JP4845233B2 - Release film for printed circuit board manufacturing - Google Patents

Description

  The present invention relates to a release film used in a hot press molding process when manufacturing a flexible printed wiring board.

  In recent years, with the rapid progress of electronic devices, as the degree of integration of ICs increases, printed wiring boards have been frequently used for the purpose of meeting demands for higher accuracy, higher density, and higher reliability. As this printed wiring board, there is a single-sided printed wiring board, a double-sided printed wiring board, a multilayer printed wiring board, and a flexible printed wiring board, and in particular, an insulating layer is integrated between three or more conductors, The field of application of multilayer flexible printed wiring boards (hereinafter referred to as FPC) has expanded in that any conductor layers and leads of electronic components to be mounted can be connected to any conductor layers.

  In the FPC manufacturing process, a heat-resistant resin film with adhesive (generally a polyimide film) is used on an insulating substrate, for example, on a flexible circuit board having a predetermined circuit on the polyimide resin film surface for the purpose of insulation and circuit protection. It is covered with a certain cover lay (hereinafter referred to as CL) and molded by press lamination through a release film. Further, for the purpose of improving strength, a reinforcing plate (generally a thick count polyimide film) is similarly press-laminated on the connector portion and the like. In these manufacturing processes, a mold release film that has excellent mold release properties with respect to FPC materials and press plates, conformability to shapes, uniform formability, finished appearance of FPC, and plating on circuits in subsequent processes is required. It has been.

Under such circumstances, a polyester (PET) film imparted with appropriate surface roughness by using inert additive particles taking advantage of its heat resistance has been proposed as a similar release film (Patent Document 1). . Since the PET film has a high melting point of about 260 ° C., it exhibits excellent heat resistance even in CL press molding. However, in recent years, from the viewpoint of FPC productivity, there is a tendency to increase the press temperature at the time of molding, and in this case, there is a problem that the release property between the release film and the FPC material becomes insufficient.
JP 2002-252458 A

  The present invention has been made in view of the above circumstances, and the problem to be solved is that, while satisfying required characteristics such as FPC finished appearance and plating property, in a reinforcing plate pasting process (heating press) during FPC manufacturing, An object of the present invention is to provide a release film for FPC production having excellent releasability from a press plate and an FPC material that could not be expressed by a polyester film.

  As a result of intensive studies in view of the above problems, the present inventors have found that the above problems can be easily solved by a film having a specific configuration, and have completed the present invention.

That is, the gist of the present invention is a film having a coating layer containing 10 to 90% by weight of polyvinyl alcohol and a release agent on both sides of the polyester film, and the water droplet contact angle on the surface of the coating layer is 80 to 80%. It exists in the mold release film for printed circuit board characteristics characterized by being the range of 120 degree | times.

Hereinafter, the present invention will be described in more detail.
As the polyester constituting the polyester film of the present invention, typically, for example, polyethylene terephthalate in which 80 mol% or more of the structural unit is ethylene terephthalate, and 80 mol% or more of the structural unit is ethylene-2,6-naphthalate. Specific polyethylene-2,6-naphthalate and poly-1,4-cyclohexanedimethylene terephthalate in which 80 mol% or more of the structural unit is 1,4-cyclohexanedimethylene terephthalate. Other examples include polyethylene isophthalate and polybutylene terephthalate.

  Examples of copolymer components other than the above-described dominant components include diol components such as diethylene glycol, propylene glycol, neopentyl glycol, polyethylene glycol, and polytetramethylene glycol, isophthalic acid, 2,7-naphthalenedicarboxylic acid, and 5-sodium dicarboxylic acid. Ester-forming derivatives such as diasulfoisophthalic acid, adipic acid, azelaic acid, sebacic acid and oxymonocarboxylic acid can be used. Further, as the polyester, in addition to a homopolymer or a copolymer, a small proportion of a blend with another resin can also be used.

  For the purpose of imparting stable release performance to the polyester film of the present invention, a coating layer is appropriately provided in order to make the water droplet contact angle on the film surface a specific range. Below, the method of formation of the coating layer for making the water drop contact angle of the polyester film of this invention into a specific range is demonstrated.

  In the present invention, a method of adjusting the water droplet contact angle to a specific range by mixing and blending polyvinyl alcohol and a release agent in an appropriate ratio in the coating layer is preferably used. If polyvinyl alcohol is not included in the coating layer, the water droplet contact angle exceeds 120 degrees, and the release component is likely to be transferred from the film surface (coating layer) to the FPC material surface during press processing. Tends to be disturbed. On the other hand, if the release agent is not contained in the coating layer, the water droplet contact angle is less than 80 degrees, and it becomes difficult to release from the FPC or the press plate in press working, which tends to hinder the suitability for processing in this application. There is.

  The release agent used in the coating layer is not limited to the following, and examples thereof include a fluorine-based acrylic resin, a long-chain alkyl compound, silicone, and wax. These compounds can also be used in combination.

  Further, in the coating layer, it is preferable to use a crosslinking agent in combination as long as the gist of the present invention is not impaired. Specific examples include urea-, melamine-, guanamine-, acrylamide-, polyamide, methylolated or alkylolated. System compounds, oxazoline compounds, epoxy compounds, aziridine compounds, block polyisocyanates, silane coupling agents and the like. These crosslinking components may be previously bonded to the binder polymer.

  Further, for the purpose of improving the adhesion and slipperiness of the coating layer, inert particles may be contained, and specific examples include silica, alumina, kaolin, calcium carbonate, titanium oxide, organic particles, and the like.

  Furthermore, as long as it does not impair the gist of the present invention, an antifoaming agent, a coating property improver, a thickener, an organic lubricant, an antistatic agent, an antioxidant, an ultraviolet absorber, a foaming agent, a dye, etc. May be contained.

Regarding the total of polyvinyl alcohol in the coating layer constituting the release film for producing a printed circuit board in the present invention, it is preferable that the following formula (1) is satisfied.
10 ≦ W ≦ 90 (1)
(In the above formula, W represents the weight% of polyvinyl alcohol in the coating layer constituting the release film for producing a printed circuit board)

  Manufactures a release film for printed circuit board production by applying a coating solution prepared by using the above-described series of compounds as a solution or dispersion on a polyester film with a solid concentration of about 0.1 to 50% by weight as a guide. It is preferable to do this.

  Furthermore, in the case of in-line coating, the above-mentioned series of compounds is used as an aqueous solution or water dispersion, and printed in the manner of applying a coating solution adjusted to a solid content concentration of about 0.1 to 50% by weight on a polyester film. It is preferable to produce a release film for producing a substrate. Moreover, in the range which does not impair the main point of this invention, a small amount of organic solvents may be contained in the coating liquid for the purpose of improving dispersibility in water, improving film-forming properties, and the like. Only one type of organic solvent may be used, or two or more types may be used as appropriate.

Although there is no restriction | limiting in the application quantity (after drying) of the coating layer provided on a polyester film regarding the release film for printed circuit board manufacture in this invention, Usually 0.005-1g / m < ² >, Preferably 0.005-0 The range is 0.5 g / m ² . If the coating amount is less than 0.005 g / m ² , the uniformity of the coating thickness may be insufficient. On the other hand, when it coats exceeding 1 g / m < ² >, malfunctions, such as a slipperiness fall and blocking, may arise.

  The water droplet contact angle of the polyester film of the present invention needs to be 80 to 120 degrees. The upper limit of the water droplet contact angle is preferably 117 degrees, and more preferably 115 degrees. When the water droplet contact angle exceeds 120 degrees, the release component is likely to be transferred from the film surface (coating layer) to the FPC material surface in the press working, and the plating property in the subsequent process tends to be hindered. On the other hand, when the water droplet contact angle is less than 80 degrees, the target peelability tends to be not obtained.

  Although the thickness of the polyester film of the present invention is not particularly limited, it is usually 10 to 100 μm, preferably 15 to 75 μm, and more preferably 20 from the viewpoint of moderate elasticity from the viewpoint of workability during press working and avoiding wrinkles. It is in the range of ˜50 μm.

  The polyester film of the present invention may be a multilayer film of two or more layers as long as it does not exceed the gist of the present invention. For example, a layer containing almost no inert particles is laminated to reduce the manufacturing cost or improve the strength. There is no problem.

  In the method for producing a polyester film of the present invention, a polymer blended in a predetermined manner is generally melted and extruded, and then stretched at least in a uniaxial direction according to a roll stretching method, a tenter method, or the like. In order to appropriately satisfy mechanical strength and thermal dimensional stability, it is preferable to use a biaxial stretching method and a heat treatment method in combination.

Here, an example in the case of using biaxial stretching will be described in detail.
First, the raw materials are blended and supplied to an extruder, and after melt-kneading, the molten polymer is usually guided to a T-die and extruded into a slit shape. Next, the molten sheet extruded from the die is rapidly cooled and solidified on the rotary cooling drum so that the temperature is equal to or lower than the glass transition temperature, thereby obtaining a substantially amorphous unoriented sheet. In this case, in order to improve the planar uniformity and cooling effect of the sheet, it is preferable to improve the adhesion between the sheet and the rotary cooling drum, and in the present invention, an electrostatic application adhesion method is preferably employed. Next, the obtained sheet is stretched in a biaxial direction to form a film. The surface irregularities of the polyester film of the present invention are generated by such stretching.

  First, the unstretched sheet is stretched under the conditions of a stretching temperature of usually 70 to 150 ° C., preferably 75 to 130 ° C., a stretching ratio of usually 2.5 to 6.0 times, preferably 3.0 to 5.0 times. Stretch in one direction (longitudinal direction). A roll and tenter type stretching machine can be used for such stretching. Furthermore, at a stretching temperature of usually 75 to 150 ° C., preferably 80 to 140 ° C., usually orthogonal to the first stage under conditions of a stretching ratio of 2.5 to 6.0 times, preferably 3.0 to 5.0 times. The film is stretched in the direction (transverse direction) to obtain a biaxially oriented film. For such stretching, a tenter type stretching machine can be used. A method of performing the above-mentioned unidirectional stretching in two or more stages can also be adopted, but in this case as well, it is preferable that the final stretching ratio falls within the above-described range. Further, the unstretched sheet can be simultaneously biaxially stretched so that the area magnification is 7 to 30 times. Next, heat treatment in the tenter is usually performed at 200 to 250 ° C., preferably 220 to 240 ° C., for 1 second to 3 minutes. In this heat treatment step, relaxation of 0.1 to 30% in the transverse direction and / or the longitudinal direction is performed in the zone of the highest temperature of the heat treatment and / or the cooling zone immediately before the heat treatment outlet, in order to impart thermal dimensional stability. Is preferable. In particular, it is preferable to perform 1-30% relaxation in the lateral direction.

In the above, a coating layer is provided on the film (both sides) after longitudinal stretching.
As a method of providing the coating layer, a conventionally known coating method such as reverse gravure coating, direct gravure coating, roll coating, die coating, bar coating, curtain coating or the like can be used. Regarding the coating method, there is a description example in “Coating method” published by Yasuharu Harasaki in 1979.

  In the present invention, the drying and curing conditions for forming the coating layer on the polyester film are not particularly limited. However, in general, the post-coating process is performed at 70 to 280 ° C. for 3 to 200 seconds. It is better to perform heat treatment.

  Moreover, you may use together heat processing and active energy ray irradiation, such as ultraviolet irradiation, as needed. The polyester film constituting the release film for producing a printed board in the present invention may be subjected to surface treatment such as corona treatment or plasma treatment in advance.

  The polyester film of the present invention is suitably used as a release film for hot press molding in the production of a flexible printed wiring board, taking advantage of its characteristics.

  According to the present invention, in the reinforcing plate pasting process (heating press) at the time of FPC production, while satisfying required characteristics such as FPC finished appearance and plating property, a press plate that could not be expressed with a conventional polyester film and It is possible to provide a release film for producing FPC having excellent releasability with respect to an FPC material, and its industrial value is high.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to these Examples, unless the summary is exceeded. In addition, the various physical property in this invention, its measuring method, and a definition are as follows. In Examples and Comparative Examples, “parts” and “%” mean “parts by weight” and “% by weight”, respectively.

(1) Average particle size of additive (μm)
The particle size was measured by a sedimentation method based on Stokes' resistance law using a centrifugal sedimentation type particle size distribution analyzer SA-CP3 manufactured by Shimadzu Corporation. The average particle diameter was determined by using a value of 50% of integration (volume basis) in the equivalent spherical distribution of particles obtained by measurement.

(2) Intrinsic viscosity of polyester (dl / g)
A mixed solvent of phenol / tetrachloroethane: 50/50 (weight ratio) was added to 1 g of polyester at a ratio of 100 ml, and the mixture was measured at 30 ° C.

(3) Centerline average roughness Ra (μm)
It measured using the universal surface shape measuring device SE-3F made from Kosaka Laboratory. The measurement was performed 7 times on one side (cast surface) of the sample under the following conditions, and an average value of 5 points excluding the maximum and minimum 2 points was taken.
・ Tip tip diameter: 2 μm ・ Measurement force: 30 mgf
・ Measurement length: 2.5 mm ・ Cutoff value: 0.08 mm

(4) Thermal contraction rate (%)
The film was cut into a length of 15 mm and a length of 150 mm in the longitudinal direction (MD) or the width direction (TD), marked at intervals of 100 mm, and heat-treated in a hot air circulating oven at 180 ° C. for 5 minutes in a tensionless state. The marking interval before heat treatment: a and the marking interval after heat treatment: b were measured, and the thermal shrinkage rate was determined by the following formula. The number of measurements n was 3, and the average value was taken.
Thermal contraction rate (%) = (ab) × 100 / a

(5) Water drop contact angle (°)
2 μL of ion-exchanged water was dropped, and the water droplet contact angle on the film surface after 1 minute was measured by a θ / 2 method using a contact angle measuring device (CA-A type manufactured by Kyowa Interface Science Co., Ltd.).

(6) Process suitability test by hot press-About deposits on the hot press plate.
(Press release) Film / FPC / (Release) Film stacked in this order was pressed with a hot platen (170 ° C., 30 kg / cm 2, 60 minutes), then pressure-cooled to 50 ° C., then: The items were evaluated.

"FPC releasability"
A: Release from FPC was easy.
X: Release from FPC was difficult, and a problem was recognized in processability.

"Press board releasability"
○: Adhesion with a hot plate was not recognized and was good.
X: Adhesion to the hot plate occurred, and there was a problem in processability.

"Plating properties"
○: 90% or more of the required plating area is plated ×: The plating is less than 90% of the required plating area

Examples of compounds constituting the coating layer are as follows.
Fluorine-based acrylic resin In a glass reaction vessel, 80.0 g of CF ₃ (CF ₂ ) _n CH ₂ CH ₂ OCOCH═CH ₂ (n = 5 to 11, n average = 9), acetoacetoxyethyl methacrylate 20. 0 g, 0.8 g of dodecyl mercaptan, 354.7 g of deoxygenated pure water, 40.0 g of acetone, 1.0 g of C ₁₆ H ₃₃ N (CH ₃ ) ₃ Cl and C ₈ H ₁₇ C ₆ H ₄ O (CH ₂ CH ₂ O) 3.0 g of nH (n = 8) was added, 0.5 g of azobisisobutylamidine dihydrochloride was added, and a copolymerization reaction was carried out at 60 ° C. for 10 hours with stirring in a nitrogen atmosphere. Obtained.

A polyethylene terephthalate chip containing 0.07% of amorphous silica particles having an average particle diameter of 2.4 μm and having an intrinsic viscosity of 0.66 is directly charged into a vented twin screw extruder and melted and kneaded at 270 ° C. The melt was extruded into a slit shape via a T-die and cooled on a cooling drum at 30 ° C. to obtain an unstretched sheet. Next, the non-stretched sheet was mixed at a ratio of 50:30:20 on both sides of a film obtained by stretching the unstretched sheet 3.3 times in the longitudinal direction at 82 ° C. at a ratio of polyvinyl alcohol: fluorinated acrylic resin: hexamethoxymethylmelamine = 50: 30: 20. The applied liquid was applied by a bar coating method, guided to a tenter, stretched 4.1 times in the transverse direction at 120 ° C., heated in steps, and then heat treated at 232 ° C. for 3 seconds. Next, under a 180 ° C. atmosphere, 2% relaxation treatment (to narrow the tenter rail width) was performed in the width direction. Finally, a biaxially oriented polyester film having a thickness of 38 μm was obtained in which a coating layer having a coating amount (after drying) of 0.02 g / m ² was provided on both sides.

The coating amount on both surfaces was the same as in Example 1, except that the blending ratio of the coating layer was changed to the ratio of polyvinyl alcohol: fluorinated acrylic resin: hexamethoxymethylmelamine urea copolymer = 35: 45: 20. A biaxially oriented polyester film having a thickness of 38 μm and having a coating layer of 0.02 g / m ² (after drying) was obtained.

The coating amount on both sides was the same as in Example 1 except that the blending ratio of the coating layer was changed to the ratio of polyvinyl alcohol: fluorine acrylic resin: hexamethoxymethylmelamine urea copolymer = 70: 10: 20. A biaxially oriented polyester film having a thickness of 38 μm and having a coating layer of 0.02 g / m ² (after drying) was obtained.

(Comparative Example 1)
In Example 1, a biaxially oriented polyester film having a thickness of 38 μm was obtained in the same manner except that the coating layer was not provided.

(Comparative Example 2)
In Example 1, the coating layer was mixed in the same manner except that the blending ratio of the coating layer was changed to a ratio of polyvinyl alcohol: fluorinated acrylic resin: hexamethoxymethylmelamine urea copolymer =-(not blended): 80: 20. A biaxially oriented polyester film having a thickness of 38 μm, having a coating layer having a coating amount (after drying) of 0.02 g / m ² , was obtained.

(Comparative Example 3)
The coating amount on both surfaces was the same as in Example 1, except that the blending ratio of the coating layer was changed to the ratio of polyvinyl alcohol: fluorinated acrylic resin: hexamethoxymethylmelamine urea copolymer = 1: 79: 20. A biaxially oriented polyester film having a thickness of 38 μm and having a coating layer of 0.02 g / m ² (after drying) was obtained.
The obtained results are summarized in Table 1 below.

The film of the present invention can be suitably used as a release film used in, for example, a hot press molding process when manufacturing a flexible printed wiring board.

Claims (1)

It is a film having a coating layer containing 10 to 90% by weight of polyvinyl alcohol and a release agent on both sides of the polyester film, and the water droplet contact angle on the coating layer surface is in the range of 80 to 120 degrees. A release film for producing printed circuit boards.