JP2000281754A - Epoxy resin composition and semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a resin composition having excellent moldability, suited for use in, especially, a thin semiconductor device, and developing excellent soldering resistance when cured by mixing an epoxy resin composition containing crystalline and noncrystalline epoxy resins in a specified ratio with a phenolic resin, a fused silica powder, a cure accelerator, and a long-chain fatty acid amide. SOLUTION: The epoxy resin mixture used is a mixture containing 10-60 wt.% crystalline epoxy resin selected from among a biphenol epoxy resin of formula I, a bisphenol F epoxy resin of formula II, and a stilbene epoxy resin of formula III and 40-90 wt.% noncrystalline epoxy resin having at least three epoxy groups on the average. In the formulae, R is H, a halogen or a 1-9C alkyl. The amount of the fused silica powder used is desirably 75-93 wt.% based on the entire composition. The long-chain fatty acid amide used is exemplified by N-stearylstearamide, ethylenebisstearamide, N,N'-distearylsebacamide, or m-xylylenebisstearamide.

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 which has excellent moldability and solder resistance and is particularly suitable for thin semiconductor devices.

[0002]

2. Description of the Related Art Transfer molding of an epoxy resin composition has been employed as a method suitable for mass production at low cost as a method for encapsulating semiconductor devices such as ICs and LSIs. Improvements have been made by improving phenolic resins as curing agents. However, in the recent market trend of miniaturization, weight reduction and high performance of electronic devices, the integration of semiconductors has been increasing year by year, and the surface mounting of semiconductor devices has been promoted. Demands for resin compositions are becoming more stringent. For this reason, a problem that cannot be solved by the conventional epoxy resin composition has appeared. The biggest problem is that the semiconductor device is exposed to a high temperature of 200 ° C. or more in the solder immersion or reflow process due to the adoption of the surface mounting of the semiconductor device. This is a phenomenon in which the device breaks or peels off at each interface with various plated joints on the semiconductor element, the lead frame, and the inner lead, resulting in a significant decrease in reliability.

Further, in recent years, as semiconductor devices have become thinner, the thickness of the resin composition occupying in the semiconductor devices has been further reduced, and for semiconductor devices for 64M and 256M DRAMs, a 1 mm thick TSOP is becoming mainstream. . These thin semiconductor devices are required to have good package filling properties at the time of molding the resin composition, to have little gold wire deformation, and to have no deformation of semiconductor elements or lead frames (referred to as chip shift or die pad shift). Therefore, the resin composition is
It is necessary to have excellent fluidity during molding.

As an epoxy resin composition for encapsulating a semiconductor, a resin composition comprising an orthocresol novolak type epoxy resin, a phenol resin and an inorganic filler represented by fused silica has been generally used. This resin composition has a high reactivity at the time of molding because it involves a curing reaction between polyfunctional resins, and has a high cross-linking density after curing. It is widely used because it has features such as excellent heat resistance. However, ortho-cresol novolak type epoxy resin has a high melt viscosity at the molding temperature, is inferior in fluidity at the time of molding, has a limit to low moisture absorption because a large amount of inorganic filler cannot be blended, or has a limit in thin semiconductor devices. Further improvements are desired, such as poor filling properties and poor adhesion due to insufficient wettability with the substrate. For this reason, the molecular weight of the ortho-cresol novolak type epoxy resin is small, and an attempt has been made to improve the fluidity during molding by using a resin having a low softening temperature. It exhibits adhesiveness even at room temperature, causing the epoxy resin composition to be fused or deformed into tablets during the manufacturing process, the use process at the time of molding, and the like, resulting in extremely poor workability.

On the other hand, 3,3 ', 5,5'-
Crystalline epoxy resins such as biphenyl type epoxy resins represented by tetramethyl-4,4'-dihydroxybiphenyldiglycidyl ether have been developed and put to practical use. A resin composition using a biphenyl-type epoxy resin can easily achieve low moisture absorption due to the high filling of inorganic fillers, and also has excellent filling properties for thin semiconductor devices due to high fluidity during molding. ing. However, due to the limitation of bifunctional epoxy resin, the reactivity during molding is low and the curability and releasability are inferior, and the crosslink density after curing is low, so the heat resistance of the molded product is low and solder immersion is difficult. In this case, reliability such as solder resistance is also insufficient.

[0006]

In order to improve these drawbacks, epoxy resins having higher crystallinity than biphenyl type epoxy resins (hereinafter referred to as highly crystalline epoxy resins) and orthocresol novolak type epoxy resins have been proposed. Use of such a polyfunctional epoxy resin having an average of three or more epoxy groups in one molecule has been studied.
In particular, a resin obtained by heating and mixing a highly crystalline epoxy resin and a polyfunctional epoxy resin, or a highly crystalline phenol compound and a polyfunctional phenol compound, which are precursors of each epoxy resin, are heated and mixed in advance and then mixed with epichlorohydrin. The epoxidized resin does not exhibit tackiness at room temperature even when a low-softening point polyfunctional epoxy resin is used because the highly crystalline epoxy resin is crystallized in the polyfunctional epoxy resin. Excellent workability in the manufacturing process,
Furthermore, at the time of molding, the epoxy resin composition becomes highly fluid by melting and lowering the viscosity of the highly crystalline epoxy resin,
It has excellent filling properties for thin semiconductor devices, and after molding and curing, the rigid structure of the highly crystalline epoxy resin forms a crosslinked structure, giving molded products with high heat resistance and excellent solder resistance. It is effective for

However, since the epoxy resin composition has high crystallinity, it melts and recrystallizes during the heating and kneading of the epoxy resin composition, so that the crystallinity remains even after the heating and kneading. Since the crystal is melted for the first time at the time of molding, there are drawbacks of poor moldability, such as low curability, generation of burrs and voids, and easy surface staining of the molded semiconductor device. In addition, it was also found that a release agent component such as carnauba wax having low compatibility with the resin was separated and precipitated during the process of crystallizing the highly crystallized epoxy resin during heating and kneading. Due to the non-uniformity of the release agent, the releasability is poor, and contamination of the mold surface by the release agent also occurs. Further, since the degree of crystallization of the highly crystalline epoxy resin depends on the heating and kneading conditions, there is also a problem in production stability that it is difficult to obtain an epoxy resin composition having a constant fluidity even with the same composition. . In order to improve these,
A high-crystalline epoxy resin, a polyfunctional epoxy resin, and a phenol resin are melt-mixed in advance to prepare a uniform resin with few residual crystals, and then mixed with other components, and then heated and kneaded to obtain a uniform epoxy resin. Even if an attempt is made to obtain a resin composition, good moldability and production stability cannot be obtained because the highly crystalline epoxy resin has a property of being easily recrystallized at a kneading temperature of 80 to 110 ° C. As described above, the polyfunctional epoxy resin has curability, moldability and heat resistance after molding, and can realize low viscosity and high fluidity during molding even if a large amount of inorganic filler is blended, An epoxy resin composition having excellent moldability and production stability has not been developed, and its realization has been awaited.

[0008]

That is, the present invention relates to (A) 10 to 60% by weight of a crystalline epoxy resin represented by the general formulas (1) to (3) in the total epoxy resin, and An epoxy resin containing 40 to 90% by weight of a non-crystalline epoxy resin having an average of three or more epoxy groups in the total epoxy resin, (B) a phenol resin, (C) a fused silica powder,
(D) a curing accelerator, and (E) a long-chain fatty acid amide as essential components, an epoxy resin composition for semiconductor encapsulation, and a semiconductor element encapsulated with the epoxy resin composition. Semiconductor device.

Embedded image

[0009]

Embedded image

[0010]

Embedded image (R in the formula (3) is a group selected from a hydrogen atom, a halogen atom or an alkyl group having 1 to 9 carbon atoms, and may be the same or different from each other.)

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The epoxy resin used in the present invention comprises (A) a biphenyl type epoxy resin represented by the general formula (1):
A crystalline epoxy resin selected from the group consisting of a bisphenol F type epoxy resin of the general formula (2) and a stilbene type epoxy resin of the general formula (3) is contained in the total epoxy resin in an amount of 10 to 60% by weight, and one molecule. The epoxy resin contains 40 to 90% by weight of the total epoxy resin containing an amorphous epoxy resin having an average of three or more epoxy groups in the epoxy resin. Specific examples of the crystalline epoxy resin represented by the general formula (3) are shown below, but are not limited thereto.

Embedded image

The crystalline epoxy resins represented by the general formulas (1) to (3) are diepoxy resins having two epoxy groups in one molecule, and all have very strong crystallinity. Is a solid at the above temperature, but becomes a low-viscosity liquid at a temperature higher than the melting point. For this reason, even if a large amount of fused silica is blended, the resin composition has a low melt viscosity at the time of molding, is excellent in the filling property of a thin semiconductor device, has little gold wire deformation of a semiconductor element, and has little chip shift and die pad shift. It is essential that the crystalline epoxy resins represented by the general formulas (1) to (3) be contained in the total epoxy resin in an amount of 10 to 60% by weight. If the content is less than 10% by weight, the effect of lowering the viscosity is difficult to obtain, and a large amount of fused silica cannot be added, so that the molded product has a large moisture absorption and the semiconductor package has poor solder resistance. Further, the melt viscosity at the time of molding increases, and the moldability of the thin semiconductor device is poor. If it exceeds 60% by weight, the curability of the epoxy resin composition during molding is low, and the heat resistance of the cured product is low, so that the solder resistance is poor. On the other hand, non-crystalline epoxy resins having an average of three or more epoxy groups in one molecule include orthocresol novolak epoxy resin, dicyclopentadiene epoxy resin, triphenolmethane epoxy resin, naphthalene epoxy resin, phenol aralkyl Type epoxy resin and the like. An example is shown below.

[0013]

Embedded image

[0014]

Embedded image These epoxy resins contain 40 to 9 in the total epoxy resin.
It must be contained at 0% by weight. If it is less than 40% by weight, the curability of the epoxy resin composition during molding is low, and the heat resistance of the cured product is low, so that the solder resistance is poor. On the other hand, if the content exceeds 90% by weight, the viscosity becomes high, the filling property of the thin semiconductor device is poor, and the adhesiveness to the base material is poor, so that peeling is likely to occur at the interface with the base material during the soldering process. Therefore, the molded product has a large amount of moisture absorption, and the semiconductor device has poor solder resistance. The crystalline epoxy resin represented by the general formulas (1) to (3) and the non-crystalline epoxy resin having an average of three or more epoxy groups in one molecule are mixed with other components and then heated and kneaded. However, in order to further reduce the residual amount of the crystalline epoxy resin, these epoxy resins may be mixed and heated in advance, or more preferably, a phenol compound which is a precursor of each epoxy resin may be used. It can also be used as a resin mixture which is mixed and epoxidized by an ordinary method using epichlorohydrin or the like. It should be noted that there is no problem in using the crystalline epoxy resins represented by the general formulas (1) to (3) and the epoxy resins other than the non-crystalline epoxy resin having an average of three or more epoxy groups in one molecule.

The phenolic resin of the component (B) used in the present invention refers to all monomers, oligomers and polymers having a phenolic hydroxyl group capable of forming a crosslinked structure by curing reaction with an epoxy resin. Examples include, but are not limited to, aralkylphenol resins, terpene-modified phenol resins, dicyclopentadiene-modified phenol resins, bisphenol A, triphenolmethane, and the like. These phenolic resins can be used alone or in combination.

The fused silica powder of the component (C) used in the present invention refers to, for example, natural silica melted in a flame and synthetic silica obtained by hydrolyzing tetramethoxysilane, tetraethoxysilane and the like. . Further, they are classified into spherical silica and crushed silica according to their shapes and production methods. The blended amount of the fused silica powder of the component (C) used in the present invention is preferably 75 to 93% by weight in the whole resin composition. If the content is less than 75% by weight, the moisture absorption of the molded semiconductor device is increased, and the strength at the soldering temperature is reduced, so that the semiconductor device is likely to crack during the soldering process, which is not preferable. On the other hand, when the content exceeds 93% by weight, the fluidity during molding of the resin composition decreases, and unfilling, chip shift, and pad shift tend to occur, which is not preferable. In particular, spherical silica is used to highly fill the fused silica powder, and broadening the particle size distribution of the silica powder is effective for reducing the melt viscosity of the resin composition during molding flow.

The curing accelerator of the component (D) used in the present invention refers to those which can serve as a catalyst for a crosslinking reaction between the epoxy resin and the phenol resin. Specific examples thereof include tributylamine and 1,8-diazabicyclo ( Examples thereof include amine compounds such as (5,4,0) undecene-7, organic phosphorus compounds such as triphenylphosphine and tetraphenylphosphonium / tetraphenylborate salts, and imidazole compounds such as 2-methylimidazole. These may be used alone or as a mixture.

The long-chain fatty acid amide (E) used in the present invention is a reaction between a long-chain fatty acid such as stearic acid and sebacic acid and a compound having an amino group such as stearylamine, ethylenediamine and m-xylylenediamine. Product or a reaction product of a long-chain aliphatic amine such as stearyldiamine and a compound having a carboxyl group such as stearic acid or sebacic acid. Examples thereof include N-stearylstearic acid amide, ethylenebisstearic acid amide, N , N'-distearyl sebacic amide, m-
Xylylene bisstearylamide and the like. These long-chain fatty acid amides are known as release agents and are sometimes used in epoxy resin compositions for semiconductor encapsulation. But,
Unlike long-chain fatty acid esters such as carnauba wax or montanic acid ethylene glycol ester, long-chain fatty acids, metal salts of long-chain fatty acids, and polyolefin oxides, unlike long-chain fatty acid amides of the present invention, When used in a mixture of an epoxy resin and a polyfunctional non-crystalline epoxy resin, the compatibility between the long-chain fatty acid amide and the epoxy resin is good. Since a uniform resin mixture can be obtained by preventing crystallization, there is little decrease in curability, there is no generation of burrs and voids, and there is no variation in fluidity due to heating and kneading conditions. On the other hand, unlike other release agents, the long-chain fatty acid amide has a property that it is difficult to separate and precipitate from the mixture of the epoxy resin and the phenolic resin of the present invention, so that it has excellent mold release properties, and can be used in mold stains and molded products. Dirt on the surface of a certain semiconductor device hardly occurs. In addition, it is also possible to use together with other said release agents.

The resin composition of the present invention comprises, in addition to the components (A) to (E), a brominated epoxy resin, a flame retardant such as antimony trioxide, a low stress agent represented by a polysiloxane compound, if necessary, Coupling agents and coloring agents represented by carbon black can be appropriately compounded. . In order to obtain a molding material, after mixing all components, the mixture is heated and kneaded using a heating kneader or a hot roll, and then cooled and pulverized to obtain a desired resin composition. Using the resin composition of the present invention to encapsulate electronic components such as semiconductor elements and manufacture semiconductor devices, transfer molding, compression molding, and curing molding may be performed by conventional molding methods such as injection molding.

Hereinafter, the present invention will be described specifically with reference to examples. Example 1 An epoxy resin containing the formula (4) as a main component (melting point: 103 ° C.,
Epoxy equivalent 225) 2.9 parts by weight

Embedded image

Orthocresol novolak type epoxy resin (softening point 55 ° C., epoxy equivalent 200) 4.5 parts by weight Phenol novolak resin (softening point 75 ° C., hydroxyl equivalent 103) 3.6 parts by weight Spherical fused silica powder 88.0 Parts by weight triphenylphosphine 0.2 parts by weight ethylene bisstearic acid amide 0.3 parts by weight carnauba wax 0.2 parts by weight Carbon black 0.3 parts by weight After mixing using a mixer, the surface temperature was 9 parts by weight.
The mixture was kneaded 30 times using two rolls at 0 ° C. and 45 ° 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 1 shows the results.

Evaluation method Spiral flow: Using a mold for measuring spiral flow according to EMMI-I-66, using 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. Chip shift amount: 32-pin lead-on-chip structure TS
OP (package size is 10 × 21 mm, thickness 1.
0 mm, silicon chip size 9 × 18 mm, lead frame made of iron / nickel alloy (42 alloy), the chip and inner lead are adhered with 100 μm-thick polyimide tape), mold temperature of 175 ° C., 75 kg
Transfer molding was performed at a molding pressure of / cm ² for 2 minutes. The molded product was cut at the center of the package along the injection direction of the resin composition, and by observing the cross section, the distance from the lower surface of the package molded product at both ends of the chip was obtained, and the difference was displayed as a chip shift amount in μm. Burr amount: The length of the burr generated in the air vent portion during molding of the lead-on-chip structure TSOP in which the chip shift amount was measured was indicated in mm. Glass transition temperature (Tg): A test piece obtained by transfer molding at 175 ° C. for 2 minutes was further cured at 175 ° C. for 4 hours, and a thermomechanical analyzer [TMA manufactured by Seiko Electronics Co., Ltd.
-120, a heating rate of 5 ° C / min]. Heat strength: Flexural strength at 240 ° C. is determined according to JIS-K6911.
The test conditions were as follows. Solder resistance: 100-pin TQFP package (package size is 14 x 14 mm, thickness is 1.4 mm, silicon chip size is 8.0 x 8.0 mm, lead frame is 4
2 alloy) at a mold temperature of 175 ° C., 75 kg / cm ²
Transfer molding at an injection pressure of 2 minutes, and 175
Post-curing was performed at 8 ° C. for 8 hours. 85 molded product packages
It was left for 168 hours in an environment of 85 ° C. and a relative humidity of 85%, and then immersed in a solder bath at 240 ° C. for 10 seconds. The package was observed with a microscope, and external cracks ((number of packages in which cracks occurred) / (number of all packages) × 100) were displayed in%. In addition, the ratio of the peeling area between the chip and the resin composition was measured using an ultrasonic flaw detector, and the peeling rate ((peeling area) /
(Chip area) × 100) was expressed in%. Releasability: When molding a 100-pin TQFP evaluated for solder resistance, the releasability from the mold when the mold was opened was evaluated. ○ indicates good releasability, and × indicates occurrence of mold adhesion or runner breakage. Mold stain: The epoxy resin composition was continuously molded 100 times under the above conditions using a mold evaluated for mold release properties, and the surface of the mold after molding was visually observed. When the discoloration was recognized on the mold surface, it was indicated by x, and when there was no change, it was indicated by ○.

Examples 2 to 4 and Comparative Examples 1 to 4 Instead of the composition of Example 1, each component was blended in the ratio shown in Table 1, and mixed and kneaded in the same manner as in Example 1 to obtain a resin composition. Obtained. Table 1 shows the results of the evaluation performed in the same manner as in Example 1. The contents of the epoxy resins A to C used in Examples 2 to 4 and Comparative Examples 3 and 4 are shown below. Epoxy resin A is an epoxy resin obtained by epoxidizing a mixture of a stilbene-type phenol resin of the formula (5) and orthocresol novolak having a softening point of 70 ° C at a weight ratio of 1: 1 with epichlorohydrin by an ordinary method (epoxy equivalent 193) ).

Embedded image

Epoxy resin B is an epoxy resin obtained by epoxidizing a mixture of 4,4′-biphenol and orthocresol novolak having a softening point of 70 ° C. in a weight ratio of 2: 8 with epichlorohydrin by an ordinary method (epoxy equivalent: 190). ). Epoxy resin C is bisphenol F and formula (6)
Is an epoxy resin (epoxy equivalent: 260) obtained by epoxidizing a mixture having a weight ratio of 3: 7 with a phenol resin (softening point: 90 ° C.) by epichlorohydrin in a conventional manner.

Embedded image

[0025]

[Table 1]

[0026]

The resin composition of the present invention is excellent in curability at the time of molding, filling property and releasing property of a thin semiconductor device,
The sealed semiconductor device has excellent heat resistance, low moisture absorption, and excellent solder resistance after moisture absorption.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08L 63/00 C08L 63/00 C H01L 23/29 H01L 23/30 R 23/31 F-term (Reference) 4J002 CC032 CC082 CD051 CD061 CD071 DJ016 EP017 EP027 FB016 FD167 GQ05 4J036 AD04 AD05 AD08 AD09 AD10 AJ02 AJ14 DA04 FA05 FA12 FB08 JA07 4M109 EA06 EB03 EB04 EB06 EB07 EB08 EB09 EB13 EC05 EC05 EC03 EC05

Claims (2)

[Claims] (A) A non-polymer having a crystalline epoxy resin represented by the general formulas (1) to (3) in an amount of 10 to 60% by weight in the total epoxy resin and having an average of three or more epoxy groups in one molecule. Crystalline epoxy resin in total epoxy resin 40-90
Weight percent epoxy resin, (B) phenolic resin,
(C) fused silica powder, (D) curing accelerator, and (E)
An epoxy resin composition for encapsulating a semiconductor, comprising a long-chain fatty acid amide as an essential component. Embedded image Embedded image Embedded image (R in the formula (3) is a group selected from a hydrogen atom, a halogen atom or an alkyl group having 1 to 9 carbon atoms, and may be the same or different from each other.) 2. A semiconductor device comprising a semiconductor element encapsulated with the epoxy resin composition for semiconductor encapsulation according to claim 1.