JP5101425B2 - Epoxy resin composition for optical semiconductor element sealing and optical semiconductor device using the same - Google Patents

Description

  The present invention relates to an epoxy resin composition for sealing an optical semiconductor element used for sealing various optical semiconductor elements and an optical semiconductor device formed by sealing an optical semiconductor element using the same.

  Conventionally, as a sealing material for an optical semiconductor element such as a light receiving element and a light emitting element, an epoxy resin composition has been used from the viewpoint of excellent transparency, moisture resistance, and heat resistance. This epoxy resin composition is, for example, transfer-molded in a molding die provided with an optical semiconductor element, and an optical semiconductor device is formed by using the optical semiconductor element as a package (see, for example, Patent Document 1).

In this optical semiconductor package, as with semiconductor packages other than the optical semiconductor, the surface mounting method has been rapidly spread instead of the conventional pin insertion mounting method for the purpose of reducing the size and weight and improving the mounting productivity. ing. Examples of such surface mount packages include a two-way flat package (small outline package: SOP), a four-way flat package (quad flat package: QFP), and SON (small outline non-lead).
JP 2006-93277 A

  In the surface mounting method, unlike the pin insertion mounting method, the entire package is exposed to a high temperature environment of 260 ° C. at the time of mounting. At that time, moisture absorbed during storage after manufacturing the optical semiconductor device is rapidly vaporized and expanded, and a large stress is generated. When the stress exceeds the strength of the package, a crack occurs in the package. To prevent this, optical semiconductor manufacturers add steps such as moisture-proof packaging of optical semiconductor devices at the time of shipment, and heating and drying optical semiconductor devices in an oven before the mounting process at the mounting site. However, the cost increase due to the moisture-proof packaging, the deterioration of workability due to the opening of the packaging, and the cost for the heat drying are significant burdens. As a general technique for solving the problem of cracking of the sealing resin due to water vapor, there is a method in which a large amount of a high-strength structure such as a filler is contained in the sealing resin. From the viewpoint of property, it is difficult to use a method of containing a large amount of high-strength structures such as the filler. In addition, a method of increasing the solder group resistance by increasing the content of aliphatic groups and phenyl groups and lowering the water absorption rate of the resin itself is also conceivable. However, even with this method, the glass transition temperature of the epoxy resin composition ( Since Tg) is high and the elastic modulus during solder reflow is high, the stress due to vaporization expansion during reflow cannot be relieved and cracks occur. As a technique for reducing the elastic modulus at the time of solder reflow, a method of lowering the glass transition temperature (Tg) of the epoxy resin composition is conceivable. However, this method significantly reduces the temperature cycle reliability, and the reliability of the product. There is a problem that it cannot be satisfied in terms of sex.

  The present invention has been made in view of such circumstances, and has an excellent epoxy resin for sealing an optical semiconductor element that has excellent transparency, crack resistance during solder reflow, and excellent temperature cycle test reliability. An object of the present invention is to provide a composition and an optical semiconductor device using the composition and having high reliability.

（Ｂ）上記構造式（１）で表されるエポキシ樹脂以外のエポキシ樹脂〔ただし、トリグリシジルイソシアヌレートおよび下記の一般式（２）で表される脂環式エポキシ樹脂を除く〕。

（Ｃ）硬化剤。 In order to achieve the above object, the present invention provides an epoxy resin composition for encapsulating an optical semiconductor element containing the following components (A) to (C), which is a mixture of the components (A) and (B): The epoxy resin composition for sealing an optical semiconductor element in which the ratio [(A) :( B)] is set to (A) :( B) = 60: 40 to 95: 5 by weight ratio is the first. The gist.
(A) An epoxy resin represented by the following structural formula (1).

(B) Epoxy resins other than the epoxy resin represented by the structural formula (1) above (excluding triglycidyl isocyanurate and the alicyclic epoxy resin represented by the following general formula (2)).

(C) Curing agent.

  And this invention makes the 2nd summary the optical-semiconductor device formed by carrying out transfer molding of the optical-semiconductor element using the said epoxy resin composition for optical-semiconductor-element sealing.

  The inventors of the present invention have made a series of studies to obtain an epoxy resin composition for sealing an optical semiconductor element that is excellent in crack resistance during solder reflow. As a result, when the epoxy resin [component (A)] represented by the structural formula (1) and the other epoxy resin (component (B)) are combined at a specific ratio, the solder reflow temperature (rubber-like region) The low-temperature elastic modulus of the resin is lower than that of the conventional epoxy resin, and it is possible to relieve the stress generated by vaporization expansion when reflow is applied, and of course, the generation of cracks is suppressed and the solder reflow resistance is excellent. The present inventors have found that the glass transition temperature is increased and that the reliability of the temperature cycle test can be improved.

  Thus, the present invention is a light comprising the epoxy resin [component (A)] represented by the above structural formula (1) and the other epoxy resin [component (B)] in a specific mixing ratio. An epoxy resin composition for encapsulating semiconductor elements. For this reason, it is excellent in crack resistance at the time of solder reflow, and also has excellent temperature cycle test reliability because of its high glass transition temperature. Therefore, the epoxy resin composition for sealing an optical semiconductor element of the present invention becomes a useful sealing material, and a highly reliable optical semiconductor device can be obtained.

  Next, embodiments of the present invention will be described in detail.

  The epoxy resin composition for sealing an optical semiconductor element of the present invention (hereinafter simply referred to as “epoxy resin composition”) includes an epoxy resin (A component) represented by a specific structural formula and an epoxy resin other than the A component. It is obtained using (B component) and a curing agent (C component), and is usually in the form of a powder or a tablet obtained by tableting this powder.

  The epoxy resin (component A) represented by the specific structural formula is an epoxy resin represented by the following structural formula (1).

  In the above formula (1), the repeating number n is a positive number, and more preferably n is 1 to 2. And it is preferable that an epoxy equivalent is 400-1300, More preferably, it is 400-800. Moreover, it is preferable that a softening point is 50-130 degreeC, More preferably, it is 70-110 degreeC.

  The epoxy resin (component B) other than the component A used together with the component A may be any one excluding triglycidyl isocyanurate and the alicyclic epoxy resin represented by the following general formula (2).

  Examples of the epoxy resin other than the component A (component B) include, for example, bisphenol A type epoxy resin, bisphenol F type epoxy resin, 3,4-epoxycyclohexenylmethyl-3 ′, 4′-epoxycyclohexene carboxylate, And a biphenyl type epoxy resin represented by the general formula (3). These may be used alone or in combination of two or more.

  The biphenyl type epoxy resin represented by the above formula (3) is more preferably a biphenyl type epoxy resin in which R is a methyl group. Furthermore, it is preferable to use an epoxy resin having an epoxy equivalent of 80 to 250 as an epoxy resin (B component) other than the A component. Moreover, it is preferable to use a thing with a softening point or melting | fusing point of 40-125 degreeC.

  The mixing ratio [(A component) :( B component)] of the epoxy resin (component A) represented by the structural formula (1) and the epoxy resin (component B) other than the component A is (weight ratio) (component A) ): (Component B) = 60: 40 to 95: 5 is required to be set. More preferably, (A component) :( B component) = 70: 30 to 90:10. That is, if the mixing ratio is out of the above range and the ratio of the component A is too small, the elastic modulus at the time of solder reflow increases, stress cannot be relieved, and cracks occur at the time of solder reflow resistance. . On the other hand, if the mixing ratio is out of the above range and the ratio of the component A is too large, the glass transition temperature (Tg) is lowered and the solder reflow resistance is improved. The reliability of itself decreases. Further, heat resistance is lowered, discoloration during solder reflow is severe, and optical properties are affected.

  The curing agent (C component) used together with the A component and the B component acts as a curing agent for the A component and the B component, and conventionally known curing agents for epoxy resins are used. In particular, it is preferable to use an acid anhydride-based curing agent from the viewpoint that the cured product of the epoxy resin composition is not easily discolored.

  Examples of the acid anhydride-based curing agent include phthalic anhydride, maleic anhydride, trimellitic anhydride, pyromellitic anhydride, hexahydrophthalic anhydride, tetrahydrophthalic anhydride, methyl nadic anhydride, nadic anhydride, anhydrous Colorless to light yellow acid anhydrides such as glutaric acid, methylhexahydrophthalic anhydride, methyltetrahydrophthalic anhydride and the like can be mentioned. These may be used alone or in combination of two or more. Of the acid anhydride curing agents, hexahydrophthalic anhydride and methylhexahydrophthalic anhydride are preferably used from the viewpoint of lower absorption in the short wavelength region.

  Further, in addition to the acid anhydride curing agent, the acid anhydride curing agent esterified with glycols, or carboxylic acids such as hexahydrophthalic acid, tetrahydrophthalic acid, methylhexahydrophthalic acid, etc. Curing agents may be used alone or in combination of two or more.

  The blending ratio of the epoxy resin component (A component + B component) and the curing agent (C component) is, for example, when an acid anhydride curing agent is used as the curing agent (C component), the epoxy resin component (A component + B). It is preferable to set the acid anhydride equivalent in the acid anhydride curing agent to 0.5 to 1.5 equivalents with respect to 1 equivalent of the epoxy group in the component. Particularly preferred is 0.7 to 1.2 equivalents. That is, in the above blending ratio, when the acid anhydride equivalent is less than the above lower limit value, the hue after curing of the resulting epoxy resin composition tends to be deteriorated, and conversely, when the above upper limit value is exceeded, moisture resistance is increased. This is because there is a tendency to decrease.

  In addition, as a curing agent (C component), in addition to the acid anhydride-based curing agent, when the curing agent such as carboxylic acids such as hexahydrophthalic acid is used alone or in combination of two or more, the blending ratio is According to the blending ratio (equivalent ratio) using the above acid anhydride curing agent.

  The epoxy resin composition of the present invention can contain a curing accelerator if necessary. Examples of the curing accelerator include tertiary amines, imidazoles, quaternary ammonium salts and organometallic salts, phosphorus compounds and the like. These may be used alone or in combination of two or more. And among the said hardening accelerators, it is preferable to use a phosphorus compound and tertiary amines. More preferably, 1,8-diazabicyclo [5.4.0] undecene-7 (DBU), 1,5-diazabicyclo [4.3.0] nonene-5, DBU octylate, N, N-dimethyl Examples include benzylamine, tetra-n-butylphosphonium-o, o-diethyl phosphorodithioate, and N, N-dimethylcyclohexylamine. By using these, the effect that heat discoloration at the solder reflow temperature hardly occurs can be obtained.

  The blending amount of the curing accelerator is preferably set in the range of 0.05 to 7.0 parts with respect to 100 parts by weight of the epoxy resin component (component A + component B) (hereinafter abbreviated as “part”). More preferably, it is 0.2 to 3.0 parts. That is, if the blending amount of the curing accelerator is too small, there is a tendency that a sufficient curing accelerating effect cannot be obtained, and conversely, if too large, the cured product of the epoxy resin composition tends to be discolored. It is.

  The epoxy resin composition of the present invention includes the epoxy resin (component A) represented by the structural formula (1), an epoxy resin other than the component A (component B), a curing agent (component C), and a curing accelerator. In addition, as long as it does not impair the transparency of the cured product of the epoxy resin composition, conventionally used deterioration inhibitors, modifiers, silane coupling agents, defoaming agents, release agents are used. Various conventionally known additives such as dyes and pigments can be appropriately blended.

  Examples of the deterioration preventing agent include conventionally known agents such as phenol compounds, amine compounds, organic sulfur compounds, and phosphine compounds.

  Examples of the modifier include conventionally known modifiers such as glycols, silicones, and alcohols.

  As said silane coupling agent, conventionally well-known silane coupling agents, such as a silane system and a titanate system, are mention | raise | lifted, for example.

  Examples of the defoaming agent include conventionally known defoaming agents such as silicone-based ones.

  Examples of the release agent include conventionally known agents such as stearic acid, behenic acid, montanic acid and metal salts thereof, polyethylene, polyethylene-polyoxyethylene, and carnauba wax. And among the said mold release agents, since the transparency of the hardening body of an epoxy resin composition becomes favorable, polyethylene-polyoxyethylene type | system | group is used preferably.

  In addition, when a light dispersibility is required, you may mix | blend a filler other than the said component. Examples of the filler include inorganic fillers such as quartz glass powder, talc, silica powder, alumina powder, and calcium carbonate.

  The epoxy resin composition of the present invention can be produced, for example, as follows. That is, the above A component, B component and C component, and further, if necessary, curing accelerators, deterioration inhibitors, modifiers, silane coupling agents, defoaming agents, mold release agents, dyes, pigments, fillers, etc. Various conventionally known additives are blended at a predetermined ratio. Then, these are mixed and kneaded by appropriately adopting a dry blend method or a melt blend method according to a conventional method. Subsequently, the obtained kneaded product is cooled and then pulverized, and further tableted as necessary, whereby the epoxy resin composition of the present invention can be produced.

  Sealing of the optical semiconductor element using such an epoxy resin composition can be performed by a known molding method such as transfer molding.

  The cured product of the epoxy resin composition of the present invention preferably has a light transmittance of 70% or more at a wavelength of 600 nm as measured by a spectrophotometer at a thickness of 1 mm, particularly preferably 80% or more. However, the light transmittance in the case of using the filler, dye, or pigment is not limited to this.

  Moreover, it is preferable that the glass transition temperature (Tg) in the hardening body of the epoxy resin composition of this invention is 110 degreeC or more, More preferably, it is the range of 110-150 degreeC. Further, the storage elastic modulus at a temperature 50 ° C. higher than the glass transition temperature (Tg) is preferably 2 to 14 MPa, more preferably 3 to 14 MPa. By having such characteristics, the epoxy resin composition of the present invention is excellent in solder reflow resistance and temperature cycle test reliability. The glass transition temperature (Tg) is measured by, for example, a differential scanning calorimeter (DSC) using a cured epoxy resin composition, and the intermediate point between two bending points appearing before and after the glass transition temperature. Determine the temperature (Tg). Moreover, the said storage elastic modulus is measured by RSA-II made from RHEOMETRIC SCIENTIFIC, for example using the epoxy resin composition hardened | cured body and the temperature range of 1 Hz and 30-270 degreeC on the measurement conditions of 10 degreeC / min. be able to.

  Next, examples will be described together with comparative examples. However, the present invention is not limited to these examples.

  First, prior to the examples and comparative examples, the following components were prepared.

〔エポキシ樹脂ｅ〕
３，４−エポキシシクロヘキセニルメチル−３′，４′−エポキシシクロヘキセンカルボキシレート（エポキシ当量１３４） [Epoxy resin a]
Epoxy resin represented by the structural formula (1) [in formula (1), n = 1, epoxy equivalent 540: manufactured by Tohto Kasei Co., Ltd., ZX-1718-3]
[Epoxy resin b]
Bisphenol A type epoxy resin (epoxy equivalent 185, liquid)
[Epoxy resin c]
Bisphenol F type epoxy resin (epoxy equivalent 170, liquid)
[Epoxy resin d]
Biphenyl type epoxy resin represented by the following structural formula (d) (epoxy equivalent 193, melting point 105 ° C.)

[Epoxy resin e]
3,4-epoxycyclohexenylmethyl-3 ', 4'-epoxycyclohexenecarboxylate (epoxy equivalent 134)

[Curing agent]
Hexahydrophthalic anhydride

[Curing accelerator]
N, N-dimethylbenzylamine [silane coupling agent]
γ-mercaptotrimethoxysilane

[Examples 1-9, Comparative Examples 1-9]
Each component shown in Table 1 and Table 2 below is blended in the proportions shown in the same table, melt-kneaded for 3 minutes in a mixing roll heated to 80 to 130 ° C., aged, and then until room temperature (25 ° C.) The target powdery epoxy resin composition was obtained by cooling and pulverizing.

  Using the epoxy resin compositions of Examples and Comparative Examples thus obtained, various characteristics were evaluated according to the methods described below. The results are also shown in Tables 1 and 2 above.

[Glass transition temperature (Tg)]
Using each epoxy resin composition produced as described above, molding with a dedicated mold (curing conditions: molding at 150 ° C. for 4 minutes) to obtain a cured specimen (size: diameter 50 mm × thickness 1 mm) Was made. This was completely cured by heating at 150 ° C. for 3 hours. Next, using a test piece that has been completely cured, the sample was measured with a differential scanning calorimeter (DSC: DSC-6220, manufactured by Seiko Instruments Inc.), and an intermediate between two bending points appearing before and after the glass transition temperature. The point was made into glass transition temperature (Tg).

[Storage modulus]
Using each epoxy resin composition produced as described above, molding with a dedicated mold (curing conditions: molding at 150 ° C. for 4 minutes) to obtain a cured specimen (size: width 5 mm × length 35 mm) X thickness 1 mm). This was completely cured by heating at 150 ° C. for 3 hours. Next, the storage elastic modulus was measured under a measurement condition of 10 ° C./min in a temperature range of 1 Hz and 30 to 270 ° C. by using RSA-II manufactured by RHEOMETRIC SCIENTIFIC, using a test piece that had been completely cured. . That is, the storage elastic modulus is a measured value at a temperature 50 ° C. higher than the measured glass transition temperature (Tg).

[Solder reflow resistance]
An optical semiconductor element (SiN photodiode: 1.5 mm × 1.5 mm × thickness 0.37 mm) is molded by transfer molding (150 ° C. × 4 minutes molding, 150 ° C. × 3 hours post-curing) using the epoxy resin composition. As a result, a surface mount type optical semiconductor device was obtained. As shown in FIG. 1, this surface-mount type optical semiconductor device is an 8-pin small outline package (SOP-8: 4.9 mm × 3.9 mm × thickness 1.5 mm) 1 and a 42 alloy as a lead frame 2. What formed the silver plating layer (thickness 0.2 micrometer) on the whole surface of the alloy element | base_body was used. The wire diameter is 25 μm.

  Ten optical semiconductor devices thus obtained were absorbed by 192 hours under the conditions of 30 ° C./60% RH and passed through an actual reflow furnace (top peak 260 ° C. × 10 seconds) three times. Thereafter, the resin interface between the lead frame and the element was visually observed with a microscope for the presence or absence of cracks, and the number of optical semiconductor devices in which this occurred was counted.

[Temperature cycle test]
The optical semiconductor device evaluated by the solder reflow resistance was subjected to a temperature cycle test of 300 cycles with 100 ° C. to −40 ° C. as one cycle, and wire breakage and continuity were checked. In the evaluation of solder reflow resistance, the optical semiconductor device in which peeling and cracking occurred was not subjected to a temperature cycle test.

  From the above results, all of the examples had glass transition temperatures (Tg) of 110 ° C. or higher, and the storage elastic modulus was kept low. Good results were obtained in solder reflow resistance and temperature cycle tests.

  On the other hand, in the solder reflow resistance test, peeling and cracking occurred in the products of Comparative Examples 1 to 4 in which the mixing ratio of the two types of epoxy resins was outside the specific range and the mixing ratio of the epoxy resin a was small. Moreover, although the mixing ratio of two types of epoxy resins deviated from a specific range and the mixing ratio of the epoxy resin a was too large, the comparative examples 6 to 9 had a low storage elastic modulus. Disconnection and continuity failure occurred. Similarly, in Comparative Example 5 using only the epoxy resin a, the glass transition temperature (Tg) was as low as 100 ° C., and the storage elastic modulus was kept low. However, wire breakage and poor conduction occurred in the temperature cycle test.

It is a perspective view which shows SOP-8 which is an example of a surface mount optical semiconductor device.

Claims (4)

An epoxy resin composition for encapsulating an optical semiconductor element containing the following components (A) to (C), wherein the mixing ratio [(A) :( B)] of the components (A) and (B) is: An epoxy resin composition for sealing an optical semiconductor element, wherein the weight ratio is set to (A) :( B) = 60: 40 to 95: 5.
(A) An epoxy resin represented by the following structural formula (1).

(B) Epoxy resins other than the epoxy resin represented by the structural formula (1) above (excluding triglycidyl isocyanurate and the alicyclic epoxy resin represented by the following general formula (2)).

(C) Curing agent. The epoxy resin (B) other than the epoxy resin represented by the structural formula (1) is bisphenol A type epoxy resin, bisphenol F type epoxy resin, 3,4-epoxycyclohexenylmethyl-3 ', 4'-epoxycyclohexene. 2. The epoxy resin composition for sealing an optical semiconductor element according to claim 1, wherein the epoxy resin composition is at least one epoxy resin selected from the group consisting of a carboxylate and a biphenyl type epoxy resin represented by the following general formula (3).

  The epoxy resin composition for sealing an optical semiconductor element according to claim 1 or 2, wherein the epoxy resin composition for sealing an optical semiconductor element has a glass transition temperature of 110 ° C or higher.   The optical semiconductor device formed by carrying out transfer molding of an optical semiconductor element using the epoxy resin composition for optical semiconductor element sealing as described in any one of Claims 1-3.

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