JPH03259960A - Silica filler and its preparation - Google Patents

Abstract

PURPOSE:To prepare a silica filler giving a semiconductor-sealing resin compsn. excellent in flowability, prevention of flash formation, and high-temp. strengths by adhering, to the surface of a fused spherical silica having a specified particle size, a pulverized silica having a particle size smaller than the spherical silica. CONSTITUTION:A mixture of a fused spherical silica having a mean particle size of 10-40mum with a pulverized silica having a mean particle size of 5mum or lower is introduced into and treated in an air current rotating at a high speed, and is then classified under the condition of a classification point of 1-10mum. Thus the particles in the mixture collide with each other in the air current, generating static electricity and physically adhering to each other, and are then classified under a specified classification point to give a silica filler suitable for a semiconductor-sealing resin compsn. The compsn. shows an excellent balance among flowability, prevention of flash formation, and high-temp. strengths.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a silica filler and a method for producing the same.More specifically, the present invention relates to a silica filler and a method for producing the same. The present invention relates to a filler and an industrially advantageous manufacturing method thereof.

(Prior art) Semiconductor resin encapsulation is performed using a encapsulating material made of a resin composition, which is a resin typically epoxy resin filled with a large amount of filler, especially silica. Many patents have been published.

Conventionally, pulverized fused silica has been used as a filler in resin encapsulants for semiconductors, but as the degree of integration of semiconductors has increased, highly filling resin encapsulants have been required, and resin fluidity has been improved. Therefore, fused spherical silica has become indispensable as a filler in place of conventional pulverized products.

Special Publication No. 54-43201, Special Publication No. 61-5734
The invention described in Publication No. 7, etc. is aimed at this type of resin composition, and includes fine spherical particles and average particles Pk1.
It has been shown to use ~60 μm fused spherical silica.

In this way, silica fillers for resin encapsulants include crushed crystalline or amorphous silica crushed with a ball mill, etc., spherical silica melted in a high-temperature flame, etc., and one of these types or It is also known to use two or more types with particle sizes adjusted (JP-A-54-141569, JP-A-55-29532, JP-A-56-10947, JP-A-57-212225). No. Publication, JP-A-62-
261161).

[Problem to be solved by the invention]

In recent years, in the field of highly integrated IC memories, there has been a growing trend for packages to shift from pin-insertion type to surface-mount type, thinner and smaller, and to have more pins.

Furthermore, as the degree of integration of IC memories improves, the area of the IC chip increases, and the chip occupies a larger proportion of the package. Along with this, the occurrence of cracks in packages due to thermal stress caused by the difference in coefficient of thermal expansion between the chip and the package composition has become an important problem.

The coefficient of thermal expansion of the packaging composition decreases as the content of silica filler in the composition increases. Therefore, increasing the silica content in the composition cannot be achieved without improving the fluidity of the composition, and therefore, consideration has been given to using spherical silica in place of the conventionally used crushed silica. When spherical silica is used, it is possible to increase the silica content in the composition due to improved fluidity, but a problem has arisen in that firmness tends to occur during molding of the resin composition. In addition, as surface mounting methods become mainstream, package cracks (cracks that occur when placed in a flow furnace due to a decrease in thermal strength at the solder temperature after moisture absorption), which had not been much of a problem in the past, have become a new problem. This has been pointed out as a problem, and it has been found that especially when a large amount of spherical silica is blended, package cranking is likely to occur due to insufficient strength when heated.

In general, crushed silica has poor fluidity in resin compositions, but
It has excellent Paris properties and high-temperature strength properties, while spherical silica has the opposite tendency. Therefore, in many cases, both types of silica are appropriately blended, and resin sealing is performed using a blending system that sacrifices fluidity.

For example, the above-mentioned Japanese Patent Application Laid-open No. 56-10947 and Japanese Patent Application Laid-open No. 5
7-212225 discloses a filler containing a mixture of crystalline silica powder and fused silica powder, and JP-A-62-261161 discloses a filler containing a mixture of crushed silica and spherical silica. However, according to experiments conducted by the present inventors, it cannot be used as a highly filling filler that simultaneously satisfies the fluidity and Paris characteristics of the sealing resin composition.

In addition, simply mixing spherical silica and crushed silica,
In many cases, it has been found that the mixture not only fails to bring out the best of both worlds, but also compromises its reliability as a filler.

[Means to solve the problem]

In view of the fact of the ridges, the present inventors have conducted numerous experiments and research, and have found that silica filler that can be highly filled as a filler for resin sealing has not only different shapes and particle sizes, but also different silica particles. The present invention was completed based on the finding that the mutual physical bonding relationship between the two is extremely important.

That is, the silica filler provided by the present invention is
It is characterized in that crushed silica finer than the silica particles is adhered to the surface of fused spherical silica particles having an average particle size of IO to 40.

Furthermore, the present invention provides an industrially advantageous manufacturing method for the above-mentioned silica filler, which is characterized by comprising fused spherical silica having an average particle size of 10 to 40 μm and crushed silica finer than the silica particles. After the mixture is put into a high-speed rotating air stream, it is classified under the conditions that the classification point is 1 to 10 μm.

The present invention will be explained in detail below.

The silica filler according to the present invention is characterized in that, as described above, finely crushed silica is adhered to the surface of spherical silica having a relatively large particle size. That is, the silica filler according to the present invention maintains the high fluidity of spherical silica in the sealing resin composition using it, and has a shape effect that cannot be obtained with spherical silica alone due to the shape effect due to the adhesion of crushed silica particles. It is possible to simultaneously satisfy low-temperature properties and excellent high-temperature strength properties, thereby expanding the range of freedom when preparing a resin composition by applying the silica according to the present invention.

The spherical silica according to the present invention has no particular restrictions on the starting materials before melting, and includes crushed products of natural silica stone and crystal, crushed synthetic quartz, powdered sodium silicate obtained by hydrolysis of silane compounds such as alkoxysilane, etc. A powder etc. obtained by reaction with an acid can be used.

Usually, these powdered silicas are dispersed in an oxygen-combustible gas flame, molten and spheroidized, and the particle size is adjusted as necessary.

In the silica filler according to the present invention, it is important that the fused spherical silica has an average particle size of 10 to 40 nm.

The reason for this is that if the diameter is 40n or more, the coarse particles contained therein may clog the gate of the mold, and slit burrs may occur due to the lack of fine particles, which is undesirable.On the other hand, if the diameter is 10μm or less, This is because there is an undesirable tendency to reduce fluidity due to a lack of coarse particles and to generate air vent burrs. Further, such spherical silica often has a BET specific surface area of 0.3 to 51/g. The specific surface area is considered as one of the indicators of the degree of melting of spherical silica, and if it is less than 0.3 m''/g, economically advantageous industrial production is impossible;
If it is more than g, melt spheroidization is insufficient and satisfactory fluidity cannot be obtained.

Next, the silica filler according to the present invention has fine crushed silica attached to the fused spherical silica, which may be either crystalline or amorphous, and may be natural or synthetic. Any material may be used, but a pulverized product of fused silica is preferable.

Although the degree of refinement varies depending on the average particle size of the fused spherical silica and the physical properties of the crushed silica itself, it is necessary that the average particle size is at least 1/2 or less of that of the spherical silica.

The reason for this is that if the degree of refinement is insufficient, the fluidity of the silica filler will decrease.

Therefore, in many cases, the average particle size of crushed silica is 5
It is preferably n or less.

Although there is no particular limitation on the amount of crushed silica attached to spherical silica, it is usually 10 to 50% per total weight.
@t% is preferred. If it is less than 1Qwt%, the effect of improving high temperature strength due to the adhesion of crushed silica is poor, and if it is more than 50-t%, although the high temperature strength is improved, the fluidity is greatly reduced. Therefore, it is preferable to appropriately select the content within the range of 10 to 50 wt% while maintaining a balance between fluidity and high-temperature strength.

The particle size characteristics of the crushed silica and spherical silica according to the present invention are both values based on a particle size distribution measurement method using a laser scattering light method, and examples of measurement models include, for example:
SK Laser (Seishin Enterprise ■) and Cirrus Laser (
Cirrus Inc.), etc.

Furthermore, whether the particles of silica filler are spherical or crushed can be easily confirmed with an electron microscope or an ordinary microscope. The term "crushed" refers to a particle state with a rounded shape without any roundness, and the term "crushed particle" refers to a particle state with an arbitrary shape with corners that the crushed particles have.

It is important that the silica filler according to the present invention has two types of silica having different shapes and particle sizes adhered to each other. Here, adhesion is not a mere mixture of the two, but refers to a state in which fine crushed silica particles are physically adhered to the particle surface of spherical silica having a large particle size.

Next, the method for producing silica filler according to the present invention will be explained in detail.

The spherical silica in the present invention can be industrially advantageously produced by operations having the characteristics described above.

That is, it can be produced by supplying raw material silica powder having predetermined particle size characteristics and specific surface area to a flame melting furnace and melting it into a spheroid, and this method is well known.

Melt spheroidization is carried out using a flame resulting from the combustion of an oxygen-combustible gas, often an oxygen-propane flame, but if a flame at a temperature above the melting point of the silica can be obtained,
The melting method is not particularly limited.

Note that the silica raw material that can be used in this step is not particularly limited, but it is desirable to use natural or synthetic silica with the highest possible purity.

Examples of natural silica include purified silica, silica sand, and crystal, and examples of synthetic silica include those produced by hydrolysis of silicon halides, hydrolysates of organosilicate such as ethyl silicate, or those produced by neutralization of aqueous alkali silicate solutions. Examples include silica.

In particular, the applicant has already successfully developed a method for producing high-purity silica obtained by neutralizing an aqueous alkali silicate solution with a mineral acid, and it can be used as an industrially advantageous raw material for silica. However, the details can be found in, for example, JP-A-61-48421, JP-A-61-48422, JP-A-61-178414, and JP-A-62-
It is described in Publication No. 12608 and the like.

It is also possible to prepare crushed silica by crushing spherical silica, but as mentioned above, it is usually possible to obtain the desired molten warping force in the form of granules or blocks obtained by heating and melting or sintering the silica raw material in a melting furnace. Prepare by crushing in a crusher. In addition, crushed natural silica can also be used if necessary.

In the present invention, it is important and characteristic that the above-mentioned spherical silica and crushed silica are mixed and this mixture is introduced into a high-speed rotating air stream.

At this stage, fine crushed silica adheres to the surface of the spherical silica due to the collision between the spherical silica and the crushed silica and the generation of static electricity. Next, in order to separate the spherical silica to which the crushed silica has adhered to the surface and the crushed silica to which no crushed silica has adhered, classification is performed near the classification point 5n.

The operations from adhesion to classification in such a high-speed rotating airflow can be performed using a forced vortex type classifier, for example,
Equipment such as Tarpo Classifier (Nissin Engineering), Micron Separator (Hosokawa Micron), and Spedic Classifier (Seishin Enterprises) can be used.

The amount of crushed silica deposited is B of spherical silica before deposition.
It can be calculated from the ET specific surface area, the specific surface area of silica after adhesion, and the specific surface area of crushed silica.

The silica filler according to the present invention obtained in this way is suitable as a filler for resin sealing even when used alone, but if necessary, other spherical fillers of a specific particle size can be added using this as a base material. Particle size can also be adjusted to achieve a delicate balance between fluidity, Paris properties, and high-temperature strength properties. Further, if necessary, the surface can be treated with a silane coupling agent or the like before use.

[For production]

The silica filler according to the present invention is a silica filler in which crushed silica, which is finer than the silica, is physically adhered to the particle surface of fused spherical silica having specific particle characteristics. Such silica filler is produced by processing the above-mentioned two types of silica mixture in a vortex type classifier, whereby the mixed particles collide with each other in a high-speed rotating airflow and generate static electricity, resulting in physical adhesion. It can be obtained by separating at a predetermined classification point.

[Example] Hereinafter, the present invention will be specifically explained by giving examples and comparative examples. Note that all parts represent weight.

(1) Preparation A of spherical silica, R50=13. Synthetic silica of 0 μm was dispersed in an oxygen-propane flame and molten into spheroids. The obtained fused silica has R50=33.0 gm, B E T O, 451
/g and by SEM i! Upon inspection, it was found to be spherical.

B, R50=2. OnO Gakai silica was dispersed in an oxygen-propane flame and molten into spheroids. The obtained fused silica was classified to remove coarse particles and R50 = 2.8n, B
Silica with an ET of 2.65 m''/g was obtained. It was confirmed by SEM that it had a spherical shape.

C, R50 = 2.2 μm synthetic silica was dispersed in an oxygen-propane flame and molten into spheroids. The obtained fused silica has R50=2. On, B ET 23m t /
g, and when confirmed by SEM, it had a spherical shape.

(2) Preparation of crushed silica After melting natural quartz, crush it with a ball mill to obtain R50=
4.8n, BE 77.5m"/g of crushed silica was obtained.

(3) Silica filler blended with sealing resin & 1. Kaido acid composition...80 w t% Note (1) Evicron N665, [manufactured by Dainippon Ink Company]
Pour z′ Barcam TD2131, [Dainippon Ink■
[manufactured by Hoechst] Note (3) Manufactured by Hoechst (4) Evaluation of resin composition After kneading the above epoxy resin composition for sealing with a hot roll at 85 to 95°C, the fluidity and Paris properties of the composition were evaluated. , the high temperature strength properties were evaluated.

In other words, the fluidity is EMMI in the transfer molding machine.
The spiral flow value based on 1-66 was measured, and the slit characteristic was evaluated by measuring the slit length extending at the edge of the mold with the slit width adjusted to 5 to Soμm.

The transfer molding conditions are a mold temperature of 170°C.
°C1 resin pressure was set at 70 kg/cm''.

For the measurement of high temperature strength, a test piece for strength measurement (4■-)<lQmmXloo-m) molded with a mold was post-cured (180°C
2 by Autograph [manufactured by Shimadzu Corporation] according to 11.
The three-point bending strength at 20°C was measured. In addition, the high humidity strength after water absorption is determined by P CT (120℃
x 24hrs) test to absorb water, then 220°C
The three-point bending strength was measured. In addition, for one measurement,
The average value was measured using six test pieces.

Example 1 After mixing 300 parts of spherical silica A and 200 parts of crushed silica, this mixture was passed through a classifier [Turbograph Firer].
TC-15N, manufactured by Nisshin Engineering Corporation] to obtain 960 parts of spherical silica to which fine crushed silica was attached.

The classification conditions at this time were: rotor rotation speed 4250RPm;
Air volume 1. Oa+'/min, and the classification point was 4-.

When the particle size and specific surface area of the obtained silica filler were measured, the average particle diameter (R50) was 29.5 fa and the specific surface area (B ET ) was 1.36 m''/g.

The adhesion amount of crushed silica calculated from BET was 12%.

Using this silica filler, a sealing resin All-in-bottom material was prepared, and its fluidity and high temperature strength were measured. The results are shown in Table 1.

Example 2 After mixing 300 parts of spherical silica A and 200 parts of crushed silica, the mixture was passed through a classifier in the same manner as in Example 1 to obtain 970 parts of spherical silica with crushed silica attached. The classification conditions at this time are rotor rotation speed 4000RP - air volume 1.4m
'/min, and the classification point was 5n.

When the particle size and specific surface area of the obtained silica were measured, it was found to be R5.
0 = 28.9- and B E T 1.92 m"/g, and the amount of crushed silica adhered calculated from BET was 20%. A sealing resin composition was prepared using this silica filler, Fluidity and high temperature strength were measured.

The results are also listed in Table 1.

Comparative Example 1 A sealing resin m-acid was prepared using spherical silica A, and its fluidity and high temperature strength were measured. The obtained results are also listed in Table 1.

From Table 1, it was found that the silica filler of Example 1.2 had a high-temperature strength after water absorption that was approximately 30% higher than that of Comparative Example 1, and was suitable as a base filler for preparing high-strength materials.

Example 3 80 parts of silica obtained from Example 1 and 810 parts of spherical silica
A silica filler was prepared by mixing 0.1 parts of spherical silica and 0.10 parts of spherical silica. A sealing resin m-acid was prepared using this silica filler, and its fluidity, Paris properties, and high-temperature strength were measured.
Obtained the results in the table.

Example 4 80 parts of silica obtained from Example 2 and 810 parts of spherical silica
A silica filler was prepared by mixing 0.1 parts of spherical silica and 0.10 parts of spherical silica. A sealing resin composition was prepared using this silica filler, and its fluidity, Paris properties, and high temperature strength were measured.
Obtained the results in the table.

Comparative Example 2 A silica filler was prepared by mixing 80 parts of spherical silica A, 810 parts of spherical silica, and 10 parts of C. A sealing resin composition was prepared using this silica filler, and its fluidity, Paris properties, and high temperature strength were measured, and the results shown in Table 2 were obtained.

Comparative Example 3 A silica filler was prepared by simply mixing 70 parts of spherical silica A, 810 parts of spherical silica, 10 parts of C, and 10 parts of crushed silica without using a vortex classifier. A sealing resin composition was prepared using this silica filler, and its fluidity, Paris properties, and high temperature strength were measured, and the results shown in Table 2 were obtained.

From the measurement results shown in Table 2, it was found that Examples 3 and 4 had well-balanced fluidity, Paris properties, and strength. Also,
Despite using a base material to which crushed silica was attached, the fluidity and elastic modulus were the same as the whole spherical filler of Comparative Example 2, and no decrease in fluidity etc. was observed due to the crushed silica. do not have. The comparative examples have insufficient high-temperature strength, and the high-temperature strength after water absorption is particularly low compared to the examples. Comparative Example 3, in which only crushed silica was mixed, had the drawbacks of slightly low fluidity, high high-temperature strength, but high elastic modulus.

[Effects of the Invention] According to the present invention, a silica filler suitable as a resin filler for semiconductor encapsulation is provided by attaching crushed silica having specific particle characteristics to the surface of spherical silica having specific particle characteristics. Ru.

When a sealing resin composition is prepared using such a silica filler, the composition has an excellent balance of fluidity, Paris properties, and high-temperature strength properties, and in particular, overcomes the drawbacks of conventional spherical fillers. High temperature strength properties can be greatly improved.

Claims (1)

[Scope of Claims] 1. A silica filler characterized by having crushed silica finer than the silica particles adhered to the surface of fused spherical silica particles having an average particle size of 10 to 40 μm. 2. A mixture of fused spherical silica with an average particle size of 10 to 40 μm and crushed silica with an average particle size of 5 μm or less is introduced into a high-speed rotating air stream, and then classified under conditions where the classification point is 1 to 10 μm. Characteristic manufacturing method of silica filler.