JP2005187526A - Mold release film and method for producing flexible film with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mold release multi-layered film which maintains excellent characteristics such as mold release characteristic, shape followingness, uniform moldability and FPC finish appearance wrinkles, and has improved solder adhesiveness to circuits in post processes, not satisfied by conventional mold release films, and to provide a method for producing FPC with the same. <P>SOLUTION: This mold release film having a mold release layer comprising polymethylpentene, a polymethylpentene/α-olefin copolymer, or polybutylene terephthalate, and having TMA of 2-7% in 160 to 185°C. The method for producing FPC uses the same. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a release film used in a manufacturing process of a flexible printed wiring board (hereinafter referred to as FPC) and a method of manufacturing an FPC using the release film.

In the FPC manufacturing process, a coverlay (hereinafter referred to as CL), which is a heat-resistant resin film with an adhesive, is formed on an insulating base material, for example, a flexible circuit board having a predetermined circuit on a polyimide resin film surface for the purpose of insulation and circuit protection. In general, press lamination is performed using a release film as in Patent Document 1. In this manufacturing process, releasability between the FPC and this plate, suppression of the adhesive flow from the CL end face by sufficiently following the unevenness of the FPC and prevention of contamination of the conductor part, and further uniformization of the pressure applied to the entire FPC, In addition to low mold releasability, anti-trackability, devoid of voids due to uniform pressure on the entire FPC (hereinafter referred to as moldability), FPC finished appearance wrinkles, and film end face wrinkles during pressing. There is a need for a release film that is excellent in plating on the circuit.
Japanese Patent No. 2659404

  In the present invention, while maintaining excellent properties such as releasability, shape conformability, uniform formability, and FPC finished appearance wrinkles, the circuit is plated in a later process that was not satisfactory with conventional release films. A release film having improved properties and a method for producing an FPC using the release film are provided.

The present invention
(1) A release film having a first layer composed of a first thermoplastic resin, wherein the first layer has a linear expansion coefficient of 2 to 7 in a region where the temperature is 160 to 185 ° C. % Release film,
(2) The release film according to item (1), further comprising a second layer on at least one side of the first layer,
(3) The release film according to (2), wherein the second layer is composed of a second thermoplastic resin different from the first thermoplastic resin.
(4) The release film according to any one of (1) to (3), wherein the first thermoplastic resin includes polymethylpentene, polybutylene terephthalate, and polypropylene.
(5) The release film according to (3), wherein the second thermoplastic resin has a softening point of 50 to 160 ° C.
(6) A method for producing a flexible printed wiring board, wherein the release film according to any one of (1) to (4), an adhesive film, and a laminate are laminated in this order. Manufacturing method of flexible printed wiring board,
It is.

  In the present invention, while maintaining the mold release property, the shape following property, the uniform moldability, and the excellent finish of the appearance finish of the FPC, the plating on the circuit in the post-process that could not be achieved by the conventional release film. A release film with improved adhesion and an FPC manufacturing method using the same are provided.

  The release film of the present invention has a linear expansion coefficient (hereinafter referred to as TMA) of a first layer (referred to as a release layer) composed of a first thermoplastic resin in a temperature range of 160 to 185 ° C. 2-7%. If it is less than 2% or exceeds 7%, the ability to plate the circuit in the subsequent process is deteriorated due to the effect of thermal shrinkage during pressing. With regard to the plating property, solder, nickel, and gold are plated after CL molding. At that time, a product having 90% or more of the required plating area is regarded as a good product.

  The resin used for the release layer of the present invention is polymethylpentene or a copolymer of polymethylpentene and α-olefin, a polyester resin, and polypropylene. Polymethylpentene is represented by the following formula (1). There are no particular limitations on the copolymerization ratio of the copolymer of polymethylpentene and α-olefin and the type of α-olefin.

  The thickness of the release layer is 10 to 100 μm. Preferably it is 15-50 micrometers. When the thickness is less than 10 μm, the resin used for the release layer is broken after press lamination, and when the FPC and the release film are separated, the resin used for the release layer remains on the FPC side. When the thickness exceeds 100 μm, the shape following ability is deteriorated, and the flow amount of the adhesive adhering to the CL increases.

  The resin used for the resin constituting the second layer of the present invention (referred to as a cushion layer) has a softening point of 50 to 160 ° C. When the temperature is lower than 50 ° C., the resin begins to stain from the end face of the release film during pressing, adheres to the press hot platen, etc., and there is a concern of secondary contamination in the next process. If it exceeds 160 ° C., the moldability is poor and voids are generated in the details of the FPC. The cushion layer thickness is not particularly specified.

  Although there is no problem even if an adhesive resin is interposed between the release layer and the cushion layer, it is preferable that no adhesive resin is interposed between the film and the film to prevent the end face from appearing.

The method for producing the release film used in the present invention may be any method such as a coextrusion laminating method, an extrusion laminating method, or a dry laminating method.

  As a molding method in which the release film of the present invention is used for CL press lamination in the FPC manufacturing process and is pressure-laminated, for example, a structure in which a release film and a single-sided FPC are stacked in this order between hot plates are used. Then, after heating and pressing under predetermined conditions, post-curing may be performed. The release film used in the present invention is particularly effective for a short-time molding method (generally referred to as a hot-hot press).

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited to these examples. The characteristics of the raw materials used in the following examples and comparative examples are as follows.
-Copolymer of polymethylpentene and α-olefin (TPX): product number MX004 (melting point 240 ° C.) (manufactured by Mitsui Chemicals, Inc.)
-Polybutylene terephthalate (PBT): product number 5510S [melting point 217 ° C.] (manufactured by Mitsubishi Engineering Plastics)
-Ethylene-methyl acrylate copolymer (EMMA): Part number ACRIFT WD105-1 [Softening point 75 ° C] (manufactured by Sumitomo Chemical Co., Ltd.)
-Ethylene-methyl acrylate copolymer (EMMA): product number ACRIFTH WH102 [softening 60 ° C] (manufactured by Sumitomo Chemical Co., Ltd.)
Polypropylene: Nobrene FH1016 [softening point 150 ° C.] (manufactured by Sumitomo Chemical Co., Ltd.)

<Examples 1-5>
In Examples 1 to 4, each of the three extruders was co-extruded with a three-layer die by supplying TPX or PBT as the release layer, EMMA or PP as the cushion layer, and TPX or PBT as the release layer opposite to the release layer. A release film having the composition shown in Table 1 was prepared.
In Example 5, the film was formed by supplying TPX to a single-layer die in one extruder, and a single-layer release film having the composition shown in Table 1 was produced.
The TMA of the release film was measured with EXSTAR6000 manufactured by Seiko Instruments Inc. The measurement conditions are a tension method, a temperature increase of 5 ° C./min, a load of 5 g, and a room temperature to 220 ° C. Table 1 shows the values of TMA of MD and TD at 160 to 185 ° C.
The release film and the FPC were taken out using a one-stage press machine, heated and pressurized at 185 ° C. and 5 MPa for 2 minutes, and then evaluated according to the following evaluation items. The evaluation results are shown in Table 1.

<Comparative Examples 1-4>
Each of the three extruders was co-extruded with a three-layer die by supplying TPX as a release layer, EMMA or PP as a cushion layer, and TPX as a release layer, and having the composition shown in Table 2 A film was created.
The release film and the FPC were taken out using a one-stage press machine, heated and pressurized at 185 ° C. and 5 MPa for 2 minutes, and then evaluated according to the following evaluation items. The evaluation results are shown in Table 2.
The TMA of the release film was measured with EXSTAR6000 manufactured by Seiko Instruments Inc. The measurement conditions were the tension method, temperature rise of 5 ° C./min, load of 5 g, and normal temperature to 220 ° C.
The evaluation was made according to the JPCA standard (design guide manual, single-sided and double-sided flexible printed wiring board, JPCA-DG02) and the following items and standards.

Formability (due to air bubbles in 7.5.3.3)
○: Void generation rate less than 2.0% ×: Void generation rate 2.0% or more CL adhesive flow amount (due to coverlay adhesive flow and cover coat bleeding in 7.5.3.6)
○: Flow amount less than 150 μm ×: Flow amount 150 μm or more Finished appearance wrinkle
○: Wrinkle generation rate less than 2.0% ×: Wrinkle generation rate 2.0% or more Releasing of release layer resin (due to 7.5.7.1 surface deposits)
○: Breakage rate less than 2.0% ×: Breakage rate 2.0% or more Plating property (A product with 90% or more of the necessary plating area is plated: Appearance of 7.5.4 plating) by)
○: Good product is 98% or more ×: Good product is less than 98%

  The present invention is not satisfactory with the conventional release multilayer film while maintaining excellent properties such as releasability, conformability to shape, uniform formability, and FPC finished appearance wrinkles. A release film with improved adhesion and an FPC manufacturing method using the same are provided.

Claims (6)

  A release film having a first layer composed of a first thermoplastic resin, wherein the linear expansion coefficient of the first layer is 2 to 7% in a temperature range of 160 to 185 ° C. A release film characterized by that.   The release film according to claim 1, further comprising a second layer on at least one side of the first layer.   3. The release film according to claim 2, wherein the second layer is composed of a second thermoplastic resin different from the first thermoplastic resin.   The release film according to any one of claims 1 to 3, wherein the first thermoplastic resin contains polymethylpentene and polybutylene terephthalate.   The release film according to claim 3, wherein the second thermoplastic resin has a softening point of 50 to 160 ° C. 5. A method for producing a flexible printed wiring board, wherein the release film according to any one of claims 1 to 4, an adhesive film, and a laminated board are laminated in this order. Method.