JP2958402B2 - Silica filler for semiconductor resin encapsulation and method for producing the same - Google Patents

Description

Description: TECHNICAL FIELD 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 having specific particle characteristics suitable as a silica filler for resin sealing of a semiconductor and an industrially advantageous production method thereof.

[Conventional technology]

Resin encapsulation of semiconductors is performed by encapsulating material of a resin composition filled with a resin such as epoxy resin, especially a large amount of filler mainly composed of silica, and many patents have already published this relationship. Have been.

Conventionally, pulverized fused silica has been used as a filler for semiconductor resin encapsulants, but recently, as the degree of integration of semiconductors has increased, high filling resin encapsulation has been required to improve the fluidity of the resin. For this reason, fused spherical silica has become indispensable as a filler in place of conventional pulverized products.

The inventions described in JP-B-5-43201 and JP-B-61-57347 are directed to this type of resin composition, and include fine spherical particles and molten spherical particles having an average particle diameter of 1 to 60 μm. The use of silica has been shown.

As described above, the silica filler for the resin sealing material includes crushed crystalline or amorphous silica pulverized by a ball mill or the like, spherical silica melted in a high-temperature flame, or the like. It is also known to use two or more kinds of which are adjusted in particle size (JP-A-54-141569, JP-A-55-141569).
No. 29532, JP-A-56-10947, JP-A-57-2122
No. 25, JP-A-62-261161).

[Problems to be solved by the invention]

In recent years, in the field of high-integration IC memories, packages are increasingly becoming thinner, smaller, and more pins from pin insertion type to surface mount type.

Further, as the degree of integration of the IC memory increases, the area of the IC chip increases, and the occupation ratio of the chip in the package is increasing. Along with this, the generation of cracks based on thermal stress caused by the difference in the coefficient of thermal expansion between the chip and the package composition has become an important problem.

The coefficient of thermal expansion of the package composition decreases as the content of the silica filler in the composition increases. Therefore, in order to increase the silica content in the composition, it cannot be achieved without improving the fluidity of the composition, and therefore, the use of spherical silica instead of conventionally used crushed silica has been studied. When spherical silica is used, although the flowability is certainly improved, the silica content in the composition can be increased. However, there has been a problem that burrs are easily generated at the time of molding the resin composition. In addition, as the surface mounting method has become mainstream, package cracks (cracks that occur when placed in a reflow furnace due to a decrease in hot strength at the solder temperature after moisture absorption) have been a new problem. In particular, it has been found that when a large amount of spherical silica is blended, package cracks are likely to occur due to insufficient strength at the time of heating.

In general, crushed silica is inferior in fluidity of a resin composition, but is excellent in burr characteristics and high-temperature strength characteristics, while spherical silica has the opposite tendency. Therefore, in many cases, both silicas are appropriately blended, and the resin is sealed with a blending system in which fluidity is sacrificed.

For example, JP-A-56-10947 and JP-A-57-212 described above.
No. 225 discloses a mixture of crystalline silica powder and fused silica powder, and JP-A-62-261161 discloses that a mixture of crushed silica and spherical silica is used as a filler. According to the experiments of the present inventors, it cannot be used as a highly-fillable filler that simultaneously satisfies the fluidity and the burr characteristics of the sealing resin composition.

In addition, it has been found that, in many cases, the mere mixing of the spherical silica and the crushed silica cannot not only bring out the advantages of both but also impose reliability on the filler.

[Means for Solving the Problems] In view of the above-mentioned facts, the present inventors have conducted a number of experiments and studies, and as a result, as a silica filler that can be highly filled as a resin sealing filler, the shape and particle size are of course In addition, they have found that the mutual physical bonding relationship with different silica particles is extremely important, and completed the present invention.

That is, the silica filler for semiconductor resin encapsulation provided by the present invention, the crushed silica finer than the silica particles on the surface of the fused spherical silica particles having an average particle diameter of 10 to 40 μm collide with each other in a high-speed rotating airflow. And physical adhesion accompanied by generation of static electricity.

Furthermore, the present invention is to provide an industrially advantageous method for producing the above silica filler, characterized by fused spherical silica having an average particle size of 10 to 40 μm and crushed silica finer than the silica particles. Is put into a high-speed rotating airflow, and then classified at a classification point of 1 to 10 μm.

 Hereinafter, the present invention will be described in detail.

As described above, the silica filler according to the present invention is characterized in that finely crushed silica is adhered to the surface of spherical silica having a relatively large particle diameter. That is, the silica filler according to the present invention can be obtained by using the spherical silica alone due to the shape effect due to the adhesion of the crushed silica particles while maintaining the high fluidity of the spherical silica with respect to the sealing resin composition using the same. It is possible to simultaneously satisfy no burr characteristics and excellent high-temperature strength characteristics, and expand 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 is not particularly restricted with respect to the starting material before melting, and is obtained by pulverizing natural silica or quartz, pulverized synthetic quartz, powdered sodium silicate obtained by hydrolysis of a silane compound such as alkoxysilane. Powders obtained by reaction with an acid can be used.

Normally, these powdered silicas are dispersed in an oxygen-flammable gas flame, melted and spheroidized, and the particle size is adjusted as required.

It is important that the fused spherical silica in the silica filler according to the present invention has an average particle size of 10 to 40 μm.
The reason for this is that when the thickness is 40 μm or more, coarse particles contained therein may be clogged in the gate portion of the mold and slit burrs may be generated due to shortage of fine particles. On the other hand, when the thickness is 10 μm or less, the flowability is reduced due to the lack of coarse particles, and air vent burrs are generated. Such spherical silica often has a BET specific surface area of 0.3 to ⁵ m ² / g. The specific surface area is taken as one of the indicators of the melting degree of the spherical silica, those of less than 0.3 m ² / g is not economically advantageous industrial production, not less than 5 m ² / g in the opposite Is insufficient in melt spheroidization to obtain satisfactory fluidity.

Next, the silica filler according to the present invention is one in which fine crushed silica is adhered to the fused spherical silica, which may be either crystalline or amorphous,
It may be either natural or synthetic. Preferably, a crushed product of fused silica is used.

Although the degree of fineness is not uniform due to the average particle diameter of the fused spherical silica and the physical properties of the crushed silica itself, it is necessary that the average particle diameter is at least 1/2 of that of the spherical silica.

The reason for this is that if the degree of fineness is insufficient, the fluidity of the silica filler is reduced.

Therefore, in many cases, the average particle size of the crushed silica is
Those having a size of 5 μm or less are preferred.

The amount of the crushed silica attached to the spherical silica is not particularly limited, but is usually 10 to 50 wt.
% Is preferred. If it is less than 10 wt%, the effect of improving the high-temperature strength due to the adhesion of crushed silica is poor. Therefore, while maintaining the balance between fluidity and high-temperature strength, 10
It is better to select as appropriate within the range of ~ 50 wt%.

The particle size characteristics of the crushed silica and the spherical silica according to the present invention are values based on a particle size distribution measurement method using a laser scattering light method. Examples of the measurement models include SK laser (Seishin Enterprise Co., Ltd.) And Cirrus Laser (Cirrus Inc.).

Whether the particles of the silica filler are spherical or crushed can be easily confirmed with an electron microscope or an ordinary microscope, and the spherical shape in the present invention is a true sphere or a substantially square shape. It refers to a particle state having no roundness and a crushed state, and the term "crushed state" refers to a state having a crushed particle having an arbitrary shape with corners.

It is important that the silica filler according to the present invention is in a state where two types of silica having different shapes and particle sizes are 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 in close contact with the surface of the spherical silica particles having a large particle diameter.

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

The spherical silica in the present invention can be industrially advantageously produced by an operation having the above-mentioned features.

That is, a raw material silica powder having a predetermined particle size characteristic and a specific surface area can be manufactured by supplying the raw material silica powder to a flame melting furnace and melting and spheroidizing the powder. This method is known.

Melt spheroidization is a flame caused by the combustion of oxygen-flammable gas,
In many cases, the reaction is performed in an oxygen-propane flame, but the type of gas and the melting method are not particularly limited as long as a flame having a temperature equal to or higher than the melting point of the silica can be obtained.

The silica raw material that can be used in this step is not particularly limited, but is preferably natural or synthetic silica with the highest possible purity.

Natural silica includes purified silica stone, silica sand, quartz and the like.Synthetic silica includes those obtained by hydrolysis of silicon halide, hydrolyzates of organosilicates such as ethyl silicate or neutralization of aqueous alkali silicate solutions. Silica and the like.

In particular, a method for producing high-purity silica obtained based on a neutralization reaction of an aqueous solution of an alkali silicate with a mineral acid has already been successfully developed by the present applicant and can be used as an industrially advantageous silica raw material. For details, see, for example, JP-A-61-48421, JP-A-61-48422,
It is described in JP-A-61-178414, JP-A-62-12608 and the like.

The crushed silica can be prepared by pulverizing spherical silica, but as described above, usually, a granular or massive fused silica obtained by heating and melting or sintering a silica raw material in a melting furnace as desired is appropriately used. It is prepared by crushing with a crusher. In addition, pulverized natural silica can 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 airflow. At this stage, fine crushed silica adheres to the spherical silica surface due to collision between the spherical silica and the crushed silica and generation of static electricity. Next, classification is performed at a classification point of about 5 μm in order to separate spherical silica having crushed silica adhered to the surface and crushed silica not having adhered thereto.

The operation of classification from the adhesion in the high-speed rotating airflow can be performed by a forced vortex type classifier, for example, a turbo classifier (Nissin Engineering), a micron separator (Hosokawa Micron), a Spedd classifier (Seishin Enterprise) ) Etc. can be used.

The amount of crushed silica adhered was the spherical silica before adhesion.
It can be determined by calculation from the BET specific surface area, the specific surface area of the silica after adhesion, and the specific surface area of the crushed silica.

The silica filler according to the present invention thus obtained is suitable as a resin sealing filler by itself, but if necessary, a spherical filler of another specific particle size is added using this as a base material. By adjusting the particle size, fine flowability, burr characteristics, and high-temperature strength characteristics can be balanced. Further, if necessary, the surface can be treated with a silane coupling agent or the like before use.

(Operation)

The silica filler according to the present invention is obtained by physically adhering crushed silica finer than silica to the particle surface of fused spherical silica having specific particle characteristics as a silica filler. By treating the above-mentioned two different silica mixtures with a vortex-type classifier, the silica fillers collide with each other in a high-speed rotating airflow and cause physical adhesion with the generation of static electricity. It can be obtained by separating at the classification point.

EXAMPLES Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples. All parts represent weight.

(1) Preparation of spherical silica A. Synthetic silica having an R50 of 13.0 μm was dispersed in an oxygen propane flame and melted and spheroidized. The obtained fused silica has R50 = 3
It was 3.0 μm and BET 0.45 m ² / g, and it was spherical when confirmed by SEM.

B. Synthetic silica with R50 = 2.0 μm was dispersed in an oxygen propane flame and melted and spheroidized. The obtained fused silica was classified to remove coarse particles, thereby obtaining silica having an R50 of 2.8 μm and a BET of 2.65 m ² / g. It was spherical as confirmed by SEM.

C. R50 = 2.2 μm synthetic silica was dispersed in an oxygen propane flame and melted and spheroidized. The obtained fused silica has R50 = 2.0
μm, BET 23 m ² / g, and confirmed spherical by SEM.

(2) Preparation of crushed silica After melting natural quartz, it was crushed with a ball mill and R50 =
A crushed silica having a particle size of 4.8 μm and a BET of 7.5 m ² / g was obtained.

(3) Preparation of sealing resin composition (4) Evaluation of resin composition After kneading the above-mentioned epoxy resin composition for sealing with a hot roll at 85 to 95 ° C, the fluidity, burr characteristics and high-temperature strength characteristics of the composition were evaluated.

In other words, the fluidity is measured by the transfer molding machine using EMMI 1-
Measure the spiral flow value based on 66.
Evaluation was made by measuring the length of a burr extending immediately before a mold having a slit width of の 50 μm.

The transfer mold conditions were a mold temperature of 170
° C and a resin pressure of 70 kg / cm ² .

For the measurement of high-temperature strength, a test piece (4 mm x 10 mm x 100 mm) for strength side molding molded by a mold was post-cured (180 ° C x 4
hrs) and autograph [JIS K-6911
(Manufactured by Shimadzu Corporation). For the high temperature strength after water absorption, the post-cured test piece
Water was absorbed in a T (120 ° C. × 24 hrs) test, and then the three-point bending strength at 220 ° C. was measured. In addition, in one measurement, the average value was measured using six test pieces.

Example 1 After mixing 800 parts of spherical silica A and 200 parts of crushed silica, the mixture was classified into a classifier [Turbo Classifier TC
-15 N, manufactured by Nisshin Engineering Co., Ltd.] to obtain 960 parts of spherical silica having fine crushed silica adhered thereto.

The classification conditions at this time are: rotor speed 4250RPm, air flow
1.0 m ³ / min and the classification point was 4 μm.

When the particle size and specific surface area of the obtained silica filler were measured, the average particle size (R50) was 29.5 μm and the specific surface area (BET) was 1.36 m ² / g. The adhered amount of crushed silica calculated by BET was 12%. A sealing resin composition was prepared using this silica filler, and the fluidity and the high-temperature strength were measured. The results are shown in Table 1.

Example 2 After 800 parts of spherical silica A and 200 parts of crushed silica were mixed, the mixture was passed through a classifier in the same manner as in Example 1 to obtain 970 parts of spherical silica with spherical silica attached. The classification conditions at this time were a rotor rotation speed of 4000 RPm and an air volume of 1.4 m ³ / min, and the classification point was 5 μm.

When the particle size and specific surface area of the obtained silica were measured, R5
0 = 28.9 μm and BET 1.92 m ² / g, and the adhered amount of crushed silica calculated from BET was 20%. Using this silica filler, a sealing resin composition was prepared, and the fluidity and high-temperature strength were measured. The results are shown in Table 1.

Comparative Example 1 A sealing resin composition was prepared using spherical silica A, and the fluidity and high-temperature strength were measured. The obtained results are shown in Table 1.

From Table 1, it was found that the silica fillers of Examples 1 and 2 had a high temperature strength after water absorption of about 30% higher than that of Comparative Example 1 and were suitable as a base filler when preparing a high-strength material.

Example 3 80 parts of silica obtained according to Example 1 and spherical silica B10
Parts and spherical silica C10 parts were mixed to prepare a silica filler. A sealing resin composition was prepared using this silica filler, and the fluidity, burr characteristics, and high-temperature strength were measured, and the results shown in Table 2 were obtained.

Example 4 80 parts of silica obtained from Example 2 and spherical silica B10
Parts and spherical silica C10 parts were mixed to prepare a silica filler. A sealing resin composition was prepared using this silica filler, and the fluidity, burr characteristics, and high-temperature strength were measured, and the results shown in Table 2 were obtained.

Comparative Example 2 80 parts of spherical silica, 10 parts of B, and 10 parts of C were mixed to prepare a silica filler. A sealing resin composition was prepared using this silica filler, and the fluidity, burr characteristics, 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, 10 parts of B, 10 parts of C and 10 parts of crushed silica without treating with a vortex classifier. A sealing resin composition was prepared using the silica filler, and the fluidity, burr characteristics, and high-temperature strength were measured, and the results shown in Table 2 were obtained.

From the measurement results in Table 2, it was found that Examples 3 and 4 had good balance of fluidity, burr characteristics and strength. In addition, despite the use of the substrate to which the crushed silica was adhered, the fluidity and the elastic modulus were equivalent to those of the all-spherical filler of Comparative Example 2. unacceptable. In the comparative example, the high temperature strength is insufficient,
The high temperature strength after water absorption is particularly low as compared with the examples. Comparative Example 3 in which only crushed silica was mixed had a drawback that the fluidity was slightly low and the high temperature strength was high but the elastic modulus was high.

〔The invention's effect〕

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. When a sealing resin composition is prepared using such a silica filler, the composition has a good balance of fluidity, burr characteristics, and high-temperature strength characteristics, and is particularly a disadvantage of the conventional spherical filler. High temperature strength characteristics can be greatly improved.

Continued on the front page (72) Inventor Yutaka Kinose, 3rd Tenno-mae, Miharu-cho, Tamura-gun, Fukushima Japan Inside the Miharu Plant of Chemical Industry Co., Ltd. (56) References JP-A-1-185373 (JP, A) JP-A-61-257908 (JP, A) JP-A-3-259996 (JP, A) JP-A-2- 158637 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) C09C 1/28 C09C 3/06 C08K 3/36 C08K 9/02 C01B 33/12

Claims (2)

(57) [Claims] Crushed silica finer than the silica particles is physically adhered to the surface of the fused spherical silica having an average particle diameter of 10 to 40 μm, accompanied by mutual collision and generation of static electricity in a high-speed rotating airflow. A silica filler for semiconductor resin encapsulation, comprising: 2. A mixture of fused spherical silica having an average particle size of 10 to 40 μm and crushed silica having an average particle size of 5 μm or less is introduced into a high-speed rotating airflow, and then classified at a classification point of 1 to 10 μm. A method for producing a silica filler for semiconductor resin encapsulation.