JP3230772B2 - 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. Epoxy resin compositions cured with phenolic resins have been used.
However, with the recent trend in the market for smaller, lighter, and higher-performance electronic devices, the integration of semiconductors is increasing year by year, and small and thin surface-mount packages are becoming mainstream in packages. With the increase in size of chips accompanying the demand, requirements for sealing resins have become increasingly severe, and it has become difficult to ensure reliability with conventional resin compositions.
This is because the semiconductor mounting method is changed from a conventional pin insertion type to a surface mounting type (VPS reflow type, IR reflow type, solder immersion method, etc.), so that the semiconductor immersion process is rapidly exposed to a high temperature of 200 ° C. or more. This causes problems such as cracking of the package and peeling of the interface between the chip and the sealing resin, deteriorating moisture resistance and lowering reliability, and further increasing the effect on small and thin packages. . Under such circumstances, development of a highly reliable resin having excellent 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 Laid-Open No. 62-15849) and addition of various silicone compounds (Japanese Patent Laid-Open No. 62-15849) have been proposed for the purpose of reducing thermal shock during soldering. No. 11585, 62-
116654, 62-128162), and silicone modification (Japanese Patent Application Laid-Open No. 62-136860). However, cracks are generated in the package during solder immersion, resulting in excellent reliability. It was not possible to obtain a resin composition for semiconductor encapsulation. on the other hand,
In order to obtain a resin composition for semiconductor encapsulation having excellent resistance to solder cracking during solder immersion, use of a phenol aralkyl resin represented by the formula (3) as a curing agent has been studied.

[0004]

Embedded image

The use of this resin improves the adhesion to the lead frame and low water absorption, and reduces the occurrence of cracks. However, the glass transition temperature of the cured product is significantly lower than that of a conventional phenol novolak curing agent system. There is a disadvantage that 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 inventor has made intensive studies to solve these problems, and has found the following resin compositions. That is, the present invention provides (A) a biphenyl type epoxy represented by the formula (1) in an amount of 3
A resin containing 0 to 100% by weight,

[0008]

Embedded image (Where R ₁ , R ₂ , R ₃ , R ₄ are hydrogen or CH ₃ and are the same or different atoms or groups)

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

[0010]

Embedded image (Where X is para-xylylene, n = 1 to 8)

(C) an inorganic filler as an essential component;
The resin composition for semiconductor encapsulation wherein the inorganic filler is 70 to 90% by weight of the total composition.

The biphenyl type epoxy of the formula (1) used in the present invention can incorporate a large amount of an inorganic filler without impairing fluidity due to the low melt viscosity of the epoxy itself.
In addition, it has high strength and high toughness, and is characterized by low moisture absorption and excellent resistance to solder stress. By adjusting the amount of use of the formula (1), the effect can be maximized. That is, the amount used is preferably 30 to 100% by weight, preferably 50% by weight or more based on the total amount of the epoxy resin. If it is less than 30% by weight, it is difficult to reduce the viscosity of the resin, and it is difficult to mix a large amount of the intended inorganic filler,
High strength, high toughness and low hygroscopic properties cannot be exhibited. Further, in formula (1), R ₁ , R ₂ , R ₃ and R ₄ are preferably CH ₃ .
Other epoxy resins used in combination are bisphenol type,
Various types such as phenol novolak type, orthocresol novolak type, trisphenylmethane type and naphthalene skeleton-containing type can be applied, and they may be used alone or in combination.

The phenol resin curing agent having the structure represented by the formula (2) has the following two features. First
The point is that it has valaxylylene represented by X in the molecular chain, and has an effect of being superior in moisture resistance and excellent in flexibility when heated as compared with a conventional phenol novolak resin. When paraxylylene having such a flexible structure is incorporated into the molecule, the reactivity is lowered, and the crosslink density of the cured product is lowered, so that the glass transition temperature is lowered. Therefore, the second point is that bisphenols are introduced instead of phenol mononuclear to introduce a large amount of phenolic hydroxyl groups into the molecular side chain, thereby improving the reactivity and the glass transition temperature. There is. The value of n in Expression (2) is 1 to 8, and 8
If it exceeds, the fluidity is reduced and the moldability is deteriorated.

By adjusting the amount of the phenol resin curing agent used, the solder crack resistance can be maximized. In order to obtain the effect of the solder crack resistance, the phenol resin curing agent represented by the formula (2) is used in an amount of 50% by weight or more, preferably 7% by weight of the total amount of the phenol resin curing agent.
It is desirable to use 0% by weight or more. If it is less than 50% by weight,
Low hygroscopicity and flexibility under heat cannot be obtained, and solder crack resistance is insufficient.

The other phenolic resin-based curing agents used in combination with the phenolic resin curing agent of the formula (2) include all compounds having a phenolic hydroxyl group. Examples include bisphenol A, bisphenol F, phenol novolak resin, cresol novolak resin, phenol aralkyl resin, and the like. These phenolic resins used in combination are appropriately used for the purpose of adjusting curability, imparting flexibility, etc., but for adjusting fluidity, low molecular weight compounds such as bisphenol F and narrow low molecular weight phenol novolak resins are suitable. .

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 in the range of 70 to 90% by weight. 70% by weight
In the following cases, the amount of moisture absorption is large, and the coefficient of thermal expansion is too large to withstand thermal stress during mounting. 90% by weight
Above this, the flow characteristics deteriorate, making it impractical.

The resin composition for encapsulating a semiconductor of the present invention contains an epoxy resin, a curing agent and an inorganic filler as essential components. In addition to this, a curing accelerator, 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. Further, in order to produce the resin composition for semiconductor encapsulation of the present invention as a molding material, an epoxy resin, a curing agent, an inorganic filler, a curing accelerator,
After sufficiently mixing other additives with 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.

[0018]

The present invention will be described below by way of examples. The mixing ratio is by weight. Examples 1 to 6, Comparative Examples 1 to 4 (A) Epoxy resin ortho-cresol novolak type epoxy resin (epoxy equivalent 200, softening point 65 ° C) Biphenyl type epoxy: 3,3 ', 5,5'-tetramethyl-4 4,4'-dihydroxybiphenyl glycidyl ether (epoxy equivalent 195) bisphenol A diglycidyl ether (epoxy equivalent 200) (B) phenol resin curing agent A phenol resin represented by the formula (2) (hydroxyl equivalent 1)
75, softening point 80 ° C) Phenol novolak resin (hydroxyl equivalent 105, softening point 80 ° C) Phenol aralkyl resin represented by the formula (3) (hydroxyl equivalent 180, softening point 80 ° C) (C) Inorganic filler fused silica powder ( (D) Other raw materials Curing accelerator: Triphenylphosphine Release agent: Carnauba wax The respective proportions shown in Table 1 were mixed at room temperature with a mixer at 70-100 ° C with a biaxial roll. The mixture was kneaded, cooled and pulverized to obtain a molding material, which was tabletted to obtain an epoxy resin composition for semiconductor encapsulation. A low-pressure transfer molding machine (molding conditions: 175 ° C., 70 kg / c)
m ² , 120 seconds).
Post-curing was performed at 5 ° C. for 8 hours and evaluated. Table 1 shows the evaluation results.

Evaluation method * 1 Spiral flow Using a mold for spiral flow measurement according to EMMI-1-66, mold temperature 175 ° C, injection pressure 70 kg / cm ² ,
Measured with a curing time of 2 minutes. * 2 Curability Using a Shore D hardness meter, mold temperature 175 ° C, curing time 2
Measured in minutes. * 3 Heat resistance The glass transition temperature of the cured product was determined by measuring the thermal expansion characteristics of a test piece molded at 175 ° C. for 2 minutes and post-cured at 175 ° C. for 8 hours. * 4 Solder cracking test 85 molded products (chip size 6 × 6 mm, 52pQFP)
After 48 hours and 72 hours of treatment in an environment of 85 ° C. and 85% RH, the wafer was immersed in a solder bath at 260 ° C. for 10 seconds, and external cracks were observed with a microscope. * 5 Solder moisture resistance test Molded product (chip size 3 x 6 mm simulation element, 16 pSO
P) is treated for 72 hours in an environment of 85 ° C. and 85% RH,
Then, after dipping in a solder bath at 260 ° C. for 10 seconds, a pressure cooker test (125 ° C., 100% RH) was performed to measure the number of open defects of the circuit.

[0022]

[Table 1]

[0023]

According to the present invention, it is possible to obtain an epoxy resin composition having good moldability such as curability and mold release properties, a high glass transition point, and resistance to solder stress, which could not be obtained by the prior art. It has excellent resistance to cracks when subjected to thermal stress due to rapid temperature changes during the soldering process, and because of its excellent moisture resistance, it is used for sealing, coating and insulating electronic and electrical components. In particular, when used for highly integrated large chip ICs mounted on surface mount packages
Is suitable for products that require a high degree of reliability.

Continuation of the front page (51) Int.Cl. ⁷ identification code FI H01L 23/31 (58) Fields investigated (Int.Cl. ⁷ , DB name) C08G 59/62 C08G 59/24 C08L 63/00-63 / 10 H01L 23/29

Claims (1)

(57) [Claims] (A) 30% to 100% by weight of a biphenyl type epoxy represented by the formula (1) based on the total epoxy resin amount.
Epoxy resin, containing (Where R ₁ , R ₂ , R ₃ , and R ₄ are hydrogen or CH ₃ and are the same or different atoms or groups) (B) As a curing agent, a phenol resin represented by the formula (2) is used as a total curing agent amount. And a curing agent containing 50 to 100% by weight with respect to (Where X is paraxylylene, n = 1 to 8) (C) An inorganic filler is an essential component, and (C) 70 to 90% by weight of the inorganic filler in the total composition is used for semiconductor encapsulation. Resin composition.