as to be joined to a circuit board on which a package is mounted. Further, a structure using a metal substrate such as a lead frame other than the organic circuit substrate has been devised as a substrate on which the element is mounted.

[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, warpage of the package occurs, and a large number of solder balls do not become flat, and the package is mounted. There is also a problem that the semiconductor device floats from the circuit board to be mounted and lowers the reliability of electrical connection. In a package in which substantially only one surface on a substrate is sealed with a resin composition, in order to reduce warpage, the linear expansion coefficient of the substrate and the linear expansion coefficient of a cured product of the resin composition are brought close to each other, and the resin composition There are two important ways to reduce the cure shrinkage. As a substrate, in 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 an epoxy resin composition. . Accordingly, in the cooling process from the molding temperature to room contracts only alpha ₁ region of the organic substrate.
The resin composition is also the same as the high and alpha ₁ is a circuit board glass transition temperature, warping if further cure shrinkage is zero is considered to be almost 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.

When soldering is performed by soldering by means such as infrared reflow, vapor phase soldering, or solder immersion, moisture present inside the package due to moisture absorption from the cured resin composition and the organic substrate is high. Cracks in the package due to stress caused by rapid vaporization in the package, and peeling at the interface between the device mounting surface of the substrate and the cured product of the resin composition, resulting in a low stress and low moisture absorption of the cured product. With the development, the adhesion to the substrate is also required. Furthermore, due to the mismatch between the thermal expansion coefficient of the substrate and the cured product,
In a temperature cycle test, which is a typical example of a reliability test, peeling of the interface between the substrate and the cured product and cracking of the package occur. Conventional surface mount packages such as QFP and SOP use a crystalline epoxy resin typified by a biphenyl-type epoxy resin and a flexible skeleton to prevent cracks at the time of solder mounting and peeling at each material interface. By using a phenolic resin curing agent in combination and increasing the blending amount of an inorganic filler, measures have been taken to lower the glass transition temperature and lower the moisture absorption. However, at present, this method cannot solve the problem of warpage in a single-sided sealed package.

Further, in a semiconductor package for area mounting, an epoxy resin composition is molded and sealed on substantially only one surface (device mounting surface) of the substrate. A solder resist layer is formed on the device mounting surface of the substrate. That is common. This solder resist is formed on the surface to ensure insulation and protect the copper foil circuit on the substrate. For this reason, the epoxy resin composition is also formed on the surface of the solder resist. However, the solder resist contains a silicone-based additive for imparting its surface smoothness and defoaming effect, which bleeds out to the surface of the solder resist layer. Significantly lowers the adhesive strength. The decrease in the adhesive strength has caused a problem that a large amount of moisture can enter in the moisture absorption treatment of the package, leading to release of many ionic impurities, accelerating the corrosion of aluminum circuits and the like, and greatly reducing the reliability.

[0006]

DISCLOSURE OF THE INVENTION The present invention has low warpage after molding in an area mounting package or during soldering, and has particularly excellent adhesiveness to a substrate, so that reliability in a temperature cycle test, soldering, etc. The object of the present invention is to develop an epoxy resin composition for semiconductor encapsulation which is excellent in moisture resistance and a semiconductor device in which a semiconductor element is encapsulated thereby.

[0007]

The present invention relates to (A) a polyfunctional epoxy resin represented by the general formulas (3) and (4) and / or a polyfunctional epoxy resin represented by the formulas (5) to (9) and having a melting point of: 50-150
At least one epoxy resin selected from the group of crystalline epoxy resins at ℃, (B) a phenolic resin curing agent represented by the general formula (1), (C) a curing accelerator, (D) fused silica powder, and ( E) An epoxy resin composition for semiconductor encapsulation, characterized in that the total epoxy resin composition contains 0.05 to 5% by weight of a bismuth compound represented by the general formula (2), and a semiconductor element is encapsulated thereby. Semiconductor device.

[0008]

Embedded image _{Bi x O y (OH) p} (Y -a) q (NO 3) r · nH 2 O (2)

[0009]

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[0010]

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[0011]

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[R in the formulas (1), (3), (4) and (9) represents a halogen atom or an alkyl group having 1 to 12 carbon atoms, and may be the same or different. Good.
l is a positive number of 1 to 10, m is a positive integer of 0 or 1 to 3, and n is 0 or a positive integer of 1 to 4. ]
[R in the formulas (5) to (8) represents a hydrogen atom, a halogen atom or an alkyl group having 1 to 12 carbon atoms, and may be the same or different. In the formula (2), ^Ya represents an oxyacid residue other than a nitric acid group, a represents an ionic value (absolute value) of the oxyacid residue, and when q = 0, x = y = 6, 3.5 ≦ p ≦ 5.5, and n is 0
Or a positive number. When q ≠ 0, x, y, p, q, r, and n are values that satisfy the following equations. x ≧ 1, y ≧ 1, n ≧ 0, 0.08x ≦ p ≦ 0.92
x, 0.02x ≦ a, q ≦ 0.92x, 0 ≦ r ≦ 0.1
x, 3x = 2y + p + q + r]

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
Among the epoxy resins of the component (A) used in the present invention, a resin generally referred to as a triphenolmethane epoxy resin represented by the formula (3) or an epoxy resin represented by the formula (4) is represented by the following formula (1). In combination with a phenolic resin curing agent, the crosslinked density of the cured product is high, the glass transition temperature is high, and the curing shrinkage is small. It is effective in reducing warpage. Specific examples of the formulas (3) and (4) include the following, but are not limited thereto.

[0014]

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[0015]

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The crystalline epoxy resin represented by the formulas (5) to (9) and having a melting point of 50 to 150 ° C. is a diepoxy compound having two epoxy groups in one molecule or an oligomer thereof. 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, the epoxy resin composition using these has a low viscosity in a molten state, so that the fluidity of the resin composition at the time of molding is high, and the filling property into a thin package is excellent. Therefore, it is preferable to use these crystalline epoxy resins when increasing the amount of the fused silica powder to reduce the moisture absorption of the cured product of the obtained epoxy resin composition and improving the solder reflow resistance. . These crystalline epoxy resins have as few as two epoxy groups in one molecule, and generally have only a low crosslink density and a cured product with low heat resistance. However, since it has a rigid plane or rod-like skeleton as a structure and has the property of being crystallized, that is, the feature that molecules are easily oriented, the polyfunctional phenol resin curing agent represented by the general formula (1) is used. When used in combination, it is difficult to lower the heat resistance such as the glass transition temperature after curing. For this reason, the semiconductor package sealed with the epoxy resin composition by the combination of the crystalline epoxy resin and the phenol resin curing agent represented by the general formula (1) can reduce the amount of warpage. Further, in a temperature region once exceeding the glass transition temperature, the compound exhibits a low elastic modulus characteristic of a compound having a low functional group, which is effective for reducing stress at a solder processing temperature. This has the effect of preventing the occurrence of package cracks during the soldering process and the occurrence of separation at the interface between the substrate and the resin composition. If the crystalline epoxy resin has a melting point of less than 50 ° C., it tends to fuse in the production process of the epoxy resin composition, and the workability is significantly reduced. Further, a crystalline epoxy resin having a melting point exceeding 150 ° C. has a problem that the uniformity of the material is inferior because the epoxy resin composition is not sufficiently melted in the production step of kneading under heating. The melting point can be measured by a differential scanning calorimeter [Seiko Electronics Co., Ltd. SSC520, heating rate 5 ° C. /
Min] from the endothermic peak temperature. Hereinafter, specific examples of these crystalline epoxy resins are shown, but are not limited thereto.

[0017]

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[0018]

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[0019]

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[0020]

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Further, from the viewpoint of reducing package warpage, increasing fluidity during molding, and achieving solder resistance during mounting, the polyfunctional epoxy resins represented by the general formulas (3) and (4) are all used. It is particularly preferable that the total epoxy resin contains 20 to 90% by weight in the epoxy resin and further contains a crystalline epoxy resin represented by the formulas (5) to (9) and having a melting point of 50 to 150 ° C in the total epoxy resin. preferable. The epoxy resin used in the present invention can be appropriately used in combination with other epoxy resins and is not particularly limited. For example, in addition to the above, bisphenol F type epoxy resin, bisphenol A type epoxy resin, orthocresol novolak type Epoxy resins, naphthol type epoxy resins and the like can be mentioned. These epoxy resins may be used alone or as a mixture.

Formula (1) of the component (B) used in the present invention
Is a so-called triphenolmethane-type phenol resin, and specific examples are shown below, but are not limited thereto.

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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 can be obtained. For this reason, the warpage of the package sealed with the obtained epoxy resin composition can be reduced. The phenolic resin of the formula (1) can be appropriately used in combination with other phenolic resins, and is 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 includes amine compounds 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 of the component (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 bismuth compound of the component (E) used in the present invention can be represented by the general formula (2), and it is essential that the molecule has a bismuth nitrate group in the molecule. Y ^-a in the general formula (2) represents an oxyacid residue other than a nitric acid group, for example, a carboxylic acid such as carbonic acid, bicarbonate, metasilicic acid, orthosilicic acid, metaboric acid, orthoboric acid, phosphoric acid, or oxalic acid In addition, those obtained by combining two or more of these or using them in combination are also included. In general, the addition of a hydrated metal compound to an epoxy resin composition has the effect of supplementing ionic impurities of the epoxy resin composition and preventing corrosion of semiconductor circuits.By introducing a bismuth nitrate group, With a dramatic increase in the capture rate of ionic impurities,
Further, the following effects are obtained.

By adding the bismuth compound represented by the general formula (2) to the epoxy resin composition, ionic impurities released during moisture absorption can be quickly captured.
Reduces corrosion of aluminum circuits and improves package reliability. The compounding amount of the bismuth compound is 0.05 to 5% by weight in the total epoxy resin composition, and the compounding amount is 0.05% by weight.
If it is less than 5%, the reliability is not improved. If it exceeds 5% by weight, the spiral flow of an important element at the time of molding is lowered, which is not preferable.

The resin composition of the present invention is represented by a brominated epoxy resin, a flame retardant such as antimony trioxide, a coupling agent, and carbon black, if necessary, 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. Using the epoxy resin composition of the present invention to encapsulate electronic components such as semiconductors and manufacture semiconductor devices, transfer molding, compression molding, and injection molding can be performed by conventional molding methods such as injection molding. Good.

[0029]

The present invention will be specifically described below with reference to examples. << Example 1 >> An epoxy resin having a structure represented by the formula (10) as a main component: [manufactured by Yuka Shell Epoxy Co., Ltd., trade name Epicoat 1032H, softening point 60 ° C, epoxy equivalent 170] 4.6 weight Part: Biphenyl-type epoxy resin having a structure represented by the formula (11) as a main component: [YX-4000H, manufactured by Yuka Shell Epoxy Co., Ltd., melting point 105 ° C, epoxy equivalent 195] 4.6 parts by weight A phenolic resin represented by the formula (12): [Mehka Kasei Co., Ltd., trade name MEH-7500, softening point 107 ° C, hydroxyl equivalent 97] 4.8 parts by weight Bismuth compound represented by the formula (13) 0.5 parts by weight Triphenylphosphine 0.2 parts by weight Spherical fused silica 84.5 parts by weight Carnauba wax 0.5 parts by weight Carbon black 0.3 parts by weight After more mixed, the surface temperature is 30 times kneaded using two rolls 90 ° C. and 45 ° C., the kneaded product sheet obtained by pulverizing after cooling to obtain a resin composition. The properties of the obtained resin composition were evaluated by the following methods. Table 1 shows the evaluation results.

[0030]

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[0031]

Embedded image Bi ₆ O ₆ (OH) ₃ (NO ₃ ) _2.4 · 1.1 H ₂ O (13)

<< Examples 2 and 3 >> Based on Example 1, the amount of the bismuth compound was changed, and the amount of the change was adjusted by the amount of fused silica. It was blended and mixed and kneaded in the same manner as in Example 1 to obtain a resin composition. Evaluation was performed in the same manner as in Example 1. Table 1 shows the formulation and evaluation results. << Examples 4 to 10 >> Same as Example 1 except that the basic composition of Example 1 was used, and the types of the epoxy resin and the phenol resin and the amounts thereof were changed. To obtain a resin composition. Evaluation was performed in the same manner as in Example 1. The formulations and evaluation results are shown in Tables 1 and 2. << Examples 11 and 12 >> Using Example 1 as a basic composition, changing the type of bismuth compound, and otherwise blending each component at the same ratio as the basic composition, mixing and kneading in the same manner as in Example 1 to obtain a resin composition. I got something. Evaluation was performed in the same manner as in Example 1. Table 3 shows the formulation and evaluation results. << Comparative Examples 1 to 4 >> Based on Example 1, the components were mixed in the same proportions as the basic compound by changing the amount and type of bismuth compound, and mixed and kneaded in the same manner as in Example 1. Thus, a resin composition was obtained. Evaluation was performed in the same manner as in Example 1. Table 3 shows the formulation and evaluation results.

The formula (1) used in the above Examples and Comparative Examples
The structures of the epoxy resins of 4) to (18), the phenol resin of the formula (19) and the bismuth compounds of the formulas (20), (21) and (22) are shown below.

[0034]

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[0035]

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[0036]

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Bi ₆ O ₆ (OH) _3.13 (HCO ₃ ) _2.35 (NO ₃ ) _0.52 · 0.62 H ₂ O (20) Bi ₆ O ₆ (OH) _5.1 (NO ₃ ) _0.9 · 0.6 H ₂ O (21) _{Bi 6 O 6 (OH) 0.01} (HCO 3) 6 · 0.76H 2 O (22)

An epoxy resin having a structure represented by the formula (14) as a main component: melting point 144 ° C., epoxy equivalent 175 ・ an epoxy resin having a structure represented by the formula (15) as a main component: melting point 103 ° C., epoxy equivalent 225 ・ Epoxy resin having a structure represented by formula (16) as a main component: melting point 133 ° C., epoxy equivalent 182 ・ Epoxy resin having a structure represented by formula (17) as a main component: melting point 82 ° C., epoxy equivalent 190 ・Epoxy resin having a structure represented by formula (18) as a main component: melting point 65 ° C., epoxy equivalent 210 ・ phenol resin of formula (19): softening point 80 ° C., hydroxyl 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 ): 1
The test piece obtained by transfer molding at 75 ° C. for 2 minutes was post-cured at 175 ° C. for 8 hours, and measured by a thermomechanical analyzer [TMA-120 manufactured by Seiko Denshi Co., Ltd., heating rate 5 ° C./min].・ Heat elastic modulus: Flexural elastic modulus at 240 ° C is JIS-K6
It was measured according to 911. 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.

Package warpage: 225-pin BGA package (substrate 0.36 mm thick, bismaleimide
Triazine / glass cloth substrate, package size 2
4 × 24 mm, thickness 1.17 mm, silicon chip size 9 × 9 mm, thickness 0.35 mm, the chip and the bonding pad of the circuit board are bonded with a gold wire having a diameter of 25 μm). 75kg / cm
Perform transfer molding for 2 minutes at ² injection pressure, 8 hours at 175 ° C., and post-cured. 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. Moisture resistance: 1000 in an atmosphere of 125 ° C. and 2.3 atm.
The test was conducted until the time, and the open failure of the IC (16pDIP) was measured. Gold wire deformation: 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%.

[0041]

[Table 1]

[0042]

[Table 2]

[0043]

[Table 3]

[0044]

The epoxy resin composition for semiconductor encapsulation of the present invention has a small warpage in the area mounting type semiconductor device using the same at room temperature and in the soldering process, and is particularly excellent in the ability to trap ionic impurities. Therefore, it is excellent in reliability such as moisture resistance.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI H01L 23/31 (56) References JP-A-2-294354 (JP, A) JP-A-4-258624 (JP, A) JP-A-5-259315 (JP, A) JP-A-6-25384 (JP, A) JP-A-6-100657 (JP, A) JP-A-7-173373 (JP, A) JP-A-8-213518 (JP JP, A) JP-A-8-316374 (JP, A) JP-A-9-52228 (JP, A) JP-A-9-124901 (JP, A) JP-A-9-176278 (JP, A) (58) ) Surveyed field (Int.Cl. ⁷ , DB name) H01L 23/28-23/31 C08G 59/20 C08G 59/62 C08K 3/00 C08L 63/00

Claims (2)

(57) [Claims] 1. A polyfunctional epoxy resin represented by the general formulas (3) and (4) and / or a crystalline epoxy represented by the formulas (5) to (9) and having a melting point of 50 to 150 ° C. At least one epoxy resin selected from the group of resins, (B)
A phenolic resin curing agent represented by the general formula (1), (C)
A semiconductor encapsulation characterized in that the curing accelerator, (D) fused silica powder, and (E) the total epoxy resin composition contain 0.05 to 5% by weight of a bismuth compound represented by the general formula (2). Epoxy resin composition. Embedded image _{Bi x O y (OH) p} (Y -a) q (NO 3) r · nH 2 O (2) ## STR2 ## Embedded image Embedded image [R in the formulas (1), (3), (4) and (9) represents a halogen atom or an alkyl group having 1 to 12 carbon atoms, and may be the same or different. l is 1 to 10
Is a positive integer of 0 or 1 to 3, and n is a positive integer of 0 or 1 to 4. [R in the formulas (5) to (8) represents a hydrogen atom, a halogen atom or an alkyl group having 1 to 12 carbon atoms, and may be the same or different. In the formula (2), ^Ya represents an oxyacid residue other than a nitric acid group, a represents an ionic value (absolute value) of the oxyacid residue, and when q = 0, x = When y = 6, 3.5 ≦ p ≦
5.5, where n is 0 or a positive number. If q ≠ 0,
x, y, p, q, r, and n are values that satisfy the following equations. x ≧ 1, y ≧ 1, n ≧ 0, 0.08x ≦ p ≦ 0.92
x, 0.02x ≦ a, q ≦ 0.92x, 0 ≦ r ≦ 0.1
x, 3x = 2y + p + q + r] 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. Semiconductor device.