JPH0655827B2 - Method for manufacturing epoxy resin tablet for semiconductor encapsulation - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for continuously producing a resin tablet for semiconductor encapsulation, which is high in quality and capable of resin-encapsulating a semiconductor with good moisture resistance, with high productivity.

2. Description of the Related Art Conventional techniques and problems to be solved by the invention In many cases, resin encapsulation of semiconductor elements is usually carried out by transfer molding an epoxy resin composition. The epoxy resin composition used at that time is supplied in the form of tablets, and the tablets are kneaded with a roll and a kneading machine of the epoxy resin composition, cooled, and crushed and then put a predetermined amount of powder obtained in a mold. Although it is made by a compression molding method of pressurizing by pressurization, it has a drawback that the specific gravity is lower than that of a molded product because bubbles are introduced into the tablet at the time of compression molding.

Regarding the specific gravity of the above-mentioned tablets, particularly when a tablet having a specific gravity of 90% or more of the molded product is used, transfer molding efficiency and resin encapsulation obtained are obtained as compared with the case of using a tablet having a specific gravity of less than 90%. It has been confirmed that the moisture resistance life of the semiconductor element is further improved.

Therefore, it has been attempted to increase the molding pressure during tablet production to increase the specific gravity of the tablet to 90% or more, especially about 95% of the molded product. The energy applied to the body changes into heat, and heat is generated due to the friction between the tablet and the mold when the tablet is removed from the mold. For this reason, when tablet production is continued for a long time, the heat of the die causes the resin powder to melt and adhere to the die.If you continue working in this state, the tablet surface rubs, and defective parts such as chips are left behind. There is a disadvantage that it may occur or the tablet may crack. In addition, such a disadvantage is remarkable when a resin having a low viscosity is used.

In order to avoid the above-mentioned inconvenience, it is necessary to frequently interrupt the molding operation of the resin composition to cool the mold and remove the resin composition adhering to the mold surface. The method was poor in workability.

Furthermore, in recent years, a fully automated method called a multi-plunger method has begun to be adopted when a semiconductor device is sealed by a transfer molding method using an epoxy resin composition.
This method uses a transfer molding machine with 5 plungers.
10 plungers are attached, and one plunger fills 2 to 4 cavities. A large number of attached plungers can be lowered at a time, and 10 to 40 cavity cavities can be filled at the same time. .

However, compared to the tablet shape used in the conventional method of molding 250 to 500 cavities with one plunger, which has a diameter of 35 mm or more and a weight of 40 to 500 g,
The tablet used in the multi-plunger system has a diameter of 1
Since the size is 6 mm or less and the weight is 2 to 10 g, which is very small, the resin adhesion to the mold at the time of manufacturing the tablet becomes a further serious problem in this multi-plunger system.
That is, in the case of manufacturing a small tablet, if the tablet is continuously manufactured while the resin remains attached to the mold, the tablet surface is rubbed on the tablet as described above and defects such as chipping occur, and the weight of the obtained tablet is molded. However, there is a drawback in that the amount of resin finally adheres to the upper punch and the lower punch of the mold, and the tablet cannot be molded. Therefore, in order to manufacture small tablets in large quantities, when the weight of the obtained tablets reaches the minimum allowable weight, the molding operation is interrupted, the resin adhered to the upper punch and the lower punch of the mold is removed, and the tablets are re-molded. The process of starting work must be carried out frequently. Therefore, its workability is extremely poor,
In addition, the quality of the obtained tablets varied, and the production efficiency was low.

Therefore, it has been desired to develop a manufacturing method capable of efficiently and continuously manufacturing high-quality epoxy resin tablets for semiconductor encapsulation.

The present invention has been made in view of the above circumstances, has high quality,
An object of the present invention is to provide a manufacturing method which is capable of continuously molding a resin tablet for semiconductor encapsulation capable of resin encapsulating a semiconductor with good moisture resistance and having stable quality, and which has good workability and production efficiency.

Means and Actions for Solving the Problems The inventors of the present invention have conducted extensive studies in order to achieve the above-mentioned object, and as a result, for 100 parts (parts by weight, hereinafter the same) of epoxy resin composition powder, α-olefin-modified silicone, Fluorine-modified silicone, fatty acid-modified silicone and the following formula (14) (However, in the formula, R ⁴ is a monovalent hydrocarbon group having 1 to 6 carbon atoms,
R ⁵ is a monovalent hydrocarbon group having 7 to 21 carbon atoms, X is a hydrogen atom or a fluorine atom, a is an integer of 1 to 4, b is 1, 2
Or 3. ) A silicone-based lubricant selected from the organopolysiloxanes represented by the formula (1) is mixed in a proportion of 0.01 to 0.5 parts to form a tablet, and more preferably a powdered epoxy resin composition. A silicone-based lubricant solution prepared by dissolving a silicone-based solvent in a solvent having a boiling point of 120 ° C. or lower is mixed, and then the solvent is removed, and then the silicone-based lubricant-containing epoxy resin composition powder is compression molded into a tablet shape. In this case, it has been found that a resin tablet for semiconductor encapsulation having a high quality and a specific gravity of 90% or more of the specific gravity of the transfer molded product can be continuously and stably produced with high production efficiency.

That is, since the silicone-based lubricant adheres to the surface of the epoxy resin composition powder mixed with the above-mentioned silicone-based lubricant, the tablet production is performed even when the tablet having the specific gravity of 90% or more of the specific gravity of the molded product is compressed. At times, the resin powder does not easily adhere to the upper punch and the lower punch of the die of the tablet making machine, and the heat generated by pressurization and friction with the die during molding is very small. Therefore, even if a tablet with a high specific gravity is manufactured by continuous operation, there is almost no phenomenon in which the resin powder is melted and adheres to the mold due to the heat generated, and the rate of occurrence of scratches, chips, cracks, etc. on the tablet surface during manufacturing. Very few. Therefore, according to the present invention, a high specific gravity and high quality epoxy resin tablet for semiconductor encapsulation capable of encapsulating a semiconductor with good moisture resistance, variation in specific gravity, size and weight,
Further, it is possible to perform continuous molding stably by a simple operation without generation of chips and cracks.

Therefore, the present invention is based on 100 parts by weight of the epoxy resin composition powder, α-olefin modified silicone, fluorine modified silicone, fatty acid modified silicone and the following formula (14) (However, in the formula, R ⁴ is a monovalent hydrocarbon group having 1 to 6 carbon atoms,
R ⁵ is a monovalent hydrocarbon group having 7 to 21 carbon atoms, X is a hydrogen atom or a fluorine atom, a is an integer of 1 to 4, b is 1, 2
Or 3. ) A silicone-based lubricant selected from organopolysiloxanes represented by the formula (1) is mixed in a proportion of 0.01 to 0.5 parts by weight, and the mixture is compression-molded into a tablet shape. .

Hereinafter, the present invention will be described in more detail.

The epoxy resin composition powder used for the epoxy resin tablet for semiconductor encapsulation of the present invention is variously selected, but the main component is an epoxy resin and a curing agent thereof, and more preferably a filler and other required components. It includes.

In this case, as the epoxy resin, an epoxy resin having two or more epoxy groups in one molecule, for example, cresol novolac type epoxy resin, phenol novolac type epoxy resin, bisphenol A type epoxy resin, o-allylphenol novolac type epoxy resin One or more epoxy resin compositions containing the above-mentioned brominated epoxy resins, epoxy resin modified with organopolysiloxane, and heterocyclic epoxy resin such as triglycidyl isocyanate can be used. In addition, it is preferable that the content of hydrolyzable chlorine ions in these epoxy resins is as low as possible, and it is preferable that the content of the epoxy resin is 0.1% by weight or less.

Further, a phenol resin is suitable as the curing agent, and as the phenol resin, a phenol novolac resin, a cresol novolac resin, a tert-butylphenol novolac resin, a nonylphenol novolac resin, a resole type phenol resin, a bisphenol A type novolac resin and an organopolysiloxane are used. Examples include modified phenol novolac resins. Further, as the filler, silica, alumina, talc, mica, clay, kaolin, glass fiber, glass beads, asbestos, baryta, zinc white, antimony trioxide, calcium carbonate, aluminum hydroxide, calcium hydroxide titanium, silicon carbide. , Inorganic fillers such as iron oxide, and other components include imidazoles, imidazoles such as 2-methylimidazole, curing accelerators such as amine compounds such as triethylamine and diethylenetriamine, release agents, organic rubber-based agents, and the like. Silicone-based flexibility-imparting agents, pigments such as carbon black, cobalt blue, red iron oxide, antimony oxide, flame retardants such as halogen compounds, surface treatment agents (γ-glycidoxypropyltrimethoxysilane, etc.), epoxysilanes , Vinylsilane, boron compounds, alkyl titane Coupling agents and the like, and the like anti-aging agents.

In this case, the amount of the curing agent used is usually 20 to 40 parts based on 100 parts of the epoxy resin, and the filler is 200 to 700 parts based on 100 parts of the total amount of the epoxy resin and the curing agent. Is preferably 1 to 10 parts per 100 parts of the total amount of the epoxy resin and the curing agent. Specifically as such an epoxy resin composition, K
MC-140 (manufactured by Shin-Etsu Chemical Co., Ltd.) is preferably used.

The above-mentioned epoxy resin composition is used as a powder, and its particle size and the like are not particularly limited, but the particle size is 74 to 8
It is preferable to use powder obtained by containing particles of 40 μm in an amount of 95% by weight or more of the whole and pulverizing so as to have an average particle size of 250 to 400 μm.

In the present invention, the silicone-based lubricant to be added to the epoxy resin composition powder, C _n H _{2n + 1} - group, C _n H
A silicone compound containing a _{2n + 1} COO-group, a fluorine atom or the like, for example, one or more of α-olefin modified silicone, fluorine modified silicone and fatty acid modified silicone is used.

Here, as the α-olefin modified silicone, any one can be used as long as it is a silicone compound containing an olefin group in the molecule, but as a typical one, the following structural formula (1) (Wherein R is a monovalent hydrocarbon group such as a substituted or unsubstituted alkyl group having 6 or less carbon atoms, n is a number of 7 or more,
Each of X and Y is a number of 1 or more. ) The silicone compound shown by these is mentioned. In the present invention, it is preferable to use a silicone compound having a large number of n among the silicone compounds represented by the above formula (1) since the resin composition is less attached to the mold. Specifically, the following formula (1a) What is shown by can be used conveniently.

Further, as the fluorine-modified silicone, any organopolysiloxane having at least one fluorine atom in one molecule may be used, and various fluorine-atom-containing organopolysiloxanes may be used. It is preferable to use an organopolysiloxane having at least one atom-containing perfluoroalkyl group in the molecule.

Examples of the perfluoroalkyl group in the fluorine atom-containing organopolysiloxane molecule include CF ₃ CF ₂ CF ₂ , CF ₃ (CF ₂ ) _n CH ₂ CH ₂ −, CF ₃ (CF ₂ ) _n CH ₂ CH ₂ S −, CF ₃ (CF ₂ ) _n CF ₂ CF ₂ COO-, (Where n = 3 to 30), include _{C 7 F 15 CH 2 CH 2} O- and the like.
Further, the organopolysiloxane having a perfluoroalkyl group may be any of linear, branched, and three-dimensional structures, and R ¹ ₃ SiO _0.5 unit, R ² ₂ SiO unit, R ³ ₁ SiO _1.5
Unit, SiO ₂ unit (wherein R ¹ , R ² and R ³ are each a monovalent organic group or an organic group having at least one fluorine atom)
The organic group is a methyl group,
Alkyl group such as ethyl group, propyl group, butyl group, alkenyl group such as vinyl group, allyl group, aryl group such as phenyl group, tolyl group, cycloalkyl group such as cyclohexyl group, bonded to carbon atom of these groups A group in which one part of a hydrogen atom is replaced with a halogen atom, a cyano group, or the like,
Further, it may be selected from functional groups such as alkoxy groups such as methoxy group and ethoxy group, amino group, epoxy group, thiol group, hydroxyl group, carboxyl group and the like. The viscosity of this organopolysiloxane is not particularly limited, and it may be a low-viscosity, high-viscosity liquid substance or a solid substance having a softening point.

Specific examples of such an organopolysiloxane include those represented by the following formulas (2) to (10).

(I) Linear polysiloxane (III) Three-dimensional structure polysiloxane (In the above formula, R represents a hydrogen atom or an alkyl group, and R _f represents a perfluoroalkyl group.) Further, the fatty acid-modified silicone has C _n H in one molecule.
Organopolysiloxanes having at least one _{2n + 1} COO- group are used, but in addition, C _n H _{2n + 1} COO is included in one molecule.
C _m H _2m - can also be used organopolysiloxane containing an organic group having an ester bond such groups. The _{n of the} C _n H _{2n + 1} COO-group and the C _n H _{2n + 1} COOC _m H _2m -group are
The values of m and m are preferably integers of 5 or more, and if smaller than 5, it is difficult to improve the adhesion of the resin composition to the mold, and the object of the present invention may not be achieved in some cases.

Here, as the fatty acid-modified silicone, compounds represented by the following formulas (11) to (13) are specifically exemplified.

Furthermore, in the present invention, as a silicone-based lubricant, 1
An organopolysiloxane having both a fluorine atom and a C _n H _{2n + 1} COO- group in the molecule, for example, the following structural formula (14) (However, in the formula, R ⁴ is a monovalent hydrocarbon group having 1 to 6 carbon atoms,
R ⁵ is a monovalent hydrocarbon group having 7 to 21 carbon atoms, X is a hydrogen atom or a fluorine atom, a is an integer of 1 to 4, b is 1,
2 or 3. It is also possible to use an organopolysiloxane represented by Specific examples of the organopolysiloxane of the formula (14) include the following compounds. (Here, Me represents a methyl group).

F (CF ₂ CF ₂ ) ₄ CH ₂ CH ₂ Si (Me) (OCOC ₁₇ H ₃₃ ) ₂ … (14a) F (CF ₂ CF ₂ ) ₄ CH ₂ CH ₂ Si (Me) (OCOC ₇ H ₁₅ ) ₂ … (14b) F (CF ₂ CF ₂ ) ₄ CH ₂ CH ₂ Si (Me) (OCOC ₁₃ H ₂₇ ) ₂ … (14c) F (CF ₂ CF ₂ ) ₄ CH ₂ CH ₂ Si (OCOC ₂₁ H ₄₃ ) ₃ … (14d) F (CF ₂ CF ₂ ) ₃ CH ₂ CH ₂ Si (Me) (OCOC ₇ H ₁₅ ) ₂ … (14e) F (CF ₂ CF ₂ ) ₃ CH ₂ CH ₂ Si (OCOC ₁₇ H ₃₁ ) ₃ … (14f) F (CF ₂ CF ₂ ) ₂ CH ₂ CH ₂ Si (Me) (OCOC ₇ H ₁₅ ) ₂ … (14g) F (CF ₂ CF ₂ ) ₂ CH ₂ CH ₂ Si (Me) ( OCOC ₉ H ₁₉ ) ₂ … (14h) F (CF ₂ CF ₂ ) ₂ CH ₂ CH ₂ Si (OCOC ₁₃ H ₂₇ ) ₃ … (14i) F (CF ₂ CF ₂ ) ₂ CH ₂ CH ₂ Si (Me) (OCOC ₁₇ H ₃₃ ) ₂ … (14j) CF ₃ CF ₂ CH ₂ CH ₂ Si (Me) (OCOC ₇ H ₁₅ ) ₂ … (14k) CF ₃ CF ₂ CH ₂ CH ₂ Si (OCOC ₁₇ H ₃₅ ) ₃ (14l) The silicone type lubricant used in the present invention can be used alone or in combination of two or more of the above-mentioned ones. Ionic Na, so as not to impair the properties,
It is desirable to minimize the content of Cl, and it is preferable that the content of each of Na ion and Cl ion is 10 ppm or less.

Furthermore, the addition amount of the silicone lubricant is 0.01 to 0.5 part, preferably 0.015 to 0.2 part, relative to 100 parts of the epoxy resin composition powder. If the amount of the silicone lubricant added is less than 0.01 part, the phenomenon of resin adhesion to the mold occurs early, and if it is more than 0.5 part, the adhesive force between the resin and the semiconductor device decreases. The moisture resistance becomes poor and the object of the present invention cannot be achieved.

The epoxy resin tablet for semiconductor encapsulation of the present invention uses a silicone-based lubricant-containing epoxy resin composition obtained by mixing the epoxy resin composition with a specific amount of a silicone-based lubricant. The following method is preferably adopted as the manufacturing method.

That is, a silicone-based lubricant is previously dissolved in a solvent having a boiling point of 120 ° C. or less to prepare a silicone solution, and the silicone solution is mixed with a powdery pulverized epoxy resin composition, and then the solvent is removed to obtain a silicone obtained. This is a method of forming a powder of a lubricant-containing epoxy resin composition into a tablet shape.

In this case, the silicone-based lubricant is used as a silicone-based lubricant solution by dissolving it in a solvent so that it is mixed with an epoxy resin composition powder (hereinafter referred to as EMC) with good dispersibility, and further, as this solvent, If the solvent remains in the resin composition during tablet molding, voids may be generated. Therefore, after the silicone lubricant is thoroughly mixed with EMC, it is quickly scattered from the inside of the EMC at low temperature and removed outside the system. As the solvent to be obtained, a solvent having a boiling point of 120 ° C. or lower is preferably used.

Examples of the solvent having a boiling point of 120 ° C. or lower include toluene, acetyl, methanol, low-boiling point dimethyl silicone, water, etc. Among them, the solubility of the silicone lubricant is good, and the boiling point and vapor pressure are low. From the following formula (15) The silicone represented by can be preferably used.

Note that this solvent is ionic Cl or contained in the solvent so as not to impair the characteristics of the semiconductor device sealed with the resin composition.
It is preferable that the amount of Na is as small as possible, and it is particularly preferable that the contents of Na ion and Cl ion are each 10 ppm or less.

When the silicone lubricant is dissolved in the above solvent, it is desirable that the viscosity of the solution is 500 poise or less at room temperature, especially 10 poise or less. If the viscosity of the silicone lubricant used is lower than the above value,
Since it can be sufficiently dispersed in EMC without being dissolved in a solvent, it can be used as it is.

The method of mixing and dispersing the silicone lubricant solution in EMC is not particularly limited, but spraying the silicone lubricant solution while stirring the EMC is effective.

Further, the EMC mixed with the silicone-based lubricant solution is placed in a hermetically sealed container and left at room temperature for about 5 to 48 hours.
It is desirable to remove the solvent after infiltrating the silicone lubricant into the mixture and mixing them uniformly. Here, the solvent is easily scattered by leaving it naturally, but it can be removed under reduced pressure by using a vacuum pump. The conditions for removing the solvent are not particularly limited, but if the solvent is removed at a temperature of 40 ° C. or higher, the EMCs adhere to each other to form a lump.
Since the viscosity of the solvent increases, the temperature should be below 40 ℃, especially 25
It is preferable to perform the treatment at a low temperature of ℃ or less.

The epoxy resin composition for semiconductor encapsulation obtained by such a method can be molded into a tablet shape by a usual method using a tablet manufacturing machine to obtain tablets having various shapes. In particular, in the present invention, since the resin composition hardly adheres to the mold of the tablet manufacturing machine, it is possible to continuously mold even a tablet having a high specific gravity or a small tablet used in the multi-plunger system.

As described above, according to the method for producing an epoxy resin tablet for semiconductor encapsulation of the present invention, the resin powder adheres to the upper punch and the lower punch of the die of the tablet making machine at the time of production, or at the time of molding. Since heat is hardly generated by the pressurization or friction with the mold, the tablet surface is not scratched, chipped or cracked. Therefore, a resin tablet having high specific gravity and high quality can be continuously molded by a simple operation without interrupting the work on the way. Moreover,
The epoxy resin tablet for semiconductor encapsulation obtained in the present invention is of high quality as described above, has good adhesiveness to the semiconductor, and is capable of encapsulating the semiconductor with good moisture resistance.

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

[Example 1, Comparative Example 1] α-olefin-modified silicone (Cl
Ion 5ppm, Na ion 1ppm) 1kg to the solvent represented by the above formula (15) (boiling point 100 ° C, Cl ion 5ppm, Na ion 1p)
pm) dissolved in 5 kg.

Next, 1000 kg of an epoxy resin composition for semiconductor encapsulation (KMC-140, manufactured by Shin-Etsu Chemical Co., Ltd.) containing 90% of particles having a particle diameter of 1000 to 74 μm and crushed to an average particle diameter of 310 μm was ribbon-shaped. The mixture was placed in a blender, 6 kg of the above α-olefin-modified silicone solution was sprayed with stirring, and then the mixture was further stirred for 1 hour. Then, the resin composition was taken out in a sealed container and left in an atmosphere of 20 ° C. for 2 days.
After standing, the solvent of the formula (15) contained in the obtained powder of the resin composition was removed by using a vacuum pump.

Using this powder, 10,000 tablets each having a diameter of 13 mm, a weight of 2.5 g and a tablet specific gravity of 1.73 were continuously molded by a tablet manufacturing machine (manufactured by Niei Seiko Co., Ltd.).

For comparison, the same epoxy resin composition for semiconductor encapsulation as described above was molded as it was in the same manner as above using a tablet making machine.

Regarding the obtained tablets, the continuous moldability by a tablet making machine, the appearance and the specific gravity, height, and weight were measured to examine the variations.

The results are shown in Table 1.

From the results shown in Table 1, when the epoxy resin composition containing the silicone lubricant according to the present invention is used, tablets can be continuously molded, and the specific gravity and height of the tablets to be obtained,
It was confirmed that there was little variation in weight and the appearance was also good.

[Examples 2 to 5, Comparative Examples 2 and 3] Tablets similar to those in Example 1 were produced except that the amount of α-olefin-modified silicone was set to the amount shown in Table 2.

Next, using this tablet, it was designed to study the corrosion of the Al metal electrode by the transfer molding method.
The pin IC was molded.

A pressure cooker test was carried out in which the obtained molded product was allowed to stand in steam at 2 atm and 120 ° C., and the occurrence rate of wire breakage caused by aluminum corrosion after 1000 hours was measured.

The results are shown in Table 2.

From the results shown in Table 2, when the blending amount of the α-olefin modified silicone is small (Comparative Example 2), the phenomenon of adhesion to the mold occurs early, and when the blending amount is large (Comparative Example 3), the resin is used. The adhesive strength between the semiconductor device and the semiconductor device was poor, and the moisture resistance was lowered. On the other hand, the tablet formed by using the resin composition containing 0.01 to 0.5 part of the α-olefin-modified silicone according to the present invention has good continuous moldability and adhesiveness with a semiconductor device. Was found to have good moisture resistance.

[Examples 6 to 8 and Comparative Examples 4 to 6] A third lubricant was used instead of the α-olefin-modified silicone as a lubricant.
Tablets were produced in the same manner as in Example 1 except that the silicone compounds or internal release agents shown in the table were used, and the continuous moldability and moisture resistance of the tablets were examined.

Since the internal release agent was not dissolved in the solvent, 320
It was pulverized more finely than the mesh and mixed.

The results are shown in Table 3.

From the results of Table 3, when the conventional internal mold release agent is blended (Comparative Examples 4 to 6), it is difficult to continuously mold the tablet, but the resin composition blended with the silicone lubricant according to the present invention is used. When (Examples 6 to 8) were used, the continuous moldability and moisture resistance of the tablet were good.

Examples 9 to 11 Fourth Solvent for Solving α-Olefin Modified Silicone
Tablets were produced in the same manner as in Example 1 using the solvents shown in the table, and the continuous moldability of the tablets was evaluated.

Further, 1000 14-pin ICs were molded with the obtained tablets, and the pinhole generation rate on the surface was measured.

The results are also shown in Table 4.

From the results shown in Table 4, it was found that according to the present invention, tablets could be continuously molded and the pinhole generation rate was low.
As a solvent, dimethylformamide (boiling point 153
℃) is used, the continuous moldability of the tablet is 600
The pinhole generation rate is 5% per piece, and when xylene (boiling point 142 ° C) is used, the tablet continuous moldability is 600 pieces, the pinhole generation rate is 6%, and the boiling point is higher than 120 ° C. It was found that the use of the solvent tends to deteriorate the continuous moldability of the tablet and increase the pinhole generation rate.

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Claims (3)

[Claims] 1. An α-olefin modified silicone, a fluorine modified silicone, a fatty acid modified silicone and the following formula (14) with respect to 100 parts by weight of an epoxy resin composition powder. (However, in the formula, R ⁴ is a monovalent hydrocarbon group having 1 to 6 carbon atoms,
R ⁵ is a monovalent hydrocarbon group having 7 to 21 carbon atoms, X is a hydrogen atom or a fluorine atom, a is an integer of 1 to 4, b is 1, 2
Or 3. ) A silicone-based lubricant selected from the organopolysiloxanes represented by the formula (1) is mixed in a proportion of 0.01 to 0.5 parts by weight, and the mixture is compression-molded into a tablet shape. 2. The method according to claim 1, wherein the silicone-based lubricant is previously dissolved in a solvent having a boiling point of 120 ° C. or less and mixed as a silicone solution. 3. The method according to claim 2, wherein the solvent having a boiling point of 120 ° C. or lower is silicone.