TWM481570U - Covering film and flexible printed circuit board having the same - Google Patents

Description

Cover film and flexible printed circuit board having the same

This creation relates to cover films, and more particularly to a cover film for protecting flexible printed circuit boards.

Printed circuit board is an indispensable material in this product, and as the demand for consumer electronics increases, so does the demand for printed circuit boards. At present, commercial small-sized electronic products not only have to be smaller and lighter, but also have a degree of freedom in design. Therefore, most of the wiring materials are flexible printed circuit (FPC) with high design freedom and good flexibility. In the FPC field, not only the mainstream smart phones, but also new demands for touch panel design. In the FPC, it is expected to be able to achieve breakthroughs in various thicknesses and workability as the FPC continues to develop at a high speed and high flexibility.

In general, flexible printed circuit boards are mainly composed of a copper foil substrate (FCCL, Flexible Copper Clad Laminate) and a cover film (CL, Coverlay). Generally, a plastic film is used as a cover film, or a layer is formed by screen printing technology. A thin insulating ink is used as the cover film. These conventional cover films have the consideration of thickness thickness, uneven filling property, and the life of the cover film itself.

Polyimide (PI) has been widely used in electronic materials. In addition to being used as a substrate for FPC, traditional PI composites have been introduced on the market. Membrane, photosensitive PI (or acrylic) composite film, non-photosensitive PI composite film or photosensitive acrylic composite film.

However, the polyimine resin is mostly highly translucent, which results in the use of the FPC cover film, which makes the circuit design of the FPC circuit layer easy to interpret and is plagiarized by the same industry, thereby affecting the sales of the product market. Therefore, most of the cover films on the market are bright-light polyimide films, and in order to make the polyimide film have the function of shielding the circuit layout, the conventional cover film uses two protective layers to achieve the effect of shielding the circuit. As shown in Figure 1.

Please refer to Fig. 1, which is a schematic cross-sectional view of a conventional cover film. The cover film 11 as shown in FIG. 1 includes: an adhesive layer 114; a second protective layer 113 is formed on the adhesive layer 114; a first protective layer 112 is formed on the second protective layer 113; The release layer 111 is formed on the first protective layer 112. In addition, the release paper 12 is overlaid on the adhesive layer 114, and the release layer 111 and the release paper 12 are removed when the cover film 11 is used. However, the second coating to form the first protective layer 112 and the second protective layer 113 can satisfy the requirements of the shielding line and the matte matte surface, but at the same time, the thickness of the covering film is increased, and then used for FPC reduces the flexibility of FPC.

In view of this, it is not necessary for the industry to develop a cover film having high shielding properties, light weight, and high flexibility, so that the flexible printed circuit board not only has the characteristics of light weight and high flexibility, but also protects the circuit design. Peeking in the industry.

Accordingly, the present invention provides a cover film comprising: an adhesive layer; a protective layer formed on the adhesive layer; and a release layer formed on the protective layer, the protective layer being sandwiched between the release layer and the adhesive layer Between layers.

In another embodiment of the inventive cover film, a release paper is formed which is formed on the adhesive layer such that the adhesive layer is sandwiched between the protective layer and the release paper.

The present invention provides a flexible printed circuit board comprising: a substrate; a circuit layer formed on the substrate; and an adhesive layer and a protective layer laminated to each other by the adhesive layer contacting the substrate and the circuit layer The circuit layer is shielded, wherein the thickness of the protective layer of the cover film is between 1 and 15 microns.

In an embodiment of the flexible printed circuit board of the present invention, the substrate further includes an adhesive layer for adhering the wiring layer to the substrate.

In the foregoing flexible printed circuit board, part of the substrate exposes the adhesive layer and the protective layer which are overlapped with each other. In addition, in the above flexible printed circuit board, the material of the substrate is an insulating material such as polyimide, and the material of the circuit layer is copper foil.

In the foregoing cover film, the cover film has a thickness of from 13 to 68 μm, and in a preferred embodiment, the cover film has a thickness of from 14 to 66 μm, more preferably from 15 to 65 μm.

In the aforementioned cover film, the protective layer has a thickness of from 1 to 15 μm.

In the aforementioned cover film, the protective layer comprises a polymer and an additive. In the above coating film, the polymer is selected from the group consisting of an epoxy resin, an acrylic resin, a urethane resin, a ruthenium rubber resin, a polyparaphenylene resin, and a bismaleimide resin. And at least one of the group consisting of polyimine resins.

In a preferred embodiment, the polymer is selected from the group consisting of polyamidiamine resins having a guanamine functional group in the backbone, such as polyamidoximine. In addition to improving the water absorption and hygroscopicity of polyimine, polyamidoximine has better properties in terms of color masking, softness, thickness, chemical resistance and flexibility than general polyimide. Also has good Electrical characteristics.

In addition, its low-temperature curing properties are particularly suitable for the protective layer of the creation by spraying or printing. The protective layer of the present invention is formed by inkjet or printing, so that the protective layer can have a thickness of 8 micrometers and further less than 8 micrometers, which is a thickness which is difficult to achieve by conventional coating films.

In the aforementioned cover film, the additive is selected from the group consisting of carbon powder, titanium white powder, pigment or dye.

In the above cover film, the material of the adhesive layer is selected from the group consisting of epoxy resin, acrylic resin, urethane resin, silicone rubber, polyparaphenylene resin, and bismaleimide. At least one of a group consisting of a resin and a polyimide resin.

In the foregoing cover film, the material of the release layer is not particularly limited. Preferably, the release layer material comprises polyethylene terephthalate or polyethylene.

In summary, the protective layer in the cover film of the present invention has good electrical properties in addition to thin thickness, better flexibility, chemical resistance and flexibility, and also has color shielding shielding lines. pattern. It is suitable for product applications such as flip-tops, slider phones, digital cameras, digital cameras, lithography computers, smart phones, etc., which have the requirements of bending or sliding circuit boards, to replace the conventional cover film.

3, 3'‧‧‧Soft printed circuit boards

11, 21‧‧ ‧ cover film

111, 211‧‧‧ release layer

112‧‧‧First protective layer

113‧‧‧Second protective layer

114, 214‧‧‧ adhesive layer

12, 22‧‧‧ release paper

212‧‧‧Protective layer

30‧‧‧Substrate

31‧‧‧Line layer

32‧‧‧Next layer

1 is a schematic cross-sectional view showing a conventional cover film; and FIGS. 2 to 2' are schematic cross-sectional views showing a cover film of the present invention, wherein the 2' view shows a cross section of another embodiment of the cover film of the present invention. Schematic; 3 and 3' are schematic cross-sectional views showing a flexible printed circuit board using the present cover film, wherein the 3' is a schematic cross-sectional view showing another embodiment of a flexible printed circuit board using the present cover film. .

The present invention is fully understood by reference to the following detailed description and exemplary embodiments, which are intended to illustrate non-limiting embodiments of the present invention.

It is to be understood that the structure, the proportions, the size and the like of the drawings are only used in conjunction with the disclosure of the specification for the understanding and reading of those skilled in the art, and are not intended to limit the implementation of the present invention. The qualifications, the modification of any structure, the change of the proportional relationship or the adjustment of the size, should not fall under the purpose of the creation and the purpose of the creation, should still fall within the technical content revealed by this creation. Within the scope of coverage. In the meantime, the terms "upper" and "one" as used in this specification are for convenience of description only, and are not intended to limit the scope of implementation of the creation, and the relative relationship is changed or adjusted. Under the technical content of substantive changes, it is also considered to be the scope of implementation of this creation.

Please refer to Figures 2 to 2' for a cross-sectional view of the cover film of this creation. As shown in FIG. 2, the cover film 21 of the present invention includes an adhesive layer 214, a protective layer 212 formed on the adhesive layer 214, and a release layer 211 formed on the protective layer 212. The protective layer 212 is interposed between the release layer 211 and the adhesive layer 214. When the cover film 21 of the present invention is used to shield the wiring, the auxiliary release layer 211 can be removed.

In this embodiment, the protective layer 212 is formed on the release layer 211 with a mixture of an additive and a polymer, and is baked at a low temperature of 150 ° C to 180 ° C. The mixture is formed to form a protective layer.

In the present embodiment, the method of forming the mixture on the release layer is not particularly limited, and may be formed by coating or ink jetting, and the mixture may be formed on the release layer by screen printing. .

Referring to FIG. 2 ′, in another embodiment, the cover film 21 of the present invention comprises a release paper 22 formed on the adhesive layer 214 , so that the adhesive layer 214 is sandwiched between the protective layer 212 and the release paper. Between 22.

Please refer to Figures 3 and 3' for a cross-sectional view of a flexible printed circuit board using the inventive cover film.

Referring to FIG. 3, the flexible printed circuit board 3 of the present invention comprises a substrate 30; a circuit layer 31 formed on the substrate 30; and a substrate 30 and a circuit layer 31 for shielding the circuit layer 31. The cover film 21 of the present invention, wherein the cover film 21 is covered by the adhesive layer 214 to cover the substrate 30 and the wiring layer 31, and the release layer 211 has been torn off.

Referring to FIG. 3 ′, in another embodiment of the flexible printed circuit board of the present invention, the substrate 30 of the flexible printed circuit board 3 ′ further includes an adhesive layer 32 for bonding the circuit layer 31 to the substrate. 30.

In the embodiment of the two types of flexible printed circuit boards, the substrate is made of polyimide, the circuit layer is made of copper foil, and part of the substrate 30 is exposed to the cover film 21.

Embodiments 1 to 5 of the inventive cover film

According to the description of Table 1, the original cover film as shown in Fig. 2 was formed.

In this embodiment, the cover film comprises: a release layer, a protective layer and an adhesive layer, wherein the thickness of the protective layer and the adhesive layer are as described in Table 1. The protective layer is composed of The additive (carbon powder or titanium dioxide) is mixed with the polymer (epoxy resin) and baked at 180 ° C at a low temperature. The adhesive layer is made of epoxy resin; the release layer is made of PET release film.

Comparative Examples 1 to 2

A black polyimide film (Teijin Advanced Films, trade name: Kapton) having a thickness of 12.5 μm was used as a protective layer, and transferred or coated on the protective layer with an epoxy resin adhesive to obtain a cover film of a comparative example.

Comparative example 2

A yellow polyimide film (Teijin Advanced Films, trade name: Kapton) having a thickness of 12.5 μm was used as a protective layer, and transferred or coated on the protective layer with a black epoxy resin adhesive to obtain a cover film of a comparative example.

Test case

The cover films of Examples 1 to 5 and Comparative Examples 1 and 2 were attached to a flexible printed circuit board of the model R-F775 produced by Matsuda Electric Co., Ltd., and the substrate of the flexible printed circuit board was made of polyimide plate. The circuit layer material is copper. The gloss, brightness, flexibility and flexibility of the test piece were measured by the following test methods, and the test results of the test were recorded in Table 2 below.

The test methods used in the test examples are as follows: Gloss test: using a gloss tester (Omega, Germany; model micro-gloss 60°), according to the ASTM D1003 instrument method, that is, The gloss of the machine direction (MD) was measured under the condition that the light incident angle was 60°.

The term "gloss" as used herein means the degree of reflection of the surface of the sheet to be tested. The gloss does not have a unit, but the larger the value, the stronger the intensity of the reflected light. Conversely, the smaller the value, the reflection. The weaker the intensity of light.

Lightness test: using a brightness tester (KONICA MINOLTA company; model CM2500d, according to ASTM D2244 method, that is, measuring the brightness of the machine direction (MD) with a light incident angle of 45° .

The term "lightness" as used herein is defined by the International Commission on Illumination for the degree of color shading (usually, white has the highest brightness; black has the lowest brightness). Therefore, the lower the brightness, the better the effect of shielding the line.

Softness test: The measurement was performed using a softness tester (Setra, BL-410S) to cut the flexible printed circuit board sheets having the cover films of Examples 1 to 5 and Comparative Examples 1 and 2 into a size of 10 mm × 30 mm, and It was attached to a softness tester and bent into a "U" shape to form an R angle of 2.35 mm to measure the Stiffness data.

Flexibility test: The flexible printed circuit board having the cover films of Examples 1 to 5 and Comparative Examples 1 and 2 was cut into a size of 10 mm × 30 mm using a flexural tester model HT8636 manufactured by Hung Ta Co., Ltd. Size, with a distance of 2.0mm, and form an R angle of 0.8mm, the test stroke of the flexural resistance is 32mm, and the bending or bending action is continuously performed at a speed of 30 times/min until the fracture or cusp is generated, and the measured bending is performed. frequency.

From the results of the above test examples, it is known that the cover film of the present invention has a lower gloss than the comparative examples 1 and 2, in addition to retaining the original good chemical resistance of the polyimide, and making the protective layer thinner. In addition to thickness, better flexibility and flexibility, it also has good electrical properties. In addition, the cover film of the present invention has a very low brightness and a function of shielding the line pattern as compared with the conventional cover film. Therefore, the cover film of the present invention can be used not only as a cover film for FPC but also as an LCM plate, and can be widely applied to products having the demand for bending or sliding circuit boards.

The above embodiments are merely illustrative of the principles of the present invention and their effects, and are not intended to limit the present invention. Any person skilled in the art can modify and change the above embodiments without departing from the spirit and scope of the present invention. Therefore, the scope of protection of this creation should be as listed in the scope of the patent application described later.

21‧‧‧ Cover film

211‧‧‧ release layer

212‧‧‧Protective layer

214‧‧‧Adhesive layer

Claims (13)

A cover film comprising: an adhesive layer; a protective layer formed on the adhesive layer; and a release layer formed on the protective layer such that the protective layer is sandwiched between the release layer and the adhesive layer. The cover film of claim 1, wherein the protective layer has a thickness of from 1 to 15 μm. The cover film of claim 1, wherein the protective layer comprises a polymer and an additive. The cover film according to claim 3, wherein the polymer is selected from the group consisting of an epoxy resin, an acrylic resin, an urethane resin, a ruthenium rubber resin, and a polyparaphenylene resin. At least one of a group consisting of a bismaleimide resin and a polyimine resin. The cover film of claim 4, wherein the polyamidene resin has a guanamine functional group in its main chain. The cover film of claim 3, wherein the additive is selected from the group consisting of carbon powder or titanium dioxide. The cover film of claim 3, wherein the additive is selected from the group consisting of pigments or dyes. The cover film according to claim 1, wherein the adhesive layer is selected from the group consisting of epoxy resin, acrylic resin, urethane resin, ruthenium rubber resin, and polyparaphenylene system. At least one of a group consisting of a resin, a bismaleimide resin, and a polyimide resin. The cover film of claim 1, wherein the material of the release layer comprises polyethylene terephthalate or polyethylene. The cover film according to claim 1, wherein the cover paper is formed on the adhesive layer, and the adhesive layer is sandwiched between the protective layer and the release paper. A flexible printed circuit board comprising: a substrate; a circuit layer formed on the substrate; and an adhesive layer and a protective layer laminated to each other, the adhesive layer contacting the substrate and the circuit layer to shield the circuit a layer, wherein the protective layer has a thickness of between 1 and 15 microns. The flexible printed circuit board of claim 11, wherein a portion of the substrate exposes the mutually adhered adhesive layer and protective layer. The flexible printed circuit board of claim 11, wherein the substrate further comprises an adhesive layer for adhering the circuit layer to the substrate.