TWI476103B - A release film and a method of manufacturing a flexible printed wiring board using the release film - Google Patents

Description

Release film and method for producing flexible printed wiring board using the release film

The present invention relates to a release film used in the production of a flexible printed wiring board or a rigid flexible printed wiring board. Further, the present invention relates to a method of producing a flexible or rigid flexible printed wiring board using the release film.

The flexible printed wiring board (hereinafter referred to as FPC) is formed of a flexible circuit member provided with a predetermined circuit on the surface of an insulating base material such as a polyimide film. In the FPC system, the flexible circuit member is usually covered with a coating layer of a heat-resistant resin film to which an adhesive is applied, and is insulated and circuit-protected, and a release film is present and pressed and laminated by a press machine.

In this way, the manufacturing system requires a good release property between the FPC and the pad of the press machine, and the coating layer is sufficient to follow the irregularities adhering to the flexible circuit member, and the pressure to the FPC is uniform. Wait. In other words, it is required to have excellent "formability" in FPC which is excellent in release property, shape followability, and void-free property to uniform pressure of the entire FPC.

Other characteristics required for the release film include a small amount of wrinkles in the appearance of the FPC, a small flow rate of the adhesive of the coating layer, and a small amount of leakage of the adhesive on the end surface of the coating layer during pressurization, and no conductor portion. Contamination, the adhesion of the subsequent engineering to the circuit is good, and the release film after use is not damaged. The benchmark for the evaluation of these characteristics is in the JPCA specification in Japan.

SUMMARY OF THE INVENTION An object of the present invention is to provide a release film which has improved properties such as insufficient release property and shape followability while having the same characteristics as those of a release film which is generally known for use in FPC production. Further, the present invention provides a method of producing an FPC using the release film. This release film is superior in tear strength, elongation, tensile strength, and cost as compared with a conventional release film.

The present invention provides a release film which is a release layer having a thermoplastic resin having a Viscoelasticity rate of 50 to 250 MPa at a temperature of 180 °C. A thermoplastic resin is preferably a polybutylene terephthalate resin. The release film is preferably a buffer layer composed of a thermoplastic resin different from the release layer provided on the release layer and one side thereof. Further, it is also preferable to provide a sub-separation layer (second release layer) on the opposite side to the release layer side of the buffer layer.

According to another aspect of the present invention, in the manufacture of a flexible or rigid flexible printed wiring board, the order of the flexible circuit member, the coating layer (adhesive film similar to the coating layer), and the release film are overlapped. A method of manufacturing a printed wiring board including a flexible printed wiring board and a rigid flexible printed wiring board by pressure stacking.

Detailed description of the invention

A more detailed description of the invention follows. In addition to FPC (Flexible Printed Wiring Board), printed wiring boards are called rigid flexible printing. Wiring board. The manufacturing process of the printed wiring board is also the same as that of the FPC, and the hard flexible printed circuit board is coated with an adhesive film similar to the coating layer, and these can be pressure-stacked using the release film of the present invention to produce printing. Wiring board. Therefore, the following description is related to the FPC.

In the manufacture of FPC, it is necessary to have good release properties in the release film. If the release property is low, peeling after the pressure-stacking treatment causes a problem that the film adheres to the FPC and is broken, and the FPC circuit is peeled off.

(release layer)

The resin used for the release layer of the film is a thermoplastic resin having a viscoelasticity (Pa) at a temperature of 180 ° C of 50 to 250 MPa, preferably 60 to 200 MPa, more preferably 70 to 150 MPa. When the viscoelasticity ratio is smaller than this, the surface of the release layer resin is softened and the fluidity becomes high at the required pressurization temperature, so that it is fused to the copper foil portion of the FPC to deteriorate the release property. In addition, when the viscoelasticity is larger than the above range, the release property is good, but the flow rate of the adhesive adhering to the coating layer increases, and the shape followability decreases.

The specific thermoplastic resin system is preferably a polybutylene terephthalate resin. Examples of such a resin include polybutylene terephthalate (hereinafter referred to as PBT) or a copolymer thereof. Copolymers of polybutylene terephthalate and polytetramethyl glycol are preferred in the copolymer system. The copolymerization ratio of the copolymer is not particularly limited.

It is preferable to provide a buffer layer on one side of the release layer. Further, it is preferable to provide a sub-separation layer on the opposite side to the release layer side of the buffer layer. related It is also better to use the same resin for the two release layers.

The thickness of the release layer is 10 to 100 μm, preferably 15 to 50 μm. If the release layer is thinner than this, the release layer will be broken after the pressure is laminated, and the release layer resin remains on the FPC side when the FPC is separated from the release film. On the other hand, when it is thicker than the above range, the shape followability is poor, and the flow rate of the adhesive adhering to the coating layer is increased.

The release layer system is preferably a 10-point average roughness (Rz) of 10 to 45 μm. The surface roughness of the release layer is obtained by a generally known surface treatment such as emboss treatment. In the case of embossing treatment, it is possible to use a high temperature, a high pressure, a method of passing a film through a mat roll, or a film which is produced by a die, and a contact roller is pressed against embossing cooling. The method of the drum, etc. The embossing treatment temperature is 120 to 220 ° C, and the softening temperature of the ideal release layer resin is preferably 140 to 190 ° C. The pressure at the time of embossing is 50 to 200 kgf/mm ² (gauge pressure), preferably 60 to 120 kgf/mm ² . The roughness of the rough roll for embossing has a 10-point average roughness (Rz) of 0.05 μm to 1 mm. The surface roughness of the release layer is Rz = 10 to 45 μm, preferably 15 to 43 μm. If the surface roughness is smaller than the aforementioned range, cracking of the release layer occurs. On the other hand, if it exceeds the above range, the embossing pattern is transferred to the FPC.

(The buffer layer)

The buffer layer of the release film is preferably a thermoplastic resin different from the release layer. As a resin system, softening temperature (Weiss softening temperature) 50~160°C It is ideal. When the softening temperature of the resin is less than 50 ° C, the resin is oozing out from the end surface of the release film at the time of pressurization, and adheres to the heating plate, which may cause secondary pollution in the secondary process. On the other hand, when it exceeds 160 ° C, the moldability falls, and a void occurs in the fine portion of the FPC. The thickness of the buffer layer is not particularly limited.

Specific examples of the resin include a polyethylene resin, a polypropylene resin, and an ethylene-methyl acrylate (hereinafter referred to as EMMA) resin. Although it is preferable to have an adhesive resin between the release layer and the buffer layer, if it does not exist, the bleeding of the film end face is less desirable.

(Manufacturing method of release film)

In the release film of the present invention, a coextrusion lamination method, a extrusion lamination method, a dry lamination method, or the like can be used for the production of a multilayer film, and a conventionally known lamination method is preferred.

The film system of the present invention is used as a release film in the production process of FPC as in the case of a generally known release film. In this press-stacking system, for example, the SUS plate, the paper, the release film, the coating layer (adhesive film), the flexible circuit member (single-sided), and the SUS plate are placed in an overlapping configuration between the heating plates. After heating and pressing under the specified conditions, the material is post-hardened. In general, the release film, the coating layer, and the flexible circuit member may be laminated in reverse. The release film of the present invention is a short-time forming method (generally referred to as a pressurized pressurizing method for Hot-Hot) and a pressurized pressurizing method called Cold-Hot. use.

Example

Hereinafter, the present invention will be described in more detail by way of examples and comparative examples. The invention is not limited by these examples. The raw materials used in the examples and comparative examples are shown below.

Release resin

. Copolymer of polybutylene terephthalate and polytetramethyl glycol (PBT resin): trade name 5505S (manufactured by Mitsubishi Engineering Plastics Co., Ltd.) viscoelasticity rate 100MPa. Copolymer of polybutylene terephthalate and polytetramethyl glycol (PBT resin): trade name 5510S (manufactured by Mitsubishi Engineering Plastics Co., Ltd.) viscoelasticity rate 70MPa. Polybutylene terephthalate (PBT resin): trade name 5020F (manufactured by Mitsubishi Engineering Plastics Co., Ltd.) viscoelasticity 110MPa. Copolymer of polybutylene terephthalate and sebacic acid (PBT resin): trade name 1200D (manufactured by Toray Co., Ltd.) viscoelasticity rate 30 MPa. Polybutylene terephthalate (PBT): trade name 1200S (Japan Toray (TORAY) company) viscoelasticity rate 110MPa. Polybutylene terephthalate and added filler (cerium oxide) (PBT resin): 5020SCAMD24 (manufactured by Mitsubishi Engineering Plastics Co., Ltd.) viscoelasticity 300MPa

Buffer layer resin

. Ethylene-methyl acrylate copolymer (EMMA): trade name ACRYFT WH102 (manufactured by Sumitomo Chemical Industries, Ltd.) softening temperature 73 ° C. Polyethylene (LDPE): trade name Smicasen L211 (manufactured by Sumitomo Chemical Industries, Ltd.) softening temperature 100 ° C. Polypropylene: Nobren FS2011DG2 (manufactured by Sumitomo Chemical Industries, Ltd.) softening temperature 154 ° C. Ethylene-vinyl acetate copolymer (EVA): trade name Ebatate K5010 (manufactured by Sumitomo Chemical Co., Ltd.) softening temperature 41 ° C, and softening temperature means Vicat softening temperatur (JIS K6730-1981)

<Examples 1 to 6>

Each of the two extruders was supplied to the release layer resin and the buffer layer resin shown in Table 1, and was subjected to co-extrusion by a two-layer mold to form a release multilayer film (Examples 1 to 4).

Further, each of the three extruders was supplied to the release layer resin, the buffer layer resin, and the sub-separation layer resin shown in Table 1, and a three-layer mold was co-extruded to form a release multilayer film (Example 5, 6).

The obtained release multilayer film and the flexible printed wiring board (FPC) were heated and pressurized at 185 ° C, 5 MPa, and 2 minutes using a one-stage press. Then, these were taken out and evaluated about the item mentioned later. The results are shown in the first table.

<Comparative Examples 1 to 2>

The resin shown in the second table was supplied by one extruder, and extruded into a single layer mold to form a release single layer film. The obtained release single-layer film and the flexible printed wiring board (FPC) were heated and pressurized at 175 ° C, 4 MPa, and 60 minutes using a multi-stage press. Next, the results of the same evaluation as described above are shown in the second table.

<Examples 7 to 11>

Using the resin shown in Table 3, a release film was co-extruded in a two-layer mold in the same manner as in Example 1. The embossing treatment was applied offline (temperature 170 ° C, pressure 100 kgf / mm ² (gauge pressure)).

The obtained release film and FPC were heated and pressurized at 175 ° C, 5 MPa, and vacuum for 60 minutes using a multi-stage press. Performing phase with the foregoing The results of the same evaluation are shown in Table 3.

<Comparative Examples 3 to 5>

A release film was produced in the same manner as in Example 1 except that the resin shown in Table 3 was used. Among these, the embossing treatment was carried out in addition to Comparative Example 4. The results of the same evaluation as described above are shown in the third table.

<Examples 12 to 14 and Comparative Examples 6 to 8>

The resin shown in Table 4 was co-extruded into a release film by a two-layer mold in the same manner as in Example 1. The obtained release film was treated and evaluated in the same manner as described above. The results are shown in Table 4. The viscoelasticity of the release layer of the release film was measured using a viscoelasticity measuring apparatus of "DMS-210 type manufactured by Seiko Instruments Inc.".

In addition, the evaluation is based on the following items and standards in accordance with the JPCA specifications (Design Guidebook. Single-sided and double-sided flexible printed wiring boards. JPCA-DG02).

The surface roughness of the release layer of the release film was measured by HANDYSURF graph E-30A (manufactured by Tokyo Seimitsu Co., Ltd.).

(evaluation project)

. Formability (by 7.5.3.3 bubbles)

○: void generation rate less than 2.0% ×: void generation rate 2.0% or more

. CL (coating layer) adhesive flow rate (coated by 7.5.3.6) The outflow of the adhesive and the bleed of the coated coating)

○: Flow rate less than 150 μm ×: flow rate 150 μm or more

. The length of the spot on the end face of the release film (measured by the length of the resin stain on the end face of the film 4)

○: less than 1.2 mm ×: 1.2 mm or more

. Complete appearance wrinkle (creased by 7.5.7.2)

○: wrinkle occurrence rate less than 2.0% ×: wrinkle occurrence rate 2.0% or more

. Release property (rupture of release film) (attachment of surface by 7.5.7.1)

○: incidence of rupture less than 2.0% ×: rupture rate 2.0% or more

. Plating adhesion (more than 90% of the necessary plating area is adhered to the plating as a good product: the appearance of electroplating by 7.5.4)

○: Good product is 98% or more ×: Good product is less than 98%

Industrial availability

When the FPC is produced by using the release film (single layer or multilayer) of the present invention, it is possible to maintain the release property, the shape followability, the uniform formability, the plating adhesion, and the appearance wrinkles when the FPC is completed. The characteristics and one side are excellent in the release property and formability at the time of excellent pressure-bonding which is not obtained by the prior release single-layer film. Further, the surface of the release layer is treated by embossing to improve the release property at the time of pressurization. Further, the release film of the present invention is excellent in tear strength, elongation, tensile strength, and cost, and is also superior to a generally known release film. Moreover, it is also preferable to manufacture a hard flexible printed wiring board as a release film.

Claims (5)

A release film is a pressure-release engineering release film for manufacturing a flexible or rigid flexible printed wiring board comprising a release layer, characterized in that the release layer is made of a paste having a temperature of 180 ° C a polybutylene terephthalate resin having a Viscoelasticity rate of 50 to 250 MPa and having a thickness of 15 to 50 μm; a buffer layer provided on one side of the release layer, the buffer layer being a release layer and a release layer It is composed of a different thermoplastic resin, and the buffer layer resin has a Vicat softening point temperature of 50 to 160 °C. The release film according to the first aspect of the invention, wherein the release film is provided on the side opposite to the release layer side of the buffer layer. The release film according to the first aspect of the invention, wherein the surface of the release layer has a 10-point average roughness (Rz) of 10 to 45 μm. A method for producing a flexible printed wiring board, characterized in that in the manufacture of a flexible printed wiring board, the flexible circuit member, the coating layer, and the release film of claim 1 or 2 are in this order Overlap and pressure stacking process. A method of manufacturing a rigid flexible printed wiring board, characterized in that, in the manufacture of a rigid flexible printed wiring board, a rigid flexible circuit member, an adhesive film, and a release type of claim 1 or 2 The order of the films overlaps and the pressure is stacked.