JP2005239901A - Epoxy resin composition for encapsulating optical semiconductor and optical semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an epoxy resin composition for encapsulating optical semiconductors excellent in light transparency and discoloration resistance in high temperature storage and an optical semiconductor encapsulated with the cured material. <P>SOLUTION: The epoxy resin composition is mainly composed of (A) an epoxy resin having not less than two epoxy groups in the molecule, (B) a curing agent for phenolic resins, (C) a curing promotor and (D) crushed molten silica. The composition contains (E) a phenolic antioxidant as an indispensable ingredient. A 1 mm thick cured material of the epoxy resin composition has a 700 nm-1,000 nm light transmittance of ≥15% and a 720 nm light transmittance retention of ≥50% after being exposed to 125°C heat for 1,000 hours. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an epoxy resin composition for sealing an optical semiconductor and an optical semiconductor device sealed with a cured product thereof.

  Transfer molding of an epoxy resin composition as a sealing method for semiconductor elements such as IC and LSI is suitable for mass production at low cost and has been used for a long time. Improvements have been made to improve properties. In the field of optoelectronics, inorganic filler-filled epoxy resin compositions are used in highly reliable photocouplers because they are excellent in electrical insulation and low thermal expansion properties and transmit near infrared light.

  A photocoupler combines a light receiving element and a light emitting element and transmits a signal using light. For this reason, it is important to efficiently transmit light from the light emitting side to the light receiving side. Moreover, in order to block the light from the outside and to give moisture resistance reliability, it is characterized by having a double sealing structure. That is, first, the optical semiconductor element is sealed with a primary sealing resin having light transmission ability, and subsequently sealed with a secondary resin having a light shielding property. As the secondary resin having a light-shielding property, it is common to use a normal epoxy resin for semiconductor encapsulation.

  The efficiency of the photocoupler is expressed by CTR (Current Transfer Ratio), and is determined by the ratio of the current on the light emitting side and the electromotive force on the light receiving side. For this reason, studies on transparent wax, filler shape, and the like have been made so far, but in order to obtain a high CTR value, the light transmittance of the resin composition, particularly near infrared light in the vicinity of 850 nm to 1000 nm. High light transmittance is required.

  In general, when a phenol resin is used as a curing agent, an oxidation phenomenon due to heat occurs, and the primary sealing resin used for the photocoupler may be discolored. Various examinations have been made so far for these problems.

  Patent Document 1 and Patent Document 2 describe resin compositions to which an antioxidant having a specific structure is added. In recent years, however, photocouplers are increasingly using optical semiconductor elements in a low wavelength region, particularly 700 nm to 800 nm, in order to transmit light more efficiently.

When the present inventors used a primary sealing resin that has been studied so far, the sealing resin was oxidized and discolored by heat generation of the optical semiconductor element, and the light transmission ability was reduced. Furthermore, the conventional sealing resin does not match the optical semiconductor elements used in the low wavelength region, and the sealing resin changes color during long-term storage at a high temperature of 120 to 180 ° C. and 1000 to 10,000 hours. The property was extremely low.
Japanese Patent Laid-Open No. 2-86149 (full text) JP 2001-234073 A (full text)

  The present invention provides an epoxy resin composition for encapsulating an optical semiconductor excellent in light transmittance and excellent in resistance to discoloration during high-temperature storage, and an optical semiconductor device encapsulated with a cured product thereof.

The present invention
[1] Epoxy resin composition mainly composed of an epoxy resin (A) having two or more epoxy groups in one molecule, a phenol resin curing agent (B), a curing accelerator (C), and a molten crushed silica (D) A phenolic antioxidant (E) as an essential component, and in a 1 mm thick cured product of the epoxy resin composition, the light transmittance at 700 nm to 1000 nm is 15% or more, and An epoxy resin composition for sealing an optical semiconductor, characterized in that the light transmittance retention at 720 nm after treatment at 125 ° C. for 1000 hours is 50% or more,

[2] The phenolic antioxidant (E) is 2,6-di-tert-butyl-4-methylphenol, 2,5-di-tert-amylhydroquinone, 2,5-di-tert-butylhydroquinone. 4,4′-butylidene-bis (3-methyl-6-tert-butylphenol), 2,2′-methylene-bis (4-methyl-6-tert-butylphenol), 2,2′-methylene-bis ( 4-ethyl-6-tert-butylphenol) and 4,4′-thiobis (3-methyl-6-tert-butylphenol) at least one selected from the group consisting of photosemiconductor encapsulation according to item [1] Epoxy resin composition for stopping,

[3] The optical semiconductor according to [1] and [2], wherein the phenolic antioxidant (E) is contained in the total epoxy resin composition in an amount of 0.1 wt% to 5 wt%. Epoxy resin composition for sealing,

[4] The maximum particle size of the fused crushed silica (D) is 125 μm or less, and the fused crushed silica (D) is contained in the total epoxy resin composition in an amount of 30% by weight to 90% by weight. The epoxy resin composition for optical semiconductor encapsulation according to any one of [1], [2] or [3],

[5] The epoxy resin composition for optical semiconductor encapsulation according to any one of [1], [2], [3] or [4], wherein the iron content in the total epoxy resin composition is 15 ppm or less. Stuff,

[6] An optical semiconductor device encapsulated with a cured product of the epoxy resin composition for encapsulating an optical semiconductor according to any one of [1] to [5],
It is.

  The epoxy resin composition for optical semiconductor encapsulation of the present invention provides an optical device with excellent light transmittance, excellent discoloration resistance and light transmittance during high-temperature storage, and has high reliability and good storage stability. can do.

  The present inventors obtain a high light transmittance by using a specific filler, and further suppress a resin discoloration and a decrease in light transmittance during high-temperature storage by adding a specific antioxidant. And it discovered that the epoxy resin composition excellent in the high temperature storage characteristic was obtained, and came to complete this invention.

The epoxy resin composition of the present invention exhibits high transparency by using a specific filler so that the light transmittance at 700 nm to 1000 nm of a cured 1 mm thickness of the epoxy resin composition is 15% or more. Is.
The measurement of the light transmittance is not limited as long as it can measure the light transmittance of a spectrophotometer or the like. As a spectrophotometer, it is convenient and preferable to measure with Shimadzu self-recording spectrophotometer UV-3100 (integral sphere installation type). The measurement sample may be a cured product of an epoxy resin composition having a thickness of 1 mm and is not limited to any shape, but using a low-pressure transfer molding machine, a molding temperature of 175 ° C., a pressure of 6.9 MPa, and a curing time. It is simpler and more preferable if a test piece of 30 mm × 10 mm × 1 mm is molded in 120 seconds and processed as an after cure by treatment at 175 ° C. for 4 hours. When the photocoupler package is assembled using an epoxy resin composition whose light transmittance is lower than the lower limit, the light transmission ability of the photocoupler is reduced, and sufficient optical characteristics of the photocoupler cannot be obtained. Absent.

  Furthermore, in the present invention, in the cured product of the epoxy resin composition, the light transmittance at 720 nm after treatment at 125 ° C. for 1000 hours is required to be 50% or more as compared with the light transmittance before treatment. is there. When the light transmittance retention is below the lower limit, the reliability as a photocoupler is remarkably lowered, which is not preferable.

  In the cured product of the epoxy resin composition, it is essential that the phenolic antioxidant (E) is essential as a blending component of the epoxy resin composition in order to achieve a light transmittance retention of 50% or more after high temperature treatment. The inventors have found. The phenolic antioxidant (E) used in the present invention is not limited as long as it prevents oxidation of the resin due to heat. More preferably, 2,6-di-tert-butyl- 4-methylphenol, 2,5-di-tert-amylhydroquinone, 2,5-di-tert-butylhydroquinone, 4,4′-butylidene-bis (3-methyl-6-tert-butylphenol), 2,2 '-Methylene-bis (4-methyl-6-tert-butylphenol), 2,2'-methylene-bis (4-ethyl-6-tert-butylphenol), 4,4'-thiobis (3-methyl-6- Examples thereof include phenolic antioxidants such as tert-butylphenol. The phenolic antioxidant exhibits an antioxidant function even in a long-term reliability test such as 1000 hours or more, and remarkably improves the reliability of the photocoupler. When an epoxy resin composition not containing a phenolic antioxidant is treated at 125 ° C. for 1000 hours or longer, the surface of the cured resin composition is oxidized, and the originally white cured product is brown, dark brown The color changes to black, the light transmittance is greatly reduced, and the light transmission ability of the photocoupler is significantly reduced. The addition amount of the phenolic antioxidant is more preferably 0.1% by weight or more and 10% by weight or less. Further, it is more preferably 0.1 wt% or more and 5 wt% or less. When the amount is less than 0.1% by weight, the effect of the antioxidant may not be obtained. When the amount exceeds 10% by weight, curing may be inhibited.

  The epoxy resin (A) having two or more epoxy groups in one molecule used in the present invention is not limited as long as it has two or more epoxy groups in one molecule. Specifically, it has two epoxy groups such as bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol type epoxy resin such as bisphenol S type epoxy resin, and biphenyl type epoxy resin, hydrogenated bisphenol A type epoxy resin. Polyfunctional heterocyclic epoxy resin such as epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, alkyl-modified triphenolmethane type epoxy resin, triglycidyl isocyanurate, polyfunctionality such as poly (epoxidized cyclohexene oxide) Such as alicyclic epoxy resin Epoxy resin having a number or more epoxy groups are preferred. These epoxy resins may be used alone or in combination of two or more. In order to improve moisture resistance reliability, it is desirable that the amount of chlorine ions, sodium ions, and other free ions contained in the epoxy resin used in the present invention be as small as possible.

The phenol resin curing agent (B) used in the present invention refers to monomers, oligomers, and polymers in general having a phenolic hydroxyl group in the molecule. Modified phenol resins, triphenolmethane type resins, phenol aralkyl resins (having a phenylene skeleton, biphenylene skeleton, etc.), naphthol aralkyl resins (having a phenylene skeleton, a biphenylene skeleton, etc.), etc. Absent.
These may be used alone or in combination of two or more. In order to improve moisture resistance reliability, it is desirable that chlorine ions, sodium ions, and other free ions contained in the phenol resin be as small as possible.

    The equivalent ratio of epoxy groups of all epoxy resins to phenolic hydroxyl groups of all phenol resins is preferably 0.5 to 2.0, particularly preferably 0.7 to 1.5. If it is out of the preferable range, curability, moisture resistance reliability and the like may be lowered.

  As the curing accelerator (C) used in the present invention, any of those usually used for anionic curing of an epoxy resin can be used, but any one that promotes the crosslinking reaction between the epoxy resin and the phenol resin. For example, tertiary amines, quaternary ammonium salts, bicyclic amidines such as 1,8-diazabicyclo (5,4,0) undecene-7 and derivatives thereof, 2-methylimidazole, 2- Examples thereof include, but are not limited to, imidazoles such as phenyl-4-methylimidazole, and organic phosphorus compounds such as triphenylphosphine and tetraphenylphosphonium / tetraphenylborate salts. These may be used alone or in combination of two or more. As long as it has good curability and is not colored, it is not limited at all, and it may be used alone or in combination of two or more. In particular, bicyclic amidines such as 1,8-diazabicyclo (5,4,0) undecene-7 and imidazoles can exhibit high activity with respect to epoxy resins even with a small addition amount, and are more preferable. When the total weight of all epoxy resin compositions is 100 parts by weight, the addition amount of the curing accelerator is preferably 0.1 to 2 parts by weight.

  Although there is no restriction | limiting in particular as fused crushing silica (D) used for this invention, Generally what is used for a sealing material can be used. Particularly preferably, those having a maximum particle size of 125 μm or less from the viewpoint of gate clogging during molding. The filling amount of the melt-crushed silica is more preferably added in a ratio of 30% by weight or more and 90% by weight or less in the entire epoxy resin composition. If the lower limit is not reached, it will not be possible to obtain a sufficient reinforcing effect with fused crushed silica, and the amount of resin component that is a moisture absorption factor will increase, so the amount of moisture absorption of the cured product of the epoxy resin composition will increase. Therefore, there is a possibility that cracks are likely to occur in the semiconductor device during the soldering process. When the upper limit is exceeded, the fluidity of the epoxy resin composition is lowered, and there is a possibility that poor filling, chip shift, pad shift, and wire sweep are likely to occur during molding.

  A known method may be used to measure the particle size of the melt-crushed silica, but the volume particle size distribution of the particles is measured by a laser light scattering method, and converted to the weight particle size distribution using the true density value of the particles. It is preferred to use the method.

  In the present invention, the iron content in the epoxy resin composition is more preferably 15 ppm or less. When it exceeds 15 ppm, the light transmittance is lowered due to the influence of iron, which may affect the light transmission ability of the photocoupler.

  The iron content may be measured using a powdered epoxy resin composition. It is convenient to dissolve the powdered epoxy resin composition in an appropriate amount of acetone, add dilute nitric acid and extract, and then measure by atomic absorption spectrometry.

    In addition to the above components, the epoxy resin composition for optical semiconductor encapsulation of the present invention includes other epoxy resins, mold release agents, coupling agents, inorganic fillers other than fused crushed silica, and the like as necessary. There is nothing wrong with combining known additives and auxiliary materials.

In the epoxy resin composition of the present invention, the components (A) to (E) and other additives are mixed using a mixer or the like, and then heated and kneaded using a heating kneader, a heating roll, an extruder, or the like. It is obtained by cooling and grinding. Alternatively, the components (A) and (B) may be preliminarily heated and mixed in a reaction kettle or the like to obtain a resin composition in a B-stage state, and then obtained through the aforementioned steps.

As for an epoxy resin composition, it is more preferable to manufacture an epoxy resin, a hardening | curing agent, a hardening accelerator, a fusion | melting crushing silica, and another component using a biaxial extruder, Furthermore, the jacket temperature of a biaxial extruder is 50- It is more preferable to knead at 120 ° C. and pulverize the kneaded material after kneading with a ceramic granulator, but it is not limited to these production methods.
The granulator made of ceramic which is a pulverizer is a different direction rotating type, and examples of the material used include zirconia and alumina. Examples of the surface of the granulator include smoothness, dimple processing, and slit processing. What is necessary is just to adjust the rotation speed at the time of a grinding | pulverization suitably with the magnitude | size of a granulator and the discharge amount of a biaxial extruder. The resin composition obtained by such a production method has less iron contamination and is more preferable as a resin composition for photocouplers.

  Sealing using the epoxy resin composition for optical semiconductor sealing can be performed by a general method. For example, the optical semiconductor element is sealed by a transfer molding method or the like, and a cured product of the epoxy resin composition is used. A sealed optical semiconductor device can be obtained.

EXAMPLES Examples will be shown below to describe the present invention in more detail, but the present invention is not limited to these examples.
(Examples 1-20, Comparative Examples 1-5)
Components (A) to (E) and other additives were mixed at the blending ratios shown in Tables 1, 2, and 3 and kneaded at 50 to 90 ° C. for 5 minutes using a twin screw extruder, and the obtained kneading was performed. The product sheet was cooled and pulverized using a granulator to obtain an epoxy resin composition.

The evaluation method is as follows, and the results are summarized in Tables 1, 2, and 3.
[Measurement of light transmittance]
The tablet of the epoxy resin composition was transfer molded under the conditions of a mold temperature of 175 ° C., an injection pressure of 6.86 MPa, and a curing time of 120 seconds to obtain a molded product of 30 × 10 × 1 mm. The molded product was measured for light transmittance with a wavelength of 700 nm to 1000 nm and a thickness of 1 mm, using a spectrophotometer (Shimadzu Corp., self-recording spectrophotometer UV-3100) equipped with an integrating sphere.

[Evaluation of light transmittance retention]
The molded product obtained above was treated at 125 ° C. for 1000 hours, the light transmittance was measured in the same manner as described above, and the ratio of the light transmittance after treatment to the light transmittance before treatment was determined. Units%.
[Iron content measurement]
1 g of the powdery powder of the epoxy resin composition was dissolved in 5 ml of acetone, 20 ml of 2N-nitric acid was added, and after extraction, the concentration of iron was measured by atomic absorption spectrometry.

[Evaluation of fluidity]
The epoxy resin composition before molding was molded and filled using a spiral flow measurement mold according to EMMI-I-66 under conditions of a molding temperature of 175 ° C., an injection pressure of 6.86 MPa, and a curing time of 120 seconds. Was measured. Evaluations were made with ◯ for 40 cm or more and X for less than that.

[Evaluation of fillability]
The above epoxy resin composition tablet is mounted on a surface mount package (12-pin SOP, 4 × 5 mm, thickness 1.2 mm, chip size 1.5 mm × 2.0 mm, lead frame 42 alloy, gate size 0 .5 mm × 0.05 mm) using a mold, transfer molding was performed at a mold temperature of 175 ° C., an injection pressure of 6.86 MPa, and a curing time of 120 seconds. It was confirmed whether there was no gate clogging at the time of molding.

  In addition, the contents of the blends, product names, and various types of fused crushed silica described in Tables 1, 2, and 3 are as follows.

Orthocresol novolac type epoxy resin: epoxy equivalent 210, softening point 62 ° C
Dicyclopentadiene-modified phenol type epoxy resin: Epoxy equivalent 265, softening point 60 ° C., HP-7200 manufactured by Dainippon Ink & Chemicals, Inc. was used.
Phenol novolac resin: hydroxyl group equivalent 105, softening point 90 ° C
Phenol aralkyl resin: hydroxyl equivalent 174, softening point 80 ° C
1,8-diazabicyclo- (5,4,0) -undecene-7
2-Methylimidazole Silica A: Fused crushed silica with a maximum particle size of 75 μm and an average particle size of 11 μC Silica B: Fused crushed silica with a maximum particle size of 54 μm and an average particle size of 15 μC Silica C: Melted with a maximum particle size of 125 μm and an average particle size of 33 μm Crushed silica Crystalline silica: Crystalline silica having a maximum particle size of 33 μm and an average particle size of 13 μm 2,6-di-tert-butyl-4-methylphenol 2,5-di-tert-amylhydroquinone 2,5-di-tert-butyl Hydroquinone 4,4′-butylidene-bis (3-methyl-6-tert-butylphenol)
2,2′-methylene-bis (4-methyl-6-tert-butylphenol)
2,2′-methylene-bis (4-ethyl-6-tert-butylphenol)
4,4′-thiobis (3-methyl-6-tert-butylphenol)
Coupling agent: γ-glycidoxypropyltrimethoxysilane carnauba wax

  As is apparent from the results shown in the table, the epoxy resin composition for sealing an optical semiconductor of the present invention is excellent in light transmittance, suppresses resin discoloration and decrease in light transmittance during high temperature storage, and stores at high temperature. It can be seen that the characteristics are excellent.

The epoxy resin composition for encapsulating an optical semiconductor of the present invention has an optical semiconductor device in which an optical semiconductor element is encapsulated with excellent light transmittance and discoloration resistance at high temperature storage, and high reliability. Therefore, it can be suitably used for optical devices such as photocouplers.

Claims (6)

It is an epoxy resin composition mainly composed of an epoxy resin (A) having two or more epoxy groups in one molecule, a phenol resin curing agent (B), a curing accelerator (C), and a molten crushed silica (D). In addition, the epoxy-based antioxidant (E) is contained as an essential component, and in the 1 mm-thick cured product of the epoxy resin composition, the light transmittance at 700 nm to 1000 nm is 15% or more, and 125 ° C. An epoxy resin composition for sealing an optical semiconductor, wherein the light transmittance retention at 720 nm after the treatment for 1000 hours is 50% or more. The phenolic antioxidant (E) is 2,6-di-tert-butyl-4-methylphenol, 2,5-di-tert-amylhydroquinone, 2,5-di-tert-butylhydroquinone, 4, 4'-butylidene-bis (3-methyl-6-tert-butylphenol), 2,2'-methylene-bis (4-methyl-6-tert-butylphenol), 2,2'-methylene-bis (4-ethyl The epoxy resin composition for optical semiconductor encapsulation according to claim 1, comprising at least one selected from the group consisting of -6-tert-butylphenol) and 4,4'-thiobis (3-methyl-6-tert-butylphenol). Stuff. The epoxy resin composition for optical semiconductor encapsulation according to claim 1 or 2, wherein the phenolic antioxidant (E) is contained in the total epoxy resin composition in an amount of 0.1 wt% to 5 wt%. . The maximum particle size of the fused crushed silica (D) is 125 µm or less, and the fused crushed silica (D) is contained in 30 wt% or more and 90 wt% or less in the total epoxy resin composition. The epoxy resin composition for optical semiconductor sealing in any one of 2 or 3. 5. The epoxy resin composition for optical semiconductor encapsulation according to claim 1, wherein the iron content in the total epoxy resin composition is 15 ppm or less. The optical semiconductor device sealed with the hardened | cured material of the epoxy resin composition for optical semiconductor sealing in any one of Claims 1 thru | or 5.