JPH06200121A - Low-pressure transfer molding material for sealing semiconductor - Google Patents

Abstract

PURPOSE:To obtain the subject molding material, consisting essentially of a specific epoxy, a curing agent, a curing accelerator and a filler, having low hygroscopicity and excellent in solder heat resistance and moldability and useful as electronic equipment, etc. CONSTITUTION:The objective molding material consists essentially of (A) a mixture of an epoxy containing a diphenyl ether skeleton of the formula (R1 to R8 are H, alkyl or halogen) in all or a part thereof with an epoxy which is glycidyl ether of naphthols having at least one naphthalene skeleton and hydroxyl group bound to the at least one naphthalene skeleton in the molecule (e.g. 4,4'-dihydroxybiphenyl ether), (B) a curing agent (e.g. phenol), (C) a curing accelerator (e.g. tributylamine) and (D) a filler (e.g. crushed silica).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention can reduce the thermal shock due to soldering that an epoxy-sealed semiconductor device used for electronic equipment receives during surface mounting on a circuit board, and can provide excellent reliability. The present invention relates to a possible low-pressure transfer molding material for semiconductor encapsulation having excellent moldability.

[0002]

2. Description of the Related Art Conventionally, in the use of encapsulating electronic parts such as coils, capacitors, transistors, ICs, etc., epoxy resin has been used because it satisfies the requirements of material properties such as mechanical strength and is excellent in productivity. Low-pressure transfer molding with a molding material is widely performed. This epoxy molding material contains epoxy, a curing agent, a curing accelerator, and a filler as main components, and in addition to a colorant, a flame retardant, a release agent, a coupling agent, etc.
It contains various additives to improve stress characteristics, moisture resistance, adhesion, etc.

In this application, phenol curable epoxy is used as a resin component from the viewpoint of curability, heat resistance and moisture resistance. The main epoxy widely used is glycidyl ether of orthocresol novolac, and recently, epoxy having a biphenyl skeleton or a naphthalene skeleton has been partially used.

As the curing agent, those having a phenolic OH group are widely used. Phenol novolac is the most common, and those having naphthol and the like in the molecule and terpene skeletons for various modification applications, Those having a dicyclopentadiene skeleton have been proposed.

On the other hand, it has been studied to improve the mechanical strength and the hygroscopicity by highly filling the filler. Techniques that have been studied so far for increasing the filling amount of the filler include a technique that uses a bifunctional low-viscosity epoxy having a biphenyl skeleton, and an epoxy that has a rigid naphthalene skeleton to keep the glass transition temperature high. There are technologies, etc. The amount of filler added is such that the mechanical strength of the molding material is sufficiently exerted, and
Although they are mixed within a range that does not impair the moldability, 70 to 80% of the total composition is mixed in the conventional technique.

Epoxy having a naphthalene skeleton has a drawback that it has a high viscosity. Therefore, a technique using a bifunctional low-viscosity epoxy having a biphenyl skeleton, a technique using spherical silica as the main component of the filler, and a particle size distribution of the filler Higher filling of the filler has been attempted by using a technique for optimizing the above. However, using any of the techniques, there was no example in which high filling of 85% by weight or more of the entire composition could be achieved while maintaining excellent moldability.

[0007]

In recent years, the miniaturization of electronic equipment has been rapidly reduced, and the mounting of electronic components on a circuit board is rapidly shifting from the conventional insertion method to the surface mounting method. In the surface mounting method, since the electronic component body is mounted on the solder mounting surface, 200 ° C. or higher in both soldering methods of flow soldering and reflow soldering.
The electronic component body is exposed to a very high temperature of up to about 260 ° C.

Particularly in an epoxy-sealed semiconductor device, due to this thermal shock, moisture absorbed in the resin cured product of the package expands rapidly in the device, causing cracks and interfacial delamination, resulting in reliability. There is a serious problem of worsening the so-called solder heat resistance.

In order to solve such a problem, the present invention provides
The present invention aims to provide a low-pressure transfer molding material for semiconductor encapsulation, which is made of a material and has a low hygroscopicity and therefore has good solder heat resistance and excellent moldability.

[0010]

Means for Solving the Problems The present inventors have found that an epoxy containing an ultra-low viscosity diphenyl ether skeleton and a glycidyl ether of a naphthol or a derivative thereof having both heat resistance (high glass transition temperature) and low hygroscopicity. It was found that the moisture absorption of the epoxy-sealed semiconductor device can be suppressed to a minimum and the heat resistance of the solder can be improved by using the epoxy together, and the invention has been completed. In particular, when the epoxy of the present invention is used, in a low-pressure transfer molding material for semiconductor encapsulation containing a heat-resistant naphthalene skeleton, the increase in viscosity is suppressed to 500 poises or less,
It has been clarified that it is possible to achieve a high loading of fused silica of 85% by weight or more, and the maximum effect can be expected.

That is, the present invention provides (a) an epoxy,
The curing agent (b), the curing accelerator (c), and the filler (d) are essential components, and (a) the epoxy is wholly or partly represented by the following formula (1).

[Chemical 4] A mixture of an epoxy having a diphenyl ether skeleton represented by and an epoxy which is a glycidyl ether of a naphthol having a hydroxyl group bonded to at least one naphthalene skeleton and at least one naphthalene skeleton in a molecule. It is a low-voltage transfer molding material for semiconductor encapsulation.

The present invention will be described in detail below. The (a) epoxy used in the present invention has the following formula (1)

[Chemical 5] Represented by the following, an epoxy containing a diphenyl ether skeleton, and an epoxy which is a glycidyl ether of a naphthol having a hydroxyl group bonded to at least one naphthalene skeleton and at least one naphthalene skeleton in a molecule,
It is most preferable to mix it as an essential component and use it in an amount corresponding to 70% or more of the total amount of epoxy in order to exert the effect of the present invention.

As the epoxy resin represented by the above formula (1), 4,4'-dihydroxybiphenyl ether,
4,4'-dihydroxy-3,3'-dimethylbiphenyl ether, 4,4'-dihydroxy-3,3 ', 5
Examples thereof include diglycidyl ethers of 5'-tetramethylbiphenyl ether.

Further, as an epoxy which is a glycidyl ether of a naphthol having a naphthalene skeleton and a hydroxyl group bonded to at least one naphthalene skeleton,
There are glycidyl ethers such as 1-naphthol, 2-naphthol, 1,5-naphthol, 1,6-naphthol, 2,6-naphthol, bisnaphthol, and naphthol novolak, and the following formula (3) is preferable.

[Chemical 6] It is a glycidyl ether having a random co-condensation structure represented by. Such a random co-condensation structure can be easily obtained by random co-condensation of naphthol with dimethylolphenol, p-xylylene glycol or the like.

As the other epoxy that can be used in combination with the above-mentioned essential epoxy, any epoxy can be used as long as it has an epoxy group in one molecule, for example, bisphenol A type epoxy, bisphenol F type epoxy,
Biphenyl type epoxy, phenol, cresol,
A resin obtained by singly or co-condensing bisphenol A or the like with aldehydes, xylene glycols or the like under an acidic catalyst as a raw material, and epoxidized by glycidyl etherification with epichlorohydrin is used. Further, for the purpose of imparting flame retardancy, it is possible to include the above-mentioned bromide of epoxy in a part of the epoxy.

As the curing agent (b) used in the present invention, those having a phenolic OH group can be widely used, and in addition, acid anhydrides, amines, thiols and the like can also be used. In the phenol curing type, for example, phenol, cresol, bisphenol A, naphthol, etc. and aldehydes, xylene glycols, etc. under acidic catalyst are used alone or in cocondensation, terpene diphenol, dicyclohexyl of phenols, etc. A pentadiene condensate or its derivative is used. The compounding amount of the curing agent with respect to epoxy is 0.5 with respect to 1 epoxy equivalent.
Approximately 1.2 equivalents are desirable, and otherwise, serious defects may occur in moldability.

Examples of the (c) curing accelerator used in the present invention include amines such as tributylamine, 1,8-siazabicyclo (5,4,0) undecene-7, triphenylphosphine and tetraphenylphosphonium tetra. Phosphines such as phenylborate and imidazoles such as 2-methylimidazole and 2-phenyl-4-methylimidazole are used.

As the filler (d) used in the present invention, crushed or spherical silica powder is used in an amount of 90% of the total amount of the filler.
It is preferable to use at least wt%. The crushed silica may be crushed by a ball mill or the like, or may be crushed by a grinding method. As the spherical silica, it is possible to use, in addition to those processed into a spherical shape by the thermal spraying method, those in which silica metal is made into fine powder spherical silica by a direct oxidation method. As a filler other than fused silica, inorganic powder such as alumina, silicon nitride, aluminum nitride, etc. can be used, and as a flame retardant aid, antimony trioxide can be used as a part of the filler. . A larger content of the filler is more effective for improving heat resistance, but if it is too large, moldability may be impaired.

Further, the transfer molding material of the present invention contains various kinds of colorants, flame retardants, release agents, coupling agents, etc., if necessary, as well as various kinds for improving stress characteristics, moisture resistance, adhesion and the like. Additives can be used.

As the colorant, for example, carbon black, acetylene black, red iron oxide and the like can be used.

As the flame retardant, the above-mentioned brominated epoxy,
In addition to antimony trioxide, hexabromobenzene or the like can be used.

As the release agent, natural waxes such as carnauba, synthetic waxes such as higher fatty acid esters, modified silicone oils and the like can be used.

As the coupling agent, a silane coupling agent such as epoxysilane, aminosilane, ureidosilane, mercaptosilane, or a titanate coupling agent can be used.

As the stress reducing agent, solid or liquid silicone rubber, silicone oil, synthetic rubber (polybutadiene, polyisoprene, etc.), thermoplastic elastomer (SB) can be used.
S, SIS, SEBS, SEPS, etc.) and their derivatives are used. As the moisture resistance improver, ion exchangers such as hydrotalcites are used.

As the adhesion improver, liquid polybutadiene, tackifiers such as petroleum resin, rosin and terpene are used.

These additives are also calculated as the weight of the entire composition, and the inorganic components in the additives are calculated as fillers. In the present invention, it is most preferable that the total amount of these fillers is 85% by weight or more in the entire composition in order to maximize the effect of heat resistance. Also 1 of this formulation
The minimum melt viscosity at 75 ° C. is most preferably 500 poise or less in order to maintain good moldability.

[0027]

[Function] The root cause of cracking due to moisture absorption is
The resin component absorbs moisture in the air, and the moisture expands rapidly during solder mounting, causing package cracks. Due to such a mechanism, reliability deterioration occurs at the time of solder mounting, so a fundamental measure against solder heat resistance is to reduce the moisture absorption of the epoxy molding material. Also, in order to ensure sufficient reliability, the operating temperature of the semiconductor (up to 150
It is necessary to exhibit sufficient heat resistance in the temperature range of about ° C), and it is necessary to keep the glass transition temperature of the molded product sufficiently high.

According to the present invention, an epoxy containing an ultra-low viscosity diphenyl ether skeleton and an epoxy which is a glycidyl ether of a naphthol having both heat resistance (high glass transition temperature) and low hygroscopicity are used in combination. , It has become possible to suppress the moisture absorption of the epoxy-sealed semiconductor device to a minimum while maintaining the high glass transition temperature and improve the solder heat resistance.

Further, when the filler is highly filled by using the conventionally used resin, it is unavoidable that the viscosity is increased at the time of low pressure transfer molding, and unfilled, gold wire deformation, island deformation, It was not possible to secure molding quality due to the occurrence of voids and the like.

In the present invention, as a method of suppressing an increase in melt viscosity, the viscosity is extremely low because the molecular weight is very low and a bending structure called an ether group is contained in the molecule. An inventor has invented a method of using an epoxy having a diphenyl ether skeleton represented by the formula (1), which has a high melting point due to a polar structure, is solid at room temperature, and can be used as an epoxy for a low-pressure transfer molding material. In the present invention, it is possible to suppress the melt viscosity in the low pressure transfer molding temperature range of 175 ° C. to 500 poises or less even if the filling is increased to 85% by weight or more, and the molding quality of these can be secured.

[0031]

EXAMPLES The present invention will be described below with reference to examples, but the scope of the present invention is not limited to these examples. The main epoxies used in the examples are as follows. Epoxy A: diphenyl ether diglycidyl ether (epoxy equivalent 175 g / eq, melting point 84 ° C., 150 ° C.
Viscosity 4 cst) Standard structural formula

[Chemical 7] Epoxy B: Epoxidized naphthol paraxylene glycol condensate (epoxy equivalent: 280 g / eq, melting point 85)
℃, 150 ℃ viscosity 3.6 poise) Standard structural formula

[Chemical 8] Epoxy C: Epoxidized naphthalene diol para-xylene glycol condensate (epoxy equivalent 170 g / eq, melting point 64 ° C, 150 ° C viscosity 2.0 poise) Standard structural formula

[Chemical 9] Epoxy D: EOCN-7000-90 (manufactured by Nippon Kayaku Co., epoxy equivalent 235 g / eq, melting point 93 ° C., 150
℃ viscosity 10.8 poise) Standard structural formula

[Chemical 10] Epoxy E: YX-4000H (Okaka Shell Epoxy Co., Ltd., epoxy equivalent 190g / eq, melting point 105 ° C, 1
50 ° C viscosity 12 cst) Standard structural formula

[Chemical 11]

The method for preparing the low-pressure transfer molding materials used in Examples and Comparative Examples will be described below. The amounts used in the examples and comparative examples are all parts by weight. According to the formulations shown in Tables 1, 2, and 3, spherical fused silica (manufactured by Denki Kagaku Kogyo,
3 parts of a silane coupling agent (manufactured by Nippon Unicar Co., Ltd., A-186) was added to 10 parts of FB-48) shown in the table and 10 parts of antimony trioxide powder (manufactured by Sumitomo Metal Mining Co., Ltd.) and mixed with a mixer. Further, the number of parts of the epoxies A to E shown in the table, brominated epoxy (manufactured by Dainippon Ink and Chemicals, Epicron-
152S) 10 parts, phenol novolak (manufactured by Gunei Chemical Co., Ltd., PSM-4261) in the number of parts shown in the table, and curing accelerator triphenylphosphine (manufactured by KAISEI CORPORATION, PP
-360) in the table, 3 parts of carbon black (MA-600 manufactured by Mitsubishi Kasei Co., Ltd.) as a colorant, and 4 parts of release agent (Hoechst OP / Hoechst S = 1/1 manufactured by Hoechst) are added. After mixing, the mixture was kneaded with a kneader to obtain low-pressure transfer molding materials of Examples and Comparative Examples.

Examples 1 to 6 In Examples 1 to 6 shown in Table 1, epoxy B is used as the epoxy which is a glycidyl ether of naphthols. In Examples 1 to 3, the epoxy A and B were used in different proportions. In Examples 4 to 6, spherical fused silica was blended so that the amount of the filler in all compositions was 85% by weight or more. Also in the formulations of Examples 4 to 6, the melt viscosity was 500 poise or less due to the use of Epoxy A. As can be seen from the evaluation results in Table 1, Examples 1 to 6 have low water absorption, excellent solder heat resistance, and low viscosity, so that they have high fluidity and excellent moldability.

Comparative Examples 1 to 5 In Comparative Examples 1 and 2, since the epoxy which is a glycidyl ether of naphthol is not used, the glass transition temperature is low, the water absorption is relatively high, and the solder heat resistance is poor. In Comparative Example 3, since the epoxy A was not used, the melt viscosity was 500 poise or more, and the moldability was poor. Comparative Examples 4 and 5
Then, the spherical fused silica was blended so that the amount of the filler in the entire composition was 85% by weight or more, but the melt viscosity was 500 poise or more, and the moldability was poor.

[0035]

[Table 1]

Examples 7 to 12 In Examples 7 to 12 shown in Table 2, Epoxy C is used as the epoxy which is a glycidyl ether of naphthols. In Examples 7 to 9, the epoxy A and C were used in different proportions. In Examples 10 to 12, spherical fused silica was blended so that the amount of the filler in all compositions was 85% by weight or more. Also in the formulations of Examples 10 to 12, the melt viscosity was 500 poise or less due to the use of Epoxy A. As can be seen from the evaluation results in Table 2, Examples 7 to 12
It can be seen that is low in water absorption, excellent in heat resistance of solder, and low in viscosity, so that it has high fluidity and excellent moldability.

Comparative Examples 6 to 8 In Comparative Example 6, since no epoxy A was used, the melt viscosity was 500 poise or more, and the moldability was poor. In Comparative Examples 7 and 8, spherical fused silica was blended so that the amount of the filler in the entire composition was 85% by weight or more, but the melt viscosity was 5
It is more than 00 poise and is inferior in moldability.

[0038]

[Table 2]

Examples 13-18 In Examples 13-18 shown in Table 3, Epoxy D is used as the epoxy which is a glycidyl ether of naphthols. In Examples 13 to 15, the epoxy A and D were used in different proportions. In Examples 16 to 18, spherical fused silica was blended so that the amount of the filler in all compositions was 85% by weight or more. Also in the formulations of Examples 16 to 18, the melt viscosity was 500 poise or less due to the use of Epoxy A. As can be seen from the evaluation results in Table 3, Example 13 to
It can be seen that No. 18 has low water absorption, excellent solder heat resistance, low viscosity, high fluidity, and excellent moldability.

Comparative Examples 9 to 11 In Comparative Example 9, since epoxy A was not used, the melt viscosity was 500 poises or more, and the moldability was poor. Comparative Example 1
In Nos. 0 and 11, spherical fused silica was blended so that the amount of the filler in the entire composition was 85% by weight or more, but the melt viscosity was 500 poises or more, and the moldability was poor.

[0041]

[Table 3]

Evaluation Method Melt Viscosity: The minimum viscosity when flowing in a molten state at 175 ° C. in a circular tube having a diameter of 1.0 mmφ and a length of 10 mm was measured using a Koka type flow tester. Fluidity: 17 using a mold for spiral flow measurement according to EMMI-I-66 with a low pressure transfer molding machine
The length of the molded product when molded was determined under the conditions of 5 ° C., 70 kg / mm ² , and 120 seconds. Glass transition temperature: 175 on low pressure transfer molding machine
° C., under the conditions of 70 kg / mm ^2, 120 seconds, 10 to length and formed into 20mm cylindrical, linear expansion behavior of those 12 hours post-cured at 175 ° C., as measured by the TMA method, the inflection point of the curve It was calculated from the temperature. Water absorption: tableting the obtained molding material, and using a low-pressure transfer molding machine, 175 ° C., 70 kg / mm ² , 1
Under a condition of 20 seconds, a disk having a diameter of 50 mmφ × 3 mm was formed, and post-cured at 175 ° C. for 12 hours.
The sample was allowed to stand for 100 hours in an environment of 85 ° C RH and the water absorption was measured. Moldability: The obtained molding material is made into tablets, which are then subjected to a low pressure transfer molding machine at 175 ° C., 70 kg / mm ² , 1
14 × 20 × 2.2 mm QFP-8 under the condition of 20 seconds
0 x 7 x 7 x 0.4 mm aluminum wiring simulation element (TE
G) was sealed. The unfilled portion was visually inspected for gold wire deformation, island deformation, and voids using a soft X-ray fluoroscope, and if any defect occurred, it was determined to be a defective package. Solder cracking property: same Q as used in the formability test of the previous section
Post cure FP-80 at 175 ° C for 12 hours,
After absorbing moisture for 100 hours in an environment of 5 ° C and 85% RH, 26
The cracks generated when immersed in a solder bath at 0 ° C. for 10 seconds were visually inspected to determine defects. Moisture resistance after soldering: same QF as used in the former formability test
Post cure P-80 at 175 ° C for 12 hours,
After absorbing moisture for 24 hours in an environment of ℃ 85% RH, 260 ℃
Immerse in the solder bath for 10 seconds and then at 121 ℃ 100% R
Using a tester, the open circuit that occurred when left in an H environment for 300 hours was inspected and a defect was determined.

[0043]

According to the present invention, it is possible to obtain a low-voltage transfer molding material for semiconductor encapsulation, which has not been obtained by the prior art and has low water absorption, excellent solder heat resistance, and excellent moldability. When the low-voltage transfer molding material for semiconductor encapsulation of the present invention is used for encapsulating a semiconductor device, it is used for a semiconductor device that requires high reliability, particularly a highly integrated large IC mounted in a surface mount type package. In this case, the epoxy-encapsulated semiconductor device used in electronic equipment reduces the thermal shock due to soldering when it is surface-mounted on a circuit board,
It becomes possible to give excellent reliability.

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Claims (4)

[Claims] 1. (a) Epoxy, (b) Hardener, (c)
A curing accelerator and a filler (d) are essential components, and all or part of the epoxy (a) is represented by the following formula (1): A mixture of an epoxy having a diphenyl ether skeleton represented by and an epoxy which is a glycidyl ether of a naphthol having a hydroxyl group bonded to at least one naphthalene skeleton and at least one naphthalene skeleton in a molecule. Low-voltage transfer molding material for semiconductor encapsulation. 2. An epoxy having a diphenyl ether skeleton is represented by the following formula (2): The low-pressure transfer molding material for semiconductor encapsulation according to claim 1, which is a diphenyl ether diglycidyl ether represented by: 3. An epoxy which is a glycidyl ether of a naphthol is represented by the following formula (3): The low-pressure transfer molding material for semiconductor encapsulation according to claim 1, which is a glycidyl ether having a random co-condensation structure represented by: 4. (d) The main component in the filler is fused silica, the amount of the filler in the entire composition is 85% by weight or more, and the minimum melt viscosity at 175 ° C. is 500 poises or less. Item 1. A low-pressure transfer molding material for semiconductor encapsulation according to Item 1.