CN110784983A - 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 PDFInfo
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- CN110784983A CN110784983A CN201811423676.6A CN201811423676A CN110784983A CN 110784983 A CN110784983 A CN 110784983A CN 201811423676 A CN201811423676 A CN 201811423676A CN 110784983 A CN110784983 A CN 110784983A
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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
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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
- 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 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 first conductor layer, a second conductor layer and a glue film layer, and a resin bulge formed by solidifying resin after the resin flows from one side of a first through hole to the other side of the first through hole is arranged at the first through hole of the first conductor layer; the second conductor layer is arranged on one side, close to the resin bulge, of the first conductor layer, so that a bulge part is formed on the outer surface of the second conductor layer at a position corresponding to the resin bulge; the glue film layer is arranged on one side of the second conductor layer far away from the first conductor layer; when the free grounding film is used for grounding of a printed circuit board, the free grounding film can be pressed with the electromagnetic shielding film on the printed circuit board through the adhesive film layer, the protruding part pierces through the insulating layers of the adhesive film layer and the electromagnetic shielding film and is electrically connected with the shielding layer of the electromagnetic shielding film, so that interference charges accumulated on the shielding layer are effectively led out, the accumulation of the interference charges is avoided to form an interference source, and the integrity of signal transmission is effectively ensured.
Description
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 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 the shielding layer of the electromagnetic shielding film through the conductive adhesive layer, so that when the printed circuit board is applied to electronic equipment, the printed circuit board can be electrically connected with the shell of the electronic equipment through the free grounding film, and interference charges of the circuit board are led out. However, in the process of implementing the invention, the inventor finds that the prior art has at least the following problems: at high temperature, because the conductive adhesive layer expands, the conductive particles which originally contact with each other in the conductive adhesive layer are pulled apart or the conductive particles which originally contact with the electromagnetic shielding film are pulled apart, so that the connection failure of the free grounding film and the electromagnetic shielding film is caused, and the interference charges accumulated on the electromagnetic shielding film can not be effectively led out, thereby forming an interference source and influencing the signal transmission of the circuit board.
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 realize reliable connection of the free grounding film and an electromagnetic shielding film so as to ensure that interference charges in the electromagnetic shielding film can be led out and ensure the integrity of signal transmission.
In order to solve the technical problem, the invention provides a free grounding film, which comprises a first conductor layer, a second conductor layer and a film adhesive layer, wherein the first conductor layer is provided with a first through hole penetrating through the upper surface and the lower surface of the first conductor layer, a resin bulge is arranged at the first through hole, and the resin bulge is formed by solidifying resin after the resin flows from one side of the first through hole to the other side; the second conductor layer is arranged on one side, close to the resin bulge, of the first conductor layer and covers the resin bulge, so that a bulge part is formed on the outer surface of the second conductor layer at a position corresponding to the resin bulge; the glue film layer is arranged on one side, far away from the first conductor layer, of the second conductor layer;
when the free grounding film is used for grounding the printed circuit board, an electromagnetic shielding film is arranged on the printed circuit board and comprises a shielding layer and an insulating layer which are arranged in a stacked mode, the free grounding film is in press fit with the electromagnetic shielding film through the glue film layer, and the protruding portion penetrates through the glue film layer and the insulating layer and is electrically connected with the shielding layer.
As a modification of the above, the resin projection is formed by solidifying at a curing temperature after resin flows from one side to the other side of the first through hole at normal temperature; or the like, or, alternatively,
the resin protrusion is formed by instantly cooling after resin flows from one side to the other side of the first through hole at a melting temperature.
As an improvement of the above scheme, the surface of the convex part is provided with convex conductor particles; the height of the conductor particles is 20-100 μm.
As an improvement of the above scheme, the adhesive film layer includes an adhesive layer containing conductive particles; or the adhesive film layer comprises an adhesion layer without conductive particles.
As an improvement of the above scheme, the first conductor layer and the second conductor layer respectively include one or more of a metal conductor layer, a carbon nanotube conductor layer, a ferrite conductor layer, and a graphene conductor layer.
As a modification of the above, the metal conductor layer includes 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.
As an improvement of the above scheme, the number of the first through holes in the first conductor layer per square centimeter is 5 to 10
6A plurality of; and/or the cross-sectional area of the first through hole is 0.01 mu m
2-1mm
2。
As an improvement of the above scheme, the free grounding film further includes an oxidation prevention layer, and the oxidation prevention layer is disposed on a surface of the first conductor layer away from the second conductor layer.
As an improvement of the scheme, the free grounding film further comprises a strippable protective film layer, and the strippable protective film layer is arranged on one surface, away from the second conductor layer, of the adhesive film layer.
Compared with the prior art, the embodiment of the invention discloses a free grounding film, wherein the resin bulge is arranged at the first through hole of the first conductor layer, the second conductor layer is arranged at one side of the first conductor layer close to the resin bulge, so that a bulge part is formed at the position of the outer surface of the second conductor layer corresponding to the resin bulge, and the adhesive film layer is arranged at one side of the second conductor layer far from the first conductor layer, so that when the free grounding film is pressed with the electromagnetic shielding film through the adhesive film layer, the bulge part can sequentially pierce the adhesive film layer and the insulating layer of the electromagnetic shielding film and is connected with the shielding layer of the electromagnetic shielding film, thereby effectively leading out the interference charges accumulated in the electromagnetic shielding film, further ensuring the grounding of the electromagnetic shielding film and effectively avoiding the phenomenon that at high temperature, the free grounding film is pressed with the electromagnetic shielding film through the conductive adhesive layer, so that the problem that the connection between the free grounding film and the electromagnetic shielding film fails and the interference charges cannot be rapidly led out is solved, and the influence on the normal work of the printed circuit board caused by the accumulation of the interference charges is effectively avoided.
In order to solve the same technical problem, the invention also provides a circuit board, which comprises a printed circuit board, an electromagnetic shielding film and the free grounding film, wherein the electromagnetic shielding film is arranged on the printed circuit board and comprises a shielding layer and an insulating layer which are arranged in a laminated manner, the free grounding film is laminated with the electromagnetic shielding film through the adhesive film layer, and the bulge part pierces through the adhesive film layer and the insulating layer and is electrically connected with the shielding layer.
Compared with the prior art, the embodiment of the invention discloses a circuit board, which comprises a printed circuit board, an electromagnetic shielding film and a free grounding film, when the free grounding film is pressed with the electromagnetic shielding film through the adhesive film layer, the bulge part can sequentially pierce the adhesive film layer and the insulating layer of the electromagnetic shielding film and is connected with the shielding layer of the electromagnetic shielding film, thereby effectively guiding out the interference charges accumulated in the electromagnetic shielding film, further ensuring the grounding of the electromagnetic shielding film, effectively avoiding the phenomenon that at high temperature, the free grounding film is pressed with the electromagnetic shielding film through the conductive adhesive layer, so that the problem that the connection between the free grounding film and the electromagnetic shielding film fails and the interference charges cannot be rapidly led out is solved, and the influence on the normal work of the printed circuit board caused by the accumulation of the interference charges is effectively avoided.
In order to solve the same technical problem, the invention also provides a preparation method of the free grounding film, which is suitable for preparing the free grounding film and comprises the following steps:
forming a first conductor layer; wherein the first conductor layer is formed with a first through hole penetrating through the upper and lower surfaces thereof;
forming a resin protrusion at the first through hole; wherein the resin projection protrudes out of the first through hole;
forming a second conductor layer on the first conductor layer on the side where the resin projection is formed, and forming a projection portion on the outer surface of the second conductor layer at a position corresponding to the resin projection by covering the resin projection with the second conductor layer;
forming a glue film layer on one side of the second conductor layer, which is far away from the first conductor layer; when the free grounding film is used for grounding the printed circuit board, an electromagnetic shielding film is arranged on the printed circuit board and comprises a shielding layer and an insulating layer which are arranged in a stacked mode, the free grounding film is in press fit with the electromagnetic shielding film through the adhesive film layer, and the protruding portion penetrates through the adhesive film layer and the insulating layer and is electrically connected with the shielding layer.
As an improvement of the above scheme, the forming of the resin protrusion at the first through hole specifically includes:
setting resin at the first through hole, and solidifying the resin at a curing temperature after the resin flows from one side to the other side of the first through hole at normal temperature, so as to form a resin bulge at the first through hole; or the like, or, alternatively,
and arranging resin at the first through hole, and instantly cooling after the resin flows from one side to the other side of the first through hole at a melting temperature, thereby forming a resin protrusion at the first through hole.
As an improvement of the above scheme, before forming the adhesive film layer on the side of the second conductor layer away from the first conductor layer, the method further includes the following steps:
forming conductor particles on the outer surface of the protrusion part by one or more processes of physical roughening, chemical plating, physical vapor deposition, chemical vapor deposition, evaporation plating, sputtering plating, electroplating and hybrid plating.
As an improvement of the above scheme, the forming of the glue film layer on the side of the second conductor layer away from the first conductor layer specifically includes:
coating a glue film layer on a release film, and transferring the glue film layer to one side of a second conductor layer far away from a first conductor layer in a pressing mode; or
And coating a glue film layer on one side of the second conductor layer, which is far away from the first conductor layer.
Compared with the prior art, in the preparation method of the free grounding film provided by the embodiment of the invention, the resin protrusion is formed at the first through hole of the first conductor layer, the second conductor layer is formed at the side of the first conductor layer where the resin protrusion is formed, so that the protrusion part is formed at the position of the outer surface of the second conductor layer corresponding to the resin protrusion, and finally the adhesive film layer is formed at the side of the second conductor layer far away from the first conductor layer, so that when the free grounding film is pressed with the electromagnetic shielding film through the adhesive film layer, the protrusion part can sequentially pierce the adhesive film layer and the insulating layer of the electromagnetic shielding film and is connected with the shielding layer of the electromagnetic shielding film, thereby effectively guiding out the interference charges accumulated in the electromagnetic shielding film and further ensuring the grounding of the electromagnetic shielding film, the problem that interference charges cannot be rapidly led out due to the fact that the free grounding film is in failure in connection with the electromagnetic shielding film due to the fact that the free grounding film is pressed with the electromagnetic shielding film through the conductive adhesive layer at high temperature is effectively solved, and therefore the problem that the accumulation of the interference charges affects normal work of the printed circuit board is effectively avoided.
Drawings
FIG. 1 is a schematic structural diagram of a free grounding film according to a first embodiment of the present invention;
FIG. 2 is a cross-sectional view of a free-grounding film in accordance with a first embodiment of the present invention;
FIG. 3 is a schematic structural diagram of a free grounding film in a second embodiment of the present invention;
fig. 4 is a schematic structural diagram of a circuit board in a third embodiment of the present invention;
fig. 5 is a schematic flow chart of a method for manufacturing a free-grounding film in the fourth embodiment of the present invention.
Wherein, 1, a first conductor layer; 11. a first through hole; 12. resin bumps; 13. a first surface; 14. a second surface; 2. a second conductor layer; 21. a boss portion; 22. a conductive particle; 3. a glue film layer; 4. a strippable protective film layer; 5. an oxidation-resistant layer; 6. an electromagnetic shielding film; 61. an insulating layer; 62. a shielding layer; 7. a printed wiring board.
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.
Example one
With reference to fig. 1 and 2, the printed circuit board includes a first conductor layer 1, a second conductor layer 2, and an adhesive film layer 3, wherein a first through hole 11 penetrating through upper and lower surfaces of the first conductor layer 1 is formed in the first conductor layer 1, a resin protrusion 12 is formed at the first through hole 11, and the resin protrusion 12 is formed by resin flowing from one side of the first through hole 11 to the other side and then solidifying; the second conductor layer 2 is arranged on one side of the first conductor layer 1 close to the resin bump 12 and covers the resin bump 12, so that a bump part 21 is formed on the outer surface of the second conductor layer 2 at a position corresponding to the resin bump 12; the glue film layer 3 is arranged on one side, far away from the first conductor layer 1, of the second conductor layer 2;
as shown in fig. 4, when the free grounding film is used for grounding a printed circuit board, an electromagnetic shielding film 6 is arranged on the printed circuit board 7, the electromagnetic shielding film 6 includes a shielding layer 62 and an insulating layer 61 which are stacked, the free grounding film is pressed with the electromagnetic shielding film 6 through the glue film layer 3, and the protruding portion 21 pierces through the glue film layer 3 and the insulating layer 61 and is electrically connected with the shielding layer 62.
In the embodiment of the present invention, the resin bump 12 is disposed at the first through hole 11 of the first conductor layer 1, and the second conductor layer 2 is disposed at the side of the first conductor layer 1 close to the resin bump 12, so as to form the bump 21 at the position corresponding to the resin bump 12 on the outer surface of the second conductor layer 2, and at the same time, the adhesive film layer 3 is disposed at the side of the second conductor layer 2 away from the first conductor layer 1, so that when the free contact grounding film is pressed against the electromagnetic shielding film 6 through the adhesive film layer 3 thereof, the bump 21 can sequentially pierce through the adhesive film layer 3 and the insulating layer 61 of the electromagnetic shielding film 6 and is connected with the shielding layer 62 of the electromagnetic shielding film 6, thereby effectively guiding out the interference charges accumulated in the electromagnetic shielding film 6, and further ensuring the grounding of the electromagnetic shielding film 6, the problem that interference charges cannot be rapidly led out due to the fact that the free grounding film is in failure in connection with the electromagnetic shielding film due to the fact that the free grounding film is pressed with the electromagnetic shielding film through the conductive adhesive layer at high temperature is effectively solved, therefore, the phenomenon that the interference charges are accumulated to influence normal work of the printed circuit board is effectively avoided, and the integrity of signal transmission is guaranteed.
In the embodiment of the present invention, in one preferable mode, the process of forming the resin projection 12 is specifically represented as follows: the resin protrusion 12 is formed by instant cooling after the resin flows from one side to the other side of the first through hole 11 at the melting temperature. In another preferred embodiment, the resin is a curing adhesive, and the forming process of the resin protrusion 12 is embodied as follows: at normal temperature, the liquefied resin is solidified at a curing temperature after flowing from one side to the other side of the first through hole 11. The resin forming the resin bump 12 may be provided at one end of the first through hole 11 away from the second conductor layer 2, or may be provided on one surface of the first conductor layer 1 away from the second conductor layer 2; the resin may be a thermoplastic resin or a thermosetting resin.
In the embodiment of the present invention, it should be noted that the structure of the resin protrusion 12 shown in the drawings is merely exemplary. Since the resin bumps 12 are formed by solidification after the resin flows from one side to the other side of the first through-holes 11, in either case, the resin flows almost completely out of the first through-holes 11 with no residue in the first through-holes 11, and thus the resin bumps 12 can be formed as shown in the drawings, the resin bumps 12 being formed at the boundaries of the first through-holes 11 and the second conductor layer 2; in another case, resin remains in the first through hole 11, and the first through hole 11 is even filled with resin, so that one end of the resin projection 12 is formed to be located in the first through hole 11 and the other end of the resin projection 12 protrudes out of the first through hole 11; in still another case, a resin remains on a surface of the first conductor layer 1 on a side away from the second conductor layer 2, and therefore, the resin bump 12 may be formed to penetrate the first through hole 11. The resin protrusion 12 of the present invention is not limited to the shape shown in the drawings, and any resin protrusion having a piercing ability is within the scope of the present invention.
In the embodiment of the present invention, in order to ensure that the resin bump 12 can be formed at the first through hole 11 while ensuring that the first conductor layer 1 is not easily broken, it is preferable that the cross-sectional area of the first through hole 11 in the embodiment is 0.01 μm
2-1mm
2。
In addition, in order to ensure that enough resin bumps 12 can be formed on the first conductor layer 1 to ensure that the bumps 21 formed on the second conductor layer 2 can smoothly penetrate through the adhesive film layer 3 and the insulating layer 61 of the electromagnetic shielding film 6 and connect with the shielding layer 62, and to ensure that the first conductor layer 1 is not easily broken, the number of the first through holes 11 in the first conductor layer 1 per square centimeter is 5 to 10 in the present embodiment
10And (4) respectively. Accordingly, the number of the resin projections 12 per square centimeter of the first conductor layer film 1 is 5 to 10
10A plurality of; it should be noted that, since the second conductor layer 2 covers the resin bumps 12, the protrusions 21 are formed at the positions of the outer surface of the second conductor layer 2 corresponding to the resin bumps 12, and therefore, the number of the protrusions 21 corresponds to the number of the resin bumps 12, thereby ensuring that the adhesive film layer 3 and the electromagnetic shielding film 6 can be smoothly pierced throughAnd an insulating layer 61.
In the embodiment of the present invention, the first through holes 11 may be regularly or irregularly distributed on the first shielding layer 1; wherein, the first through holes 11 are regularly distributed on the first conductor layer 1, which means that the shapes of the first through holes 11 are the same and are uniformly distributed on the first conductor layer 1; the first through holes 11 are irregularly distributed on the first conductor layer 1, that is, the first through holes 11 have different shapes and are irregularly distributed on the first conductor layer 1. Preferably, the shapes of the first through holes 11 are the same, and the first through holes 11 are uniformly distributed on the first conductor layer 1, as shown in fig. 2. In addition, the first through hole 11 may be a circular through hole, and may also be a through hole of any other shape, and the drawings of the present invention only illustrate that the first through hole 11 is a circular through hole, but the first through hole 11 of any other shape is within the scope of the present invention.
In the embodiment of the present invention, the shape of the protrusion 21 may be the same as the shape of the resin protrusion 12, or may be different from the shape of the resin protrusion 12, and the shape of the protrusion 21 shown in the drawings is merely exemplary.
In the embodiment of the present invention, the thickness of the first conductor layer 1 is preferably 2 μm to 45 μm; the thickness of the second conductor layer 2 is preferably 2 μm to 45 μm, thereby ensuring that the first conductor layer 1 and the second conductor layer 2 are not easily broken and have good flexibility. In order to ensure that the first conductor layer 1 and the second conductor layer 2 have good conductivity, the first 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; the second conductor layer 2 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.
In the embodiment of the present invention, the first conductor layer 1 includes a first surface 13 and a second surface 14 which are oppositely arranged, and the first surface 13 is in contact with the second conductor layer 2; the second surface 14 is in contact with the protective film layer 4. It should be noted that the first surface 13 and the second surface 14 may be surfaces of any shape, for example, flat surfaces as shown in fig. 1, uneven surfaces with a wavy shape, or other rough surfaces; in addition, the first surface 13 and the second surface 14 may be regular surfaces or irregular surfaces. The drawings of the present invention only illustrate that the first surface 13 and the second surface 14 are flat surfaces, and any other shapes of the first surface 13 and the second surface 14 are within the scope of the present invention. In addition, a surface of the second conductor layer 2 contacting the first surface 13 may also be a surface of any shape, for example, a flat surface as shown in fig. 1, a non-flat surface with a wavy shape, or other rough surfaces, which will not be described herein.
In the embodiment of the present invention, it should be noted that, in the drawings of the present embodiment, both the first conductor layer 1 and the second conductor layer 2 may have a single-layer structure or a multi-layer structure. In addition, the first conductor layer 1 and the second conductor layer 2 of the present embodiment can be arranged in a grid shape, a foam shape, etc. according to the requirements of actual production and application.
In the embodiment of the present invention, one of the structures of the adhesive film layer 3 is specifically represented as follows: the adhesive layer 3 includes an adhesive layer containing conductive particles. The adhesive film layer 3 includes an adhesive layer containing conductive particles, so that the adhesive film layer 3 has an adhesive function to tightly adhere the free grounding film and the electromagnetic shielding film 6, and the adhesive film layer 3 also has a conductive function to cooperate with the second conductor layer 2 and the first conductor layer 1 to rapidly guide out interfering electrons. The conductive particles can be mutually separated conductive particles or aggregated large-particle conductive particles; when the conductive particles are mutually separated, the area of electrical contact can be further increased, and the uniformity of the electrical contact is improved; and when the conductive particles are large agglomerated conductive particles, the piercing strength can be increased.
In the embodiment of the present invention, another structure of the adhesive film layer 3 is specifically represented as follows: the adhesive layer 3 includes an adhesive layer containing no conductive particles. The adhesive film layer 3 has an adhesive effect by making the adhesive film layer 3 include an adhesive layer without conductive particles, so that the free grounding film and the electromagnetic shielding film 6 are tightly adhered, and meanwhile, because the adhesive film layer 3 includes an adhesive layer without conductive particles, the insertion loss of the circuit board in the using process is reduced, and the bending property of the circuit board is improved.
In the embodiment of the present invention, the thickness of the adhesive film layer 3 is 0.1 μm to 80 μm. The glue film layer 3 is made of the following materials: modified epoxy resins, acrylic resins, modified rubbers, and modified thermoplastic polyimides. In addition, the outer surface of the adhesive film layer 3 may be a flat surface without undulation, or may be a non-flat surface with gentle undulation.
As shown in fig. 1, in order to protect the adhesive film layer 3, the free grounding film in this embodiment further includes a peelable protective film layer 4, and the peelable protective film layer 4 is disposed on a surface of the adhesive film layer 3 away from the second conductor layer 2. The peelable protective film layer 4 plays a role in protection so as to prevent the adhesive film layer 3 from being damaged before use, and therefore the free grounding film can be pressed with the electromagnetic shielding film 6 through the adhesive film layer 3. It should be noted that, when the free grounding film is laminated on the electromagnetic shielding film 6, the peelable protective film layer 4 needs to be peeled off, and then the free grounding film is laminated on the electromagnetic shielding film 6 through the adhesive film layer 3.
In addition, the peelable protective film layer 4 includes a PPS film layer, a PEN film layer, a polyester film layer, a polyimide film layer, a film layer formed after curing of epoxy resin ink, a film layer formed after curing of polyurethane ink, a film layer formed after curing of modified acrylic resin, or a film layer formed after curing of polyimide resin.
In the embodiment of the present invention, in order to protect the first conductor layer 1 and ensure that the interference charges can be led out, in this embodiment, the free grounding film further includes an anti-oxidation layer 5, and the anti-oxidation layer 5 is disposed on a surface of the first conductor layer 1 away from the second conductor layer 2. The anti-oxidation layer 5 is arranged on one surface, far away from the second conductor layer 2, of the first conductor layer 1, so that the first conductor layer 1 is prevented from being oxidized due to contact with air, and therefore it is guaranteed that interference charges in the electromagnetic shielding film 6 can be led out through the free grounding film.
In one preferable mode, the material of the oxidation preventing layer 5 is one of a metal material, ferrite, graphite, a carbon nanotube, graphene, and silver paste; wherein 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 formed by two or more of aluminum, titanium, zinc, iron, nickel, chromium, cobalt, copper, silver, gold and molybdenum; in this case, the thickness of the oxidation preventing layer 5 is 0.01 μm to 5 μm, and the thickness of the oxidation preventing layer 5 is preferably 0.1 μm to 1 μm. In addition, the oxidation preventing layer 5 may be formed by one or a composite process of at least two of chemical plating, physical vapor deposition, chemical vapor deposition, evaporation plating, sputtering plating, and electroplating.
In another preferred mode, the oxidation preventing layer 5 is made of a mixture of glue and conductive particles; wherein the volume ratio of the conductive particles to the glue is 5-80%; in this case, the thickness of the oxidation preventing layer 5 is preferably 0.1 μm to 5 μm. The oxidation preventing layer 5 may be formed by a process of curing after coating.
Example two
As shown in fig. 3, the free-ground film in the present embodiment is different from the first embodiment in that the surface of the protruding portion 21 is provided with convex conductor particles 22. By arranging the conductor particles 22 on the surface of the protruding portion 21, the protruding portion 21 can more easily pierce through the adhesive film layer 3 and the insulating layer 61 of the electromagnetic shielding film 6, thereby ensuring that the interference charges can be conducted out.
Preferably, the conductive particles 22 are distributed in a concentrated manner on the outwardly protruding positions of the surface of the protruding portion 21, so that the adhesive film layer 3 is easier to pierce. Of course, the non-convex portions of the surface of the convex portion 21 may have the conductive particles 22 distributed. In addition, the conductor particles 22 may also be distributed on other positions of the second conductor layer 2 near the surface of the adhesive film layer 3, not only on the surface of the protruding portion 21, as shown in fig. 3. Of course, the conductor particles 22 may also be distributed only on the projections 21.
In a specific implementation, as shown in fig. 3, the second conductor layer 2 may be formed first, and then the conductor particles 22 may be formed on a side of the second conductor layer 2 away from the first conductor layer 1 by another process. Of course, the second conductor layer 2 and the conductor particles 22 may be an integral structure formed by a one-step molding process.
In the embodiment of the present invention, the conductor particles 22 may be spaced from the outer surface of the adhesive film layer 3, and may also contact with the outer surface of the adhesive film layer 3 or extend out of the outer surface of the adhesive film layer 3.
In the embodiment of the present invention, the height of the conductor particles 22 is preferably 20 μm to 100 μm, the thickness of the adhesive film layer 3 is preferably 0.1 μm to 80 μm, and the thickness of the insulating layer 61 is preferably 1 μm to 20 μm. By providing the conductor particles 22 with a height of preferably 20 μm to 100 μm, the thickness of the glue film layer 3 is preferably 0.1 μm to 80 μm, so as to ensure that the conductor particles 22 can penetrate through the glue film layer 3 and the insulating layer 61 of the electromagnetic shielding film 6, thereby ensuring that the free grounding film can conduct away the interference charges accumulated on the electromagnetic shielding film 6.
In an embodiment of the present invention, the conductor particles 22 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. Note that the material of the conductor particles 22 may be the same as or different from that of the second conductor layer 2.
In the embodiment of the present invention, it should be noted that the shape of the conductor particles 22 shown in fig. 3 is only an example, and the conductor particles 22 may also be in other shapes such as clusters, ice-hanging shapes, stalactites, and dendrites due to differences in process means and parameters. The conductive particles 22 in the present invention are not limited to the shapes shown in the drawings and described above, and any conductive particles having piercing and conductive functions are within the scope of the present invention.
In addition, other structures and working principles of the free grounding film of the embodiment are the same as those of the first embodiment, and are not further described herein.
EXAMPLE III
As shown in fig. 4, an embodiment of the present invention further provides a circuit board, which includes a printed circuit board 7, an electromagnetic shielding film 6, and the free grounding film according to one or two embodiments, where the electromagnetic shielding film 6 is disposed on the printed circuit board 7, the electromagnetic shielding film 6 includes a shielding layer 62 and an insulating layer 61 that are stacked, the free grounding film is pressed against the electromagnetic shielding film 6 through the glue film layer 3, and the protruding portion 21 pierces through the glue film layer 3 and the insulating layer 61 and is electrically connected to the shielding layer 62.
In this embodiment, reference may be made to the description of the above embodiments for implementation of the free grounding film, and details are not repeated here.
Preferably, the printed circuit board 7 is one of a flexible single-sided board, a flexible double-sided board, a flexible multilayer board, and a rigid-flex printed board.
In a specific implementation, when the wiring board is applied to an electronic device, the interference charges accumulated in the electromagnetic shielding film 6 can be conducted out by electrically connecting the free grounding film with a housing of the electronic device.
In the embodiment of the present invention, with the above structure, in the process of pressing the free grounding film and the electromagnetic shielding film 6, the protruding portion 21 on the second conductor layer 2 is used to sequentially pierce the adhesive film layer 3 and the insulating layer 61, so that at least a part of the outer surface of the second conductor layer 2 is connected to the shielding layer 62 of the electromagnetic shielding film 6, and thus, under the cooperation of the first conductor layer 1 and the second conductor layer 2, the interference charges are led out, and the interference source formed by the accumulation of the interference charges is avoided, so that the normal operation of the circuit board is affected.
Example four
As shown in fig. 5, the method is suitable for preparing the free grounding film described in the first embodiment, and includes steps S1 to S4:
s1, forming a first conductor layer; the first conductor layer is provided with a first through hole penetrating through the upper surface and the lower surface of the first conductor layer;
wherein the first conductor layer is formed in step S1 by:
and forming an anti-oxidation layer on the carrier film, and forming the first conductor layer on one side of the anti-oxidation layer.
Or, a peelable layer is formed on a carrier film, the first conductor layer is formed on the surface of the peelable layer, and after an oxidation preventing layer is formed on the side of the first conductor layer away from the peelable layer, the carrier film layer is peeled.
In an embodiment of the present invention, the first through-hole has a cross-sectional area of 0.01 μm
2-1mm
2(ii) a The number of the first through holes in the first conductor layer per square centimeter is 5-10
6And (4) respectively.
S2, forming a resin bulge at the first through hole; wherein the resin projection protrudes out of the first through hole;
wherein the forming of the resin protrusion at the first through hole is specifically:
and arranging resin at the first through hole, and solidifying the resin after the resin flows from one side to the other side of the first through hole, so that a resin bulge is formed at the first through hole.
Specifically, in one of preferred modes, after a resin is provided at the first through hole and is caused to flow from one side to the other side of the first through hole at normal temperature, the resin is solidified at a curing temperature, thereby forming a resin protrusion at the first through hole; in yet another preferred embodiment, a resin is provided at the first through-hole and instantaneously cooled after flowing from one side to the other side of the first through-hole at a melting temperature, thereby forming a resin protrusion at the first through-hole.
S3, forming a second conductor layer on the side of the first conductor layer where the resin projection is formed, and forming a projection on the outer surface of the second conductor layer at a position corresponding to the resin projection by covering the resin projection with the second conductor layer;
s4, forming an adhesive film layer on one side, far away from the first conductor layer, of the second conductor layer; when the free grounding film is used for grounding the printed circuit board, an electromagnetic shielding film is arranged on the printed circuit board and comprises a shielding layer and an insulating layer which are arranged in a stacked mode, the free grounding film is in press fit with the electromagnetic shielding film through the adhesive film layer, and the protruding portion penetrates through the adhesive film layer and the insulating layer and is electrically connected with the shielding layer.
Wherein, form the glued membrane layer in the second conductor layer keeps away from one side of first conductor layer, specifically do:
coating an adhesive film layer on a release film, and then transferring the adhesive film layer to one side of the second conductor layer away from the first conductor layer in a pressing manner, so that the adhesive film layer is formed on one side of the second conductor layer away from the first conductor layer; or
And directly coating an adhesive film layer on one side of the second conductor layer, which is far away from the first conductor layer, so that the adhesive film layer is formed on one side of the second conductor layer, which is far away from the first conductor layer.
In another preferred embodiment suitable for preparing the electromagnetic shielding film of the second embodiment, after step S3 and before step S4, the method further comprises the steps of:
forming conductor particles on the outer surface of the protrusion part by one or more processes of physical roughening, chemical plating, physical vapor deposition, chemical vapor deposition, evaporation plating, sputtering plating, electroplating and hybrid plating.
To sum up, the embodiment of the present invention provides a free grounding film, a circuit board and a method for manufacturing the free grounding film, wherein the free grounding film includes a first conductor layer 1, a second conductor layer 2 and a glue film layer 3, a first through hole 11 penetrating through the upper and lower surfaces of the first conductor layer 1 is provided on the first conductor layer 1, a resin protrusion 12 is provided at the first through hole 11, and the resin protrusion 12 is formed by resin which is solidified after flowing from one side of the first through hole 11 to the other side; the second conductor layer 2 is arranged on one side of the first conductor layer 1 close to the resin bump 12 and covers the resin bump 12, so that a bump part 21 is formed on the outer surface of the second conductor layer 2 at a position corresponding to the resin bump 12; the glue film layer 3 is arranged on one side, far away from the first conductor layer 1, of the second conductor layer 2; when the free grounding film is used for grounding the printed circuit board, an electromagnetic shielding film 6 is arranged on the printed circuit board 7, the electromagnetic shielding film 6 comprises a shielding layer 62 and an insulating layer 61 which are stacked, the free grounding film is pressed with the electromagnetic shielding film 6 through the adhesive film layer 3, the boss 21 pierces the adhesive film layer 3 and the insulating layer 61 and is electrically connected to the shield layer 62, thereby effectively guiding out the interference charges accumulated in the electromagnetic shielding film 6, further ensuring the grounding of the electromagnetic shielding film 6, effectively avoiding that at high temperature, the free grounding film is pressed with the electromagnetic shielding film through the conductive adhesive layer, so that the problem that the connection between the free grounding film and the electromagnetic shielding film fails and the interference charges cannot be rapidly led out is solved, and the influence on the normal work of the printed circuit board caused by the accumulation of the interference charges is effectively avoided.
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 (14)
1. A free grounding film is characterized by comprising a first conductor layer, a second conductor layer and a film adhesive layer, wherein a first through hole penetrating through the upper surface and the lower surface of the first conductor layer is formed in the first conductor layer, a resin bulge is arranged at the first through hole, and the resin bulge is formed by solidifying resin after the resin flows from one side to the other side of the first through hole; the second conductor layer is arranged on one side, close to the resin bulge, of the first conductor layer and covers the resin bulge, so that a bulge part is formed on the outer surface of the second conductor layer at a position corresponding to the resin bulge; the glue film layer is arranged on one side, far away from the first conductor layer, of the second conductor layer;
when the free grounding film is used for grounding the printed circuit board, an electromagnetic shielding film is arranged on the printed circuit board and comprises a shielding layer and an insulating layer which are arranged in a stacked mode, the free grounding film is in press fit with the electromagnetic shielding film through the glue film layer, and the protruding portion penetrates through the glue film layer and the insulating layer and is electrically connected with the shielding layer.
2. The free grounding film of claim 1, wherein the resin protrusion is formed by solidification of resin at a curing temperature after the resin flows from one side to the other side of the first through hole at a normal temperature; or the like, or, alternatively,
the resin protrusion is formed by instantly cooling after resin flows from one side to the other side of the first through hole at a melting temperature.
3. The free grounding film of claim 1, wherein the surface of the protrusions is provided with convex conductor particles; the height of the conductor particles is 20-100 μm.
4. The free grounding film of claim 1, wherein the glue layer comprises an adhesive layer containing conductive particles; or the adhesive film layer comprises an adhesion layer without conductive particles.
5. The free grounding film of any of claims 1 to 4, wherein the first conductor layer and the second conductor layer comprise one or more of a metal conductor layer, a carbon nanotube conductor layer, a ferrite conductor layer, and a graphene conductor layer, respectively.
6. A free grounding film as claimed in claim 5, 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.
7. The free grounding film of any of claims 1 to 4, wherein the number of the first vias in the first conductor layer per square centimeter is from 5 to 10
6A plurality of; and/or the cross-sectional area of the first through hole is 0.01 mu m
2-1mm
2。
8. The free grounding film of any one of claims 1 to 4, wherein the free grounding film further comprises an oxidation preventing layer disposed on a side of the first conductor layer remote from the second conductor layer.
9. A free grounding film as claimed in any one of claims 1 to 4, further comprising a peelable protective film layer provided on the side of the adhesive film layer remote from the second conductor layer.
10. A circuit board comprising a printed circuit board, an electromagnetic shielding film and the free grounding film of any one of claims 1 to 9, wherein the electromagnetic shielding film is disposed on the printed circuit board, the electromagnetic shielding film comprises a shielding layer and an insulating layer which are stacked, the free grounding film is laminated with the electromagnetic shielding film through the adhesive film layer, and the protrusions pierce through the adhesive film layer and the insulating layer and are electrically connected to the shielding layer.
11. A method for preparing a free-grounding film, which is suitable for preparing the free-grounding film of any one of claims 1 to 9, comprising the steps of:
forming a first conductor layer; wherein the first conductor layer is formed with a first through hole penetrating through the upper and lower surfaces thereof;
forming a resin protrusion at the first through hole; wherein the resin projection protrudes out of the first through hole;
forming a second conductor layer on the first conductor layer on the side where the resin projection is formed, and forming a projection portion on the outer surface of the second conductor layer at a position corresponding to the resin projection by covering the resin projection with the second conductor layer;
forming a glue film layer on one side of the second conductor layer, which is far away from the first conductor layer; when the free grounding film is used for grounding the printed circuit board, an electromagnetic shielding film is arranged on the printed circuit board and comprises a shielding layer and an insulating layer which are arranged in a stacked mode, the free grounding film is in press fit with the electromagnetic shielding film through the adhesive film layer, and the protruding portion penetrates through the adhesive film layer and the insulating layer and is electrically connected with the shielding layer.
12. The method for preparing a free grounding film according to claim 11, wherein the resin protrusion is formed at the first through hole, specifically:
setting resin at the first through hole, and solidifying the resin at a curing temperature after the resin flows from one side to the other side of the first through hole at normal temperature, so as to form a resin bulge at the first through hole; or the like, or, alternatively,
and arranging resin at the first through hole, and instantly cooling after the resin flows from one side to the other side of the first through hole at a melting temperature, thereby forming a resin protrusion at the first through hole.
13. The method for preparing a free grounding film as claimed in claim 11, wherein before forming the adhesive film layer on the side of the second conductor layer away from the first conductor layer, the method further comprises the following steps:
forming conductor particles on the outer surface of the protrusion part by one or more processes of physical roughening, chemical plating, physical vapor deposition, chemical vapor deposition, evaporation plating, sputtering plating, electroplating and hybrid plating.
14. The method for preparing a free-grounding film according to claim 11, wherein a glue film layer is formed on a side of the second conductor layer away from the first conductor layer, specifically:
coating a glue film layer on a release film, and transferring the glue film layer to one side of a second conductor layer far away from a first conductor layer in a pressing mode; or the like, or, alternatively,
and coating a glue film layer on one side of the second conductor layer, which is far away from the first conductor layer.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201811423676.6A CN110784983A (en) | 2018-11-26 | 2018-11-26 | Free grounding film, circuit board and preparation method of free grounding film |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201811423676.6A CN110784983A (en) | 2018-11-26 | 2018-11-26 | Free grounding film, circuit board and preparation method of free grounding film |
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| CN110784983A true CN110784983A (en) | 2020-02-11 |
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ID=69383190
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114205997A (en) * | 2021-12-27 | 2022-03-18 | 武汉华星光电半导体显示技术有限公司 | Flexible circuit board and display module |
-
2018
- 2018-11-26 CN CN201811423676.6A patent/CN110784983A/en active Pending
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114205997A (en) * | 2021-12-27 | 2022-03-18 | 武汉华星光电半导体显示技术有限公司 | Flexible circuit board and display module |
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