CN114641194A - Electromagnetic shielding film and circuit board - Google Patents

Abstract

The invention relates to the technical field of electronics, and discloses an electromagnetic shielding film and a circuit board, wherein the electromagnetic shielding film comprises an insulating layer, a shielding layer and an adhesive film layer; the shielding layer is formed on one surface of the insulating layer, and the adhesive film layer is arranged on one surface, far away from the insulating layer, of the shielding layer; wherein, under the unit of the adhesive gram weight parameter being gram per square decimeter, the ratio of the roughness Sdr of one surface of the insulating layer close to the shielding layer to the adhesive gram weight parameter of the adhesive film layer is 0.2-20000. The electromagnetic shielding film and the circuit board provided by the invention have the following advantages at the same time: the circuit board has good adhesive strength with the circuit board and good appearance after being pressed and combined on the circuit board.

Description

Electromagnetic shielding film and circuit board

Technical Field

The invention relates to the technical field of electronics, in particular to an electromagnetic shielding film and a circuit board.

Background

With the rapid development of the electronic industry, electronic products are further miniaturized, light-weighted and densely assembled, and the development of flexible circuit boards is greatly promoted, so that the integration of element devices and wire connection is realized. The flexible circuit board can be widely applied to industries such as mobile phones, liquid crystal display, communication, aerospace and the like.

Under the push of the international market, the functional flexible printed circuit board is dominant in the flexible printed circuit board market, and an important index for evaluating the performance of the functional flexible printed circuit board is Electromagnetic Shielding (EMI Shielding). With the integration of the functions of communication equipment such as mobile phones, the internal components thereof are rapidly high-frequency and high-speed. For example: besides the original audio transmission function, the camera function has become a necessary function, and WLAN (Wireless Local Area network), GPS (Global Positioning System) and internet function have become popular, and the integration of the sensing component in the future makes the trend of rapid high-frequency and high-speed of the component unavoidable. Problems of electromagnetic interference inside and outside the device, signal attenuation during transmission, insertion loss, and jitter caused by high-frequency and high-speed driving are becoming serious.

At present, an electromagnetic shielding film commonly used for an existing circuit board comprises an insulating layer, a shielding layer and a glue film layer, wherein the shielding layer is formed on one surface of the insulating layer, one surface, close to the glue film layer, of the shielding layer has roughness and can pierce through the glue film layer to be in contact connection with a stratum of the circuit board, and then interference charges are led into the stratum of the circuit board, so that shielding is achieved.

The inventor finds that the following technical problems exist in the prior art in the process of implementing the invention: in the process of laminating the existing electromagnetic shielding film on the circuit board, the glue of the glue film layer is easy to overflow from the edge between the electromagnetic shielding film and the circuit board, so that the circuit board has the problem of poor appearance; in order to avoid the situation that glue of the glue film layer easily overflows from the edge between the electromagnetic shielding film and the circuit board in the laminating process of the electromagnetic shielding film, the glue amount of the glue film layer can be reduced or smaller laminating force is applied, but the two modes can cause the phenomenon of layering and board explosion between the electromagnetic shielding film and the circuit board easily.

Disclosure of Invention

In view of the above problems, an object of the present invention is to provide an electromagnetic shielding film and a circuit board, which can simultaneously have the following advantages: the circuit board has good adhesive strength with the circuit board and good appearance after being pressed on the circuit board.

In order to achieve the above object, an embodiment of the present invention provides an electromagnetic shielding film, including an insulating layer, a shielding layer, and a glue film layer;

the shielding layer is formed on one surface of the insulating layer, and the adhesive film layer is arranged on one surface, far away from the insulating layer, of the shielding layer;

wherein, under the unit of the adhesive gram weight parameter being gram per square decimeter, the ratio of the roughness Sdr of one surface of the insulating layer close to the shielding layer to the adhesive gram weight parameter of the adhesive film layer is 0.2-20000.

In an improvement of the above scheme, the roughness Sdr of the surface of the insulating layer close to the shielding layer is 0.1% -8000%.

As an improvement of the scheme, the grammes weight parameter of the adhesive film layer is 0.01-1 g per square decimeter.

As an improvement of the above scheme, the ratio of the roughness Sdr of the side of the insulating layer close to the shielding layer to the thickness of the shielding layer is 0.1-335.

As an improvement of the scheme, the shielding layer is provided with a through hole penetrating through the upper surface and the lower surface of the shielding layer.

As an improvement of the scheme, the number of the through holes per square centimeter on the shielding layer is 1-1000 on average.

As a refinement of the above aspect, the electromagnetic shielding film further includes a carrier layer; the carrier layer is arranged on one surface of the insulating layer, which is far away from the shielding layer.

As a modification of the above, the insulating layer is formed on one side of the carrier layer; the ratio of the roughness Sdr of the one side of the carrier layer to the thickness of the insulating layer is 0.05-12.

As an improvement of the scheme, a conductive protrusion is arranged on one surface of the shielding layer close to the adhesive film layer.

In order to solve the same technical problem, another embodiment of the present invention further provides a circuit board, which includes a circuit board body and the electromagnetic shielding film according to any one of the above aspects; the electromagnetic shielding film is pressed with the circuit board body through the adhesive film layer; one surface of the shielding layer, which is close to the glue film layer, pierces the glue film layer and is electrically connected with the ground layer of the circuit board body.

Compared with the prior art, the electromagnetic shielding film and the circuit board provided by the embodiment of the invention have at least one of the following beneficial effects:

when the electromagnetic shielding film is pressed on a circuit board, the shielding layer is formed on one surface of the insulating layer, and the ratio of the roughness Sdr of one surface, close to the shielding layer, of the insulating layer to the rubber gram-weight parameter of the rubber film layer is 0.2-20000 under the condition that the unit of the rubber gram-weight parameter is gram per square decimeter, so that the rubber in the rubber film layer can be effectively accommodated by the surface, far away from the insulating layer, of the shielding layer, and the problem of obvious rubber overflow caused by the fact that a large amount of rubber substances move to the edge of the circuit board is not easy to occur, and the circuit board pressed with the shielding film has good appearance; in addition, the ratio of the roughness Sdr of the surface of the insulating layer close to the shielding layer to the rubber gram weight parameter of the rubber film layer is 0.2-20000, so that the rubber amount of the rubber film layer and the roughness of the surface of the shielding layer can have a proper ratio, the shielding layer is effectively contacted with the ground layer of the circuit board and is connected with the circuit board in a pressing mode, the circuit board has good appearance after the shielding layer is pressed on the circuit board in a pressing mode, meanwhile, the rubber amount of the rubber film layer is not required to be too small, or the pressing force on the shielding film is not required to be reduced intentionally, and the shielding film and the circuit board can have good bonding strength. In summary, the embodiments of the present invention can have the following advantages at the same time: the circuit board has good adhesive strength with the circuit board and good appearance after being pressed on the circuit board.

Drawings

In order to more clearly illustrate the technical solution of the present invention, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without creative efforts.

Fig. 1 is a schematic structural view of a first electromagnetic shielding film according to an embodiment of the present invention;

fig. 2 is a schematic structural view of a second electromagnetic shielding film according to an embodiment of the present invention;

fig. 3 is a schematic structural view of a third electromagnetic shielding film according to an embodiment of the present invention;

fig. 4 is a schematic structural view of a fourth electromagnetic shielding film according to an embodiment of the present invention;

fig. 5 is a schematic structural view of a fifth electromagnetic shielding film according to an embodiment of the present invention;

fig. 6 is a schematic structural diagram of a circuit board according to an embodiment of the present invention.

Reference is made to the accompanying drawings in which: 1. a carrier layer; 2. an insulating layer; 3. a shielding layer; 4. a glue film layer; 5. a protective film layer; 6. a conductive bump; 7. the circuit board body.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

In the description of the specification and claims, it is to be understood that the terms "upper", "lower", "left", "right", "front", "back", "top", "bottom", "inner", "outer", and the like, indicate orientations and positional relationships based on those shown in the drawings, are used for convenience in describing embodiments of the present invention, and do not indicate or imply that the referenced devices or components must have a particular orientation, be constructed and operated in a particular orientation, and thus are not to be construed as limiting the embodiments of the present invention.

Furthermore, the terms first, second and the like in the description and in the claims, are used for descriptive purposes only to distinguish one technical feature from another, and are not to be construed as indicating or implying relative importance or to imply that the indicated technical features are in number, nor necessarily order or temporal order. The terms are interchangeable under appropriate circumstances. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature.

Referring to fig. 1, an embodiment of the present invention provides an electromagnetic shielding film, which includes an insulating layer 2, a shielding layer 3, and an adhesive film layer 4;

the shielding layer 3 is formed on one surface of the insulating layer 2, and the glue film layer 4 is arranged on one surface of the shielding layer 3 far away from the insulating layer 2;

wherein, under the unit of the rubber gram weight parameter being gram per square decimeter, the ratio of the roughness Sdr of the surface of the insulating layer 2 close to the shielding layer 3 and the rubber gram weight parameter of the rubber film layer 4 is 0.2-20000.

When the ratio of the roughness Sdr to the rubber weight parameter is calculated, the percentage value of the roughness Sdr is calculated as it is without converting the percentage value of the roughness Sdr to an actual value. For example, if the roughness Sdr is 1%, the calculation is performed by using the value 1 without conversion to 0.01.

The insulating layer 2 can electrically isolate the shielding layer 3 from the outside effectively, so that the electromagnetic shielding effect of the shielding layer 3 can be ensured. The shielding layer 3 plays a role of electromagnetic shielding. In addition, the electromagnetic shielding film can be attached to the circuit board through the adhesive film layer 4.

It can be understood that, the side of the insulating layer 2 on which the shielding layer 3 is formed has a certain roughness, and when the shielding layer 3 is formed on the side of the insulating layer 2, the shielding layer 3 will undulate along with the rough surface of the insulating layer 2 because the thickness of the shielding layer 3 is constant, so that the side of the shielding layer 3 close to the adhesive film layer 4 can have a certain roughness.

In the embodiment of the invention, when the electromagnetic shielding film is laminated on the circuit board, the shielding layer 3 is formed on one surface of the insulating layer 2, and under the unit of the rubber gram weight parameter being gram per square decimeter, the ratio of the roughness Sdr of the surface of the insulating layer 2 close to the shielding layer 3 to the rubber gram weight parameter of the rubber film layer 4 is 0.2-20000, so that the rubber in the rubber film layer 4 can be effectively accommodated by the surface of the shielding layer 3 far away from the insulating layer 2, the problem of obvious rubber overflow at the edge between the electromagnetic shielding film and the circuit board due to the fact that a large amount of rubber substances move to the edge of the circuit board is not easy to occur, and the circuit board laminated with the shielding film has good appearance; in addition, the ratio of the roughness Sdr of the side of the insulating layer 2 close to the shielding layer 3 to the rubber gram weight parameter of the rubber film layer 4 is 0.2-20000, so that the rubber amount of the rubber film layer 4 and the roughness of the side of the shielding layer 3 can be in a proper ratio, the shielding layer 3 can be effectively contacted with the ground layer of the circuit board and connected with the ground layer of the circuit board in a pressing mode, the circuit board has a good appearance after the shielding layer 3 is pressed on the circuit board in a pressing mode, meanwhile, the rubber amount of the rubber film layer 4 is not required to be too small, or the pressing force on the shielding film is not required to be reduced intentionally, and the shielding film and the circuit board can have good bonding strength. In summary, the embodiments of the present invention can have the following advantages at the same time: the circuit board has good adhesive strength with the circuit board and good appearance after being pressed and combined on the circuit board.

Illustratively, the film layer 4 has a grammage parameter of 0.01-1 grams per square decimeter.

In this embodiment, when the electromagnetic shielding film is pressed onto the circuit board, the glue film layer 4 with a rubber gram weight of 0.01-1 g per square decimeter is easily pierced by the surface of the shielding layer 3 away from the insulating layer 2, so that the shielding layer 3 is electrically connected with the ground layer of the circuit board, and thus the interference charges of the shielding layer 3 can be effectively introduced into the ground layer of the circuit board, and the shielding effectiveness of the electromagnetic shielding layer 3 is effectively improved. In addition, the adhesive film layer 4 with the grammes per square decimeter of 0.01-1 g can effectively maintain the adhesive strength between the electromagnetic shielding film and the circuit board, so that the phenomenon of board explosion between the electromagnetic shielding film and the circuit board is not easy to occur. As an example, the grammes parameter of the adhesive film layer 4 is 0.01, 0.05, 0.1, 0.2, 0.505, 0.7, 1 gram per square decimeter.

Illustratively, the roughness Sdr of the surface of the insulating layer 2 close to the shielding layer 3 is 0.1% -8000%. Preferably, the roughness Sdr of the side of the insulating layer 2 close to the shielding layer 3 is 1% -2000%, and more preferably, the roughness Sdr of the side of the insulating layer 2 close to the shielding layer 3 is 20% -500%.

It is understood that the roughness Sdr represents: how much the extended area (surface area) of a region increases relative to the area of the defined region. Wherein Sdr of a completely flat surface is 0. For example, the roughness Sdr of one side of the insulating layer 2 is 20%, which can indicate that the area of the test region of the shielding film after being spread flat is increased by 20% compared to before spreading. In addition, the test standard for the roughness Sdr is ISO 25178.

In this embodiment, the shielding layer 3 is formed on one surface of the insulating layer 2, and the roughness Sdr of the surface of the insulating layer 2 close to the shielding layer 3 is 0.1% to 8000%, so that in the process of forming the shielding layer 3 on the surface of the insulating layer 2, the shielding layer 3 can undulate along with the surface of the insulating layer 2, and the surface of the shielding layer 3 far from the insulating layer 2 can be easily provided with a roughness capable of piercing the adhesive film layer 4, so that the shielding layer 3 can be effectively electrically connected with the ground layer of the circuit board. As an example, the roughness Sdr of the side of the insulating layer 2 close to the shielding layer 3 is 0.1%, 0.5%, 1%, 5%, 10%, 50%, 100%, 500%, 1000%, 4000.05%, 5000%, 8000%.

In the above embodiment, the ratio of the roughness Sdr of the surface of the shielding layer 3 close to the adhesive film layer 4 to the thickness of the adhesive film layer 4 is 2 to 95.

In this embodiment, the ratio of the roughness Sdr of the surface of the shielding layer 3 close to the glue film layer 4 to the thickness of the glue film layer 4 is 2 to 95, so that when the electromagnetic shielding film is laminated on a circuit board, the surface of the shielding layer 3 close to the glue film layer 4 can effectively pierce through the glue film layer 4 and is electrically connected with the ground layer of the circuit board, and then the interference charges of the shielding layer 3 can be effectively introduced into the ground layer of the circuit board, thereby effectively improving the shielding effectiveness of the electromagnetic shielding layer 3.

Wherein, the materials used for the glue film layer 4 are selected from the following materials: modified epoxy resins, acrylic resins, modified rubbers, and modified thermoplastic polyimides. It is understood that, in order to ensure that the shielding layer 3 has good electrical conductivity, the shielding layer 3 includes one or more of a metal shielding layer, a carbon nanotube shielding layer, a ferrite shielding layer and a graphene shielding layer. Wherein the metal shielding layer comprises a single metal shielding layer and/or an alloy shielding layer; the single metal shielding layer is made of any one of aluminum, titanium, zinc, iron, nickel, chromium, cobalt, copper, silver and gold, and the alloy shielding layer is made of any two or more of aluminum, titanium, zinc, iron, nickel, chromium, cobalt, copper, silver and gold.

In the above embodiment, further, the ratio of the roughness Sdr of the side of the insulating layer 2 close to the shielding layer 3 to the thickness of the shielding layer 3 is 0.1 to 335. In the process of forming the shielding layer 3 on the rough surface of the insulating layer 2, the ratio of the roughness Sdr of the rough surface of the insulating layer 2 to the thickness of the shielding layer 3 is 0.1-335, so that the shielding layer 3 can undulate along with the rough surface of the insulating layer 2, and the surface, far away from the insulating layer 2, of the shielding layer 3 can be easily provided with roughness capable of penetrating through the adhesive film layer 4, so that the shielding layer 3 can be effectively electrically connected with the ground layer of the circuit board.

In the above embodiment, further, referring to fig. 2, the shielding layer 3 is provided with a through hole penetrating through the upper and lower surfaces thereof. Through set up the through-hole that runs through on the shielding layer 3, like this will electromagnetic shielding membrane high temperature pressfitting is when the circuit board is gone up, and the volatile gas of production in the glued membrane layer 4 can effectively pass through the through-hole of shielding layer 3 exhausts to avoid 4 volatile matters in the glued membrane layer to be difficult to discharge when the high temperature, thereby avoided electromagnetic shielding membrane bubbling layering to cause peeling off between the stratum of electromagnetic shielding membrane and circuit board, and then ensured electromagnetic shielding membrane ground connection and will disturb the electric charge and derive.

In this embodiment, the aperture of the through hole is 0.1 to 10 μm. The aperture of the through hole is set to be 0.1-10 microns, so that the through hole can smoothly discharge volatile gas in the high-temperature pressing process of the adhesive film layer 4.

In this embodiment, the number of through holes per square centimeter on the shielding layer 3 is 1-1000 on average. The number of the through holes is set to be 1-1000, so that volatile matters in the adhesive film layer 4 can be exhausted through enough through holes at high temperature, the problem that volatile gases in the adhesive film layer 4 are difficult to exhaust at high temperature is avoided, stripping between the electromagnetic shielding film and a stratum of a circuit board caused by bubbling and layering of the electromagnetic shielding film is avoided, grounding of the electromagnetic shielding film is guaranteed, and interference charges are effectively led out.

In this embodiment, the ratio of the sum of the cross-sectional areas of all the through holes of the shielding layer 3 in each square centimeter on average to the cross-sectional area of the shielding layer where the cross-section is located is 1% to 70%. Through making shielding layer 3 is all in average per square centimeter the cross sectional area sum of through-hole with the cross section place the ratio of the cross sectional area of shielding layer is 1% -70%, like this guarantee that the volatile gas of production in the glued membrane layer 4 can effectively pass through when the through-hole of shielding layer 3 carries out the exhaust, can not influence because of the through-hole quantity is too much the electromagnetic shielding effect of shielding layer 3.

In the above embodiment, further, referring to fig. 3, the electromagnetic shielding film further includes a carrier layer 1; the carrier layer 1 is arranged on the side of the insulating layer 2 remote from the shielding layer 3. The carrier layer 1 may be for protecting the insulating layer 2 so that the insulating layer 2 is not damaged by external contact or impact, etc. Furthermore, the carrier layer 1 may serve as a base film forming the insulating layer 2, namely: an insulating layer 2 can be formed on one side of the carrier layer 1.

Specifically, the insulating layer 2 is formed on one side of the carrier layer 1; the ratio of the roughness Sdr of the one surface of the carrier layer 1 to the thickness of the insulating layer 2 is 0.05-12. In the process of forming the insulating layer 2 on one surface of the carrier layer 1, the ratio of the roughness Sdr of the one surface of the carrier layer 1 to the thickness of the insulating layer 2 is 0.05-12, so that the insulating layer 2 can undulate along with the one surface of the carrier layer 1, and the surface, far away from the carrier layer 1, of the insulating layer 2 can easily have certain roughness, so that the surface, far away from the insulating layer 2, of the shielding layer 3 can finally have the roughness capable of piercing the adhesive film layer 4, and the shielding layer 3 can be effectively electrically connected with the ground layer of the circuit board.

In the above embodiment, further referring to fig. 4, a conductive protrusion 6 is disposed on a surface of the shielding layer 3 close to the adhesive film layer 4, so that the adhesive film layer 4 can be pierced more effectively, thereby further ensuring that the electromagnetic shielding film is electrically connected with the ground layer of the circuit board.

Specifically, the number of the conductive bumps 6 having a longitudinal height of more than 5um on the shielding film provided per square centimeter on the average on the one face of the shielding layer 3 is 1 to 1000. This can more effectively pierce the adhesive film layer 4, thereby further ensuring the electrical connection of the electromagnetic shielding film with the ground layer of the circuit board.

In the embodiment of the present invention, the conductive bumps 6 may be regularly or irregularly distributed on a surface of the shielding layer 3 close to the adhesive film layer 4. In this embodiment, the shapes of the conductive bumps 6 may be the same or different, and the distances between the conductive bumps 6 may be the same or different. Preferably, the shapes of the conductive bumps 6 are the same, and the conductive bumps 6 are uniformly distributed on the surface of the shielding layer 3 of the conductive base body portion, which is close to the adhesive film layer 4. In a specific implementation, the shielding layer 3 may be formed first, and then the conductive bump 6 may be formed on the shielding layer 3 by another process. Of course, the shielding layer 3 and the conductive bump 6 may also be an integral structure formed by a one-step molding process.

Illustratively, the conductive bump 6 includes a conductive base portion and at least one conductive spike portion; the conductive base portion extends outward from the one surface of the shielding layer 3, and at least one of the conductive spikes extends outward from a surface of the conductive base portion. The conductive sharp part extending from the surface of the conductive base part can pierce the adhesive film layer 4 more effectively, so that the shielding layer 3 can be better electrically connected with the ground layer of the circuit board.

Specifically, the protruding height of the conductive spine part is 0.1-8 micrometers, so that the conductive spine part can effectively pierce the adhesive film layer 4, and the electromagnetic shielding film is further ensured to be electrically connected with the ground layer of the circuit board.

Preferably, the conductive bump 6 may have a certain distance with the outer surface of the adhesive film layer 4, and may also contact with the outer surface of the adhesive film layer 4 or extend out of the outer surface of the adhesive film layer 4. In addition, the outer surface of the adhesive film layer 4 may be a flat surface without undulation, or may be an uneven surface with gentle undulation.

It should be noted that the shape of the conductive bump 6 in fig. 4 is merely exemplary, and due to differences in process means and parameters, the conductive bump 6 may also be in other shapes such as cluster, ice, stalactite, and dendritic shapes. In addition, the conductive bump 6 in the embodiment of the present invention is not limited to the shape shown in the drawings and described above, and any conductive bump 6 having piercing and conductive functions is within the scope of the present invention.

As another example, the conductive bump 6 may be composed of one or more conductive particles. The conductive particles include one or more of metal particles, carbon nanotube particles, and ferrite particles. Further, the metal particles include single metal particles and/or alloy particles; the single metal particles are made of any one of aluminum, titanium, zinc, iron, nickel, chromium, cobalt, copper, silver and gold, and the alloy particles are made of any two or more of aluminum, titanium, zinc, iron, nickel, chromium, cobalt, copper, silver and gold. It should be noted that the conductive bump 6 may be the same as or different from the material of the shielding layer 3.

It should be noted that the shielding layer 3 of the present embodiment may have a single-layer structure or a multi-layer structure. When the shielding layer 3 is a single layer, a conductive protrusion may be disposed on one surface of the shielding layer 3 close to the adhesive film layer 4; when the shielding layer 3 is a plurality of layers, a conductive protrusion may be further disposed on one surface of each shielding layer 3 close to the adhesive film layer 4. In addition, the shielding layer 3 of the present embodiment may be provided in a grid shape, a foam shape, etc. according to the requirements of actual production and application.

In the embodiment of the present invention, in order to further ensure the connection between the electromagnetic shielding film and the ground layer of the circuit board, the adhesive layer 4 in this embodiment includes an adhesive layer containing conductive particles. The adhesive layer 4 comprises an adhesive layer containing conductive particles, so that the conductive capability of the adhesive layer 4 is improved, and the ground connection of the electromagnetic shielding film and the circuit board is further ensured. Of course, in the embodiment of the present invention, the adhesive layer 4 may include an adhesive layer without containing conductive particles, so as to reduce the insertion loss of the circuit board with the electromagnetic shielding film, thereby improving the shielding performance and improving the bending resistance of the circuit board.

Referring to fig. 5, the electromagnetic shielding film in this embodiment further includes a protection film layer 5, and the protection film layer 5 is disposed on a surface of the adhesive film layer 4 away from the shielding layer 3. The protective film layer 5 has a protective effect to ensure that the insulating layer 2 is not scratched or damaged in the using process, so that the high shielding effectiveness of the shielding layer 3 is maintained. The protective film layer 5 comprises a PPS film layer, a PEN film layer, a polyester film layer, a polyimide film layer, a film layer formed after epoxy resin ink is cured, a film layer formed after polyurethane ink is cured, a film layer formed after modified acrylic resin is cured or a film layer formed after polyimide resin is cured.

Specifically, when the electromagnetic shielding film includes the carrier layer 1, the insulating layer 2, the shielding layer 3, the adhesive film layer 4, and the protective film layer 5, the method for preparing the electromagnetic shielding film includes:

1) preparing a carrier layer 1;

2) forming an insulating layer 2 on one side of a carrier layer 1;

3) forming a shielding layer 3 on one side of the insulating layer 2 far away from the carrier layer 1;

4) coating glue on one surface of the shielding layer 3 far away from the insulating layer 2 to form a glue film layer 4;

5) and a protective film layer 5 is attached to one surface of the adhesive film layer 4, which is far away from the shielding layer 3.

To facilitate an understanding of the inventive arrangements described above, five specific examples are provided and tested:

the first embodiment is as follows:

an electromagnetic shielding film comprises an insulating layer, a shielding layer and an adhesive film layer; the shielding layer is formed on one surface of the insulating layer, and the adhesive film layer is arranged on one surface, far away from the insulating layer, of the shielding layer; the roughness Sdr of one surface, close to the shielding layer, of the insulating layer is 0.2%, the rubber gram weight parameter of the adhesive film layer is 1 gram per square decimeter, and the ratio of the roughness Sdr of one surface, close to the shielding layer, of the insulating layer to the rubber gram weight parameter of the adhesive film layer is 0.2.

And (3) testing results: after the electromagnetic shielding film of the embodiment is laminated on a circuit board, through tests, the peel strength of the electromagnetic shielding film of the embodiment and the circuit board is greater than 18.92N/cm, and the length of the glue overflow of the adhesive film layer after the electromagnetic shielding film of the embodiment is laminated on the circuit board is less than 198 μm.

Therefore, by applying the electromagnetic shielding film of the embodiment, the electromagnetic shielding film and the circuit board have good adhesive strength, and the circuit board has good appearance.

Example two:

an electromagnetic shielding film comprises an insulating layer, a shielding layer and a film adhesive layer; the shielding layer is formed on one surface of the insulating layer, and the adhesive film layer is arranged on one surface, far away from the insulating layer, of the shielding layer; the roughness Sdr of one surface, close to the shielding layer, of the insulating layer is 0.2%, the rubber gram weight parameter of the adhesive film layer is 0.01 gram per square decimeter, and the ratio of the roughness Sdr of one surface, close to the shielding layer, of the insulating layer to the rubber gram weight parameter of the adhesive film layer is 20.

And (3) testing results: after the electromagnetic shielding film of the embodiment is laminated on a circuit board, through tests, the peel strength of the electromagnetic shielding film of the embodiment and the circuit board is greater than 11.62N/cm, and the length of the glue overflow of the adhesive film layer after the electromagnetic shielding film of the embodiment is laminated on the circuit board is less than 70 μm.

Therefore, by applying the electromagnetic shielding film of the embodiment, the electromagnetic shielding film and the circuit board have good adhesive strength, and the circuit board has good appearance.

Example three:

an electromagnetic shielding film comprises an insulating layer, a shielding layer and a film adhesive layer; the shielding layer is formed on one surface of the insulating layer, and the adhesive film layer is arranged on one surface, far away from the insulating layer, of the shielding layer; the roughness Sdr of the surface of the insulating layer close to the shielding layer is 200%, the glue gram weight parameter of the glue film layer is 1 gram per square decimeter, and the ratio of the roughness Sdr of the surface of the insulating layer close to the shielding layer to the glue gram weight parameter of the glue film layer is 200.

And (3) testing results: after the electromagnetic shielding film of the embodiment is laminated on a circuit board, through tests, the peel strength of the electromagnetic shielding film of the embodiment and the circuit board is greater than 12.76N/cm, and the length of the adhesive overflow of the adhesive film layer after the electromagnetic shielding film of the embodiment is laminated on the circuit board is less than 93 μm.

Therefore, by applying the electromagnetic shielding film of the embodiment, the electromagnetic shielding film and the circuit board have good adhesive strength, and the circuit board has good appearance.

Example four:

an electromagnetic shielding film comprises an insulating layer, a shielding layer and an adhesive film layer; the shielding layer is formed on one surface of the insulating layer, and the adhesive film layer is arranged on one surface, far away from the insulating layer, of the shielding layer; the roughness Sdr of the surface of the insulating layer close to the shielding layer is 200%, the rubber gram weight parameter of the adhesive film layer is 0.01 gram per square decimeter, and the ratio of the roughness Sdr of the surface of the insulating layer close to the shielding layer to the rubber gram weight parameter of the adhesive film layer is 20000.

And (3) testing results: after the electromagnetic shielding film of the embodiment is laminated on the circuit board, through a test, the peel strength of the electromagnetic shielding film of the embodiment and the circuit board is greater than 10.08N/cm, and the length of the glue overflow of the adhesive film layer after the electromagnetic shielding film of the embodiment is laminated on the circuit board is less than 26 μm.

Therefore, by applying the electromagnetic shielding film of the embodiment, the electromagnetic shielding film and the circuit board have good adhesive strength, and the circuit board has good appearance.

Example five:

an electromagnetic shielding film comprises an insulating layer, a shielding layer and an adhesive film layer; the shielding layer is formed on one surface of the insulating layer, and the adhesive film layer is arranged on one surface, far away from the insulating layer, of the shielding layer; the roughness Sdr of the surface of the insulating layer close to the shielding layer is 100.001%, the rubber gram weight parameter of the adhesive film layer is 0.01 gram per square decimeter, and the ratio of the roughness Sdr of the surface of the insulating layer close to the shielding layer to the rubber gram weight parameter of the adhesive film layer is 10000.1.

And (3) testing results: after the electromagnetic shielding film of the embodiment is laminated on a circuit board, through tests, the peel strength of the electromagnetic shielding film of the embodiment and the circuit board is greater than 11.87N/cm, and the length of the glue overflow of the adhesive film layer after the electromagnetic shielding film of the embodiment is laminated on the circuit board is less than 62 μm.

Therefore, by applying the electromagnetic shielding film of the embodiment, the electromagnetic shielding film and the circuit board have good adhesive strength, and the circuit board has good appearance.

The numerical ratio of the roughness Sdr to the rubber grammage parameter is only an example, and the numerical ratio may be other numerical values, such as 1, 10, 100, 1000, 10000, and the like.

Referring to fig. 6, another embodiment of the present invention further provides a circuit board, which includes a circuit board body 7 and the electromagnetic shielding film according to any one of the above embodiments; the electromagnetic shielding film is pressed with the circuit board body 7 through the adhesive film layer 4; one surface of the shielding layer 3 close to the glue film layer 4 pierces through the glue film layer 4 and is electrically connected with the ground layer of the circuit board body 7.

Preferably, the circuit board body 7 is one of a flexible single-sided board, a flexible double-sided board, a flexible multilayer board and a flex-rigid board.

In the embodiment of the invention, one surface of the shielding layer 3 close to the adhesive film layer 4 can pierce through the adhesive film layer 4 and is connected with the ground layer of the circuit board body 7 when the electromagnetic shielding film is pressed with the circuit board body 7, so that the ground connection between the shielding layer 3 and the circuit board body 7 is ensured, interference charges in the shielding layer 3 and the shielding layer 3 are led into the ground, and the interference source formed by accumulation of the interference charges is prevented from influencing the normal operation of the circuit board.

In the embodiment of the invention, the shielding layer 3 is formed on one surface of the insulating layer 2, and the unit of the grammes per square decimeter of the glue weight parameter is gram per square decimeter, so that the glue in the glue film layer 4 can be effectively contained by one surface of the shielding layer 3 far away from the insulating layer 2, the problem of obvious glue overflow at the edge between the electromagnetic shielding film and the circuit board due to the fact that a large amount of glue substances move to the edge of the circuit board is not easy to occur, and the circuit board after the shielding film is pressed has good appearance; in addition, the ratio of the roughness Sdr of the side of the insulating layer 2 close to the shielding layer 3 to the rubber gram weight parameter of the rubber film layer 4 is 0.2-20000, so that the rubber amount of the rubber film layer 4 and the roughness of the side of the shielding layer 3 can be in a proper ratio, the shielding layer 3 can be effectively contacted with the ground layer of the circuit board and connected with the ground layer of the circuit board in a pressing mode, the circuit board has a good appearance after the shielding layer 3 is pressed on the circuit board in a pressing mode, meanwhile, the rubber amount of the rubber film layer 4 is not required to be too small, or the pressing force on the shielding film is not required to be reduced intentionally, and the shielding film and the circuit board can have good bonding strength. In summary, the embodiments of the present invention can have the following advantages at the same time: the circuit board has good adhesive strength with the circuit board and good appearance after being pressed on the circuit board.

The above description is only an embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention disclosed herein are intended to be covered by the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims (10)

1. An electromagnetic shielding film is characterized by comprising an insulating layer, a shielding layer and an adhesive film layer;

the shielding layer is formed on one surface of the insulating layer, and the adhesive film layer is arranged on one surface, far away from the insulating layer, of the shielding layer;

wherein, under the unit of the adhesive gram weight parameter being gram per square decimeter, the ratio of the roughness Sdr of one surface of the insulating layer close to the shielding layer to the adhesive gram weight parameter of the adhesive film layer is 0.2-20000.

2. The electro-magnetic shielding film of claim 1, wherein the shielding layer is provided with a through hole penetrating upper and lower surfaces thereof.

3. The electro-magnetic shielding film of claim 2, wherein the number of through holes per square centimeter on average on the shielding layer is 1 to 1000.

4. The electromagnetic shielding film according to claim 1, wherein the roughness Sdr of the side of the insulating layer close to the shielding layer is 0.1% -8000%.

5. The electromagnetic shielding film of claim 1, wherein the adhesive gram weight parameter of the adhesive film layer is 0.01-1 grams per square decimeter.

6. The electromagnetic shielding film according to claim 1, wherein a ratio of roughness Sdr of a side of the insulating layer adjacent to the shielding layer to a thickness of the shielding layer is 0.1-335.

7. The electro-magnetic shielding film of claim 1, further comprising a carrier layer; the carrier layer is arranged on one surface of the insulating layer, which is far away from the shielding layer.

8. The electro-magnetic shielding film of claim 7, wherein the insulating layer is formed on one side of the carrier layer; the ratio of the roughness Sdr of the one side of the carrier layer to the thickness of the insulating layer is 0.05-12.

9. The electromagnetic shielding film according to claim 1, wherein a conductive bump is disposed on a surface of the shielding layer adjacent to the adhesive film layer.

10. A wiring board comprising a wiring board body and the electromagnetic shielding film according to any one of claims 1 to 9; the electromagnetic shielding film is pressed with the circuit board body through the adhesive film layer; one surface of the shielding layer, which is close to the glue film layer, pierces the glue film layer and is electrically connected with the ground layer of the circuit board body.

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