JPH03257009A - Silica-based filler - Google Patents

Abstract

PURPOSE:To improve the packing ratio by crushing a silica grain with an impact crusher substantially into a globular silica grain having a specified diameter and having >=1 recess on its surface. CONSTITUTION:A rotary disk 5 having a blade 6 is rotated at high speed to exert centrifugal force on the air in the blade, hence the outside of the disk 5 is pressed, and a negative pressure is produced at the center of the disk 5. The compressed air outside the disk 5 is moved to the center of the disk 5 through a circulating circuit 3, and an air circulating flow is formed. Under these conditions, globular silica grains are charged from a powder feed chute 2 set in the middle of the circuit 3. The silica grain is circulated along with the circulating flow and subjected to the impact force produced by the collison between the grains and with the blade 6, and the reformed globular silica grains having 1-100mum diameter and 5-50mum average diameter and >=50wt.% of which has >=1 recess having 0.1-1mum depth on its surface are obtained.

Description

Detailed Description of the Invention [Object of the Invention] (Industrial Application Field) The present invention relates to a novel silica-based filler. Specifically, the present invention provides a silica-based filler that can be highly filled into a resin and can significantly improve the mechanical strength of the resin.

(Prior art) In recent years, high filling of fillers into resin has been developed for the purpose of improving the dimensional stability of resin molded products during molding, improving the mechanical strength of resin molded products, and reducing the coefficient of thermal expansion of resin molded products. is being considered.

For example, LS1. Encapsulants such as epoxy resins used to protect semiconductor circuits such as VLSIs are also highly filled with fillers in order to improve the reliability of the resulting semiconductor chips and increase yields. ing.

Conventionally, fillers made of silica powder with spherical particle shapes have been proposed as such fillers for high filling. As a method for preparing this type of spherical silica powder, for example, as shown in Japanese Patent Application Laid-open No. 57-95877, amorphous silica powder is introduced into a flame having a temperature higher than the melting point. Method for spheroidizing particles (melting method), JP-A-61-190
As shown in No. 556, etc., there is a method in which a metal alkoxide is dispersed in a water-alcoholic solvent, hydrolyzed, then dried and fired (sol-gel method).

These spherical silica powders have good fluidity,
It is easy to highly fill the resin.

However, although the filler made of silica powder in which each particle is spherical can be highly filled into the resin, the mechanical strength of the resulting resin molded product is
This has the problem of causing a decrease in thermal shock properties.

(Problems to be Solved by the Invention) The present inventors have conducted repeated research in order to solve the problems of the prior art resin filler made of silica powder with spherical particle shapes. As a result, a filler made of silica powder containing a specific proportion of spherical silica particles that are within a specific particle size range and have irregularities of a specific size on the surface is changed from the conventional spherical silica powder. It has been discovered that the mechanical strength and thermal shock properties of the resulting resin molded article can be significantly improved while exhibiting good fluidity equivalent to that of fillers, leading to the completion of the present invention.

[Configuration 1 of the Invention (Means for Solving the Problems) To summarize the present invention, the present invention provides particles having a particle diameter of substantially 1 to 1.
IflOtLm, and the average particle size is 5 to 5.
Relating to a silica-based filler made of 0 μm silica powder, wherein 50% by weight or more of the silica powder is spherical silica particles having one or more irregularities with a depth of 0.1 to 1 μm on the surface. It is something.

In the present invention, the depth of the irregularities on the surface of the silica particles and the number of the irregularities are values measured by a surface shape analyzer having a non-contact laser surface roughness meter with a spot diameter of 1 μm as a detection unit. The depth of the above-mentioned irregularities is a value obtained by measuring the difference in height between the highest and lowest parts on the slope of a predetermined irregularity that exists continuously in a certain direction on the particle surface. Further, the number of irregularities is the number of irregularities having the depth measured by scanning the surface of a predetermined particle.

In the present invention, spherical means substantially spherical, and does not mean only perfect pearls. Generally, the sphericity (major axis/minor axis ratio) is 06 or more,
Preferably, any shape having a shape of 0.8 or more may be used.

The filler of the present invention has a particle size of substantially 1 to 100 μm.
It is important that the particle diameter is in the range of 5 to 50 μm and that the average particle diameter is comprised of silica powder. That is, if particles with a particle size smaller than 1 μm are present, the viscosity increases significantly when mixed with the resin, and not only can they not be uniformly dispersed in the resin (also, high filling tends to be difficult,
Furthermore, if particles with a particle size exceeding 100 μm are present, the surface smoothness of the obtained molded product will not only decrease (
, stress concentration occurs at the interface between the particles and the resin, which tends to cause a decrease in the bending strength of the molded article. Furthermore, if the average particle size is smaller than 5 μm, the particle size distribution of the silica particles will be too biased toward small particle sizes, and if the average particle size is larger than 50 μm, conversely, the particle size distribution of the silica particles will be biased toward large particle sizes. In either case, it becomes difficult to increase the filling rate into the resin. In the present invention, the fact that the particle diameter is substantially in the range of 1 to 100 μm allows for the presence of particles smaller than 1 μm that are attached to the particles due to the action of static electricity or the like.

Furthermore, the filler of the present invention is composed of spherical silica in which 50% by weight or more, preferably 70% by weight or more, has one or more irregularities on the surface with a depth of 0.1 to 1 μm, preferably 0.3 to 1 μm. It is important that the particles be composed of particles (such spherical silica is hereinafter also referred to as "modified spherical silica particles"). That is, in the present invention, it is important to satisfy both the above-mentioned predetermined usage ratio of the modified spherical silica particles and the depth of the unevenness. For example, even if one of the usage ratios is satisfied, if the depth of the unevenness existing on the surface of the spherical silica is shallower than the above range, the mechanical strength and heat The effect of improving impact properties is insufficient, and if the depth of the unevenness is deeper than 1 μm, the fluidity of the filler decreases, making it difficult to highly fill the resin. In addition, in the modified spherical silica particles, it is preferable to form as many irregularities on the surface as possible. Generally, 5 or more pieces per 100 μm2,
Preferably, the unevenness is present at a density of 10 or more.

Further, when the proportion of the modified spherical silica particles used in the filler is less than 50% by weight, for example, the proportion of the modified spherical silica particles is reduced to less than 50% by weight by mixing with irregularly shaped silica particles. In this case, the fluidity of the filler is not sufficiently improved, making it difficult to highly fill the resin. In addition, if the proportion of the modified spherical silica particles is less than 50% by weight due to mixing with spherical silica particles with smooth surfaces, the mechanical strength and thermal The effect of improving impact properties is insufficient.

In the filler of the present invention, the shapes of other silica particles used together with the modified spherical silica particles are not particularly limited. Examples include amorphous silica produced by crushing bulk silica, spherical silica particles, and crushed products of the spherical silica particles. Among these, amorphous silica is preferably used because it is effective in improving the mechanical strength and thermal shock properties of a molded article obtained by filling a resin with the filler.

Conventionally, as a method of processing spherical silica particles to form a filler, there is one disclosed in, for example, Japanese Patent Application Laid-Open No. 12609/1983. In this process, spherical particles are processed by powerfully shearing fused spherical silica using a ball mill or the like.

In this treatment method, a strong shearing force acts between fused spherical silica particles, causing a mechanochemical reaction on the particle surface, increasing the specific surface area, and improving the surface. According to the experiments conducted by the present inventors, in the process of applying such a strong shearing force, not only the particle surface is modified, but also the particles themselves are mainly crushed, and as a result, a large amount of fine powder of less than ILLm is generated. will be generated. Therefore, the above-mentioned filler has the problem that not only does the specific surface area increase apparently due to the presence of the fine powder, but also that it becomes difficult to highly fill the resin.

In contrast, the filler of the present invention does not substantially contain particles with a particle diameter of less than 1 μm as described above, and contains 50% by weight or more of the specific modified spherical silica particles described above. As a filler, it can exhibit the excellent effects described above. The filler of the present invention generally has a specific surface area of 0.1 to 3 m''/g.

In the present invention, the purity of silica is not particularly limited, but when it is used as a filler for the semiconductor encapsulating material described above, the content of radioactive substances such as uranium and thorium is preferably 51) pb or less, preferably , 11) l) b and below,
Electrolyte substances containing sodium, potassium, chlorine, etc. having a purity of 20 ppm or less, preferably 5 ppm or less are suitably used.

Next, a method for producing modified spherical silica particles, which are characteristic particles of the silica filler of the present invention, will be described.

The method for producing the modified spherical silica particles of the present invention is not particularly limited, but to give an example of a typical production method, an impact mill is used to create irregularities with a depth of 0.1 to 1 μm on the particle surface. One example is a method of treating spherical silica particles under conditions that produce spherical silica particles or more.

In the above method, spherical silica particles manufactured by a known method can be used without particular limitation. For example, those obtained by the above-described melting method or sol-gel method are preferably used.

As the impact crusher used in the method for producing modified spherical silica particles of the present invention, any known impact crusher can be used without any particular restriction. As this type of impact crusher, any type of impact crusher may be used as long as it can mainly apply impact force to the particles to be treated, such as a closed circuit impact type impact crusher (hereinafter referred to as
It's called a pipe retizer. ) is preferred. 1st
The schematic internal structure of the hybridizer shown in the figure is shown.

In FIG. 1, 1 is a powder input valve, 2 is a powder input chute, 3 is a circulation circuit, 4 is a casing, 5 is a rotary disk, 6 is a blade, 7 is a stator 8 is a cooling or heating jacket, 9 indicates a powder discharge chute, and 10 indicates a powder discharge valve. Note that the arrow indicates the locus of the powder.

Such a pipe retizer operates as described below to form recesses on the surface of spherical silica particles. That is, when a rotary disk having blades 6 is rotated at high speed, the blades 6
As a result, a centrifugal force acts on the internal air, the outside of the rotary disk 5 becomes pressurized, and the center of the rotary disk 5 becomes under negative pressure.

Thus, the pressurized air outside the rotary disk 5 is transferred to the center of the rotary disk 5 via the circulation circuit 3, thereby forming a circulating flow of air. In a state where such a circulating air flow is formed, when spherical silica particles are introduced from the powder input chute 2 provided in the middle of the circulation circuit 3,
The spherical silica particles circulate through the circulation circuit together with this circulating flow, and during this time they are mainly subjected to impact forces due to collisions between the particles and collisions with the blade 6, forming recesses on their surfaces.

The processing conditions for spherical silica particles using the above-mentioned impact crusher are such that the particle surface has a depth of 0.1=ILLm, preferably 0.1 ILLm.
Conditions are selected that produce one or more unevenness of 3 to 1 μm. Generally, conditions are selected in the above-mentioned impact pulverizer so that the target particles are not substantially pulverized. Specifically, a method may be mentioned in which the treatment is performed using an impact force of 20 to 90%, preferably 30 to 90%, of the impact force at which particles having a particle size of about 100 μm begin to be crushed. It goes without saying that the impact force at which the particles begin to be crushed can be determined in advance through experiments using spherical silica particles containing particles with a particle size of 1100 U, taking into account factors such as the processing intensity and processing time by the impact crusher. There is no such thing. In the case of a rotary impact crusher, the impact force can be compared based on the number of rotations.

Further, the particle density of the spherical silica in the airflow in the impact crusher is preferably 10 to 100 kg7m''.

The particle density in the air stream mentioned above is the value obtained by dividing the weight of the particles supplied to the grinding chamber of the impact grinder by the volume of the particles.

If the particle density in the airflow is smaller than the above range, the probability of particles colliding with each other will be small, and if the particle density is larger than the above range, the heat generation of the processing system will be large, and particles,
It becomes difficult to obtain modified spherical silica particles having concave portions of a desired size due to reasons such as adverse effects on equipment and the like. In addition, if the impact force is smaller than the above range,
The formation of depressions on the surface of spherical silica particles is insufficient,
It becomes difficult to form recesses of a size that is satisfactory for the modified spherical silica used in the present invention on the surface. Furthermore, if the impact force is larger than the above range, the spherical silica particles begin to be crushed, making it impossible to obtain the desired modified spherical silica. The treatment time is not particularly limited, but if it is too short, the number of unevenness on the particle surface will decrease, and if it is too long, the particle diameter will decrease. It is preferable to do this for about a minute.

When spherical silica particles are processed by the method of the present invention described above, if free fine powder smaller than 1 μm is generated in the impact mill, this can be removed to obtain the modified spherical silica used in the present invention. Bye. The method for removing such fine powder is as follows:
Known methods can be employed without particular restriction. Examples include methods using wet classifiers such as rake classifiers and liquid cyclones, and dry classifiers such as air separators and zigzag classifiers.

As described above, according to the method for producing modified spherical silica particles of the present invention,
Modified spherical silica particles having one or more irregularities with a depth of 0.1 to 1 μm on the surface are efficiently produced. Incidentally, the irregularities present on the surface of the modified spherical silica particles of the present invention have edge portions constituted by sharp ridges at the edges thereof. Therefore, when used as a filler, the presence of the edge portion provides an additional effect, and the effect of improving the strength of the resin molded product can be further promoted.

The filler of the present invention is preferably surface-treated to improve its affinity with the resin. As such a process, any known process may be employed without particular limitation. For example, a method of treating the particle surface with a treatment agent such as a silane coupling agent bonded with a group reactive with a resin is suitable, if necessary.

The filler of the present invention can be filled into a known thermoplastic resin or a known thermosetting resin without particular limitation.

Typical examples of thermoplastic resins include polyolefins such as polypropylene and polyethylene, polycarbonate, and examples of thermosetting resins include epoxy resins and phenol resins.

The filler of the present invention can be highly loaded into these resins, but in particular, the filler can be used at a high filling rate of 30 parts by weight per 100 parts by weight of the resin.
When added in an amount of up to 90 parts by weight, preferably 60 to 90 parts by weight, various properties such as good mechanical strength and one-dimensional stability can be imparted to the resulting molded article.

[Effects of the Invention] As can be understood from the above explanation, the filler of the present invention maintains the same fluidity as spherical silica used as a conventional filler, and can be used for resin molding obtained by filling it. The mechanical strength and thermal shock properties of the body can be significantly improved. In particular, when a thermosetting resin such as an epoxy resin is highly filled and used as a semiconductor encapsulant,
These properties make it possible to significantly improve the durability, mechanical strength, etc. of the resulting semiconductor chip.

(Examples) Hereinafter, in order to explain the present invention more specifically, Examples will be shown, but the present invention is not limited to these Examples.

In addition, in the Examples and Comparative Examples, the depth and density of the unevenness on the particle surface, the moldability of the filler-filled resin, the bending strength,
Thermal shock resistance was measured by the following method.

(2) Depth and density of irregularities on the particle surface These are values measured using a surface shape analyzer (5AS2010; trade name, manufactured by Meishin Koki (2)) whose detection unit is a non-contact laser surface roughness meter with a Nispot diameter of 1 μm. The depth of the above-mentioned unevenness was determined by measuring the difference in height between the highest and lowest parts of the sloped surface that exists continuously in a certain direction on the particle surface.

In addition, upon measurement, fine powder adhering to the surface of the particles was removed in advance. Moreover, the depth and density of the unevenness indicate the average value of 50 arbitrarily selected particles.

■Average particle size and particle size range: Light diffraction scattering particle size distribution analyzer (PRO-7000 type,
■Measurement was made by Seishin Enterprise Co., Ltd.).

■Moldability of filler-filled resin: For the resin compositions shown in Table 1 below, American Plastics Association standards: EMMI (EPOXY MOLDING MAT)
The spiral flow value was measured according to ERIALS IN5TITUTE) 1-66. In addition, the mold temperature is 1
At 75°C, the transfer pressure was 70 kg/cm2.

Table 1 - Bending strength: The resin compositions shown in Table 1 were tested at a mold temperature of 180°C for 4 hours.
Form into a size of mm x 16 mm x 80 mm, 1
After post-curing for 80'CX6 hours, JIS K6
The measurement was performed according to the bending strength measurement method of 911.

■Thermal Shock Resistance II (Reflow Resistance): Using the resin composition shown in Table 1, a 6 mm square semiconductor chip set on a lead frame was molded at a mold temperature of 180°C, and post-cured at 180°C for 6 hours. 64 pin Q F P f14mm x 16mm x 2.7mm
)It was created. This QFP was placed at a temperature of 85℃ and a relative humidity of 85℃.
% conditions for 8 hours, and then the crack generation rate during vapor reflow at 215° C. for 90 seconds was measured.

■Specific surface area: BET using 5A-1000 model manufactured by Shibata Kagaku Kikai Kogyo Co., Ltd.
It was measured by the method.

Examples 1 to 6 and Comparative Examples 1 to 5 The molten spherical silica powder shown in Table 2 was supplied to an impact crusher (hybritizer type NHS-1; trade name, manufactured by Nara Kikai Seisakusho ■). After processing under the conditions shown in the table, the particles were classified to obtain modified spherical silica particles having particle diameters and surface irregularities shown in Table 2.

In addition, A-1 particles (Example 1) and B-1 particles (Example 1) in Table 2
The surface diffraction patterns of Comparative Example 1) are shown in Figures 2 and 3, respectively.
As shown in the figure. These surface diffraction patterns were measured using the above-mentioned surface shape analyzer. That is, the surface analysis pattern (4 pitches, fa in each figure) ~ [d
Corresponds to +. ).

In addition, A-1 particles (Example 1) and B-1 particles (Example 1) in Table 2
Scanning electron microscope (SEM) showing the surface structure of Comparative Example 1)
I photos are shown in Figures 4 and 5, respectively. These SEM
As shown in the photograph, the modified spherical silica particles of the present invention (
Fig. 4) has sharp edges on the edges of the unevenness.

The modified spherical silica shown in Table 2 and the amorphous wrinkle strength obtained by crushing were mixed to have the composition shown in Table 3 to obtain a filler having the particle size distribution shown in Table 3.

The obtained fillers were mixed in the proportions shown in Table 3, and blended to have the compositions of the resin compositions shown in Table 1 above. Various test results for this resin composition are also shown in Table 3.

(Margin below)

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an impact crusher used for producing the filler of the present invention. In addition, Figure 2 shows the surface diffraction pattern of the A-1 particle, and the third
The figure shows the surface diffraction pattern of B-1 particles. FIG. 4 is an electron micrograph showing the surface structure of A-1 particles (invention), and FIG. 5 is an electron micrograph showing the surface structure of B-1 particles (comparative example). In FIG. 1, 1 is a powder input valve, 2 is a powder input chute, 3 is a circulation circuit, 4 is a casing, 5 is a rotary disk, 6 is a blade, 7 is a stator 8 is a cooling or heating jacket, 9 indicates a powder discharge chute, and 10 indicates a powder discharge valve. Note that the arrow indicates the locus of the powder. Patent applicant Soda Tokuyama Dodo Co., Ltd.
Toyo Ink Manufacturing Co., Ltd. Representative Patent Attorney Yoshio Mizuno Kayu 4 Figure

Claims (1)

[Claims] (1) The particle size is substantially in the range of 1 to 100 μm,
and made of silica powder with an average particle diameter of 5 to 50 μm,
The silica powder contains 50% by weight or more on the surface at a depth of 0.1
A silica-based filler characterized by being spherical silica particles having one or more irregularities of ~1 μm.