JP2001335621A - Epoxy resin composition and semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an epoxy resin composition for semiconductor sealing which is excellent in low hygroscopicity, high fluidity and curability. SOLUTION: The composition comprises (A) an epoxy resin, (B) an ortho- cresol novolac resin wherein a binuclear component content is 10-25 wt.% and the melt viscosity at 150 deg.C is 0.35 Pa.s or less, (C) an inorganic filler and (D) a curing accelerator as the essential components. It is characterized in that the equivalent ratio of phenolic hydroxyl groups in whole phenolic resin to epoxy groups in whole epoxy resin is 0.5 to 2.0, the content of the inorganic filler (C) is 200 to 2,400 pts.wt. based on 100 pts.wt. of the total of the whole epoxy resin (A) and whole phenolic resin (B) and the content of the curing accelerator (D) is 0.4 to 20 pts.wt. based on 100 pts.wt. of the total of the whole epoxy resin and whole phenolic resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an epoxy resin composition for semiconductor encapsulation having excellent solder cracking resistance due to low moisture absorption, excellent fluidity and rapid curing, and a semiconductor device using the same. It is.

[0002]

2. Description of the Related Art Conventionally, diodes, transistors and I
In order to protect semiconductor components such as C and LSI from external stimuli (mechanical / thermal shock, chemical action, etc.), encapsulation molding is performed with an epoxy resin composition in consideration of productivity and cost. Is becoming more common. On the other hand, in contrast to the recent improvement in the degree of integration of semiconductors and the accompanying increase in the dimensions of semiconductors, there has been a demand for smaller and thinner semiconductor devices due to the recent downsizing of electronic devices, and the demand for printed circuit boards has been increasing. Since the mounting method has also shifted from the conventional pin insertion type to the surface mounting type, problems such as cracks in semiconductor devices due to thermal shock during the surface mounting soldering process and separation between the chip / lead frame and the cured product of the resin composition have occurred. There is a strong demand for an epoxy resin composition that is easily generated and has excellent heat resistance. It is believed that these cracks and peeling are caused by the semiconductor device itself before the soldering process absorbs moisture and the moisture causes a steam explosion at a high temperature during the soldering process. Techniques such as imparting low hygroscopicity are often used. One of the techniques for reducing hygroscopicity is to use a low-viscosity crystalline epoxy resin to increase the amount of the inorganic filler and reduce the content of the resin component. There is technology.

[0003] Conventionally, there is a biphenyl type epoxy resin as an epoxy resin used in such a method, which is often used for a highly filled resin composition of an inorganic filler. However, even in the case of a biphenyl type epoxy resin, it is not easy to mix an inorganic filler in an epoxy resin composition in an amount of 90% by weight or more in production, and a higher level of production technology is required to realize it. In addition, the production cost is increased, and improvement of the hygroscopicity by increasing the amount of the inorganic filler cannot be expected any more.

[0004] One of the means for increasing the production efficiency is to shorten the molding time. For this purpose, rapid curing at the time of molding is required. In a phenol novolak resin that has been widely used in the past, if a sufficient amount of a curing accelerator is added to exhibit rapid curing at the time of molding, poor filling may occur due to a decrease in fluidity at the time of molding, or a semiconductor element Gold wire is disconnected, and conduction failure occurs. There is also a problem that the storage stability at room temperature is extremely reduced.

[0005]

DISCLOSURE OF THE INVENTION The present invention provides an epoxy resin composition for semiconductor encapsulation which is further improved in low moisture absorption and rapid curing by using a specific phenol resin, and a semiconductor element using the same. It is intended to provide a sealed semiconductor device.

[0006]

According to the present invention, the content of a binuclear compound in (A) an epoxy resin and (B) a novolak resin of the general formula (1) is 10 to 25% by weight in the resin. And 15
A novolak resin represented by the general formula (1) having a melt viscosity at 0 ° C. of 0.35 Pa · s or less, (C) an inorganic filler,
And (D) a curing accelerator as an essential component, wherein the equivalent ratio of phenolic hydroxyl groups of all phenolic resins to epoxy groups of all epoxy resins is 0.5 to 2.0, and inorganic filler (C)
Is 200 to 2400 parts by weight per 100 parts by weight of the total amount of all epoxy resins (A) and all phenolic resins (B), and the content of the curing accelerator (D) is 0.1 per 100 parts by weight of total amount.
An epoxy resin composition for encapsulating a semiconductor, wherein the composition is 4 to 20 parts by weight, and a semiconductor device obtained by encapsulating a semiconductor element using the composition.

Embedded image (R in the formula is an alkyl group having 1 to 4 carbon atoms. N is an average value and is a positive number of 1 or more.)

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The epoxy resin used in the present invention refers to all monomers, oligomers and polymers having two or more epoxy groups in one molecule, and their molecular weight and molecular structure are not particularly limited. For example, biphenyl type epoxy resin, bisphenol type epoxy resin,
Stilbene epoxy resin, phenol novolak epoxy resin, cresol novolak epoxy resin, triphenolmethane epoxy resin, alkyl-modified triphenolmethane epoxy resin, epoxy resin containing triazine nucleus, dicyclopentadiene-modified phenol epoxy resin, phenol aralkyl Type epoxy resin (having a phenylene skeleton, a diphenylene skeleton and the like) and the like, and these may be used alone or in combination. The epoxy resin used in the present invention preferably has a melt viscosity as low as possible, and has a melt viscosity at 150 ° C. of 0.30 Pa · s or less, more preferably 0.10 P
a · s or less is desirable. When an epoxy resin is used in combination, it indicates the melt viscosity of the melt mixture. By lowering the melt viscosity, the inorganic filler is highly filled to reduce moisture absorption, and the resulting semiconductor device has improved solder crack resistance. Furthermore, the fluidity of the resin composition can be improved, and the deformation of the gold wire at the time of molding can be prevented.

The novolak resin represented by the general formula (1) used in the present invention has an alkyl group and is characterized by low hygroscopicity, and reduces the moisture absorption of a cured product of an epoxy resin composition using the novolak resin. As a result, the solder crack resistance of the obtained semiconductor device can be improved. Further, by having an alkyl group, the reactivity between the phenolic hydroxyl group and the epoxy resin is improved, and the resin is rapidly cured. If it is a phenol novolak resin having no alkyl group, if the molecular weight is reduced and the melt viscosity is reduced, the softening point is also reduced, the phenol novolak resin becomes sticky at room temperature, and the consolidation of the resin composition powder using this, Since tablet sticking occurs and handling workability is inferior, reduction in melt viscosity is limited, and the inorganic filler cannot be filled at a high level. Furthermore, since the softening temperature of the resin composition also decreases, the storage stability deteriorates.
Even if the melt viscosity is reduced by the introduction of the alkyl group, the softening point does not decrease so much, so that the handling workability, the preservability of the resin composition is maintained, and the inorganic filler can be highly filled, Solder crack resistance of the obtained semiconductor device can be improved. R in the general formula (1) is
An alkyl group having 1 to 4 carbon atoms and having 5 or more carbon atoms is not preferred because steric hindrance increases, the reaction with an epoxy group is inhibited, and curability is significantly reduced.

The novolak resin represented by the general formula (1) used in the present invention is not only a single alkylphenol having 1 to 4 carbon atoms, but also the bonding position of the alkyl group or the alkyl group is different in the range of 1 to 4 carbon atoms. Alkyl phenols may be simultaneously contained. The alkyl group may be substituted at the ortho position, the para position, or the meta position, but the ortho position is preferred because the reaction with the epoxy group is faster and the product is easily available as an industrial product. Further, a methyl group is preferable as the alkyl group from the balance between low hygroscopicity and rapid curing. The most preferred alkyl phenol is orthocresol.

The novolak resin represented by the general formula (1) used in the present invention has a binuclear content in the resin of:
Those containing 10 to 25% by weight are preferred. 10% by weight
If it is less than 1, the viscosity of the novolak resin sharply increases, the fluidity of the resin composition is greatly reduced, and the viscosity increases, which causes deformation of a gold wire and pad shift during molding. If it exceeds 25% by weight, the ratio of the resin having three or more phenolic hydroxyl groups in the novolak resin becomes too small, and the curability is lowered. In the present invention, the amount of binucleate is
It is a value obtained from a peak order and a peak area by a general GPC (Gel Permeation Chromatography) method. If the proportion of the binuclear body in the novolak resin represented by the general formula (1) is within the above range, the melt viscosity is preferably as low as possible, and the melt viscosity at 150 ° C. is 0.35 Pa ·
s or less, more preferably 0.30 Pa · s. If the melt viscosity is low, the fluidity is improved, and the moisture absorption is reduced by increasing the amount of the inorganic filler, whereby the solder crack resistance of the obtained semiconductor device can be improved. The melt viscosity of the epoxy resin and the novolak resin of the general formula (1) in the present invention is measured by an ICI cone & plate viscometer (Research).
Equipment Co., Ltd.) at 150 ° C. The novolak resin represented by the general formula (1) used in the present invention can be obtained, for example, by reacting an alkylphenol with formaldehyde (formalin) in the presence of an acid catalyst, but is not particularly limited.

The phenol resin may be used in combination with another phenol resin as long as the properties of the novolak resin represented by the general formula (1) are not impaired. Examples of the phenol resin that can be used in combination include phenol novolak resin, dicyclopentadiene-modified phenol resin, terpene-modified phenol resin, triphenolmethane-type resin, and phenol aralkyl resin (having a phenylene skeleton, a diphenylene skeleton, and the like). May be used alone or as a mixture. When used in combination, it is desirable that the novolak resin of the general formula (1) be contained in an amount of 50% by weight or more in all phenol resins. If it is less than 50%, the inherent effects of the novolak resin of the present invention, such as low hygroscopicity and rapid curability, may not be sufficiently exhibited. The equivalent ratio of the epoxy group of all epoxy resins to the phenolic hydroxyl group of all phenol resins is preferably 0.5 to 2.0, particularly preferably 0.7 to 1.5. If the ratio is out of the range of 0.5 to 2, the curability, the moisture resistance reliability and the like are undesirably reduced.

The type of the inorganic filler used in the present invention is not particularly limited, and those generally used for a sealing material can be used. For example, fused crushed silica powder, fused spherical silica powder, crystalline silica powder, secondary aggregated silica powder, alumina, titanium white, aluminum hydroxide and the like are mentioned, and fused spherical silica is particularly preferred. The shape is preferably infinitely spherical, and the filling amount can be increased by mixing particles having different particle sizes. The compounding amount of the inorganic filler is preferably 200 to 2400 parts by weight, more preferably 40 to 40 parts by weight per 100 parts by weight of the total amount of all epoxy resins and all phenolic resins.
0 to 1900 parts by weight is preferred. If the amount is less than 200 parts by weight, the reinforcing effect of the inorganic filler is not sufficiently exhibited, and the amount of the resin component that is a factor of moisture absorption is increased. ,
It is not preferable because the fluidity of the resin composition is reduced and there is a possibility that defective filling may occur during molding. It is preferable that the inorganic filler used in the present invention is sufficiently mixed in advance. If necessary, the inorganic filler may be treated in advance with a coupling agent, an epoxy resin or a phenol resin, and may be used. The method of the treatment includes a method of removing the solvent after mixing with a solvent or a method of directly filling the inorganic filler. There is a method of adding to the material and treating using a mixer

As the curing accelerator used in the present invention, any one can be used as long as it promotes the curing reaction between the epoxy group and the phenolic hydroxyl group, and those generally used for a sealing material can be used. For example, 1,8-diazabicyclo (5,4,0) undecene-7, triphenylphosphine, 2-methylimidazole, tetraphenylphosphonium / tetraphenylborate and the like can be mentioned, and these may be used alone or as a mixture. Absent. The compounding amount of the curing accelerator is preferably 0.4 to 20 parts by weight per 100 parts by weight of the total amount of all epoxy resins and all phenolic resins. If the amount is less than 0.4 part by weight, sufficient curability may not be obtained at the time of heat molding, while if it exceeds 20 parts by weight, curing is too fast and poor fluidity due to a decrease in fluidity during molding. This is not preferable because of the possibility of causing the like.

The epoxy resin composition of the present invention comprises (A)
In addition to the component (D), if necessary, brominated epoxy resins, antimony oxide, phosphorus compounds, magnesium hydroxide, boric acid compounds and other flame retardants, bismuth oxide hydrates and other inorganic ion exchangers, γ-glycide Coupling agents such as xypropyltrimethoxysilane, coloring agents such as carbon black and red bean, low stress components such as silicone oil and silicone rubber, release of natural wax, synthetic wax, higher fatty acids and their metal salts or paraffin, etc. Various additives such as an agent and an antioxidant can be blended. The epoxy resin composition of the present invention is obtained by mixing components (A) to (D), other additives, and the like at room temperature using a mixer,
It is obtained by a general method of melt-kneading with a kneader such as a kneader or an extruder, followed by cooling and pulverizing. In order to manufacture a semiconductor device by encapsulating an electronic component such as a semiconductor element using the epoxy resin composition of the present invention, the molding may be performed by a molding method such as a transfer mold, a compression mold, and an injection mold.

[0015]

EXAMPLES Examples of the present invention will be shown below, but the present invention is not limited to these examples. The mixing ratio is by weight. The abbreviations and structures of the epoxy resin and the phenol resin used in the examples and comparative examples are summarized below.
Equivalents of epoxy resin and phenol resin, melting point, softening point, melt viscosity / 150 ° C, content of binuclear substance, Example 5
[Epoxy resin (1) / Epoxy resin (2) = 2.5 /
2.6 (weight ratio), Example 6 [epoxy resin (1) / epoxy resin (5) = 3.2 / 2.1 (weight ratio) melt mixture], Example 8 [epoxy resin] (1)
/ Epoxy resin (2) = 2.5 / 2.6 (weight ratio) melt mixture] / 150 ° C. is shown in Table 1. The melt viscosity and the content of the binuclear body were measured by the method described above. Epoxy resin (1): an epoxy resin having a structure represented by the formula (3) as a main component

Embedded image

Epoxy resin (2): an epoxy resin having a structure represented by the formula (4) as a main component

Embedded image

Epoxy resin (3): an epoxy resin having a structure represented by the formula (5) as a main component

Embedded image

Epoxy resin (4): an epoxy resin represented by the formula (6)

Embedded image

Epoxy resin (5): epoxy resin represented by formula (7)

Embedded image

[0020]

[Table 1]

Example 1 Epoxy resin (1) 5.3 parts by weight Orthocresol novolak resin (1) 3.4 parts by weight Fused spherical silica 89.0 parts by weight 1,8-diazabicyclo (5,4,0) undecene- 7 (hereinafter referred to as DBU) 0.2 part by weight Brominated bisphenol A type epoxy resin (epoxy equivalent 359, viscosity 0.13 Pa · s / 150 ° C.) 0.5 part by weight Inorganic ion exchanger 0.4 part by weight Oxidation 0.3 parts by weight of antimony 0.3 parts by weight of carbon black 0.2 parts by weight of γ-glycidoxypropyltrimethoxysilane 0.4 parts by weight of carnauba wax were mixed using a mixer.
The mixture was kneaded 30 times using two rolls at 5 ° C., and the obtained kneaded material sheet was cooled and pulverized to obtain a resin composition. The properties of the obtained resin composition were evaluated by the following methods. Table 2 shows the results.

Evaluation method Spiral flow: Using a mold for spiral flow measurement in accordance with EMMI-1-66, a mold temperature of 175 ° C.
The measurement was performed at an injection pressure of 70 kg / cm ² and a curing time of 2 minutes.
The unit is cm. Moisture absorption: Using a transfer molding machine, mold temperature 17
A molded product having a diameter of 50 mm and a thickness of 3 mm was molded at 5 ° C., an injection pressure of 75 kg / cm ² , and a curing time of 2 minutes.
After curing for a time, the obtained molded article was heated to 85 ° C. and a relative humidity of 8
The sample was left for 168 hours in an environment of 5%, the change in weight was measured, and the moisture absorption was calculated. The unit is% by weight. Curability: Using a JSR Curastometer IVPS manufactured by Orientec Co., Ltd., the diameter of the die was 35 mm, the amplitude angle was 1 °, the molding temperature was 175 ° C., and the torque value 45 seconds after the start of molding was measured. The smaller the value, the slower the curing. The unit is kgf · cm. Solder crack resistance: Using a transfer molding machine, mold temperature 175 ° C, injection pressure 75kg / c
m ² , curing time: 2 minutes, 100 pTQFP (package size: 14 × 14 mm, thickness: 1.4 mm, dimensions of semiconductor element: 8.0 × 8.0 mm, lead frame: 42 alloy), 175 ° C., 8 After post-curing, the resulting package was left at 85 ° C. and 85% relative humidity for 168 hours, and then immersed in a 240 ° C. solder bath for 10 seconds. Observe the package with a microscope and observe the external crack occurrence rate [(number of cracked packages) / (total number of packages)
× 100]. Units%. The ratio of the peeled area between the semiconductor element and the cured product of the resin composition was measured using an ultrasonic flaw detector, and the peeling rate [(peeled area) / (semiconductor element area) × 100] was determined. Units%.

Examples 2 to 8 and Comparative Examples 1 to 5 Resin compositions were obtained in the same manner as in Example 1 according to the formulations in Table 2, and evaluated in the same manner as in Example 1. Table 2 shows the results.

[Table 2]

[0024]

The epoxy resin composition of the present invention has low hygroscopicity, high fluidity, and rapid curability. A semiconductor device encapsulated with the epoxy resin composition has low hygroscopicity and excellent solder crack resistance. I have.

Claims (5)

[Claims] The content of a binuclear substance in (A) an epoxy resin and (B) a novolak resin of the general formula (1) is 10 to 25% by weight in the resin, and a melt viscosity at 150 ° C. A novolak resin represented by the general formula (1) of not more than 0.35 Pa · s, (C) an inorganic filler, and (D) a curing accelerator are essential components, and phenol of all phenolic resins with respect to epoxy groups of all epoxy resins. The equivalent ratio of the hydroxyl group is 0.5 to 2.0, and the content of the inorganic filler (C) is 10 in total of the total epoxy resin (A) and the total phenol resin (B).
0 to 2400 parts by weight per 0 parts by weight, and the content of the curing accelerator (D) is 0.4 to 20 parts by weight per 100 parts by weight of the total amount of all epoxy resins and all phenolic resins. Epoxy resin composition for semiconductor encapsulation. Embedded image (R in the formula is an alkyl group having 1 to 4 carbon atoms. N is an average value and is a positive number of 1 or more.) 2. The epoxy resin composition for semiconductor encapsulation according to claim 1, wherein the epoxy resin has a melt viscosity at 150 ° C. of 0.30 Pa · s or less. 3. The epoxy resin composition for semiconductor encapsulation according to claim 1, wherein the novolak resin represented by the general formula (1) is a novolak resin represented by the general formula (2). Embedded image (R in the formula is an alkyl group having 1 to 4 carbon atoms. N is an average value and is a positive number of 1 or more.) 4. The novolak resin of the general formula (1) wherein R is
The epoxy resin composition for semiconductor encapsulation according to claim 1, 2 or 3, which is a methyl group. 5. A semiconductor device comprising a semiconductor element encapsulated with the epoxy resin composition according to claim 1.