JPS627211B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an epoxy resin composition for encapsulating semiconductors such as resin-encapsulated LSIs, ICs, and transistors. Resin encapsulation materials for semiconductor devices have excellent heat resistance, moisture resistance, mechanical strength, etc., as well as appropriate hardness that will not wear out the mold, and will not damage the internal encapsulation during cooling and heating cycles. In order to prevent this, it is necessary to have a small coefficient of linear expansion, and it is also desirable to have good thermal conductivity in order to prevent heat generation in the semiconductor element. In addition, recently, transfer molding has been widely adopted for encapsulating semiconductors such as LSIs, ICs, and transistors, which has advantages such as low resin injection pressure and less risk of damaging bonding wires that connect semiconductor elements and leads. However, in this case, as the number of molding molds increases, it is required to have a relatively large spiral flow value in addition to the above-mentioned general required characteristics. On the other hand, if the spiral flow value becomes too large, that is, the fluidity becomes too high,
Resin flows out from minute gaps such as mold joints, creating burrs that significantly reduce work efficiency. Also, burrs that occur on the lead wires of semiconductor components are difficult to remove, resulting in solder defects during soldering. or Therefore, it is not enough to simply satisfy the spiral flow value; it is necessary to satisfy the spiral flow value and have excellent burr characteristics that suppress the occurrence of burrs. Conventionally, epoxy resin compositions have been commonly used as resin encapsulation materials for semiconductor devices, especially for transfer molds, and the types and amounts of epoxy resins, their curing agents, fillers, and various additives have been widely used. etc. were used depending on individual requirements. However, among the conventionally known epoxy resin compositions of this type, few have been found that satisfy all of the above-mentioned general required properties and also have excellent spiral flow values and burr properties. The emergence of this product was strongly desired in the industry. This invention was discovered as a result of intensive studies from the above viewpoints, and its gist consists of the following three components: (a) a novolak type epoxy with an epoxy equivalent of 250 or less and a softening point of 60 to 120°C; resin, (b) novolac resin with a softening point of 60 to 130°C, (c) accounting for 60 to 80% by weight of the total composition, particle size 149
Less than 0.5% by weight of things larger than μ, more than 60% by weight of things less than 44μ, and 20 to 5% less than 5μ
55% by weight and the median diameter exceeds 10μ
An epoxy resin composition for semiconductor encapsulation, comprising: crystalline silica powder and/or fused silica powder having a particle size distribution of 30μ or less. That is, the inventors have determined that the above a, b, c
By using the three ingredients as essential ingredients,
While it satisfies the temporary properties required for a sealing material, such as heat resistance, moisture resistance, mechanical strength, appropriate hardness, coefficient of linear expansion, and thermal conductivity, it also satisfies the spiral flow value and burr properties. We have found that both can be improved. The component a used in this invention is a novolac type epoxy resin with an epoxy equivalent of 250 or less and a softening point in the range of 60 to 120°C, and has 2
Among cresol novolac epoxy resins, phenol novolac epoxy resins, etc. having 1 or more epoxy groups, those satisfying the above requirements are selected and used. Here, if the epoxy equivalent is greater than 250, the crosslinking density becomes low and sufficient heat resistance and strength cannot be obtained. Furthermore, if the softening point is lower than 60°C, burrs will occur significantly, and if it is higher than 120°C, the flowability will deteriorate and it will become unsuitable for molding. Furthermore, in the case of epoxy resins other than novolak type, such as bisphenol A type and alicyclic epoxy resins, when the epoxy equivalent is set to 250 or less, the epoxy resin becomes a low viscosity liquid, and in this case, the flash properties are significantly reduced. Or, the heat resistance during molding becomes low. In this invention, in addition to the epoxy resin consisting of component a above, a brominated epoxy resin is used in a proportion of usually 15 to 25% by weight of the total epoxy resin in order to impart a flame retardant function to the molding material. I can do it. As the brominated epoxy resin, preferably used are novolak type such as brominated phenol novolac epoxy resin, brominated cresol novolac epoxy resin, and brominated cresol novolac epoxy resin, but other brominated epoxy resins such as bisphenol A type are used. There is no problem even if it is of the type. Further, the epoxy equivalent and softening point of the brominated epoxy resin are not particularly limited, and conventionally known ones can be widely applied. The b component used in this invention is the above a
It is a curing agent for epoxy resin mainly composed of
Among the novolak resins having two or more hydroxyl groups in the molecule, such as phenol novolac resins and cresol novolac resins, those having a softening point in the range of 60 to 130°C are used. The use of curing agents other than novolac resins, such as amine curing agents and acid anhydride curing agents, is unsuitable because of disadvantages such as poor moisture resistance. Also, the softening point is 60~130
The reason for specifying the temperature is that if the temperature is lower than 60°C, burrs will occur significantly, and if the temperature is higher than 130°C, problems such as poor flowability will occur. Generally, the amount of component b used is preferably such that the ratio of epoxy groups to hydroxyl groups contained in the epoxy resin mainly composed of component a is in the range of 0.7:1 to 1:0.7, with the ratio of epoxy groups to hydroxyl groups being 1:1. . The c component used in this invention is a filler made of crystalline silica powder and/or fused silica powder, and by selectively using such a filler, it has an appropriate hardness that does not damage the mold. is obtained, and good results are obtained in terms of linear expansion coefficient, thermal conductivity, moisture resistance, etc. Other fillers, such as alumina powder, have high hardness and cause severe mold wear during molding, while calcium carbonate and barium sulfate are easily hydrolyzed, resulting in poor moisture resistance of semiconductor parts. In this invention, the above-mentioned crystalline silica powder and/or fused silica powder has a particle size of 149μ or more, 0.5% by weight or less, a particle size of 44μ (350 mesh) or less, 60% by weight or less, and a particle size of 5μ or less.
It is necessary to have a particle size distribution of 20 to 55% by weight and a median diameter of more than 10μ and less than 30μ. If particles with a diameter of 149 μm or more exceed 0.5% by weight, the mold gate will become clogged, resulting in unfilled areas, making complete resin sealing difficult.
In addition, if the weight percentage is less than 60% with 44μ or less, if the percentage with 5μ or less is less than 20% or more than 55% by weight, and if the median diameter exceeds 10μ and falls outside the range of 30μ or less. In both cases, the spiral flow value becomes low and the burr characteristics also deteriorate. The drawing shows particle diameter (μ) on the horizontal axis for silica powder applicable to this invention and silica powder for comparison.
The graph shows a particle size distribution curve in which the vertical axis represents the passing cumulative distribution (wt%) and the horizontal axis represents the logarithmic scale. 95% by weight, 5μ or less is 53
% by weight, fused silica powder with a median diameter of 4.5μ)
Curve 2 corresponds to silica B shown in Table 1 below (64% by weight of particles with a particle size of 44μ or less, 5μ
The following corresponds to 20% by weight of crystalline silica powder with a median diameter of 24μ. Note that both Silica A and Silica B contain 0.5% by weight or less of particles with a particle size of 149 μm or more. This diagram is only for the purpose of making it easier to understand the particle size distribution of silica powder applied to this invention, but as an example, silica powder B having a particle size distribution curve as shown in curve-2 above is , it can be said that the above-mentioned requirements of the present invention are satisfied. and,
Only by satisfying these requirements can good results be achieved in both the spiral flow value and the burr properties, and this is very clear from the Examples and Comparative Examples described later. As described above, the silica powder used in the present invention must have a specific viscosity distribution as described above, but especially silica powder with a relatively high viscosity distribution in which the median diameter is in the range of more than 10μ and less than 30μ. As a result, a high spiral flow value as well as burr properties can be obtained, and very good results can be obtained in terms of moldability. In this invention, the proportion of component c having the above-mentioned structure used must be within the range of 60 to 80% by weight of the total composition. When the amount is less than 60% by weight, the thermal expansion coefficient of the encapsulating material increases, resulting in a peeling phenomenon between the leads of the semiconductor molded product and the encapsulating resin, resulting in a decrease in moisture resistance. In addition, if the amount exceeds 80% by weight, even if the optimum particle size distribution is selected, the spiral flow value will be small, leading to unfilling during molding, and the risk of deforming or breaking bonding wires that connect semiconductor elements and leads. occurs. The epoxy resin composition for semiconductor encapsulation of the present invention has the three components a, b, and c described above as essential components, and may contain a brominated epoxy resin as an epoxy resin below component a, if necessary. Further, curing accelerators such as various amines, various amine complexes of boron fluoride, and various imidazole compounds can be added to these in an amount of 0.1 to 1.0% by weight based on the total composition. In addition, known additives such as inorganic flame retardants such as antimony trioxide, pigments, coupling agents, mold release agents, deterioration inhibitors, and modifiers may be incorporated in an amount of 10% by weight or less based on the total composition. can. The epoxy resin composition of the present invention thus obtained has a relatively large spiral flow value and exhibits excellent moldability by transfer molding. Here, the spiral flow value refers to EMMI1−66 (Epoxy Molding
Material Institute; Society of Plastic
The above measurement value of the epoxy resin composition of the present invention is usually 90 cm or more and 120 cm or less, and particularly preferably 100 cm or more, and 120 cm or less.
It shows a spiral flow of about ~110cm. In order to actually encapsulate various semiconductors with resin using this epoxy resin composition, it is sufficient to cure and mold it by a conventionally known molding method such as transfer molding. It is possible to obtain a resin-sealed semiconductor that not only satisfies general properties such as conductivity but also has excellent burr properties. Examples of the present invention will be described below along with comparative examples. In the following, parts shall mean parts by weight. In addition, the orthocresol novolak epoxy resin used in each example and comparative example has an epoxy equivalent of 215 and a softening point of 88°C, and the brominated phenol novolak epoxy resin has an epoxy equivalent of 265 and a softening point of 92°C. be. Furthermore, the softening point of phenolic novolak resin is 95°C. Further, as the silica powder, eight types of fused silica powder and/or crystalline silica powder shown in Table 1 below were used, each containing 0.5% by weight or less of particles with a particle size of 149 μm or more.

[Table] Examples 1 and 2 Silica B or C shown in Table 1 above is used together with an orthocresol novolac epoxy resin, a brominated phenol novolac epoxy resin, and a phenol novolac epoxy resin, and 2-
Additives such as phenylimidazole, carnauba wax, antimony trioxide, carbon black, and coupling agents are blended in the proportions (parts) shown in Table 2 below, and heated at 80 to 100°C with two rolls.
After heating and kneading, the mixture was cooled and pulverized to a predetermined particle size to obtain two types of epoxy resin compositions for semiconductor encapsulation of the present invention. The spiral flow value (cm) and flash characteristics of each composition are also listed in Table 2. In addition, the burr characteristics are 5
The burr length (mm) was measured using molds for burr evaluation with μ and 50μ clearances. Comparative Examples 1 to 6 Using silica A, D, E, F, G or H shown in Table 1 above, along with an orthocresol novolac epoxy resin, a brominated phenol novolac epoxy resin and a phenol novolac epoxy resin, Additives similar to those in Examples 1 and 2 were blended in the proportions (number of parts) shown in Table 2 below, and six types of semiconductors different from this invention were prepared in the same manner as in Examples 1 and 2. An epoxy resin composition for sealing was obtained. The spiral flow value and flash characteristics of each composition were as listed in Table 2.

【table】

[Table] As is clear from Table 2, the epoxy resin composition of the present invention has excellent flow characteristics (spiral flow) and burr characteristics. In addition, other tests in which semiconductor devices were actually resin-sealed using transfer molding using each composition showed that the epoxy resin composition of the present invention sufficiently exhibited general properties such as heat resistance, strength, and moisture resistance. It was confirmed that resin sealing that satisfies the above is possible.

[Brief explanation of the drawing]

The drawing is a characteristic diagram showing the particle size distribution of silica powder applied to the present invention.

Claims (1)

[Scope of Claims] 1 The following three components; (a) a novolak type epoxy resin with an epoxy equivalent of 250 or less and a softening point of 60 to 120°C, (b) a novolak resin with a softening point of 60 to 130°C, (c) all Accounts for 60-80% by weight of the composition, particle size 149
Less than 0.5% by weight of things larger than μ, more than 60% by weight of things less than 44μ, and 20 to 5% less than 5μ
55% by weight and the median diameter exceeds 10μ
An epoxy resin composition for semiconductor encapsulation, comprising: crystalline silica powder and/or fused silica powder having a viscosity distribution of 30μ or less. 2. The epoxy resin composition for semiconductor encapsulation according to claim 1, which contains a brominated epoxy resin as the epoxy resin other than component a.