JPH01289842A - Molding agent - Google Patents

Abstract

PURPOSE:To obtain easily at low cost a molding agent having excellent thixotropy and weathering resistance and being useful in the step of sealing in the production of IC by dispersing SiO2 ultramicroparticles of a specified particle diameter prepared by the micelle process in a resin. CONSTITUTION:This molding agent is prepared by dispersing ultramicroparticles of a mean particle diameter <0.1mum, prepared by the micelle process, in a resin. Said micelle process is one for obtaining ultramicroparticles of a desired substance and comprises performing its chemical reaction in the internal spaces of micelles which are associations formed when a surfactant is added to a solvent in a concentration higher than the critical micelle concentration. When the mean particle diameter of the SiO2 ultramicroparticle is above 0.1mum, the specific surface area of the particle is excessively small and the thixotropy and weathering resistance, which are important properties, of the molding agent cannot be improved. Examples of the resin include an epoxy resin and a silicone resin. The amount of the SiO2 ultramicroparticles used is 1-15pts.wt. per 100pts. wt. resin.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a molding agent particularly suitable for sealing electronic components such as ICs.

In the production of Jakuryuki C, the chip is fixed to a lead frame and connected with bonding wire.

The process is to encapsulate it in a package of ceramics, resin, etc. In this encapsulation process, epoxy-based or silicon-based molding agents are mainly used from the viewpoint of insulation, heat resistance, chemical resistance, moisture resistance, etc. In recent years, SiO2 fine particles have been added to these molding agents as fillers mainly for the purpose of improving thixotropy, weather resistance, and reducing costs. These Sin,x fine particles have a small particle size and a narrow particle size distribution.

Although it is known to be effective, particles with an average particle size of 0.1 to 14 m and a wide particle size distribution have conventionally been used due to manufacturing costs and technical problems.

An object of the present invention is to provide a molding agent having excellent thixotropy and weather resistance, which is particularly useful in the encapsulation process of IC manufacturing, simply and at low cost.

(2) The molding agent of the present invention is a molding agent formed by dispersing SiO□ fine particles in a resin.
Fine particles were prepared by the micelle method and had an average particle size of 0.1μ.
The particles are characterized by being ultrafine particles with a diameter of less than 0.0 μm, preferably 0.01 μm or less.

The method for preparing Sin2 fine particles by the micelle method used in the present invention will be described below.

The micelle method is a method to obtain ultrafine particles of the target substance by causing a chemical reaction in the internal space of micelles, which are aggregates that are formed when a surfactant is added to a solvent at a concentration higher than the critical micelle concentration. be. Surfactant used here (can be cationic, anionic, or nonionic)
has a molecular structure in which hydrophobic hydrocarbon groups of C8 to C□ and hydrophilic groups are bonded in an appropriate balance. Such surfactants have different association directions depending on the solvent used, and either form micelles in the solvent as shown in Figure 1(a) or reverse micelles as shown in Figure 1(b). Form.

In the figure, 1 is a hydrophobic group, 2 is a parent wood group, and 3 is a molecular model of a surfactant. When preparing a substance using the micelle method, whether to select micelles or reverse micelles depends on the aqueous phase (high polarity) relative to the reaction system that produces the target substance.
In the case of oxides such as Sin,
Reverse micelles are selected because their production reaction is generally carried out in an aqueous phase reaction system such as a precipitation method or a hydrolysis method. Therefore, as a solvent in this case, an organic solvent with low polarity is preferable.

- To explain the reverse micelle method with reference to Figure 2, it is necessary to first use an appropriate container (if the solvent or reagent used in the reaction system is volatile, or if there is a possibility that other substances may be mixed in from the outside), Collect a predetermined amount of a surfactant aqueous solution with a predetermined concentration into a sealed container. Target substance C has the following formulas (1) and (2)
When it is obtained by the reaction of component A and component B (D is a by-product), as in

A+B4C...(1) A+B-)C+D...(2) While stirring the aqueous solution, an organic solvent solution of component 1 of either A or B, such as component A, is added dropwise.

As a result, component A is incorporated into the aqueous phase of the reverse micelle [Figure 2 (a)]. Next, this is allowed to stand for a predetermined period of time, and after reaching solubilization equilibrium, the other component, for example, an organic solvent solution of component B, is added dropwise while stirring. As a result, the B component is incorporated into the aqueous phase of the reverse micelle [FIG. 2(b)], and at the same time, a reaction between the A component and the B component occurs. By continuing the reaction for a predetermined period of time, ultrafine particles of the target substance C corresponding to the size of the micelles are generated in the aqueous phase of the reverse micelles [Figure 2 (c)]. It can be controlled or a catalyst can be added. In addition, in the case of a reaction system such as the one shown in formula (2), by selecting a solvent in which the by-product is dissolved in a phase different from that of the target substance C, only the target substance C can be produced in the micelles. The particle size and shape of the ultrafine particles can be controlled to some extent by changing conditions such as the type and concentration of surfactant, the concentration of reagents in the reaction system, the amount of catalyst, reaction temperature, and reaction time.

Next, this system is repeatedly subjected to sedimentation by centrifugation, dispersion by ultrasonic waves, and decantation with an appropriate solvent to remove impurities, and the resulting wet particles are dried by an appropriate method to obtain the desired substance. ultrafine particles are obtained in a dry state.

As a reaction system for actually producing ultrafine particles of Sin using the Cemil method as described above, an alkoxide hydrolysis reaction (in a reverse micelle) as shown by the following formula (3) can be mentioned.

Si (QC,H,), + 2 H20→Sin,
+ 4 C, H, OH... (3) The ultrafine particles of Sin of the present invention obtained as above have an average particle size of 0.1μ
It is less than I and has a narrow particle size distribution. If the average particle size is 0.1 μm or more, the specific surface area of the particles is small, making it impossible to improve the properties of rice grain and weather resistance, which are important properties of a molding agent.

The Sin and ultrafine particles of the present invention are mixed with a resin for a molding agent in a desired amount and used. Here, examples of the resin include epoxy resin and silicone resin. Furthermore, SiO□
The appropriate amount of ultrafine particles to be used is 1 to 15 parts by weight per 100 parts by weight of the resin.

The present invention will be explained below by way of examples.

Example 1 The reaction system for producing 5un2 is a hydrolysis reaction of an alkoxide in a reverse micelle of formula (3). The reagents and amounts used were as follows.

Solvent dichlorohexane 5i (QC2H,): 0.2Fo++o12/k
gH,O: 0.5 moQ/kg catalyst:
0.2 moQ/kg First, put the aqueous solution of NP-6 together with the catalyst in a glass container,
A cyclohexane solution of Si (QC,H,)4 is added to this, and the mixture is reacted at 25°C for 48 hours. Next, this system was repeatedly subjected to sedimentation by centrifugation, dispersion by ultrasonic waves, and decantation by methanol, and then the obtained wet particles were dried to obtain spherical SiO□ ultrafine particles with an average particle size of 60 nm.

Next, add 7 in
．． A molding agent was prepared by adding and mixing 5 parts by weight.

Example 2 1 (Example 1 except that the amount was changed to 1.5n+oQ/kg
Spherical SiO□ ultrafine particles with an average particle diameter of 35 nm were prepared in the same manner as above, and a molding agent was made in the same manner.

Example 3 Spherical 5in2 ultrafine particles with an average particle size of 45 nm were prepared in the same manner as in Example 1, except that the reaction temperature was 10° C., and a molding agent was prepared in the same manner.

Example 4 Spherical Sin ultrafine particles with an average particle size of 30 nm were prepared in the same manner as in Example 1, except that the reaction time was 6 hours, and a molding agent was prepared in the same manner.

Comparative Example: Sin with an average particle size of 60n+s, and a commercially available average particle size of 0.00nm instead of ultrafine particles. A molding agent was prepared in the same manner as in Example 1, except that IJLm SiO2 fine particles were used.

Next, each of the above-mentioned molding agents was tested for compatibility with rice and wheat. The test method is as follows.

Rice and wheat properties: Evaluation was made using the thixotropy index (ratio of viscosity at two predetermined rotational speeds measured by a rotational viscometer), which quantitatively expressed rice and wheat properties. The measurement conditions are as follows.

Resin used: Epikote 828, amount added: 5wt, % (stirred for 1hr with a ball mill), rotation speed of viscometer: 20rpm
and 40°C mp, temperature: 25°C The results are shown in the table below.

Since the ultrafine particles of Sin used in the present invention have a large specific surface area, they have a large chemical bonding force with the resin component, and therefore the properties and weather resistance of the molding agent can be greatly improved. Furthermore, since the Sin and ultrafine particles are prepared by the micelle method, it is possible to reduce costs and improve product reliability.

[Brief explanation of the drawing]

FIGS. 1(a) and (b) are model diagrams of micelles and reverse micelles, respectively, and FIGS. 2(a) to (C) are state diagrams of an example of micelles in the preparation process. 3...Molecular model of surfactant having hydrophobic group 1 and parent, water curtain 2

Claims (1)

[Claims] 1. A molding agent formed by dispersing SiO_2 fine particles in a resin, characterized in that the SiO_2 fine particles are ultrafine particles with an average particle size of less than 0.1 μm prepared by a micelle method.