JPS6231735B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention has excellent moisture resistance, and also has normal pressure injection properties.
The present invention relates to a liquid epoxy resin composition for semiconductor encapsulation that has excellent curability and high-temperature hydrolysis resistance. Currently, resin encapsulation methods are widely used to encapsulate semiconductor devices such as ICs and LSIs using silicone resin or epoxy resin. Of these, epoxy resin provides relatively good airtightness and is inexpensive. Because of this, it is widely used as a resin for semiconductor encapsulation. Conventional epoxy resin compositions for semiconductor encapsulation include those in which an epoxy resin is blended with a curing agent and a curing accelerator, and those in which the composition is hardened to an appropriate point and made into a solid state, which is then turned into a powder.
It is used in the form of a tablet. When using a tablet-shaped product, the semiconductor element is sealed by placing the tablet-shaped product into a cylinder of a molding machine, heating and melting it at high temperature, and then using a mold clamping press machine in advance. It is injected into a heated mold at a pressure of 20 kg/cm ² or more and cured by heating. When manufacturing such conventional resin compositions for semiconductor encapsulation and encapsulating semiconductor elements, there are various problems. The process up to molding is complicated, and heating and melting takes a long time, which reduces productivity and increases product costs. Furthermore, when encapsulating semiconductor elements, high-pressure molding reduces the efficiency of resin usage, requires the use of expensive mold clamping press machines and high-pressure resistant molds, and also requires the use of semiconductor element wiring and bonding wires. Deformation, misalignment, dashed lines, etc. often occur, leading to high capital investment costs and decreased product characteristics and yield. Therefore, although efforts have been made to develop various liquid semiconductor encapsulating resins, they have not yet been put to practical use in applications requiring high reliability. The biggest reason is that using liquid epoxy resin eliminates most of the above-mentioned drawbacks, but the aluminum wiring of resin-sealed semiconductors corrodes under high temperature and high humidity, resulting in an extreme drop in moisture resistance. This is because new problems will arise. That is, in a liquid epoxy resin composition using an amine-based curing agent, the amine-based curing agent is inherently highly reactive, and not only does the normal pressure injectability decrease in a short period of time after blending, but it also has strong hydrophilicity. Furthermore, due to the reaction between the active hydrogen of the amine curing agent and the epoxy group during curing, highly hydrophilic alcoholic hydroxyl groups are newly generated, which greatly increases water absorption and leads to a decrease in moisture resistance. In addition, even in a liquid epoxy resin composition using a phenolic resin curing agent, the reaction between the phenolic hydroxyl group and the epoxy group produces a highly hydrophilic alcoholic hydroxyl group, resulting in a decrease in moisture resistance.
Furthermore, due to the hydrogen bonding of the phenolic hydroxyl groups, it tends to become semi-solid and has poor normal pressure injectability.To improve this, modifiers such as low-molecular phenol compounds and diluents are usually blended, but when these are blended, heat cures. This tends to cause a decrease in various properties such as the heat distortion temperature of the cured product afterward. On the other hand, in a liquid epoxy resin composition using an acid anhydride as a curing agent, a large amount of a low-viscosity acid anhydride can be blended, so the viscosity of such a resin composition is extremely low and cast molding is possible. . Therefore, it is not necessary to add a deforming agent such as a diluent to lower the viscosity, and various properties such as heat deformation temperature do not deteriorate. Furthermore, the reaction between acid anhydride groups and epoxy groups in the presence of a curing accelerator produces ester bonds with no active hydrogen and low hydrophilicity, resulting in good moisture resistance and On the other hand, it may be used as a resin composition for encapsulating semiconductors such as ICs and LSIs that require high reliability. However, the ester bonds of epoxy resins using the above-mentioned acid anhydrides as curing agents are gradually hydrolyzed by the action of curing accelerators such as ordinary tertiary amines, and because they contain active hydrogen, they become hygroscopic carboxylic acids. There is a problem in that it forms alcoholic hydroxyl groups and moisture resistance over a relatively long period of time. Therefore, it can be applied to LSI and VLSI, which will increasingly require higher humidity resistance and miniaturization in the future, and has excellent moisture resistance and high-temperature hydrolysis resistance, as well as excellent normal pressure injection and curing properties. At present, there is a strong desire to develop a liquid epoxy resin composition for semiconductor encapsulation. In view of these circumstances, the present inventors have conducted extensive research into the relationship between the ester production reaction of epoxy resins using acid anhydrides as curing agents, the hydrolysis reaction, and curing accelerators. The present invention was achieved based on the discovery that extremely favorable results can be obtained only when a specific compound is selected and used as a curing accelerator. That is, in the present invention, the equivalent ratio of liquid epoxy resin/acid anhydride is 1/0.6 to 1/1.0, and the weight ratio of liquid epoxy resin/tertiary amine containing an aromatic hydroxyl group is
Semiconductor encapsulation that is formulated to have a ratio of 100/0.2 to 100/2.0 and further contains an inorganic filler and a coupling agent, and has excellent moisture resistance, normal pressure injectability, curing properties, and high temperature hydrolyzability. The present invention relates to a liquid epoxy resin composition for use. This liquid epoxy resin composition for semiconductor encapsulation, which has excellent moisture resistance, normal pressure injectability, curability, and high-temperature hydrolyzability, can be used as a curing accelerator when ordinary tertiary amines are used. This is possible only when an aromatic hydroxyl group-containing tertiary amine is used as a curing accelerator. Generally, the reaction between an acid anhydride and an epoxy resin requires a long time at a high temperature, so the curing reaction time is attempted to be shortened by using a curing accelerator such as a tertiary amine. When using ordinary tertiary amines, curing time can be shortened by increasing the amount added or using highly active tertiary amines, but the viscosity increases in a short time and normal pressure injection Such tertiary amines, which are free in the cured product and impair the properties of the cured product, also promote the hydrolysis reaction of formed ester bonds under high temperature and high humidity conditions, and promote the formation of carboxylic acid groups, alcoholic hydroxyl groups, etc. As a result, moisture resistance and high temperature hydrolysis resistance are reduced. On the other hand, if the amount added is reduced, the above-mentioned disadvantages will not occur, but the curability will be poor even at high temperatures. On the other hand, when a tertiary amine containing an aromatic hydroxyl group is used as a curing accelerator, the tertiary amine containing an aromatic hydroxyl group greatly inhibits the reaction between the acid anhydride, which is the curing agent, and the epoxy resin at high temperatures. At the same time, the aromatic hydroxyl group reacts with the epoxy group and becomes a component of the cured epoxy resin matrix, and the molecular movement of the promoter is greatly restricted even when exposed to high temperature and high humidity. A liquid epoxy resin composition for semiconductor encapsulation that is difficult to promote hydrolysis reactions, has extremely high moisture resistance, and also has excellent normal pressure injectability, curability, and high-temperature hydrolysis resistance can be obtained. Various types of epoxy resins can be used as the liquid epoxy resin used in the present invention, such as liquid novolak epoxy resin, liquid bisphenol A epoxy resin, and liquid alicyclic epoxy resin. The use of liquid novolak epoxy resins is preferred. These epoxy resins may be used alone or in combination of two or more. In addition to these liquid epoxy resins, if necessary, solid epoxy resins such as brominated novolak epoxy resins and brominated bisphenol A epoxy resins are added in an amount that does not impair workability during normal pressure injection or low pressure injection. If so, they may be used together as appropriate. Examples of the acid anhydride used as a curing agent in the present invention include phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, maleic anhydride,
Examples include hexachloroendomethylenetetrahydrophthalic anhydride, but it is preferable to use hexahydrophthalic anhydride and tetrahydrophthalic anhydride, which have excellent high temperature properties and normal pressure injection properties. These acid anhydrides may be used alone or in combination of two or more, and the amount used is in the range of 0.6 to 1.0 equivalents per equivalent of the liquid epoxy resin. If the amount is less than 0.6 equivalent, it will not cure sufficiently, resulting in poor mechanical properties, and a decrease in heat distortion temperature and moisture resistance.If it is more than 1.0 equivalent, it will be affected by excess acid anhydride, leading to a decrease in moisture resistance. , both are unfavorable. As the aromatic hydroxyl group-containing tertiary amine used in the present invention, for example, 4-(imidazo-1-
lyl)phenol, 4-(1H-1,2,4,triazo-1-lyl)phenol, 4-(dimethylaminomethyl)phenol, 2,4,6-tris(dimethylaminomethyl)phenol, 4-(dimethyl amino)phenol, 2-(dimethylaminomethyl)-3-hydroxypyridine, 2-bromo-3-pyridinol, 2,3,-dihydroxypyridine, 2-hydroxy-6-methylpyridine, 5-chloro-hydroquinoline, 5 -Hydroxypyridine, 2,4-dihydroxy-6-methylpyrimidine, 2,4-dihydroxy-5,6-
Dimethylpyrimidine, 4,6-dihydroxy-2
-Methylpyrimidine, 3,6-dihydroxypyridazine, 9-hydroxy-acridine, etc., but 4-(imidazo-1-lyl)phenol, 4-(1H-1,2,
4-triazo-1-lyl)phenol, 4-(dimethylaminomethyl)phenol, 2,4,6-
Tris(dimethylaminomethyl)phenol, 4
Particular preference is given to using -(dimethylamino)phenol, 2-(dimethylaminomethyl)-3-hydroxypyridine. These curing accelerators may be used alone or in combination of two or more, and the amount used is in the range of 0.2 to 2.0 parts per 100 parts (parts by weight, same hereinafter) of the epoxy resin. If it is less than 0.2 parts, the curing accelerating effect will be poor and the curability of the composition will be poor, and if it is more than 2.0 parts, moisture resistance and storage stability will decrease, which is not preferable. In the present invention, as the inorganic filler, for example, crystalline silica, fused silica, alumina, antimony trioxide, glass fiber, mica, talc, clay, etc. can be used. The use of alumina and antimony trioxide is particularly preferred. These fillers may be used alone or in combination of two or more, and the amount used varies depending on the type, etc.
Generally 100 to 100 parts of liquid epoxy resin
A range of 600 parts is preferred. If it is less than 100 parts, the expansion coefficient will be large and crack resistance will be poor, and if it is more than 600 parts, the viscosity will be high and the normal pressure injection property will be poor, which is not preferable. In the present invention, as a coupling agent, for example, γ-glycidoxypropyltrimethoxysilane, β-(3,4 epoxycyclohexyl)ethyltrimethoxysilane, vinyltri-2-methoxysilane, γ-aminopropyltrimethoxysilane, γ- Mercaptopropyltrimethoxysilane and the like can be used, but γ-glycidoxypropyltrimethoxysilane, β-(3,4-
Preference is given to using epoxycyclohexyl)ethyltrimethoxysilane. These coupling agents may be used alone or in combination of two or more, and the amount used is 0.1 to 3 parts per 100 parts of filler.
parts, preferably in the range of 0.2 to 2 parts. If it is less than 0.1 part or more than 3 parts, the adhesion between the filler and the epoxy resin will be poor, leading to a decrease in moisture resistance, which is undesirable. A coloring agent such as carbon black, a mold release agent such as carnauba wax or polyethylene wax, and a flame retardant may be added to the composition of the present invention, if necessary. The composition of the present invention can be easily prepared by using known mixing devices such as rolls, kneaders, and mixers used for preparing conventional epoxy resins and silicone resins. The present invention will be described below with reference to Examples, Comparative Examples, and Reference Examples. Examples 1 to 9, Comparative Examples 1 to 9, and Reference Examples The components of epoxy resin, acid anhydride, curing accelerator, filler, flame retardant, coupling agent, coloring agent, and mold release agent are shown in Tables 1 and 2. They were blended in the proportions shown in the table and vacuum mixed using a kneader at 40°C for 10 minutes to obtain an epoxy resin composition. The resulting composition was examined for its normal pressure pourability, curability, hydrolysis resistance, and moisture resistance. The results are shown in Tables 3 and 4. Injectability under normal pressure was evaluated based on viscosity at 40°C. Curing properties were evaluated using gel time at 170°C. Regarding hydrolysis resistance, after vacuum casting into a shape of 3 x 5 x 20 mm, it was molded in a PCT (Pressure Cooker) at 121℃, 2 atm, and 100% relative temperature.
Test) and then evaluated by infrared spectroscopy. As for moisture resistance, silicone elements for evaluation of moisture resistance were vacuum cast molded and the time required for defects to occur when left under the above conditions was investigated. In addition, as a reference example, the gelation time of a commercial product (solid transfer mold resin) at 170℃,
Furthermore, the failure occurrence time in the above-mentioned PCT atmosphere of a semiconductor element for evaluating moisture resistance which was transfer-molded using this commercially available product was investigated. The results are shown in Table 5. Comparative Examples 10 to 11 The amount of acid anhydride used in Example 1 was changed to 45 parts and 110 parts (equivalent ratio of epoxy resin/acid anhydride was 1/0.46 and 1/1.13, respectively) (in Comparative Examples 10 and 11, respectively). Example 1 except that it was changed to
It was evaluated in the same way. The results are shown in Table 4. Comparative Example 12 Evaluation was carried out in the same manner as in Example 1, except that the acid anhydride used in Example 1 was not used and 5 parts of 4-(imidazo-1-lyl)phenol was used. The results are shown in Table 4. From the results in Tables 3 and 4, the liquid epoxy resin composition for semiconductor encapsulation of the present invention has excellent normal pressure injection properties, good curability, excellent hydrolysis resistance and moisture resistance at high temperatures, It can be seen that it is extremely useful as a liquid sealing resin composition for semiconductor devices.

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Claims (1)

[Claims] 1. Liquid epoxy resin/acid anhydride in an equivalent ratio of 1/
0.6-1/1.0, liquid epoxy resin/tertiary amine containing aromatic hydroxyl group weight ratio 100/0.2-100/
2.0, and further contains an inorganic filler and a coupling agent. 2 The aromatic hydroxyl group-containing tertiary amine is 4-
(imidazo-1-lyl)phenol, 4-(1H-
1,2,4-triazo-1-lyl)phenol,
4-(dimethylaminomethyl)phenol, 2,
Claim 1, which is at least one member selected from the group consisting of 4,6-tris(dimethylaminomethyl)phenol, 4-(dimethylamino)phenol, and 2-(dimethylaminomethyl)-3-hydroxypyridine. Compositions as described in Section. 3. The composition according to claim 1, wherein the liquid epoxy resin is a liquid novolak epoxy resin. 4. The composition according to claim 1, wherein the acid anhydride is methylhexahydrophthalic anhydride and/or methyltetrahydrophthalic anhydride. 5. The composition of claim 1, wherein the inorganic filler is crystalline silica and/or fused silica. 6 The coupling agent is γ-glycidoxypropyltrimethoxysilane and/or β-
The composition according to claim 1, which is (3,4-epoxycyclohexyl)ethyltrimethoxysilane.