JPH059455A - Adhesive for airtight sealing - Google Patents

Abstract

PURPOSE:To provide the title adhesive which is excellent in heat resistance and adhesive properties and generates little water and few voids by incorporating a specific polymer and a specific metal powder into the adhesive. CONSTITUTION:The title adhesive contains a polymer having at least 10mol% repeating units of formula I [wherein X is a group of formula II or III (wherein R1 is H or a monovalent org. group; and R2 is a tetravalent org. group)] in the molecule [e.g. a polyimide resin prepd. from 1,3-bis(3-aminophenoxy)benzene and 3,3',4,4'-oxydiphthalic dianhydride] and at least one metal powder selected from the group consisting of powders of Al, Mg, Zn, and Fe.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an adhesive used when die-bonding a semiconductor element to a hermetically sealed ceramic package. More specifically, after the semiconductor element is bonded, the bonding strength does not decrease due to the decomposition of the resin even with the high temperature due to the heat treatment during the sealing of the ceramic package, and the low void bonding in which the water content in the sealed container is extremely small It is related to agents.

[0002]

2. Description of the Related Art Conventionally, when a semiconductor element is mounted on a ceramic package, an inorganic mounting material such as Au-Si eutectic or low melting point glass, or an organic paste using an epoxy resin or a polyimide resin has been used. .. However, due to the increase in size of semiconductor devices, when thermal stress is applied to the difference in the coefficient of thermal expansion between the ceramic package and the device,
The inorganic mount material could not be absorbed and chip cracks occurred. In addition, since the inorganic mount material has a high elastic modulus, chipping and the like occurred when mechanical shock was applied. With respect to such defects, attempts have been made to improve the above defects by using an organic paste containing a resin having a low elastic modulus as a base and filled with a metal filler. However, these organic pastes are still inferior in heat resistance to the inorganic mount materials, and the resin decomposes due to the high temperature at the time of sealing the ceramic package, the adhesive strength is reduced, and a large amount of gas is generated to perform sealing. Damage, or
There is a problem in that a large amount of water is generated and reliability is lowered, and especially in an ultraviolet erasable read-only memory (EPROM), dew condensation causes a drastic decrease in function.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to use a polyimide resin as a base material, which has heat resistance equal to or higher than that of an inorganic type while utilizing the low stress of an organic type and has a very small amount of generated water. An object of the present invention is to provide an adhesive for airtight sealing having excellent adhesiveness.

[0004]

According to the present invention, a repeating unit represented by the following general formula (1) is added to a polymer molecule in an amount of 10
An adhesive for hermetic sealing containing a polymer having a mol% or more and at least one of aluminum powder, magnesium powder, zinc powder, and iron powder.

[0005]

[Chemical 2] Examples of preferable monovalent organic groups for R ₁ are:

[0006]

[Chemical 3] However, the present invention is not limited to these. Also, two or more kinds may be used in combination. Examples of preferred tetravalent organic groups for R ₂ include

[0007]

[Chemical 4]
etc However, the present invention is not limited to these. Also, two or more kinds may be used in combination.

The repeating unit represented by the general formula (1) in the polymer must be 10 mol% or more,
It is preferably 20 mol% or more. If it is less than 10 mol%, sufficient adhesive strength may not be obtained, or the amount of voids may increase. Repeating units other than the repeating unit represented by the general formula (1) may be copolymerized and / or blended in a range of less than 90 mol%. Examples of preferable ones for copolymerization and / or blending include:

[0009]

[Chemical 5]

Polyimides and / or polyimide precursors such as, but not limited to these. Also, two or more kinds may be used in combination. The repeating unit represented by the general formula (1) is obtained by reacting the tetracarboxylic dianhydride having the structure of R ₁ and R ₂ with 1,3-bis (3-aminophenoxy) benzene. You can As a feature of this polyimide resin, since it has an ether bond in the molecule, it has a low elastic modulus,
It can be mentioned that it is excellent in stress relaxation when a semiconductor element is mounted and has a strong adhesive force.

The filler used in the present invention is at least one of aluminum powder, magnesium powder, zinc powder and iron powder. As the shape, a flake shape, a resin shape, a spherical shape, or the like is used. There is no problem even if a mixture of particles having different particle diameters or particles is used. As the filler, aluminum powder, magnesium powder, zinc powder, the reason for using at least one of the iron powder, reduction of thermal resistance by improving the thermal conductivity of the adhesive layer after curing without impairing the heat resistance of the polyimide resin, In addition to high strength and low voids,
It is possible to reduce the amount of internal moisture after the ceramic package is sealed. In this case, the mixing ratio of the filler / the polymer represented by the general formula (1) is 0.05 to 10
(Polymerization ratio) is preferable. If the mixing ratio is less than 0.05, it becomes difficult to obtain the effect of the filler, and if the mixing ratio exceeds 10, the amount of the polymer is too small, so that the adhesive strength is likely to decrease.

It is preferable that the composition of the present adhesive has a solid content of 10 to 90% by weight, and the remaining component is a solvent. If the solid content is other than this, it is difficult to obtain a sufficient thickness of the adhesive layer, which causes unevenness, and as a result, the adhesive strength is likely to be lowered. Further, if it is more than this, the paste has a high viscosity,
Handling as an adhesive becomes difficult. Preferred examples of the solvent include N-methyl-2-pyrrolidone, benzylpyrrolidone, N, N-dimethylacetamide, N, N-dimethylformamide, tetrahydrofuran, dimethyl sulfoxide, diethylene glycol dimethyl methyl ether (diglyme), tetraethylene. There are glycol dimethyl ether (tetraglyme), γ-butyrolactone, ethyl cellosolve acetate, butyl cellosolve acetate, cyclohexanone, etc., but not limited thereto. Also, two or more kinds may be used in combination. Further, a poor solvent for the polymer may be used as a volatilization regulator, a film smoothing agent, etc. within a range where it can be made uniform.

Further, in the present invention, an antifoaming agent can be added if necessary. The method for producing the airtight sealing adhesive is as follows. A polymer having a repeating unit represented by the general formula (1) or a solution thereof, a filler, a solvent is weighed, and an antifoaming agent or the like is added if necessary, and a stirrer, a mortar, a triple roll, a kneader, etc. A single paste or a proper combination is used to form a uniform paste. As a method of using the airtight sealing adhesive of the present invention, the adhesive can be applied by an ordinary dispenser or the like. After mounting the semiconductor element, it can be heat-cured and adhered in an oven or on a heating plate.

Since the airtight sealing adhesive of the present invention can be used for bonding a semiconductor element to a ceramic package and has a low elastic modulus, chip cracking due to a difference in coefficient of thermal expansion between the ceramic package and the semiconductor element, It is possible to prevent chipping due to mechanical shock. Furthermore, it is a low-void airtight sealing adhesive that has excellent heat resistance and adhesive strength, and has a very small amount of internal water after sealing the ceramic package due to the reducing action of the filler.

[0015]

EXAMPLES The present invention will be specifically described below with reference to examples.

Synthesis Example 1 23.39 g (0.08 g) of 1,3-bis (3-aminophenoxy) benzene was placed in a four-neck separable flask equipped with a thermometer, a stirrer, a raw material inlet, and a dry nitrogen gas inlet tube. Mol)
Is dissolved in 193 g of N-methyl-2-pyrrolidone.
Under a dry nitrogen gas inflow, 24.82 g (0.08 mol) of 3,3 ′, 4,4′-oxydiphthalic acid dianhydride was added all at once, and stirring was continued for 5 hours while maintaining the temperature at 20 ° C. to form a polyamic acid varnish. Obtained. To the obtained polyamic acid varnish, 58 g of toluene was added, the dry nitrogen gas introduction pipe was removed, and a Dean Starch reflux cooling pipe was attached instead, to raise the temperature of the system. Continue heating while removing water generated by imidization from the system by azeotropic distillation with toluene.
Water no longer formed due to imidization at ~ 150 ° C 5
The reaction was terminated after a lapse of time. The obtained polyimide varnish was dropped into 30 liters of methanol with stirring for 1 hour to precipitate the resin, and the solid content was collected by filtration, followed by drying in a dryer at 120 ° C. for 8 hours. It was
The FT-IR spectrum of the polyimide resin thus obtained was measured, and the imidation ratio was determined from the absorption based on the amide bond before imidization appearing at 1650 cm ⁻¹ and the absorption based on the imide ring appearing at 1780 cm ⁻¹ . By the way, 100
It was found to be% imidized.

Synthesis Example 2 22.98 g (0.0786 g) of 1,3-bis (3-aminophenoxy) benzene was placed in a four-necked separable flask equipped with a thermometer, a stirrer, a raw material inlet, and a dry nitrogen gas inlet tube. Mol) and silicone diamine of formula (2)

[0018]

[Chemical 6] 17.10 g (0.0224 mol) are dissolved in 166 g N-methyl-2-pyrrolidone. Under the inflow of dry nitrogen gas,
3,3 ', 4,4'-oxydiphthalic anhydride 31.02
g (0.1 mol) was added all at once, and stirring was continued for 5 hours while maintaining the temperature at 20 ° C. to obtain a polyamic acid varnish. 63 g of toluene was added to the obtained polyamic acid varnish, and a silicone-modified polyimide resin was obtained in the same manner as in Synthesis Example 1 below. The imidation ratio of the obtained resin was 100%.

Example 1 100 parts by weight of the polyimide resin obtained in Synthesis Example 1, 100 parts by weight of aluminum powder having an average particle size of 5 μm, 110 parts by weight of γ-butyrolactone, and 75 parts by weight of tetraglyme were stirred and then kneaded with a three-roll mill. Then, a uniform paste-like adhesive was obtained. The obtained adhesive is applied to a ceramic package, a silicon chip of 10 × 7 mm square is mounted at a pressure of 150 gf, heated at 120 ° C. for 1 hour, and then at 150 ° C., 25
After curing at 0 ℃ and 350 ℃ for 30 minutes respectively, at 390 ℃ 2
After heat treatment for 0 minutes, the adhesive strength was measured by a Tensilon universal testing machine (according to MIL-STD-883C2027). Similarly, after curing using a 15 x 15 mm square silicon chip,
Observe the void area of the bonded part with SOFTX (MIL-
STD-883C2012). A lid was placed on the sample prepared in the same manner as the sample subjected to the void observation, a load of 1 Kgf was applied, and the sample was treated at 390 ° C. for 20 minutes and sealed. The amount of water in the sealed package was analyzed by mass spectrometry (according to MIL-STD-883C1018). The thermal decomposition temperature was measured by a thermobalance of the cured adhesive. The evaluation results are shown in Table 1.

Examples 2 and 3 and Comparative Examples 1 to 3 Adhesives were prepared and evaluated in the same manner as in Example 1 with the compounding ratios shown in Table 1. The evaluation results are shown in Table 1.

A filler containing a polymer having a repeating unit represented by the general formula (1) in a specific ratio as in Examples 1 to 3 and at least one of aluminum powder, magnesium powder, zinc powder and iron powder. When the chips are bonded with an adhesive consisting of a specific ratio of solvent, the water content after sealing is 0.3.
% Or less, and the void area was as small as less than 20%. The adhesive strength was 20 Kgf or more (10 × 7 mm square silicon chip), which was a sufficient value. On the other hand, Comparative Examples 1 and 3
Has a considerably large amount of water of 2% or more. In Comparative Example 2 using aluminum nitride, the heat resistance and the adhesive strength are good, but the water content is 0.74%, which is better than the case of using only silver powder, but the standard 0.5% is known. It is also considered that voids will be 80% or more, and the thermal conductivity will deteriorate.

[0022]

[Table 1]

[0023]

EFFECTS OF THE INVENTION The airtight sealing adhesive of the present invention is excellent in adhesive strength and less in the generation of voids, and eliminates the conventional defect that the amount of water after sealing is large. Suitable for hermetic sealing.

Claims (1)

Claims: 1. A polymer having a repeating unit represented by the following general formula (1) in an amount of 10 mol% or more in a polymer molecule:
An airtight sealing adhesive comprising at least one of aluminum powder, magnesium powder, zinc powder and iron powder. [Chemical 1]