TW202041135A - 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, and more particularly to a cover film with electromagnetic interference shielding function.

Under the market demand of electronic and communication products becoming more multifunctional and complex, the structure of the circuit substrate needs to be lighter, thinner and shorter, and in terms of function, it needs powerful and high-speed signal transmission.

With the development of electronic products in the market toward a trend toward lightness and thinness, in order to reduce the overall thickness of a flexible printed circuit (FPC), it is necessary to provide a thinner cover film to cover the FPC. Generally, the cover film used on FPC is mostly insulating material, the most common thickness is 37.5 microns and 50 microns, and the thinnest thickness that the cover film can reach is about 19 microns, which is difficult to achieve thinner thickness.

Among black polyimide-type cover films, polyimide materials have become the most widely used cover film due to their special mechanical processing properties, but this type of cover film still has its drawbacks. For example, it is difficult to make a black polyimide film with a thickness of 5 microns or less, and its processing operability is not good, and there is a certain bottleneck in thinning. For aesthetics, visual protection, and non-exposure of the circuit, a cover film with a thickness of ≤ 7.5 microns is required. However, the current common black polyimide film is produced The production method uses casting. When the thickness of the black polyimide film is designed to be 5 to 7.5 microns, the film produced by the existing method cannot meet the specifications of the industry, making the process and material selection more stringent . In addition, the black insulating layer of the general cover film cannot achieve a sufficiently low surface gloss (less than or equal to 5GU), although it is possible to add a matte material such as carbon black or titanium black to the insulating material to make it a matte surface. However, the addition of the above matting materials 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, making the surface of the film low gloss is one of the process difficulties.

As electronic signal transmission is more high-speed and dense, the line density will inevitably increase, making the distance between the substrate lines closer, and the application frequency is going to be higher and wider, making the electromagnetic interference (EMI) situation more and more serious, so it must be effectively managed Electromagnetic Compatibility (EMC), so as to maintain the normal signal transmission of electronic products and improve reliability. The characteristics of being thin and flexible, making FPC play a pivotal role in the development of the portable information and communication electronics industry. Today's EMI shielding films are more stringent in terms of their thickness and shielding function. The general cover film shielding rate is about 55dB, and it is difficult to achieve 70dB or even higher shielding effects. Therefore, while pursuing thinning, make A film with a higher shielding rate is also one of the difficulties.

It can be seen from the above that the general cover film only has the function of insulation and does not have the effect of EMI shielding. With the increasing demand for these two functions in electronic products nowadays, how to make one based on the original thin cover film Thin cover film products with EMI shielding function should be a problem that needs to be solved.

In order to solve the above problems, the present invention provides a cover film with electromagnetic interference shielding function, which includes: a carrier layer having a first surface and a second surface opposite to each other, 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, the gloss of the first insulating layer and the second insulating layer measured at a 60 degree angle is 0 to 50 GU, and has a surface pencil hardness of 4H or more; and a thickness of 3 to 25 microns The first bonding layer is formed on the second insulating layer so that the second insulating layer is located between the metal layer structure and the first bonding layer.

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

In another embodiment, a second adhesive layer with a thickness of 3-10 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 bonding layer and the first bonding 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 μm.

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

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

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

In a specific implementation aspect, before forming the second insulating layer on the metal layer structure, a second adhesive layer is 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 formed on the second insulating layer, and the second adhesive layer is bonded to the metal layer structure , The second bonding layer is located between the metal layer structure and the second insulating layer.

The covering film with electromagnetic interference shielding function of the present invention uses high pencil hardness (pencil hardness greater than or equal to 4H) and low gloss (gloss at an angle of 60° is less than or equal to 50GU) and satisfies mechanical and electrical characteristics. As the first insulating layer, ensure that the insulating layer has a good insulating effect and a very thin thickness (thickness of 2 to 10 microns) during preparation, and the second surface of the carrier layer is designed as the surface roughness Rz value With a rough surface greater than or equal to 0.8 microns, the second surface is in contact with the first insulating layer, and the surface of the first insulating layer also has a certain degree of roughness, so that the finished cover film can best achieve a gloss of 60° The degree is less than or equal to 50GU.

On the other hand, if the thickness of the first and second insulating layers is too thick, the metal layer structure provided between the first and second insulating layers will not be conductive when the subsequent cover film is applied. Therefore, In the manufacturing process, the thickness of the first and second insulating layers will be 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. In order to realize the conduction function when the final product is applied, the thickness of the metal layer structure 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, the metal layer structure of the present invention is used in combination with the first insulating layer. While the first insulating layer exerts an insulating effect, the metal layer structure can achieve a good electromagnetic signal interference shielding effect. The shielding effect of 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 70dB at 1GHz.

The covering film of the present invention has the function of insulating the electronic circuit and the function of shielding the transmission signal. In the manufacturing process, 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 reaching 9 to 10 microns, and its surface has higher hardness (more than 4H) Pencil hardness), very low gloss (less than or equal to 5GU gloss), good mechanical properties, and excellent shielding effect (greater than or equal to 70dB). In terms of subsequent storage of the product, since the present invention includes the electromagnetic interference shielding structure in the cover film structure, the storage method can be stored in the same manner as the general cover film.

1‧‧‧Carrier layer

1a‧‧‧First surface

1b‧‧‧Second surface

2‧‧‧First insulation layer

3‧‧‧Metal layer structure

4‧‧‧Second layer

5‧‧‧Second insulation layer

6‧‧‧The first subsequent layer

7‧‧‧Release layer

The embodiments of the present invention will be described with reference to the drawings as an example: Figure 1 is a schematic diagram of the structure of the cover film with electromagnetic interference shielding function of the present invention.

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

The following is a specific embodiment to illustrate the implementation of the present invention. Those skilled in the art can easily understand the advantages and effects of the present invention from the content disclosed in this specification.

It should be noted that the structures, proportions, sizes, etc. shown in the drawings in this manual are only used to match the contents disclosed in the manual for the understanding and reading of those familiar with the art, and are not intended to limit the implementation of the present invention Therefore, it does not have any technical significance. Any structural modification, proportional relationship change, or size adjustment should still fall within the scope of the present invention without affecting the effects and objectives that can be achieved. The technical content disclosed by the invention can be covered. At the same time, references such as "一", "下" and "上" in this specification are only for ease of description, and are not used to limit the scope of the present invention. Changes or adjustments to their relative relationships are Substantial changes to the technical content should also be regarded as the scope of the present invention. In addition, all ranges and values herein are inclusive and combinable. Any value or point falling within the range described herein, for example, any integer can be used as the minimum or maximum value to derive the lower range and so on.

As shown in Figure 1, it shows a specific implementation of the cover film with electromagnetic interference shielding function of the present invention, which includes: a carrier with opposite first surface 1a and 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 Between a bonding layer 6; and, a release layer 7 is formed on the first bonding layer 6 so that the first bonding 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; the metal layer structure The thickness is 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 Micrometers, more preferably 0.2 to 0.6 micrometers, most preferably 0.6 micrometers; the thickness of the second insulating layer is 3 to 15 micrometers, 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; and, the separation 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 embodiment, the carrier layer is one of a release film or a carrier film, and the surface of the release film has a release agent, and the surface of the carrier film has an adhesive.

The carrier layer is the surface layer of the cover film of the present invention and is used to protect the first insulating layer. It needs to have good processability, high mechanical strength, and friction resistance. In addition, through the design of the carrier layer, the first insulating layer has higher surface roughness and lower gloss. Since the gloss is also related to the roughness of the carrier layer, it makes contact with the first insulating layer. The second surface of the carrier layer is a rough surface with a surface roughness Rz value 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 withstand high temperature. After the high temperature process, the surface release force of the carrier layer is not different from the initial release force.

In a specific embodiment, the first insulating layer is selected from epoxy resins, acrylic resins, polysulfones and polyesters. At least one of the groups. Or, selected from polyimide (PI), polyimide imine (PAI), polyether ether ketone (PEEK), polybutylene hexamethylene diamine (polyamide 46), polyterephthalic acid 1 , 4-cyclohexanedimethanol (PCT), polyurethane (PU), polyphenylene sulfide (PPS), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), poly At least one of the group consisting of Ether Sulfate (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 groups.

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

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 effect, it also needs to have low gloss and high hardness. Therefore, the material of the first insulating layer of the present invention is preferably a material having a pencil hardness of 4H or more on the surface after curing, so as to be directly formed on the carrier layer.

In a specific implementation aspect, 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. Or, selected from polyimide (PI), polyimide imine (PAI), polyether ether ketone (PEEK), polybutylene adipamide (PA46), polyterephthalic acid 1,4- Cyclohexane dimethyl ester (PCT), polyurethane (PU), polyphenylene sulfide (PPS), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyether sulfide ( At least one polymer in the group consisting of PES), polyetherimide (PEI), polypropylene (PP), polystyrene (PS) and polycarbonate (PC).

In addition, the ink layer contains selected from calcium sulfate, carbon black, titanium black, Nigrosine, silicon dioxide, titanium dioxide, zinc sulfide, zirconium oxide, calcium carbonate, silicon carbide, boron nitride, aluminum oxide, and nitride At least one of the 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 includes at least one selected from the group consisting of halogen, phosphorus, nitrogen, and boron compounds.

By adding the above-mentioned powders and/or compounds, the gloss and hardness of the first insulating layer can be improved, and at the same time, it can have flame retardancy and matte effects, and increase heat dissipation.

In a specific 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 modulus of elasticity, high elongation, high tensile strength and high Hardness (pencil hardness greater than or equal to 4H) and other advantages, suitable for high temperature and high pressure processing, and its water absorption rate is low, and it has excellent reliability in high temperature and high humidity environments. Therefore, use polyimide As the first insulating layer of the present invention, it has the advantages of good electrical characteristics, good chemical resistance, high shielding performance, good bonding strength and good insulation effect. In addition, because the powder content is too high, a 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. The solvent is selected from N-methylpyrrolidone (NMP) , At least one of the group consisting of MEK, cyclohexanone and gamma-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 thinner polyimide layer can be obtained, which can overcome the polyimide film in the prior art. The thickness is difficult to reach defects below 7.5 microns.

In a specific implementation aspect, the first insulating layer is polyamide imide. Because polyamide imine has an aromatic heterocyclic structure, it has better heat resistance and low temperature resistance than other polymer materials, and has good dimensional stability, abrasion resistance, UV resistance, and Resistance to high-energy radiation and low flammability. 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, one of liquid polyimide or liquid polyimide is used, which contains selected from calcium sulfate, carbon black, and A group of powders composed of silicon, 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% by weight of the first insulating layer. Since the powder content of the present invention is relatively low, it will not affect the mechanical properties and insulation properties of the polyimide layer.

In a specific implementation aspect, the first insulating layer uses one of solid polyimide or solid polyimide. In order to make the gloss of the first insulating layer meet the requirements of the present invention, in addition to selecting itself In addition to solid polyimide or solid polyimide imide with lower gloss, a carrier film with adhesive on the surface can be used as the carrier layer, and solid polyimide or solid polyimide imide can be combined with the solid polyimide or solid polyimide imide. The adhesive on the carrier film is attached, and the first insulating layer is combined with the rough surface of the carrier layer during pressing, so that the gloss of the first insulating layer meets 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 microns, after the first insulating layer is formed on the second surface 1b of the carrier layer, the first insulating layer will also exhibit 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 surface roughness of the carrier layer in contact with the first insulating layer, the gloss of the first insulating layer is measured at a 60 degree angle from 0 to 50 GU To achieve a higher haze, the gloss is preferably less than 5GU.

By adjusting the powder content and the surface roughness of the carrier layer, the surface glossiness of the first insulating layer is reduced, so as to achieve the goal of glossiness 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 high hardness, etc., can fully play the role of scattering and extinction to reduce light penetration, thereby protecting the cover film of the present invention. In order to make the cover film of the present invention have the advantage of being thinner, the first insulating layer needs to have the thinnest thickness as much as possible, and at the same time can play an insulating function.

In one 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 selected from at least one of 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 improves the shielding performance and reliability of the finished cover film.

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

The purpose of the metal layer structure is to make the cover film of the present invention 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 microns, the cover film of the present invention works 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 resins, acrylic resins, polysulfones and polyesters. At least one of the groups. It is preferably selected from polyimide (PI), polyimide imide (PAI), polyether ether ketone (PEEK), polybutylene hexamethylene diamine (polyamide 46), polyterephthalic acid 1,4-cyclohexanedimethanol (PCT), polyurethane (PU), polyphenylene sulfide (PPS), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), Polyether sulfide (PES), polyether imide 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 groups.

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

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

In a specific implementation aspect, 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 being thinner, the second insulating layer needs to have the thinnest thickness possible, and at the same time can play an insulating function.

The second insulating layer is the internal structure of the cover film of the present invention, and it needs to have good mechanical, electrical, and processing characteristics as 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 being thinner, the first adhesive layer also needs to meet the thinning requirements in terms of manufacturing process conditions.

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

The release layer protects the first adhesive layer from external pollution, and at the same time makes the covering film product of the present invention easy to rewind and store. In a specific embodiment, the release film is selected from at least one of the group consisting of PET fluorine release film, PET silicone oil release film, PET matte release film and PE release film; In a specific implementation aspect, the release paper is selected from one of single-sided or double-sided release PET coated paper.

The present invention also provides a method for preparing a cover film with electromagnetic interference shielding function, which includes: forming a first insulating layer on a carrier layer; forming a metal layer structure on the first insulating layer; forming a second insulating layer on the metal layer Structurally; forming a first bonding layer on the second insulating layer; and forming a release layer on the first bonding layer. In another embodiment, a first bonding layer is formed on the release layer, and then the first bonding layer and the second insulating layer are bonded together so that the first bonding layer is located on the second insulating layer and the release layer Between layers.

As shown in Figure 2, it shows a specific implementation of the cover film with electromagnetic interference shielding function of the present invention, which includes: a carrier layer 1 having a first surface 1a and a second surface 1b opposite to each other, and the 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 layer 2, the first insulating layer 2 is located between the carrier layer 1 and the metal layer structure 3; the second adhesive layer 4 is formed on the metal layer structure 3 so that the metal layer structure 3 is located on the first insulating layer Between layer 2 and the second adhesive layer 4; the second insulating layer 5 is formed on the second adhesive layer 4, 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 on the second insulating layer 5 and the release layer Between 7.

In a specific embodiment, the thickness of the second adhesive layer is 3-10 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 being thinner, the second adhesive layer also needs to meet the thinning requirements in terms of manufacturing process conditions.

In a specific embodiment, the second insulating layer is a solid material. Because the solid material and the metal layer structure are dry and rough surfaces, it is impossible to directly bond the second insulating layer using the solid material to the metal layer structure Therefore, by placing the second bonding 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 adhesive layer on the metal layer structure; 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 bonded to the metal layer structure so that the second adhesive layer is located between the metal layer structure and the second insulating layer between.

In another embodiment, a first bonding layer is formed on the release layer, and the first bonding layer and the second insulating layer are bonded together so that the first bonding layer is located on the second insulating layer and the release layer Between layers.

The following examples and comparative examples illustrate the laminated structure and performance of the covering film with electromagnetic interference shielding function of the present invention. In Examples 1 to 7, the first insulating layer is an ink layer, the ink layer is one of epoxy resin or acrylic resin, and the ink layer contains selected from 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 metal layer, examples 2 to 4, 6 and The metal layer structure of 7 is a two-layer metal layer in contact with each other, and the second adhesive layer of Examples 4 to 7 uses acrylic resin. The metal layer structure of Comparative Examples 4 and 5 is 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 film with electromagnetic interference shielding function of Examples 1 to 7. Among them, Examples 1 to 3 are cover films without a second adhesive layer structure, and Examples 4 to 7 have second Then 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 gloss, pencil hardness, resistance value, peel strength and shielding test results of Examples 1 to 7 and Comparative Examples 1 to 5.

The thickness is measured with a digital outside micrometer (three quantities, 0-25mm specifications); the gloss is measured with a single-angle gloss meter (color spectrum, CS-300); the pencil hardness is measured according to the standard test method IPC-TM-650 2.3 .17.1 The test method is used for testing; the resistance value is tested with a grounding resistance tester (Xima, AR4105A); the peel strength is tested according to the standard test method IPC-TM650 2.4.9; the EMI shielding performance is based on the soft board assembly requirements Test criteria TPCA-F-002 for testing.

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

In order to show that the covering film with electromagnetic interference shielding function of the present invention has good shielding effect and conduction effect, the covering film with electromagnetic interference shielding function of the present invention of Examples 8 and 9 and the prior art of Comparative Examples 4 and 5 The performance test and comparison of the shielding film were performed. Among them, the overall thickness of Examples 8, 9 and Comparative Examples 4 and 5 were all 16 microns, and the comparison of the test results was recorded in Table 3. In addition, the stacking structure of Examples 8 and 9 is the same as that of Example 4 in Table 1, and the composition of the first insulating layer, the first bonding layer, the second insulating layer, and the second bonding layer in Examples 8 and 9 are all The same, the difference is that the metal layer structure of Example 8 is a single metal layer, and its thickness is 0.2 microns, and the metal layer structure of Example 9 is two metal layers in contact with each other, and the thickness is 0.6 microns; The composition of the first insulating layer and the first bonding 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 microns. The metal layer structure of Comparative Example 5 They 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 70dB, the best can reach 75dB, and it also has 55dB at a thickness of 0.2 microns. The above shielding effect. At the same time, at 85℃ and relative humidity After 100 hours at 85%, the excellent shielding effect can still be maintained, showing its excellent reliability.

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

The above-mentioned embodiments are only illustrative and not used to limit the present invention. Anyone familiar with this technique can modify and change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the rights of the present invention is defined by the scope of the patent application attached to the present invention. As long as it does not affect the effect and implementation purpose of the present invention, it should be covered in the technical content of this disclosure.

1‧‧‧Carrier layer

1a‧‧‧First surface

1b‧‧‧Second surface

2‧‧‧First insulation layer

3‧‧‧Metal layer structure

5‧‧‧Second insulating layer

6‧‧‧The first subsequent layer

7‧‧‧Release layer

Claims (12)

A cover film with electromagnetic interference shielding function, comprising: a carrier layer having a first surface and a second surface opposite, and the surface roughness of the second surface is greater than the surface roughness of the first surface; the thickness is 2 A first insulating layer with a thickness of up 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 on the 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 gloss of the first insulating layer and the second insulating layer measured at a 60 degree angle is 0 to 50 GU, and has a surface pencil hardness of 4H or more; and a first adhesive layer with a thickness of 3 to 25 microns is formed On the second insulating layer, the second insulating layer is located between the metal layer structure and the first adhesive layer. According to the cover film described in item 1 of the scope of patent application, the thickness of the carrier layer is 25 to 100 microns. The covering film described in item 1 of the scope of the patent application includes 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 insulating layer. Then between the layers. According to the cover film described in item 3 of the scope of patent application, the second insulating layer is located between the second adhesive layer and the first adhesive layer. The covering film according to the first item of the scope of patent application, wherein the surface roughness Rz value of the second surface of the carrier layer is greater than or equal to 0.8 microns. According to the cover film described in the first item of the scope of patent application, the gloss of the first insulating layer and the second insulating layer measured at a 60 degree angle is less than 5GU. According to the cover film described in item 1 of the scope of patent application, the thickness of the metal layer structure is 0.2 to 0.6 microns. The cover film according to the first item of the patent application, wherein the metal layer structure includes a single metal layer or two metal layers in contact with each other. The covering film according to item 8 of the scope of patent application, wherein the material for forming the single metal layer or the two metal layers is selected from the group consisting of copper, nickel, cobalt, tin, silver, iron and gold at least One kind. A method for preparing a cover film with electromagnetic interference shielding function includes: forming a first insulating layer on a 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 adhesive layer on the second insulating layer. According to the manufacturing method described in claim 10, before forming the second insulating layer on the metal layer structure, a second adhesive layer is formed on the metal layer structure. The manufacturing method according to claim 10, wherein, before forming the second insulating layer on the metal layer structure, a second bonding layer is formed on the second insulating layer, and the second bonding 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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