Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
In the description and claims, it should be understood that the terms "upper," "lower," "left," "right," "front," "rear," "top," "bottom," "inner," "outer," and the like indicate an orientation or positional relationship based on that shown in the drawings, merely to facilitate description of the embodiments of the invention, and do not indicate or imply that the devices or components referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus should not be construed as limiting the embodiments of the invention.
Furthermore, the terms first, second and the like in the description and in the claims, are used for descriptive purposes only and are not necessarily for describing relative importance or to indicate the number of features indicated or to imply a sequence or order. The terms are interchangeable where appropriate. Thus, a feature defining "a first" or "a 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 a shielding layer 3 and a glue film layer 4;
the adhesive film layer 4 is arranged on one surface of the shielding layer 3;
Wherein, under the unit of gram weight parameter is gram per square decimeter, the ratio of the roughness Sdr of the surface of the shielding layer 3 close to the adhesive film layer 4 to the numerical value of the gram weight parameter of the adhesive film layer 4 is 25-4500.
In the case of calculating the ratio of the roughness Sdr to the gram weight parameter, the percentage value of the roughness Sdr is not required to be converted into an actual value, but is calculated directly from the percentage value. For example, if the roughness Sdr is 1%, the calculation is directly performed with the value 1 without conversion to 0.01.
Wherein 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. In addition, when in use, a layer of insulating material can be arranged on one surface of the shielding layer 3, which is far away from the adhesive film layer 4, so as to ensure effective electrical isolation between the shielding layer 3 and the outside.
In the embodiment of the invention, when the electromagnetic shielding film is pressed onto the circuit board, as the surface of the shielding layer 3, which is close to the adhesive film layer 4, has roughness, and under the unit of gram per square decimeter of the adhesive gram weight parameter, the ratio of the roughness Sdr of the surface of the shielding layer 3, which is close to the adhesive film layer 4, to the numerical value of the adhesive gram weight parameter of the adhesive film layer 4 is 25-4500, under the condition of applying a certain pressing force, the shielding layer 3 and the stratum of the circuit board can be effectively contacted and connected, so that the interference charge of the shielding layer 3 can be effectively introduced into the stratum of the circuit board, the shielding efficiency of the electromagnetic shielding film can be effectively improved, and in addition, the adhesive quantity of the adhesive film layer 4 and the roughness of the surface of the shielding layer 3 can be provided with a proper ratio, so that the adhesive quantity of the shielding layer 3 and the stratum of the circuit board can be effectively contacted and connected, and the adhesive film layer 4 can be prevented from being excessively small, and the shielding film and the circuit board can also have good bonding strength. In summary, the embodiment of the invention has the advantages of good shielding effectiveness and good bonding strength with the circuit board.
Illustratively, the glue film layer 4 has a glue gram weight parameter of 0.01-1 gram per square decimeter.
In this embodiment, when the electromagnetic shielding film is pressed onto the circuit board, the adhesive film layer 4 with a glue gram weight of 0.01-1 gram per square decimeter is easy to be effectively pierced by the surface of the shielding layer 3, which is close to the adhesive film layer 4, so that the shielding layer 3 is electrically connected with the stratum of the circuit board, and thus, the interference charge of the shielding layer 3 can be effectively introduced into the stratum of the circuit board, and the shielding efficiency of the electromagnetic shielding layer 3 is effectively improved. In addition, the adhesive film layer 4 with the adhesive gram weight of 0.01-1 gram per square decimeter can effectively maintain the adhesive strength between the electromagnetic shielding film and the circuit board, so that the explosion phenomenon is not easy to occur between the electromagnetic shielding film and the circuit board. As an example, the glue gram weight parameter of the glue 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 side of the shielding layer 3 adjacent to the adhesive film layer 4 is 0.1% -4500%. Preferably, the roughness Sdr of the surface of the shielding layer 3 close to the adhesive film layer 4 may be 0.1% -2000%. More preferably, the roughness Sdr of the surface of the shielding layer 3 near the adhesive film layer 4 is 0.1% -560%. As an example, the roughness Sdr of the surface of the shielding layer 3 close to the adhesive film layer 4 is 0.1%, 0.5%, 1%, 5%, 10%, 50%, 100%, 500%, 1000%, 2000%, 2250.05%, 4500%.
It will be appreciated that roughness Sdr indicates how much the area of expansion (surface area) of a region increases relative to the area of the defined region. Wherein the Sdr of the completely flat surface is 0. For example, the roughness Sdr of one side of the shielding layer 3 is 20%, and it can be expressed that the test area of the shielding film is increased by 20% when it is expanded to be flat, compared with that before the expansion. In addition, the test standard of the roughness Sdr is ISO25178.
In this embodiment, since the roughness Sdr of the surface of the shielding layer 3 near the adhesive film layer 4 is 0.1% -4500%, when the electromagnetic shielding film is pressed onto the circuit board, the surface of the shielding layer 3 near the adhesive film layer 4 can effectively pierce the adhesive film layer 4, so that the shielding layer 3 is electrically connected with the stratum of the circuit board, and thus the interference charge of the shielding layer 3 can be effectively introduced into the stratum of the circuit board, the shielding efficiency of the electromagnetic shielding layer 3 is effectively improved, and when the roughness Sdr of the surface of the shielding layer 3 near the adhesive film layer 4 is 0.1% -4500%, the adhesive containing effect is better, and a significant adhesive overflow problem is not easy to occur at the edge of the circuit board due to the fact that the adhesive substance is largely moved to the edge of the circuit board, so that the circuit board after the shielding film is pressed has a good appearance.
In the above embodiment, the ratio of the roughness Sdr of the surface of the shielding layer 3 near the adhesive film layer 4 to the thickness of the adhesive film layer 4 is 2-95.
In this embodiment, the ratio of the roughness Sdr of the surface of the shielding layer 3 near the adhesive film layer 4 to the thickness of the adhesive film layer 4 is 2-95, so that when the electromagnetic shielding film is pressed onto the circuit board, the surface of the shielding layer 3 near the adhesive film layer 4 can effectively pierce the adhesive film layer 4 to be electrically connected with the stratum of the circuit board, and further, the interference charge of the shielding layer 3 can be effectively introduced into the stratum of the circuit board, thereby effectively improving the shielding efficiency of the electromagnetic shielding layer 3.
Wherein the adhesive film layer 4 is made of modified epoxy resins, acrylic acid, modified rubber and modified thermoplastic polyimide. It will be appreciated that 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 in order to ensure good electrical conductivity of the shielding layer. The metal shielding layer comprises a single metal shielding layer and/or an alloy shielding layer, wherein the single metal shielding layer is made of any one material of aluminum, titanium, zinc, iron, nickel, chromium, cobalt, copper, silver and gold, and the alloy shielding layer is made of any two or more materials of aluminum, titanium, zinc, iron, nickel, chromium, cobalt, copper, silver and gold.
In the above embodiment, further referring to fig. 2, the electromagnetic shielding film further includes an insulating layer 2, and the insulating layer 2 is disposed on a side of the shielding layer 3 away from the adhesive film layer 4. Wherein, the insulating layer 2 can effectively electrically isolate the shielding layer 3 from the outside, thereby ensuring the electromagnetic shielding effect of the shielding layer 3.
Specifically, the shielding layer 3 is formed on one side of the insulating layer 2, and the ratio of the roughness Sdr of the one side of the insulating layer 2 to the thickness of the shielding layer 3 is 0.1-335. 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 a roughness capable of penetrating through the adhesive film layer 4, so that the shielding layer 3 can be effectively electrically connected with the stratum of the circuit board.
In the above embodiment, further referring to fig. 3, the electromagnetic shielding film further comprises a carrier layer 1, wherein the carrier layer 1 is disposed on a side of the insulating layer 2 away 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 collision, etc. In addition, the carrier layer 1 may serve as a base film for forming the insulating layer 2, i.e., the insulating layer 2 may 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, and the ratio of the roughness Sdr of the one side 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 the 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 one surface of the insulating layer 2 away from the carrier layer 1 can be easily provided with a certain roughness, so that the surface of the shielding layer 3, which is close to the adhesive film layer 4, can be finally provided with a roughness capable of penetrating the adhesive film layer 4, and the shielding layer 3 can be effectively electrically connected with the stratum of the circuit board.
In the above embodiment, further, referring to fig. 4, the side of the shielding layer 3 near the adhesive film layer 4 is provided with a conductive bump 6, 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 conductive bumps 6 having a longitudinal height of more than 5um on the shielding film is 1 to 1000 per square centimeter on the average provided on the one side of the shielding layer 3. This allows a more efficient penetration of the glue film layer 4, thereby further ensuring an electrical connection of the electromagnetic shielding film with the ground layer of the circuit board.
In the embodiment of the present invention, the conductive protrusions 6 may be regularly or irregularly distributed on the surface of the shielding layer 3 near the adhesive film layer 4. In this embodiment, the plurality of conductive bumps 6 may be identical in shape or different in shape, and the plurality of conductive bumps 6 may be identical in pitch to each other. Preferably, the conductive protrusions 6 have the same shape, and the conductive protrusions 6 are uniformly distributed on one surface of the shielding layer 3 of the conductive base portion, which is close to the adhesive film layer 4. In an implementation, the shielding layer 3 may be formed first, and then the conductive bump 6 may be formed on the shielding layer 3 through other processes. Of course, the shielding layer 3 and the conductive bump 6 may be an integral structure formed by a one-shot molding process.
The conductive bump 6 illustratively includes a conductive base portion extending from a surface of the shielding layer 3 adjacent to the adhesive film layer 4, and at least one conductive spike portion extending from a surface of the conductive base portion. Wherein the conductive spike extending from the surface of the conductive base portion is capable of more effectively piercing the adhesive film layer 4, thereby enabling the shield layer 3 to be better electrically connected with the ground layer of the circuit board.
Specifically, the height of the protrusion of the conductive spike is 0.1-8 micrometers, so that the conductive spike can effectively pierce the adhesive film layer 4, and the electromagnetic shielding film is further ensured to be electrically connected with the stratum of the circuit board.
Preferably, the conductive protrusion 6 may be spaced from the outer surface of the adhesive film layer 4, or may contact 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 the conductive bump 6 may be in a cluster shape, an ice-hanging shape, a stalactite shape, a dendritic shape, or other shapes due to differences in process means and parameters. In addition, the conductive bump 6 in the embodiment of the present invention is not limited by 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 made of any one of aluminum, titanium, zinc, iron, nickel, chromium, cobalt, copper, silver, and gold, and/or alloy particles made of any two or more of aluminum, titanium, zinc, iron, nickel, chromium, cobalt, copper, silver, and gold. 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 in this 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 a surface of the shielding layer 3 close to the adhesive film layer 4, and when the shielding layer 3 is a plurality of layers, a conductive protrusion may be disposed on a 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 mesh shape, a foam shape, or the like, according to the actual production and application requirements.
In the embodiment of the present invention, in order to further ensure the formation connection between the electromagnetic shielding film and the circuit board, the adhesive film layer 4 in the embodiment includes an adhesive layer containing conductive particles. The adhesive layer 4 comprises an adhesive layer containing conductive particles so as to improve the conductive capability of the adhesive layer 4, thereby further ensuring the stratum connection of the electromagnetic shielding film and the circuit board. Of course, in the embodiment of the present invention, the adhesive film layer 4 may include an adhesive layer without conductive particles, so as to reduce the insertion loss of the circuit board with the electromagnetic shielding film, thereby improving the bending resistance of the circuit board while improving the shielding efficiency.
Referring to fig. 5, the electromagnetic shielding film in this embodiment further includes a protective film layer 5, where the protective film layer 5 is disposed on a surface of the adhesive film layer 4 away from the shielding layer 3. Since the protective film layer 5 has a protective effect, the insulating layer 2 is not scratched and damaged in the use 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 by curing epoxy resin ink, a film layer formed by curing polyurethane ink, a film layer formed by curing modified acrylic resin or a film layer formed by curing polyimide resin.
Specifically, when the electromagnetic shielding film includes a carrier layer 1, an insulating layer 2, a shielding layer 3, a glue film layer 4 and a protective film layer 5, the preparation method of the electromagnetic shielding film includes:
1) Preparing a carrier layer 1;
2) Forming an insulating layer 2 on one side of the carrier layer 1;
3) Forming a shielding layer 3 on a side of the insulating layer 2 remote 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 far away from the shielding layer 3.
To facilitate an understanding of the above inventive arrangements, the following four specific examples are provided herein and tested:
Embodiment one:
The electromagnetic shielding film comprises a shielding layer and a film layer, wherein the film layer is arranged on one surface of the shielding layer, the roughness Sdr of one surface of the shielding layer, which is close to the film layer, is 560%, the glue gram weight parameter of the film layer is 1 gram per square decimeter, and the ratio of the roughness Sdr of one surface of the shielding layer, which is close to the film layer, to the glue gram weight parameter of the film layer is 560.
Test results after the electromagnetic shielding film of the embodiment is pressed onto the circuit board, the grounding resistance between the shielding layer of the electromagnetic shielding film of the embodiment and the stratum of the circuit board is smaller than 187mΩ through test. Moreover, the peel strength of the electromagnetic shielding film and the circuit board of the embodiment is more than 17.39N/cm.
Therefore, by applying the electromagnetic shielding film of the embodiment, the interference charge of the shielding layer can be effectively led into the stratum of the circuit board, so that the electromagnetic shielding film has good shielding efficiency, and after being pressed onto the circuit board, the electromagnetic shielding film and the circuit board have good adhesive strength.
Embodiment two:
The electromagnetic shielding film comprises a shielding layer and a film layer, wherein the film layer is arranged on one surface of the shielding layer, the roughness Sdr of one surface of the shielding layer, which is close to the film layer, is 25%, the glue gram weight parameter of the film layer is 1 gram per square decimeter, and the ratio of the roughness Sdr of one surface of the shielding layer, which is close to the film layer, to the glue gram weight parameter of the film layer is 25.
Test results after the electromagnetic shielding film of the embodiment is pressed onto the circuit board, the grounding resistance between the shielding layer of the electromagnetic shielding film of the embodiment and the stratum of the circuit board is smaller than 436mΩ through test. Moreover, the peel strength of the electromagnetic shielding film and the circuit board of the embodiment is more than 18.23N/cm.
Therefore, by applying the electromagnetic shielding film of the embodiment, the interference charge of the shielding layer can be effectively led into the stratum of the circuit board, so that the electromagnetic shielding film has good shielding efficiency, and after being pressed onto the circuit board, the electromagnetic shielding film and the circuit board have good adhesive strength.
Embodiment III:
The electromagnetic shielding film comprises a shielding layer and a film layer, wherein the film layer is arranged on one surface of the shielding layer, the roughness Sdr of one surface of the shielding layer, which is close to the film layer, is 22.625%, the glue gram weight parameter of the film layer is 0.01 gram per square decimeter, and the ratio of the roughness Sdr of one surface of the shielding layer, which is close to the film layer, to the numerical value of the glue gram weight parameter of the film layer is 2262.5.
And after the electromagnetic shielding film of the embodiment is pressed on the circuit board, the grounding resistance between the shielding layer of the electromagnetic shielding film and the stratum of the circuit board is smaller than 114mΩ after test. Moreover, the peel strength of the electromagnetic shielding film and the circuit board of the embodiment is more than 10.23N/cm.
Therefore, by applying the electromagnetic shielding film of the embodiment, the interference charge of the shielding layer can be effectively led into the stratum of the circuit board, so that the electromagnetic shielding film has good shielding efficiency, and after being pressed onto the circuit board, the electromagnetic shielding film and the circuit board have good adhesive strength.
Embodiment four:
The electromagnetic shielding film comprises a shielding layer and a film layer, wherein the film layer is arranged on one surface of the shielding layer, the roughness Sdr of one surface of the shielding layer, which is close to the film layer, is 4500%, the glue gram weight parameter of the film layer is 1 gram per square decimeter, and the ratio of the roughness Sdr of one surface of the shielding layer, which is close to the film layer, to the glue gram weight parameter of the film layer is 4500.
And after the electromagnetic shielding film of the embodiment is pressed on the circuit board, the grounding resistance between the shielding layer of the electromagnetic shielding film and the stratum of the circuit board is less than 85mΩ after test. Moreover, the good peel strength of the electromagnetic shielding film and the circuit board of the embodiment is more than 17.36N/cm.
Therefore, by applying the electromagnetic shielding film of the embodiment, the interference charge of the shielding layer can be effectively led into the stratum of the circuit board, so that the electromagnetic shielding film has good shielding efficiency, and after being pressed onto the circuit board, the electromagnetic shielding film and the circuit board have good adhesive strength.
The ratio of the roughness Sdr to the grammage parameter is merely exemplary, and the ratio of the values may be other values, such as 40, 100, 1000, 3000, etc.
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 foregoing embodiments, wherein the electromagnetic shielding film is pressed together with the circuit board body 7 through the adhesive film layer 4, and one surface of the shielding layer 3, which is close to the adhesive film layer 4, pierces through the adhesive film layer 4 and is electrically connected with a ground layer of the circuit board body 7.
Preferably, the circuit board body 7 is one of flexible single-sided, flexible double-sided, flexible multi-layer board and rigid-flex board.
In the embodiment of the invention, the surface of the shielding layer 3, which is close to the adhesive film layer 4, can pierce the adhesive film layer 4 and be connected with the stratum of the circuit board body 7 when the electromagnetic shielding film is pressed with the circuit board body 7, so that the stratum connection of the shielding layer 3 and the circuit board body 7 is ensured, and the interference charges in the shielding layer 3 and the shielding layer 3 are led into the ground, thereby avoiding the influence of an interference source on the normal operation of the circuit board due to the accumulation of the interference charges.
In the embodiment of the invention, since the surface of the shielding layer 3 near the adhesive film layer 4 has roughness, and the ratio of the roughness Sdr of the surface of the shielding layer 3 near the adhesive film layer 4 to the numerical value of the adhesive gram weight parameter of the adhesive film layer 4 is 25-4500 under the unit of gram per square centimeter, under the condition that a certain pressing force is applied, the shielding layer 3 and the stratum of the circuit board can be effectively contacted and connected, so that the interference charge of the shielding layer 3 can be effectively introduced into the stratum of the circuit board, the shielding efficiency of the electromagnetic shielding film can be effectively improved, and the adhesive amount of the adhesive film layer 4 and the roughness of the surface of the shielding layer 3 can be provided with a proper ratio, so that the adhesive film 3 and the stratum of the circuit board can be effectively contacted and connected, and the circuit board can have good appearance after being pressed to the circuit board, the adhesive amount of the shielding layer 4 can be not excessively reduced, and the adhesive film and the circuit board can have good bonding strength. In summary, the embodiment of the invention has the advantages of good shielding effectiveness and good bonding strength with the circuit board.
The foregoing is merely illustrative of the present invention, and the present invention is not limited thereto, and any changes or substitutions easily contemplated by those skilled in the art within the technical scope of the present invention should be included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.