TWI754842B - Cover film with emi shielding function and methods for preparing the same - Google Patents

Abstract

The present invention provides a cover film with EMI shielding function comprising a carrier layer having an opposing first surface and a second surface, a first insulation layer formed on the second surface of the carrier layer, a metal layer formed on the first insulation layer, which makes the first insulation layer located between the carrier layer and the metal layer, a second insulation layer formed on the metal layer, which makes the metal layer located between the first and the second insulation layer, and a first adhesive layer formed on the second insulation layer, which makes the second insulation layer located between the metal layer and the first adhesive layer. The cover film with EMI shielding function possesses an insulation effect and an EMI shielding effect, and achieves a thinner thickness than the conventional cover films. The present invention further provides a method for preparing the cover film with EMI shielding function.

Description

Cover film with electromagnetic interference shielding function and preparation method thereof

The present invention relates to a cover film for flexible printed circuit boards, in particular to a cover film with electromagnetic interference shielding function.

Under the market demand that electronic and communication products tend to be multi-functional and complex, the structure of circuit substrates needs to be lighter, thinner and shorter, and in terms of functions, powerful and high-speed signal transmission is required.

As the electronic products in the market are developing towards the trend of thinness and lightness, in order to reduce the overall thickness of the flexible printed circuit (FPC), it is necessary to provide a thinner cover film to cover the FPC. The cover films generally used on FPC are mostly insulating materials, and the most common thicknesses are 37.5 microns and 50 microns. At present, the thinnest thickness of the cover films that can be achieved is about 19 microns, and it is difficult to achieve a thinner thickness.

Among the black polyimide type cover films, due to the special machining properties of polyimide materials, it has become the most widely used type of cover film, but this type of cover film still has its defects. For example, it is difficult to make a black polyimide film with a thickness of less than 5 microns, and its processing operability is not good, and there is a certain bottleneck in thinning. For the needs of aesthetics, visual protection and no circuit exposure, a cover film with a thickness of ≤ 7.5 microns is required. However, the current common black polyimide film is The production method uses the casting method. When the thickness of the black polyimide film is expected to be designed to be 5 to 7.5 microns, the film produced by the existing method cannot meet the requirements of the industry, which makes the selection of process and materials more stringent. . In addition, the black insulating layer of the general cover film cannot achieve a low enough surface gloss (less than or equal to 5GU), although it can be made into a matte surface by adding a matte material such as carbon black or titanium black to the insulating material. However, adding the above-mentioned matting material will affect the mechanical and insulating properties of the insulating material itself. Therefore, while ensuring that the thickness of the cover film is thin enough, it is one of the difficulties in the process to make the surface of the film have a low gloss.

As the transmission of electronic signals is more high-speed and denser, the line density is bound to increase, making the distance between the substrate lines closer, and the application frequency is moving toward a high-bandwidth, making the electromagnetic interference (Electromagnetic Interference, EMI) situation more and more serious, so it must be effectively managed Electromagnetic compatibility (Electromagnetic Compatibility, EMC), so as to maintain the normal signal transmission of electronic products and improve reliability. The characteristics of being light, thin and free to bend make FPC play a pivotal role in the development of the portable information and communication electronics industry. Today's EMI shielding film has more stringent requirements on its thickness and shielding function. The shielding rate of the general cover film is about 55dB, and it is difficult to achieve a shielding effect of 70dB or even higher. Films with higher shielding rates are also one of the difficulties.

It can be seen from the above that the general cover film only has the function of insulating and does not have the effect of EMI shielding. With the increasing demand for these two functions in today's electronic products, how to create a The thin cover film product with EMI shielding function is a problem that needs to be solved at present.

In order to solve the above problems, the present invention provides a cover film with electromagnetic interference shielding function, which comprises: a carrier layer having an opposite first surface and a second surface, and the surface roughness of the second surface is greater than that of the first surface. Surface roughness; a first insulating layer with a thickness of 2 to 10 microns is formed on the second surface of the carrier layer; a metal layer structure with a thickness of 0.01 to 1.0 microns is formed on the first insulating layer, so that The first insulating layer is located between the carrier layer and the metal layer structure; a second insulating layer with a thickness of 3 to 15 microns is formed on the metal layer structure, so that the metal layer structure is located between the first insulating layer and the second insulating layer. Between the two insulating layers, wherein the first insulating layer and the second insulating layer have a glossiness measured at an angle of 60 degrees of 0 to 50GU, and have a surface pencil hardness of 4H or more; and a thickness of 3 to 25 microns The first adhesive layer is formed on the second insulating layer, so that the second insulating layer is located between the metal layer structure and the first adhesive layer.

In an embodiment, the thickness of the carrier layer is 25 to 100 microns.

In another embodiment, a second adhesive layer with a thickness of 3 to 10 microns is formed on the metal layer structure, so that the metal layer structure is located between the first insulating layer and the second adhesive layer , the second insulating layer is located between the second adhesive layer and the first adhesive layer.

In a specific embodiment, the surface roughness Rz value of the second surface of the carrier layer is greater than or equal to 0.8 microns.

In a specific embodiment, the glossiness of the first insulating layer and the second insulating layer measured at an angle of 60 degrees is less than 5GU.

In an embodiment, the thickness of the metal layer structure is 0.2 to 0.6 microns.

In an embodiment, the metal layer structure includes a single metal layer or two metal layers in contact with each other.

In a specific embodiment, the material for forming the single-layer metal layer or the two-layer metal layers in contact with each other is at least one selected from the group consisting of copper, nickel, cobalt, tin, silver, iron and gold.

The present invention further provides a method for preparing a cover film with electromagnetic interference shielding function, which includes: forming a first insulating layer on the carrier layer; forming a metal layer structure on the first insulating layer; forming a second insulating layer on the metal layer structure; and forming a first bonding layer on the second insulating layer.

In an embodiment, before forming the second insulating layer on the metal layer structure, a second adhesive layer is first formed on the metal layer structure. In another embodiment, before forming the second insulating layer on the metal layer structure, a second adhesive layer is first formed on the second insulating layer, and the second adhesive layer is attached to the metal layer structure , so that the second bonding layer is located between the metal layer structure and the second insulating layer.

The cover film with electromagnetic interference shielding function of the present invention uses a surface with high pencil hardness (pencil hardness greater than or equal to 4H) and low gloss (gloss at 60° angle is less than or equal to 50GU), and has good mechanical and electrical properties. The material is used as the first insulating layer to ensure that the insulating layer has both good insulating effect and a very thin thickness (thickness is 2 to 10 microns) during preparation, and the second surface of the carrier layer is designed to have a surface roughness Rz value The rough surface greater than or equal to 0.8 microns makes the second surface contact the first insulating layer, and further makes the surface of the first insulating layer have a certain roughness, so that the finished cover film can optimally reach the gloss of 60° angle measurement Degree is less than or equal to 50GU.

On the other hand, if the thicknesses of the first and second insulating layers are too thick, the metal layer structure disposed between the first and second insulating layers will be unable to conduct during the subsequent application of the cover film. Therefore, In the manufacturing process, the thicknesses of the first and second insulating layers are reduced as much as possible. The first and second insulating layers of the present invention have a minimum thickness of 6 microns or less, and can even reach a thickness of 3 microns, while still having a good insulating effect. The best is about 0.6 microns, so that the cover film product has excellent shielding and conductivity, and has the advantage of thinning.

Furthermore, when the metal layer structure of the present invention is used in conjunction with the first insulating layer, while the first insulating layer exerts an insulating effect, the metal layer structure can achieve a good effect of shielding electromagnetic signal interference. The shielding effect of the general EMI shielding film is usually about 55dB at 1GHz, and it is difficult to reach more than 70dB. In the present invention, the metal layer structure is designed to be 0.6 microns to achieve a shielding effect of 70 dB at 1 GHz.

The cover film of the present invention has the function of insulating the electronic circuit and shielding the transmission signal at the same time. In terms of process technology, the cover film and the shielding film are combined to overcome the difficulties of the two processes to achieve a thinner thickness than the simple cover film, even 9 to 10 microns, and the surface has a higher hardness (above 4H). pencil hardness), extremely low gloss (gloss less than or equal to 5GU) and good mechanical properties, and has excellent shielding effect (greater than or equal to 70dB). In terms of subsequent storage of the product, since the shielding structure of electromagnetic interference is included in the cover film structure in the present invention, the storage method can be stored in the manner of a general cover film.

1‧‧‧Carrier layer

1a‧‧‧First surface

1b‧‧‧Second surface

2‧‧‧First insulating layer

3‧‧‧Metal layer structure

4‧‧‧Second layer

5‧‧‧Second insulating layer

6‧‧‧First Adhering Layer

7‧‧‧Release layer

Embodiments of the invention are described by way of illustrative reference to the accompanying drawings: FIG. 1 is a schematic diagram of the structure of the cover film with electromagnetic interference shielding function of the present invention.

FIG. 2 is another schematic diagram of the structure of the cover film with electromagnetic interference shielding function of the present invention.

The following describes the implementation of the present invention through specific embodiments, and those skilled in the art can easily understand the advantages and effects of the present invention from the contents disclosed in this specification.

It should be noted that the structures, proportions, sizes, etc. shown in the drawings in this specification are only used to cooperate with the contents disclosed in the specification for the understanding and reading of those who are familiar with the art, and are not intended to limit the implementation of the present invention. Therefore, it has no technical significance. Any modification of the structure, change of the proportional relationship or adjustment of the size should still fall within the scope of the present invention without affecting the effect and the purpose that the present invention can achieve. The technical content disclosed by the invention can be covered within the scope. At the same time, references such as "a", "below" and "above" in this specification are only for the convenience of description, and are not intended to limit the scope of the present invention. Substantially changed technical content should also be regarded as the scope of the present invention. Furthermore, all ranges and values herein are inclusive and combinable. Any value or point falling within a range described herein, eg, any integer, can be taken as a minimum or maximum value to derive a lower range, etc.

As shown in FIG. 1, it shows a specific embodiment of the cover film with electromagnetic interference shielding function of the present invention, which includes: a carrier having an opposite first surface 1a and a second surface 1b The body layer 1, and the surface roughness of the second surface 1b is greater than the surface roughness of the first surface 1a; the first insulating layer 2 is formed on the second surface 1b of the carrier layer 1; The metal layer structure 3 is is formed on the first insulating layer 2, so that the first insulating layer 2 is located between the carrier layer 1 and the metal layer structure 3; the second insulating layer 5 is formed on the metal layer structure 3, so that the metal layer The structure 3 is located between the first insulating layer 2 and the second insulating layer 5; the first bonding layer 6 is formed on the second insulating layer 5, so that the second insulating layer 5 is located between the metal layer structure 3 and the second insulating layer 5. Between an adhesive layer 6 ; and a release layer 7 is formed on the first adhesive layer 6 , so that the first adhesive layer 6 is located between the second insulating layer 5 and the release layer 7 .

In this embodiment, the thickness of the carrier layer is 25 to 100 microns, for example: 25, 26, 27, 28, 29, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95 and 100 microns; the thickness of the first insulating layer is 2 to 10 microns, for example: 2, 3, 4, 5, 6, 7, 8, 9 and 10 microns; Thickness from 0.01 to 1.0 microns, for example: 0.01, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95 and 1.0 microns, more preferably 0.2 to 0.6 microns, and most preferably 0.6 microns; the thickness of the second insulating layer is 3 to 15 microns, for example: 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 12.5, 13, 14 and 15 microns; the thickness of the first adhesive layer is 3 to 25 microns, for example: 3, 4, 5, 6, 7, 8, 9, 10, 15, 20 and 25 microns; The mold layer is at least one of a release film with a thickness of 25 to 100 microns or a release paper with a thickness of 25 to 130 microns.

In a specific embodiment, the material of the carrier layer is polyethylene terephthalate (PET). In another specific embodiment, the carrier layer is one of a release film or a carrier film, the release film has a release agent on the surface, and the carrier film has an adhesive on the surface.

The carrier layer is the surface layer of the cover film of the present invention, which is used to protect the first insulating layer, and needs to have good processability, high mechanical strength, and abrasion resistance. In addition, through the design of the carrier layer, the first insulating layer has higher surface roughness and lower gloss. The second surface of the carrier layer is a rough surface with a surface roughness Rz greater than or equal to 0.8 microns, so as to adjust the surface gloss of the cover film of the present invention. On the other hand, since the cover film of the present invention includes a metal plating process, the carrier layer of the present invention needs to be resistant to high temperature. After the high temperature process, the surface release force of the carrier layer is no different from the initial release force.

In a specific embodiment, the first insulating layer is selected from epoxy resin, acrylic resin, polysulfone and polyester. at least one of the groups. Alternatively, selected from polyimide (PI), polyimide (PAI), polyether ether ketone (PEEK), polyhexamethylenediamine (polyamide 46), polyamide 1 ,4-cyclohexanedimethanol (PCT), polyurethane (PU), polyphenylene sulfide (PPS), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyethylene At least one of the group consisting of ether ash (PES), polyetherimide (PEI), polypropylene (PP), polystyrene (PS) and polycarbonate (PC). In another embodiment, the first insulating layer is a composite material selected from at least two of the above-mentioned groups.

In an embodiment, the glossiness of the first insulating layer measured at an angle of 60 degrees is 0 to 50 GU, preferably less than or equal to 5 GU, and the surface has a pencil hardness of more than 4H.

The first insulating layer is the exposed surface of the end product of the cover film of the present invention. In addition to the insulating function, the first insulating layer also needs to have the properties of low glossiness and high hardness. Therefore, the material of the first insulating layer of the present invention is preferably a material with a pencil hardness of 4H or higher on the surface after curing, so as to be directly formed on the carrier layer.

In a specific embodiment, the first insulating layer is an ink layer. The ink layer includes at least one selected from the group consisting of epoxy resin, acrylic resin, polysulfone and polyester. Alternatively, selected from polyimide (PI), polyimide (PAI), polyetheretherketone (PEEK), polyhexamethylenediamine (PA46), poly1,4-terephthalate Cyclohexanedimethanol (PCT), Polyurethane (PU), Polyphenylene Sulfide (PPS), Polyethylene Terephthalate (PET), Polyethylene Naphthalate (PEN), Polyether ( At least one polymer of the group consisting of PES), polyetherimide (PEI), polypropylene (PP), polystyrene (PS) and polycarbonate (PC).

In addition, the ink layer contains calcium sulfate, carbon black, titanium black, Nigrosine, silicon dioxide, titanium dioxide, zinc sulfide, zirconium oxide, calcium carbonate, silicon carbide, boron nitride, aluminum oxide, nitride At least one of the group consisting of powders of aluminum, talc, glass powder, quartz powder, clay and polyimide powder, wherein the content of the powder is 5 to 20% by weight of the ink layer. In another embodiment, the ink layer further comprises at least one selected from the group consisting of compounds of halogen, phosphorus, nitrogen and boron.

By adding the above powders and/or compounds, the gloss and hardness of the first insulating layer can be improved, and at the same time, the first insulating layer can be provided with flame retardancy and matte effect, and heat dissipation can be increased.

In one embodiment, the first insulating layer is polyimide. Because polyimide has good heat resistance and chemical resistance, high glass transition temperature (Tg≧300℃), low expansion coefficient, high dimensional stability, high elastic modulus, high elongation, high tensile strength and high The advantages of hardness (greater than or equal to 4H pencil hardness) are suitable for high temperature and high pressure processing, and its water absorption is low, and it has excellent reliability in high temperature and high humidity environments. Therefore, polyimide is used. As the first insulating layer of the present invention, it has the advantages of good electrical properties, good chemical resistance, high shielding performance, good bonding strength and good insulation effect. In addition, because the powder content is too high, the thin liquid polyimide film is prone to fail to form a film, which makes it difficult to prepare a polyimide film with a thickness of less than 7.5 microns in the prior art. The present invention prepares the polyimide layer by adding a solvent to reduce the solid content of the liquid polyimide film and increase the thickness of the liquid polyimide film, and the solvent is selected from N-methylpyrrolidone (NMP) , at least one of the group consisting of butanone (MEK), cyclohexanone and γ-butyrolactone (GBL). Therefore, the proportion of powder can be reduced, the solid content can be further reduced, and the solvent can be dried in the subsequent process. After drying, a polyimide layer with a thinner thickness can be obtained, which can overcome the polyimide film in the prior art. It is difficult to reach defects below 7.5 microns in thickness.

In one embodiment, the first insulating layer is polyimide imide. Due to the aromatic heterocyclic structure of polyamide imide, it has better heat resistance and low temperature resistance than other polymer materials, and has good dimensional stability, wear resistance, UV resistance, Resistance to high-energy radiation and low flammability and other properties. Polyamide imide also has the characteristics of high mechanical strength, high insulation, corrosion resistance, self-lubrication and low thermal expansion coefficient.

In a specific embodiment, when preparing the first insulating layer, a liquid polyimide or one of liquid polyimide imide is used, which contains calcium sulfate, carbon black, carbon dioxide, etc. Silicone, titanium dioxide, zinc sulfide, zirconium oxide, calcium carbonate, silicon carbide, boron nitride, aluminum oxide, aluminum nitride, talc, glass powder, quartz powder, clay and polyimide powder. At least one of the group, wherein the powder system accounts for 5 to 20 wt % of the first insulating layer. Since the powder content of the present invention is relatively low, the mechanical properties and insulating properties of the polyimide layer will not be affected.

In a specific embodiment, the first insulating layer is made of solid polyimide or one of solid polyimide imide. In addition to the solid polyimide or solid polyimide with low gloss, a carrier film with an adhesive on the surface can be used as the carrier layer, and the solid polyimide or solid polyimide and the solid polyimide can be used as the carrier layer. The adhesive on the carrier film is pasted, and the first insulating layer is combined with the rough surface of the carrier layer during lamination, so that the glossiness of the first insulating layer can meet the requirements of the present invention.

Since the surface roughness Rz value of the second surface of the carrier layer is greater than or equal to 0.8 μm, after the first insulating layer is formed on the second surface 1b of the carrier layer, the first insulating layer will also have a rough surface , thereby further reducing the gloss of the cover film of the present invention. By adjusting the powder content of the first insulating layer and the roughness of the surface of the carrier layer in contact with the first insulating layer, the gloss of the first insulating layer measured at an angle of 60 degrees is 0 to 50GU , in order to achieve higher haze, the gloss is preferably below 5GU.

By adjusting the powder content and the surface roughness of the carrier layer, the surface glossiness of the first insulating layer can be reduced, so as to achieve the goal of the glossiness being less than or equal to 5GU, and the first insulating layer of the present invention has good mechanical properties , friction resistance, aging resistance, chemical resistance and hardness, etc., can give full play to the role of scattering and extinction, so as to reduce the penetration of light, so as to protect the cover film of the present invention. In order to make the cover film of the present invention have the advantage of thinning, the first insulating layer needs to have the thinnest thickness as much as possible, and at the same time, it can play an insulating role.

In an embodiment, the metal layer structure includes a single metal layer or two metal layers in contact with each other. In another embodiment, the material of the single metal layer or the two metal layers in contact with each other is at least one selected from the group consisting of copper, nickel, cobalt, tin, silver, iron and gold. The metal layer structure of the present invention has excellent flexibility and wear resistance, improves oxidation resistance and conductivity, so as to achieve a higher shielding rate, and further improve the shielding performance and reliability of the cover film finished product.

The metal layer structure of the present invention is formed on the first insulating layer by evaporation method, sputtering method or electroplating method. Because both the evaporation method and the sputtering method are under vacuum conditions, metal or non-metallic films are deposited on the surface of the workpiece or substrate by means of evaporation or sputtering, so as to obtain an extremely thin surface coating, and at the same time, it has an operating speed. The advantages of fast, environmentally friendly process and good adhesion. In a specific embodiment, the method for forming the metal layer structure is preferably an evaporation method or a sputtering method.

The purpose of the metal layer structure is to enable the cover film of the present invention to have the function of shielding transmission signals. Since the thickness of the metal layer structure is related to the shielding performance, when the thickness of the metal layer structure is 0.6 μm, the cover film of the present invention can operate at 1 GHz. It can achieve a shielding effect of more than 70dB and has an excellent electromagnetic interference shielding effect.

In a specific embodiment, the second insulating layer is selected from epoxy resin, acrylic resin, polysulfone and polyester. at least one of the groups. Preferably selected from polyimide (PI), polyimide (PAI), polyether ether ketone (PEEK), polyhexamethylenediamine (polyamide 46), polyterephthalic acid 1,4-Cyclohexanedimethanol (PCT), Polyurethane (PU), Polyphenylene Sulfide (PPS), Polyethylene Terephthalate (PET), Polyethylene Naphthalate (PEN), Polyetherimide (PES), polyetherimide At least one of the group consisting of (PEI), polypropylene (PP), polystyrene (PS) and polycarbonate (PC). In another embodiment, the second insulating layer is a composite material selected from at least two of the above-mentioned groups.

In a specific embodiment, the second insulating layer contains calcium sulfate, carbon black, silicon dioxide, titanium dioxide, zinc sulfide, zirconium oxide, calcium carbonate, silicon carbide, boron nitride, aluminum oxide, aluminum nitride , talc powder, glass powder, quartz powder, clay and polyimide powder powders of at least one of the group consisting of powders, wherein the content of the powders is 5 to 20% by weight of the second insulating layer. In another embodiment, the second insulating layer further includes at least one selected from the group consisting of compounds of halogen, phosphorus, nitrogen and boron.

In a specific embodiment, the glossiness of the second insulating layer measured at an angle of 60 degrees is 0 to 50 GU, preferably less than or equal to 5 GU, and the surface has a pencil hardness of 4H or more.

In a specific embodiment, when preparing the second insulating layer, a liquid material can be selected, and it can be directly coated on the metal layer structure without adopting the design of the second adhesive layer.

In order to make the cover film of the present invention have the advantage of thinning, the second insulating layer needs to have the thinnest thickness as much as possible, and at the same time can play an insulating role.

The second insulating layer is the internal structure of the cover film of the present invention, which needs to have good mechanical, electrical and processing properties as required by the aforementioned first insulating layer.

In a specific embodiment, the first adhesive layer is selected from epoxy resins, acrylic resins, polyvinyl acetate resins (PVAC), urethanes, silicone resins, parylene resins, At least one of the group consisting of bismaleimide resin and polyimide resin. Specifically, the first adhesive layer does not affect the shielding effect of the overall cover film And the insulating effect of the adhesive layer. In addition, in order to make the cover film of the present invention have the advantage of thinning, the first adhesive layer also needs to meet the thinning requirement in terms of process conditions.

The first adhesive layer is located between the second insulating layer and the release layer, so as to improve the application range of the cover film and make the cover film more convenient to use.

The release layer is to protect the first adhesive layer from external contamination, and at the same time to make the cover film product of the present invention easy to roll and store. In a specific embodiment, the release film is at least one selected from the group consisting of PET fluorine release film, PET silicone oil release film, PET matte release film and PE release film; in another In a specific embodiment, the release paper is selected from one of single-sided or double-sided release PET coated papers.

The present invention further provides a method for preparing a cover film with electromagnetic interference shielding function, which includes: forming a first insulating layer on the carrier layer; forming a metal layer structure on the first insulating layer; forming a second insulating layer on the metal layer structure; forming a first adhesive layer on the second insulating layer; and forming a release layer on the first adhesive layer. In another specific embodiment, a first adhesive layer is formed on the release layer, and then the first adhesive layer is attached to the second insulating layer, so that the first adhesive layer is located on the second insulating layer and the release layer. between layers.

As shown in FIG. 2, a specific embodiment of the cover film with electromagnetic interference shielding function of the present invention is shown, which includes: a carrier layer 1 having an opposite first surface 1a and a second surface 1b, and the first surface 1a and the second surface 1b are opposite to each other. The surface roughness of the two surfaces 1b is greater than the surface roughness of the first surface 1a; the first insulating layer 2 is formed on the second surface 1b of the carrier layer 1; the metal layer structure 3 is formed on the first insulating layer On the layer 2, the first insulating layer 2 is located between the carrier layer 1 and the metal layer structure 3; the second bonding layer 4 is formed on the metal layer structure 3, so that the metal layer structure 3 is located in the first insulating layer Between the layer 2 and the second bonding layer 4; the second insulating layer 5 is formed on the second bonding layer 4, so that the second adhesive layer 4 is located between the metal layer structure 3 and the second insulating layer 5; the first adhesive layer 6 is formed on the second insulating layer 5, so that the second insulating layer 5 is located Between the second adhesive layer 4 and the first adhesive layer 6; and the release layer 7 is formed on the first adhesive layer 6, so that the first adhesive layer 6 is located between the second insulating layer 5 and the release layer between 7.

In an embodiment, the thickness of the second adhesive layer is 3 to 10 microns, for example: 3, 4, 5, 6, 7, 8, 9 and 10 microns.

In a specific embodiment, the second adhesive layer is selected from epoxy resins, acrylic resins, polyvinyl acetate resins (PVAC), urethanes, silicone resins, parylene resins, At least one of the group consisting of bismaleimide resin and polyimide resin. Specifically, the second adhesive layer is an adhesive layer that does not affect the shielding effect and insulating effect of the overall cover film. In addition, in order to make the cover film of the present invention have the advantage of thinning, the second adhesive layer also needs to meet the thinning requirement in terms of process conditions.

In a specific embodiment, the second insulating layer is a solid material. Since the solid material and the metal layer structure are both dry and rough surfaces, the second insulating layer using the solid material cannot be directly attached to the metal layer structure. Therefore, through the design of disposing the second adhesive layer between the metal layer structure and the second insulating layer, the second insulating layer and the metal layer structure are closely attached.

In a specific embodiment, the preparation method includes: forming a first insulating layer on the carrier layer; forming a metal layer structure on the first insulating layer; forming a second bonding layer on the metal layer structure; forming a first Two insulating layers are formed on the second adhesive layer; a first adhesive layer is formed on the second insulating layer; and a release layer is formed on the first adhesive layer.

In another embodiment, a second adhesive layer is formed on the second insulating layer, and then the second adhesive layer is attached to the metal layer structure, so that the second adhesive layer is located on the metal layer structure and the second insulating layer between.

In another specific embodiment, a first adhesive layer is formed on the release layer, and then the first adhesive layer is attached to the second insulating layer, so that the first adhesive layer is located on the second insulating layer and the release layer. between layers.

The following describes the stack structure and performance of the cover film with electromagnetic interference shielding function of the present invention through examples and comparative examples. In Examples 1 to 7, the first insulating layer is an ink layer, and the ink layer is one of epoxy resin or acrylic resin, and the ink layer contains carbon black, aniline black, titanium black, titanium dioxide or oxide. Powder of at least one of the group consisting of aluminum. The second insulating layer is a polyimide layer, the first adhesive layer is epoxy resin, the metal layer structure is copper, and the metal layer structure of Examples 1 and 5 is a single-layer metal layer, Examples 2 to 4, 6 and The metal layer structure of 7 is a double metal layer in contact with each other, and the second adhesive layer of Examples 4 to 7 uses acrylic resin. The metal layer structures of Comparative Examples 4 and 5 are copper, the metal layer structure of Comparative Example 4 is a single-layer metal layer, and the metal layer structure of Comparative Example 5 is a double-layer metal layer in contact with each other.

Table 1 shows the thickness of each layer of the cover films with electromagnetic interference shielding function of Examples 1 to 7, wherein Examples 1 to 3 are cover films without the second adhesive layer structure, and Examples 4 to 7 are the cover films with the second adhesive layer structure. Next, the cover film of the layer structure, Comparative Examples 1 to 3 are the thickness of each layer of the cover film, Comparative Examples 4 and 5 are the thickness of each layer of the shielding film, and the first insulating layer of Comparative Examples 4 and 5 is a black insulating layer, and the second The next layer is a conductive adhesive layer.

Table 2 shows the test results of gloss, pencil hardness, resistance value, peel strength and shielding property of Examples 1 to 7 and Comparative Examples 1 to 5.

Thickness is measured with a digital micrometer (three quantities, 0-25mm specification); gloss is measured with a single-angle gloss meter (Colour Spectrum, CS-300); pencil hardness according to standard test method IPC-TM-650 2.3 .17.1 test method; resistance value is tested by grounding resistance tester (Sima, AR4105A); peel strength is tested according to standard test method IPC-TM650 2.4.9 test method; EMI shielding is based on soft board assembly requirements Tested according to test guideline TPCA-F-002.

As can be seen from Table 2, the cover films of Examples 1 to 7 of the present invention are thinner than the cover films of Comparative Examples 1 to 3, and the thinnest can reach about 9 or 10 microns, and the cover films of the present invention are The film has good conductivity and shielding properties, and its surface has a very low gloss (about 1.5GU). In addition, it can be seen from Table 2 that when the cover film is manufactured with a metal layer structure with a thickness of 0.2 microns, the shielding performance of the cover film is 55dB, and when a metal layer structure with a thickness of 0.6 microns is used, its shielding performance can reach 75dB From the above, it is obvious that the thickness of the metal layer structure directly affects the electrical conductivity. It can be seen from the above that the metal layer structure with a thickness of 0.6 μm can achieve good conduction and has good reliability.

In order to show that the cover film with electromagnetic interference shielding function of the present invention has good shielding effect and conduction effect, the cover films with electromagnetic interference shielding function of the present invention of Examples 8 and 9 and the prior art of Comparative Examples 4 and 5 were used. The shielding films were tested and compared. The overall thicknesses of Examples 8 and 9 and Comparative Examples 4 and 5 were all 16 microns. The comparison of the test results is recorded in Table 3. In addition, the stacked structures of Examples 8 and 9 are the same as those of Example 4 in Table 1, and the components of the first insulating layer, the first adhesive layer, the second insulating layer and the second adhesive layer in Examples 8 and 9 are all The same, the difference is that the metal layer structure of Example 8 is a single-layer metal layer, and its thickness is 0.2 μm, and the metal layer structure of Example 9 is two metal layers in contact with each other, and its thickness is 0.6 μm; The composition of the first insulating layer and the first adhesive layer in Comparative Examples 4 and 5 are the same, the difference is that the metal layer structure of Comparative Example 4 is a single-layer metal layer, and its thickness is 0.2 μm, and the metal layer structure of Comparative Example 5 is are two metal layers in contact with each other, and their thickness is 0.6 microns.

It can be seen from Table 2 that when the total thickness is the same, when the thickness of the metal layer structure reaches 0.6 microns, the shielding effect is the best, which can reach more than 70 dB, the best can reach 75 dB, and it also has 55 dB under the thickness of 0.2 microns. The above shielding effect. At the same time, at 85°C and relative humidity After 100 hours at a temperature of 85%, it can still maintain an excellent shielding effect, showing that it has excellent reliability.

It can be seen from the test results in Tables 2 and 3 that the cover film with electromagnetic interference shielding function of the present invention has good flexibility, good electrical properties, good chemical resistance, good adhesion strength, less transmission loss, and transmission quality. High reliability and high shielding performance, and the cover film of the present invention not only has the excellent shielding effect of the general thin shielding film, but also has the insulating function of the cover film, and can replace the general shielding film and cover film and other materials.

The above-mentioned embodiments are only illustrative, 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 the right protection of the present invention is defined by the scope of the patent application attached to the present invention, as long as the effect and implementation purpose of the present invention are not affected, it shall be included in the technical content disclosed herein.

1‧‧‧Carrier layer

1a‧‧‧First surface

1b‧‧‧Second surface

2‧‧‧First insulating layer

3‧‧‧Metal layer structure

5‧‧‧Second insulating layer

6‧‧‧First Adhering Layer

7‧‧‧Release layer

Claims (11)

A cover film with electromagnetic interference shielding function, comprising: a carrier layer, which has a first surface and a second surface opposite to each other, and the surface roughness of the second surface is greater than the surface roughness of the first surface, wherein the The surface roughness Rz value of the second surface of the carrier layer is greater than or equal to 0.8 microns; the first insulating layer with a thickness of 2 to 10 microns is formed on the second surface of the carrier layer; the metal thickness of 0.01 to 1.0 microns A layer structure is formed on the first insulating layer, so that the first insulating layer is located between the carrier layer and the metal layer structure; a second insulating layer with a thickness of 3 to 15 microns is formed on the metal layer structure , so that the metal layer structure is located between the first insulating layer and the second insulating layer, wherein the glossiness of the first insulating layer and the second insulating layer measured at a 60-degree angle is 0 to 50GU, and has 4H The above surface pencil hardness; and a first adhesive layer with a thickness of 3 to 25 microns are formed on the second insulating layer, so that the second insulating layer is located between the metal layer structure and the first adhesive layer. The cover film according to claim 1, wherein the carrier layer has a thickness of 25 to 100 microns. The cover film as described in claim 1 of the claimed scope further comprises a second adhesive layer with a thickness of 3 to 10 microns, which is formed on the metal layer structure, so that the metal layer structure is located between the first insulating layer and the second adhesive layer. between layers. The cover film according to claim 3, wherein the second insulating layer is located between the second adhesive layer and the first adhesive layer. The cover film according to claim 1, wherein the glossiness of the first insulating layer and the second insulating layer measured at an angle of 60 degrees is 5GU or less. The cover film according to claim 1, wherein the thickness of the metal layer structure is 0.2 to 0.6 microns. The cover film of claim 1, wherein the metal layer structure comprises a single metal layer or two metal layers in contact with each other. The cover film as described in claim 7, wherein the material for forming the single-layer metal layer or the two-layer metal layer is at least one selected from the group consisting of copper, nickel, cobalt, tin, silver, iron and gold A sort of. A method for preparing a cover film with electromagnetic interference shielding function as described in item 1 of the scope of the patent application, comprising: forming a first insulating layer on a carrier layer; forming a metal layer structure on the first insulating layer; forming a first insulating layer Two insulating layers are formed on the metal layer structure; and a first bonding layer is formed on the second insulating layer. The preparation method according to claim 9, wherein before forming the second insulating layer on the metal layer structure, a second adhesive layer is first formed on the metal layer structure. The preparation method according to claim 9, wherein before forming the second insulating layer on the metal layer structure, a second adhesive layer is formed on the second insulating layer, and the second adhesive layer is formed on the second insulating layer. It is attached to the metal layer structure so that the second adhesive layer is located between the metal layer structure and the second insulating layer.

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