KR101125423B1 - Coverlay film and the preparing process thereof - Google Patents

Abstract

The present invention relates to a coverlay film and a method of manufacturing the coverlay film of the present invention is a coverlay film composed of an insulating film, an adhesive layer and a peelable protective film sequentially laminated, the protective film is a plastic substrate It is characterized by being a release film in which a mold release material is apply | coated to the plastic film whose ten point average roughness Rz of a base material by a two-dimensional roughness analysis method is 0.5 micrometer or more and 5 micrometers or less by containing an inorganic particle in it.

The coverlay film of the present invention configured as described above is a release film that protects the adhesive layer of the coverlay that protects the circuit of the flexible circuit board, and a plastic base material of which the ten point average roughness (Rz) of the substrate is controlled to be in a predetermined range is used. Since the matting layer is formed on the surface by the irregularities of the particles contained in the plastic substrate and the release layer is formed thereon, the price can be lowered compared to the conventionally used release paper of the three-layer structure, At the same time to solve the curling effect, it is possible to solve the problem of tackiness floating on the punching surface and the problem of burrs generated during punching, which has been a problem in the conventional transparent release film without irregularities.

Coverlay, Flexible Circuit Board, Protection, Release Film, Release Paper, Adhesive.

Description

Coverlay film and its manufacturing method

The present invention relates to a coverlay film and a method for manufacturing the same. More specifically, the coverlay film for circuit protection of a flexible circuit board is less affected by moisture, so that curling is good and blocking in the coverlay application process is good. The present invention also relates to a coverlay film excellent in visibility of the punchable property and the release layer surface, and a method of manufacturing the same.

In general, a coverlay used for circuit protection in a conventional flexible circuit board is formed with an adhesive layer to adhere to the circuit surface of the substrate, and thus is applied to a release paper or a transparent substrate to protect the adhesive of the adhesive layer during manufacture of the coverlay. Release films subjected to release treatment have been used.

In the case of the release paper described above, a polyolefin resin such as polyethylene or polypropylene resin is laminated on the surface of the base sheet, a release layer is formed, or an alkyd resin is coated to form a release layer, and fine irregularities are formed on the surface. It is known to emboss the release layer by means of one emboss roll. Moreover, in the case of the said release film, in order to prevent adhesion | attachment or sticking between a base material, such as a paper or a plastic film, and an adhesive substance, a cured film of a silicone composition is formed in a surface of a base material, and exfoliation property is provided. When the substrate surface is a plastic film, it is commonly referred to as a release film, which releases the adhesive adhesive surface of the adhesive layer temporarily from contamination by dust, debris, moisture and other contaminants until the product is ready for use, for example. It protects you. Therefore, in general, the release paper or the release film is separated from the adhesive surface immediately before use of the adhesive article.

Particularly, in the release film, a polyester film is generally used as the base film, and the polyester film has a stable chemical structure, high mechanical strength, and excellent properties in terms of physical properties such as heat resistance, durability, and chemical resistance. Because it represents. Among these polyesters, in particular, polyethylene terephthalate has excellent stability of physical properties over a wide temperature range from low temperature to high temperature, excellent chemical resistance, good mechanical strength, surface properties, and uniformity of thickness. As it has excellent adaptability to process conditions of various uses, it is widely used for industrial, medical, and packaging. In addition, in the recent environmental pollution problem, the recycling rate is high, so the importance of the industrial sector is increasing.

Moreover, the release paper used at the time of manufacture of the cover protection film for circuit protection of the conventional flexible circuit board generally uses the thing which formed the release layer in the one surface of the thing which laminated polyolefin film, paper, and polyolefin film sequentially. Such three layers of release paper has the advantage of good handleability, but the middle paper layer is easy to absorb moisture, there is a problem of dropping workability (cutting) in the process due to curling (curling) problem due to the dimensional change by moisture absorption, There is a disadvantage in that the cost is increased by manufacturing in a three-layer structure.

Therefore, in order to solve the above problem, it has been attempted to use a release layer formed on one surface of a single-layer plastic substrate as a protective film for the coverlay adhesive layer, but due to the smooth surface shape of the plastic surface of the laminated adhesive It is smoothed and it causes blocking when joining on the copper clad laminate where the pattern is formed after removing the release layer when using the coverlay, and causes poor workability. There is a problem in that (Burr) is generated to act as a foreign material on the circuit, and due to transparency, there is a problem that the release layer surface is difficult to see.

As for the release paper or the release film, for example, Korean Patent Publication No. 2004-0086279 is to provide a release film capable of hard peeling without substantially containing silicon and halogen elements, at least one surface of the base film Is a film having a release layer, the abundance ratio (Si / C) of silicon atoms to carbon atoms on the surface of the release layer is 0.01 or less, the abundance ratio (X / C) of halogen atoms to carbon atoms is 0.1 or less. It discloses a release film characterized in that the peel force is 75 mN / cm or less, the residual adhesion rate is 80% or more, Korean Patent Publication No. 2007-0033420 has excellent heat resistance and mechanical strength, even if repeated use, the surface gloss For the purpose of providing a release sheet capable of suppressing the formation of the sheet, fine roughness of mat-like is formed on the surface of at least one surface of the base sheet. That a matting layer is formed, and a release layer formed of a coating film layer of a release resin containing an ultrafine particle having an average particle diameter of 0.01 to 0.3 µm is formed on the surface of the matified layer. Disclosed are a release sheet characterized by.

In addition, the Republic of Korea Patent Publication No. 2006-0003355 has excellent release properties, less heat shrinkage, less likely to wrinkle wrinkles on printed circuit board products, to provide a release film suitable for the manufacture of flexible printed substrates difficult to wrinkle on the release film itself. The release film for printed circuit board manufacture containing the resin layer containing 50 weight% or more of polyphenylene ether resin is disclosed. However, the release film of the present invention discloses that it is used to facilitate the peeling of the pressurized hot plate and the coverlay film when the coverlay film is welded to the circuit board.

As described above, in the prior art, it is conventionally proposed to improve the peelability of a release film which is temporarily attached to the surface of the adhesive layer of the coverlay film for manufacturing a flexible printed circuit board and is easily peeled off during use while protecting the adhesive layer. There is no release film.

Accordingly, an object of the present invention is to solve the above-mentioned conventional problems, and the curling is good under the influence of moisture, and the blocking in the coverlay application process is not only good, but also the punchability and visibility of the release layer surface. It is for providing this excellent coverlay film.

Another object of the present invention is to provide a method for producing a coverlay film having the above characteristics more easily.

The present invention may also be directed to achieving other objects in addition to the above-described specific objects that may be readily derived by one of ordinary skill in the art from the general description of this specification.

Coverlay film of the present invention for achieving the above object;

In the coverlay film composed of an insulating film, an adhesive layer and a peelable protective film sequentially laminated,

The protective film is a release film coated with a release material on a plastic film having a ten-point average roughness (Rz) of the substrate by a two-dimensional roughness analysis method of 0.5 μm or more and 5 μm or less by containing inorganic particles in the plastic substrate. .

According to another configuration of the present invention, the plastic substrate of the protective film is characterized in that the one selected from polyester-based, polypropylene-based, polyethylene-based resin.

According to another configuration of the present invention, the visible light transmittance of the protective film is characterized in that less than 80%.

According to another configuration of the present invention, the inorganic particles contained in the plastic substrate are characterized in that the inorganic particles such as silicon dioxide, aluminum hydroxide, alumina, titanium oxide are used alone or in combination.

According to another configuration of the present invention, the particle diameter of the inorganic particles is characterized in that the 0.001 to 5㎛.

According to another configuration of the present invention, the amount of the inorganic particles to the plastic substrate is characterized in that 0.5% by weight or more and 5% by weight or less.

Method for producing a coverlay film of the present invention for achieving the above another object;

A coverlay film was prepared by coating 15-50 μm of 20 to 40 wt% epoxy resin epoxy resin for coverlay on the insulating film, volatilizing an organic solvent contained in the adhesive, and laminating it using a protective film. Here, the protective film is a release film coated with a release material on a plastic film having a ten-point average roughness (Rz) of the substrate by a two-dimensional roughness analysis (Rz) of 0.5㎛ or more and 5㎛ or less by containing inorganic particles in the plastic substrate. Characterized in that.

The coverlay film of the present invention configured as described above is a release film that protects the adhesive layer of the coverlay that protects the circuit of the flexible circuit board, and a plastic base material of which the ten point average roughness (Rz) of the substrate is controlled to be in a predetermined range is used. Since the matting layer is formed on the surface by the irregularities of the particles contained in the plastic substrate and the release layer is formed thereon, the price can be lowered compared to the conventionally used release paper of the three-layer structure, At the same time to solve the curling effect, it is possible to solve the problem of tackiness floating on the punching surface and the problem of burrs generated during punching, which has been a problem in the conventional transparent release film without irregularities.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail by preferable embodiment.

In the coverlay film according to the present invention, an insulating film, an adhesive layer, and a peelable protective film (release film) are sequentially stacked.

As an insulating film which comprises one layer of the said coverlay film, the film which consists of plastics, such as a polyimide, polyester, polyphenylene sulfate, polyester sulfone, polyethyl ketone, aramid, polycarbonate, polyarylate, is mentioned. You may laminate | stack a some film. As for the thickness of the said insulating film, 5-200 micrometers is preferable. In addition, the insulating film may be subjected to surface treatment such as hydrolysis, corona discharge, low temperature plasma, physical surface irregularities treatment, and easy-adhesive coating treatment, if necessary. As a main structure of a coverlay film, it becomes an insulating film (10-125 micrometers) / adhesive layer (5-50 micrometers) / peelable protective film (12.5-125 micrometers), such as a polyimide film or an aramid film, for example. These are sequentially stacked.

The adhesive layer is a portion which is directly bonded to the circuit surface of the flexible circuit board through a press and serves to surround the circuit through a suitable flow of adhesive in the pressing process. Such an adhesive includes a thermosetting resin (epoxy or acrylic) having a crosslinkable functional group to function to be cured through crosslinking between molecules after pressing, and also a thermoplastic resin such as acryl, which can control flowability. Ronitrile-butadiene copolymer and the like. In addition, bromine-based flame retardants or phosphorus-based flame retardants may be added in order to have a level of flame retardancy that must be satisfied as an electronic component.

The release film of the protective film constituting the coverlay film of the present invention is formed of one plastic substrate selected from polyester-based, polypropylene-based, and polyethylene-based resins, wherein the surface roughness of the plastic substrate is determined by two-dimensional roughness analysis. Ten point average roughness (Rz) It is obtained by apply | coating a mold release material to the surface using the single-layered plastic base material 0.5 micrometer or more.

Examples of the release film according to the present invention include polyolefin resins such as polyethylene resins and polypropylene resins, polybutylene terephthalate resins, polyethylene terephthalate resins, polyester resins such as polyethylene naphthalate resins, polyetherimide resins, and acetates. The sheet | seat of synthetic resin, such as resin, a polystyrene resin, and a vinyl chloride resin, etc. are mentioned. Although the thickness of a base material sheet does not have a restriction | limiting in particular, Usually, 10-300 micrometers may be sufficient, Preferably it is 20-200 micrometers. If the substrate is too thin or too thick, the handleability is poor, and the cost is too high at 200 µm or more, which is not preferable.

According to a preferred embodiment of the present invention, it is preferable to mix and use inorganic particles such as silicon dioxide, aluminum hydroxide, alumina, titanium oxide and the like to the plastic substrate which is the substrate of the release film. What is necessary is just to select the particle size of the said inorganic particle normally 0.001-5 micrometers, and to mix | blend with respect to a plastic base material at 0.5 weight% or more and 5 weight% or less. The surface of the film thus formed may have a ten-point average roughness Rz of 0.5 µm or more and 5 µm or less by a two-dimensional roughness analysis method. If the amount of the inorganic particles to the plastic substrate is less than 0.5% by weight, the average ten point average roughness is less than 0.5 µm, so that appropriate surface roughness cannot be formed. After removing the film, the surface irregularities of the adhesive are inadequately formed, causing blocking in the welding process and worsening of cutability, which causes burrs in the cutting process, which acts as a foreign material in the product or decreases the yield. It is not preferable because proper opacity cannot be secured and it becomes difficult to visually recognize. On the contrary, when the blending amount is more than 5% by weight, the average ten point average roughness is more than 5 µm, so that a suitable surface roughness cannot be formed and peelability is lowered, which is not preferable.

In addition, since the particle size of the inorganic particles used in the present invention acts as a factor influencing the ten-point average roughness, for the same reason as above, it is preferable to limit to the range according to the present invention.

According to a preferred embodiment of the present invention, the release layer of the protective film is formed by applying a release agent solution to a base film, followed by heat treatment, drying and thermosetting. The release agent may be used by mixing a silicone release agent or various polymeric materials with a silicone additive, a fluorine additive, and the like. The thickness of the release layer is not particularly limited, but is usually 10 nm or more, preferably 50 nm or more, and usually 0.1 to 15 g / m 2 is preferable as the coating amount after drying.

When the application amount of the release layer is less than 0.1 g / m 2, the peeling performance may become unstable, which is not preferable. On the other hand, when the application amount of the release layer exceeds 15 g / m 2, the surface of the release layer when the release sheet is wound in a roll shape is easily blocked with the release sheet back surface, and the peeling performance of the release layer surface is lowered by blocking. There is, it is not preferable that the adhesive roughening by the release film surface roughness to be obtained in the present invention is not easy.

Examples of the method for applying the release agent include gravure coating, bar coating, spray coating, spin coating, air knife coating, roll coating, blade coating, gate roll coating, die coating, and the like. Can be used.

In addition, as a drying method, the method of heat-drying with a hot air drying furnace etc., etc. can be used, for example. Although drying temperature does not have a restriction | limiting in particular, 100-200 degreeC is preferable, and drying time is preferable to set it as 10 to 5 minutes.

Peeling force of the release layer of the release substrate of the present invention is a sticking tape "No.502" (manufactured by Nitto Denko Kobushiki Kaisha) on the surface of the release layer and allowed to stand at room temperature for 1 hour, followed by a tensile speed of 300 mm in a tensile tester. 90 degree peeling is performed by / min, and it is preferable that a measured value is 500-1200mN / 3cm.

According to another preferred embodiment of the present invention, the method for producing a coverlay film according to the present invention, specifically, coated on the polyimide film 15 to 50㎛ coating 20 to 40% by weight epoxy resin adhesive solids After volatilizing the organic solvent contained in the adhesive, it can be laminated using a protective substrate (release film, release paper, etc.) to produce a coverlay film. The coverlay film thus prepared may be subjected to a heat treatment process at a temperature of 60 ° C. or lower to lower the resin flow of the adhesive.

Hereinafter, although an Example demonstrates this invention in detail, these Examples are for demonstrating this invention in detail, Of course, the scope of the present invention is not limited by these Examples.

The performance evaluation of the release sheet obtained by the Example or comparative example of this invention was performed by the following method.

(1) curling properties;

The release sheets obtained in the Examples and Comparative Examples were cut into 150 mm in length and 150 mm in width in the width direction after preparation of the coverlay, and the specimens were cut to form a sample piece. After installing on a horizontal stand so as to face, it was left to stand at room temperature for 24 hours, and the average value of the heights of four corners of the sample piece lifted from the horizontal stand was measured. In addition, the curling height was measured by the same method after 3 days to confirm the curling properties after moisture absorption.

(2) punchability;

The coverlay product was put into a punching machine used for the coverlay punching process of the flexible circuit board and processed. Observe the punching surface of the processed product under a microscope, ○ if there is no lifting around the punching surface, mark with X if lifting, and a good level without burr generation on the punching surface ○, part of the burr △, which does not cause a problem in use, and burr occurrence is severe and are marked as unusable level X.

(3) accessibility;

When the coverlay product goes through the punching process, the release substrate is peeled off and the degree of blocking between the adhesive coated on the polyimide film and the circuit board is evaluated.When freely moving, the initial movement is less, but after time passes. △ If there is no movement, it is marked with X.

(4) visibility;

It indicates whether the coverlay film is visually distinguished during the punching process, and when the release substrate has a color and the punching surface can be distinguished, ○ is indicated by X when not easily distinguished.

Example 1

Ten point average roughness (Rz) was 2.17 micrometers, and 0.3 g / m <2> release coating was performed on the polyethylene terephthalate film which is 36 micrometers in thickness, and it dried and produced the release base material.

After coating the epoxy resin for the coverlay on the insulating film, the release substrate was laminated through a lamination process to prepare a coverlay film. The obtained coverlay film was evaluated by the said test method. The results are shown in Table 1.

Comparative Example 1

Ten point average roughness (Rz) was 0.25 micrometer, and 0.3 g / m <2> release coating was performed on the transparent polyethylene terephthalate film which is 36 micrometers in thickness, and it dried and produced the release base material.

After coating the epoxy resin for the coverlay on the insulating film, the release substrate was laminated through a lamination process to prepare a coverlay film. The obtained coverlay film was evaluated by the said test method. The results are shown in Table 1.

Comparative Example 2

In general, a release paper, which is widely used for adhesive protection of a coverlay, was used. In the case of the release paper, polyethylene was laminated on both sides of the paper, and a release layer was formed only in a single layer.

After coating the epoxy resin for the coverlay on the insulating film, the above release paper was laminated through a lamination process to prepare a coverlay film. The obtained coverlay film was evaluated by the said test method. The results are shown in Table 1.

unit Example 1 Comparative Example 1 Comparative Example 2 Total thickness Μm 36 36 130 Curling property Early mm 3 3 3 3day room temperature storage mm 3 3 20 Visibility ○ X ○ Punchability Lifting degree of punching surface ○ X ○ Burr occurrence degree ○ △ △ Accessibility (Blocking) ○ X ○

As can be seen from Table 1, in the case of using Comparative Example 2 which is a conventional release paper generally used a lot, the curling change is severe after 3 days, but the cutability is reduced, when applying Example 1 according to the present invention It can be seen that the punching ability, curling after 3 days, and the splintering, punching, etc. are all good and passed.

Claims (3)

In the coverlay film composed of an insulating film, an adhesive layer and a peelable protective film sequentially laminated, The protective film is a release film coated with a release material on a plastic film having a ten-point average roughness (Rz) of the substrate by a two-dimensional roughness analysis method of 0.5 µm or more and 5 µm or less by containing inorganic particles in the plastic substrate. Coverlay film. The coverlay film of claim 1, wherein the plastic substrate of the protective film is one selected from a polyester-based, polypropylene-based, and polyethylene-based resin. The coverlay film according to claim 1, wherein the visible light transmittance of the protective film is 80% or less.