JPH11302502A - Semiconductor device and epoxy resin composition for semiconductor encapsulation used therein - Google Patents

Abstract

(57) [Problem] To provide a semiconductor device having good adhesion between a lead frame and a cured resin for encapsulation and excellent in solder heat resistance. A semiconductor element mounted on a lead frame is sealed with an epoxy resin composition containing the following components (A) to (D). (A) Epoxy resin. (B) a phenolic resin. (C) an inorganic filler. (D) an aluminum chelate compound having a phosphate ester structure in the molecule.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a resin-sealed semiconductor device sealed with an epoxy resin composition, and more particularly to a semiconductor device excellent in solder heat resistance.

[0002]

2. Description of the Related Art Semiconductor devices such as transistors, ICs and LSIs are usually sealed by transfer molding using an epoxy resin composition. A typical example of this type of package is a dual in-line package (DIP). This DIP is of a pin insertion type, and is attached to a mounting board by inserting pins into the board.

However, as electronic devices have become smaller, lighter, and more sophisticated in recent years, the mounting density has been increased, and the surface mounting of semiconductor packages has been promoted.

[0004]

However, in a semiconductor device using the above surface mount type package,
Especially when the package itself has absorbed moisture before surface mounting, the vapor pressure of the absorbed moisture vaporized during solder mounting
There is a problem that cracks occur in the package.

As a countermeasure against such a problem, a method of reducing the moisture absorption of the package by lowering the moisture absorption of the resin skeleton and increasing the filling amount of the filler, or a method of curing the lead frame and the sealing resin by adding a silane compound. Although a method for improving the adhesiveness of the interface with an object has been proposed, satisfactory results have not yet been obtained. In recent years, lead-plated lead frames made of palladium have been applied from the viewpoint of shortening and rationalizing the manufacturing process of semiconductor devices and protecting the global environment by not using lead solder. In particular, the adhesiveness to the cured resin for sealing is not sufficient, which is a cause of deteriorating solder heat resistance.

The present invention has been made in view of such circumstances, and a semiconductor device having good adhesion between a lead frame and a cured resin for encapsulation and having excellent heat resistance for soldering and an epoxy for semiconductor encapsulation used therefor. The purpose is to provide a resin composition.

[0007]

In order to achieve the above object, the present invention provides an epoxy resin composition containing the following components (A) to (D) mounted on a lead frame. A first gist is a semiconductor device in which a semiconductor element is sealed. (A) Epoxy resin. (B) a phenolic resin. (C) an inorganic filler. (D) an aluminum chelate compound having a phosphate ester structure in the molecule.

A second aspect of the present invention is an epoxy resin composition for semiconductor encapsulation containing the above components (A) to (D).

That is, the present inventors have studied a sealing material to achieve the above object. Then, for the purpose of preventing the occurrence of package cracks during mounting, the research was repeated mainly on the improvement of the adhesiveness between the epoxy resin composition cured product as the sealing resin and the lead frame. as a result,
The present invention has been found that, when the specific aluminum chelate compound as the component (D) is used as the epoxy resin composition as the material for forming the cured sealing resin, the adhesion to the lead frame is improved and effective. Reached.

And among the above-mentioned lead frames,
It has been found that it exhibits excellent adhesiveness to a lead frame, which is frequently used in recent years and has an Au plating layer formed on the outermost layer. Similarly, an Au plating layer is formed on the outermost layer, and a lower layer adjacent to the Au plating layer has a Pd plating layer and exhibits excellent adhesiveness that cannot be obtained with a conventional sealing material. I figured it out.

[0011]

Next, embodiments of the present invention will be described in detail.

The epoxy resin composition for semiconductor encapsulation of the present invention comprises an epoxy resin (component A), a phenol resin (component B), an inorganic filler (component C), and a specific aluminum chelate compound (component D). And is usually in the form of a powder or a tablet obtained by compressing the powder.

Epoxy resin (A component) used in the present invention
Is not particularly limited, and a commonly used epoxy resin is used. For example, various epoxy resins such as cresol novolak type, phenol novolak type, bisphenol A type, biphenyl type and naphthalene type, and brominated epoxy resins can be used. These can be used alone or in combination of two or more. Above all,
From the viewpoint of low hygroscopicity, it is preferable to use a biphenyl type epoxy resin.

The phenolic resin (component B) used together with the epoxy resin (component A) has a function as a curing agent for the epoxy resin, and refers to a resin having a failing hydroxyl group. Those having a measured melt viscosity at 150 ° C. of 5 poise or less are preferably used. Such a phenol resin is not particularly limited, and examples thereof include a phenol novolak resin, a novolak resin such as a cresol novolak resin, a xylylene-modified phenol resin, a terpene-modified phenol resin, and a dicyclopentadiene-modified phenol resin. . These phenolic resins can be used alone or in combination of two or more. Among these phenol resins, it is preferable to use a xylylene-modified phenol resin represented by the following general formula (1) from the viewpoint of low moisture absorption. In the general formula (1), the number of repetitions n is preferably in the range of n = 1 to 5.

[0015]

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The mixing ratio of the component A and the component B is such that the epoxy group (a) of the epoxy resin (component A) and the phenolic hydroxyl group (b) of the phenol resin (component B).
And the equivalent ratio [(a) / (b)] is (a) / (b) = 0.
It is preferable to set in the range of 5 to 2.0, and more preferably (a) / (b) = 0.8 to 1.2.

As the inorganic filler (component C) used together with the above-mentioned components A and B, inorganic powders such as fused silica, crystalline silica and alumina are used. These inorganic fillers can be used in either crushed or spherical form. These are used alone or in combination of two or more. Particularly preferred is fused silica. Further, those having an average particle size of about 20 to 40 μm are preferable. The amount of these inorganic fillers is preferably 70 to 95% by weight in the epoxy resin composition in view of the balance between moldability and solder heat resistance. If the amount is less than 70% by weight, the solder heat resistance tends to be insufficient. Tend to occur.

Next, the specific aluminum chelate compound (D component) used together with the above-mentioned A to C components is an aluminum chelate compound having a phosphate ester structure in the molecule. The effect of improving the adhesiveness between the lead frame and the cured body of the epoxy resin composition as the material can be obtained. As the specific aluminum chelate compound used in the present invention, for example, an aluminum chelate compound having a phosphate ester structure in a molecule represented by the following general formula (2) is preferably used. It can be obtained by reacting such an aluminum alcoholate, a chelating agent such as β-ketoester or β-diketone, and an acidic phosphate ester.

[0019]

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In the aluminum chelate compound represented by the general formula (2), R ₁ is an isopropyl group, R ₂
Is a methyl group, R ₃ is an ethoxy group, R ₄ is an octyl group, an aluminum chelate compound wherein R ₁ is an isopropyl group, R ₂ is a methyl group, R ₃ is an ethoxy group, and R ₄ is an isobutyl group. It is particularly preferable to use it from the viewpoint of improving adhesiveness.

The amount of the specific aluminum chelate compound (component D) is preferably set in the range of 0.1 to 2.0% by weight, particularly preferably 0.2% by weight, based on the entire epoxy resin composition. ~ 0.5% by weight. That is, if the amount of the component D is too small, it is difficult to obtain a sufficient effect of improving the adhesiveness to the lead frame. Conversely, if it exceeds 2.0% by weight, the curability of the resin tends to decrease. Because it can be seen.

Further, in addition to the above components (A) to (D), other conventionally used additives may be appropriately added to the epoxy resin composition used in the present invention, if necessary. Can be.

Examples of the other additives include a curing accelerator, a release agent, a flame retardant aid, a coloring agent, a silane coupling agent, and a stress reducing agent.

Examples of the curing accelerator include amines such as 1,8-diazabicyclo (5,4,0) undecene-7;
Examples include imidazoles, organic phosphorus compounds such as organic phosphine compounds and quaternary phosphonium compounds, and these can be used alone or in combination.

Examples of the releasing agent include conventionally known long-chain carboxylic acids such as stearic acid and palmitic acid, metal salts of long-chain carboxylic acids such as zinc stearate and calcium stearate, and waxes such as carnauba wax and montan wax. Can be used.

Further, examples of the flame retardant auxiliary include antimony trioxide, antimony pentoxide and the like.

Further, examples of the coloring agent include carbon black.

As the stress reducing agent, acrylonitrile-butadiene-styrene copolymer (ABS) and methyl methacrylate-butadiene-styrene copolymer (MB
Butadiene rubbers and silicone compounds such as S).

The epoxy resin composition for semiconductor encapsulation used in the present invention can be produced, for example, as follows. That is, first, the components (A) to (D) and the other additives are appropriately compounded, and the mixture is melted and mixed in a kneading machine such as a mixing roll in a heated state.
It can be manufactured by a series of steps of cooling it to room temperature, pulverizing it by a known means, and compressing it as necessary.

The sealing of a semiconductor element mounted on a lead frame using such an epoxy resin composition for semiconductor encapsulation is not particularly limited, and the semiconductor element on the lead frame may be molded by ordinary transfer molding. The sealing can be performed by a known molding method such as the above.

When the epoxy resin composition for encapsulating a semiconductor of the present invention is used as a sealing material, the lead frame may have a sufficient adhesive strength, for example, with a conventional sealing material, in view of improving the adhesiveness to the lead frame. Was not obtained, a lead frame having an Au plating layer formed on the outermost layer can be given. Further, there is a lead frame in which a Pd plating layer is formed in a lower layer adjacent to the Au plating layer. The Pd plating layer is formed, for example, by applying Pd plating to the surface of a lead frame body such as copper or a copper alloy, and such a lead frame is pre-plated with Pd by Pd (hereinafter referred to as “Pd-PPF”). ). Usually, the above Pd-P
PF is poor in adhesiveness to the cured sealing resin, but when the epoxy resin composition for semiconductor encapsulation of the present invention is used, because the D component is contained, the obtained cured sealing resin is It exhibits excellent adhesiveness, and as a result, high solder heat resistance can be obtained.

Next, examples will be described together with comparative examples.

First, the following compounds were prepared prior to the examples.

<Epoxy resin> (a): o-cresol novolak type epoxy resin (epoxy equivalent: 195, softening point: 80 ° C.)

(B): Novolac type brominated epoxy resin (epoxy equivalent: 275, softening point: 84 ° C.)

<Phenol resin> (c): Phenol novolak resin (hydroxyl equivalent: 10)
6, softening point: 83 ° C, 150 ° C, melt viscosity: 2 poise)

(D): Xylylene-modified phenolic resin represented by the following formula (3) (hydroxyl equivalent: 170, softening point: 83 ° C., 150 ° C. melt viscosity: 1.8 poise)

[0038]

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(E): phenol novolak resin (hydroxyl equivalent: 106, softening point: 91 ° C., 150 ° C. melt viscosity:
11 poise)

<Inorganic filler> (f): fused silica (average particle size: 20 μm)

<Aluminum chelate compound> (g): an aluminum chelate compound represented by the formula (2), wherein R _{1 is an} isopropyl group, R _{2 is a} methyl group, R _{3 is an} ethoxy group, and R _{4 is an} octyl group.

(H): In the general formula (2), R ₁ : isopropyl group, R ₂ : methyl group, R ₃ : ethoxy group, R
₄ : Aluminum chelate compound that is an isobutyl group

(I): an aluminum chelate compound represented by the following formula (4):

[0044]

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[0045]

Examples 1 to 8 and Comparative Examples 1 and 2
The components shown in Table 2 were blended in the proportions shown in the table, kneaded with a mixing roll machine, cooled, and then pulverized to obtain a desired powdery epoxy resin composition.

[0046]

[Table 1]

[0047]

[Table 2]

Using the epoxy resin composition, transfer molding of a semiconductor element (175 ° C. × 90 sec.
The semiconductor device was obtained by molding at 80 ° C. × 5 hours post-curing). This semiconductor device uses a 160-pin quad flat package (QFP-160), and as a lead frame, Ni: 500 μm in thickness, Pd: 50 μm in thickness, and A in outermost layer of a copper alloy body.
u: Each plated with a thickness of 8 nm was used. About the semiconductor device thus obtained, 85
After absorbing moisture for 168 hours at a temperature of 85 ° C./85% RH, it was immersed in solder at 260 ° C. to measure the time until a package crack occurred.

The adhesive strength was measured as follows. That is, the middle mold 11 and the lower mold 12 of the mold having a three-layer structure of the upper mold 10, the middle mold 11, and the lower mold 12 shown in FIG.
A metal plate 13 for measurement (the same material as the lead frame: a nickel plating layer having a thickness of 500 μm on a copper alloy body, a Pd plating layer having a thickness of 50 μm, and gold plating having a thickness of 8 nm) A plate on which a layer was formed: a size of 3 cm × 7 cm) was prepared, and the epoxy resin composition 14 was filled in a mold to form a measurement sample shown in FIG. In FIG. 2, reference numeral 13 denotes a metal plate for measurement, and reference numeral 15 denotes a resin-cured body having a truncated cone shape (the lower surface has a diameter of 1 cm and the upper surface has a diameter of <1 cm). Molding was performed at 175 ° C. for 2 minutes, and post-curing was performed at 175 ° C. for 5 hours, similarly to the usual molding conditions. Then, the obtained sample is, as shown in FIG.
The metal plate 13 was fixed to a fixing jig 16, and the end of the metal plate 13 was chucked by a tensile tester 17, and the shear adhesive strength between the cured resin 15 and the metal plate 13 was measured. Then, the adhesiveness between the cured resin body 15 and the metal plate 13 was evaluated from the shear adhesive strength.

Further, the sparral flow was evaluated under the conditions of 175 ° C. and 70 kg / cm ² using a mold conforming to the EMMI standard.

Further, 80 mm long × 10 mm wide × thickness 4
After molding a bar-shaped plate (cured body) having a thickness of 175 ° C. for 90 seconds, the hardness of the resin was measured with a Shore hardness meter to evaluate the curability of the resin.

The results of these measurements and evaluations are shown in Tables 3 to 5 below.
Also shown in Table 4.

[0053]

[Table 3]

[0054]

[Table 4]

From the results in Tables 3 and 4, it can be seen that all the products of Examples have a high spiral flow value and are excellent in fluidity, show high adhesive strength, and are also excellent in solder heat resistance. . In particular, the products of Examples 3 and 6 were more excellent in adhesiveness and solder heat resistance. On the other hand, Comparative Example 1 did not contain an aluminum chelate compound and had no problem with fluidity, but had extremely low adhesive strength and poor soldering heat resistance. Further, the product of Comparative Example 2 had no problem in fluidity similarly to the product of Comparative Example 1, but had low adhesive strength and poor solder heat resistance.

[0056]

As described above, the semiconductor device of the present invention has the following features.
By using a special epoxy resin composition containing a specific aluminum chelate compound (D component) to seal the semiconductor element with resin, the adhesion between the lead frame and the cured resin for sealing is improved, The package does not crack even under severe conditions such as solder mounting, and has excellent solder heat resistance.

In particular, the present invention provides a semiconductor device exhibiting good adhesiveness to a lead frame made of palladium which has recently been applied and having excellent solder heat resistance.

Although the present invention has been described centering on a surface-mount type semiconductor device, the present invention is not limited to this, and may be applied to a pin-insertion type mounting method or the like.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a method for producing an evaluation sample used for evaluating the adhesiveness of a cured resin body made of an epoxy resin composition.

FIG. 2 is a perspective view showing an evaluation sample obtained by the above manufacturing method.

FIG. 3 is an explanatory diagram showing a method for measuring a shearing force between a cured resin body and a frame.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI H01L 23/29 H01L 23/50 D 23/31 23/30 R 23/50

Claims (4)

[Claims] 1. A semiconductor device in which a semiconductor element mounted on a lead frame is sealed with an epoxy resin composition containing the following components (A) to (D). (A) Epoxy resin. (B) a phenolic resin. (C) an inorganic filler. (D) an aluminum chelate compound having a phosphate ester structure in the molecule. 2. The semiconductor device according to claim 1, wherein said lead frame has an Au plating layer as an outermost layer. 3. The method according to claim 1, wherein the lower layer adjacent to the Au plating layer is Pd.
3. The semiconductor device according to claim 2, wherein a lead frame which is a plating layer is used. 4. An epoxy resin composition for semiconductor encapsulation comprising the following components (A) to (D). (A) Epoxy resin. (B) a phenolic resin. (C) an inorganic filler. (D) an aluminum chelate compound having a phosphate ester structure in the molecule.