JPS6361017A - Liquid epoxy sealant - Google Patents

Abstract

PURPOSE:To obtain a sealant having an excellent crack resistance and useful for electronic and electrical parts, by comprising a liquid epoxy compd, a specific copolymer, a liquid acid anhydride as a curing agent, fine particles of spherical inorganic filler, a silane coupling agent and a curing accelerator in a specified ratio. CONSTITUTION:The objective sealant comprises (A) 100pts.(wt.) of a liquid epoxy compd. having >=2 epoxy groups in the molecule, (B) 10-60pts. of a liquid butadiene-acrylonitrile copolymer having COOH groups at the molecular terminals (preferably one having a mol.wt. of 2,000-6,000 and contg. 5-30wt% acrylonitrile), (C) 0.8-1.2 equivs. (per epoxy group) of a liquid acid anhydride as a curing agent (e.g., methylhexahydrophthalic anhydride), (D) 15-65vol% (based on the total vol.) of a particulate inorganic filler with an average particle size of 1-10mu, (E) 0.5-5pts. of a silane coupling agent and (F) 0.3-3pts. of a curing accelerator.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a sealing material for electronic/electrical components.

More specifically, the present invention relates to a liquid sealing material used for sealing semiconductor elements, capacitors, flyback transformers, ignition coils, diodes, and the like.

<Prior art> Currently, semiconductor devices are encapsulated using compositions containing epoxy resin as the main ingredient, fused silica or crystalline silica as filler, and phenol novolak as curing agent, and a curing accelerator. is used.

Although this composition is in powder form, it is formed into tablet or pellet form for ease of handling.

This tablet or pellet is introduced into a part of the cylinder of a low-pressure transfer molding machine, heated and melted, and then press-fitted into a mold in which a semiconductor element has been placed in advance and heated and hardened to complete resin sealing of the semiconductor element.

This method is called low-pressure transfer molding, and because it is easy to mass-produce, it has become the mainstream method for resin encapsulation of semiconductor devices.

However, due to high equipment costs, it is not suitable for low-volume, high-mix production.

Casting, dipping, and dropping methods are used for low-volume, high-mix production.

The casting method is a method in which an element is placed in a mold, a liquid sealant is injected, and then the element is heated and cured.

The dipping method is a method in which an element is immersed in a liquid sealant, the sealant is adhered to the surface of the element, and then heated and cured.

The dropping method is a method in which a liquid sealant is dropped onto an element and cured by heating.

As described above, the method using liquid encapsulant has low equipment costs and is suitable for small-volume, high-mix production. The problem is that the gender is low.

That is, the coefficient of linear expansion is large, and stress is applied to the semiconductor element due to temperature changes, resulting in defects such as disconnection of wiring or cranking of the sealing resin itself.

To reduce the coefficient of linear expansion, a method of filling an inorganic filler with a low coefficient of linear expansion is generally used, but if the filling is high, the fluidity of the liquid encapsulant decreases significantly, making it difficult to mold as described above. method becomes unusable.

For this reason, reactive diluents are sometimes used, but these also have drawbacks such as a decrease in heat resistance.

Furthermore, there are problems such as corrosion of the aluminum forming the wiring of the semiconductor integrated circuit due to the mixing of ionic impurities.

As a method for reducing the coefficient of linear expansion, for example, Japanese Patent Application Laid-Open No. 19620/1983 discloses that a cured product with a small coefficient of linear expansion can be obtained by using a spherical inorganic filler as a component of a liquid sealant. It is stated that

Further, JP-A-60-124647 describes a method of improving thermal shock resistance by using a spherical filler as a component of a solid encapsulant.

As a method of reducing the elastic modulus of the sealing material, for example, Japanese Patent Application Laid-Open No. 57-3821 describes adding a silicone compound.

Further, JP-A No. 57-180626 describes that the occurrence of cranks in the sealing material can be prevented by adding a polybutadiene derivative having a functional group.

These sealants are solid at room temperature in the composition before curing, and are raw materials for low-pressure transfer molding.

<Problems to be Solved by the Invention> The performance required of a liquid sealant for electronic/electrical parts is as follows.

fl) Low viscosity.

(2) The glass transition temperature is at least 110°C or higher.

(3) The coefficient of linear expansion is small.

[4) Good adhesion to the substrate.

]5) The elastic modulus of the cured product is small.

In addition to these basic physical properties, good crack resistance is required.

JP-A-61-19620 and JP-A-60-12464
When a spherical inorganic filler like No. 7 is used, the coefficient of linear expansion becomes smaller, but the modulus of elasticity becomes higher, and in some cases,
The stress applied to electronic components may increase.

JP-A-57-3821 and JP-A-57-180626
As shown in No. 1, in the case of a solid sealant, a rubber-like substance can be optionally added, but in the case of a liquid sealant, there are restrictions because it is required to have a low viscosity at room temperature.

Another problem is that among rubber-like substances, silicone-based rubbers generally have weak adhesive strength with glass substrates.

Means for Solving the Problems) The present inventors have conducted extensive research into a composition that can solve the above-mentioned problems and also satisfy the various characteristics required of a liquid sealant, and have developed the present invention. invention has been achieved.

That is, the present invention provides: (a) 100 parts by weight of a liquid epoxy compound having two or more epoxy groups in the molecule; (b) liquid putadiene having a carboxyl group at the end;
Acrylonitrile copolymer lO~60! ! Amount part (c) Liquid acid anhydride 0.8 to 1 based on epoxy group
．． 2 equivalents (d) 15-65% by volume of the entire spherical inorganic filler with an average particle size of 1-100μ (e) Silane cuff pulling agent 0.5-5 parts by weight <f
>This relates to a liquid epoxy encapsulant containing 0.3 to 3 parts by weight of a curing accelerator.

Specific examples of liquid epoxy compounds having two or more epoxy groups in the molecule used in the present invention include diglycidyl ether of bisphenol A, diglycidyl ether of bisphenol F, triglycidyl ether of phloroglycine, and phenol and acetaldehyde. glycidyl ether of a condensate of, glycidyl ether of m-methyl-p-aminophenol, glycidyl ether of diaminodiphenylmethane, and glycidyl ether of p-amino-m-cresol.

In the present invention, liquid means that the viscosity is 500 voids or less at 25°C.

A solid or semi-solid epoxy compound may also be mixed and used with the main purpose of increasing the glass transition temperature of the cured product of the sealant.

However, as long as the mixture is in liquid form.

Specific examples of this solid or semi-solid epoxy resin include glycidyl ether of various novolacs such as glycidyl ether of phenol novolak, glycidyl ether of talesol novolac, glycidyl ether of bisphenol A novolac, polyvinylphenyl glycidyl ether, polyisopropenylphenyl Examples include glycidyl ether.

Further, when flame retardation is required, glycidyl ether of tetrabromobisphenol A and bromphenyl glycidyl ether can be added.

In the present invention, in principle, reactive diluents such as phenylglycidyl ether, which reduce heat resistance, are not used.

The liquid putadiene-acrylonitrile copolymer having a carboxyl group at the end has a molecular weight of 2.000 to 6,00.
0. The acrylonitrile content is 5 to 30% by weight and has a carboxyl group at the end of the molecular chain.

The content of the copolymer is 10 to 60 parts by weight based on 100 parts by weight of the epoxy compound.

If the copolymer content is less than 10 parts by weight, sufficient crack resistance cannot be obtained.

Furthermore, the effect of reducing the elastic modulus of the cured product of the sealant is not sufficient.

When the content of the copolymer is 60 parts by weight or more, crack resistance is significantly improved, but other properties required for the liquid sealant are lowered. That is, this is not preferable because it causes a decrease in the glass transition temperature and an increase in the coefficient of linear expansion.

There are two known methods for blending cough copolymers.

Specifically, the copolymer and the epoxy compound are mixed in advance to form an adduct through the reaction between the terminal carboxyl group and the epoxy group, and then the mixture is mixed with a curing agent.The copolymer, the epoxy compound, and the curing agent are mixed simultaneously. This is the way to do it.

The former blending method improves crank resistance, but increases the viscosity of the sealant.

Although the latter compounding method suppresses the increase in the viscosity of the encapsulant, the former compounding method is not as effective in improving crack resistance.

Liquid encapsulants are required to have various properties, such as when low viscosity is required or when crack resistance is required, so if the compounding method and amount of the copolymer are selected according to the required properties, good.

The liquid acid anhydride of the curing agent used in the present invention is a liquid according to the above-mentioned definition of liquid, and has at least one dicarboxylic acid anhydride group in the molecule.

Specifically, they include methylhexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylnadic anhydride, and hemicic acid.

These can be mixed with a solid acid anhydride as long as the acid anhydride is in a liquid state.

Specific examples of solid acid anhydrides include phthalic anhydride, maleic anhydride, trimellitic anhydride, pyromellitic anhydride, hexahydrophthalic anhydride, and tetrahydrophthalic anhydride.

The content of the nucleic acid anhydride is 0.8 to 1.2 equivalents to the epoxy group of the epoxy compound.

Outside this range, the performance of the cured product of the liquid sealant will be impaired, such as a decrease in glass transition.

Among the curing agents for epoxy resins, there are amine-based curing agents.

However, when such a curing agent is used, there are drawbacks such as a high water absorption rate of the cured product and a decrease in electrical properties such as volume resistance, making it unsuitable for sealing electronic and electrical components.

The spherical inorganic filler preferably has an average particle size of 1 to 100 microns.

If the average particle size is less than 1 μm, the viscosity of the liquid sealant increases and high filling cannot be achieved.

If the filling amount is small, a cured product with a low coefficient of linear expansion cannot be obtained.

If the average particle size is 100 μm or more, a problem arises in that the filler settles during storage of the liquid sealant.

Further, thixotropy is sometimes required for the liquid sealant, and if the average particle size is 100 μm or more, sufficient thixotropy cannot be imparted.

The spherical shape of the inorganic filler of the present invention means that the aspect ratio is 1 to 1.
．． 5.

The reason why a spherical shape is preferable is that the viscosity of the liquid encapsulant is lower than that of other shapes at the same filling amount, and because a spherical shape can be filled with a higher filling rate at the same viscosity, the coefficient of linear expansion of the cured liquid encapsulant is lower. The spherical shape means less wear during processing, the spherical shape makes it difficult to cause mechanical damage to the sealed object, and there are no Omura parts that can cause cracks in the resin part when stress is applied. It is.

Furthermore, it has the advantage of easily imparting thixotropy to the liquid sealant.

Specific examples of inorganic fillers include alumina, fused silica,
These include glass, aluminum hydroxide, and hydrated alumina.

Alumina is preferred in fields where thermal conductivity is required.

Furthermore, fused silica is preferred in fields where a linear expansion coefficient is required.

Aluminum hydroxide is preferred in fields where flame retardancy is required.

Two or more of these inorganic fillers can be used in combination.

The blending amount of the inorganic filler is 15 to 65% by volume of the total.

If it is less than 15% by volume, the coefficient of linear expansion cannot be made sufficiently small, which is not preferable.

If it is more than 65% by volume, the viscosity of the liquid sealing material increases significantly, the processability decreases, and the adhesion to the object to be sealed also decreases, which is not preferable.

The silane coupling agent used in the present invention is blended in an amount of 0.5 to 5 parts by weight per 100 parts by weight of the epoxy compound.

When the blending amount is less than 0.5 parts by weight, the adhesive strength between the inorganic filler and the epoxy compound is insufficient, so that the interface ff4 separates when stress is applied.

Moreover, when the amount is more than 5 parts by weight, the moisture resistance and the glass transition temperature are lowered.

When using an inorganic filler whose surface has been treated with a silane cuff pulling agent, this amount should also be taken into account.

Specific examples of the silane coupling agent include γ-glycidoxypropyltrimethoxysilane, β-(3,4 epoxycyclohexyl)ethyltriethoxysilane, T-aminopropyltriethoxysilane, T-mercaptopropyltrimethoxysilane, etc. However, the present invention is not limited to these.

Specific examples of curing accelerators used in the present invention include benzyldimethylamine, tris(dimethylaminemethyl)
They are phenol, dimethylaniline, 2-ethyl-4-methylimidazole, pyridine, piperazine, diethylaminopropylamine, modified amine, and N-trimethylsilylimidazole.

Various modified amines are used for low temperature curing purposes.

Further, imidazoles are preferred for the purpose of increasing the glass transition temperature of the cured product.

In particular, N-)limethylsilylimidazole has a high glass transition temperature and is suitable for obtaining a cured product with improved hygroscopicity.

The blending amount of the curing accelerator is 0.3 to 3 parts by weight per 100 parts by weight of the epoxy compound.

If the blending amount is less than 0.3 parts by weight, the curing speed will be slow and productivity will be reduced, which is industrially disadvantageous.

If the blending amount is 3 parts by weight or more, electrical properties such as volume resistance will deteriorate.

Moreover, storage stability is also lowered, which is not preferable.

<Effects of the Invention> The liquid sealing material of the present invention is suitable for sealing electronic and electrical components in the following respects.

(1) It can be used as a sealing material with a high glass transition temperature.

(2) Liquid putadiene with a carboxyl group at the end
By blending an acrylonitrile copolymer, crank resistance is significantly improved.

(3) It is possible to achieve low viscosity, thereby eliminating the need for reactive diluents that have been used up to now.
Adverse effects of reactive diluents, namely lowering of glass transition temperature,
Eliminate deterioration of electrical properties (4) Inside the encapsulant, increase the adhesive strength at the interface of the filler and at the same time increase the adhesive strength between the encapsulant and the base.

(5) A low coefficient of linear expansion is achieved by highly filling the inorganic filler, and a reduction in the elastic modulus of the cured product is also achieved by using the liquid putadiene-acrylonitrile copolymer together.

<Examples> Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples.

Examples 1 to 10 and Comparative Examples 1 to 5 Each component of an epoxy compound, a liquid putadiene-acrylonitrile copolymer having a carboxyl group at the end, a curing agent, an inorganic filler, a coupling agent, a curing accelerator, and a pigment was added to the first They were blended in the proportions shown in the table and mixed using a kneader to obtain a liquid epoxy composition.

The amounts of each component in the table are volume % for the inorganic filler and parts by weight for the others.

The copolymer is Hycar CTBN manufactured by Ube Industries Jun.
1300X31 was used.

The inorganic fillers are ■AX-25 (spherical alumina) and 5-COL (spherical fused silica) manufactured by Micron, Hi-3ilex ■Sumi 3 (amorphous crystalline silica) manufactured by Hayashi Kasei, and FB- manufactured by Denki Kagaku Kogyo Jun. 90 (amorphous fused silica) was used.

In addition to commonly used commercially available curing accelerators, Amicure MY
24 (manufactured by Ajinomoto ■) was used.

Using these mixed and adjusted compositions, 3×10100
A test piece was prepared by pouring the mixture into a casting mold having a size of X100 and curing at 100°C for 2 hours and then at 150°C for 4 hours.

The test piece obtained by cast molding was adjusted to a specified size using a diamond cutter to create a test piece for measurement.

The viscosity was measured at 50° C. using an E-type rotational viscometer manufactured by Tokyo Keiki ■.

Dynamic viscoelasticity was measured using Toyo Seiki Rheograph Solid.
Measured at ℃.

The coefficient of linear expansion was measured using a thermomechanical analyzer manufactured by Daini Seiko Kin.
Measurement was performed at a temperature rising rate of 5° C./min below the glass transition temperature.

At the same time, the glass transition temperature was also measured.

The water resistance was expressed as the water absorption rate (%) measured using a pressure tester test of a test piece under the conditions of 121° C. and 2 atm based on JIS K6911 5.26.

Crank resistance was evaluated by placing a No. 2 12S washer specified in JIS B1251 (spring washer) in the center of a flat-bottomed groove with an inner diameter of 5Q mm and a depth of 20 mm, and applying the epoxy composition to it so as not to contain air bubbles. A test piece was prepared by pouring and casting to a height of 2 mm above the washer.

The obtained test piece was immersed in dry ice-ethanol at -55°C for 30 minutes, and then left in a hot air circulation drying product at 150°C for 30 minutes.

This operation was regarded as one cycle, and the number of cycles for crank generation was investigated.

The results are shown in Table 2.

Claims (1)

[Claims] (1) A liquid epoxy sealant consisting of the following components (a) to (f). (a) 100 parts by weight of a liquid epoxy compound having two or more epoxy groups in the molecule (b) Liquid putadiene having a carboxyl group at the end
Acrylonitrile copolymer 10-60 parts by weight (c) 0.8-1.2 equivalents based on liquid acid anhydride epoxy group as a curing agent (d) Spherical inorganic filler with an average particle size of 1-100μ 15-65% by volume of the total (e) 0.5-5 parts by weight of silane coupling agent (f) 0.3-3 parts by weight of curing accelerator