JP2991847B2 - Resin composition for semiconductor encapsulation - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin composition for encapsulating a semiconductor having excellent resistance to soldering stress and moisture.

[0002]

2. Description of the Related Art Conventionally, electronic components such as diodes, transistors, and integrated circuits are sealed with a thermosetting resin. In particular, in an integrated circuit, ortho-cresol novolak epoxy resin having excellent heat resistance and moisture resistance is made of a novolak type. An epoxy resin composition cured with a phenol resin is used.

In recent years, in the market trend of miniaturization, weight reduction and high performance of electronic equipment, high integration of semiconductors is progressing year by year, while surface mounting in packages is becoming mainstream. As chips become larger and surface mounted, packages tend to be smaller and thinner. In particular, the thickness of the package is remarkably reduced, and the T
Practical use of SOP and TQFP is being continued. As described above, the semiconductor mounting method is changed from the conventional insertion type to the surface mounting type (VP).
S reflow type, IR reflow type, solder immersion method, etc.).
Exposure to the above-mentioned high temperatures causes a phenomenon such as cracking of the package or separation of the interface between the chip and the sealing resin, which causes a problem that the moisture resistance is deteriorated and the reliability is lowered. Therefore, development of a highly reliable resin excellent in crack resistance and moisture resistance even under severe conditions such as solder immersion is urgently required.

In order to solve these problems, addition of thermoplastic oligomers (Japanese Patent Application Laid-Open No. 62-15849) and addition of various silicone compounds (Japanese Patent Application Laid-Open No. 115850, 62-
116654, 62-128162) and silicone modification (Japanese Patent Application Laid-Open No. 62-136860), all of which have cracks in the package during solder immersion and have excellent reliability. It has not been possible to obtain an epoxy resin composition for semiconductor encapsulation.

On the other hand, in order to obtain an epoxy resin composition for semiconductor encapsulation having excellent resistance to soldering stress during solder immersion, a biphenyl type epoxy resin is used as a resin system (Japanese Patent Laid-Open No.
No. 4-65116) has been studied, but the use of a biphenyl type epoxy improves the adhesion to a lead frame and low water absorption, and reduces the occurrence of cracks. The transition temperature is
There is a drawback that it is lower than that of a conventional epoxy resin represented by orthocresol novolak type epoxy, and the long-term heat resistance is poor.

[0006]

An object of the present invention is to provide a resin composition for semiconductor encapsulation which is remarkably excellent in solder crack resistance, moisture resistance and heat resistance against such problems.

[0007]

Means for Solving the Problems The present inventors have intensively studied to solve these problems and found a resin composition having the following composition. That is, the present invention provides (A) an epoxy resin containing 50 to 100% by weight, based on the total epoxy resin amount, of a cocondensed novolak epoxy resin of orthocresol and β-naphthol represented by the formula (1),

[0008]

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(N = 1 to 15) (B) a phenolic resin curing agent containing a polyfunctional phenolic resin represented by the formula (2) in an amount of 50 to 100% by weight based on the total amount of the phenolic resin;

[0010]

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(N = 1 to 15) A resin composition for encapsulating a semiconductor comprising (C) an inorganic filler and (D) a curing accelerator as essential components.

The co-condensed novolak epoxy resin of ortho-cresol and β-naphthol used in the present invention is an epoxy resin of a novolak resin obtained by co-condensing ortho-cresol and β-naphthol from formaldehyde. % By weight, and the formula (1)
Is a compound mainly having the structure of n is 1 to 15, 15
If it exceeds, the fluidity is inferior and the moldability decreases.

The epoxy resin of the formula (1) has the characteristics of excellent low water absorption, low coefficient of linear expansion of the resin, excellent releasability during molding, and excellent resistance to solder cracking during solder immersion. Shows the results. The amount of the ortho-cresol and β-naphthol co-condensed novolak epoxy resin can be adjusted so as to maximize the solder crack resistance. In order to obtain the effect of solder crack resistance, it is desirable to use ortho-cresol and β-naphthol co-condensation Novoc epoxy resin in an amount of 50% by weight or more, preferably 70% by weight or more of the total epoxy resin amount. If the content is less than 50% by weight, low water absorption and low linear expansion coefficient cannot be sufficiently obtained, and solder crack resistance is insufficient.

When an epoxy resin other than ortho-cresol and β-naphthol co-condensed novolak epoxy resin is used in combination, the epoxy resin used refers to all polymers having an epoxy group. For example, trifunctional epoxy resins such as bisphenol type epoxy resin, cresol novolak type epoxy resin, biphenyl type epoxy resin, phenol novolak type epoxy resin, triphenolmethane type epoxy resin, alkyl-modified triphenolmethane type epoxy resin, and epoxy resin containing triazine nucleus And so on.

The polyfunctional phenol resin curing agent having the structure represented by the formula (2) is a phenol resin curing agent having three or more hydroxyl groups in one molecule. n is 1 to 15, and when it exceeds 15, the fluidity is poor and the moldability is reduced. The feature is that the crosslink density of the cured product with the epoxy resin is improved, and the glass transition temperature is improved. Therefore, it is suitable not only for solder crack resistance during solder immersion for recent surface mounting, but also for long-term heat resistance of semiconductor components.

By controlling the amount of the polyfunctional phenol resin curing agent used, the solder crack resistance can be maximized. In order to obtain the effect of solder crack resistance, it is desirable to use the trifunctional phenolic resin curing agent represented by the formula (2) in an amount of 50% by weight or more, preferably 70% by weight or more of the total amount of the phenolic resin curing agent. 50% by weight
If it is less than 3, the crosslink density does not increase and the solder crack resistance is insufficient.

When other phenolic resin curing agents are used in addition to the polyfunctional phenolic resin curing agent represented by the formula (2), the phenolic resin curing agent used refers to all compounds having a phenolic hydroxyl group. For example, bisphenol A, bisphenol F, phenol novolak resin,
A cresol novolak resin, a dicyclopentadiene-modified phenol resin, a cocondensate of a dicyclopentadiene-modified phenol resin with phenol novolak and a cresol novolak resin, a para-xylene-modified phenol resin, and the like can be used. These may be used alone or in combination of two or more. Alternatively, a polyfunctional phenol resin represented by the formula (2) and another phenol resin curing agent may be melt-mixed in advance. These phenolic resins used in combination are appropriately used for the purpose of adjusting curability, imparting flexibility and the like, but for adjusting fluidity, low molecular weight compounds such as bisphenol F are preferable.

Examples of the inorganic filler used in the present invention include fused silica powder, crystalline silica powder, alumina powder, hydrated alumina powder, silicon nitride powder, calcium carbonate powder and the like, and particularly preferred is fused silica powder. The amount of the inorganic filler is preferably 70 to 90% by weight in the total resin composition in view of the balance between solder stress resistance and moldability.

The curing accelerator used in the present invention may be any one which promotes the reaction between the epoxy resin and the phenolic hydroxyl group, and those generally used as sealing materials can be widely used. For example, organic phosphine compounds such as triphenylphosphine (TPP), tributylphosphine and tri (4-methylphenyl) phosphine, tributylamine, triethylamine, dimethylbenzylamine (BDMA), trisdimethylaminomethylphenol, and diazabicycloundecene (DBU) ) And imidazole compounds such as 2-methylimidazole, 2-phenylimidazole and 2-ethyl-4-methylimidazole. These can be used alone or 2
It is used by mixing more than one kind.

The epoxy resin composition for encapsulation of the present invention comprises an epoxy resin, a curing agent, an inorganic filler and a curing accelerator as essential components. In addition to this, a silane coupling agent, a brominated epoxy resin may be used if necessary. Various additives such as flame retardants such as antimony trioxide and hexabromobenzene, coloring agents such as carbon black and red iron oxide, release agents such as natural wax and synthetic wax, and low stress additives such as silicone oil and rubber. It may be properly compounded.

In order to produce the encapsulating epoxy resin composition of the present invention as a molding material, an epoxy resin, a curing agent,
After the filler, the curing accelerator, and other additives are sufficiently and uniformly mixed by a mixer or the like, the mixture is further melt-mixed with a hot roll or a kneader or the like, cooled, and pulverized to obtain a molding material. These molding materials can be applied to sealing, coating, insulating and the like of electronic parts or electric parts.

[0022]

EXAMPLES The present invention will be specifically described below with reference to examples. The mixing ratio is by weight. Examples 1-4, Comparative Examples 1-3 (A) Epoxy resin Orthocresol and β-naphthol co-condensed novolak epoxy resin represented by formula (1) (epoxy equivalent 23
3, softening point 87 ° C) Orthocresol novolak type epoxy resin (epoxy equivalent 200, softening point 65 ° C) Biphenyl type epoxy resin: 3,3 ′, 5,5′-tetramethyl-4,4′-dihydroxybiphenylglycidyl ether (B) Phenolic resin curing agent Polyfunctional phenol resin represented by formula (3) (hydroxyl equivalent 107, softening point 129 ° C)

[0023]

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Bisphenol F (hydroxyl equivalent 10
0) Phenol novolak resin (hydroxyl equivalent 104, softening point 95 ° C.) (C) Inorganic filler Fused silica (Average particle diameter 14 μm) (D) Hardening accelerator Triphenylphosphine (E) Other additives Carbon black Carnauba wax Mix at each temperature shown in Table 1 with a mixer at room temperature, knead with a biaxial roll at 70 to 100 ° C, cool and pulverize to obtain a molding material, and make it into a tablet to form an epoxy resin composition for semiconductor encapsulation. I got This composition was transferred to a low-pressure transfer molding machine (molding conditions: 175 ° C., 70 kg / cm
² , 120 seconds), and the obtained molded product is
Post-curing was performed at 5 ° C. for 8 hours and evaluated. Table 1 shows the results.

Evaluation method * 1 Spiral flow Using a mold for measuring spiral flow according to EMMI-I-66, mold temperature 175 ° C, injection pressure 70 kg / cm ² ,
The cure time was measured at 2 minutes. * 2 Solder cracking test A molded product (chip size: 36 mm ² , package thickness: 2.05 mm) was treated for 72 hours at 85 ° C. and 85% RH water vapor for 20 pieces, and then passed through a VPS-type soldering machine.
The temperature was maintained at 90 ° C. for 90 seconds, and the presence or absence of external cracks was observed. For 20 molded products (chip size: 36 mm ² , package thickness: 2.05 mm), after 72 hours of treatment at 85 ° C. and 85% RH water vapor at 240 ° C. for 10 seconds in an infrared reflow soldering machine, presence or absence of external cracks Was observed. * 3 Solder moisture resistance test A 16pSOP package on which a simulated element was mounted was molded and hardened, treated for 72 hours in an environment of 85 ° C and 85% RH, and then immersed in a solder bath at 260 ° C for 10 seconds. 100% RH), and the number of open defects of the circuit was measured. * 4 Heat resistance Thermal expansion characteristics were measured on a test piece molded at 175 ° C. for 2 minutes and cured at 175 ° C. for 8 hours to determine the glass transition temperature of the cured product.

[0026]

[Table 1]

[0027]

Industrial Applicability The resin composition for encapsulating a semiconductor of the present invention has extremely high industrial value as a resin composition for surface mounting encapsulation due to its remarkably excellent solder cracking property, moisture resistance and heat resistance.

Claims (2)

(57) [Claims] (A) An epoxy resin, a co-condensed novolak epoxy resin of ortho-cresol and β-naphthol represented by the formula (1) is used in an amount of 50 to 50% based on the total epoxy resin amount.
Epoxy resin containing 100% by weight (N = 1 to 15) (B) a phenolic resin curing agent containing 50 to 100% by weight of a polyfunctional phenolic resin represented by the formula (2) based on the total phenolic resin amount as a phenolic resin curing agent; (N = 1 to 15) A resin composition for semiconductor encapsulation containing (C) an inorganic filler and (D) a curing accelerator as essential components. 2. A phenol resin curing agent of the formula (2)
2. The resin composition for semiconductor encapsulation according to claim 1, wherein the polyfunctional phenol resin curing agent is used in combination with bisphenol F.