JP2007296727A - Release sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a release sheet which has releasing properties and in which both cushioning properties and thermal conductivity are easily compatible with each other. <P>SOLUTION: The release sheet 10 has a glass fiber layer 1 and a release layer 2 containing a fluororesin, and one of the main faces 21 of the release layer 2 is exposed. The release layer 2 preferably has gaps inside. As the release layer having the gaps inside, a woven fabric, a nonwoven fabric or a porous body may be used. As the woven fabric and the nonwoven fabric, a woven fabric and a nonwoven fabric made of a glass fiber are available. When these are used, from a view point of providing the release properties, an article impregnated with the fluororesin is preferably used. From the similar point of view, as the porous body, a porous body of the fluororesin is preferably used. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a release sheet used for crimping and joining work of electronic components.

  In order to automate and speed up the mounting and wiring connection of electronic components, technology relating to pressure bonding using a tape automated bonding (TAB) method is actively developed. An example of a bonding tape used in the TAB method is an anisotropic conductive film (Anisotropic Conductive Flim: ACF). ACF is often used in the production of flat panel displays (FPD) such as liquid crystal systems, plasma systems, and electroluminescent systems. For example, it is used for connection between a glass substrate and a driving IC, or connection between a driving IC and a printed circuit board.

  For example, the pressure bonding using the ACF is performed as follows. First, as shown in FIG. 2, an electrode 104 provided on a liquid crystal panel 105 and an electrode 102 provided on a tape carrier package (TCP) 101 on which a semiconductor chip for driving liquid crystal is mounted. The ACF 103 is disposed between the two. The ACF 103 is composed of a binder 103b made of a thermosetting epoxy resin and conductive particles 103a dispersed in the binder 103b. As shown in FIG. 4, the liquid crystal panel 105 and the TCP 101 stacked via the ACF 103 are placed on the stage 107, and then the TCP 101 is pressed from above using a heating head 108 heated to about 300 ° C. By this pressing, the binder 103b of the ACF 103 is melted, and as shown in FIG. 3, the liquid crystal panel 105 and the TCP 101 are joined together, and the conductive particles 103a cause conduction between the electrode 102 and the electrode 104. Become.

  As shown in FIG. 4, the pressure bonding is performed by disposing a release sheet 106 between the TCP 101 and the heating head 108. This is to prevent the melted ACF 103 from protruding from between the TCP 101 and the liquid crystal panel 105 and adhering to the heating head 108.

  From the viewpoint of improving the releasability of the release sheet, a fluorine-based resin typified by polytetrafluoroethylene (PTFE) has attracted attention as its material. However, the thermal conductivity of the fluororesin is inferior compared to other sheet materials. The release sheet is required to have not only releasability but also excellent thermal conductivity so that the heat of the heating head can be satisfactorily transmitted to the ACF. For this reason, when the release sheet is made of a fluorine-based resin, the sheet is designed to be thin.

  With the recent increase in the size of FPD modules, unevenness and variations in parallelism in connecting works such as TCP, COF (Chip On Film), and FPC (Flexible Print Circuit) are increasing. For this reason, if the release sheet made of fluororesin is thinned to such an extent that sufficient thermal conductivity is obtained, a uniform pressure distribution cannot be obtained during pressure bonding, in other words, a good cushion. In some cases, the connection work or the glass substrate of the FPD may be damaged by the impact caused by the pressing.

A technique for forming a release sheet by laminating a fluororesin film and a silicone rubber film for the purpose of enhancing the release property and cushioning property of the release sheet is known (Patent Document 1). In this technique, the cushioning property is improved by setting the thickness of the silicone rubber film in the range of 0.2 to 5 mm.
JP 2001-315248 A

  The conventional release sheet as disclosed in Patent Document 1 has a problem that it is inferior in thermal conductivity. If the release sheet is made thin in order to ensure thermal conductivity, the cushioning property is lowered. An object of this invention is to provide the release sheet which has mold release property and is easy to make cushion property and heat conductivity compatible.

  The present invention provides a release sheet having a glass fiber layer and a release layer containing a fluororesin, wherein one main surface of the release layer is exposed.

  In the present invention, release properties are secured by a release layer containing a fluororesin, and cushion properties are secured mainly by a glass fiber layer. The glass fiber layer is suitable for both cushioning properties and thermal conductivity in a pressed state. Thus, according to the present invention, it is possible to provide a release sheet having releasability and easy compatibility between cushioning properties and thermal conductivity.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view of an example of the release sheet 10 of the present invention. The release sheet 10 has a glass fiber layer 1 and a release layer 2 disposed on the glass fiber layer 1. One main surface 21 of the release layer 2 is exposed, and the other main surface 22 is bonded to the glass fiber layer 1 through the adhesive layer 3.

  The release sheet 10 is preferably used for the purpose of pressure bonding via ACF. In this case, the release sheet 10 is used by disposing the release layer 2 between the heating head and the pressed object in a state where the release layer 2 is directed to the pressed object typified by TCP disposed on the ACF. Will be.

  The glass fiber layer 1 is composed of a woven fabric (glass cloth) or a nonwoven fabric of glass fibers. The glass fiber layer can be obtained, for example, as MC paper manufactured by Nippon Sheet Glass Co., Ltd. or S111-A manufactured by Hokuetsu Paper Co., Ltd.

  The thickness of the glass fiber layer may be set in the range of 100 μm to 400 μm. If the thickness is less than 100 μm, the cushioning property of the release sheet may extremely decrease. On the other hand, if it exceeds 400 μm, the thermal conductivity of the release sheet may be lowered to such an extent that sufficient pressure bonding is difficult.

  The release layer 2 contains a fluororesin. Examples of the fluororesin include PTFE, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), perfluoroethylene propene copolymer (FEP), ethylene-tetrafluoroethylene copolymer (ETFE), polyvinylidene fluoride (PVDF), poly Chlorotrifluoroethine (PCTFE), ethylene-chlorotrifluoroethylene copolymer (ECTFE), polyvinyl fluoride (PVF), or the like may be used. In particular, the use of PTFE is preferred. This is because it becomes easier to improve the flexibility of the release layer as compared with the case where other fluororesins are used. When the flexibility of the release layer is increased, the release sheet is more likely to adhere along the surface shape of the pressed object typified by TCP during pressure bonding, and a uniform pressure distribution is easily obtained.

  The thickness of the release layer is preferably set in the range of 20 μm to 100 μm, and in some cases, in the range of 50 μm to 100 μm. When the thickness is less than 20 μm, the release layer tends to be damaged, and the number of times the release sheet can be used repeatedly may be extremely reduced. On the other hand, if it exceeds 100 μm, the thermal conductivity of the release sheet may be lowered to such an extent that sufficient pressure bonding is difficult.

  The release layer preferably has voids inside. This is because, as shown in Examples to be described later, when a void is formed inside the release layer, the thermal conductivity of the release sheet is improved in the pressed state. As the release layer having voids inside, a woven fabric, a nonwoven fabric or a porous body may be used. Examples of the woven fabric and nonwoven fabric include glass fiber woven fabric and nonwoven fabric. When these are used, it is preferable to use those impregnated with a fluororesin from the viewpoint of providing releasability. In this case, the release layer is a glass fiber layer impregnated with a fluororesin. From the same viewpoint, it is preferable to use a fluororesin porous body as the porous body.

  Glass cloth impregnated with fluororesin is, for example, No. manufactured by Nippon Valqua Industries, Ltd. 7921, Nitto Denko No. 971 etc. are available. The porous body of a fluororesin can be obtained as, for example, pore-flon membrane HP-045-30 manufactured by Sumitomo Electric Fine Polymer, NTF1026 manufactured by Nitto Denko. Note that the release layer may not have voids formed therein. In this case, the release layer is, for example, No. manufactured by Nippon Valqua Industries, Ltd. 7991, Nitto Denko No. It can be obtained as a fluororesin film such as 901.

  The release layer and the glass fiber layer are preferably joined with an adhesive. This is because the bondability between the release layer and the glass fiber layer can be improved, and the durability of the release sheet can be improved. For example, as shown in FIG. 1, the bonding may be performed in a state where the adhesive layer 3 is formed, or, for example, as shown in FIG. You may carry out in the state which impregnated the adhesive 4 in the vicinity of the main surface 11 by the side of the release layer 2 of the fiber layer 1. FIG. From the viewpoint of improving the heat resistance of the release sheet, it is preferable to use a silicone-based adhesive typified by a silicone rubber paste. In some cases, a PFA dispersion may be used. These adhesives can be obtained, for example, as JCR6160 manufactured by Toray Dow Corning, TSE392 manufactured by GE Toshiba Silicone, KE-1842 manufactured by Shin-Etsu Silicone, or as neoflon AD-2CRE manufactured by Daikin Industries. The adhesive may further contain, for example, a thermally conductive filler such as boron nitride, aluminum nitride, magnesium oxide, or silicon carbide. When the thickness of the adhesive in the release sheet, specifically, the thickness of the adhesive layer 3 and the thickness of the portion of the glass fiber layer impregnated with the adhesive 4 are set in the range of 5 μm to 50 μm. Good. If the thickness is less than 5 μm, the bonding force by the adhesive may be extremely reduced. On the other hand, if it exceeds 50 μm, the thermal conductivity of the release sheet may be lowered to such an extent that sufficient pressure bonding is difficult.

  As described above, the release sheet is preferably used for the purpose of pressure bonding via ACF. In this application, in the release sheet, since it is not necessary to give release properties to the surface on the heating head side, the main surface on the heating head side of the glass fiber layer is exposed without placing the release layer thereon. You can let it go. If a release layer is also disposed on the main surface, the thermal conductivity of the release sheet may be reduced.

  EXAMPLES Hereinafter, although this invention is demonstrated further more concretely using an Example, this invention is not limited by this.

Example 1
After applying a silicone rubber paste (KE-1842 made by Shin-Etsu Silicone) on the adhesion-treated surface of the adhesion-treated PTFE film (Nitto Denko No.901, thickness: 25 μm) to a thickness of 50 μm Further, a glass fiber nonwoven fabric (S111-A manufactured by Hokuetsu Paper Co., Ltd., thickness: 200 μm) was placed thereon. Then, it passed between a pair of crimping | compression-bonding rolls, and the PTFE film and the glass fiber nonwoven fabric were temporarily bonded. The temporary bonding was performed by setting the surface temperature of the pressure-bonding roll to 160 ° C. and the linear pressure between the pressure-bonding rolls to 20 kg / cm ² . In this case, the silicone paste is impregnated into a part of the glass fiber nonwoven fabric. Finally, by heating at 120 ° C. for 1 hour to cure the silicone rubber paste, the PTFE film and the glass fiber nonwoven fabric were finally bonded to obtain a release sheet having a total thickness of 225 μm. In this example, a release layer is formed by the PTFE film, and a glass fiber layer (cushion layer) is formed by the glass fiber nonwoven fabric.

(Example 2)
In the same manner as in Example 1, except that PTFE-impregnated glass cloth (Nitto Denko No. 971, thickness: 50 μm) was used instead of the adhesion-treated PTFE film (Nitto Denko No. 901). A release sheet having a thickness of 250 μm was obtained. In this example, the release layer is formed of PTFE-impregnated glass cloth.

(Example 3)
A total thickness of 225 μm was used in the same manner as in Example 1 except that a PTFE porous body (NTF1026 manufactured by Nitto Denko Corporation, thickness: 25 μm) was used instead of the adhesive-treated PTFE film (Nitto Denko Corporation No. 901). A release sheet was obtained. In this example, the release layer is formed of the PTFE porous body.

(Comparative Example 1)
A sheet consisting only of a PTFE film (Nitto Denko No. 900, thickness: 50 μm) was prepared.

(Comparative Example 2)
Comparative Example 2 is a conventional release sheet in which a cushion layer is formed of silicone rubber. This release sheet was produced as follows.

  A silicone rubber paste (KE-1842, manufactured by Shin-Etsu Silicone) was applied on the adhesive-treated surface of an adhesive-treated PTFE film (No. 901, manufactured by Nitto Denko Corporation, thickness: 25 μm). Then, it heated at 120 degreeC for 1 hour, the apply | coated silicone rubber paste was hardened, the 200-micrometer-thick silicone rubber layer (cushion layer) was formed, and the release sheet with a total thickness of 225 micrometers was obtained.

(Comparative Example 3)
A release sheet having a total thickness of 75 μm was obtained in the same manner as in Comparative Example 2 except that a silicone rubber layer having a thickness of 50 μm was formed.

  About the sheet | seat of Examples 1-3 and Comparative Examples 1-3, mold release property, cushion property, and heat conductivity were test | inspected as follows. The results are shown in Table 1.

[Inspection method for releasability]
After laminating a glass substrate, ACF (AC7206U-18 manufactured by Hitachi Chemical Co., Ltd.), FPC, and sheet to be inspected in this order from the bottom to an anisolum thermocompression bonding machine (AC-S50 manufactured by Nikka Equipment Engineering Co., Ltd.) The heated heating head was pressed against the inspection target sheet at a pressure of 3 MPa for 20 seconds. Each sheet to be inspected was 25 mm × 100 mm in size, and was arranged so that the main surface of the release layer was in contact with the FPC. After the pressing, when peeling between the sheet to be inspected and the FPC, if the adhesion is confirmed between the two, the release property is inferior (x), and if the adhesion is not confirmed, the release property is good (○). Judged that there was.

[Cushioning inspection method]
In order to investigate the pressure distribution at the time of pressure bonding, pressing was performed in the same manner as the method for inspecting releasability. The shape during pressing of each conductive particle in the ACF arranged between the plurality of electrodes provided on the FPC and having different heights and the glass substrate was observed from the glass substrate side using a microscope. . When there was almost no variation in the deformed shape of each conductive particle, it was judged that the cushioning property was good (◯), and when the variation in the deformed shape was large, the cushioning property was inferior (×). In addition, the shape of each electroconductive particle in ACF before implementing pressing was substantially in agreement.

[Thermal conductivity inspection method]
In a state where a temperature sensor (DP-500 manufactured by Rika Kogyo Co., Ltd.) is disposed between the FPC and the ACF, pressing is performed in the same manner as the method for inspecting releasability, and the temperature after 20 seconds from the start of pressing is Detected with a temperature sensor.

  As shown in Table 1, it was found that all of the release sheets of Examples 1 to 3 were obtained while ensuring good release properties and at the same time achieving good thermal conductivity and cushioning properties. . Moreover, it turned out that Example 2 and 3 exhibits the further outstanding thermal conductivity compared with Example 1. FIG. On the other hand, in the sheets of Comparative Examples 1 to 3, none of the cushioning properties and the thermal conductivity were obtained in the same degree as the sheets of Examples 1 to 3.

  The present invention can be applied to providing a release sheet having releasability and easy to satisfy both cushioning properties and thermal conductivity.

It is sectional drawing which shows an example of the release sheet of this invention. It is a figure for demonstrating the crimping | compression-bonding using ACF. It is a figure for demonstrating the crimping | compression-bonding using ACF. It is a figure for demonstrating the crimping | compression-bonding using ACF. It is sectional drawing which shows another example of the release sheet of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Glass fiber layer 2 Release layer 3 Adhesive layer 4 Adhesive (Impregnated into the glass fiber layer) 10 Release sheet 11 Main surface on the release layer side of the glass fiber layer 21 One main surface 22 of the release layer The other main surface of the release layer

Claims (14)

  A release sheet having a glass fiber layer and a release layer containing a fluororesin, wherein one main surface of the release layer is exposed.   The release sheet according to claim 1, wherein the glass fiber layer has a thickness in the range of 100 μm to 400 μm.   The release sheet according to claim 1, wherein the release layer has a thickness in the range of 20 μm to 100 μm.   The release sheet according to claim 1, wherein one main surface of the glass fiber layer is exposed.   The release sheet according to claim 1, wherein the release layer has voids therein.   The release sheet according to claim 5, wherein the release layer is a woven fabric, a nonwoven fabric or a porous body.   The release sheet according to claim 5, wherein the release layer is a glass fiber layer impregnated with a fluororesin.   The release sheet according to claim 6, wherein the release layer is a porous body of a fluororesin.   The release sheet according to claim 1, wherein the fluororesin is polytetrafluoroethylene.   The release sheet according to claim 1, wherein the glass fiber layer is a glass fiber nonwoven fabric.   The adhesive layer further disposed between the glass fiber layer and the release layer, wherein the adhesive layer includes silicone rubber or a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer. Release sheet as described in 1.   The release sheet according to claim 11, wherein the adhesive layer contains silicone rubber.   The release sheet according to claim 1, wherein a part of the glass fiber layer is impregnated with an adhesive containing silicone rubber or a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer.   The release sheet according to claim 13, wherein the adhesive contains silicone rubber.

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