JPH0369939B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a resin composition for encapsulating electronic components, especially α
The present invention relates to a resin composition for encapsulating electronic components that prevents memory elements from malfunctioning due to radiation. Electronic components are generally sealed with a ceramic package or resin to protect them from the external environment, but synthetic resin compositions are commonly used as sealing materials due to cost and productivity considerations. There is. This synthetic resin is composed of an organic resin and an inorganic filler mainly composed of silica, and this composition has the lowest possible expansion coefficient, good thermal conductivity, low moisture permeability, and mechanical properties. In order to obtain an excellent product and a low cost product, it is considered advantageous to incorporate this inorganic filler in as much as possible as far as its moldability allows. Silica-based fillers are considered the most preferable for this purpose, and are used in most resin sealing materials. There are two types of silica-based fillers, crystalline and amorphous, each of which has advantages and disadvantages and is used depending on the purpose and use. On the other hand, silica fillers have a relatively large average particle diameter, from the viewpoint of the large amount of silica fillers mentioned above.
For example, since silica with an average particle size of 1 to 100 μm is used, it can be prepared by powdering natural ore without refining it, or by washing natural ore with water and treating it with hydrofluoric acid at 1000 to 1800°C.
Quartz powder is used, which is obtained by sintering or melting it and then crushing it. On the other hand, memory elements sealed with this type of resin composition have become more integrated as technology advances, and are now highly integrated, called LSI and VLSI. In the case of highly integrated electronic components sealed with resin, this memory element is However, this problem has been developed in recent years due to the problem of malfunctions.
A solution to this problem is desired, as it has a major impact on the design of 64Kbit dynamic MOS RAM. Therefore, as a countermeasure, a method has been proposed in which the surface of the memory element is coated with polyimide resin, silicone resin, etc. in advance to protect the element from alpha ray irradiation; It is difficult to apply the coating to a constant thickness and a constant area on the surface of the memory element, and troubles are likely to occur due to the difference in expansion coefficient between the memory element, these resins, and the above-mentioned sealing resin composition. It is said that this method is not advantageous in terms of production efficiency and economy because there are concerns about the surface area and the complexity associated with the addition of this resin coating process. Therefore, the silica filler used in this resin element material for sealing memory elements is prepared by adding various synthetic silicas currently available on the market, such as silicon tetrachloride, to high temperatures (1850
Dry silica produced by flame hydrolysis with H ₂ and O ₂ at ~2000〓), or by neutralizing hydrated sodium silicate with hydrochloric acid, or by neutralizing hydrated sodium silicate with acid. The use of precipitated silica, silica airgel obtained by neutralization in the coexistence of alcohol, etc., was also considered, but these are all fine particles with an average particle size on the order of mμ and a specific surface area (BET method).
50m ² /g or more, and it also has a large number of silanol groups on its inner and outer surfaces. It has been confirmed that it cannot be filled in a large amount into a resin and therefore cannot be used as a resin for encapsulating electronic components. Furthermore, in the case of silica made from hydrated sodium silicate as a starting material, it is nearly impossible to completely remove residual alkali ions, and the purity is also unsuitable for the above-mentioned purposes. That is, high-purity silica that can be highly filled and is suitable for encapsulating electronic components does not currently exist and is considered impossible to obtain. The present invention relates to a resin for encapsulating electronic components that can solve these disadvantages, and which contains 100 parts by weight of a thermosetting resin or thermoplastic resin,
Distillation-purified alkoxysilane or alkoxy group-containing siloxane is hydrolyzed in an aqueous hydrochloric acid solution with a concentration of 10% or more, and a gelled product with a particle size of 1 μm or more obtained by polymerization is heated to oxidize and sinter at 1200°C or more. Synthetic silica having a specific surface area of 20 m ² /g or less, an average particle size of 0.5 to 100 μm, and a uranium and thorium content of 10 ppb or less is
It is characterized by adding 800 parts by weight. To explain this, the present inventors have conducted various studies on countermeasures against malfunctions of memory elements called soft errors caused by the emission of alpha rays, and have found that this can be easily achieved using chemical engineering means such as distillation as a raw material. If you use an alkoxysilane or alkoxy group-containing siloxane that can be sufficiently purified, the synthetic silica obtained from this can be converted into uranium,
Focusing on the fact that it can contain almost no radioactive elements such as thorium, we have further investigated the production of synthetic silica from this silicon compound. The present invention was completed by discovering that a gelled product obtained by hydrolysis and polymerization with an aqueous hydrochloric acid solution having a concentration of 1.200°C or higher can be heat-treated at 1.200°C or higher. The starting materials for making the synthetic silica used in the compositions of the present invention are alkoxysilanes or siloxanes containing alkoxy groups. This is because if organochlorosilane contains chlorine atoms in its molecules, the silica synthesized from this will contain chlorine atoms, and if a resin composition containing this is used to seal a semiconductor element with resin, reliability tests will be conducted. There is a risk that chlorine atoms will elute and corrode the electrodes for semiconductor devices, but if you use hydrolyzable alkoxysilane that does not contain chlorine atoms or siloxane that contains an alkoxy group, the silica that can be obtained is This is because it does not contain any chlorine atoms and does not have such disadvantages. Examples of this alkoxysilane include tetramethoxysilane [Si(OCH ₃ ) ₄ ], methyltrimethoxysilane [CH ₃ Si(OCH ₃ ) ₃ ], dimethyldimethoxysilane [(CH 3 ) ₂ Si(OCH 3 ) 2 ], and tetramethoxysilane [(CH ₃ ) 2 Si(OCH ₃ ) ₂ ]. Ethoxysilane [Si(OC ₂ H ₅ ) ₄ ], phenyltrimethoxysilane [C ₆ H ₅ Si(OCH ₃ ) ₃ ], dimethyldiethoxylan [(CH ₃ ) ₂ Si(OC ₂ H ₅ ) ₂ ] , diphenyldiethoxysilane [(C ₆ H ₅ ) ₂ Si(OC ₂ H ₅ ) ₂ ], etc.
This can be used as one type or a mixture of two or more types, but this is a siloxane containing an alkoxy group in the molecule, such as a siloxane with the formula (CH ₃ SiO _1.5 ) _o (where n is an arbitrary number). It may also be a polysiloxane in which the terminal group shown is a methoxy group. This alkoxysilane, a siloxane containing an alkoxy group, is made into a gelling product by hydrolysis and polymerization, but this hydrolysis is only 10%
It is necessary to carry out the above in an aqueous hydrochloric acid solution. Although this hydrolysis can be carried out either in an acidic or alkaline aqueous solution, if it is carried out in an alkaline aqueous solution, it is difficult to avoid the contamination of ionic impurities such as Na and K, which cause corrosion of aluminum. Therefore, it is necessary to use an acidic aqueous solution.If this is a 10% or more hydrochloric acid aqueous solution, the hydrolysis and polymerization reactions will proceed quickly, and SiOSi bonds can be easily obtained. This is because even if it remains, it can be easily volatilized during high-temperature heating. In addition, this hydrolyzate is then polymerized to form a gel-like product,
This polymerization can be carried out by polymerizing the hydrolyzed product with an aqueous solution of 10% or more hydrochloric acid alone, or with an aqueous solution of 10% or more hydrochloric acid using an aromatic solvent such as triene or a ketone solvent such as acetone. A gel-like product with a particle size of 1 μm or more can be easily obtained. The particle size of this gel-like product decreases as the hydrolysis temperature increases and as the stirring intensity increases, but when the hydrolysis temperature is -10°C or lower when carrying out the present invention, the speed is slow;
At temperatures above 100℃, when a silicon compound with a low boiling point is used, some of it will hydrolyze in the gas phase, resulting in a gel-like product with a fine particle size. Range, preferably 20℃~80℃
It is said to be in the range of ℃. The gel-like product obtained by this hydrolysis and polymerization is then heated and oxidized at 1200° C. or higher to obtain the desired synthetic silica. This heating is performed to oxidize and cleave the organic groups contained in the polysiloxane, ultimately producing silica that does not contain any organic groups. In order to make it completely free of components, it is preferable to raise the temperature in stages. If the oxidation reaction is carried out at temperatures above 1200℃ without increasing the temperature in stages, silicon carbide will be produced and it will be difficult to obtain silica with good insulation properties, and below 1200℃, sintering will be insufficient and voids will form. This is because it remains
A temperature of 1200℃ or higher is required. The synthetic silica obtained in this way has a sufficiently purified raw material through distillation, so the content of radioactive elements such as uranium and thorium is low.
It has been reduced to less than 10 ppb, especially to a trace level, and this also reduces the moisture resistance of resin compositions made using it as a filler, as well as alkali metal ions such as Na and K, which cause corrosion of aluminum. The content is extremely low, making it particularly suitable as a filler constituting the resin composition for encapsulating electronic components. In the above-mentioned method, by appropriately selecting the conditions, it is possible to obtain particles having a particle size that can be applied as is to a sealing resin composition without any pulverization, and therefore, when a pulverization step is required. There are no disadvantages such as contamination of the silica during the process or disadvantages in terms of purity. When used for this purpose, if the particle size of this synthetic silica is less than 0.5 μm, the fluidity and moldability of the resin composition will deteriorate, and if it is more than 100 μm, the gate of the molding machine will clog during molding. This is required to be in the range of 0.5 to 100 μm. The resin composition for encapsulating electronic components of the present invention is obtained by blending this synthetic silica with a thermosetting resin or a thermoplastic resin, but this resin is not conventionally used for encapsulating electronic components. Examples thereof include thermosetting resins such as epoxy resins, silicone resins, epoxy-silicone resins, and polyimide resins, and thermoplastic resins such as polyphenylene sulfide resins. This silicone resin has, for example, the formula RSiX ₃ (where R and X are the same as above, T unit constituents) and the formula
R ₂ SiX ₂ (R and X are the same as above, D unit constituents)
It can be synthesized by a conventional method of co-hydrolyzing a silane mixture mainly composed of organosilane represented by the formula in the presence of an organic solvent such as toluene, xylene, alcohol or acetone. Of course, even if it has a T or D structure as necessary, for example, CH ₃ SiCl ₃ , C ₆ H ₅ SiCl ₃ , (C ₆ H ₅ ) ₂ SiCl ₂ , (CH ₃ ) ₂ SiCl ₂ , CH _{3 ・ C6H5SiCl2 _}
It is also possible to use two or more types of silanes in combination. Generally, in the present invention, a resin having a T unit content of 70% or more and a large number of functional groups (≡Si-OH) is suitable. In addition, this silicone resin contains a T unit block represented by (T _x D _y ) _z and D as a flexibility imparting agent.
A multi-block polymer consisting of unit blocks may also be added. The curing of the silicone resin is described, for example, in Japanese Patent Publication No. 1973-
As disclosed in No. 3020, Pt, It is carried out by a method that utilizes an addition reaction using an addition reaction catalyst such as a Pt compound, and in the case of a mixed resin of silicone resin and epoxy resin, an Al catalyst as disclosed in Japanese Patent Publication No. 51-118728 is used. A method of curing by curing can also be adopted. In addition, this epoxy resin has at least two epoxy groups in one molecule, and includes those synthesized from epichlorohydrin and bisphenol A and various novolac resins, alicyclic epoxy resins, and Examples include epoxy resins into which halogen atoms such as Cl and Br are introduced. In addition, as curing agents for this resin, amine curing agents represented by diaminodiphenylmethane, diaminodiphenyl sulfone, metaphenylene diamine, etc., phthalic anhydride, pyromellitic anhydride, benzophenonetetracarboxylic anhydride, etc. Either an acid anhydride curing agent or a novolak curing agent having two or more hydroxyl groups in one molecule such as phenol novolak resin or cresol novolak resin can be used. A curing accelerator such as imidazole or its derivatives, tertiary amine derivatives, phosphine derivatives, etc. may be added. Further, as the polyimide resin, those conventionally used for sealing electronic components can be used. In addition, polyphenylene sulfide resin as this thermoplastic resin has the highest heat resistance as a thermoplastic resin, in which benzene rings obtained by the reaction of p-dichlorobenzene and sodium sulfide are linked with sulfur atoms. This material has the characteristics of low moisture permeability, chemical resistance, flame retardancy, and excellent dimensional stability, so it is used for encapsulating electronic components like the silicone resin and epoxy resin mentioned above. It is considered useful. In addition, when these resins mentioned above are used as a composition of the present invention, this composition is particularly
Since the emission of radiation must be prevented, impurities that cause this should be removed as much as possible. Furthermore, it is preferable to use a product that has been purified so that ionic impurities such as Na and K are within a certain limit. The resin composition for encapsulating electronic components of the present invention can be obtained by blending the above-mentioned organic resin and the above-mentioned synthetic silica, but this blending can be carried out using conventionally known hot roll, kneader, or screw type continuous kneading machines. You can do this using . The amount of synthetic silica to be blended is preferably as large as possible from the viewpoint of lowering the expansion coefficient of this composition and imparting good heat dissipation properties to it, but loading of 800 parts by weight or more is recommended. In addition to worsening moldability, there is a risk of deteriorating its mechanical properties, and if the amount is less than 50 parts by weight, the effect will not be fully achieved. Parts by weight are required, particularly preferably in the range of 100 to 500 parts by weight. In addition, various additives such as a silicon compound having an organic group such as an epoxy group and a hydrolyzable atom or group such as a hydroxyl group in one molecule may be added to this composition as necessary. . This compound is commonly referred to as a carbon functional silane or siloxane. The hydrolyzable atom or group can be various, including alkoxy groups, acyloxy groups, etc., but in the present invention, alkoxy groups, particularly methoxy groups, are preferred, and hydroxyl groups are also preferred. Similarly, it is a preferred group. Regarding this optional silicon compound,
When the main component constituting the sealing resin composition is a silicone-epoxy resin, one of the compounds is preferably an epoxy group, and when it is a polyphenylene sulfide resin, an amino group or an epoxy group is preferred. Adducts with amino groups are good. Synthetic silica obtained by the method described above has poor surface activity, is hydrophilic, and easily wets with water, but by adding this optional component, it is possible to combine thermosetting or thermoplastic resin with synthetic silica. The bonding strength of the synthetic silica increases, and furthermore, an optional component can impart the effect of making the synthetic silica hydrophobic. Therefore, it is particularly preferable for the silicon compound to have an organic group such as a methyl group, ethyl group, or propyl group in its molecule in addition to the carbon functional group, from the viewpoint of improving the water resistance of the compound. Examples of such silicon compounds include the following compounds. _{H2NCH2CH2CH2Si ( OC2H5 ) 3 , _} The silicon compound is contained in an amount of 10 parts by weight or less, preferably 0.1 to 10 parts by weight, and more preferably 0.5 to 3 parts by weight, based on 100 parts by weight of the resin. Even if this is added, it is difficult to expect the effect if it is less than 0.1 part by weight;
This is because, if the amount exceeds 1 part by weight, not only will the effect of increasing the amount not be obtained, but also the moldability and physical properties will be adversely affected due to excess components that are not adsorbed on the surface of the synthetic silica. The composition may further contain colorants, flame retardants, and mold release agents, including various atomized fillers such as atomized silica, atomized alumina, Small amounts of fumed titanium oxide may be added, but careful consideration of their purity is required to ensure that no radioactive elements are introduced by their addition. The above-mentioned resin composition of the present invention is molded into an appropriate shape after being blended, but electronic components can be sealed using any of conventionally known injection molding, injection molding, compression molding, and transfer molding. is possible,
According to this method, it is possible to easily obtain a resin-sealed electronic component that is completely free from soft errors due to the emission of alpha rays. Next, examples of the present invention will be given, and all parts in the examples indicate parts by weight. Example (Manufacture of synthetic silica) Three types of synthetic silica were synthesized by the following method. Pour 15% hydrochloric acid aqueous solution into the reaction container.
[4 times the amount of CH ₃ Si (OCH ₃ ) ₃ ], plus CH ₃ Si
(OCH ₃ ) ₃ was gradually added dropwise while stirring. After the dropwise addition was completed, stirring was continued at 60°C for 1 hour. The gel-like material produced here was separated and washed repeatedly with ion-exchanged hot water at 80°C to make it slightly acidic. Next, the gel-like material was dried at 150°C to remove moisture, and placed in a crucible in an electric furnace at 400°C, 600°C, 800°C, 1000°C,
After heat treatment at 1200℃ for 2 hours each, the average particle size
Synthetic silica in the form of a white powder of 15 μm was obtained (synthetic silica A). Add 10% hydrochloric acid aqueous solution (5 times the amount of mixed silane) to the above and reaction container, and add Si
After gradually dropping a 1:1 mixture of (OC ₂ H ₅ ) ₄ and CH ₂ Si (OCH ₃ ) ₃ , the treatment was carried out in the same manner as in the synthesis of synthetic silica A, and then the temperature was increased to 600°C, 800°C, and 1250°C. When the mixture was heat-treated for 2 hours each, a white powdery silica having an average particle diameter of 4.5 μm was obtained (synthetic silica B). Into the same reaction vessel as above, a 15% aqueous hydrochloric acid solution (4 times the amount of siloxane) was charged, and a polysiloxane represented by (CH ₃ SiO _1.5 ) _o (the terminal group is -OCH ₃ and n is 3 to 5) was gradually added dropwise (keeping the internal temperature below 5°C), treated in the same manner as for synthetic silica A above, and then heated at 400°C and 800°C.
When the mixture was ignited at 1000°C, 1000°C, and 1200°C for 3 hours each, and 4 hours at 1400°C, powdered synthetic silica with an average particle size of 1.7 μm was obtained (synthetic silica C).

[Table] (Manufacture of sealing composition) Cresol novolac epoxy resin (product name
EOCN-102, manufactured by Nippon Kayaku Co., Ltd.) 100 parts, phenol novolac resin 60 parts, synthetic silica A to C synthesized above 350 parts, A compound consisting of 2 parts of epoxy group-containing siloxane, 1.9 parts of carnauba wax, and 1.2 parts of 2-methylimidazole was kneaded for 10 minutes with a heated roll, taken out in the form of a sheet, and then crushed to prepare a sealing composition. did. On the other hand, for comparison purposes, the same amount of commercially available silica (melted natural silica) was used instead of synthetic silica, and 3
- A sealing composition was obtained by treating the same composition as above except that the same amount of glycidoxypropyltrimethoxysilane (trade name KBM-403, manufactured by Shin-Etsu Chemical Co., Ltd.) was used. . The sealing composition obtained above was molded using a transfer molding machine at 175°C for 2 minutes, and then post-cured at 180°C for 4 hours. When the alpha ray intensity and volume reduction efficiency of the molded product obtained here were investigated, the results shown in the table below were obtained.

[Table] * Control example
PCT; 120℃, 2Kg/cm ² , in water vapor
Leave for 24 hours

Claims (1)

[Scope of Claims] 1 A product obtained by hydrolyzing and polymerizing 100 parts by weight of a thermosetting resin or thermoplastic resin with an alkoxysilane purified by distillation or an alkoxy group-containing siloxane in an aqueous solution of hydrochloric acid with a concentration of 10% or more. Particle size is 1μ
Heating and oxidizing the gelled product of m or more at 1200℃ or more,
Synthetic silica obtained by sintering has a specific surface area of 20 m ² /g or less, an average particle size of 0.5 to 100 μm, and a uranium and thorium content of 10 ppb or less.
A resin composition for encapsulating electronic components, characterized in that the resin composition is added in an amount of 50 to 800 parts by weight. 2. The composition according to claim 1, wherein the thermosetting resin is an epoxy resin, a silicone resin, an epoxy-silicone resin or a polyimide resin. 3. The composition according to claim 1, wherein the thermoplastic resin is a polyphenylene sulfide resin.