JPH09227241A - Releasing sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prepare a releasing sheet suitable for use at the time of dewaxing an AlN green sheet and capable of imparting satisfactory releasability to the sheet after dewaxing by blending BN powder with a specified resin. SOLUTION: This releasing sheet is formed preferably in 1-200μm thickness by blending 100 pts.wt. acrylic resin with 1-30 pts.wt. BN powder. The acrylic resin may be any of only PMMA and a copolymer of PMMA with styrene, DMA, etc. Ordinary additives may be added to the acrylic resin, if necessary. The pref. average particle diameter of the BN powder is preferably 0.1-30μm and the pref. purity is >=95wt.%. The BN powder preferably has a well- crystallized state and a platy shape.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a release sheet which can be preferably used when degreasing an aluminum nitride green sheet.

[0002]

2. Description of the Related Art Conventionally, aluminum nitride (hereinafter referred to as AlN) has excellent thermal conductivity, and its thermal expansion coefficient is similar to that of a silicon wafer for semiconductors. Used as a heat dissipation substrate for semiconductors. This AlN substrate is usually
1N powder, Y ₂ O ₃ , sintering aid powder such as CaO, and a binder for molding are dispersed and mixed in an organic solvent, and then a green sheet is obtained by performing sheet forming with a calender roll, doctor blade, etc., and further drying. It is manufactured through the steps of degreasing and baking. Among these steps, during degreasing,
It is necessary to stack the green sheets via a release agent to prevent the adhesion between the sheets. Boron nitride powder, which is chemically stable even at high temperature, is useful as the release agent, but the boron nitride powder alone has no adhesive force and is difficult to uniformly apply to the surface of the green sheet. Therefore,
Conventionally, boron nitride powder is dispersed in a solvent to form a suspension, and the suspension is applied to the surface of the green sheet by spraying or the like and dried. However, this method has a problem that it takes a lot of time and labor for the work.

Therefore, the present inventors have filed Japanese Patent Application No. 7-276.
No. 094, dimethylsiloxane trimer (hereinafter,
Proposed a release plate made of two components D ₃ hereinafter) and boron nitride powder, when stacking the AlN green sheet, by laminating interposed the release plate between the sheet, the degreasing furnace The preparation work has been simplified and the workability has been improved.

However, since D ₃ is a brittle material, it is difficult to finish it into a thin plate shape, and a thickness of at least about 1 mm is required. Therefore, when a mold release plate is sandwiched between green sheets in a degreasing furnace, the number of laminated green sheets is limited, which may cause a decrease in productivity. In some cases, degreasing is performed by punching a strip-shaped green sheet into a final shape with a large die-cutting tooth before degreasing.
Sintering is desired, but since D ₃ is hard and brittle, there is a problem in that it cannot be punched by the large die-cutting teeth if a release plate is interposed between the green sheets.

Therefore, in order to solve these problems,
It is desired to develop a mold release composition containing a thin sheet-like boron nitride powder having elasticity that can be punched out by a bisecting tooth. Further, the composition forming this sheet is required to volatilize components other than boron nitride during degreasing, and to eliminate the risk of ignition due to the volatiles and to have no adverse effect on the environment or the human body.

The present invention meets the above-mentioned demands, and uses AlN
An object of the present invention is to provide a release sheet which is suitably used during degreasing of a green sheet and which can impart good release properties to the degreased sheet.

[0007]

Means for Solving the Problems and Modes for Carrying Out the Invention As a result of intensive studies aimed at achieving the above-mentioned objects, the present inventors have found that acrylic resin is used as a main material and 100 parts by weight of the acrylic resin is added. On the other hand, it was found that it is effective to blend 1 to 30 parts by weight of boron nitride powder to obtain a release sheet.

That is, the sheet obtained by blending the acrylic resin with the boron nitride powder in the above blending amount has elasticity and can be punched with a large die-cutting tooth, and at the time of degreasing the AlN green sheet, the acrylic resin is Since it is depolymerizable and has a slow depolymerization rate, it does not generate a large amount of combustible gas, there is no danger of ignition, it can be degreased in the atmosphere with a non-explosion proof degreasing furnace, and cracks occur in the AlN green sheet. Moreover, it was found that after depolymerization, only BN powder substantially remains, and this acts as a mold release agent, which is very useful as a degreasing mold release agent for AlN green sheets. Further, in this case, since the release sheet is mainly made of acrylic resin, the moldability is good and the thickness is 1 to 200.
Since it can be made into an extremely thin sheet of μm, it is possible to stack more green sheets than before, and it is possible to significantly increase the number of sheets to be processed in the degreasing furnace, and it has been found that the production efficiency can be improved. The present invention has been completed.

Therefore, the present invention provides a release sheet comprising an acrylic resin as a main material and 1 to 30 parts by weight of boron nitride powder mixed with 100 parts by weight of the acrylic resin. provide.

The present invention will be described in more detail below. The release sheet of the present invention comprises an acrylic resin as a main material and boron nitride powder mixed therein to form a sheet.

Examples of the ductile material that can be formed into a thin film include light metals such as aluminum and various resins. However, since light metal does not volatilize and melts, it is not suitable for degreasing and firing steps.
It cannot be used because it impregnates the N substrate and remains as an impurity.

Therefore, the main material of the release sheet is selected from various resins. When a hydrocarbon resin such as vinyl chloride resin or vinyl acetate resin is used,
Since a carbon component remains during degreasing, which causes inconvenience, a depolymerizable resin is required. Further, when a resin having a high depolymerization rate is used, there is a risk of ignition when a non-explosion-proof degreasing furnace is used, and problems such as cracking of the AlN green sheet after degreasing may occur.

Therefore, it is essential that the resin as the main material of the present invention is depolymerizable and has a slow depolymerization reaction rate. As the resin satisfying the conditions, an acrylic resin is used as the main material. Is. In this case, the acrylic resin used may be PMMA alone or PMMA.
It may be a copolymer of MA with styrene, DMA or the like. Further, additives usually added may be appropriately added to these acrylic resins, if necessary.

Next, the boron nitride powder, which is another component of the release sheet of the present invention, is prepared by laminating the release sheet of the present invention together with a green sheet and degreasing it.
While the acrylic resin depolymerizes and volatilizes, it is an essential component that remains between the AlN green sheets and contributes to the prevention of adhesion between the sheets.

Here, the boron nitride powder preferably has an average particle diameter of 0.1 to 30 μm, particularly 0.5 to 10 μm. If it is less than 0.1 μm, the number of aggregated particles increases,
Uniform mixing with the acrylic resin may be difficult. On the other hand, when it exceeds 30 μm, the surface of the obtained release sheet may become rough. Further, the purity of the boron nitride powder is preferably 95% by weight or more, and particularly preferably 98% by weight or more. If the content is less than 95% by weight, the impurities contained may diffuse into the AlN green sheet to adversely affect the characteristics of the manufactured AlN substrate. Further, it is preferable that the boron nitride powder has a plate-like shape in which crystallization is sufficiently developed, and the Lc value measured by the Gakshin Carbon Material 117 Committee method is 500 Å or more, and particularly 700 Å or more. If the Lc value is less than 500 Å, the crystal may not be fully developed and sufficient releasability may not be obtained.

The content of the boron nitride powder is 1 to 30 parts by weight, preferably 10 to 20 parts by weight, based on 100 parts by weight of the acrylic resin. If the blending amount is less than 1 part by weight, sufficient releasability cannot be obtained, and if the blending amount exceeds 30 parts by weight, the plasticity of the acrylic resin composition increases, which causes deterioration of the sheet formability.

The release sheet of the present invention can be obtained by a conventional method using the above blending amounts of acrylic resin and boron nitride powder, and the production method is not particularly limited, but usually the above materials are used. It is obtained by heating and mixing with a planetary mixer or the like, and forming into a sheet using general-purpose equipment such as a calender roll, a doctor blade, and an extrusion molding machine.

In this case, the thickness of the release sheet of the present invention is not particularly limited, but when considering the productivity of the sheet molded body and the AlN substrate to be released,
The thickness is preferably 1 to 200 μm, particularly 10 to 50 μm.

The release sheet of the present invention can be used for various purposes such as degreasing and firing of ceramics and is not particularly limited, but as described above,
It can be suitably used when degreasing an aluminum nitride green sheet during the production of an AlN substrate. In this case, when using the release sheet of the present invention, by laminating between the green sheets before degreasing the aluminum nitride green sheet, it is possible to send a larger number of laminated layers to the degreasing furnace than in the past, so that industrially It is advantageous and has good formability because it can be punched with a large die-cutting tooth in a state of being laminated with a green sheet. In addition, after degreasing, only the boron nitride powder, which serves as the release agent, remains, so that the AlN green sheet is not cracked.

[0020]

INDUSTRIAL APPLICABILITY The release sheet of the present invention can be favorably used especially during degreasing in the manufacturing process of an aluminum nitride substrate, and by interposing and stacking between aluminum nitride green sheets, degreasing in a degreasing furnace is favorable. In addition to being able to provide good releasability to the degreased green sheet, it also has elasticity so that it can be punched well by the die-cutting teeth when laminated and has excellent moldability. is there.

[0021]

EXAMPLES Hereinafter, the present invention will be specifically described by showing Examples and Comparative Examples of the present invention, but the present invention is not limited to the following Examples.

[Examples 1 to 5] 100 parts by weight of acrylic resin (manufactured by Mitsubishi Rayon Co., Ltd., trade name: Acrypet) was added to boron nitride powder (manufactured by Shin-Etsu Chemical Co., Ltd., KB).
1, 5, 10, 20, 30 parts by weight of N (h) -sp) were mixed and mixed with a planetary mixer for 1 hour while heating at 200 ° C., and then a thickness of 20 μm with an extruder.
A strip sheet 20 m having a width of m and a width of 300 mm was molded to obtain a release sheet.

On the other hand, AlN powder 10 having an average particle diameter of 2 μm
After wet mixing 0 parts by weight and 3 parts by weight of Y ₂ O ₃ powder in ethanol, a doctor blade is used to form a thickness of 1 mm and a width of 30.
It was molded into 0 mm and a length of 20 m and dried to obtain an AlN green sheet.

Next, the release sheets obtained by various formulations were sandwiched between the 20 sheets of AlN green sheets, and the AlN green sheets were laminated. This laminated green sheet was cut at 1400 points with a Viku die-cutting tooth, 5 each
After punching out into a 0 mm square, put it in a degreasing furnace at 100 ° C.
The temperature was raised to 500 ° C. at a heating rate of / hr, and the temperature was maintained for 1 hour for degreasing in the atmosphere. When the green sheets were peeled off after degreasing, the green sheets could be well peeled without sticking to each other, and the obtained green sheets did not have defects such as cracks.

Comparative Example 1 Al was used without using a release sheet.
Example 1 except that only 20 N green sheets were laminated
Atmospheric degreasing was performed in the same manner as in. After degreasing, when the green sheet was peeled off, all the sheets were attached,
There was also a local crack.

Comparative Example 2 An AlN green sheet was degreased in the same manner as in Example 1 except that 0.5 part by weight of boron nitride powder was mixed with 100 parts by weight of an acrylic resin to form a release sheet. . When the green sheets were peeled off after degreasing, the green sheets adhered to each other.

Comparative Example 3 An attempt was made to prepare a release sheet in the same manner as in Example 1 by mixing 40 parts by weight of boron nitride powder with 100 parts by weight of an acrylic resin. I couldn't get a sheet for me.

[Comparative Examples 4 and 5] A release sheet was added to 100 parts by weight of a vinyl chloride resin composition consisting of 100 parts by weight of vinyl chloride resin, 30 parts by weight of dioctyl phthalate and 2 parts by weight of zinc stearate, and boron nitride powder. 5, respectively
Example 1 except that a release sheet was obtained by mixing 10 parts by weight.
In the same manner as above, the AlN green sheet was degreased.
After degreasing, when the green sheet was peeled off, AlN
Vinyl chloride resin was carbonized and adhered as a carbon component to the surface of the green sheet.

[Comparative Examples 6 and 7] The AlN green sheets were degreased in the same manner as in Comparative Examples 4 and 5 except that polyethylene resin was used instead of vinyl chloride resin to obtain release sheets. Since rapid depolymerization was performed in the degreasing step, when the AlN green sheet was peeled off after degreasing, cracks were formed in the green sheet.

[Comparative Examples 8 and 9] Dimethylsiloxane unit 99.85 mol%, methylvinylsiloxane unit 0.
To 100 parts by weight of 15 mol% of organopolysiloxane having an average degree of polymerization of about 8000, 25 parts of fumed silica are used.
To 100 parts by weight of a silicone rubber composition consisting of 1 part by weight and 0.8 parts by weight of 2,4-dichlorobenzoyl peroxide as a cross-linking agent, 5 and 10 parts by weight of boron nitride powder were blended, and after extrusion molding, The AlN green sheet was degreased in the same manner as in Example except that the release sheet of silicone rubber was obtained by carrying out thermal vulcanization under normal pressure at 150 ° C. for 2 hours. When the AlN green sheet was peeled off after degreasing, a silica component due to decomposition of siloxane remained on the green sheet.

A obtained by the above Examples and Comparative Examples
Table 1 shows the above results for the 1N green sheet (results of visual inspection of adhesion between sheets, cracks and residues of the obtained green sheet).

[0032]

[Table 1]

From the results shown in Table 1, good results were obtained when degreasing AlN green sheets using a release sheet satisfying the requirements of the present invention (Examples 1 to 5). on the other hand,
When a release sheet having a small amount of boron nitride powder added to the acrylic resin is used (Comparative Example 2), the release property of the green sheet becomes insufficient, and when the amount of boron nitride powder added is too large (comparison). Example 3), the release sheet could not be formed. Furthermore, when a material other than acrylic resin was used as the main material (Comparative Examples 4 to 9), quality deterioration such as residue remaining after degreasing and cracking of the peeled green sheet occurred.

From the above, it was confirmed that the release sheet of the present invention exhibits an excellent effect when degreasing the AlN green sheet.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display location C08K 3/38 B28B 11/00 Z C08L 33/06 LHU C04B 35/58 104Z // B29C 33/68 35/64 301

Claims (3)

[Claims] 1. A release sheet comprising 100 parts by weight of an acrylic resin and 1 to 30 parts by weight of boron nitride powder. 2. The release sheet according to claim 1, which has a thickness of 1 to 200 μm. 3. The release sheet according to claim 1, which is for degreasing an aluminum nitride green sheet.