CN114206008A

CN114206008A - Manufacturing method of thick copper flexible board and thick copper flexible board

Info

Publication number: CN114206008A
Application number: CN202111537955.7A
Authority: CN
Inventors: 丁克渝; 李冬兰; 张涛; 王文剑; 郭秀冬
Original assignee: Shenzhen Threetek Technology Co ltd
Current assignee: Shenzhen Threetek Technology Co ltd
Priority date: 2021-12-16
Filing date: 2021-12-16
Publication date: 2022-03-18

Abstract

The invention discloses a thick copper flexible plate and a manufacturing method thereof, wherein the thick copper flexible plate comprises the following manufacturing steps: providing a thick copper foil, and carrying out pattern processing to form a single-sided independent circuit thick copper flexible board; filling ink into the circuit gap of the thick copper flexible board with the single-sided independent circuit to form a flexible board to be attached; attaching a second covering film to the flexible board to be attached, performing rapid pressing treatment, and then performing laser trimming treatment on the second covering film to form a thick copper flexible board; by adopting the method, the thick copper flexible plate can be manufactured. Ink is filled between the thick copper independent circuits, and then the covering films are attached and pressed, so that the covering film attaching quality requirement and the appearance requirement of the thick copper circuit flexible board of the independent circuits can be effectively met, the ink and the covering films are compounds of high polymer materials, and the electrical property, the impedance property and the signal property of the flexible circuit board cannot be influenced.

Description

Manufacturing method of thick copper flexible board and thick copper flexible board

Technical Field

The invention relates to the field of circuit boards, in particular to a thick copper flexible board and a manufacturing method thereof.

Background

A Flexible Printed Circuit (FPC) also called a Flexible Printed Circuit board or a Flexible board; a printed circuit board is made of a polyimide or polyester film as a base material, and has high reliability and good flexibility. The high-density light-weight LED lamp has the characteristics of high wiring density, light weight, thin thickness and good bending property.

For some electronic application fields requiring large current transmission, a thick copper flexible board needs to be adopted to replace a connector.

Thick copper generally refers to the thickness of a copper layer circuit layer with the copper thickness larger than 105 μm, and the thick copper circuit manufacturing method is applied to realize the conductive performance of larger current, and is more and more common in flexible circuit boards.

Meanwhile, in order to simplify the application of the thick copper flexible board replacing the connector and make the current flow more independent, the design of the independent circuit flexible board appears.

Independent circuit flexible board, each circuit exists independently promptly, and relies on the cover film as the support basis, forms the flexible board of pure realization electricity connection.

The independent circuit flexible board needs to be installed in a connector base or a plug-in hole of a main board circuit board, so that a stronger plug circuit is generally needed, and therefore, the thick copper independent circuit flexible board is the most ideal design mode.

The flexible board is required to be attached with a covering film layer so as to meet the protection of the circuit layer and the flexibility of the circuit layer. When the thick copper independent circuit flexible board is attached to the covering film, the filling performance of the covering film (generally a polyimide film) is limited due to the fact that copper is thick, and therefore the covering film is difficult to fill gaps among thick copper circuits, the problem of poor attachment of the covering film is caused, a cavity below the covering film is formed, and product quality is affected.

At present, the gap filling between thick copper circuits is generally satisfied by increasing the thickness of the cover film and the thickness of the glue layer of the cover film and properly increasing the temperature and pressure for laminating the cover film. However, the method still cannot completely ensure that the cavity under the covering film is completely filled, and after the temperature and the pressure are increased, the expansion and shrinkage of the covering film are large, and after the thick copper circuit gap is filled, the concave-convex difference of the surface of the flexible board is large, so that the flexibility and the appearance of the flexible board are influenced.

Based on the above background, a manufacturing method capable of effectively meeting the requirement of laminating a thick copper independent circuit flexible board cover film is needed.

Disclosure of Invention

The invention mainly aims to provide a manufacturing method of a thick copper flexible board, and aims to solve the problem that the existing thick copper flexible board of an independent circuit is poor in glue filling or covers a cavity under a film.

In order to achieve the above object, the present invention provides a method for manufacturing a thick copper flexible board, including:

s10: providing a thick copper foil, and carrying out pattern processing to form a single-sided independent circuit thick copper flexible board;

s20: filling ink into the circuit gap of the single-sided independent circuit thick copper flexible board to form a flexible board to be attached;

s30: and attaching a second covering film to the flexible board to be attached, performing rapid pressing treatment, and performing laser trimming treatment on the second covering film to form the thick copper flexible board.

Further, the step of providing a thick copper foil and performing patterning to form the single-sided independent circuit thick copper flexible board is as follows:

s110: taking a thick copper foil;

s120: and sequentially attaching a first covering film to the thick copper foil, attaching a dry film on two sides, exposing, developing and etching to form the single-side independent circuit thick copper flexible board.

Furthermore, circuit notches are distributed on two sides of the independent circuit in the coverage range of the first cover film, and the circuit notches are formed through the graphic processing.

Further, the processing of filling ink in the circuit gap of the single-sided independent circuit thick copper flexible board to form the flexible board to be attached is as follows:

silk-screen printing is carried out on the ink filling area in a silk-screen printing mode;

the ink filling area is a line gap of the independent line and is distributed in one side area of the independent line on the edge of the single-side independent line thick copper flexible plate;

the coverage of the ink filling area is smaller than that of the first covering film layer.

Further, the printing ink is yellow printing ink, the viscosity of the printing ink is 70 dpa.s-100 dpa.s, the silk-screen printing is performed twice, and the manufacturing steps of the silk-screen printing twice are as follows:

s310: carrying out first silk screen printing;

s320: baking for the first time at 75 ℃ for 35min to 45 min;

s330: performing second silk-screen printing;

s340: and (3) carrying out secondary baking at 75 ℃ for 45-50 min.

Further, the ink is yellow ink, the viscosity of the ink is 130 dpa.s-170 dpa.s, and the silk-screen printing is single-time silk-screen printing.

Further, the silk-screen printing is carried out by adopting an aluminum sheet as a silk-screen printing tool;

windowing areas are distributed on the aluminum sheet;

the windowing area corresponds to the ink filling area;

the length and the width of the windowing region are respectively 20-50 mu m smaller than the length and the width of the ink area to be filled.

Furthermore, the windowing region is provided with a connecting bridge, and the connecting bridge divides the windowing region into a plurality of sub windowing regions.

Further, the ink is a compound system ink formed by mixing an ink main agent, an ink auxiliary agent and glue;

the blending mode of the compound system ink is as follows:

mixing the ink main agent and the glue in a volume ratio of 7:3 to 9:1, and uniformly stirring to form a first compound system;

slowly adding the ink auxiliary agent into the first compound system, and uniformly stirring to form the compound system ink;

the glue is acrylic glue or epoxy resin glue.

In order to achieve the above object, the present invention provides a thick copper flexible board, which is manufactured by any one of the above manufacturing methods.

According to the technical scheme, the gaps among the thick copper circuits are filled with the ink, and then the cover films are attached and pressed, so that the requirement on the attachment quality and the appearance of the cover film of the thick copper circuit flexible board of the independent circuit can be effectively met.

Drawings

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

FIG. 1 is a schematic process flow diagram of a method for manufacturing a thick copper flexible board according to the present invention;

FIG. 2 is a schematic plane structure diagram of a first cover film pasted with a thick copper foil and a dry film pasted with a thick copper foil according to the method for manufacturing a thick copper flexible board of the present invention;

FIG. 3 is a schematic view of the cross-sectional structure A-A of FIG. 2;

FIG. 4 is a schematic structural diagram of a pattern process of a method for manufacturing a thick copper flexible board according to the present invention;

FIG. 5 is a schematic diagram of a planar structure of a thick copper flexible board with a single-sided independent circuit according to the method for manufacturing the thick copper flexible board of the present invention;

FIG. 6 is a schematic view of the cross-sectional structure B-B of FIG. 5;

FIG. 7 is a schematic diagram of a planar structure of an independent circuit notch of a method for manufacturing a thick copper flexible board according to the present invention;

FIG. 8 is a schematic view of the cross-sectional structure C-C of FIG. 7;

FIG. 9 is a schematic view of a filling ink process of a method for manufacturing a thick copper flexible board according to the present invention;

FIG. 10 is a schematic view of the cross-sectional structure of FIG. 9 taken along line D-D;

FIG. 11 is a schematic plane structure diagram of a thick copper flexible board manufacturing method according to the present invention, in which an aluminum sheet is used as a screen printing tool for processing;

FIG. 12 is a schematic view of the cross-sectional structure E-E of FIG. 11;

fig. 13 is a schematic structural view of attaching a second cover film to a to-be-attached flexible board according to a method for manufacturing a thick copper flexible board of the present invention.

The reference numbers illustrate:

reference numerals	Name (R)	Reference numerals	Name (R)
				100	Thick copper flexible board	1510	Ink filled zone
110	Thick copper foil	160	Second cover film
				120	Dry film	170	Aluminium sheet
130	Independent line	1710	Area of window opening
				1310	Gap	1710A	Connecting bridge
140	First cover film	200	Thick copper flexible board of single-sided independent circuit
				150	Printing ink	300	To-be-bonded flexible board

The implementation, functional features and advantages of the objects of the present invention will be further explained with reference to the accompanying drawings.

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.

It should be noted that all the directional indicators (such as up, down, left, right, front, and rear … …) in the embodiment of the present invention are only used to explain the relative position relationship between the components, the movement situation, etc. in a specific posture (as shown in the drawing), and if the specific posture is changed, the directional indicator is changed accordingly.

In addition, the descriptions related to "first", "second", etc. in the present invention are only for descriptive purposes and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "a plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.

In the present invention, unless otherwise expressly stated or limited, the terms "connected," "secured," and the like are to be construed broadly, and for example, "secured" may be a fixed connection, a removable connection, or an integral part; can be mechanically or electrically connected; they may be directly connected or indirectly connected through intervening media, or they may be connected internally or in any other suitable relationship, unless expressly stated otherwise. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.

In addition, the technical solutions in the embodiments of the present invention may be combined with each other, but it must be based on the realization of those skilled in the art, and when the technical solutions are contradictory or cannot be realized, such a combination of technical solutions should not be considered to exist, and is not within the protection scope of the present invention.

Referring to fig. 1 to 6, fig. 1 is a schematic process flow diagram of a method for manufacturing a thick copper flexible board according to the present invention, and fig. 2 to 6 are schematic structural diagrams of an independent circuit thick copper flexible board 200 manufactured according to the process of step S10 in fig. 1.

The manufacturing method comprises the following steps:

step S10: a thick copper foil 110 is provided and patterned to form a thick copper flexible board 200 having a single-sided independent circuit.

In the processing technology in the prior art, a base plate for manufacturing a flexible circuit board is a flexible copper clad laminate, namely, a copper foil covers a flexible plate dielectric layer to form the copper clad laminate; and then, carrying out pattern processing and other manufacturing by using the copper-clad plate to finally form the flexible plate. Because the copper layer circuit that needs to process in this embodiment is thick copper circuit (being greater than 105 μm), on the one hand there is very few thick copper-clad plate > 105 μm, and the preparation material is difficult to satisfy the demand, and on the other hand, the flexbile plate form that this embodiment needs to obtain is the structure that the cover film adds the copper layer (and not the traditional structure that copper layer circuit adds the flexbile plate dielectric layer), consequently, need adopt earlier the mode of making the circuit figure, and the cover film is laminated and is processed.

In view of the above background, in the present embodiment, it is first necessary to fabricate the single-sided independent circuit thick copper flexible board 200. Referring to fig. 2 and 3, fig. 2 is a schematic plan view of a first cover film pasted with thick copper foil and a dry film pasted with thick copper foil according to a method for manufacturing a thick copper flexible board of the present invention; fig. 3 is a schematic cross-sectional view of a-a of fig. 2, that is, a schematic cross-sectional view of a thick copper foil first cover film and a thick copper foil dry film. As shown in fig. 2 and 3, first, a thick copper foil 110 is taken (step S110), a first cover film 140 is sequentially attached to the thick copper foil, and a dry film 120 is attached to both surfaces of the thick copper foil (step S120); referring to fig. 4, fig. 5 and fig. 6, fig. 4 is a schematic structural diagram of a pattern process of a method for manufacturing a thick copper flexible board according to the present invention; FIG. 5 is a schematic diagram of a planar structure of a thick copper flexible board with a single-sided independent circuit according to the method for manufacturing the thick copper flexible board of the present invention; fig. 6 is a schematic cross-sectional structure view of B-B in fig. 5, that is, a schematic cross-sectional structure view of a single-sided independent circuit thick copper flexible board. After the above process, the flexible board to be processed with the dry film 120 attached on both sides is exposed, developed, and etched to form the thick copper flexible board 200 with the single-sided independent circuit (step S120).

It should be noted that, the first cover film 140 is attached to the thick copper foil 110, and the cover film is attached according to a pattern area required to be attached instead of being attached to the whole surface of the thick copper foil 110, so that the thick copper foil 110 is supported, and a board foundation for effectively preventing the circuit from scattering is provided for the subsequent processing of the independent circuit 130. The double-sided adhesive dry film can be effectively attached to the cover film, and whether the drop gap is filled can be determined, so that a pattern transfer basis for processing the thick copper foil 110 circuit is formed.

Referring to fig. 7 and 8, fig. 7 is a schematic plan view illustrating an independent circuit notch of a method for manufacturing a thick copper flexible board according to the present invention; fig. 8 is a schematic cross-sectional view of the cross-sectional structure C-C of fig. 7, i.e., a schematic cross-sectional structure of the isolated line notch. In this embodiment, the patterned single-sided independent circuit thick copper flexible board 200 forms the independent circuit 130 with the notches 1310 distributed on two sides of the independent circuit 130, and the distribution areas of the notches 1310 are within the coverage area of the first cover film 140; the notch 1310 is formed in the independent circuit 130, so that the ink 150 has more filling space during subsequent filling of the ink 150, and the ink 150 can form a better fixing effect with the independent circuit 130 after being cured, thereby preventing the independent circuit 130 from being separated from the ink 150. The gaps 1310 are generally arc-shaped gaps, and may be gaps with other shapes such as rectangular, square, etc., and the gaps are generally uniformly distributed.

Step S20: and filling ink 150 into the circuit gap of the single-sided independent circuit thick copper flexible board 200 to form a flexible board 300 to be attached.

Referring to fig. 9 and 10, fig. 9 is a schematic view illustrating a processing of filling ink in a method for manufacturing a thick copper flexible board according to the present invention; FIG. 10 is a schematic cross-sectional view of the cross-sectional view D-D of FIG. 9, i.e., a schematic cross-sectional view of a ink-plugging process. Based on single face independent circuit thick copper flexboard 200, because the clearance between the independent circuit of thick copper is great, darker, if directly attached the second cover film, the filling ability of cover film is not enough, produce the hole easily, layering scheduling problem, consequently, fill printing ink 150 to the circuit clearance of the independent circuit thick copper flexboard 200 of single face, utilize printing ink 150 to fill the circuit clearance, and utilize printing ink 150's adhesion, can provide comparatively level and smooth face condition for attaching the cover film on the one hand, on the other hand can provide effectual adhesion basic material layer for covering the rete, prevent the attached hole of cover film, layering scheduling problem.

In this embodiment, fill printing ink 150, adopt the mode of silk screen printing to process, the silk screen printing can accurate positioning to the region that needs fill printing ink 150 to can fill volume, fill effects such as thickness, homogeneity according to different printing ink control.

Please refer to fig. 9 and 10 again; the area of the ink filling 150 is distributed in the line gap of the independent line 130 and on one side of the independent line 130 at the edge to form an ink filling region 1510, in this embodiment, the ink filling region 1510 includes a portion of the independent line 130, that is, a portion of the ink 150 covers the surface of the independent line 130, generally, the width of the ink 150 covering the surface of the independent line 130 is 10 μm to 20 μm, which is beneficial to the tight and firm bonding between the ink 150 and the second cover film 160 during the subsequent attachment of the second cover film 160.

Referring to fig. 11 and 12, fig. 11 is a schematic plan structure diagram of a thick copper flexible board manufacturing method according to the present invention, in which an aluminum sheet is used as a screen printing tool for processing; FIG. 12 is a schematic view of the cross-sectional structure of E-E of FIG. 11, that is, a schematic view of a cross-sectional structure processed by using an aluminum sheet as a silk-screen tool; because the silk screen printing needs to use the silk screen printing instrument, in this embodiment, adopt aluminum sheet 170 to process as the silk screen printing instrument, it has windowing area 1710 to distribute on the aluminum sheet 170, be used for the silk screen printing to leak down printing ink, windowing area 1710 corresponds and packs printing ink district 1510, and the length and the width of windowing area 1710 are less than respectively and packs printing ink district 1510's length and width 20 mu m to 50 mu m, because aluminum sheet 170 silk screen printing time, windowing area 1710's windowing figure is great relatively, the oil mass is great when silk screen printing, consequently, it suitably reduces windowing area 1710's length and width to pack printing ink district 1510 relatively, prevent the too much diffusion of printing ink, cause the circuit to go up too much, or face pollution scheduling problem.

Referring to fig. 11 again, in this embodiment, the windowing region 1710 is provided with a connecting bridge 1710A, the connecting bridge 1710A is a "partition" disposed in the windowing region 1710, the connecting bridges 1710A are uniformly distributed in the windowing region 1710, the longitudinal direction of the connecting bridge 1710A is consistent with the direction in which the screen printing scraper advances, the windowing region 1710 is divided into a plurality of sub windowing regions by the connecting bridge 1710A, the area of the windowing region 1710 can be effectively reduced by the connecting bridge 1710A, and during the screen printing process, the problem that the edge of the windowing region 1710 is directly scraped by the screen printing scraper, which causes tearing of the windowing region 1710 and the like can be prevented; the width of the connecting bridge 1710A may be set to 0.5mm to 2.0 mm.

In this embodiment, the ink 150 is a yellow ink, and since the cover film is made of a polyimide material and the polyimide material is yellow or yellowish brown, the ink 150 is made of the yellow ink, and can match the color of the polyimide material, so that the problem of color difference or heterochrosis of the thick copper flexible board 100 is avoided; the viscosity of the ink 150 is 70 to 100 dpa.s.

In this embodiment, the number of silk-screen printing times is optionally two, and the two-time silk-screen printing manufacturing steps are as follows:

s310: carrying out first silk screen printing;

s320: baking for the first time at 75 ℃ for 35min to 45 min;

s330: performing second silk-screen printing;

s340: and (3) carrying out secondary baking at 75 ℃ for 45-50 min.

Adopt twice silk screen printing, the printing ink viscosity that twice silk screen printing adopted is lower, can effectively alleviate the printing ink bubble that silk screen printing ink is too thick and produce, and the problem that surface cure is too abundant and the internal cure is not enough during the printing ink solidification, and twice silk screen printing adopts low temperature and short time to toast, form the effect of incompletely toasting, the printing ink of first silk screen printing toasts twice, can effectively combine with first cover membrane 140, and the printing ink of second silk screen printing only toasts once, can effectively combine with the printing ink of first silk screen printing, and leave sufficient adhesion performance for attached second cover membrane 160.

In one embodiment, the ink 150 with higher viscosity is 130dpa.s to 170dpa.s, and the requirement of filling ink can be met by adopting a single-time silk-screen printing mode.

In this embodiment, the ink 150 is filled with an ink containing glue, the ink 150 is a compound system ink formed by mixing an ink main agent, an ink auxiliary agent and glue, and the mixing manner is as follows: mixing the ink main agent and the glue in a volume ratio of 7:3 to 9:1, and uniformly stirring to form a first compound system; slowly adding an ink auxiliary agent into the first compound system, and uniformly stirring to form compound system ink; the glue is acrylic acid glue or epoxy resin glue; adding a proper amount of acrylic acid glue or epoxy resin glue into the printing ink can effectively improve the adhesion performance of the printing ink, the covering film and the independent line, and prevent the problems of falling off, peeling off and the like of the printing ink layer.

Fig. 13 is a schematic structural diagram of a second cover film attached to a flexible board to be attached according to a method for manufacturing a thick copper flexible board of the present invention.

Step S30: and attaching a second cover film 160 to the flexible board to be attached, performing rapid pressing treatment, and performing laser trimming treatment on the second cover film 160 to form the thick copper flexible board 100.

After the ink is filled, a second cover film 160 is attached to the flexible board to be processed, the flexible board to be processed is pressed in a rapid pressing mode after the ink is filled, so that the flexible board to be processed is firmly attached, then laser trimming is adopted, and the cover film and the glue overflow area are trimmed to form the thick copper flexible board 100.

In this embodiment, by using the above manufacturing method, a thick copper flexible board can be obtained.

In this embodiment, make the flexbile plate basis for filling printing ink through making the independent circuit thick copper flexbile plate of single face, fill the too big, too deep region in thick copper circuit line space through filling printing ink, make the basis for making whole thick copper flexbile plate, whole preparation mode has effectively improved the attached reliability of thick copper flexbile plate cover membrane.

The above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention, and all modifications and equivalents of the present invention, which are made by the contents of the present specification and the accompanying drawings, or directly/indirectly applied to other related technical fields, are included in the scope of the present invention.

Claims

1. A manufacturing method of a thick copper flexible plate is characterized by comprising the following steps:

2. The method for manufacturing a thick copper flexible board according to claim 1, wherein the step of providing a thick copper foil and performing patterning to form the single-sided independent circuit thick copper flexible board comprises:

s110: taking a thick copper foil;

3. The method for manufacturing a thick copper flexible board according to claim 2, wherein circuit notches are distributed on two sides of the independent circuit within the coverage range of the first cover film, and the circuit notches are formed by the graphic processing.

4. The method for manufacturing the thick copper flexible board according to claim 3, wherein the step of filling the circuit gaps of the single-sided independent circuit thick copper flexible board with ink to form the flexible board to be attached comprises:

5. The method for manufacturing a thick copper flexible board as claimed in claim 4, wherein the ink is yellow ink, the viscosity of the ink is 70dpa.s to 100dpa.s, the silk-screen printing is performed twice, and the steps of the silk-screen printing twice are as follows:

s310: carrying out first silk screen printing;

s320: baking for the first time at 75 ℃ for 35min to 45 min;

s330: performing second silk-screen printing;

s340: and (3) carrying out secondary baking at 75 ℃ for 45-50 min.

6. The method of claim 4, wherein the ink is yellow ink, the viscosity of the ink is 130dpa.s to 170dpa.s, and the silk-screen printing is single-pass silk-screen printing.

7. The method for manufacturing the thick copper flexible board as claimed in claim 4, wherein the silk-screen printing is performed by using an aluminum sheet as a silk-screen printing tool;

windowing areas are distributed on the aluminum sheet;

the windowing area corresponds to the ink filling area;

8. The method according to claim 7, wherein the window area is provided with a connecting bridge, and the connecting bridge divides the window area into a plurality of sub-window areas.

9. The method for manufacturing the thick copper flexible board according to claim 4, wherein the ink is a compound system ink formed by mixing an ink main agent, an ink auxiliary agent and glue;

the blending mode of the compound system ink is as follows:

the glue is acrylic glue or epoxy resin glue.

10. A thick copper flexible board, characterized in that it is manufactured by the manufacturing method of any one of claims 1 to 9.