JP5023765B2 - Release film and circuit board manufacturing method - Google Patents

Description

  The present invention relates to a release film and a method for producing a circuit board using the release film.

In the manufacturing process of a circuit board such as a flexible printed wiring board (hereinafter referred to as FPC), an insulating base material, for example, a flexible circuit board having a predetermined circuit on the surface of a polyimide resin film is used for the purpose of insulation and circuit protection. A cover lay (hereinafter referred to as CL), which is a heat-resistant resin film with an adhesive, is coated with a release film, and then a metal plate is stacked and heat-molded (pressing process). In this manufacturing process, a metal plate (hereinafter referred to as a backing plate) with a fluororesin film on its surface is used to improve the releasability of the release film with a mating material with a view to working efficiency. Releasability is required. In addition, regarding the relationship between the FPC and the release film, it is a matter of course that excellent release properties are required for the release film, and the adhesive flow from the CL end surface is sufficiently suppressed by sufficiently following the unevenness of the FPC. Uniform pressure by enveloping the entire FPC (conformability to shape), Devoid of void by the uniform pressure on the entire FPC (hereinafter referred to as moldability), No appearance wrinkles on the finished FPC, It is required to have excellent plating on the circuit.
On the other hand, in order to improve releasability, for example, Patent Document 1 describes releasability from a circuit board, but releasability from a backing plate is insufficient, and a releasable film is applied. There were problems in actual work because man-hours were required, such as requiring manual labor to peel off the plate. In recent years, the circuit width of circuit boards has been narrowed. For example, it has been pointed out that when the circuit width is 100 μm or less, the releasability from the release film is poor.
As for the releasability with the circuit board, after the pressing process, the release film must be peeled off from the circuit board by hand, and the required releasability is not so severe, but the releasability with the backing plate is After releasing the press, the release film must be peeled off naturally from the backing plate, so that the required release properties are very severe.
Further, in view of such mold releasability, the circuit board manufacturing process has been solved by cooling the release film and the circuit board which are bonded by pressing for a certain period of time after the pressing. However, productivity is reduced by the time required for cooling.
JP 2005-178323 A

  The object of the present invention is excellent with respect to shape conformability, uniform moldability, plating property, and FPC-finished appearance wrinkles. Furthermore, after heat pressing, the circuit board and the release film can be peeled off in a relatively short time (release). The present invention provides a mold release film having a good mold release property in a very short time even when peeling a backing plate and a mold release film, and a method for producing a circuit board using the mold release film. It aims at improving the release property of the release film with respect to a circuit board with a narrow circuit width especially.

The present invention is a release film having an emboss used in a circuit board pressing process, and the embossed surface roughness (Rz: 10-point average roughness) of the release film is 5 μm before the pressing process. The release film is 20 μm or less and 2 μm or more and 8 μm or less after the pressing step.
In a more preferred embodiment, the resin constituting the release surface of the release film is a resin having a crystallization temperature higher than the press temperature of the circuit board pressing step, and constituting the release surface of the release film. The crystallization temperature is 170 ° C. or higher, the resin constituting the release surface of the release film is 4-methyl 1-pentene polymethylpentene resin, and the release surface of the release film is constituted. The softening point TS (° C.) of the resin surface is 48 or more and 56 or less, the release film is a multilayer film of 3 or more layers, and at least one of the intermediate layers is composed of an ethylene resin or an acrylic resin. It is a release film which is a layer.
Further, in the process of producing a release film through a cooling roll, the first roll and / or the touch roll is provided between the first roll and the touch roll that are paired with the molten resin extruded into a film by extrusion molding. The surface temperature T1 (° C.) of the film having an embossed shape on the roll surface and immediately before being sandwiched between the first roll and the touch roll is Tc-60 <T1 <Tc-20 (where T _C is the release film) The surface temperature T2 (° C.) of the film immediately before being taken up by the cooling roll is Tc−150 <T2 <170, and the surface of the touch roll. Is a rubber roll, and in the step of embossing the release film produced by extrusion molding using a roll having an emboss shape, Roll surface temperature T0 with shape _{(℃), T C -40 <} T0 <T C +10 ( where, T _C is the crystallization temperature of the resin constituting the release surface of the release film (° C.)) of The release film is within the range.
Moreover, it is the manufacturing method of the circuit board characterized by being manufactured using the said release film.

The embossed surface roughness (Rz: 10-point average roughness) of the release film having an emboss used in the circuit board pressing process of the present invention is 5 μm or more and 20 μm or less before the pressing process, and 2 μm or more after the pressing process. By setting the thickness to 8 μm or less, it is possible to improve the releasability between the circuit board and the backing plate after the circuit board pressing process, and not only the circuit board but also the release film is applied in the circuit board manufacturing process. Peeling naturally from the plate, a great reduction in man-hours is expected. Further, the release film of the present invention has excellent characteristics with respect to the circuit board in terms of uniform formability, plating property, and the absence of FPC finished appearance wrinkles. In addition, the product of the present invention improved the releasability, and was able to maintain sufficient anti-trackability even when the circuit width of the circuit board was 100 μm or less.
Moreover, when the release film of the present invention is used, a method for producing a circuit board with few occurrences of defects and the like can be provided.

<Surface roughness>
A release film having an emboss used in a circuit board pressing process, wherein the surface roughness of the embossing of the release film (Rz: 10-point average roughness) is 5 μm or more and 20 μm or less before the pressing process, The release film is 2 μm or more and 8 μm or less after the pressing step.
If the surface roughness (Rz) of the embossed release film before the pressing process is less than 5 μm, the film can be taken on a roll having an embossed surface (embossing roll) during embossing, or the releasability after pressing Becomes worse. In particular, when the backing plate or the circuit board and the release film are peeled off in a relatively short time after the heat pressing, the release property becomes worse on the backing plate side, or the release film is broken on the circuit board side. In addition, wrinkles are likely to occur and become a problem. On the other hand, if the thickness exceeds 20 μm, the adhesive from the CL end face will flow out from the gaps between the irregularities of the circuit board, and as a result, the exuded adhesive will harden, and the side of the circuit will be bearded, the plating property, etc. It becomes a problem. More preferably, they are 10 micrometers or more and 15 micrometers or less. In the invention of the present application, there was no problem in releasability even when the temperature of the release film at the time of peeling was 150 ° C., for example.
If the surface roughness (Rz) of the embossed release film after the pressing step is less than 2 μm, the film is taken on an embossing roll during embossing, or the release property after pressing becomes worse. In particular, if you try to peel off the backing plate or circuit board from the release film in a relatively short time after hot pressing, the release film will be hot and the release film will be worse or the release film will be torn. . In addition, wrinkles are likely to occur and become a problem. If it exceeds 8 μm, the adhesive from the CL end face will flow out from the gaps between the irregularities of the circuit board, resulting in problems such as whiskering and plating properties. In the release film of the present invention, there was no problem in release properties even when the temperature of the release film at the time of peeling was 150 ° C., for example.

  The influence of the unevenness after the pressing step is not particularly limited because Rz defining the height is dominant, but the average interval (Sm) of the unevenness of the release film is preferably 50 μm or more and 300 μm, More preferably, they are 80 micrometers or more and 250 micrometers or less. If Sm is in this range, the releasability is excellent, and problems such as generation of wrinkles and outflow of the adhesive from the CL end face through the uneven gaps are less likely to occur.

<Release layer resin>
It is preferable that the resin crystallization temperature of the layer constituting the release surface of the release film of the present invention (hereinafter referred to as the release layer) is higher than the press temperature in the circuit board pressing step. By using a resin in which the crystallization temperature of the resin in the release layer is higher than the press temperature in the pressing process of the circuit board, a more excellent effect can be obtained in terms of releasability.
Furthermore, the crystallization temperature of the resin in the release layer is 170 ° C. or higher, and a more excellent effect can be obtained in terms of releasability. In addition, the crystallization temperature of the resin of the release layer of this release film is defined by the crystallization peak top temperature.

The resin for the release layer of the present invention is not particularly limited. For example, polyester resins such as polyamide resin, polyacetal resin polybutene resin, polybutadiene resin, polypropylene resin, polyethylene resin, polybutylene terephthalate resin, polyethylene terephthalate resin, 4 -Methyl 1-pentene polymethylpentene resin etc. are mentioned. Of these, 4-methyl 1-pentene polymethylpentene is preferable in terms of releasability and shape conformability.
The crystallinity of the resin used in the release layer of the present invention is preferably 50% or more and 70% or less, more preferably 55% or more and 60% or less. A release film using a resin within the range of crystallinity, for example, can be sufficiently released from the backing plate even when the press release is performed immediately after pressing at a high temperature of 170 ° C. or higher. The peelability from the substrate is also good, and it is more effective for the problem that the adhesive from the CL end face flows out from the gaps between the projections and recesses and the conformal followability is insufficient.

<Interlayer resin>
The release film of the present invention is preferably a multilayer film having 3 or more layers. In that case, both outer layers are release layers and have releasability, and an intermediate layer having a function for various requirements is used. For example, the resin of the intermediate layer used for cushioning requirements preferably has a Vicat 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 a backing plate and the like, and there is a concern of secondary contamination in the next process. If it exceeds 160 ° C., the moldability is poor, and voids may occur in the details of the FPC. The thickness of the cushion layer 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.

  For each layer in the multilayer film of the present invention, antioxidants, slip agents, antiblocking agents, antistatic agents, ultraviolet absorbers, resin modifiers, colorants such as dyes and pigments, additives such as stabilizers, fluororesins Further, an impact resistance imparting agent such as silicon rubber and an inorganic filler such as titanium oxide, calcium carbonate, and talc may be contained. Moreover, an adhesive resin layer can be provided between the resin layers as necessary.

<Thickness of release layer>
The thickness of the release layer is 15 to 50 μm. Preferably 15-45 micrometers is desirable. When the thickness is less than 15 μm, the release layer is broken after press lamination, and when the FPC and the release film are separated, the release layer may remain on the FPC side. If it exceeds 50 μm, the shape following ability is deteriorated, and the flow amount of the adhesive adhering to the CL may be increased.

<Softening point of surface>
The softening point of the surface of the release layer T _S is defined at a temperature at which the needle has penetrated the release layer resin surface layer 10μm release film. T _S of the releasing resin layer before the pressing process for manufacturing a circuit board using the release film that has been embossed it is 48 ° C. or higher 56 ° C. or less. Within this range, it is more preferable in terms of releasability.

<Crystallinity>
Here, when the crystallization temperature of the release layer is increased, the release property tends to be improved. However, in order to further improve the release property, it is preferable to increase the crystallinity. For this purpose, it is necessary to adjust the conditions during embossing. At this time, those with a high crystallization temperature need to be embossed at a high temperature, but the treatment at a high temperature is applied to the embossing roll, and the transfer rate of the embossed shape becomes relatively low, so the crystallization degree is increased. It is necessary to adjust the conditions in consideration of the increase. The present invention is more preferable in these respects by adjusting the manufacturing conditions.

<Embossing>
The surface layer of the release film of the present invention is embossed inline or offline. Here, in-line embossing means embossing during the film production process by extrusion molding, and off-line embossing means embossing roll having embossing on the surface after producing the film by extrusion molding. Is used to emboss the film surface.
The embossing method is not particularly limited as long as the object of the present invention is satisfied and the effect is not impaired. For example, when embossing is performed offline, there is a method in which the film is passed through an embossing roll at high temperature and high pressure. In this case, the embossing temperature (embossing roll surface temperature) T0 (° C.) is T _C −40 <T0 <T _C +10 (where T _C is the crystallization temperature (° C. of the release layer resin) )). If the embossing temperature is less than the lower limit, the surface roughness after the pressing process may be less than 2 μm. If the embossing temperature exceeds the upper limit, the resin will be in a molten state, and the release film will be taken by the embossing roll during embossing. there is a possibility. The embossing pressure is not particularly limited, but is a linear pressure of 10 to 200 kgf / cm (gauge pressure), more preferably 30 to 120 kgf / cm. If the linear pressure is less than the lower limit, the uneven transfer by embossing becomes insufficient, and if it exceeds the upper limit, the film may be taken on the embossing roll. The temperature difference between the front and back surfaces of the embossing roll is preferably in the range of 0 ° C to 40 ° C. If the temperature difference exceeds 40 ° C., the film tends to be curled after embossing, which may make it difficult to use.

When embossing is performed in-line, there is a method of pressing a film coming out of a die against a roll having an emboss such as a touch roll. As an example, by using a roll having an embossed surface on the surface of the first roll and / or touch roll installed immediately after the extrusion to form a film of the extruded resin, it is melted from the die in the extrusion process. The released resin is sandwiched between the first roll and the touch roll, so that the embossed shape on the surface of the first roll and / or the touch roll is transferred to the surface of the resin film to be embossed to produce a release film. In this step, the surface temperature T1 (° C.) of the film immediately before being formed into a film by sandwiching the molten resin between the first roll and the touch roll is preferably Tc-60 <T1 <Tc-20. . Furthermore, the film surface temperature T2 (° C.) immediately before the film is taken up by a cooling roll (hereinafter referred to as a second roll) used to lower the temperature of the film is Tc−150 <T2 <170 ° C. preferable. Here, when T1 is lower than the lower limit, the cooling effect on the resin melted from the die is relatively high, and as a result, the crystallinity of the film is lowered and the mold release property may be deteriorated. If T1 exceeds the upper limit, the film is cooled and the crystallinity of the film tends to increase. However, the film is taken on a roll, or the uneven height of the embossed film is crushed in a later step. The surface shape of the transferred film may change with respect to the surface shape of the embossing roll, and the transfer rate may be lowered. Further, if T2 is lower than the lower limit, the film cooling effect is relatively high, and the crystallinity of the film is lowered and the releasability may be inferior. If T2 exceeds the upper limit, the film is the same as in T1. The film is softened and embossed, and the uneven height of the embossed film is crushed in a later process, and the surface shape of the transferred film changes relative to the surface shape of the embossing roll, resulting in a low transfer rate. There is a possibility.
T1 at this time is preferably maintained for at least about 1 second after the film in which the resin is extruded into a film by extrusion molding contacts the first roll. If the time is less than 1 second, the film is taken up by the second roll in a relatively soft state, and therefore, the film may be taken on the touch roll or the embossed surface of the film may be crushed. T2 is the temperature immediately before contacting the second roll from the moment when the film leaves the first roll when the film is taken from the first roll to the second roll. By adjusting the manufacturing conditions in this manner, the transfer rate of the surface shape of the transferred film with respect to the surface shape of the embossing roll can be as high as 80% or more.

  Since the touch roll can be uniformly transferred during embossing, a rubber roll whose surface is made of rubber is preferable. The material of the rubber roll is preferably ebonite, silicon (hardness 55 ° C. at room temperature), and the wall thickness range is 4 mm or more and 8 mm or less. If the lower limit is not reached, cushioning properties are lost and uniform transfer is not possible, and wrinkles may occur. When the upper limit is exceeded, the cooling efficiency of the rubber surface is deteriorated and the touch roll may be taken. Further, it is preferable to wind a fluororesin film in order to prevent the film from being taken off.

<Circuit board manufacturing method>
A method of manufacturing a circuit board using such a release film will be described in detail based on a preferred embodiment with reference to FIG.
As shown in FIG. 2, the circuit board 4 forms a circuit (circuit portion 41) having a predetermined pattern on the surface of the resin film 40. For example, after forming a copper layer on the resin film 40, patterning or the like is performed.
Then, the cover lay film 5 and the release film 10 are laminated on the circuit board 4, and they are sandwiched between the upper and lower sides by the contact plate 6. At this time, the adhesive layer 52 of the coverlay film 5 is disposed on the circuit portion 41 side of the circuit board 4. The release layer 1 of the release film 10 is disposed on the base layer 51 side of the coverlay film 5.
And in the state which pinched the circuit board 4, the coverlay film 5, the release film 10, etc. with the contact plate 6, it heats and pressurizes and a circuit board is obtained by press molding.

<Storage modulus>
The storage elastic modulus of the release layer resin at the press temperature is 7.0 × 10 ⁶ Pa or more and 2.0 × 10 ⁸ Pa or less. 1.0 × 10 ⁷ Pa or more and 4.0 × 10 ⁷ Pa or less is more preferable. If the storage elastic modulus is less than the lower limit value, the surface roughness after the pressing step is less than 2.0 μm, the releasability from the backing plate is deteriorated, and if it exceeds the upper limit value, the embedding property may be lowered.

<Method for producing release film>
Although the manufacturing method of the release film used for this invention is not limited, It can manufacture by any manufacturing methods, such as a co-extrusion method, an extrusion lamination method, and a dry lamination method.
There is no problem even if an adhesive resin layer is interposed between the release layer and the intermediate layer sandwiching the opposite layer to the release layer, but it is preferable not to use an adhesive resin because there is less film end surface bleeding.

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 raw materials used in the following Examples and Comparative Examples, and the crystallization temperatures and melting points thereof are as follows.
Copolymer of 4-methyl 1-pentene polymethylpentene and α-olefin (TPX): product number MX004 (crystallization temperature 210 ° C.) (manufactured by Mitsui Chemicals, Inc.)
Ethylene-methyl acrylate copolymer (EMMA): product number ACLIFT WD203-1 [melt flow rate (MFR) = 2.0 g / 10 min, melting point 90 ° C.] (manufactured by Sumitomo Chemical Co., Ltd.)

<Creation and evaluation of release film>
Although the release film of this invention is not necessarily limited to three layers, the example implemented by three layers below is shown. The release films used in Examples 1 to 18 and Comparative Examples 1 to 11 supply TPX resin as a release layer, EMMA resin as an intermediate layer, and TPX resin to an opposite release layer to three extruders, respectively. Thus, it was co-extruded from a three-layer die and laminated and integrated. Examples 1 to 9 and Comparative Examples 1 to 6 were embossed offline, and other examples and comparative examples were embossed inline.
For Examples 1 to 8 and 10 to 18 and Comparative Examples 2, 3 and 5 to 11, the layers on the side in contact with the circuit board and the layers in contact with the backing plate side as shown in Tables 1 and 2 In Example 9, embossing is performed only on the layer in contact with the contact plate side, Comparative Example 4 is performed only on the layer in contact with the circuit board, and Comparative Example 1 is double-sided. In both cases, the releasability was evaluated.

The surface roughness (Rz: 10-point average roughness) of the release film was measured using a surface roughness shape measuring machine (manufactured by Tokyo Seimitsu Co., Ltd., HANDYSURF E-35A). Measurement conditions were based on JIS B0601, and the measurement was performed with a measurement width of 4000 μm and a speed of 0.6 mm / S.
The storage elastic modulus was evaluated by measuring from normal temperature to 250 ° C. in a tensile mode, a frequency of 1 Hz, and a heating rate of 5 ° C./min with a dynamic viscoelasticity measuring device (Seiko Instruments, DMS6100).

<Evaluation as a release film during the production of circuit boards>
As a circuit board pressing process, a one-stage press was used. For Examples 1 to 12 and Comparative Examples 1 to 4 and 6 to 10, a release film and an FPC for evaluation (both cut to 15 cm × 15 cm) were used. The press temperature (the temperature of the upper and lower heating platen 7) is 185 ° C., the press pressure is 15 MPa, heated at normal pressure for 10 seconds, and then pressed for 160 seconds (see FIG. 2 for the configuration). The evaluation items were implemented. In addition, about the comparative example 5, it implemented at the press temperature of 220 degreeC. The evaluation results are shown in Tables 1 to 4.
-Contents of FPC for evaluation Size: 15cm x 15cm
Base sheet (material: copper, total thickness: 110 μm): The pattern shape described below is created on the base sheet using copper, and a polyimide resin is embedded between the circuits to adjust to a predetermined line height.
Circuit (Material: Copper)
Pattern shape: 15 parallel patterns with line / line width / line height of 80/70/30 μm created (as shown in FIG. 5) are arranged Coverlay film Size: 15cm × 15cm
Base material layer (component: polyimide, thickness: 15 μm)
Adhesive layer (component: epoxy resin, thickness: 25 μm)
Catch plate (cover plate covered with fluororesin film)
Size: 25cm x 25cm, thickness: 2mm
Batter plate material: Stainless steel Fluororesin film (Nitto Denko, Nitoflon 900UL, thickness: 180μm)

<Releasability (I) (Releasability from the backing plate)>
In the evaluation of releasability with the backing plate, the release state between the film and the backing plate was determined on the hot platen immediately after the press release. Judgment was performed in the mold release state.
○: After release of the press, the release film peels off naturally from the backing plate. ×: After release of the press, the release film adheres to the backing plate <Release (II) (Release of release layer resin)> (circuit board side) And releasability)
After pressing at 185 ° C., 15 MPa for 160 seconds, the release property (II) between the circuit board surface and the release film was evaluated. The evaluation was performed when the surface temperature of the test sample reached 150 ° C.
The releasability is in accordance with “JPCA standard (design guide manual, single-sided and double-sided flexible printed wiring board / JPCA-DG02, hereinafter abbreviated as JPCA standard), 7.5.7.1 surface deposit”. The peeled state of the circuit board and the release film was visually evaluated.
Releasing of release layer resin ◎: Breaking rate less than 1.0% ○: Breaking rate 1.0% to less than 2.0% ×: Breaking rate 2.0% or more

<Moldability>
The moldability was evaluated in accordance with “the air bubbles in 7.5.3.3 of the JPCA standard”. Each code is as follows.
○: Void generation rate less than 2.0% ×: Void generation rate 2.0% or more

<Dyeing amount of CL adhesive layer>
Evaluate whether or not the adhesive layer of the coverlay film oozes out on the circuit board in accordance with “JPCA Standard Section 7.5.3.6 Coverlay Adhesive Flow and Covercoat Smudge” did. Each code is as follows.
CL adhesive flow (adhesive bleeding length from CL end face)
A: Flow amount less than 80 μm ○: Flow amount 80 μm or more and less than 100 μm X: Flow amount 100 μm or more

<Length of film end face stain>
Release film end face bleeding length (measured length of resin bleeding from film 4 direction end face)
Exudation length of film end face ○: Exudation length of less than 5 mm ×: Exudation length of 5 mm or more

As for the appearance, the respective symbols evaluated in accordance with “JPCA standard 7.5.7.2 wrinkle” are as follows.
Finished appearance wrinkle ○: Wrinkle occurrence rate less than 2.0% ×: Wrinkle occurrence rate 2.0% or more

The plating property was evaluated according to the “Appearance of JPCA standard 7.5.4 plating (a non-defective product having 90% or more of the required plating area)”.
Plating property ○: non-defective product is 98% or more ×: non-defective product is less than 98%

  The crystallization temperature was raised from room temperature to 250 ° C. at a temperature rising rate of 10 ° C./min with a differential scanning calorimeter (DSC-50, manufactured by Shimadzu Corporation), and then from 250 ° C. to room temperature at a temperature falling rate of 10 ° C./min. The temperature was evaluated until the temperature was lowered and measured. From the chart obtained after the measurement, the peak top observed in the temperature lowering process was defined as the crystallization temperature.

<Crystallinity>
The degree of crystallinity was measured on the release layer resin surface of the release film using an X-ray diffractometer (Rigaku, AFC-5R) at a measurement angle of 2θ = 5-30 ° and an output of 12 kW (= 40 kV × 300 mA). From the obtained data, the peak appearing at 2θ = 9.6 ° was calculated by the following formula: Crystallinity = Crystal region area / (Crystal region area + Amorphous region area) × 100.

<Softening point of surface>
The softening point Ts of the surface is measured by using a heat distortion tester tester (Toyo Seiki, SHI-172) and a 1 mm diameter needle with a flat finished tip at the center of the release layer resin surface of the release film. The temperature was raised from 25 ° C. at a rate of 120 ± 5 ° C./hr with a 1 kg load applied to the top of the needle, and the temperature was defined as the temperature at which the needle entered the surface layer of 10 μm.

  The release film of the present invention is useful when producing a circuit board (particularly a flexible circuit board). In other words, with the reduced release from the circuit board and the appearance of the appearance of the circuit board, the amount of oozing out of the adhesive was suppressed, and the plating property was improved. Providing a release film that improves mold release from the backing plate, is expected to reduce man-hours even in actual work, and is superior in tear strength, elongation, and tensile strength compared to conventional release films. Can do.

It is sectional drawing which shows an example of the release film of this invention. It is a state figure which shows an example of the state which manufactures a circuit board using the release film of this invention. It is a figure which shows the state embossed in-line on the surface of the release film of this invention. It is a figure which shows the state embossed on the surface of the release film of this invention offline. It is an enlarged view of a circuit board for evaluating releasability of the present invention and its circuit pattern.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Release layer 2 Intermediate | middle layer 3 Release opposite layer 4 Circuit board 40 Resin film 41 Circuit part 5 Coverlay film 51 Base material layer 52 Adhesive layer 6 Cover plate 7 Hot plate 8 Fluororesin layer 9 Rough surface of release film 10 Release film 11 Die 12 First roll 13 Touch roll 14 Second roll 15 Film 16 Emboss roll 17 Rubber roll 18 Free roll

Claims (9)

A release film having an emboss used in a pressing process of a circuit board, wherein a resin constituting a release surface of the release film is 4-methyl 1-pentene polymethylpentene resin, The embossed surface roughness (Rz: 10-point average roughness) of the mold film is 5 μm or more and 20 μm or less before the pressing step, and after the pressing step under the conditions of a pressing temperature of 185 ° C., a pressing pressure of 15 MPa, and a pressing pressure of 160 seconds. A release film characterized by being 2 μm or more and 8 μm or less. 2. The release film according to claim 1, wherein a crystallization temperature of a resin constituting a release surface of the release film is higher than a press temperature in a circuit board pressing step. The release film according to claim 1 or 2, wherein a crystallization temperature of a resin constituting a release surface of the release film is 170 ° C or higher. 4. The release film according to claim 1, wherein the softening point TS (° C.) of the surface of the resin constituting the release surface of the release film is 48 or more and 56 or less. The said release film is a multilayer film of 3 or more layers, and at least 1 layer of an intermediate | middle layer is a layer comprised by ethylene-type resin or an acrylic resin, Either in Claim 1, 2, 3, or 4 The release film as described. The first roll and / or the touch roll is a roll surface in a process in which a molten resin extruded into a film by extrusion molding is sandwiched between a first roll and a touch roll that make a pair, and then a release film is manufactured through a cooling roll. The surface temperature T1 (° C.) of the film immediately before being sandwiched between the first roll and the touch roll is Tc-60 <T1 <Tc-20 (where T _C is the separation of the release film). a crystallization temperature of the resin constituting the molding surface (° C.)), claim a surface temperature T2 (° C.) is Tc-150 <T2 <170 immediately before the film drawn off to the cooling roll 1, 2, 3 4. A release film according to 4, or 5 . The release film according to claim 6 , wherein the surface of the touch roll is a rubber roll. In the step of embossing a film manufactured by extrusion using a roll having an emboss shape, the surface temperature T0 (° C.) of the roll having the emboss shape is T _C −40 <T0 <T _C +10 (however, The release film according to claim 1, 2, 3, 4, or 5 , wherein _TC is within a range of a crystallization temperature (° C) of a resin constituting a release surface of the release film. Method of manufacturing a circuit board, characterized by being manufactured using the release film according to any of claims 1 to 8.

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