CN110784988A - Free grounding film, circuit board and preparation method of free grounding film - Google Patents

Free grounding film, circuit board and preparation method of free grounding film Download PDF

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Publication number
CN110784988A
CN110784988A CN201811424089.9A CN201811424089A CN110784988A CN 110784988 A CN110784988 A CN 110784988A CN 201811424089 A CN201811424089 A CN 201811424089A CN 110784988 A CN110784988 A CN 110784988A
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CN
China
Prior art keywords
layer
film
conductor
conductor layer
free
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Pending
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CN201811424089.9A
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Chinese (zh)
Inventor
苏陟
高强
朱开辉
蒋卫平
朱海萍
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Guangzhou Fangbang Electronics Co Ltd
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Guangzhou Fangbang Electronics Co Ltd
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Priority to CN201811424089.9A priority Critical patent/CN110784988A/en
Publication of CN110784988A publication Critical patent/CN110784988A/en
Pending legal-status Critical Current

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    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K1/00—Printed circuits
    • H05K1/02—Details
    • H05K1/0213—Electrical arrangements not otherwise provided for
    • H05K1/0216—Reduction of cross-talk, noise or electromagnetic interference
    • H05K1/0218—Reduction of cross-talk, noise or electromagnetic interference by printed shielding conductors, ground planes or power plane
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K2201/00—Indexing scheme relating to printed circuits covered by H05K1/00
    • H05K2201/07—Electric details
    • H05K2201/0707—Shielding
    • H05K2201/0715—Shielding provided by an outer layer of PCB

Abstract

The invention relates to the field of electronics, and discloses a free grounding film, a circuit board and a preparation method of the free grounding film, wherein the free grounding film comprises a conductor layer and a glue film layer, the glue film layer is arranged on the conductor layer, one surface of the conductor layer, which is close to the glue film layer, is an uneven surface, and a through hole which penetrates through the upper surface and the lower surface of the conductor layer is arranged on the conductor layer, so that volatile matters in the glue film layer can be exhausted through the through hole of the conductor layer at high temperature, and the problem that the volatile matters in the glue film layer are difficult to exhaust at high temperature is avoided, and therefore, the free grounding film is prevented from being peeled off from an electromagnetic shielding film due to foaming; in addition, when the free grounding film is used for grounding the printed circuit board, the printed circuit board is provided with an electromagnetic shielding film, the electromagnetic shielding film comprises a shielding layer and an insulating layer arranged on the shielding layer, and the non-flat surface of the conductor layer pierces the adhesive film layer and the insulating layer and is electrically connected with the shielding layer, so that interference charges are led out through the free grounding film.

Description

Free grounding film, circuit board and preparation method of free grounding film
Technical Field
The invention relates to the field of electronics, in particular to a free grounding film, a circuit board and a preparation method of the free grounding film.
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 for short). 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, the circuit board is generally provided with an electromagnetic shielding film to reduce electromagnetic interference, while in the process of shielding electromagnetic waves, interference charges generated from the outside are accumulated on a shielding layer of the electromagnetic shielding film to affect signal transmission of the circuit board, and in order to lead out the interference charges, a free grounding film can be provided on the electromagnetic shielding film. The free grounding film commonly used for the existing circuit board generally comprises a conductor layer and a conductive adhesive layer, wherein the conductor layer is in contact conduction with a shielding layer of the electromagnetic shielding film through the conductive adhesive layer, so that interference charges accumulated on the shielding layer of the electromagnetic shielding film are led out. However, in the process of implementing the invention, the inventor finds that at least the following problems exist in the prior art: volatile matters exist in the conductive adhesive layer under the high-temperature condition, but the conductive layer is compact, so the volatile matters are difficult to discharge, the free grounding film is foamed and layered, the peeling between the free grounding film and the electromagnetic shielding film is caused, the electromagnetic shielding film is failed in grounding, and interference charges cannot be led out.
Disclosure of Invention
The invention aims to provide a free grounding film, a circuit board and a preparation method of the free grounding film, which can effectively prevent volatile matters in a conductive adhesive layer in the existing free grounding film from being discharged through a compact conductor layer at high temperature, so that the free grounding film and an electromagnetic shielding film can be prevented from being peeled off due to bubbling and delamination of the free grounding film, and interference charges can be led out.
In order to solve the above technical problems, the present invention provides a free grounding film, which includes a conductor layer and a glue film layer, wherein the glue film layer is disposed on the conductor layer; a through hole penetrating through the upper surface and the lower surface of the conductor layer is formed in the conductor layer, and one surface, close to the adhesive film layer, of the conductor layer is a non-flat surface; when the free grounding film is used for grounding a printed circuit board, an electromagnetic shielding film is arranged on the printed circuit board and comprises a shielding layer and an insulating layer, the insulating layer is arranged on the shielding layer, the free grounding film is pressed with the electromagnetic shielding film through the adhesive film layer, and the conductor layer pierces the adhesive film layer and the insulating layer and is electrically connected with the shielding layer.
Preferably, one surface of the conductor layer, which is close to the adhesive film layer, includes a plurality of protrusions and a plurality of recesses, and the plurality of protrusions and the plurality of recesses are arranged at intervals.
Preferably, the uneven surface of the conductor layer is provided with convex first conductor particles.
Preferably, the height of the first conductor particles is 35 μm to 100 μm.
Preferably, the thickness of the conductor layer is 0.01 μm to 45 μm, and the thickness of the adhesive film layer is 0.1 μm to 80 μm.
Preferably, the adhesive layer comprises an adhesive layer containing conductive particles; or the adhesive film layer comprises an adhesion layer without conductive particles.
Preferably, the free grounding film further comprises an anti-oxidation layer, and the anti-oxidation layer is arranged on one surface of the conductor layer, which is far away from the adhesive film layer.
Preferably, the free grounding film further comprises a peelable protective film layer, and the peelable protective film layer is arranged on the surface, away from the conductor layer, of the adhesive film layer.
Preferably, the area of the through hole is 0.01 μm 2-1mm 2。
Preferably, the number of the through holes in the conductor layer per square centimeter is 5-10 6And (4) respectively.
In order to solve the same technical problem, the invention also provides a circuit board, which comprises the electromagnetic shielding film, the printed circuit board and the free grounding film, wherein the electromagnetic shielding film is arranged on the printed circuit board, the electromagnetic shielding film comprises a shielding layer and an insulating layer, the insulating layer is arranged on the shielding layer, the free grounding film is pressed with the electromagnetic shielding film through the adhesive film layer, and the conductor layer pierces through the adhesive film layer and the insulating layer and is electrically connected with the shielding layer.
As a preferred scheme, the electromagnetic shielding film further comprises an adhesive layer, the adhesive layer is arranged on one surface of the shielding layer far away from the insulating layer, second conductor particles are arranged on one surface of the shielding layer close to the adhesive layer, and the second conductor particles penetrate through the adhesive layer and are electrically connected with the ground layer of the printed circuit board.
The invention provides a free grounding film and a circuit board, wherein the free grounding film comprises a conductor layer and an adhesive film layer, the adhesive film layer is arranged on the conductor layer, one surface of the conductor layer, which is close to the adhesive film layer, is a non-flat surface, and a through hole penetrating through the upper surface and the lower surface of the conductor layer is arranged on the conductor layer, so that volatile matters in the adhesive film layer can be exhausted through the through hole of the conductor layer at high temperature, the problem that the volatile matters in the adhesive film layer are difficult to exhaust at high temperature is avoided, stripping between the free grounding film and an electromagnetic shielding film caused by bubbling and layering of the free grounding film is avoided, and the grounding of the electromagnetic; in addition, when the free grounding film is used for grounding the printed circuit board, the printed circuit board is provided with an electromagnetic shielding film, the electromagnetic shielding film comprises a shielding layer and an insulating layer, the insulating layer is arranged on the shielding layer, and when the free grounding film is pressed with the electromagnetic shielding film, the adhesive film layer and the insulating layer are pierced through by the uneven surface of the conductor layer and are electrically connected with the shielding layer, so that interference charges accumulated on the electromagnetic shielding film are led out, and the phenomenon that the normal work of the printed circuit board is influenced by an interference source formed by the accumulation of the interference charges is avoided; in addition, because the one side that the conductor layer is close to the glued membrane layer is uneven surface, consequently when free ground membrane and electromagnetic shield membrane pressfitting, constitute gluey class material of glued membrane layer and be extruded in this uneven surface's the sunk position to increase the volume of holding to be glued, thereby be difficult to appear the phenomenon that free ground membrane and electromagnetic shield membrane break away from, avoided current electromagnetic shield membrane because hold glue the not enough problem that leads to free ground membrane and electromagnetic shield membrane to break away from of volume, and then guaranteed electromagnetic shield membrane ground connection effectively, thereby will disturb electric charge and derive.
In order to solve the same technical problem, an embodiment of the present invention further provides a method for preparing a free grounding film, including the following steps:
forming a conductor layer; the conductive layer is provided with a through hole penetrating through the upper surface and the lower surface of the conductive layer, and one surface of the conductive layer is a non-flat surface;
forming an adhesive film layer on the non-flat surface of the conductor layer;
when the free grounding film is used for grounding a printed circuit board, an electromagnetic shielding film is arranged on the printed circuit board and comprises a shielding layer and an insulating layer, the insulating layer is arranged on the shielding layer, the free grounding film is pressed with the electromagnetic shielding film through the adhesive film layer, and the conductor layer pierces the adhesive film layer and the insulating layer and is electrically connected with the shielding layer.
Preferably, the forming the conductor layer specifically includes:
forming an oxidation preventing layer on the carrier film;
forming a conductor layer on the oxidation preventing layer; or the like, or, alternatively,
forming a conductor layer on the surface of the strippable layer with the carrier;
forming an anti-oxidation layer on the conductor layer;
peeling the peelable layer of the tape carrier.
Preferably, before forming the adhesive film layer on the non-flat surface of the conductor layer, the method further includes:
convex first conductor particles are formed on the uneven surface of the conductor layer.
Preferably, the forming of the convex first conductor particles on the uneven surface of the conductor layer specifically includes:
the first conductor particles are formed on the non-planar surface of the conductor layer by one or more of physical roughening, electroless plating, physical vapor deposition, chemical vapor deposition, evaporation plating, sputter plating, electroplating, and hybrid plating.
As a preferred scheme, a glue film layer is formed on the non-flat surface of the conductor layer, specifically:
coating a glue film layer on the release film;
pressing and transferring the adhesive film layer to the non-flat surface of the conductor layer; or the like, or, alternatively,
and coating a glue film layer on the non-flat surface of the conductor layer.
As a preferred scheme, after forming the glue film layer on the non-flat surface of the conductor layer, the method further comprises the following steps:
and forming a strippable protective film layer on the adhesive film layer.
The invention provides a preparation method of a free grounding film, which comprises the following steps of firstly, forming a conductor layer; wherein, a through hole penetrating through the upper surface and the lower surface of the conductor layer is formed on the conductor layer, and one surface of the conductor layer is a non-flat surface; then, an adhesive film layer is formed on the uneven surface of the conductor layer, so that the prepared free grounding film comprises the conductor layer and the adhesive film layer, the adhesive film layer is arranged on the conductor layer, one surface, close to the adhesive film layer, of the conductor layer is the uneven surface, and the conductor layer is provided with a through hole penetrating through the upper surface and the lower surface of the conductor layer, so that volatile matters in the adhesive film layer can be exhausted through the through hole of the conductor layer at high temperature, the situation that the volatile matters in the adhesive film layer are difficult to exhaust at high temperature is avoided, the free grounding film is prevented from being peeled off from the electromagnetic shielding film due to foaming and layering of the free grounding film, and the grounding of the electromagnetic; in addition, when the free grounding film is used for grounding the printed circuit board, the printed circuit board is provided with an electromagnetic shielding film, the electromagnetic shielding film comprises a shielding layer and an insulating layer, the insulating layer is arranged on the shielding layer, and when the free grounding film is pressed with the electromagnetic shielding film, the adhesive film layer and the insulating layer are pierced through by the uneven surface of the conductor layer and are electrically connected with the shielding layer, so that interference charges accumulated on the electromagnetic shielding film are led out, and the phenomenon that the normal work of the printed circuit board is influenced by an interference source formed by the accumulation of the interference charges is avoided; in addition, because the one side that the conductor layer is close to the glued membrane layer is uneven surface, consequently when free ground membrane and electromagnetic shield membrane pressfitting, constitute gluey class material of glued membrane layer and be extruded in this uneven surface's the sunk position to increase the volume of holding to be glued, thereby be difficult to appear the phenomenon that free ground membrane and electromagnetic shield membrane break away from, avoided current electromagnetic shield membrane because hold glue the not enough problem that leads to free ground membrane and electromagnetic shield membrane to break away from of volume, and then guaranteed electromagnetic shield membrane ground connection effectively, thereby will disturb electric charge and derive.
Drawings
FIG. 1 is a schematic structural view of a free grounding film in an embodiment of the present invention;
FIG. 2 is a schematic view of another angle configuration of a free-grounding film in an embodiment of the present invention;
FIG. 3 is a schematic structural view of another embodiment of a free-grounding film in an example of the present invention;
FIG. 4 is a schematic structural diagram of a circuit board in an embodiment of the present invention;
FIG. 5 is a schematic structural diagram of another embodiment of a wiring board in an example of the present invention;
FIG. 6 is a schematic flow chart of a method for preparing a free-grounding film in an embodiment of the present invention;
wherein, 1, a conductor layer; 11. a through hole; 12. a convex portion; 13. a recessed portion; 2. a glue film layer; 3. a first conductive particle; 4. an oxidation-resistant layer; 5. an electromagnetic shielding film; 51. an insulating layer; 52. a shielding layer; 53. a glue layer; 6. a printed wiring board; 7. a second conductive particle.
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.
Referring to fig. 1 to 5, a free grounding film according to a preferred embodiment of the present invention includes a conductor layer 1 and a glue film layer 2, where the glue film layer 2 is disposed on the conductor layer 1; a through hole 11 penetrating through the upper surface and the lower surface of the conductor layer 1 is arranged on the conductor layer 1, and one surface of the conductor layer 1 close to the adhesive film layer 2 is a non-flat surface; when the free grounding film is used for grounding the printed circuit board 6, the electromagnetic shielding film 5 is arranged on the printed circuit board 6, the electromagnetic shielding film 5 comprises a shielding layer 52 and an insulating layer 51, the insulating layer 51 is arranged on the shielding layer 52, the free grounding film is pressed with the electromagnetic shielding film 5 through the glue film layer 2, and the conductor layer 1 penetrates through the glue film layer 2 and the insulating layer 51 and is electrically connected with the shielding layer 52.
In the embodiment of the invention, the free grounding film comprises a conductor layer 1 and an adhesive film layer 2, the adhesive film layer 2 is arranged on the conductor layer 1, one surface of the conductor layer 1 close to the adhesive film layer 2 is an uneven surface, and the conductor layer 1 is provided with a through hole 11 penetrating through the upper surface and the lower surface, so that volatile matters in the adhesive film layer 2 can be exhausted through the through hole 11 of the conductor layer 1 at high temperature, the situation that the volatile matters in the adhesive film layer 2 are difficult to exhaust at high temperature is avoided, the situation that the free grounding film is peeled off from the electromagnetic shielding film 5 due to foaming and layering of the free grounding film is avoided, and the electromagnetic shielding film 5 is ensured to be grounded; in addition, when the free grounding film is used for grounding the printed circuit board 6, the electromagnetic shielding film 5 is arranged on the printed circuit board 6, the electromagnetic shielding film 5 comprises a shielding layer 52 and an insulating layer 51, the insulating layer 51 is arranged on the shielding layer 52, and when the free grounding film is pressed with the electromagnetic shielding film 5, the adhesive film layer 2 and the insulating layer 51 are pierced through by the uneven surface of the conductor layer 1 and are electrically connected with the shielding layer 52; when the printed circuit board 6 is applied to electronic equipment, the printed circuit board can be electrically connected with a shell of the electronic equipment through the free grounding film, so that interference charges accumulated on the electromagnetic shielding film 5 can be led out through the free grounding film, the interference charges can be led out through the shell of the electronic equipment, the grounding of the electromagnetic shielding film 5 is further ensured, the interference charges accumulated on the electromagnetic shielding film 5 are led out, and the interference sources formed by the accumulation of the interference charges are prevented from influencing the normal work of the printed circuit board 6; in addition, because the one side that conductor layer 1 is close to glued membrane layer 2 is uneven surface, consequently when free ground membrane and electromagnetic shielding film 5 pressfitting, glue class material that constitutes glued membrane layer 2 is extruded in this uneven surface's the sunk position, with the increase volume of glue holding, thereby be difficult to appear the phenomenon that free ground membrane and electromagnetic shielding film 5 break away from, avoided current electromagnetic shielding film because the volume of glue holding is not enough leads to free ground membrane and the problem that the electromagnetic shielding film breaks away from, and then guaranteed electromagnetic shielding film ground connection effectively, thereby will disturb the electric charge and derive.
In the embodiment of the present invention, the uneven surface of the conductor layer 1 is a regular uneven surface or an irregular uneven surface. Specifically, when the uneven surface of the conductor layer 1 is a regular uneven surface, the uneven surface is a structure in which the undulations vary periodically, and the amplitude of the undulations and the intervals of the undulations on the uneven surface are the same; when the uneven surface of the conductor layer 1 is an irregular uneven surface, the uneven surface is a structure in which undulations do not periodically change, and the amplitudes of the undulations and/or the intervals of the undulations on the uneven surface are different.
Referring to fig. 1 and fig. 3 to fig. 5, in order to make the conductive layer 1 pierce the adhesive film layer 2 and the shielding layer 52 of the electromagnetic shielding film 5 more easily during the lamination process, one surface of the conductive layer 1 close to the adhesive film layer 2 in the embodiment includes a plurality of convex portions 12 and a plurality of concave portions 13, and the plurality of convex portions 12 and the plurality of concave portions 13 are disposed at intervals. The plurality of convex parts 12 and the plurality of concave parts 13 are arranged on one surface of the conductor layer 1 close to the adhesive film layer 2, and the plurality of convex parts 12 and the plurality of concave parts 13 are arranged at intervals, so that the conductor layer 1 can pierce the adhesive film layer 2 and the shielding layer 52 of the electromagnetic shielding film 5 more easily in the pressing process, and the conductor layer 1 and the shielding layer 52 of the electromagnetic shielding film 5 can be ensured to be in contact; in addition, when the free grounding film is pressed with the electromagnetic shielding film 5, the glue substances forming the glue film layer 2 are extruded into the concave part 13 to increase the glue containing amount, so that the phenomenon that the free grounding film is separated from the electromagnetic shielding film 5 is not easy to occur, the problem that the free grounding film is separated from the electromagnetic shielding film due to insufficient glue containing amount of the existing electromagnetic shielding film is avoided, the grounding of the electromagnetic shielding film 5 is effectively ensured, and the interference charges are led out; in addition, the plurality of protrusions 12 may have a certain distance from the outer surface of the adhesive film layer 2, and may also contact the outer surface of the adhesive film layer 2 or extend out of the outer surface of the adhesive film layer 2.
In the embodiment of the present invention, in order to further ensure the reliability of the grounding and improve the conductive efficiency, the distance between each of the convex portions 12 and the adjacent concave portions 13 is the same. By setting the distance between each convex portion 12 and the adjacent concave portion 13 to be the same, the convex portions 12 can uniformly pierce the adhesive film layer 2, thereby further ensuring that the conductor layer 1 is in contact with the shielding layer 52 of the electromagnetic shielding film 5, and improving the conductive efficiency. Preferably, each of the projections 12 is identical in shape; each of the recesses 13 has the same shape; wherein each convex part 12 is in an axisymmetric structure; each of the concave portions 13 is of an axisymmetric structure; of course, each of the protrusions 12 may also have a non-axisymmetric structure, and each of the recesses 13 may also have a non-axisymmetric structure. Because every convex part 12 is the same with adjacent interval between the depressed part 13, and every the shape of convex part 12 is all the same, every the shape of depressed part 13 is all the same, so that the volume of glue that holds on conductor layer 1 surface is more even, thereby further avoided current electromagnetic shielding film because the volume of glue that holds is not enough leads to the problem that free grounding membrane and electromagnetic shielding film break away from, and then guaranteed electromagnetic shielding film 5 ground connection effectively, thereby derive the interference electric charge.
As shown in fig. 3 and 5, in order to further ensure that the conductor layer 1 is in contact with the shielding layer 52 of the electromagnetic shielding film 5, the uneven surface of the conductor layer 1 in this embodiment is provided with convex first conductor particles 3. The conductor layer 1 is further ensured to be in contact with the shielding layer 52 of the electromagnetic shielding film 5 by providing the first conductor particles 3 having a convex shape on the uneven surface of the conductor layer 1 so as to pierce the adhesive film layer 2. Preferably, the first conductive particles 3 are intensively distributed on the convex portion 12, so that the conductive layer 1 can more easily pierce the adhesive film layer 2 and the shielding layer 52 of the electromagnetic shielding film 5 in the pressing process, thereby achieving grounding and improving the quality of electromagnetic shielding.
In a specific implementation, the conductive layer 1 provided with the first conductive particles 3 may be formed first, and then the first conductive particles 3 may be formed on the conductive layer 1 through another process. Of course, the conductor layer 1 and the first conductor particles 3 may also be a unitary structure formed by a one-shot molding process.
Preferably, the height of the first conductor particles 3 is 35 μm to 100 μm, the thickness of the adhesive film layer 22 is preferably 0.1 μm to 80 μm, and the thickness of the insulating layer 51 is preferably 1 μm to 20 μm. By providing the height of the first conductor particles 3 preferably in the range of 35 μm to 100 μm and the thickness of the glue film layer 22 preferably in the range of 0.1 μm to 80 μm, it is ensured that the first conductor particles 3 can penetrate through the glue film layer 22 and the insulating layer 51 of the electromagnetic shielding film 5, thereby ensuring that the free-grounding film can conduct away the interfering charges accumulated on the electromagnetic shielding film 5. Further, the thickness of the conductor layer 1 is preferably 0.01 μm to 45 μm to ensure that the conductor layer 1 is not easily broken and has good flexibility.
The first conductor particles 3 may have a certain distance from the outer surface of the adhesive film layer 2, and may also contact the outer surface of the adhesive film layer 2 or extend out of the outer surface of the adhesive film layer 2. In addition, the outer surface of the adhesive film layer 2 may be a flat surface without undulation, or may be an uneven surface with gentle undulation. In addition, the surface of the conductor layer 1 away from the adhesive film layer 2 may be a surface of any shape, for example, a flat surface, an uneven surface with a wavy shape, or other rough surface. The drawings of the present invention only illustrate that the side of the conductor layer 1 away from the adhesive film layer 2 is a flat surface, but any other shape is within the scope of the present invention.
In the embodiment of the present invention, the first conductor particles 3 may include a plurality of first conductor particles 3, and the plurality of first conductor particles 3 may be regularly or irregularly distributed on a surface of the conductor layer 1 close to the adhesive film layer 2; the plurality of first conductor particles 3 are regularly distributed on one surface of the conductor layer 1 close to the adhesive film layer 2, that is, the plurality of first conductor particles 3 are the same in shape and are uniformly distributed on one surface of the conductor layer 1 close to the adhesive film layer 2; the plurality of first conductor particles 3 irregularly distributed on the surface of the conductor layer 1 close to the adhesive film layer 2 means that the plurality of first conductor particles 3 are irregularly distributed on the surface of the conductor layer 1 close to the adhesive film layer 2. Preferably, the shapes of the first conductor particles 3 are the same, and the first conductor particles 3 are uniformly distributed on one surface of the conductor layer 1 close to the adhesive film layer 2.
It should be noted that the shapes of the first conductive particles 3 in fig. 3 and 5 are merely exemplary, and the first conductive particles 3 may also be in other shapes such as clusters, ice-hanging shapes, stalactites, and dendrites due to differences in process means and parameters. In addition, the first conductive particles 3 in the embodiment of the present invention are not limited to the shapes shown in the drawings and described above, and any first conductive particles 3 having piercing and conductive functions are within the scope of the present invention.
Preferably, the material used for the glue film layer 2 is 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 conductor layer 1 has good conductivity, the conductor layer 1 includes one or more of a metal conductor layer, a carbon nanotube conductor layer, a ferrite conductor layer, and a graphene conductor layer. Wherein the metal conductor layer comprises a single metal conductor layer and/or an alloy conductor layer; the single metal conductor layer is made of any one of aluminum, titanium, zinc, iron, nickel, chromium, cobalt, copper, silver and gold, and the alloy conductor layer is made of any two or more of aluminum, titanium, zinc, iron, nickel, chromium, cobalt, copper, silver and gold.
The conductor layer 1 of the present embodiment may have a single-layer structure or a multi-layer structure; when the conductive layer 1 is a plurality of layers, the surface of the conductive layer 1 close to the adhesive film layer 2 may be provided with convex first conductive particles 3 or not provided with convex first conductive particles 3. The adhesive film layer 2 can be of a single-layer structure or a multi-layer structure; the conductor layer 1 and the adhesive film layer 2 may be provided in plurality. Preferably, when the conductor layer 1 and the adhesive film layer 2 are respectively a plurality of, the conductor layer 1 and the adhesive film layer 2 are sequentially arranged at intervals, for example, when the conductor layer 1 and the adhesive film layer 2 are respectively 2, the arrangement sequence may be: one of the conductor layers 1, one of the adhesive film layers 2, the other of the conductor layers 1, and the other of the adhesive film layers 2, and so on, which will not be described herein again; in addition, according to the actual production and application requirements, the conductor layer 1 of the present embodiment may be configured as a foamed shape, and the like, which is not described herein further.
Preferably, the waviness of one surface of the conductor layer 1 close to the adhesive film layer 2 (i.e. the distance between the highest point and the lowest point of one surface of the conductor layer 1 close to the adhesive film layer 2) is 0.1 μm to 30 μm, and the waviness of one surface of the conductor layer 1 close to the adhesive film layer 2 is set within the above range, so that the piercing function of the conductor layer 1 can be enhanced, thereby ensuring that the interference charges in the conductor layer 1 are smoothly led out, and further avoiding the accumulation of the interference charges to form an interference source.
Preferably, the thickness of the glue film layer 2 and the sum of the undulation degree of the conductor layer 1 close to one side of the glue film layer 2 and the height of the first conductor particles 3 satisfy a proportional relationship of 0.5-2, so as to ensure sufficient piercing strength and glue holding capacity, which is specifically embodied as follows: on one hand, the phenomenon that the fluctuation degree of the thickness of the adhesive film layer 2 relative to the surface, close to the adhesive film layer 2, of the conductor layer 1 and the sum of the heights of the first conductor particles 3 are too small to cause insufficient glue capacity to cause plate explosion is prevented, and on the other hand, the fluctuation degree of the surface, close to the adhesive film layer 2, of the conductor layer 1 and the sum of the heights of the first conductor particles 3 are too small to cause insufficient piercing strength to cause grounding failure is prevented.
In the present embodiment, the first conductor particles 3 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. The first conductor particles 3 may be made of the same material as the conductor layer 1, or may be made of a different material.
In the embodiment of the present invention, in order to further ensure that the free grounding film is electrically connected to the shielding layer 52 of the electromagnetic shielding film 5, the adhesive layer 2 in the embodiment includes an adhesive layer containing conductive particles. The adhesive layer 2 comprises an adhesive layer containing conductive particles to improve the conductivity of the adhesive layer 2, thereby further ensuring that the free grounding film is electrically connected with the shielding layer 52 of the electromagnetic shielding film 5. Of course, the adhesive layer 2 may include an adhesive layer without conductive particles to reduce the eddy current loss of the circuit board with the free grounding film, thereby ensuring the integrity of transmission and improving the flexibility of the circuit board while improving the shielding performance.
The conductive particles may be conductive particles separated from each other, or may be large-particle conductive particles formed by aggregation; when the conductive particles are mutually separated conductive particles, the grounding conductivity of the adhesive film layer 2 can be further improved; and when the conductive particles are agglomerated large conductive particles, the piercing strength can be increased.
In the embodiment of the present invention, the free grounding film further includes an anti-oxidation layer 4, and the anti-oxidation layer 4 is disposed on a surface of the conductor layer 1 away from the glue film layer 2. The thickness range, material and forming mode of the oxidation preventing layer 4 can be any one of the following conditions:
①, the thickness of the oxidation preventing layer 4 is 0.01-5 μm, preferably 0.1-1 μm, the oxidation preventing layer 4 is made of any one of metal material, ferrite, graphite, carbon nano tube, graphene and silver paste, the metal material is any one of aluminum, titanium, zinc, iron, nickel, chromium, cobalt, copper, silver, gold and molybdenum, or the metal material is an alloy made of any two or more of aluminum, titanium, zinc, iron, nickel, chromium, cobalt, copper, silver, gold and molybdenum, the oxidation preventing layer 4 can be formed by one or more composite processes of chemical plating, PVD, CVD, evaporation plating, sputtering plating and electroplating;
② the thickness of the oxidation-proof layer 4 is 0.1-5 μm, the oxidation-proof layer 4 is made of a mixture of glue and conductive particles, and the volume ratio of the conductive particles to the glue is 5-80%, the oxidation-proof layer 4 can be formed by coating and then curing.
In the embodiment of the present invention, the oxidation-preventing layer 4 and the glue film layer 2 can be tightly contacted through the through hole 11 after being pressed or printed, so that the peeling strength between the oxidation-preventing layer 4 and the conductor layer 1 can be effectively improved, that is, the oxidation-preventing layer 4 and the conductor layer 1 are not easily peeled.
In the embodiment of the present invention, in order to protect the free grounding film, the free grounding film in the embodiment further includes a peelable protective film layer, and the peelable protective film layer is disposed on a surface of the adhesive film layer 2 away from the conductor layer 1. The strippable protective film layer is arranged on the side, away from the conductor layer 1, of the adhesive film layer 2 to protect the free grounding film, and can be stripped in use.
In the embodiment of the present invention, the area of the through hole 11 is preferably 0.01 μm 2-1mm 2. By making the area of the through-hole 11 preferably 0.01 μm 2-1mm 2And the volatile matters in the adhesive film layer 2 can be exhausted through the through holes 11 which are large enough at high temperature, so that the problem that the volatile matters in the adhesive film layer 2 are difficult to exhaust at high temperature is avoided, and the free grounding film is prevented from being peeled off from the electromagnetic shielding film 5 due to foaming and layering of the free grounding film, so that the electromagnetic shielding film 5 is grounded and interference charges are led out. Further, if the number of the through holes 11 is too large, it is liable that the conductor layer 1 is discontinuous or even broken to affect the flow of the disturbance charges, and therefore, it is preferable that the number of the through holes 11 per square centimeter of the conductor layer 1 is 5 to 10 6And (4) respectively. The number of the through holes 11 passing through the conductor layer 1 per square centimeter is set to 5 to 10 6And the volatile matters can be exhausted through enough through holes 11 at high temperature of the adhesive film layer 2, so that the problem that the volatile matters in the adhesive film layer 2 are difficult to exhaust at high temperature is avoided, peeling between the free grounding film and the electromagnetic shielding film 5 caused by bubbling and layering of the free grounding film is avoided, grounding of the electromagnetic shielding film 5 is ensured, interference charges are led out, and meanwhile, the continuous flowing of the interference charges in the conductor layer 1 cannot be influenced by the number of the through holes 11. Of course, the area and the number of the through holes 11 are not limited to the above preferred range, and it is only necessary that the volatile matter generated by the adhesive film layer 2 at a high temperature can be exhausted through the through holes 11, and the number of the through holes 11 does not affect the continuous flow and the conduction of the interference charges in the conductor layer 1, and further does not cause the conductor layer 1 to break, which is not described herein in further detail.
In the embodiment of the present invention, the through holes 11 may be regularly or irregularly distributed on the conductor layer 1; wherein, the through holes 11 are regularly distributed on the conductor layer 1, which means that the through holes 11 have the same shape and are uniformly distributed on the conductor layer 1; the through holes 11 are irregularly distributed on the conductor layer 1, which means that the through holes 11 are irregularly and randomly distributed on the conductor layer 1. Preferably, the through holes 11 have the same shape, and the through holes 11 are uniformly distributed on the conductor layer 1. In addition, the through hole 11 may be a circular through hole 11, and may also be a through hole 11 with any other shape, and the drawings of the present invention only illustrate that the through hole 11 is a circular through hole 11, but the through hole 11 with any other shape is within the protection scope of the present invention.
Referring to fig. 4, in order to solve the same technical problem, an embodiment of the present invention further provides a circuit board, including the electromagnetic shielding film 5, the printed circuit board 6, and the free grounding film, where the electromagnetic shielding film 5 is disposed on the printed circuit board 6, the electromagnetic shielding film 5 includes a shielding layer 52 and an insulating layer 51, the insulating layer 51 is disposed on the shielding layer 52, the free grounding film is laminated with the electromagnetic shielding film 5 through the glue film layer 2, and the conductor layer 1 pierces through the glue film layer 2 and the insulating layer 51 and is electrically connected to the shielding layer 52.
In the embodiment of the present invention, the free grounding film is pressed to the electromagnetic shielding film 5 through the glue film layer 2, and the uneven surface of the conductor layer 1 pierces through the glue film layer 2 and the insulating layer 51 and is electrically connected to the shielding layer 52; when the circuit board is applied to electronic equipment, the free grounding film can be electrically connected with the shell of the electronic equipment, so that interference charges of the electromagnetic shielding film 5 can be led out through the free grounding film, the interference charges can be led out through the shell of the electronic equipment, the interference charges in the shielding layer 52 of the electromagnetic shielding film 5 are led into the ground, and the interference charges are prevented from accumulating to form an interference source to influence the normal operation of the circuit board.
Preferably, the printed circuit board 6 is one of a flexible single-sided board, a flexible double-sided board, a flexible multilayer board, and a rigid-flex printed board.
Referring to fig. 4, in the embodiment of the present invention, in order to implement that the electromagnetic shielding film 5 is disposed on the printed circuit board 6, the electromagnetic shielding film 5 in the embodiment may further include a glue layer 53, where the glue layer 53 is disposed on a side of the shielding layer 52 away from the insulating layer 51. Preferably, the adhesive layer 53 is a conductive adhesive layer, and the adhesive layer 53 is electrically connected to the ground layer of the printed wiring board 6. By electrically connecting the adhesive layer 53 to the ground layer of the printed wiring board 6, it is ensured that the shielding layer 52 is connected to the ground layer of the printed wiring board 6, and it is further ensured that the electromagnetic shielding film 5 is grounded and the interference charges are conducted out.
Referring to fig. 5, in order to realize the electrical connection between the shielding layer 52 and the ground layer of the printed circuit board 6, in this embodiment, second conductive particles 7 are disposed on a surface of the shielding layer 52 close to the adhesive layer 53, and the second conductive particles 7 penetrate through the adhesive layer 53 and are electrically connected to the ground layer of the printed circuit board 6. The second conductive particles 7 are arranged on one side of the shielding layer 52 close to the adhesive layer 53, so that when the electromagnetic shielding film 5 and the printed circuit board 6 are pressed together, the second conductive particles 7 can pierce the adhesive layer 53, thereby further achieving grounding of the shielding layer 52, wherein the second conductive particles 7 may be the same as or different from the first conductive particles 3; in addition, one surface of the shielding layer 52 close to the adhesive layer 53 may be a flat surface or a non-flat surface, and preferably, one surface of the shielding layer 52 close to the adhesive layer 53 is a non-flat surface, so that the shielding layer 52 can pierce through the adhesive layer 53, thereby achieving grounding of the shielding layer 52, and it is only necessary that the shielding layer 52 can be electrically connected with the ground layer of the printed circuit board, which is not described herein in further detail.
Referring to fig. 6, to solve the same technical problem, an embodiment of the present invention further provides a method for manufacturing a free grounding film, including the following steps:
s11, forming a conductor layer 1; a through hole 11 penetrating through the upper surface and the lower surface of the conductor layer 1 is formed on the conductor layer 1, and one surface of the conductor layer 1 is a non-flat surface;
s12, forming a glue film layer 2 on the uneven surface of the conductor layer 1;
when the free grounding film is used for grounding the printed circuit board 6, the electromagnetic shielding film 5 is arranged on the printed circuit board 6, the electromagnetic shielding film 5 comprises a shielding layer 52 and an insulating layer 51, the insulating layer 51 is arranged on the shielding layer 52, the free grounding film is pressed with the electromagnetic shielding film 5 through the glue film layer 2, and the conductor layer 1 penetrates through the glue film layer 2 and the insulating layer 51 and is electrically connected with the shielding layer 52.
In the embodiment of the present invention, the area of the through hole 11 is preferably 0.01 μm 2-1mm 2. By making the area of the through-hole 11 preferably 0.01 μm 2-1mm 2And the volatile matters in the adhesive film layer 2 can be exhausted through the through holes 11 which are large enough at high temperature, so that the problem that the volatile matters in the adhesive film layer 2 are difficult to exhaust at high temperature is avoided, and the free grounding film is prevented from being peeled off from the electromagnetic shielding film 5 due to foaming and layering of the free grounding film, so that the electromagnetic shielding film 5 is grounded and interference charges are led out. Further, if the number of the through holes 11 is too large, it is liable that the conductor layer 1 is discontinuous or even broken to affect the flow of the disturbance charges, and therefore, it is preferable that the number of the through holes 11 per square centimeter of the conductor layer 1 is 5 to 10 6And (4) respectively. The number of the through holes 11 passing through the conductor layer 1 per square centimeter is set to 5 to 10 6And the volatile matters can be exhausted through enough through holes 11 at high temperature of the adhesive film layer 2, so that the problem that the volatile matters in the adhesive film layer 2 are difficult to exhaust at high temperature is avoided, peeling between the free grounding film and the electromagnetic shielding film 5 caused by bubbling and layering of the free grounding film is avoided, grounding of the electromagnetic shielding film 5 is ensured, interference charges are led out, and meanwhile, the continuous flowing of the interference charges in the conductor layer 1 cannot be influenced by the number of the through holes 11. Of course, the area and the number of the through holes 11 are not limited to the above preferred range, and it is only necessary that the volatile matter generated by the adhesive film layer 2 at a high temperature can be exhausted through the through holes 11, and the number of the through holes 11 does not affect the continuous flow and the conduction of the interference charges in the conductor layer 1, and further does not cause the conductor layer 1 to break, which is not described herein in further detail.
In the embodiment of the present invention, the through holes 11 may be regularly or irregularly distributed on the conductor layer 1; wherein, the through holes 11 are regularly distributed on the conductor layer 1, which means that the through holes 11 have the same shape and are uniformly distributed on the conductor layer 1; the through holes 11 are irregularly distributed on the conductor layer 1, which means that the through holes 11 are irregularly and randomly distributed on the conductor layer 1. Preferably, the through holes 11 have the same shape, and the through holes 11 are uniformly distributed on the conductor layer 1. In addition, the through hole 11 may be a circular through hole 11, and may also be a through hole 11 with any other shape, and the drawings of the present invention only illustrate that the through hole 11 is a circular through hole 11, but the through hole 11 with any other shape is within the protection scope of the present invention.
Referring to fig. 1, 3 and 4, in order to make the conductive layer 1 penetrate the adhesive film layer 2 and the shielding layer 52 of the electromagnetic shielding film 5 more easily during the lamination process, one surface of the conductive layer 1 close to the adhesive film layer 2 in the embodiment includes a plurality of convex portions 12 and a plurality of concave portions 13, and the plurality of convex portions 12 and the plurality of concave portions 13 are disposed at intervals. The plurality of convex parts 12 and the plurality of concave parts 13 are arranged on one surface of the conductor layer 1 close to the adhesive film layer 2, and the plurality of convex parts 12 and the plurality of concave parts 13 are arranged at intervals, so that the conductor layer 1 can pierce the adhesive film layer 2 and the shielding layer 52 of the electromagnetic shielding film 5 more easily in the pressing process, and the conductor layer 1 and the shielding layer 52 of the electromagnetic shielding film 5 can be ensured to be in contact; in addition, when the free grounding film is pressed with the electromagnetic shielding film 5, the glue substances forming the glue film layer 2 are extruded into the concave part 13 to increase the glue containing amount, so that the phenomenon that the free grounding film is separated from the electromagnetic shielding film 5 is not easy to occur, the problem that the free grounding film is separated from the electromagnetic shielding film due to insufficient glue containing amount of the existing electromagnetic shielding film is avoided, the grounding of the electromagnetic shielding film 5 is effectively ensured, and the interference charges are led out; in addition, the plurality of protrusions 12 may have a certain distance from the outer surface of the adhesive film layer 2, and may also contact the outer surface of the adhesive film layer 2 or extend out of the outer surface of the adhesive film layer 2.
In the embodiment of the present invention, in order to further ensure the reliability of the grounding and improve the conductive efficiency, the distance between each of the convex portions 12 and the adjacent concave portions 13 is the same. By setting the distance between each convex portion 12 and the adjacent concave portion 13 to be the same, the convex portions 12 can uniformly pierce the adhesive film layer 2, thereby further ensuring that the conductor layer 1 is in contact with the shielding layer 52 of the electromagnetic shielding film 5, and improving the conductive efficiency. Preferably, each of the projections 12 is identical in shape; each of the recesses 13 has the same shape; wherein each convex part 12 is in an axisymmetric structure; each of the concave portions 13 is of an axisymmetric structure; of course, each of the protrusions 12 may also have a non-axisymmetric structure, and each of the recesses 13 may also have a non-axisymmetric structure. Because every convex part 12 is the same with adjacent interval between the depressed part 13, and every the shape of convex part 12 is all the same, every the shape of depressed part 13 is all the same, so that the volume of glue that holds on conductor layer 1 surface is more even, thereby further avoided current electromagnetic shielding film because the volume of glue that holds is not enough leads to the problem that free grounding membrane and electromagnetic shielding film break away from, and then guaranteed electromagnetic shielding film 5 ground connection effectively, thereby derive the interference electric charge.
In this embodiment of the present invention, the step S11 specifically includes:
s21, forming an oxidation preventing layer 4 on the carrier film;
s22, forming a conductor layer 1 on the oxidation preventing layer 4; wherein, one surface of the conductor layer 1 far away from the oxidation-proof layer 4 is a non-flat surface; forming a conductor layer 1 on the oxidation preventing layer 4 by one or more processes of physical roughening, chemical plating, physical vapor deposition, chemical vapor deposition, evaporation plating, sputtering plating, electroplating, and hybrid plating; or the like, or, alternatively,
s31, forming a conductor layer 1 on the surface of the strippable layer with the carrier; wherein, one side of the conductor layer 1 close to the peelable layer of the tape carrier is a non-flat surface; the conductor layer 1 may be formed on the surface of the peelable layer with a carrier by one or more processes of physical roughening, electroless plating, physical vapor deposition, chemical vapor deposition, evaporation plating, sputter plating, electroplating, and hybrid plating;
s32, forming an oxidation preventing layer 4 on the conductor layer 1;
s33, peeling the peelable layer of the tape carrier.
Specifically, the thickness range, material and formation mode of the oxidation preventing layer 4 may be any one of the following cases:
①, the thickness of the oxidation preventing layer 4 is 0.01-5 μm, preferably 0.1-1 μm, the oxidation preventing layer 4 is made of any one of metal material, ferrite, graphite, carbon nano tube, graphene and silver paste, the metal material is any one of aluminum, titanium, zinc, iron, nickel, chromium, cobalt, copper, silver, gold and molybdenum, or the metal material is an alloy made of any two or more of aluminum, titanium, zinc, iron, nickel, chromium, cobalt, copper, silver, gold and molybdenum, the oxidation preventing layer 4 can be formed by one or more composite processes of chemical plating, PVD, CVD, evaporation plating, sputtering plating and electroplating;
② the thickness of the oxidation-proof layer 4 is 0.1-5 μm, the oxidation-proof layer 4 is made of a mixture of glue and conductive particles, and the volume ratio of the conductive particles to the glue is 5-80%, the oxidation-proof layer 4 can be formed by coating and then curing.
In the embodiment of the present invention, the oxidation-preventing layer 4 and the glue film layer 2 can be tightly contacted through the through hole 11 after being pressed or printed, so that the peeling strength between the oxidation-preventing layer 4 and the conductor layer 1 can be effectively improved, that is, the oxidation-preventing layer 4 and the conductor layer 1 are not easily peeled.
Before the step S12, the method further includes: convex first conductor particles 3 are formed on the uneven surface of the conductor layer 1. Specifically, the first conductor particles 3 may be formed on the non-flat surface of the conductor layer 1 by one or more processes of physical roughening, electroless plating, physical vapor deposition, chemical vapor deposition, evaporation plating, sputtering plating, electroplating, and hybrid plating.
Preferably, the step S12 is specifically:
s41, coating the adhesive film layer 2 on the release film;
s42, pressing and transferring the adhesive film layer 2 to the non-flat surface of the conductor layer 1; or the like, or, alternatively,
s51, coating a glue film layer 2 on the uneven surface of the conductor layer 1.
After the step S12, the method may further include: a peelable protective film layer is formed on the adhesive film layer 2.
To sum up, the embodiment of the invention provides a free grounding film, a circuit board and a preparation method of the free grounding film, wherein the free grounding film comprises a conductor layer 1 and an adhesive film layer 2, the adhesive film layer 2 is arranged on the conductor layer 1, one surface of the conductor layer 1, which is close to the adhesive film layer 2, is a non-flat surface, and a through hole 11 which penetrates through the upper surface and the lower surface of the conductor layer 1 is arranged on the conductor layer 1, so that volatile matters in the adhesive film layer 2 can be exhausted through the through hole 11 of the conductor layer 1 at high temperature, and the problem that the volatile matters in the adhesive film layer 2 are difficult to exhaust at high temperature is avoided, so that the free grounding film is prevented from being peeled off from the electromagnetic shielding film 5 due to bubbling and layering of the; in addition, when the free grounding film is used for grounding the printed circuit board 6, the electromagnetic shielding film 5 is arranged on the printed circuit board 6, the electromagnetic shielding film 5 comprises a shielding layer 52 and an insulating layer 51, the insulating layer 51 is arranged on the shielding layer 52, and when the free grounding film is pressed with the electromagnetic shielding film 5, the adhesive film layer 2 and the insulating layer 51 are pierced through by the uneven surface of the conductor layer 1 and are electrically connected with the shielding layer 52; when the printed circuit board 6 is applied to electronic equipment, the printed circuit board can be electrically connected with a shell of the electronic equipment through the free grounding film, so that interference charges accumulated on the electromagnetic shielding film 5 can be led out through the free grounding film, the interference charges can be led out through the shell of the electronic equipment, the grounding of the electromagnetic shielding film 5 is further ensured, the interference charges accumulated on the electromagnetic shielding film 5 are led out, and the interference sources formed by the accumulation of the interference charges are prevented from influencing the normal work of the printed circuit board 6; in addition, because the one side that conductor layer 1 is close to glued membrane layer 2 is uneven surface, consequently when free ground membrane and electromagnetic shielding film 5 pressfitting, glue class material that constitutes glued membrane layer 2 is extruded in this uneven surface's the sunk position, with the increase volume of glue holding, thereby be difficult to appear the phenomenon that free ground membrane and electromagnetic shielding film 5 break away from, avoided current electromagnetic shielding film because the volume of glue holding is not enough leads to free ground membrane and the problem that the electromagnetic shielding film breaks away from, and then guaranteed electromagnetic shielding film ground connection effectively, thereby will disturb the electric charge and derive.
The above description is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and substitutions can be made without departing from the technical principle of the present invention, and these modifications and substitutions should also be regarded as the protection scope of the present invention.

Claims (18)

1. A free grounding film is characterized by comprising a conductor layer and a glue film layer, wherein the glue film layer is arranged on the conductor layer; a through hole penetrating through the upper surface and the lower surface of the conductor layer is formed in the conductor layer, and one surface, close to the adhesive film layer, of the conductor layer is a non-flat surface; when the free grounding film is used for grounding a printed circuit board, an electromagnetic shielding film is arranged on the printed circuit board and comprises a shielding layer and an insulating layer, the insulating layer is arranged on the shielding layer, the free grounding film is pressed with the electromagnetic shielding film through the adhesive film layer, and the conductor layer pierces the adhesive film layer and the insulating layer and is electrically connected with the shielding layer.
2. The free grounding film of claim 1, wherein a surface of the conductor layer adjacent to the adhesive film layer comprises a plurality of protrusions and a plurality of recesses, and the plurality of protrusions and the plurality of recesses are arranged at intervals.
3. A free-grounding film as claimed in claim 1, wherein the uneven surface of the conductor layer is provided with convex first conductor particles.
4. The free grounding film of claim 3, wherein the first conductor particles have a height of 35 μm to 100 μm.
5. The free grounding film of claim 1, wherein the conductor layer has a thickness of 0.01 μ ι η to 45 μ ι η and the glue film layer has a thickness of 0.1 μ ι η to 80 μ ι η.
6. The free grounding film of any one of claims 1 to 5, wherein the glue layer comprises an adhesive layer containing conductive particles; or the adhesive film layer comprises an adhesion layer without conductive particles.
7. The free grounding film of any one of claims 1 to 5, wherein the free grounding film further comprises an oxidation preventing layer, and the oxidation preventing layer is arranged on a surface of the conductor layer away from the adhesive film layer.
8. The free grounding film of any of claims 1 to 5, further comprising a peelable protective film layer disposed on a side of the glue film layer remote from the conductor layer.
9. The free grounding film of any of claims 1 to 5, wherein the through-holes have an area of 0.01 μm 2-1mm 2。
10. The free grounding film of any of claims 1 to 5, wherein the number of the vias in the conductor layer per square centimeter is from 5 to 10 6And (4) respectively.
11. A circuit board comprising the electromagnetic shielding film, the printed circuit board and the free grounding film of any one of claims 1 to 10, wherein the electromagnetic shielding film is disposed on the printed circuit board, the electromagnetic shielding film comprises a shielding layer and an insulating layer, the insulating layer is disposed on the shielding layer, the free grounding film is laminated with the electromagnetic shielding film through the adhesive film layer, and the conductor layer pierces the adhesive film layer and the insulating layer and is electrically connected with the shielding layer.
12. The circuit board of claim 11, wherein the electromagnetic shielding film further comprises an adhesive layer, the adhesive layer is disposed on a surface of the shielding layer away from the insulating layer, and second conductive particles are disposed on a surface of the shielding layer close to the adhesive layer, and the second conductive particles pierce the adhesive layer and are electrically connected to the ground layer of the printed circuit board.
13. A method for preparing a free-grounding film, suitable for preparing the free-grounding film of any one of claims 1 to 10, comprising the steps of:
forming a conductor layer; the conductive layer is provided with a through hole penetrating through the upper surface and the lower surface of the conductive layer, and one surface of the conductive layer is a non-flat surface;
forming an adhesive film layer on the non-flat surface of the conductor layer;
when the free grounding film is used for grounding a printed circuit board, an electromagnetic shielding film is arranged on the printed circuit board and comprises a shielding layer and an insulating layer, the insulating layer is arranged on the shielding layer, the free grounding film is pressed with the electromagnetic shielding film through the adhesive film layer, and the conductor layer pierces the adhesive film layer and the insulating layer and is electrically connected with the shielding layer.
14. The method of making a free-grounding film of claim 13, wherein the forming a conductor layer specifically comprises:
forming an oxidation preventing layer on the carrier film;
forming a conductor layer on the oxidation preventing layer; or the like, or, alternatively,
forming a conductor layer on the surface of the strippable layer with the carrier;
forming an anti-oxidation layer on the conductor layer;
peeling the peelable layer of the tape carrier.
15. The method of making a free-grounding film as claimed in claim 13, further comprising, before forming the glue film layer on the non-planar surface of the conductor layer:
convex first conductor particles are formed on the uneven surface of the conductor layer.
16. The method for preparing a free-grounding film as claimed in claim 15, wherein the step of forming the first conductor particles having a convex shape on the uneven surface of the conductor layer comprises:
the first conductor particles are formed on the non-planar surface of the conductor layer by one or more of physical roughening, electroless plating, physical vapor deposition, chemical vapor deposition, evaporation plating, sputter plating, electroplating, and hybrid plating.
17. A method for preparing a free grounding film according to any one of claims 13 to 16, wherein a glue film layer is formed on the non-flat surface of the conductor layer, specifically:
coating a glue film layer on the release film;
pressing and transferring the adhesive film layer to the non-flat surface of the conductor layer; or the like, or, alternatively,
and coating a glue film layer on the non-flat surface of the conductor layer.
18. The method for preparing a free grounding film as claimed in any one of claims 13 to 16, wherein after forming the adhesive film layer on the non-flat surface of the conductor layer, the method further comprises:
and forming a strippable protective film layer on the adhesive film layer.
CN201811424089.9A 2018-11-26 2018-11-26 Free grounding film, circuit board and preparation method of free grounding film Pending CN110784988A (en)

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CN201811424089.9A CN110784988A (en) 2018-11-26 2018-11-26 Free grounding film, circuit board and preparation method of free grounding film

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN201811424089.9A CN110784988A (en) 2018-11-26 2018-11-26 Free grounding film, circuit board and preparation method of free grounding film

Publications (1)

Publication Number Publication Date
CN110784988A true CN110784988A (en) 2020-02-11

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Country Link
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