JPH03181547A - Resin composition for sealing semiconductor - Google Patents

Abstract

PURPOSE:To obtain a composition having excellent thermal stress characteristics, reliability and workability and suitable for the sealing of a semiconductor element on a ceramic substrate by compounding an epoxy resin with a specific amount of a specific inorganic filler, etc., having a specific particle size distribution. CONSTITUTION:The objective composition is produced by compounding (A) an epoxy resin preferably containing <=500ppm of hydrolyzable halogen group with (B) a phenolic novolak resin hardener, (C) an inorganic filler (e.g. silica or alumina) having a particle size distribution characterized by a number-ratio of particles of <=10mum diameter of <=25% and that of >=50mum diameter of 15-50% and (D) an organic solvent composed of two or more kinds of solvents having different boiling points (e.g. acetone, methyl ethyl ketone, etc.) wherein the ratio of one kind of solvent is <=90vol.% of the whole solvent. The ratio of C/(A+B+C) is 50-80vol.% and that of D/(A+B+C+D) is 20-40vol.%.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a resin that protects the surface of a semiconductor. More specifically, the present invention relates to a resin that protects the surface of a semiconductor. This invention relates to a liquid resin for semiconductor encapsulation, which is intended to prevent corrosion of wiring caused by moisture intrusion from the outside.

[Conventional technology]

Liquid resins for sealing semiconductor elements can be classified into those for ceramic substrates and those for ceramic substrates, depending on the type of substrate on which the semiconductor elements are mounted.

Both types require reliability characteristics such as heat resistance, moisture resistance, and thermal shock resistance, but especially in the case of ceramic substrates, the coefficient of thermal expansion of the substrate is usually as small as 7X10-'/°C, making it difficult to seal. It is necessary to reduce the thermal stress caused by the difference in coefficient of thermal expansion between the resin for use and the substrate.

If the thermal stress increases, cracks may appear in the cured resin or the cured resin may peel off from the substrate, significantly reducing the reliability of the semiconductor element.

Therefore, silicone resin with a low elastic modulus is used to reduce thermal stress, but it has weak adhesion, high moisture absorption, and the cured product is soft, so when external force is applied, the internal gold wire may break. There are drawbacks such as disconnection, and there are problems in terms of reliability.

On the other hand, epoxy resin is a resin that has good adhesion, moisture absorption rate, hardness of cured product, and excellent reliability, but because of its high elastic modulus, thermal stress increases and it is used as 4M resin for ceramic substrates. I can't.

Therefore, it has been considered to reduce the coefficient of thermal expansion by adding an inorganic filler to the epoxy resin, but this has the disadvantage that as the amount of filler added increases, the viscosity of the liquid resin increases, resulting in extremely poor workability. .

C Problems to be Solved by the Invention] The object of the present invention is to solve the problem by adjusting the amount and viscosity distribution of the inorganic filler and the amount of the organic solvent added in a liquid resin consisting of an epoxy resin and an inorganic filler. An object of the present invention is to provide a liquid resin for semiconductor encapsulation that has excellent thermal stress characteristics, reliability, and workability.

[Means to solve the problem]

The inventors of the present invention conducted intensive studies to solve these problems that could not be overcome with conventional techniques, and as a result, the following number of particles was found:
(D) A mixture of two or more solvents with different boiling points, in which the proportion of one type of solvent is 90% by volume or less of the total solvent. It is a liquid resin composition consisting of an organic solvent, and its composition ratio is (C) / ((A) + (B) + (C)
') -50 to 80% by volume, and (D)/((
A) + (B) + (C) + (D)) - When using a liquid resin composition for semiconductor encapsulation of 20 to 40% by volume, it has excellent thermal stress characteristics and reliability, and can highly improve workability. Based on this knowledge, we have completed the present invention.

The volume used in the present invention is volume (cc) - weight 1 (g)/true specific gravity (cc/g).

[For production]

The epoxy resin used in the present invention may be any conventional epoxy resin, but preferably has a content of hydrolyzable halogen groups of not more than sooppm.

The types include the following:

Phloroglucinol triglycidyl ether, triglycyl ether of trihydroxybiphenyl, tetraglycyl ether of tetrahydroxybiphenyl, tetraglycyl ether of tetrahydroxybisphenol F, tetraglycyl ether of tetrahydroxybenzophenone, epoxidized novolak, epoxidized Polyvinylphenol, triglycyl isocyanurate, triglycyl cyanurate, triglycyl S-) riazine, triglycyl aminophenol, tetraglycyl diaminodiphenylmethane, tetraglycidyl biromellitic acid, triglycyl trimellitic acid, diglycidyl Aniline, diglycidyl bisphenol A1 diglycidyl bisphenol S, diglycidyl aniline of dihydroxybenzophenone, diglycidyloxybenzoic acid, diglycidyl phthal! (o, m, p), diglycidylhydaintoin, diglycidylaniline, diglycidylaniline, etc., and these can be used alone or in combination of two or more.

In addition, a low viscosity epoxy resin generally called a reactive diluent may be used in combination with the above epoxy resin. kind,
These include glycidyl amines such as diglycidyl aniline and diglycidyl toluidine, glycidyl ethers such as butyl glycidyl ether, phenyl glycidyl ether, and talesyl glycidyl ether, and other glycidyl esters.

As the phenol novolac resin curing agent, an amorphous resinous substance containing as little free phenol as possible, which is an initial condensation product of phenols and aldehydes, is preferable. For example, phenol, cresol, xylenol, etc.
Low-molecular liquid novolacs mainly composed of di- and tri-nuclear bodies obtained by reacting phenols with formaldehyde in a dilute aqueous solution under strong acidity, monohydric phenols and polyfunctional aldehydes such as acrolein and glyoxal. These include initial condensates under acidic conditions with formaldehyde and polyhydric phenols such as resorcinol, catechol, and hydroquinone with formaldehyde.

Two or more of these curing agents may be used in combination, if necessary.

Inorganic fillers used in the present invention include silica, alkali, calcium carbonate, magnesium oxide, magnesium hydroxide, boron nitride, etc., and these may be used alone or in combination.
More than one species can be used in combination.

The particle size distribution of these inorganic fillers requires that the number of particles of 10 μm or less is 25% or less and the number of particles of 50 μm or more is 15 to 50%. By incorporating a large amount of filler, we were able to reduce the thermal expansion coefficient of the cured product and maintain good workability with the liquid resin.

When the number of particles of less than IO μm exceeds 25% in the charcoal distribution of the inorganic filler, the specific surface area of the inorganic filler increases, the viscosity increases, and the workability deteriorates significantly. 50 again
Even if the number of particles larger than μm is less than 15%, the specific surface area increases, the viscosity increases, and workability deteriorates. On the other hand, 50μm
If the number of particles above exceeds 50%, the inorganic filler, epoxy resin, curing agent, and solvent will be likely to separate, causing the inorganic filler to settle, resulting in poor workability and a failure to obtain a uniform cured product, making it unreliable. Sexuality decreases.

In order to reduce the coefficient of thermal expansion of a cured product of a liquid resin, it is sufficient to increase the amount of inorganic filler blended.The factor that determines the coefficient of thermal expansion is the volume of the resin component of the cured product and the inorganic filler. It is a ratio and needs to be controlled by an appropriate volume ratio.

When controlling by weight ratio, the specific gravity differs depending on the type of inorganic filler, so even if the weight ratio is the same, each inorganic filler has a different volume ratio and a different coefficient of thermal expansion.

In addition, the appropriate range for the volume ratio of the inorganic filler and the resin component is to bring the thermal expansion coefficient of the cured product as close to that of the ceramic substrate as possible, and to prevent the viscosity of the liquid resin from increasing and maintain good workability. This is an important point.

The blending ratio of these inorganic fillers is (inorganic filler)/((epoxy resin) + (phenol novolac resin curing agent) + (inorganic filler)) -50 to 8
It is essential that it be 0% by volume.

By blending the ratio within this range, the workability of the liquid resin is very good, and the coefficient of thermal expansion of the cured product is also small, reducing thermal stress and preventing the occurrence of cranking and peeling from the ceramic substrate. It can be prevented.

If the blending ratio of this inorganic filler is less than 50% by volume, the amount of inorganic filler in the cured resin product will be small and the coefficient of thermal expansion will be large, resulting in increased thermal stress, which may cause cranking or peeling from the ceramic substrate. occurs, significantly reducing the reliability of semiconductors. If the blending ratio exceeds 80% by volume, the amount of inorganic filler in the liquid resin will be too large, resulting in high viscosity and poor workability.

Further, the organic solvent used in the present invention is a mixture of two or more organic solvents having different boiling points. As these solvents, ketones, alcohols, esters, aromatic hydrocarbons, etc. can be used. Specifically, acetone, methyl ethyl ketone, methyl isobutyl ketone, methanol, ethanol, isopropanol, butanol, and Butanol, methyl it/lucerosolve, ethyl cellosolve, methyl cellosol butyl cello acetate, methyl carpitol, ethyl carpitol, butyl carpitol, hexane, benzene, toluene, xylene, etc.

It is necessary to use a mixed solvent that is a mixture of two or more of these solvents, and the boiling points of these solvents differ by 0, preferably 5°C or more, and the proportion of any one type of solvent in the mixed solvent is It should be less than 90% by volume in the solvent.

These reasons will be discussed below.

This resin has a limited proportion of inorganic filler in order to reduce the coefficient of thermal expansion, but when mixed with epoxy resin and phenol novolak hardener at this proportion, the viscosity becomes extremely high, making it difficult to use for practical purposes. Therefore, it is necessary to mix an organic solvent in order to obtain a viscosity that allows for good workability. However, when an organic solvent is mixed, when heating and curing the liquid resin composition, there is a problem! The evaporation of the solvent leaves traces and voids tend to remain in the cured product. If the number of such voids increases, the reliability of the semiconductor device will deteriorate, which is undesirable.

As a result of intensive studies to prevent the occurrence of voids, the inventor of the present invention found that the occurrence of voids is due to the rapid evaporation of the solvent during curing heating, and that by mixing two or more types of solvents with different boiling points, the evaporation of the solvent can be slowed down. It was found that voids can be prevented.

Further, at this time, if the proportion of one type of solvent in the mixed solvent is greater than 90% by volume, the evaporation of the solvent will not be as gentle as in the case of a single solvent, and voids will occur in the cured product.

The amount of organic solvent used here is (organic solvent)/((epoxy resin) + (phenol borac resin curing agent) + (inorganic filler) + (organic solvent)) -20 to 4
It is essential that it be 0% by volume.

If it is less than 20% by volume, the viscosity of the liquid resin becomes too high and the workability becomes extremely poor. If it exceeds 40% by volume, the inorganic filler, epoxy resin, curing agent, and solvent will tend to separate, causing sedimentation of the inorganic filler, worsening workability, and making it impossible to obtain a uniform cured product, reducing reliability. Resulting in.

A curing accelerator, an antifoaming agent, a dispersion stabilizer, a flame retardant, and a coloring agent may be added to the liquid resin composition of the present invention, if necessary.

〔Example〕

Next, the present invention will be explained in detail with reference to Examples.

Example 1 Phenol novolac epoxy resin (hydrolyzable chlorine content 350 ppm, number average molecular weight 3
00. Epoxy equivalent 1180) 10% by volume Phenol novolank resin (number average molecular weight 530, OH equivalent 105) 5% by volume Tris (dimethylaminomethyl) Phenol - curing accelerator 0.05% by volume 50
A homogeneous liquid resin composition was obtained by kneading 50% by volume of methyl ethyl ketone (boiling point: EO'C), 25% by volume toluene (boiling point: 111°C), 10% by volume (30% of particles having a diameter of μm or more) in a Laikai machine. The obtained liquid resin composition had good workability, and when a semiconductor element on a ceramic substrate was sealed, there were no voids, cracks, or peeling of the cured resin composition.

Also, using a simulated element, after preheating at 80℃ for 1 hour,
After curing and sealing for 13 hours, a temperature cycle test (TC) of 100 cycles and a pressure tanker test of 100 hours were performed, and the aluminum corrosion of the circuit was detected.
There were no defects due to gold wire breakage, and the product had excellent reliability.

Shown in the table.

Example 2 Results 1st Bisphenol A epoxy resin (hydrolyzable chlorine content 400 ppm, number average molecular weight 3)
80, epoxy equivalent 190) 11% by volume Phenol novolak resin (number average molecular weight 370, O)I equivalent 105) 6% by volume Tris (dimethylaminomethyl) Phenol-hardening accelerator 0.06% by volume 50
Example 1: The number of particles larger than μm is 20%) 53% by volume methyl ethyl ketone (boiling point 80°C) 2% by volume toluene (boiling point 111'C) 4% by volume methyl isobutyl ketone (boiling point 116°C) 24% by volume
A liquid resin was obtained in the same manner as above.

The obtained product had good workability, appearance of the cured product, and reliability in the same manner as in the example. The results are shown in the schedule.

Comparative Examples 1 to 5 Liquid resins were prepared using the formulations shown in Table 1 in the same manner as in Example 1, but all had inappropriate viscosities and poor workability.

Furthermore, in Comparative Example 4, the appearance of the cured product was poor because the amount of inorganic filler was small. The results are shown in Table 1.

Comparative Examples 6 to 8 Liquid resins were prepared using the formulations shown in Table 1 in the same manner as in Example 1, but the appearance of the cured products was poor in all cases. The results are shown in Table 1.

Comparative Example 9.10 Liquid resins were prepared using the formulations shown in Table 1 in the same manner as in Example 2, but all had inappropriate viscosities and poor workability. The results are shown in Table 1.

Evaluation method Thermal expansion coefficient 240 from room temperature at 2°C/min using a duratometer
The cured product was heated to 'C, and the coefficient of thermal expansion in the region from room temperature to the edge of the glass transition temperature was determined from a temperature-elongation curve chart.

C 30 minutes/-55°C 10 minutes/room temperature 30 minutes/125°C
After 100 cycles, the appearance of the cured product and the occurrence of defects due to gold wire breakage in the simulated element were examined.

〔Effect of the invention〕

The liquid resin composition for semiconductor encapsulation according to the present invention has an appropriate viscosity, so it has extremely good workability, and since rapid evaporation of the solvent can be prevented, the appearance of the cured product is excellent. Furthermore, the cured product has a small coefficient of thermal expansion and can reduce thermal stress. When a semiconductor is sealed with this composition, cranking and peeling will not occur.

This makes it possible to take advantage of epoxy resin's excellent adhesion, low moisture absorption rate, and hardness of the cured product, and provides the moisture resistance required for a liquid resin that seals semiconductor elements mounted on a ceramic substrate. This is a liquid resin composition for semiconductor encapsulation that can meet reliability characteristics such as thermal shock resistance.

Claims (1)

[Claims] (1) (A) Epoxy resin (B) Phenol novolak resin curing agent (C) Particle size distribution of 25% of particles of 10 μm or less
An inorganic filler (D) in which the number of particles of 50 μm or more is 15 to 50%; (D) an organic solvent in which the proportion of one type of solvent is 90% by volume or less in the total solvent in a mixture of two or more types having different boiling points; It is a liquid resin composition consisting of (C)/
((A)+(B)+(C))=50-80% by volume, and (D)/((A)+(B)+(C)+(D))=
A resin composition for semiconductor encapsulation, characterized in that the content is 20 to 40% by volume.