JP2002252235A - Resin paste for semiconductor and semiconductor device using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a resin paste for semiconductor having high adhesive strength and high solder crack resistance with low elasticity modulus when heated, which does not generate characteristic defectives of IC and the like due to chip cracks and warpage, even in the case of combination of a large sized chip of IC and the like and, a lead frame and the like with a large coefficient of linear expansion, and does not deteriorate adhesive strength when heated after moisture absorption. SOLUTION: This resin paste for semiconductor is made of (A) thermosetting resin and (B) filler, which has shearing bond strength of more than 2 MPa at 260 deg.C after leaving it for 72 hours under high temperature and high humidity of 85$0C, 85% and, modulus of elasticity being less than 100 MPa at 260 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin paste for a semiconductor for bonding a semiconductor element such as an IC or an LSI to a metal frame or the like.

[0002]

2. Description of the Related Art Recent remarkable developments in the electronics industry have evolved into transistors, ICs, LSIs, and ultra-LSIs. The integration of circuits in these semiconductor devices has rapidly increased, and mass production has become possible. With the spread of used semiconductor products, improvement of workability and cost reduction in mass production have become important issues. Conventionally, semiconductor elements were replaced with Au-S
In general, they were joined by an eutectic method and then sealed by a hermetic seal to obtain a semiconductor product. However, a resin encapsulation method has been developed in view of workability and cost during mass production, and is now common. Along with this, methods using solder materials and resin pastes for semiconductors have come to be taken up as an improvement of the Au-Si eutectic method in the mounting process.

However, the solder method has low reliability,
The disadvantage is that the electrode of the element is easily contaminated, etc.
Its use is limited to power transistors and power IC elements that require high thermal conductivity. On the other hand, resin paste for semiconductors is superior in workability and reliability as compared with the solder method, and the demand for the paste is rapidly increasing.

Further, in recent years, chips have been increased in size due to an increase in the degree of integration of ICs and the like. On the other hand, a copper frame has come to be used for the purpose of cost reduction because the 42 alloy frame which is a lead frame conventionally used is expensive. Here, when the size of a chip such as an IC becomes larger than about 4 to 5 mm square, the Au-Si eutectic method is used as a mounting method due to heating in the assembling process of the IC or the like. From the coefficient of thermal expansion, there is a problem of poor characteristics due to cracks and warpage of the chip.

That is, while the thermal expansion coefficient of silicon or the like, which is the material of the chip, is 3 × 10 ^-5 ° C., that of the 42 alloy frame is 8 × 10 ^-5 ° C., whereas that of the copper frame is 20 × 10 ^-5 ° C.
× is because as large as ^10-5. On the other hand, it is conceivable to use a mounting resin as the mounting method,
The conventional resin paste for semiconductors has a high modulus of elasticity and has not been able to absorb the distortion between the chip and the copper frame.

On the other hand, in response to the trend toward smaller and lighter electronic devices and higher functionality, semiconductor packages have become smaller and thinner.
As the pitch becomes increasingly narrow, resin pastes for semiconductors are required to improve solder cracking resistance and moisture resistance after moisture absorption, which is related to the reliability of semiconductor packages after encapsulation with epoxy resin molding materials. Have been. To improve reliability, it is necessary that the semiconductor chip and the lead frame adhere to each other. However, the conventional low-modulus resin paste for semiconductors requires the adhesiveness between the lead frame or semiconductor chip and the resin paste for semiconductor. And the package reliability does not improve as expected. For this reason, a resin paste for semiconductor has been proposed in which the adhesive strength at the time of heat after the moisture absorption treatment is increased (Japanese Patent Application Laid-Open No. 2000-2000).
265144).

[0007] However, due to recent environmental problems, Pb in Pb-Sn eutectic solder when mounting a semiconductor package on a substrate has become a problem, and there has been a tendency to use solder that does not use Pb. Since Pb-less solder has a higher melting point than conventional Pb-Sn eutectic solder, when using Pb-less solder, it is necessary to increase the solder reflow temperature when mounting a semiconductor package on a substrate. Specifically, in the conventional Pb-Sn eutectic solder, solder reflow was performed at about 235 ° C.
260 ° C. or higher is required for solderless. With the rise in solder reflow temperature, the solder crack resistance required for semiconductor packages has become more severe, and resin paste for semiconductors, which had no problem with solder crack resistance under conventional solder reflow conditions, is now compatible with Pb-less solder Under the solder reflow conditions described above, defects occurred, and further improvement in reliability was required.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a semiconductor device having a large chip such as an IC and a lead frame having a large coefficient of linear expansion, without causing characteristic defects such as an IC due to chip cracks or warpage and preventing heat after moisture absorption. It is an object of the present invention to provide a resin paste for semiconductors having a high adhesive strength, a low elastic modulus at the time of heat, and a high solder crack resistance, which does not lower the adhesive strength at the time.

[0009]

A semiconductor resin paste comprising (A) a thermosetting resin and (B) a filler;
After leaving for 72 hours at 5 ° C, 85% high temperature and high humidity, 2
The shear adhesive strength at 60 ° C. is 2 MPa or more and 26
It is a resin paste for semiconductors having an elastic modulus at 0 ° C. of 100 MPa or less. In a more preferred embodiment, the resin paste for semiconductor is a resin paste for semiconductor used for connecting a copper lead frame and a semiconductor chip. Also,
A semiconductor device manufactured using the above-mentioned resin paste for a semiconductor.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The thermosetting resin (A) used in the present invention is a general thermosetting resin comprising a resin, a curing agent, a curing accelerator, and the like. Is desirable to be liquid at room temperature.

Examples of the thermosetting resin (A) include liquid cyanate resin, liquid epoxy resin, various radically polymerizable acrylic resins, and triaryl isocyanurate having an aryl group. Examples of the liquid epoxy resin include bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol E type epoxy resin, alicyclic epoxy resin, aliphatic epoxy resin, and glycidylamine type liquid epoxy resin. it can. Among them, epoxy resin and acrylic resin are preferable from the viewpoint of adhesive strength.

Examples of the curing catalyst for the cyanate resin include metal complexes such as copper acetylacetonate and zinc acetylacetonate. Examples of the epoxy resin curing agent include a phenol resin, an aliphatic amine, an aromatic amine, dicyandiamide, and a dicarboxylic acid dihydrazide compound. Examples of the dihydrazide compound include carboxylic acid dihydrazides such as adipic dihydrazide, dodecanoic dihydrazide, isophthalic dihydrazide, and P-oxybenzoic dihydrazide.

As the curing accelerator and curing agent, epoxy resin
In fats, for example, there are various imidazole compounds,
Examples include 2-methylimidazole, 2-ethylimidazole
Dazol, 2-phenyl-4-methyl-5-hydroxy
Methyl imidazole, 2-C ₁₁H_{twenty three}-Such as imidazole
Common imidazole, triazine and isocyanuric acid
2,4-diamino-6-added to give storage stability
[2-methylimidazole- (1)]-ethyl-S-tri
Azine and its isocyanate adducts
Can be used alone or in combination.
Noh.

In the present invention, it is also possible to mix the thermosetting resins which are solid at room temperature to such an extent that the properties do not deteriorate. Epoxy resins include, for example, aliphatic epoxies such as bisphenol A, bisphenol F, phenol novolak, polyglycidyl ether, butanediol diglycidyl ether, and neopentyl glycol diglycidyl ether obtained by reacting cresol novolaks with epichlorohydrin, and diglycidyl hydantoin. And alicyclic epoxies such as vinylcyclohexene dioxide, dicyclopentadiene dioxide, and alicyclic diepoxy-adipate. These can be used in combination with one or more of these.

The filler (B) used in the present invention includes an inorganic filler and an organic filler. Examples of the inorganic filler include metal powder such as gold powder, silver powder, copper powder, and aluminum powder, fused silica, crystalline silica, silicon nitride, alumina, aluminum nitride, and talc. Examples of the organic filler include a silicone resin, a fluorine resin such as polytetrafluoroethylene, an acrylic resin such as polymethyl methacrylate, and a crosslinked product of benzoguanamine or melamine with formaldehyde. Among them, the metal powder is mainly used for imparting electrical conductivity and thermal conductivity.

The filler used has a content of ionic impurities such as halogen ions and alkali metal ions of 10 p.
pm or less. The shape may be a flake, scale, resin, or sphere. The particle size used varies depending on the required viscosity of the paste, but usually the average particle size is preferably 0.3 to 20 μm, and the maximum particle size is preferably about 50 μm. If the average particle size is less than 0.3 μm, the viscosity increases, and if it exceeds 20 μm, the resin component flows out during coating or curing, and bleeding occurs, which is not preferable.
If the maximum particle size exceeds 50 μm, the outlet of the needle is blocked when applying the paste with a dispenser, and continuous use cannot be performed for a long time. In addition, a mixture of a relatively coarse filler and a fine filler may be used, and various types and shapes may be appropriately mixed.

In order to impart required properties, the filler of the present invention may be, for example, a nanoscale filler having a particle size of about 1 to 100 nm, a composite material of silica and acrylic,
An organic / inorganic composite filler or the like having a metal coating on the surface of the organic filler may be added. The filler of the present invention may be one whose surface has been previously treated with a silane coupling agent such as alkoxysilane, allyloxysilane, silazane, or organoaminosilane.

After bonding the silicon chip to the lead frame using the resin paste for semiconductor of the present invention,
It is preferable that the shear adhesive strength at 260 ° C. after standing at 85% high temperature and high humidity for 72 hours is 2 MPa or more.
This is because when a semiconductor package is mounted on a printed wiring board by solder reflow connection, the package itself is 240 ° C.
When exposed at a temperature of 260 ° C. for several tens of seconds, if the adhesive strength of the internal paste layer is low, the paste layer first peels off,
This is because cracks are generated in the package, and therefore, it is preferable that the resin paste for a semiconductor has high adhesive strength at a high temperature even after absorbing moisture from the viewpoint of the reliability of the semiconductor package. It is preferable that the shear adhesive strength under the above conditions is 2 MPa or more, since peeling of the paste layer does not occur during high-temperature solder reflow.

Since the copper lead frame has a larger coefficient of linear expansion than the lead frame made of 42 alloy and thus has a large difference in expansion coefficient from the silicon chip, it is desirable to evaluate the shear adhesive strength of the copper frame after the moisture absorption treatment. . 260
It is desirable that the elastic modulus at the time of heating at 100C be 100 MPa or less. This is because a semiconductor package formed by bonding a semiconductor element to a lead frame using a resin paste for a semiconductor and then sealing using a sealing resin for a semiconductor is subjected to a solder reflow process after a moisture absorption process. Since the coefficients of thermal expansion are different, stress concentrates on the resin paste layer for semiconductor. However, when the elastic modulus of the resin paste for semiconductor under heat is 100 MPa or less, it is preferable because the stress can be reduced. If the pressure exceeds 100 MPa, the stress cannot be alleviated and peeling occurs at the interface between the semiconductor resin paste and the lead frame or semiconductor chip, which is not preferable.

The resin paste according to the present invention may contain a silane coupling agent, a titanate coupling agent, a pigment, a dye, a defoaming agent, a surfactant, a solvent, etc., as long as the properties according to the intended use are not impaired. Additives can be used. The production method of the present invention includes, for example, premixing each component, kneading using a three roll or the like to obtain a paste, and then defoaming under vacuum.

[0021]

EXAMPLES The present invention will be specifically described with reference to Examples. The mixing ratio of each component is part by weight. <Examples 1 to 5, Comparative Examples 1 to 5> Each component having the composition shown in Table 1 and a filler were blended and kneaded with a three-roll mill to obtain a resin paste. Apply this resin paste in a vacuum chamber
After defoaming at 2 mmHg for 30 minutes, various performances were evaluated by the following methods. Table 1 shows the evaluation results.

[0022]

[Table 1]

<Raw Materials> The raw materials used are as follows. -Bisphenol A type epoxy resin; Epicoat 828
(Yuika Shell Epoxy Co., Ltd.) Phenyl glycidyl ether Cyanate L-10

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Urethane acrylate; M-1600 (Toa Gosei Chemical Co., Ltd.) TAIC (Nippon Kasei Co., Ltd.)

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Phenol novolak resin; PH514
70 (Sumitomo Durez) ・ Triphenolmethane ・ Dicyandiamide ・ Cobalt naphthenate ・ Perhexa 3M (Nippon Oil & Fats Co., Ltd.)

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N-phenyl-γ-aminopropyltrimethoxysilane; KBM573 (Shin-Etsu Chemical Co., Ltd.) Epoxidized polybutadiene; E-1800 (Nippon Petrochemical Co., Ltd., epoxy equivalent 246) Silver powder: particle size Flakes with average particle size of 3 μm at 0.1 to 50 μm ・ Silica filler: maximum particle size of 20 μm with average particle size of 5 μm
Silica filler

<Evaluation method> Viscosity: 25 ° C. using an E-type viscometer (3 ° cone);
The value at 5 rpm was measured and defined as the viscosity. Adhesive strength: A 6 × 6 mm silicon chip was mounted on a copper frame using a paste and cured in an oven at 175 ° C. for 30 minutes. After curing, post cure (175 ° C,
8 hours), and after performing a moisture absorption process at 85 ° C. and a relative humidity of 85% for 72 hours, use a mount strength measuring device to perform 26 hours.
The hot die shear strength at 0 ° C. was measured. Elastic modulus: A resin paste for semiconductors on a Teflon (registered trademark) sheet is 10 mm in width, about 150 mm in length, and 10 in thickness.
After coating at 0 μm and curing in an oven at 175 ° C. for 30 minutes, using a tensile tester at 25 ° C. and 260 ° C.
Test length 100 mm, pulling speed 1 mm / 60 seconds (25
° C), 10 mm / 60 seconds (260 ° C), and the elastic modulus was calculated from the initial gradient of the obtained stress-strain curve.

Package crack resistance: A silicon chip of 6 × 6 mm was mounted on a copper frame using a paste and cured in an oven at 175 ° C. for 30 minutes. This was molded using an epoxy resin sealing material under the following conditions, and after a moisture absorption treatment at 85 ° C. and a relative humidity of 85% for 168 hours, an IR reflow treatment (260 ° C., 10 seconds) was performed to observe the cross section of the package. And the number of internal cracks was measured as an index of package crack resistance. Package: 80pQFP (14x20x2mm thickness) Chip size: 6x6mm (only surface aluminum wiring) Lead frame: Copper Molding of sealing material: 175 ° C, 2 minutes Post mold cure: 175 ° C, 8 hours Total number of packages: 12

In Examples 1 to 5, a paste having an excellent hot adhesive strength before and after moisture absorption, a paste having a low elastic modulus during heat was obtained, and the package crack resistance was good.
In Nos. 5 to 5, the package crack resistance is low because the properties of the paste having a shear adhesive strength of 2 MPa or more and the elastic modulus under heat of 100 MPa or less are not compatible.

[0030]

According to the present invention, even when a large chip such as an IC is combined with a copper frame or the like, the chip cracks or warps.
A resin paste for semiconductors that does not suffer from poor properties such as ICs, has a high adhesive strength at heat, and has a low elastic modulus at heat, and has excellent reliability without package cracks in a solder cracking resistance test after moisture absorption; and A semiconductor device using this is obtained.

Claims (3)

[Claims] 1. A semiconductor resin paste comprising (A) a thermosetting resin and (B) a filler, which has a shear adhesive strength of 2 MPa at 260 ° C. after standing at 85 ° C. and 85% high temperature and high humidity for 72 hours. A resin paste for semiconductors having an elastic modulus at 260 ° C. of 100 MPa or less. 2. The resin paste for a semiconductor according to claim 1, wherein the resin paste for a semiconductor is used for connecting a copper lead frame and a semiconductor chip. 3. A semiconductor device manufactured by using the resin paste for a semiconductor according to claim 1.