JP4040367B2 - Epoxy resin composition and semiconductor device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an epoxy resin composition for semiconductor encapsulation excellent in high-temperature storage characteristics and electrical moisture resistance reliability, and a semiconductor device.
[0002]
[Prior art]
Conventionally, electronic components such as diodes, transistors, and integrated circuits are mainly sealed using an epoxy resin composition. In particular, an integrated circuit uses an epoxy resin composition excellent in heat resistance and moisture resistance in which an epoxy resin, a phenol resin, and an inorganic filler such as fused silica or crystalline silica are blended.
However, in recent years, with the trend toward smaller, lighter, and higher performance electronic devices, higher integration of semiconductor elements has been progressing year by year, and surface mounting of semiconductor devices has been promoted. The demands on the epoxy resin compositions used are becoming increasingly severe. In particular, the surface mounting of semiconductor devices is becoming common, and moisture-absorbing semiconductor devices are exposed to high temperatures during solder reflow processing, and peeled off at the interface between the semiconductor element and lead frame and the cured epoxy resin composition. As a result, defects that greatly impair the reliability of the semiconductor device, such as cracks in the semiconductor device, occur, and prevention of these defects, that is, improvement in resistance to solder cracks is a major issue.
Furthermore, as part of the elimination of environmentally hazardous substances, replacement with lead-free solder is being promoted. Since solder containing no lead has a higher melting point than conventional solder, the reflow temperature at the time of surface mounting is about 20 ° C. higher than before and requires 260 ° C. By changing the solder reflow temperature for soldering that does not contain lead, the peeling of the epoxy resin composition at the interface between the cured product and the pad, and the peeling at the interface between the semiconductor element and the semiconductor resin paste, The problem of cracks has arisen. These solder cracks and delamination are considered to be caused by moisture absorption by the semiconductor device itself before the solder reflow process, and its moisture causing a steam explosion at a high temperature during the solder reflow process. , Using high-filled inorganic fillers, using low-hygroscopic or tough epoxy resins or phenolic resins to give low-hygroscopic properties to epoxy resin compositions, improving strength, etc. It has been. However, even an epoxy resin composition using these techniques is insufficient as an epoxy resin composition corresponding to solder containing no lead, and further improvement is desired.
[0003]
The epoxy resin composition usually contains a halogen-based flame retardant such as a bromine-containing organic compound and an antimony compound such as niantimony trioxide and niantimony tetroxide in order to impart flame retardancy. In many cases, a semiconductor device using an epoxy resin composition using these raw materials has a low stability of electrical characteristics under high temperature or high humidity of 100 to 260 ° C., that is, the resistance value of the semiconductor device is low. It has been pointed out that there is a problem that the conduction failure of the semiconductor element occurs with time, and the electrical moisture resistance reliability and high temperature storage property are poor.
In recent years, there has been a movement to reduce or eliminate substances that may be harmful due to the importance of corporate activities in consideration of the global environment. Epoxy resin compositions with excellent flame resistance without using halogenated flame retardants and antimony compounds As an alternative to environmentally friendly flame retardants, metal hydroxides such as aluminum hydroxide and magnesium hydroxide have been used. With these uses, the problems of electrical moisture resistance reliability and high-temperature storage stability have decreased, however, when produced in the same production equipment as the epoxy resin composition using halide and antimony compound, Even when materials that do not use halides and antimony compounds are manufactured, residual halides and residual antimony compounds are mixed in a small amount. As a result, semiconductor devices using the epoxy resin composition have electrical moisture resistance reliability and high-temperature storage stability. The problem of not being satisfied occurred.
[0004]
[Problems to be solved by the invention]
The present invention is excellent in flame retardancy without using a conventional flame retardant, excellent in moldability and solder crack resistance, and further excellent in high temperature storage characteristics and electrical moisture resistance reliability. A resin composition and a semiconductor device are provided.
[0005]
[Means for Solving the Problems]
[1] (A) Epoxy resin represented by general formula (2), epoxy resin represented by formula (6), (B) phenol resin represented by general formula (3), (C) silica, alumina Alternatively, an inorganic filler selected from silicon nitride and a curing accelerator represented by (D) formula (4) are essential components, and the total amount of (C) inorganic filler is 70 with respect to the total epoxy resin composition. -92 wt%, (D) The content of the curing accelerator represented by the formula (4) is 0.05-0.5 wt%, the content of Br atom measured by fluorescent X-ray is 15 ppm or less, antimony An epoxy resin composition for encapsulating a semiconductor, wherein the atomic content is 75 ppm or less,
[0006]
[Chemical 1]
[0010]
[ 2 ] A semiconductor device comprising a semiconductor element sealed with the epoxy resin composition according to item [1] ,
It is.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail.
The curing accelerator represented by the general formula (1) used in the present invention is a molecule of tetra-substituted phosphonium and 2,3-dihydroxynaphthalene, which is very excellent in terms of stability and curability of the molecular compound and physical properties of the cured product. It is an association. It is thought that it is composed of a tetra-substituted phosphonium cation and an organic anion, and the organic anion surrounds the positive charge of the tetra-substituted phosphonium ion and has a stabilized structure. Since the curing accelerator represented by the general formula (1) does not exhibit catalytic activity at room temperature, the curing reaction of the epoxy resin composition does not proceed and the catalytic activity is exhibited at a high temperature during molding, thereby curing the epoxy resin composition. It has the feature to make. In addition, since there is a characteristic that the catalytic activity is suddenly expressed in a relatively narrow temperature range, at the initial stage when the epoxy resin composition using this is injected into the molding die, the reaction does not proceed greatly, Since the melt viscosity at that time is low, sufficient fluidity is maintained even if the amount of the inorganic filler is increased, and as a result of increasing the amount of the inorganic filler, flame retardancy and solder crack resistance are improved. Moreover, since the epoxy resin composition can be hardened by the high catalytic activity after the completion of the injection, excellent moldability is exhibited. As the phosphonium ion, a tetra-substituted phosphonium ion having a substituted or unsubstituted aryl group or alkyl group as a substituent is preferable because it is stable against heat and hydrolysis. Specifically, tetraphenylphosphonium, tetratolylphosphonium, etc. And tetraaryl-substituted phosphonium, triarylphosphine such as triphenylmethylphosphonium, triarylmonoalkylphosphonium synthesized from alkyl halide, tetraalkyl-substituted phosphonium such as tetrabutylphosphonium, and the like.
[0012]
As described in the prior art, when producing with the same production equipment as the epoxy resin composition using halide and antimony compound, even if the production equipment is carefully cleaned, the halogenless and antimonyless epoxy resin composition Even if it is produced, the halogen and antimony-containing epoxy resin composition produced immediately before that may be mixed in about 0.5% by weight, that is, about 10 ppm as the halogen atom amount and about 50 ppm as the antimony atom amount. And, the electrical moisture resistance reliability and high-temperature storage stability of the semiconductor device using the epoxy resin composition in which a small amount of halogen atoms and antimony atoms are mixed are better than the epoxy resin composition containing halide and antimony compound. However, it is not sufficient, and in order to further improve the electrical moisture resistance reliability and high-temperature storage property of the semiconductor device, it is necessary to further remove some halogen atoms and antimony atoms. The 2,3-dihydroxynaphthalene in the curing accelerator represented by the general formula (1) used in the present invention reacts with one antimony molecule with respect to three 2,3-dihydroxynaphthalene molecules to form a chelate structure. Since it has a characteristic of capturing, it has an excellent characteristic that it can avoid adverse effects on electrical moisture resistance reliability and high-temperature storage stability caused by an antimony compound mixed in a small amount in the resin composition in the production process. Yes. After actually preparing an epoxy resin composition using 0.5% by weight of a Br-phenol novolac epoxy resin having a Br content of 35% by weight as a halide and 0.5% by weight of antimony trioxide as an antimony compound, In addition, when an epoxy resin composition using 0.5 wt% of the curing accelerator represented by the formula (4) was prepared in the same production apparatus, the antimony atom was stabilized by reacting with 2,3-dihydroxynaphthalene. Although the semiconductor device using the epoxy resin composition has few halogen atoms, it has excellent electrical moisture resistance reliability and high temperature storage property. It was also confirmed that the incorporation of about 10 ppm of halogen atoms did not significantly affect the electrical moisture resistance reliability and high temperature storage stability.
[Chemical 7]
(M represents a number of 0 ≦ m ≦ 2.)
[0013]
The curing accelerator represented by the general formula (1) used in this patent needs to be contained in an amount of 0.05 to 0.5% by weight with respect to the total epoxy resin composition. If the value is below the lower limit, it is not preferable because the anti-mony mixture may reduce the electrical moisture resistance reliability and high-temperature storage property of the semiconductor device, and the curability of the epoxy resin composition may be insufficient. On the other hand, if the upper limit is exceeded, the fluidity at the time of molding the epoxy resin composition is lowered, and there is a possibility that the problem of unfilling at the time of molding may be unfavorable.
[0014]
Moreover, as a hardening accelerator, except for imidazole compounds such as 2-methylimidazole that reduce electrical moisture resistance reliability and high-temperature storage stability, epoxy groups and phenolic hydroxyl groups generally used in sealing materials as needed Those that accelerate the curing reaction may be used in combination. For example, diazabicycloalkenes such as 1,8-diazabicyclo (5,4,0) undecene-7 and derivatives thereof, amine compounds such as tributylamine and benzyldimethylamine, tetraphenylphosphonium tetranaphthoic acid borate, tri Examples include, but are not limited to, organophosphorus compounds such as phenylphosphine. Two or more kinds of these curing accelerators may be used in combination. Among these, 1,8-diazabicyclo (5,4,0) undecene-7 is particularly effective for improving adhesion to various substrates, and tetraphenylphosphonium tetranaphthoic acid borate is This has the effect of greatly improving the room temperature storage characteristics of the epoxy resin composition.
[0015]
The epoxy resin used in the present invention is not limited as long as it has two or more epoxy groups in one molecule. For example, phenol novolac type epoxy resin, orthocresol novolak type epoxy resin, naphthol novolak type epoxy resin , Phenol aralkyl type epoxy resin (having phenylene skeleton, biphenylene skeleton, etc.), naphthol aralkyl type epoxy resin (having phenylene skeleton, biphenylene skeleton, etc.), dicyclopentadiene modified phenol type epoxy resin, stilbene type epoxy resin, triphenolmethane Type epoxy resin, alkyl-modified triphenolmethane type epoxy resin, triazine nucleus-containing epoxy resin, and the like. These may be used alone or in combination of two or more.
[0016]
The phenol resin used in the present invention is not particularly limited as long as it has two or more phenolic hydroxyl groups in one molecule. For example, a phenol aralkyl resin (having a phenylene skeleton, a biphenylene skeleton, or the like), a naphthol aralkyl resin, or the like. (Having a phenylene skeleton, a biphenylene skeleton, etc.), terpene-modified phenolic resin, dicyclopentadiene-modified phenolic resin, bisphenol A, triphenolmethane type resin, etc. These may be used alone or in combination of two or more. You may use together.
[0017]
As a ratio (equivalent ratio) of the number of epoxy groups in all epoxy resins and the number of phenolic hydroxyl groups in all phenol resins and curing accelerator, (number of epoxy groups) / (number of phenolic hydroxyl groups) = 0.8 to 1.3 Preferably, out of this range, not only does the epoxy resin composition have low curability or glass transition temperature, but also the resistance of the semiconductor device increases with time at high temperature or high humidity. There is a possibility that a problem of deterioration in electrical moisture resistance reliability and high-temperature storage stability, in which an element conduction failure occurs, may occur.
[0018]
As the inorganic filler used in the present invention, those generally used for sealing materials can be widely used. For example, fused silica, spherical silica, crystalline silica, secondary agglomerated silica, porous silica, 2 Examples thereof include, but are not limited to, silica, alumina, silicon nitride and the like obtained by pulverizing secondary agglomerated silica or porous silica. These may be used alone or in combination of two or more. In particular, fused silica and crystalline silica are preferable.
The shape of the inorganic filler may be either crushed or spherical, but spherical fused silica from the viewpoint of high filling to improve solder crack resistance and the balance of fluidity, mechanical strength and thermal characteristics. Is preferred.
The maximum particle size is preferably 75 μm or less, and the average particle size is preferably 5 to 25 μm. A wide particle size distribution is effective for reducing the melt viscosity of the epoxy resin composition during molding. Further, a surface treated beforehand with a silane coupling agent or the like may be used.
[0019]
As a compounding quantity of an inorganic filler, 70 to 92 weight% is preferable in all the epoxy resin compositions. If the lower limit is not reached, the amount of epoxy resin or phenol resin used increases, resulting in poor high-temperature storage characteristics and electrical moisture resistance reliability. Further, the moisture absorption amount of the cured epoxy resin composition increases and the strength at the solder processing temperature decreases, so that the semiconductor device may be easily cracked during the solder processing. On the other hand, when the upper limit is exceeded, fluidity during molding of the epoxy resin composition is lowered, and there is a possibility that unfilling and pad shift of the semiconductor element are likely to occur. Adding as much inorganic filler as possible reduces the moisture absorption rate of the cured epoxy resin composition, improves the resistance to solder cracks, and improves the flame retardancy, allowing fluidity during molding. It is preferable to blend as much as possible within the range.
[0020]
The present invention achieves flame retardancy without containing halogen compounds and antimony compounds. The content of halogen atoms and antimony atoms in all epoxy resin compositions in the present invention is preferably 15 ppm or less and 75 ppm or less, respectively, more preferably 10 ppm or less and 50 ppm or less, respectively. This means that for economic reasons, halogen atoms and antimony atoms are not added, except for trace amounts of components mixed in the raw materials and production stage. On the other hand, the content of halogen atoms and antimony atoms is not included. Is within the above range, the effect of the curing accelerator represented by the general formula (1) can avoid adverse effects on electrical moisture resistance reliability and high-temperature storage properties.
In order to achieve flame retardancy without containing halogen compounds and antimony compounds, there are methods of blending metal hydroxides such as aluminum hydroxide and magnesium hydroxide, or using a flame retardant resin. However, in order to obtain flame retardancy using only metal hydroxide, it is necessary to add a relatively large amount of metal hydroxide. In this case, there is a problem of formability due to a decrease in curing characteristics and a linear expansion coefficient. Since a decrease in solder crack resistance due to the increase is seen, it is preferable to use a resin having flame retardancy of general formula (2) and general formula (3). Briefly explaining the cured product of the epoxy resin composition using the epoxy resin and phenol resin represented by the general formulas (2) and (3), the distance between the cross-linking points is long due to the hydrophobic structure between the epoxy groups and between the hydroxyl groups. Therefore, since the cured product of the epoxy resin composition is very soft at the temperature at the time of combustion, the pyrolysis gas generated inside the cured product at the time of combustion expands the layer of the cured product like rubber. It has a feature that it has a very high flame resistance due to the formation of a foamed layer, which blocks the oxygen to the unburned part by this foamed layer and has a heat insulation effect, and also has an elastic modulus at high temperatures exceeding the glass transition temperature. And the characteristics that it can withstand thermal stress during surface mounting soldering at 260 ° C. are also exhibited. Therefore, when the epoxy resin and the phenol resin represented by the general formula (2) and the general formula (3) are used, both flame retardancy and solder crack resistance have excellent characteristics without using a flame retardant. An epoxy resin composition is obtained. Moreover, also when using together another epoxy resin and a phenol resin, the epoxy resin shown by General formula (2) and the phenol resin shown by General formula (3) are respectively in all epoxy resins and all phenol resins. However, if it is contained in an amount of 70% by weight or more, these characteristics are not impaired. However, if it is less than 70% by weight, it is easy to burn, the moisture absorption rate is increased, and the solder crack resistance due to high elasticity is increased. A decline may occur.
[0021]
The epoxy resin composition of the present invention includes components (A) to (D), an inorganic ion exchanger such as bismuth oxide hydrate as necessary, and a coupling agent such as γ-glycidoxypropyltrimethoxysilane. , Colorants such as carbon black and bengara, low stress components such as silicone oil and silicone rubber, natural waxes, synthetic waxes, mold release agents such as higher fatty acids and their metal salts or paraffin, and various additives such as antioxidants Can be blended.
The epoxy resin composition of the present invention is mixed at room temperature using a mixer, etc., with components (A) to (D) and other additives, and after heat-kneading and cooling with a kneader such as a roll, kneader or extruder. It is obtained by grinding. The epoxy resin composition of the present invention can be applied to covering, insulating, sealing, and the like of transistors and integrated circuits that are electrical or electronic components.
In order to seal an electronic component such as a semiconductor element and manufacture a semiconductor device using the epoxy resin composition of the present invention, it may be molded and cured by a molding method such as a transfer mold, a compression mold, or an injection mold.
[0022]
【Example】
Examples of the present invention will be described in detail below, but the present invention is not limited thereto. The blending ratio of each component is weight%.
<Example 1>
[Chemical 8]
[0023]
[Chemical 9]
[0024]
[Chemical Formula 10]
[0025]
Embedded image
[0026]
Embedded image
[0027]
Spherical fused silica (average particle size 22 μm) 87.00 wt%
Carbon black 0.30% by weight
Carnauba wax 0.30% by weight
Hydrotalcite 0.30% by weight
γ-glycidoxypropyltrimethoxysilane 0.40% by weight
Were mixed at room temperature using a mixer, kneaded using a roll at 70 to 110 ° C., crushed after cooling, and tableted to obtain an epoxy resin composition. This epoxy resin composition was evaluated by the following method. The results are shown in Table 1.
[0028]
Evaluation method: Spiral flow: Using a mold for spiral flow measurement according to EMMI-1-66, measurement was performed at a mold temperature of 175 ° C., an injection pressure of 6.9 MPa, and a curing time of 120 seconds. The unit is cm.
Curability: Using JSR Curlastometer IVPS, manufactured by Orientec Co., Ltd., reaches 90% of the torque after 5 minutes at a die diameter of 35 mm, an amplitude angle of 1 °, and a molding temperature of 175 ° C. The time until was used as an index of curability. That is, the slower the time to reach 90%, the worse the cure. The unit is seconds.
・ Bending strength during heating ・ Bending elastic modulus during heating: Using a low-pressure transfer molding machine, a test piece with a mold temperature of 175 ° C., an injection pressure of 9.8 MPa, and a curing time of 120 seconds (width 10 mm, thickness 4 mm, length 80 mm) ) Was processed as a post cure at 175 ° C. for 8 hours, and then the hot bending strength and the hot bending elastic modulus were measured according to JIS K 6911 (at 260 ° C.). All units are N / mm ² .
-Moisture absorption: Using a low-pressure transfer molding machine, a disk-shaped test piece having a mold temperature of 175 ° C., an injection pressure of 9.8 MPa, a curing time of 120 seconds, a diameter of 50 mm, and a thickness of 3 mm was molded, and the post-cure was 8 at 175 ° C. Time processed. The weight change before the moisture absorption treatment of the test piece and after the moisture absorption treatment for 168 hours in an environment of 85 ° C. and 85% relative humidity was measured, and the moisture absorption rate of the test piece was shown as a percentage. The unit is% by weight.
Solder crack resistance: 160 pLQFP (thickness 1.4 mm, chip size 7 mm × 7 mm) was molded using a low-pressure transfer molding machine at a mold temperature of 175 ° C., an injection pressure of 9.3 MPa, and a curing time of 120 seconds. Five packages treated as post-cure at 175 ° C. for 8 hours were treated in an environment of 85 ° C. and a relative humidity of 60% for 168 hours, followed by IR reflow treatment (260 ° C.) (n = 5). The presence or absence of internal peeling or cracks after the treatment was observed with an ultrasonic flaw detector, and the number of defective packages was counted. When the number of defective packages is i, i / 5 is displayed.
Flame retardancy: Using a low-pressure transfer molding machine, a test piece was molded at a mold temperature of 175 ° C., an injection pressure of 6.9 MPa, a curing time of 120 seconds, treated as a post cure at 175 ° C. for 8 hours, and then UL- A 94 vertical test (test piece thickness: 3.2 mm) was conducted to determine flame retardancy.
-Antimony atom, Br atomic weight: Using a disk-shaped test piece having a diameter of 50 mm and a thickness of 3 mm, the moisture absorption rate was measured with a fluorescent X-ray apparatus, and the test piece was irradiated with X-rays to measure the antimony atom and Br atomic weight. did. The unit is ppm.
High temperature storage property: 16pDIP (chip size 3 mm × 3.5 mm) was molded using a low pressure transfer molding machine at a mold temperature of 175 ° C., injection pressure, 6.9 MPa, and curing time of 120 seconds. After curing at 175 ° C for 8 hours as a post cure, a high temperature storage test (185 ° C, 1000 hours and 200 ° C, 500 hours) is performed, and a package whose electrical resistance value between wirings is increased by 20% from the initial value is determined to be defective did. The defect rate among 10 wirings is shown as a percentage. Units%.
-Moisture resistance reliability: Molding 16SOP (thickness 1.95mm, chip size 3.5mm x 3.0mm) with mold temperature 175 ° C, injection pressure 9.8MPa, curing time 120 seconds using low pressure transfer molding machine did. After processing at 175 ° C. for 8 hours as post-cure, a pressure cooker test (125 ° C., pressure 2.2 MPa) was performed, and the open circuit failure was measured and expressed as the failure occurrence time. The unit is time.
[0029]
< Reference Examples 2-7 and 9, Example 8 , Comparative Examples 1-6>
The raw materials used other than Example 1 are shown below.
Epoxy resin f represented by formula (9) (ICI melt viscosity at 150 ° C. 6.7 × 10 2 mPa · s, epoxy equivalent 273, Br 35 wt% contained)
Embedded image
[0030]
1,8-diazabicyclo (5,4,0) undecene-7 (hereinafter referred to as DBU)
Aluminum hydroxide (average particle size 5μm)
Antimony trioxide [0031]
Epoxy resin compositions were obtained in the same manner as in Example 1 according to the formulations in Tables 1 and 2, and evaluated in the same manner as in Example 1. The results are shown in Tables 1 and 2.
[Table 1]
[0032]
[Table 2]
[0033]
【The invention's effect】
According to the present invention, it is excellent in flame retardancy without using a conventional flame retardant, excellent in moldability and solder crack resistance, and further excellent in high temperature storage characteristics and electrical moisture resistance reliability. An epoxy resin composition can be obtained.

Claims (2)

(A) an epoxy resin represented by the general formula (2), an epoxy resin represented by the formula (6), (B) a phenol resin represented by the general formula (3), and (C) silica, alumina or silicon nitride. And (D) the curing accelerator represented by the formula (4) as essential components, and the total amount of (C) inorganic filler is 70 to 92 weights based on the total epoxy resin composition. %, (D) the content of the curing accelerator represented by the formula (4) is 0.05 to 0.5% by weight, the content of Br atom measured by fluorescent X-ray is 15 ppm or less, the content of antimony atom An epoxy resin composition for encapsulating a semiconductor, wherein the amount is 75 ppm or less.
  A semiconductor device comprising a semiconductor element sealed with the epoxy resin composition according to claim 1.