JP5367274B2 - Epoxy resin composition for optical semiconductor element sealing and optical semiconductor device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an epoxy resin composition for sealing an optical semiconductor element which has excellent crack resistance in reflow soldering. <P>SOLUTION: The epoxy resin composition for sealing an optical semiconductor element comprises the following (A)-(C) components, wherein the content of polyalkylene diol of the (C) component is set to be 5-30 pts.wt. based on 100 pts.wt. (A) component and the storage elastic module of the epoxy resin composition cured body is 3-8 MPa in a temperature range equal to and above the glass transition point of the epoxy resin composition cured body. (A) is an epoxy resin containing following (a) &ge;60 wt.% of the epoxy resin component [(A) component], wherein (a) is an epoxy resin solid at ordinary temperature, (B) is a curing agent and (C) is polyalkylene diol having average molecular weight of 300-1,000. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to an epoxy resin composition for optical semiconductor elements (hereinafter referred to as “epoxy resin composition”) having transparency excellent in solder crack resistance and an optical semiconductor device sealed with the resin. .

  Even in optical semiconductor devices in which optical semiconductor elements such as light emitting diodes (LEDs) are encapsulated in resin, surface mounting methods are used instead of conventional pin insertion mounting methods for the purpose of reducing size and weight and improving mounting productivity. It is spreading rapidly.

In such a surface mounting method, unlike the pin insertion mounting method, the entire package is exposed to a high temperature environment of 215 to 260 ° C. during mounting. At that time, the moisture absorbed during storage after manufacturing the optical semiconductor device is rapidly vaporized and expanded due to the high temperature, and a large stress is generated. When the stress exceeds the strength of the package, there arises a problem that cracks occur. As measures to prevent the occurrence of cracks, optical semiconductor manufacturers, for example, carry out moisture-proof packaging when shipping optical semiconductor devices, and at the mounting site, the optical semiconductor devices are heated and dried in an oven before the mounting process. In addition, a method for removing moisture from moisture absorption is employed. Furthermore, the sealing resin composition includes a method of containing an inorganic filler such as a filler. Moreover, the method of lowering | hanging a water absorption is mention | raise | lifted by raising the content rate of the aliphatic group in a resin, or a phenyl group (for example, refer patent document 1).
JP 2001-226450 A

  However, the countermeasure method using the moisture-proof packaging has a problem that the cost is increased due to the packaging and the workability is deteriorated due to the opening of the packaging. Further, the above-described countermeasure method by heat drying has a problem that the cost of heat drying becomes a large burden. Furthermore, in the sealing resin composition containing an inorganic filler such as the filler, the transparency tends to decrease in the optical semiconductor application. And in the method of lowering the water absorption rate by increasing the content of aliphatic groups and phenyl groups in the resin, the glass transition temperature is increased and the elastic modulus at the time of solder reflow is increased, so that the moisture at the time of reflow is increased. The stress due to vaporization and expansion cannot be relaxed, and cracks may occur. Furthermore, in recent years, from the viewpoint of environmental protection, lead-free has been promoted, and accordingly, the mounting temperature has increased from 240 ° C. to 260 ° C., and further solder crack resistance is desired.

  The present invention has been made in view of such circumstances, and an object thereof is to provide an epoxy resin composition having excellent crack resistance during solder reflow and an optical semiconductor device using the same.

In order to achieve the above object, the present invention provides an epoxy resin composition for encapsulating an optical semiconductor element for transfer molding containing the following components (A) to (C): The content of a certain polyalkylene diol is set in the range of 5 to 20 parts by weight with respect to 100 parts by weight of the component (A), and the cured epoxy resin composition (curing condition: 150 ° C. × 5 minutes + 150 ° C. An epoxy resin composition having a storage elastic modulus of 3 to 8 MPa in a temperature region equal to or higher than the glass transition point of (× 3 hours) is a first gist.
(A) An epoxy resin containing 60% by weight or more of the following (a) epoxy resin component [component (A)].
(A) An epoxy resin that is solid at room temperature.
(B) Curing agent.
(C) A polyalkylene diol having a number average molecular weight of 300 to 1,000.

  Moreover, this invention makes the 2nd summary the optical semiconductor device formed by resin-sealing an optical semiconductor element using the said epoxy resin composition.

That is, the present inventors have intensively studied to obtain an optical semiconductor element sealing material having transparency and excellent resistance to cracking during solder reflow. Then, focusing on the rigidity of the sealing resin formed by the sealing material, that is, the cured body, a series of studies were repeated for the purpose of alleviating the stress that causes cracks. As a result, as a blending component, the polyalkylene diol having the number average molecular weight is used at a specific ratio, and the storage elastic modulus in the temperature region above the glass transition point of the cured epoxy resin composition containing the polyalkylene diol is described above. When set to a specific range, not only has transparency, but also a low elastic modulus is achieved, and it is possible to relieve stress by flexing or vibrating the generated stress during vaporization expansion, and solder reflow The present inventors have found that the crack resistance at the time is excellent and have reached the present invention.

Thus, the present invention provides a polyalkylene having the number average molecular weight together with an epoxy resin (component (A)) and a curing agent (component (B)) containing a specific amount of an epoxy resin (a) that is solid at room temperature. Transfer molding in which the diol [(C) component] is contained at a specific ratio, and the storage elastic modulus in the temperature range above the glass transition point of the cured epoxy resin composition containing these components is set in a specific range. An epoxy resin composition for use. For this reason, the stress which arises at the time of solder reflow is eased, and generation | occurrence | production of a crack is suppressed effectively. Therefore, the optical semiconductor device in which the optical semiconductor element is sealed with the epoxy resin composition of the present invention is excellent in reliability and transparency, and can fully exhibit its function.

  The epoxy resin composition of the present invention is obtained using an epoxy resin (component A), a curing agent (component B), and a specific polyalkylene diol (component C). Used as a tablet tablet.

  Examples of the epoxy resin (component A) include bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, alicyclic epoxy resin, triglycidyl isocyanurate, and hydantoin epoxy resin. Nitrogen-containing ring epoxy resin, water-added bisphenol A type epoxy resin, aliphatic epoxy resin, glycidyl ether type epoxy resin, bisphenol S type epoxy resin, biphenyl type epoxy resin which is the mainstream of low water-absorption-curing type, dicyclo Examples thereof include a ring type epoxy resin and a naphthalene type epoxy resin. These may be used alone or in combination of two or more. Among these epoxy resins, bisphenol A type epoxy resin, bisphenol F type epoxy resin, alicyclic epoxy resin, triglycidyl isocyanate from the point that the cured product of the epoxy resin composition is difficult to discolor after sealing of the optical semiconductor element. It is preferable to use nurate.

  And as said epoxy resin (A component), it contains the epoxy resin (a) which shows solid at normal temperature, The content rate of this epoxy resin (a) which shows solid at normal temperature is an epoxy resin (A component) It is necessary to set it to 60% or more of the whole. Therefore, the entire epoxy resin (component A) may be composed of an epoxy resin (a) that is solid at room temperature. In addition, in this invention, normal temperature means the range of 10-50 degreeC. As such an epoxy resin (a) which is solid at normal temperature, for example, one having a softening point of 100 ° C. or lower is preferable. Specifically, bisphenol A type epoxy resin, bisphenol F type epoxy resin, alicyclic epoxy resin and the like can be mentioned.

  As the curing agent (component B), it is particularly preferable to use an acid anhydride curing agent from the viewpoint that the cured product of the epoxy resin composition is hardly discolored. As the acid anhydride curing agent, those having a molecular weight of about 140 to 200 are preferably used. For example, tetracarboxylic anhydride, phthalic anhydride, maleic anhydride, trimellitic anhydride, pyromellitic anhydride, hexahydrophthalic anhydride Examples thereof include colorless and light yellow acid anhydrides such as acid, tetrahydrophthalic anhydride, methyl nadic anhydride, nadic anhydride, glutaric anhydride, methyl hexahydrophthalic anhydride, and methyltetrahydrophthalic anhydride. These may be used alone or in combination of two or more. Of these acid anhydride curing agents, phthalic anhydride, hexahydrophthalic anhydride, tetrahydrophthalic anhydride, and methylhexahydrophthalic anhydride are preferably used.

  Further, as the curing agent (component B), in addition to the acid anhydride curing agent, a conventionally known amine curing agent, phenol curing agent, hexahydrophthalic acid, tetrahydrophthalic acid, methylhexahydrophthalic acid A curing agent such as carboxylic acid may be used in combination.

  The mixing ratio of the epoxy resin (component A) and the curing agent (component B) is, for example, when an acid anhydride curing agent is used as the curing agent (component B), the epoxy group in the epoxy resin (component A). It is preferable to set to a ratio such that the acid anhydride equivalent in the acid anhydride is 0.5 to 1.5 equivalents relative to 1 equivalent, and more preferably 0.7 to 1.2 equivalents. That is, in the above blending ratio, when the acid anhydride equivalent is less than 0.5 equivalent, the hue after curing of the resulting epoxy resin composition tends to deteriorate, and conversely when it exceeds 1.5 equivalent, This is because the moisture resistance tends to decrease. In addition, as the curing agent (component B), in addition to the above acid anhydride curing agent, the amine curing agent, the phenol curing agent, or a curing agent such as carboxylic acid alone or in combination of two or more, The blending ratio is in accordance with the blending ratio (equivalent ratio) when the acid anhydride curing agent is used.

  Examples of the polyalkylene diol (C component) used together with the epoxy resin (A component) and the curing agent (B component) include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polytetraethylene glycol, polypentaethylene glycol, Examples include polyhexaethylene glycol. These may be used alone or in combination of two or more. Among these, it is preferable to use polyethylene glycol, polypropylene glycol, polytetramethylene glycol, or polytetraethylene glycol.

And as said polyalkylene diol (C component), it is necessary to use a number average molecular weight of the range of 300-1000. The number average molecular weight is particularly preferably 300 to 700. That is, if the number average molecular weight is less than the lower limit value, a considerable excess amount is required to obtain the effect, resulting in problems such as poor curability and increased water absorption. Moreover, when a number average molecular weight exceeds an upper limit, it will become difficult to melt | dissolve with the epoxy resin composition which shows solid, phase separation will arise, and transparency will be impaired. In addition, the measurement of the number average molecular weight of the said polyalkylenediol (C component) is performed as follows, for example. That is, the hydroxyl value in a sample is calculated | required according to JISK-1557-1, and it substitutes and calculates to the following numerical formula. In the following formula, N is the number of functional groups in one molecule of the sample, and 56.1 is the molecular weight of KOH.
Number average molecular weight = (56.1 / hydroxyl value in sample) × N × 1000

The content of the polyalkylene diol (component C) needs to be set in the range of 5 to 20 parts with respect to 100 parts by weight of the epoxy resin composition (hereinafter abbreviated as “part”) . Ie, not obtained a sufficient effect is less than the lower limit value, if the upper limit value in the opposite, because the curable failure or water absorption is increased.

  And the conventionally well-known various silane coupling agent can be used for the epoxy resin composition of this invention with said AC component. By using the silane coupling agent, it is possible to improve the adhesive force with an optical semiconductor element, a lead frame, etc., and there is an effect that reliability is improved.

  The epoxy resin composition of the present invention may contain a curing accelerator, if necessary, in addition to the components A to C and the silane coupling agent.

  The curing accelerator is not particularly limited, and examples thereof include 1,8-diazabicyclo (5,4,0) undecene-7, triethylenediamine, tri-2,4,6-dimethylaminomethylphenol. Tertiary amines, imidazoles such as 2-ethyl-4-methylimidazole and 2-methylimidazole, triphenylphosphine, tetraphenylphosphonium / tetraphenylborate, tetra-n-butylphosphonium-o, o-diethylphosphorodithio And phosphorus compounds such as ate, quaternary ammonium salts, organometallic salts, and derivatives thereof. These may be used alone or in combination of two or more. Of these curing accelerators, tertiary amines and imidazoles are preferably used.

  It is preferable to set content of the said hardening accelerator to 0.05-7.0 parts with respect to 100 parts of said epoxy resins (A component), More preferably, it is 0.2-3.0 parts. That is, if it is less than 0.05 part, it is difficult to obtain a sufficient curing accelerating effect, and if it exceeds 7.0 parts, the cured product of the resulting epoxy resin composition may be discolored.

  In addition, in the epoxy resin composition of this invention, if it is a range which does not impair the transparency of the hardening body of an epoxy resin composition other than said AC component, a silane coupling agent, and a hardening accelerator, as needed. Various known additives such as antioxidants, modifiers, mold release agents, dyes, pigments and the like that have been conventionally used can be appropriately blended.

  Examples of the antioxidant include conventionally known antioxidants 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.

  Examples of the release agent include conventionally known ones such as stearic acid, behenic acid, montanic acid and metal salts thereof, polyethylene wax, polyethylene-polyoxyethylene wax, carnauba wax and the like. Of the above releasing agents, polyethylene-polyoxyethylene-based waxes are preferable because the transparency of the cured product of the epoxy resin composition is good.

  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 blending amount of such a filler is appropriately set according to the purpose such as light dispersibility.

  The epoxy resin composition of the present invention can be obtained, for example, in the form of a powder or a tablet obtained by tableting the powder by manufacturing as follows. That is, the above-mentioned components A to C, in addition to the silane coupling agent and, if necessary, an additive to be blended in a predetermined ratio. Then, this is melt kneaded by appropriately adopting a dry blend method or a melt blend method according to a conventional method. Subsequently, after cooling this to room temperature, it can grind | pulverize by a well-known means and can also manufacture by tableting as needed.

The epoxy resin composition of the present invention thus obtained is used for sealing an optical semiconductor element such as an LED or a charge coupled device (CCD). That is, using the epoxy resin composition of the present invention, an optical semiconductor element sealed can be performed more transfer forming the shape of the normal. In addition, when the epoxy resin composition of this invention is a powder form or a tablet form, when melt-mixing each above-mentioned component, it may be set as B stage (semi-hardened state), and this may be heat-melted at the time of use. .

The epoxy resin composition of the present invention is a thermosetting resin composition in the temperature range above the glass transition point of the cured body (curing condition: 150 ° C. × 5 minutes + 150 ° C. × 3 hours). In the epoxy resin composition, it is necessary that the storage elastic modulus of the rubber-like region which is a temperature region above the glass transition point is 3 to 8 MPa. That is, if it is less than 3 MPa, it is very soft at the glass transition temperature or more and is difficult to be molded as a molded product. Conversely, if it exceeds 8 MPa, the stress relaxation ability against vaporization and expansion of water during reflow is poor and cracks are likely to occur. Because it becomes. By realizing such a low elastic modulus, it is possible to relieve the stress generated at the time of vaporization and expansion of moisture absorption in the package, and the solder reflow resistance is excellent. In the present invention, the temperature region above the glass transition point of the cured epoxy resin composition is, for example, a region from the glass transition temperature to + 50 ° C. Moreover, an upper limit is 240-260 degreeC normally.

  In addition, the storage elastic modulus in the temperature range (rubber-like region) above the glass transition point of the cured body is measured as follows using a dynamic viscoelasticity measuring machine. That is, using a dynamic viscoelasticity measuring device RSA-III manufactured by RHEOMETRIC SCIENTIFIC, measurement is performed at a temperature range of 1 Hz and 30 to 270 ° C. under measurement conditions of 10 ° C./min. The size of the test piece is 35 mm long × 5 mm wide × 1 mm thick.

  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.

  Next, examples will be described together with comparative examples.

  First, each component shown below was prepared.

[Epoxy resin a]
Bisphenol F type epoxy resin (epoxy equivalent 950, melting point 85 ° C)

[Epoxy resin b]
1,2-epoxy-4- (2-oxiranyl) cyclohexene adduct of 2,2-bis (hydroxymethyl) -1-butanol (epoxy equivalent 185)

[Epoxy resin c]
Bisphenol A type epoxy resin (epoxy equivalent 185, liquid)

[Curing agent]
Tetrahydrophthalic anhydride

[Curing accelerator]
2-ethyl-4-methylimidazole

[Polytetramethylene glycol a]
Number average molecular weight 250

[Polytetramethylene glycol b]
Number average molecular weight 500

[Polytetramethylene glycol c]
Number average molecular weight 1000

[Polypropylene glycol a]
Number average molecular weight 400

[Polypropylene glycol b]
Number average molecular weight 700

[Polypropylene glycol c]
Number average molecular weight 1300

[Examples 1-5 , Comparative Examples 1-8]
Each component shown in Table 1 to Table 2 described below is blended in the proportions shown in the same table, melt kneaded (80 to 130 ° C.) with a mixing roll, aged, cooled, solidified at room temperature, and pulverized. A fine powder epoxy resin composition was prepared.

  Using each epoxy resin composition thus obtained, the transparency of the cured product, and the storage elastic modulus and transparency of the temperature region (rubbery region) above the glass transition point of the cured product are shown below. It was measured and evaluated according to the method. Further, using each of the obtained epoxy resin compositions, an optical semiconductor device was produced according to the following method, and solder reflow resistance was measured and evaluated. These results are shown in Tables 1 and 2 below.

〔transparency〕
A cured product having a thickness of 1 mm was prepared using each epoxy resin composition (curing conditions: 150 ° C. × 5 minutes + 150 ° C. × 3 hours). And using the said hardening body, the light transmittance of wavelength 600nm was measured using the spectrophotometer UV3101 by Shimadzu Corporation. As a result, the light transmittance of less than 70% was evaluated as x, and the light transmittance of 80% or more was evaluated as ○.

[Storage modulus]
It measured as follows using the dynamic-viscoelasticity measuring machine. That is, a test piece having a length of 35 mm, a width of 5 mm, and a thickness of 1 mm was formed (curing conditions: 150 ° C. × 5 minutes + 150 ° C. × 3 hours), and a dynamic viscoelasticity measuring device RSA-III manufactured by RHEOMETRIC SCIENTIFIC was used. The measurement was performed under the measurement conditions of 10 ° C./min in a temperature range of 1 Hz and 30 to 270 ° C.

[Solder reflow resistance]
Using each epoxy resin composition, an optical semiconductor element (chip size: 1.5 mm × 1.5 mm × thickness 0.37 mm) placed on an epoxy substrate having a thickness of 0.6 mm is transfer molded (molding condition: 150 ° C. × 4 The optical semiconductor device (package size: 7.8 mm × 5.2 mm × thickness 1.5 mm) was manufactured by further curing under conditions of 150 ° C. × 3 hours. The optical semiconductor device thus obtained was left in a constant temperature and humidity chamber of 30 ° C./85% RH for 96 hours, and then this optical semiconductor device was exposed to infrared (IR) reflow 260 ° C. The state of peeling and crack generation was observed with a stereomicroscope. The number of good packages with no problems was displayed without any element peeling or cracks in the package. The number of samples (n number) of each optical semiconductor device was 10.

  From the above results, the example product had a good transparency, and a highly reliable optical semiconductor device excellent in solder reflow resistance was obtained.

  On the other hand, the epoxy resin which is solid at normal temperature is less than a specific ratio, or a polyalkylene diol whose average molecular weight is out of a specific range is used, or the content of polyalkylene diol is out of the above range. In each comparative product, a molded body could not be produced (Comparative Examples 4, 6, and 8) or the storage elastic modulus was out of the specific range, resulting in poor solder reflow resistance. It was.

Claims (2)

An epoxy resin composition for encapsulating an optical semiconductor element for transfer molding containing the following components (A) to (C), wherein the content of the polyalkylenediol as the component (C) is the above (A) The temperature is set in the range of 5 to 20 parts by weight with respect to 100 parts by weight of the component, and in the temperature region above the glass transition point of the cured epoxy resin composition (curing conditions: 150 ° C. × 5 minutes + 150 ° C. × 3 hours) An epoxy resin composition for sealing an optical semiconductor element, having a storage elastic modulus of 3 to 8 MPa.
(A) An epoxy resin containing 60% by weight or more of the following (a) epoxy resin component [component (A)].
(A) An epoxy resin that is solid at room temperature.
(B) Curing agent.
(C) A polyalkylene diol having a number average molecular weight of 300 to 1,000.   An optical semiconductor device obtained by resin-sealing an optical semiconductor element using the epoxy resin composition for sealing an optical semiconductor element according to claim 1.