JPH09182998A - Releasing sheet for press forming and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain such a releasing sheet for press forming that is provided with releasability and cushioning property and that is superior in dimensional stability and durability by interposing a fluororubber coated layer between plural base materials and providing a releasing layer on the surface of the base material. SOLUTION: An unvulcanized fluororubber solution is applied on either one or both of the oppositely facing surfaces of base material layers 2 and dried to form an unvulcanized fluororubber layer 3. Then, the base material layers 2 are laminated, with a releasing layer 4 provided on the surface side of the base material 2 situated on the uppermost and the lowermost position. The laminated base material is heated and pressurized, with the unvulcanized fluororubber layer 3 vulcanized, and with the entirety adhesively uniformized to form a releasing sheet for press forming. The base material layer 2 is desirably an inorganic material with a thermal conductivity of 0.6W/m.K or above. The thickness of the fluororubber coated layer 3 is desirably in the range of 20-200μm. For the releasing layer 4, a heat resistant releasing paint or film is used. This releasing sheet is superior in heat conductivity and capable of uniformizing the variance of temperature transmitted within the plane.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printed circuit board,
The present invention relates to a release sheet for press molding used for press molding or thermocompression bonding of electric / electronic equipment parts such as multilayer printed wiring boards and flexible printed wiring boards.

[0002]

2. Description of the Related Art Press molding of electric / electronic equipment parts such as a printed circuit board is carried out by a method as shown in FIG. That is, one or a plurality of molded products (1
9) is sandwiched by a pair of stainless steel mirror surface plates (20) from above and below, and the upper and lower sides are sandwiched by a pair of hot plates (22) via a cushion material (21) made of paper, felt, etc., and the whole is heated. It is a method of applying pressure. The molded article (19) is obtained by impregnating a base material such as woven cloth, non-woven cloth, paper or the like with a thermosetting resin such as epoxy resin, phenol resin or polyimide resin, and drying the prepreg to form a multilayer, or a unit. For example, a printed wiring board may be laminated in multiple layers via adhesive prepregs. Then, the mirror plate (20) and the molded product (19)
Or between the molded product (19) and the molded product (19)
A release sheet (23) is used between and to prevent the product (19) and the mirror plate (20) from adhering to each other.

As such a release sheet (23),
Conventionally, synthetic resin films such as polyethylene films, polypropylene films, polyester films, and fluororesin films have been used. However, these conventionally used release sheets (23) have a drawback that they cannot be repeatedly used once used because they cause irregularities and wrinkles due to thermal deformation when used for press molding. Further, if there is a temperature variation in the plane on the hot platen (22) side, the temperature variation is transmitted to the molded product (19) as it is, so that the quality of the product tends to vary. There was also.

In order to eliminate such a defect, the actual fairness 4
No. 28755 discloses that a reinforcing body made of a woven fabric (16) of polyamide fiber is embedded in the center of a fluororubber layer (17) as shown in FIG. 4, and the entire surface of the fluororubber layer is covered with fluororesin. A release sheet (15) has been proposed which is coated with a surface layer (18) made of This release sheet (15) has cushioning properties due to the fluororubber layer (17) and releasability due to the fluororesin release layer (18), and the polyamide fiber woven fabric (16) is embedded. It has durability and can be used repeatedly.

[0005]

[Problems to be Solved by the Invention]
The release sheet disclosed in Japanese Patent No. 28755 has a rubber layer (17), (1) which is subjected to heat and compression force.
Since 7) expands and contracts in the surface direction, the dimensional stability of the surface portion was not good. Further, since the thickness is considerably larger than that of the synthetic resin film alone, the efficiency of heat conduction was poor. Furthermore, it is also insufficient in terms of uniforming the temperature variation in the plane.

Therefore, the problem to be solved by the invention according to this application is that it has mold releasability and cushioning properties, is excellent in dimensional stability and durability, has good heat conduction efficiency, and has a transfer temperature in a plane. It is an object of the present invention to provide a release sheet for press molding that can make the variation of the above uniform.

[0007]

The present invention for solving the above problems includes an invention relating to a release sheet for press molding and an invention relating to a manufacturing method thereof.

The invention relating to the release sheet for press molding included in the present application has, as a basic idea, two or more base material layers,
It includes a novel structure of a press-molding release sheet having a coating (including impregnation) layer of fluororubber interposed between base material layers and a release layer on the surface.

[Base Material Layer] The base material layer mainly contributes to stabilizing the shape of the release sheet. As the base material layer,
Woven cloth, non-woven cloth, paper, sheet and the like are used. Examples of the material include heat-resistant organic materials and inorganic materials,
Considering the point of making the variation of the transfer temperature uniform, it is preferable to use an inorganic material having a thermal conductivity of 0.6 W / m · K or more. By using an inorganic material having a thermal conductivity of 0.6 W / m · K or more, the thermal conductivity of the release sheet, particularly the thermal conductivity in the plane direction, is improved, so that the temperature unevenness in the plane is It is effective in alleviating the heat and transmitting uniform heat to the molded product. Examples of the inorganic material that is suitably used as the base material layer include fibrous materials such as glass fiber, carbon fiber, slag / rock fiber, ceramic fiber, and metal fiber. Alternatively, a sheet-shaped material such as a metal foil may be used.

Considering the thermal conductivity in the surface direction of the release sheet, the prevention of expansion and contraction in the plane direction, and the adhesiveness between the base material layer and the fluororubber coating layer, woven cloth is used as the base material layer. Preferably.

The more the number of base layers is, the more the effect of uniformizing the transfer temperature is improved. However, if the number of layers exceeds a certain level, the effect cannot be expected to be improved even if the number of layers is increased, and the weight of the release sheet is increased. In addition, the thermal conductivity in the vertical direction becomes poor. For this reason, the number of base material layers is preferably 2 to 5 layers.

[Fluoro Rubber Coating Layer] The fluoro rubber coating layer mainly functions as an adhesive between the base material layers.
By using fluororubber as the adhesive between the base layers, the strong adhesion between the base layers can be maintained even when the release sheets are repeatedly used at high temperature, and the release sheets have a cushioning property. Can be given. Since the fluororubber layer is not a sheet formed by calendering or the like but a coating layer, it is a thin layer of several μm to several hundred μm. The thickness of the fluororubber coating layer is preferably 20 μm or more in order to bond the base material layers well and to give the release sheet cushioning properties. On the other hand, when the thickness of the fluororubber coating layer is too large, the thermal conductivity of the release sheet is lowered and the weight is increased.
For that reason, the thickness of the fluororubber coating layer is 200 μm.
It is preferable to set the following.

[Release Layer] The release layer is formed of a heat-resistant release material, and its form is either a heat-resistant release coating or a heat-resistant release film. Is mentioned.

As the heat-resistant release coating, a fluororesin-based coating,
Aromatic resin system, phenol resin system, melamine resin system, epoxy resin system, unsaturated polyester resin system, silicone resin system, polyimide resin system, thermosetting acrylic resin system,
Organic heat-resistant paints such as hydrogenated NBR, fluororubber, EPM, EPDM, etc., and inorganic silicates such as alkali silicates, colloidal silica, acidic metal phosphates, dichromic acid phosphates, and enamel. Heat-resistant paints and organic-inorganic composite heat-resistant paints such as alkyl silicate-based, alkyl titanate-based, boron siloxane-based can be mentioned,
They can be used alone, in a blend system or as a copolymer.

Examples of the heat resistant release film include a fluorine resin film, a polyimide resin film, a silicone resin film and an aromatic resin film.

The release layer is directly laminated on the surface of the base material layer located at the uppermost and lowermost portions, when it is laminated after being subjected to a primer treatment, and via the fluororubber coating layer. It may be laminated. In particular, when laminating via a fluororubber coating layer, the surface portion will have an appropriate cushioning property, and therefore a unit printed wiring board on the surface of which irregularities such as perforation processing and printed circuits are formed, It is preferably used for press molding for forming multiple layers. In this case, the thickness of the fluororubber coating layer is preferably 20 μm to 200 μm for the same reason as in the case of the fluororubber coating layer interposed between the base material layers. In particular, when the thickness of the fluororubber coating layer is too large, when the surface is exposed to heat and compression force, the fluororubber layer on the surface side expands and contracts, and the dimensions of the release sheet surface change. Therefore, the quality of the molded product is adversely affected, which is not preferable.

[Manufacturing Method] The invention relating to the method for manufacturing the release sheet for press molding included in the present application is directed to two or more base material layers, a fluororubber coating layer interposed between the base material layers, and a surface release mold. A method for producing a release sheet for press molding having a layer, wherein as a basic idea, an unvulcanized fluororubber is dissolved in a solvent to prepare an unvulcanized fluororubber solution, and the opposing surfaces of the base layers are opposed to each other. One or both of them is coated with the above-mentioned unvulcanized fluororubber solution and then dried to form an unvulcanized fluororubber coating layer, and the surface side of the base material layer located at the top and bottom is separated. A mold layer is provided, and after laminating each of these base materials, the whole is adhered and integrated by heating and pressurizing to vulcanize the unvulcanized fluororubber.

Here, the description already given is applied as it is to the base material layer, the fluororubber coating layer and the release layer.

As described above, the release layer is laminated directly on the surface side of the base material layer located at the uppermost and lowermost portions, when it is laminated after the primer treatment, and when it is made of fluororubber. It may be laminated via a coating layer,
When laminating via a fluororubber coating layer, the step of providing a release layer involves applying an unvulcanized fluororubber solution to the surface side of the base material layer located at the top and bottom and then drying it. After forming a coating layer of unvulcanized fluororubber, a release layer such as a heat-resistant release coating or a heat-resistant release film is laminated on the surface side thereof.

By the way, the unvulcanized fluororubber solution generally has poor storage stability. In particular, when the fluorocarbon rubber is required to have an adhesive function as in the present invention, it is necessary to sufficiently vulcanize it, and therefore it is necessary to blend a vulcanizing agent and an accelerator having high activity. Moreover, among the fluororubbers, polyol vulcanization type or amine vulcanization type fluororubbers, which are excellent in heat resistance, are vulcanized by an ionic reaction, and therefore methyl ethyl ketone (ME
When K) is used, vulcanization proceeds during storage and coating,
Gelation occurs and it becomes impossible to coat.

Therefore, in the present invention, paying attention to the relative permittivity (ε) of the solvent, dissolving the unvulcanized fluororubber compound in a solvent having a relative permittivity (ε) of 17 or less, preferably 12 or less. It has become possible to improve the storage stability of the unvulcanized fluororubber solution and delay the gelation time of the solution. In particular, when 0.5 to 5 parts by weight of an acid is added to 100 parts by weight of a compound of unvulcanized fluororubber in a solvent having a relative dielectric constant (ε) of 17 or less, preferably 12 or less, unvulcanized fluorine is obtained. It is preferable because the storage stability of the rubber is further improved.

Here, as the solvent, not only one having a relative dielectric constant (ε) of 17 or less is used alone, but two or more kinds of solvents are mixed even if the relative dielectric constant (ε) is larger than 17 alone. However, it can be used by adjusting the relative dielectric constant (ε) to 17 or less.

Solvents having a relative dielectric constant (ε) of 17 or less include methyl n-propyl ketone (MPK) and methyl n-
Butyl ketone (MBK), methyl isobutyl ketone (M
IBK), methyl n-amyl ketone (MAK), diethyl ketone (DEK), methyl formate, ethyl formate, propyl formate, amyl formate, methyl acetate, ethyl acetate, acetic acid n
-Propyl, n-butyl acetate, isobutyl acetate, n-acetate
-Amyl, isoamyl acetate, tetrahydrofuran (TH
F) etc. can be mentioned.

The acid added to the solvent as necessary is
One that evaporates together with the solvent during drying is used. Such acids include formic acid, acetic acid, acetic anhydride, glacial acetic acid, butyric acid,
Butyric anhydride and the like.

The unvulcanized fluororubber can be applied to the substrate by a knife coating method, a roll coating method, or dipping. When the viscosity of the fluororubber solution is low, the roll coating method or dipping is suitable. In this case, the fluororubber adheres to the surface of the base material, and the base material is impregnated with the whole or part of the fluororubber. It will be. On the other hand, in order to obtain a strong adhesive force, it is preferable to increase the viscosity of the fluororubber solution to be attached to the surface of the base material and apply the solution by knife coating.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION Representative embodiments of the present invention will be described below.

<Preparation of Unvulcanized Fluorine Rubber Solution> As a solvent, two kinds of 80 parts by weight of n-butyl acetate (ε = 5.2) and 20 parts by weight of methyl ethyl ketone (MEK: ε = 18.8) are used. A mixed solvent was prepared. The relative permittivity of this mixed solvent was ε = 7.9.

The above mixed solvent was added to the stirring layer, and then 2 parts by weight of acetic acid was added and stirred. Then, a compound of fluororubber (polyol vulcanization system: Daier G755C: manufactured by Daikin Industries, Ltd.) was added while stirring. Here, the melting temperature is 50 ° C or lower, and after the melting is completed,
Aged overnight. The solution obtained by dissolving unvulcanized fluororubber in MEK gelled during storage in about 3 days, but the unvulcanized fluororubber solution according to this embodiment did not gel for about 30 days.

Example 1> FIG. 1 shows the structure of a press-molding release sheet (1) according to Example 1. The release sheet (1) includes two base material layers (2), a fluororubber coating layer (3) having a thickness of about 80 μm interposed therebetween, and a release layer (4) having a thickness of about 15 μm located on the surface. It consists of and. As the base material (2), a plain weave glass cloth (UM Glass H201SD: manufactured by Unitika Ltd.) having a thickness of about 170 μm was used. The thermal conductivity of this substrate (2) is about 0.78 W / m · K.

First, 3.8 parts by weight of toluene and a titanate coupling agent (Plenact TTS: manufactured by Ajinomoto Co., Inc.) are used with respect to 100 parts by weight of the unvulcanized fluororubber solution.
0.12 parts by weight, calcium hydroxide (Rhenofit
-CF: manufactured by Rhein-Chemie) was mixed by 0.6 parts by weight, and the mixed solution was applied to one surface of the substrate by a knife coating method and dried. Next, a primer treatment is applied to one surface of the base material (1), and as a heat resistant coating,
A polyimide resin solution was applied and dried. In this way, the fluororubber coating layer (3) is formed on one surface of the base material (2).
Was formed, and two sheets (A) each having a coating layer (4) of a polyimide resin formed on the other surface were produced.

Next, the two sheets (A) were laminated with the surface of the unvulcanized fluororubber coated on the inside, and pressed at a temperature of 180 ° C. and a surface pressure of 20 kg / cm ² for 70 minutes to form an unvulcanized sheet. The fluororubber was vulcanized and integrated as a whole. In this way, a release sheet (1) for press molding of Example 1 having a thickness of about 0.4 mm was obtained.

Example 2 FIG. 2 shows the structure of a release sheet (5) for press molding according to Example 2. The release sheet (5) includes three base material layers (6), a fluororubber coating layer (7) having a thickness of about 80 μm interposed therebetween, and a release layer (8) having a thickness of about 15 μm located on the surface. And have. The release layer (8) is a coating layer (9) of fluororubber having a thickness of about 40 μm on the surface side of the base material layer located at the top and bottom.
Are stacked through. As the base material (6), the same three plain weave glass cloths as the base material (2) used in Example 1 were used.

First, in the same manner as in Example 1, a mixed solution of unvulcanized fluororubber was prepared. And this mixed solution,
Apply to both sides of each substrate layer (6) by knife coating method,
After drying, three sheets (B) each having a coating layer of unvulcanized fluororubber formed on both sides of the base material were prepared. Further, two sheets of the sheet (B) were each coated with a polyimide resin solution as a heat-resistant release coating on one side and dried to obtain a surface sheet (C).

(C)-(B)-(C) so that these three sheets are in contact with each other on the unvulcanized fluoro rubber application surfaces.
Are laminated in this order at a temperature of 180 ° C and a surface pressure of 20 kg / cm ^2.
For 70 minutes to vulcanize the unvulcanized fluororubber and integrate the whole. In this way, the thickness is about 0.
A 65 mm release sheet (5) for press molding of Example 2 was obtained.

Example 3> FIG. 3 shows the structure of a release sheet (10) for press molding according to Example 3. The release sheet (10) is composed of five base material layers (11), a fluororubber coating layer (12) having a thickness of about 80 μm positioned between them, and a release layer (13) having a thickness of about 50 μm positioned on the surface. And have. The release layer (13) is laminated on the front surface side of the base material layers located at the uppermost and lowermost portions with the fluororubber coating layer (14) having a thickness of about 40 μm interposed therebetween. As the base material (11), the same five plain weave glass cloths as the base material (2) used in Example 1 were used. As the release layer (13), a fluororesin film (Neoprene FEP: manufactured by Daikin Industries, Ltd.) having a thickness of about 50 μm and made of tetrafluoroethylene-6 propylene fluorinated copolymer resin (FEP) was used.

First, in the same manner as in Example 2, five sheets (B) each having an unvulcanized fluororubber coating layer formed on both sides of the substrate were prepared. Then, these five sheets (B) are laminated, and the fluororesin film (1
3) are laminated and the temperature is 180 ° C and the surface pressure is 20 kg / cm ²
For 70 minutes to vulcanize the unvulcanized fluororubber and integrate the whole. In this way, the thickness is about 1.
15 mm release sheet for press molding of Example 3 (10)
I got

[0037]

[Comparative Test] In order to confirm the effect of the present invention, a comparative test was carried out as follows using the release sheets for press molding of Examples 1 to 3 and Comparative Examples 1 and 2 below. .

<Comparative Example 1> A single sheet of a fluororesin film (Neotron FEP) having a thickness of about 50 μm was used as a release sheet for press molding of Comparative Example 1.

Comparative Example 2 The release sheet for press molding shown in FIG. 4 was used as Comparative Example 2. That is, a plain weave woven fabric (16) made of polyamide fiber having a thickness of about 200 μm (heat conductivity of 0.1
(5W / mK) 1 sheet on both upper and lower sides, calendered, unvulcanized fluororubber sheet (17) with a thickness of about 0.5mm
Each with a thickness of about 50
μm Fluorine resin film (Neoflon FEP) (1
8) are laminated and the temperature is 180 ° C and the surface pressure is 20 kg / cm ^2.
For 70 minutes to vulcanize the unvulcanized fluororubber and integrate the whole. In this way, the thickness is about 1.
A 2 mm release sheet (15) for press molding of Comparative Example 2 was obtained.

Test 1 (Releasability and Cushioning Property) For each release sheet, the release sheet was inserted between a pair of hot plates in a state of being sandwiched between two stainless specular plates, and the heating temperature was 180 °. C, the amount of change in thickness when pressed at a pressure of 20 kg / cm ² was measured (→ cushioning property). After pressing for 60 minutes in that state, the presence or absence of tackiness when opened was checked (→ releasability).

Test 2 (Durability and Dimensional Stability) For each release sheet, the release sheet was inserted between a pair of hot plates in a state of being sandwiched between two stainless specular plates, and the heating temperature was 210 °. C, a pressurizing force of 20 kg / cm ² , heating and pressurizing 60 minutes → cooling 15 minutes → opening 5 minutes were set as one cycle, and this was repeated 100 cycles, and the state of the release sheet was confirmed (→ durability). After finishing, measure the dimensions of the release sheet,
The dimensional change rate with respect to the dimension of the release sheet before the test was calculated (→ dimensional stability).

Test 3 (Heat Conductivity) With respect to each release sheet, two release sheets were superposed and inserted between a pair of hot plates in a state of being sandwiched between two stainless specular plates. It was pressed at a heating temperature (hot platen temperature) of 180 ° C. and a pressure of 20 kg / cm ² for 20 minutes. At this time, 2
The temperature was measured at four points between the release sheets. The average value of the temperature at four places was calculated (→ thermal conductivity in the vertical direction). The difference between the maximum temperature and the minimum temperature was calculated (→ thermal conductivity in the plane direction). Incidentally, when the temperature was similarly measured without interposing the release sheet, the difference between the maximum temperature and the minimum temperature was 4 ° C.

The results of the comparative test are shown in Table 1.

[0044]

[Table 1]

[0045]

The effects of the invention of the release sheet for press molding according to the present application can be summarized as follows. (1) Since it requires two or more base material layers and a fluororubber coating layer interposed between the base material layers, it is excellent in dimensional stability and durability. Moreover, since the thickness is not so large, the efficiency of heat conduction is not impaired. (2) Since it has a coating layer of fluororubber, it has cushioning properties. (3) Since the surface is the release layer, it has releasability. (4) By using an inorganic material having a thermal conductivity of 0.6 W / m · K or more as the base material layer, it is possible to alleviate temperature unevenness in a plane and transfer uniform heat to the molded product. it can. (5) By laminating the release layer via the fluororubber coating layer, it is possible to provide the surface portion with an appropriate cushioning property, which is suitably used for multilayer press molding of a member having irregularities on the surface. can do.

According to the method for producing a release sheet for press molding according to this application, it has mold releasability and cushioning properties, excellent dimensional stability and durability, good heat conduction efficiency, and good in-plane It is possible to obtain a release sheet for press molding which can make the variation of the transmission temperature uniform.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a release sheet for press molding according to Example 1 of the present invention.

FIG. 2 is a sectional view showing a release sheet for press molding according to Example 2 of the present invention.

FIG. 3 is a cross-sectional view showing a release sheet for press molding according to Example 3 of the present invention.

FIG. 4 is a cross-sectional view showing an example (comparative example 2) of a conventional release sheet for press molding.

FIG. 5 is a cross-sectional view showing an outline of a press molding method.

[Explanation of symbols]

1, 5, 10, 15, 23 Release sheet for press molding 2, 6, 11 Base material layer (plain weave glass cloth) 3, 7, 12 Fluorine rubber coating layer 4, 8 Release layer (polyimide resin coating layer) ) 9,14 Fluorine rubber coating layer 13 Release layer (fluorine resin film)

Claims (10)

[Claims] 1. A release sheet for press molding, comprising two or more base layers, a fluororubber coating layer interposed between the base layers, and a release layer on the surface. 2. The release sheet for press molding according to claim 1, wherein the base material layer is made of an inorganic material having a thermal conductivity of 0.6 W / m · K or more. 3. The release sheet for press molding according to claim 1 or 2, wherein the fluororubber coating layer has a thickness of 20 μm to 200 μm. 4. The release sheet for press molding according to any one of claims 1 to 3, wherein the release layer is formed of a heat-resistant release coating material. 5. The release sheet for press molding according to claim 1, wherein the release layer is formed of a heat resistant release film. 6. The release layer according to any one of claims 1 to 5, wherein the release layer is laminated on the surface side of the base material layer located at the uppermost and lowermost portions with a fluororubber coating layer interposed therebetween. Release sheet for press molding. 7. A method for producing a release sheet for press molding, comprising two or more base layers, a fluororubber coating layer interposed between the base layers, and a release layer on the surface, wherein the solvent is a solvent. An unvulcanized fluororubber solution is prepared by dissolving unvulcanized fluororubber therein, and the unvulcanized fluororubber melt is applied to one or both of the opposing surfaces of the base material layers and then dried to obtain an unvulcanized fluororubber solution. A coating layer of vulcanized fluororubber is formed, and a release layer is provided on the top surface side of the base material layer located at the top and bottom. A method for producing a release sheet for press molding, wherein the whole is adhered and integrated by vulcanization of rubber. 8. The step of providing the release layer according to claim 7, wherein the unvulcanized fluororubber solution is applied to the surface side of the base material layer located at the uppermost and lowermost portions and is not dried. A method for producing a release sheet for press molding, comprising forming a coating layer of vulcanized fluororubber and then laminating the release layer on the surface side thereof. 9. The method for producing a release sheet for press molding according to claim 7, wherein the solvent for dissolving the unvulcanized fluororubber has a relative dielectric constant (ε) of 17 or less. 10. The unvulcanized fluororubber solution according to claim 7 or 8, wherein the acid is added to 100 parts by weight of the unvulcanized fluororubber compound in a solvent having a relative dielectric constant (ε) of 17 or less. A method for producing a release sheet for press molding, which comprises 0.5 to 5 parts by weight.