WO2013097644A1

WO2013097644A1 - Flexible printed circuit board and manufacturing method thereof

Info

Publication number: WO2013097644A1
Application number: PCT/CN2012/087053
Authority: WO
Inventors: 孙睿
Original assignee: 华为终端有限公司
Priority date: 2011-12-26
Filing date: 2012-12-20
Publication date: 2013-07-04
Also published as: CN102573285B; CN102573285A

Abstract

The present invention relates to the technical field of communications, and disclosed are a flexible printed circuit board and a manufacturing method thereof, so as to solve the problem in the prior art that electromagnetic interference shielding needs to be designed on a surface of a flexible printed circuit board. A flexible printed circuit board comprises: a back surface cover film, a flexible laminated structure, a conductive structure, and a composite cover film. A ground pad on a surface of the flexible laminated structure is connected to the conductive structure. The composite cover film comprises a bonding adhesive layer, a lower flexible dielectric material layer, a composite layer, and an upper flexible dielectric material layer that are arranged sequentially from bottom to top. The composite cover film wraps the conductive structure. The conductive structure runs through the bonding adhesive layer and the lower flexible dielectric material layer, and is connected to the composite layer. The conductive structure is not exposed on an upper surface of the composite cover film.

Description

The present invention claims to be submitted to the Chinese Patent Office on December 26, 2011, and the application number is 201110442299.2 and submitted to the Chinese Patent Office on January 9, 2012, and the application number is 201210004696.6 Chinese patent application. Priority is hereby incorporated by reference in its entirety.

TECHNICAL FIELD The present invention relates to the field of communications technologies, and in particular, to a flexible printed circuit board and a method of fabricating the same. BACKGROUND OF THE INVENTION Flexible printed circuit boards or flexible printed circuit boards (Flexible Printed Circuit Boards, flexible circuit boards, hereinafter referred to as FPCs) are characterized by lightness and flexibility, in personal consumer electronic products. There is a high proportion of use; with the popular use of portable personal consumer electronics such as smart phones and tablets, the performance of FPC is also improved; because of the need to support high-quality audio and video playback, FPC is required to achieve high-definition audio and video. Signal transmission, in order to reduce the transmission interference of high-definition audio and video signals, and thus put forward higher requirements for FPC Electromagnetic Interference (hereinafter referred to as "Electromagnetic Interference").

In the prior art, the ΕΜΙ shielding method for FPC is to form a ΕΜΙ shield by adding an additional shielding layer on the surface of the FPC and connecting the shielding layer to the ground layer of the FPC. Summary of the invention

Embodiments of the present invention provide an FPC structure that can effectively shield germanium and a method of fabricating the same.

In order to achieve the above object, embodiments of the present invention use the following technical solutions:

An FPC comprising: a back cover film (CoverLay, a cover film, hereinafter referred to as CVL); a flexible laminate structure disposed on the back surface CVL; the flexible laminate structure including the flexible laminate structure a ground pad of the surface layer and a ground layer connected to the ground pad; a conductive structure is disposed on the surface of the ground pad; and a composite CVL is further disposed on the surface layer of the flexible laminated structure, the composite CVL, The adhesive layer, the lower flexible dielectric material layer, the composite layer and the upper flexible dielectric material layer are sequentially disposed from bottom to top; the composite CVL encapsulates the conductive structure, and the conductive structure passes through the The adhesive layer and the lower flexible dielectric material layer are in communication with the composite layer and are not exposed on the upper surface of the composite CVL.

A method for preparing an FPC, comprising:

Thermally pressing the back surface CVL under the flexible laminate structure;

Forming a conductive structure at a set height on a surface of the ground pad of the surface layer of the flexible laminated structure;

Forming a thermal composite CVL on the surface of the flexible laminate structure, the composite CVL encapsulating the conductive structure, the conductive structure passing through the adhesive layer of the composite CVL and the lower flexible dielectric material layer, The composite layers of the composite CVL are in communication, and the set height is such that the conductive structures are not exposed on the upper surface of the composite CVL.

An FPC and a preparation method thereof are provided by forming a conductive structure on a ground pad of an FPC, pressing a composite CVL by hot pressing on a surface layer of the flexible laminated structure, and causing the composite CVL to wrap the conductive structure And under a certain pressure, the conductive structure just pierces the adhesive layer of the composite CVL and the lower flexible dielectric material layer, and the electrically conductive composite layer and the ground pad of the surface of the flexible laminated structure are formed by the conductive structure Connected, EMI shielding, and by providing a conductive structure at a set height, the conductive structure is not exposed on the upper surface of the composite CVL, thereby eliminating the need to add an additional shielding layer on the FPC surface, thereby effectively achieving FPC's EMI shielding, while avoiding the charge overflow and external erosion caused by the exposed structure of the conductive structure, enhances the shielding effect of FPC on EMI, and prolongs the service life of FPC. BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a schematic diagram of an FPC according to an embodiment of the present invention;

2 is a schematic view showing a conductive structure of a FPC in a FPC according to an embodiment of the present invention;

3 is a flow chart of a method for preparing an FPC according to an embodiment of the present invention; FIG. 4 is a flow chart of forming a conductive structure by printing in a method for preparing an FPC according to an embodiment of the present invention;

5 is a cross-sectional view of a screen when a conductive structure is formed by printing in a method for preparing an FPC according to an embodiment of the present invention;

6 is a flow chart of forming a conductive structure by a spray coating method in a method for preparing an FPC according to an embodiment of the invention. BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, an FPC and a preparation method thereof according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

It should be understood that the described embodiments are only a part of the embodiments of the present invention, rather than All embodiments. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments of the present invention without departing from the inventive scope are the scope of the present invention.

An FPC, as shown in Figure 1, includes: a back surface CVL1; the back surface CVL1 is provided with a flexible laminated structure 2;

The flexible laminated structure 2 includes a ground pad 200 located on a surface layer of the flexible laminated structure 2 and a ground layer 20 in contact with the ground pad 200; and a conductive layer is disposed on a surface of the ground pad 200 Structure 4;

The flexible laminated structure surface layer 2 is further provided with a composite CVL3 comprising an adhesive layer 30, a lower flexible dielectric material layer 31, a composite layer 32 and an upper flexible layer arranged in this order from bottom to top. A dielectric material layer 33; the composite CVL3 encapsulates the conductive structure 4, and the conductive structure 4 is connected to the composite layer 32 through the adhesive layer 30 and the lower flexible dielectric material layer 31.

By forming a conductive structure on the ground pad of the FPC, the composite CVL is pressed by hot pressing on the surface layer of the flexible laminated structure, so that the composite CVL wraps the conductive structure, and the conductive structure just pierces the composite under a certain pressure. The adhesive layer of the CVL and the layer of the lower flexible dielectric material communicate the electrically conductive composite layer with the ground pad of the surface of the flexible laminated structure through the conductive structure for EMI shielding, and the conductive structure can be set by setting the height The conductive structure is not exposed on the upper surface of the composite CVL, thereby eliminating the need to add an additional shielding layer on the surface of the FPC, thereby effectively shielding the EMI of the FPC, and avoiding the leakage of the conductive structure. The charge overflow and external erosion enhance the shielding effect of FPC on EMI and prolong the service life of FPC. The ground layer 20 is a conductive metal. Optionally, the ground layer is made of copper. The back surface CVL1 includes: a first flexible dielectric material layer 10 for increasing FPC flexibility and a first adhesive layer 11 for bonding with other layer structures.

In the scenario shown in FIG. 1 , the flexible laminated structure 2 is a flexible copper Clad Laminate (FCCL), but is not limited thereto, and the flexible laminated structure 2 can also be used. A stacked structure of a plurality of double-sided FCCLs, a plurality of single-sided FCCL layers, or a combination of at least one double-sided FCCL and at least one single-sided FCCL; wherein a plurality of ground layers may be included. a plurality of layers of the dielectric material layer, and as shown in FIG. 1, the flexible laminate structure 2 includes at least one ground layer 20, at least one layer of the flexible dielectric material 21, and A ground pad 200 connected to the ground layer 20.

The double-sided FCCL2a of the FPC shown in FIG. 1 includes: a ground layer 20 and a second flexible dielectric material layer 21 for increasing flexibility of the ground layer 20; grounding is provided on the ground layer 20 The pad 200 and the signal trace 201 for transmitting data, wherein there is a gap between the ground pad 200 and the signal trace 201.

The first flexible dielectric material layer 10, the second flexible dielectric material layer 21, and the upper flexible The material of the dielectric material layer 33 and the lower flexible dielectric material layer 31 may be Polyimide (hereinafter referred to as PI), PolyEthylene Terephthalate (hereinafter referred to as PET), Polynaphthalene Dioxide. PolyEthylene Naphthalate (hereinafter referred to as PEN) or Polytetrafluoroethylene (Poly Tetra Fluoro Ethylene, hereinafter referred to as PTFE).

Wherein, because the PI has better heat resistance and flexibility, and the cost is relatively low, the first flexible dielectric material layer 10, the second flexible dielectric material layer 21, and the upper flexible dielectric material layer are preferred. The material of the 33 and lower flexible dielectric material layers 31 is PI.

The material of the composite layer is a composite material of a flexible material and a metal particle, and the composite layer has conductive properties by conductive metal particles while maintaining the flexibility of the composite layer; The material of the composite layer is preferably a composite material of PI and silver.

After the back surface CVL1 and the composite CVL3 are thermally pressed with the flexible laminate structure 2, in order to improve the thermal stability of bonding between the back surface CVL1 and the composite CVL3 and the flexible laminate structure 2, optionally, the adhesion The glue layer is epoxy or acrylate.

In Fig. 1, the conductive structure 4 may have a truncated cone shape.

The conductive structure is formed by a printing method or a dispensing point coating method; wherein the printing point coating method is specifically: the printing spot coating machine is positioned by a feature point on the target structure, The feature points are fixed patterns, such as a cross shape, a circle shape or a square shape; according to the relationship between the feature points and the position where the ink spot needs to be printed, the position where the dot coating needs to be applied is determined; where the dot coating is required , spraying the target material. In the present invention, the target structure is a flexible laminated structure, and the target material is a conductive material forming a conductive structure. In order to make the conductive structure 4 more easily pierce the adhesive layer 30 and the lower flexible dielectric material layer 31 of the composite CVL3 during the hot pressing of the composite CVL3, optionally, as shown in FIG. 2, the conductive structure 4 may be tapered; wherein in the scenario shown in FIG. 2, the flexible laminate structure 2 is a double-sided FCCL2a. The shape of the conductive structure 4 may also be other shapes.

The shape of the conductive structure 4 is not limited by the present invention, as long as the conductive composite layer can communicate with the ground pad of the surface of the flexible laminated structure through the conductive structure to form an EMI shield, that is, the conductive can be ensured. The adhesive layer and the lower flexible dielectric material layer passing through the composite cover film are in communication with the composite layer of the composite cover film, and are not exposed on the upper surface of the composite cover film. Among them, in the back surface CVL1 and the composite CVL3, the film structure mentioned in the present invention is not limited, and in order to realize other functions, a film structure of other materials may be provided in the back surface CVL1 and the composite CVL3. Regardless of the film structure, in the present invention, the other structure is pierced by the conductive structure 4 provided on the surface of the ground pad 200 to connect the composite layer 32 of the composite CVL3, and is not exposed on the upper surface of the composite CVL3, thereby Layer 32, conductive The Faraday cage formed by the structure 4 and the ground pad 200 effectively realizes the EMI shielding of the FPC, and at the same time avoids the charge overflow and external erosion caused by the exposure of the conductive structure 4, enhances the shielding effect of the FPC on EMI, and prolongs the FPC. Service life. The present invention is not limited to the structure of the film, and the present invention is applicable to various occasions and various film structures in which the conductive structure 4 is required to realize EMI shielding and to avoid the exposure of the conductive structure 4. Corresponding to the above-mentioned FPC, the present invention also provides a method for preparing the FPC, as shown in FIG. 3, comprising:

In order to make the description clearer, the following flexible laminated structure 2 is described by taking the double-sided FCCL2a in the scene shown in Figs. 1 and 2 as an example.

300. The surface of the flexible laminate is heat-pressed on the back surface CVL.

On the FPC production line, the back surface CVL1 and the double-sided FCCL2a are stacked on the lower heating plate of the hot press; the first adhesive layer 11 of the back surface CVL1 is bonded to the lower surface of the double-sided FCCL2a; The heating plate and the lower heating plate are pressed together and given a certain pressure, for example, 120 kg force; the pressure is maintained, and the upper heating plate and the lower heating plate are continuously maintained at a certain temperature, which is selected according to the material of the selected bonding adhesive. , may be a temperature between 50 degrees and 150 degrees (including 50 degrees and 150 degrees), for example 130 degrees; because the first adhesive layer 11 is epoxy or acrylate, when the temperature is raised to 130 degrees Under the epoxy resin or acrylate, the first adhesive layer 11 is cured, and the double-sided FCCL2a and the back surface CVL1 are stably bonded.

301. A conductive structure is disposed at a set height on a surface of the ground pad of the surface layer of the flexible laminated structure.

After the double-sided FCCL2a and the back surface CVL1 are bonded, it is necessary to form the conductive structure 4 on the ground pad 200 at a set height, and the conductive structure 4 is formed by a printing method or a printing dot coating method. When the conductive structure 4 is prepared by printing, as shown in FIG. 4, it is specifically:

400. Place the flexible laminate structure in a printing press and place a screen on the surface of the flexible laminate structure, wherein the ground pad corresponds to a mesh on the screen.

The double-sided FCCL2a bonded to the back surface CVL1 is taken out and placed in a printing machine; the screen 5 containing the mesh 50 as shown in FIG. 5 is placed on the double-sided FCCL2a, and is carried out on the double-sided FCCL2a. Optical positioning corresponds the mesh 50 to the ground pad 200 on the double-sided FCCL 2a.

401. Pour a conductor material forming the conductive structure on the screen, and fill the mesh with the conductor material by a doctor blade.

The printing machine pours the conductor material of the conductive structure 4 on the screen 5 and prints it The scraper of the machine scrapes the conductor material into the mesh 50, so that the conductor material fills the mesh 50 uniformly, so that the conductor material in the mesh 50 can be fully contacted with the ground pad 200 on the double-sided FCCL2a; The conductive structure 4 formed by the conductor material just pierces the adhesive layer 30 and the lower flexible dielectric material layer 31, and the height of the conductive structure 4 can be adjusted according to the thickness of the composite CVL3; the height of the conductive structure 4 is related to the thickness of the screen 5 Therefore, by adjusting the thickness of the screen 5 used, a highly-conductive conductive structure 4 can be formed so that the conductive structure 4 can be connected to the composite layer 32 in the composite CVL3.

402. Lift the screen upward to make the conductor material have a pointed shape.

When the conductor material is filled with the mesh 50 by the doctor blade, a part of the conductor material is accumulated around the mesh hole 50 of the screen 5, and at this time, the printing machine lifts up the screen 5 to make the stacked portion of the conductor material to the mesh 50. The center is moved such that the conductor material is tapered at the ground pad 200.

In order to make the tip taper of the conductor material more sharp, the conductive structure 4 after curing the conductor material is more likely to pierce the adhesive layer 30 and the lower flexible dielectric material layer 31 when the composite CVL3 is pressed. The mesh 50 of the screen 5 has a trapezoidal cross section.

By controlling the slope of the section trapezoid, when the screen 5 is lifted up, the tip end of the formed tapered tapered conductor material can be sharpened to form a pointed cone.

When the screen 5 is lifted up, the speed of the lifting can be accelerated, and the conductor structure 4 can be sharpened to form a pointed shape.

403. Curing the conductor material to form a conductive structure, wherein a height of the conductive structure is controlled by a thickness of the screen.

The conductive material of the tapered shape is solidified. Because the conductive material is mixed with epoxy resin or acrylate, the conductive material can be cured by ultraviolet light curing or heating. After the conductive material is cured, a conductive structure is formed. 4.

The set height can be set by controlling the thickness of the printing press screen 5, that is, the height can be set by setting the thickness of the printing machine screen, and the screen 5 can be formed by an electroforming process; The screen is provided with a plurality of meshes 50 corresponding to the positions at which the target structure needs to be formed; the thickness of the screens 5 can be determined according to the thickness of the composite CVL3. For example, in the scenario of the present invention, when the adhesive layer 30 of the composite CVL3 is 25 microns, and the total thickness of the lower flexible dielectric material layer 31, the composite layer 32, and the upper flexible dielectric material layer 33 is 25 microns, The thickness of the screen 5 can be set to 30-35 microns. Since the height of the conductive material filled with the mesh 50 is increased during the upward lifting of the screen 5, the height of the conductive structure 4 formed by the conductive material is slightly higher than the thickness of the screen 5. Therefore, when the screen 5 is formed, the thickness of the screen 5 may be slightly smaller than the height of the composite CVL3 from the lower surface of the adhesive layer 30 to the lower surface or the upper surface of the composite layer 32 to ensure the height of the formed conductive structure 4. The adhesive layer 30 and the lower flexible dielectric material layer 31 of the composite CVL3 can pass through, and the conductive composite layer 32 communicates with the ground pad 200 on the surface of the flexible laminated structure 2 without exposing the upper surface of the composite CVL3. . When the conductive structure 4 is prepared by a spray coating method, as shown in FIG. 6, it is specifically:

600. Place the flexible laminate structure in a jet coater.

The double-sided FCCL2a bonded to the back CVL1 is taken out and fixed in a jet coater (or may be called a dispense device) so that the jet coater can optically align the double-sided FCCL2a.

601. A jet coater optically aligns a ground pad of the surface layer of the flexible laminated structure, and applies a conductive material to form a conductive material of the conductive structure corresponding to the ground pad.

The printing spot applicator searches for the feature points on the double-sided FCCL2a by optical alignment on the flexible laminated structure, and determines the position of the ground pad 200 according to the feature points, wherein the feature points are disposed on the double-sided FCCL2a And different from the shape of other structures on the double-sided FCCL2a, for example, may be a cross, a circle or a square; the nozzle of the jet applicator ejects the conductor material at a position corresponding to the ground pad 200.

602. The conductor material is tapered at a surface of the ground pad under the action of a jet coater.

By controlling the pressure and time when the conductor material is sprayed by the spot coating machine, the height and shape of the conductor material sprayed from the nozzle are adjusted, so that the conductive structure 4 formed by solidification of the conductor material is connected with the composite layer 32 in the composite CVL3. Generally, the spray The jetting machine has an ejection pressure of 0.7 MPa; under this pressure, the conductor material dropped on the ground pad 200 is tapered.

603. Curing the conductor material to form the conductive structure, wherein a height of the conductive structure is controlled by setting a pressure and time for spraying a conductor material by a jet coater.

Curing the tapered conductive material, because the conductive material is mixed with epoxy resin or acrylate, the conductive material can be cured by ultraviolet light curing or heating, and the conductive material is cured. Conductive structure 4. The height of the conductive structure can be set by setting the pressure and time at which the jet coater ejects the conductor material.

302, hot-pressing composite CVL on the surface of the flexible laminated structure, the composite CVL wrapping the conductive structure, the conductive structure passing through the adhesive layer of the composite CVL and the lower flexible dielectric material layer, and The composite layers of the composite CVL are in communication, and the set height is such that the conductive structure is not exposed on the upper surface of the composite CVL.

Alternatively, the set height can be set by setting the thickness of the screen of the printing press.

Alternatively, the set height may also be set by setting the pressure and time at which the jet coater ejects the conductor material. After curing to form the conductive structure 4, the lower end is covered with the back surface CVL1, and the double-sided FCCL2a and the composite CVL 3 provided with the conductive structure 4 on the ground pad 200 are stacked, wherein the adhesive layer 30 and the double of the composite CVL3 Face FCCL2a contact; after stacking, place The lower heating plate of the hot press; the upper heating plate is pressed with the lower heating plate, and maintains a certain pressure and temperature. Generally, the pressure is 120 kg, and the temperature can be between 50 and 150 degrees (including 50 degrees). And a temperature of 150 degrees), for example 130 degrees; a cured trapezoidal or pointed-conical structure 4, under which the adhesive layer 30 and the lower flexible dielectric layer of the composite CVL3 are pierced 31 is in contact with the composite layer 32 in the composite CVL3, the set height is such that the conductive structure 4 is not exposed on the upper surface of the composite CVL3, thereby forming a Faraday cage, so that the prepared FPC has an effect of shielding EMI. An FPC and a method for fabricating the same according to the embodiments of the present invention, by forming a conductive structure on a ground pad of an FPC, pressing a composite CVL by hot pressing on a surface layer of the flexible laminated structure, so that the composite CVL wraps the conductive structure And under a certain pressure, the conductive structure just pierces the adhesive layer of the composite CVL and the lower flexible dielectric material layer, and the electrically conductive composite layer and the ground pad of the surface of the flexible laminated structure are formed by the conductive structure Connected, EMI shielding, and by providing a conductive structure at a set height, the conductive structure is not exposed on the upper surface of the composite CVL, thereby effectively implementing FPC without adding an additional shielding layer on the surface of the FPC The shielding of EMI avoids the charge overflow and external erosion caused by the exposed structure of the conductive structure, enhances the shielding effect of FPC on EMI, and prolongs the service life of FPC. The above is only the specific embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily think of changes or substitutions within the technical scope of the present invention. It should be covered by the scope of the present invention. Therefore, the scope of the invention should be determined by the scope of the claims.

Claims

Rights request

1. A flexible printed circuit board comprising: a back cover film;

The back cover film is provided with a flexible laminated structure;

The flexible laminate structure includes a ground pad on a surface layer of the flexible laminate structure and a ground layer connected to the ground pad;

The method is characterized in that a conductive structure is disposed on the surface of the ground pad;

A composite cover film is further disposed on the surface layer of the flexible laminated structure, and the composite cover film comprises an adhesive layer, a lower flexible medium material layer and a composite layer which are sequentially disposed from bottom to top.

9 and upper flexible dielectric material layer,

The composite cover film encloses the conductive structure, and the conductive structure passes through the adhesive layer and the lower flexible dielectric material layer, communicates with the composite layer, and is not exposed to the composite cover film. Upper surface.

The flexible printed circuit board according to claim 1, wherein the conductive structure is formed by printing or by printing.

3. The flexible printed circuit board according to claim 2, wherein the conductive structure has a pointed shape.

4. The flexible printed circuit board according to claim 1, wherein the conductive structure is an epoxy resin or an acrylate, and a mixture of metal particles.

The flexible printed circuit board structure according to claim 4, wherein the metal particles are made of silver.

6. The flexible printed circuit board according to claim 1, wherein the upper flexible dielectric material layer and the lower flexible dielectric material layer are made of polyimide.

7. The flexible printed circuit board according to claim 1, wherein the composite layer is made of a composite material of polyimide and silver.

8. A method of fabricating a flexible printed circuit board, comprising: thermally pressing a back cover film under a flexible laminate structure;

Forming a conductive cover film on the surface layer of the flexible laminate structure, the composite cover film wrapping the conductive structure, the conductive structure passing through the adhesive layer and the lower flexible medium material layer of the composite cover film, And communicating with the composite layer of the composite cover film, the set height is such that the conductive structure is not exposed on the upper surface of the composite cover film.

9. Method according to claim 8, characterized in that the set height is set in particular by setting the thickness of the screen of the printing press.

10. The method of fabricating a flexible printed circuit board structure according to claim 8, wherein the set height is specifically set by setting a pressure and a time of spraying a conductor material by a jet coater. Said height.