JPH02145416A - Fused spherical silica and sealing resin composition using the same - Google Patents

Abstract

PURPOSE:To improve suppressing effects on fluidity and flash by containing specific fused spherical silica in the sealing resin composition. CONSTITUTION:Silica, having <=5ppm electrically conductive impurity content, <=1ppb alpha-radioactive impurity content, 10-30mum average particle diameter and containing 8-30wt.% fine part having <=3mum particle diameter, 5-30wt.% part of coarse particle diameter having <=48mum particle diameter and 0.65-1.10 tilting angle in a Rosin-Rammler chart in a particle size distribution of 8mum and 64mum particle diameter is fused and sphered to afford a silica filler consisting of fused spherical silica. The resultant silica filler in an amount of 60-85wt.% is then blended with a resin (e.g. epoxy resin), a curing agent (e.g. phenolic resin), a curing accelerator (e.g. BF), etc., to afford a sealing resin composition.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to fused spherical silica and a sealing resin composition using the same.

More specifically, fused spherical silica with specific particle size characteristics and specific surface area suitable as a filler in resin encapsulation of semiconductors, and a encapsulating resin with excellent fluidity and Paris properties when used as a filler. A composition is provided.

[Conventional technology]

Semiconductor resin encapsulation is performed using a resin composition filled with a resin, typically epoxy resin, and a large amount of filler, especially silica, and many patents have already been published regarding this relationship. has been done.

Conventionally, pulverized fused spherical silica has been used as a filler for 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. For improvement, fused spherical silica has become indispensable as a filler instead 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 particle diameter l~
The use of 60 μm fused spherical silica is indicated.

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). Publication No.).

[Problem to be solved by the invention]

2. Description of the Related Art In semiconductors such as DRAMs, which are becoming increasingly integrated, countermeasures against thermal stress have become a serious problem as the degree of integration increases. Thermal stress is said to be controlled by the difference in thermal expansion coefficient between the encapsulant resin composition and the chip and the elastic modulus of the composition. In particular, the difference in thermal expansion coefficient between the composition and the chip becomes smaller as the content of silica filler in the composition increases, resulting in a sealing material having thermal stress resistance.

Increasing the silica content in the composition cannot be achieved without increasing the fluidity of the composition. Crushed silica, which has been mainly used in the past, has poor fluidity, so there is a limit to its content in the composition, and in order to fill more silica, spherical silica must be used instead of crushed silica. Must be. However, a problem when using spherical silica is that so-called flaking tends to occur during transfer molding of the composition.

Generally, pulverized silica has poor fluidity of resin compositions, but excellent pulverizing properties, while unidirectional silica has the opposite tendency.

Therefore, in many cases, as described above, both types of silica are appropriately blended, and resin sealing is performed using a blending system that sacrifices fluidity.

In view of the above problems, the present inventors conducted extensive research on the characteristics of fused spherical silica, and found that the particle size characteristic frame of fused spherical silica and its specific surface area, which influences the degree of melting, are important for the characteristics of resin fillers. The present invention was completed after discovering that there is a relationship.

That is, an object of the present invention is to provide an excellent fused spherical silica that takes advantage of the characteristics of spherical silica having excellent fluidity as a filler in a resin composition and also has an effect of suppressing flaking during molding.

[Means to solve the problem]

That is, in the present invention, the average particle diameter of fused spherical silica is 10
In the range of 30j1m to 30j1m, the fine part of 3 or less is 8 to 30wt%, and the coarse part of 48μ or more is 5 to 30w.
t%, and the inclination angle of the rosin-Rammler diagram in the particle size distribution of 8/11 and 64IItm is in the range of 0.65 to 1.10, and the BET specific surface area is 3 to 15 nf/g. It relates to characteristic fused spherical silica.

Still another invention is a resin composition for semiconductor encapsulation containing fused silica particles as a filler, characterized in that the resin composition contains 60 to 85 wt% of the fine fused spherical silica. Pertaining to things.

The present invention will be explained in detail below.

The fused spherical silica according to the present invention is characterized in that it is a silica particle having the above particle size characteristics and specific surface area.

That is, the basic particle size characteristic of the fused spherical silica in the present invention is that the average particle size must be in the range of 10 to 3 oIM.

The reason for this is that when used as a sealing filler, when the average particle size is less than 10, the fluidity of the resin composition decreases.
On the other hand, if the average particle diameter exceeds 30 IIm, there will be a large number of coarse particles, and the fluidity will not only be reduced, but also a large amount of paris will be produced, and anything outside this range is basically unsuitable.

However, fused silica particles having such an average particle size are
Fine parts of 3 μm or less are 8 to 30 wt% and 481
It contains one or more coarse particles in the range of 5 to 30 wt%, and in particular, the slope angle (tan θ) of the Rosin-Rammler diagram (RR3) over the particle size range from 8μI to 64- is 0. It must have particle size characteristics ranging from .65 to 1.10.

The reason for this is that although the fine portions have the effect of suppressing the occurrence of paris, if it is less than 8 wt%, the result is insufficient, and if it exceeds 30-1%, the fluidity decreases.

On the other hand, although the coarse grain portion is necessary for improving fluidity, if it is less than 5wt%, its effect is insufficient and it is not possible to prevent pars from occurring from gaps of 30I1m or more, and if it exceeds 30w1%. This also reduces liquidity.

Furthermore, if the angle of inclination deviates from the above range, the fluidity will decrease and high filling cannot be expected.

The above particle size characteristics of the fused spherical silica according to the present invention are all values based on a particle size distribution measurement method using a laser scattering light method, and examples of measurement models include SK Laser (Seishin Enterprise ■) and Cirrus Laser (Cirrus Laser). company)
etc.

Furthermore, fused spherical silica with such particle size characteristics is BE
T specific surface area is 3 to 15nf/g, preferably 5 to 10n
It must be in the f/g range.

Similar to the particle size characteristics, the specific surface area of particles is also important as a factor in the fluidity and Paris properties of the resin composition. It is not possible to obtain something that is both excellent and suppresses Paris.

As described above, although the flow characteristics and the Paris characteristics of resin compositions for semiconductor encapsulation generally tend to contradict each other, in resin compositions that are increasingly required to be highly filled with silica filler, the particle characteristics of silica filler are important. Its influence is both large and very subtle.

For example, commercially available fine silica produced by flame hydrolysis, such as Aerosil, has a poor anti-fog effect, and when the amount used as a filler increases, the fluidity is extremely reduced.

In addition, silica powder, so-called white carbon, used in the normal wet method has an effect of preventing pars, but reduces fluidity.

Furthermore, fine spherical silica based on the hydrolysis of organosilicon compounds such as methyl silicate esters similarly do not have an anti-fog effect, although fluidity is not impaired.

The fused spherical silica according to the present invention was found based on numerous experiments, and if it does not have this characteristic, when used as a filler, it simultaneously improves both the fluidity and Paris properties of the resin composition. It cannot be improved.

Furthermore, the fused spherical silica according to the present invention is of high purity, in particular, conductive impurities such as Na and CI are 5 pI) or less, and α-radioactive impurities such as U and Th are 1 pI, respectively.
PB or less is suitable as the encapsulant filler.

It should be noted that whether or not the fused silica particles are spherical can be confirmed on the package using an electron microscope, and the silica particles according to the present invention are all in a true spherical or substantially spherical particle state. It is recognized that

Such fused spherical silica according to the present invention can be industrially advantageously produced by the following method.

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.

That is, molten spheroidization is carried out using a flame caused by the combustion of an oxygen-combustible gas, in most cases an oxygen-propane flame, but if a flame with a temperature above the melting point of the silica can be obtained, the type of gas, melting temperature, etc. The 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.

In melt processing, in order to achieve molten spheroidization with the desired particle size characteristics and specific surface area, it is of course necessary to set the particle characteristics of the raw material, but it is also necessary to set the particle characteristics of the raw material, but the melting conditions, especially the amount of raw silica supplied, the flame It changes slightly depending on the setting of the formation conditions (ratio and amount of # element - gas).

Therefore, it is necessary to obtain fused spherical silica having desired particle characteristics by appropriately setting the particle size according to the characteristics of the melting furnace equipment.

As mentioned above, if the fused spherical silica according to the present invention cannot be obtained at once due to predetermined setting conditions, it can be made into particles having the above-mentioned characteristics by classification or mixing with other grades of fused spherical silica. Needless to say, preparation is necessary.

Next, in the sealing resin composition according to the present invention, the fused spherical silica is added to the resin composition as a silica filler.
An important feature is that the content is 35 wt%.

Such a resin composition has excellent fluidity and Paris properties, and is suitable as a sealing material that can follow the trend of highly integrated semiconductors.

In the resin composition for semiconductor encapsulation, epoxy resins such as bisphenol A epoxy resin, phenol novolak epoxy resin, cresol novolac epoxy resin, alicyclic epoxy resin, and heterocyclic epoxy resin are used. .

Examples of curing agents include phenol resins, acid anhydrides such as phthalic anhydride, maleic anhydride, and tetrahydrophthalic anhydride, and curing accelerators include commonly used various amines, boron fluoride, onium salts, and imidazole compounds. Can be mentioned.

In addition, in the resin composition according to the present invention, a phosphorus-based or bromine-based organic flame retardant, an inorganic flame retardant such as antimony trioxide, a pigment, a surface treatment agent such as a silane coupling agent, a mold release agent, etc. , antioxidants, etc. can be added.

[For production]

According to the present invention, specific particle size characteristics with an average particle diameter in the range of 10 to 30 μm and a BET specific surface area of 3 to 15 μm can be obtained.
A fused spherical silica having particle characteristics of m2/g is provided.

If 60 to 85 wt % of such silica is blended into the resin composition as a filler in the resin composition for semiconductor encapsulation, the resin composition can be used as a good encapsulation material with excellent fluidity and Paris properties.

〔Example〕

Hereinafter, the present invention will be explained in more detail by giving Examples and Comparative Examples.

Examples 1 to 4, Comparative Examples 1 to 2 (1) Preparation of fused spherical silica Various fused spherical silicas were obtained by the manufacturing method shown in Table 1. Note that the particle sizes in Table 1 are average particle sizes determined by a particle size distribution measurement method using a laser scattering light method, and confirmed by electron microscopy observation of melt spheroidization.

In addition, NctAO is a granular silica gel (U: 0.04 ppb, T h:
0.20 ppb.

Na: 0.38 ppm, Fe: 0.3
8 ppm, water content 711 t%) is appropriately crushed and classified to prepare raw material silica with a predetermined average particle size. It uses silica.

Table 1 When the particle characteristics of each of the fused spherical silicas obtained above were measured, the results shown in Table 2 were obtained.

(2) Preparation of silica filler The various fused spherical silicas obtained above were appropriately selected and blended to prepare various silica fillers.

Table 3 shows the particle characteristics of each silica filler.

(3) Preparation of resin composition for sealing (3-1) Composition of the composition, that is, fluidity is determined by EM M using a transfer molding machine.
The spiral flow value based on I 1-66 was measured, and the parry property was evaluated by measuring the paris length extending just before the mold with the slit width adjusted from 5 to 5071111.

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

The evaluation results are shown in Table 3.

Silica filler...75wt% Note (1) Epicron N665, Dainippon Ink ■ Note (
2) Barcam TD2131, manufactured by Dainippon Ink (3)
) Manufactured by Hoechst (3-2) Preparation and evaluation of resin composition After kneading the above epoxy resin composition for sealing with a heated roll at 85 to 95°C, evaluate the fluidity and Paris properties of the composition. did.

From the results in Table 3, in Comparative Example 1, the silica filler with a small number of particles of 3- or less was found to have insufficient fluidity and generation of paris, and in Comparative Example 2, 50 ptn paris was found due to the lack of content of 414 or more. In contrast, all the products of the present invention exhibited good characteristics.

Examples 5 to 7, Comparative Examples 3 to 5 Four types of fused spherical silica (A-5, A-2,
B-30 and B-15) were blended in predetermined amounts to prepare silica fillers. Its formulation and physical properties are shown in Table 4.

Next, this was blended with the same epoxy resin composition as in Example 1 to obtain a sealing resin composition, and the fluidity and Paris properties of this composition were measured under exactly the same operations and conditions. The results shown in Table 4 were obtained.

From the results in Table 4, Comparative Example 3 is due to the occurrence of flaking and lack of fluidity due to the content of 3n or less and insufficient specific surface area, while Comparative Example 4 is RRS (15 due to too small bevel angle and 311111 or less). Insufficient fluidity due to excessive content; in Comparative Example 5, insufficient fluidity due to small RR3 inclination angle and small average particle size; 441
Occurrence of 50 degrees of paris was observed due to the low content of rm or higher. In contrast, it can be seen that in this example, a sealing resin composition with high fluidity and excellent Paris properties was obtained.

〔Effect of the invention〕

When a resin composition for semiconductor encapsulation is made using the silica filler having the particle size structure according to the present invention, the fluidity is 1.5 to 2.
．． A product twice as good as that of crushed silica filler is obtained, and the Paris properties are equivalent to those of crushed silica filler.

The entire portion of the filler in the resin composition can be composed of spherical silica, thereby making it possible to significantly increase the silica filling rate in the compound. Therefore, as a heat-resistant stress-resistant sealing resin composition, it can become a sealing material that can be used for VVLS I.

Claims (1)

[Claims] 1. The average particle diameter of the fused spherical silica is in the range of 10 to 30 μm, and the fine particles of 3 μm or less are 8 to 30 wt%.
, 5 to 30 wt% of coarse particles of 48 μm or more, and 8 μm
The slope angle of the Rosin-Rammler diagram in the particle size distribution of m and 64 μm is in the range of 0.65 to 1.10, and B
A fused spherical silica characterized by having particle characteristics with an ET specific surface area of 3 to 15 m^2/g. 2. A sealing resin composition containing 60 to 85 wt% of the fused spherical silica according to claim 1 as a silica filler.