CN211509416U

CN211509416U - Multilayer flexible circuit board with partially exposed inner layer

Info

Publication number: CN211509416U
Application number: CN202020165072.2U
Authority: CN
Inventors: 杨贤伟; 叶华; 谢鸿坚
Original assignee: Fujian Shizhuo Electronic Technology Co ltd
Current assignee: Fujian Shizhuo Electronic Technology Co ltd
Priority date: 2020-02-12
Filing date: 2020-02-12
Publication date: 2020-09-15
Anticipated expiration: 2030-02-12

Abstract

The utility model provides a local naked multilayer flexible line way board of inlayer, its characterized in that: the copper clad laminate comprises a PI substrate, a double-sided copper clad laminate consisting of an upper double-sided copper foil and a lower double-sided copper foil, wherein the upper single-sided copper clad laminate consisting of the PI substrate and the copper foil is bonded on the upper copper foil through hot-pressing glue; the through hole of the upper and lower double-sided copper foils of the communicated double-sided copper-clad plate is a through hole, and the through hole of the upper and lower double-sided copper foils of the communicated double-sided copper-clad plate, the copper foil of the upper single-sided copper-clad plate and the copper foil of the lower single-sided copper-clad plate are through holes; the inner layer part circuit, the inner layer part PI base material, the outer layer part PI base material, the inner layer welding pad and the fingers are exposed. The utility model discloses reach the purpose that compromises circuit and bending property or bending property needs simultaneously.

Description

Multilayer flexible circuit board with partially exposed inner layer

Technical Field

The utility model relates to a flexible line way board, specifically speaking one kind is the local naked multilayer flexible line way board of inlayer.

Background

The multilayer flexible circuit board has thicker thickness and poorer flexibility, and the flexibility and the bending property of the multilayer flexible circuit board are not as good as those of a single-sided flexible circuit board and a double-sided flexible circuit board, and some electronic products need certain parts with good flexibility and are convenient to bend or bend, such as mobile phone mainboards, screens, sensors, micro motors, robot steering systems, printing ports and other parts needing bending or bending. However, because the electronic products need to be designed as multi-layer boards, which affect the flexibility or bending property, a method needs to be found in the contradiction, which is the purpose of satisfying both the flexibility and bending property of the circuit.

SUMMERY OF THE UTILITY MODEL

The utility model provides a local naked multilayer flexible line way board of inlayer, its purpose is solved prior art's shortcoming, reaches the purpose that compromises circuit and bending property or nature of buckling and needs simultaneously.

The utility model provides a technical scheme that its technical problem adopted is:

the utility model provides a local naked multilayer flexible line way board of inlayer which characterized in that:

the copper clad laminate comprises a PI substrate, a double-sided copper clad laminate consisting of an upper double-sided copper foil and a lower double-sided copper foil, wherein the upper single-sided copper clad laminate consisting of the PI substrate and the copper foil is bonded on the upper copper foil through hot-pressing glue; the through hole of the upper and lower double-sided copper foils of the communicated double-sided copper-clad plate is a through hole, and the through hole of the upper and lower double-sided copper foils of the communicated double-sided copper-clad plate, the copper foil of the upper single-sided copper-clad plate and the copper foil of the lower single-sided copper-clad plate are through holes; the inner layer part circuit, the inner layer part PI base material, the outer layer part PI base material, the inner layer welding pad and the fingers are exposed.

The utility model discloses an useful part lies in:

the utility model discloses outer substrate and circuit about the position that multilayer flexible circuit board can be crooked or buckle in some needs does not have, only exposes the single face or the two-sided part of inlayer, makes this position thickness attenuation, is convenient for crooked or buckle, and other positions still are the multiply wood, reach the purpose of compromise circuit and bending nature or nature of buckling needs simultaneously. The utility model discloses the pad or the golden finger of inlayer also can be exposed simultaneously.

Drawings

The present invention will be further explained with reference to the drawings and examples.

Fig. 1 is a laminated structure diagram of the present invention.

Detailed Description

In order to more clearly illustrate the technical solution of the present invention, the drawings used in the description will be briefly introduced, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other embodiments can be obtained according to the drawings without inventive labor.

The embodiment is a 4-layer flexible circuit board applied between a 5G mobile phone mainboard and a display screen, one end of the flexible circuit board is exposed out of an inner-layer PI part which is easy to bend, and a golden finger at the tail end of the part is connected with the mainboard through the other end of the golden finger after being in compression joint with the screen.

As shown in fig. 1:

the utility model relates to a local naked multilayer flexible line way board in inside, including the two-sided copper-clad plate that PI substrate 1 and copper foil 2, copper foil 3 are constituteed, glue 4 bonds with the hot pressing on the copper foil 2 and have the single face copper-clad plate that PI substrate 7 and copper foil 9 are constituteed, have on the copper foil 9 to cover membrane 10, glue 6 bonds with the hot pressing on the copper foil 3 and have the single face copper-clad plate that PI substrate 12 and copper foil 13 are constituteed, have on the copper foil 13 to cover membrane 14.

The through hole 15 with the communicated

copper foils

2 and 3 is a through hole, and the through hole 16 with the communicated

copper foils

9, 2, 3 and 13 is a through hole.

The inner layer part line 21, the inner layer part PI base material 111, the outer layer part PI base material 71, the pad 8 and the finger 11 of the inner layer, and the finger 22 and the finger 5 corresponding to the inner layer part line 21 are exposed.

The PI substrate 12 is exposed at a portion corresponding to the finger 5.

The process for producing the flexible circuit board comprises the following steps:

the method comprises the following steps of:

taking a 4-layer flexible circuit board as an example, the bent or bent part and the part requiring the exposed pad of the inner-layer circuit or finger are determined according to the requirement of the product, and the parts requiring the outer-layer abdication are avoided when the outer-layer circuit is designed. Meanwhile, the inner layer and the outer layer are provided with alignment positioning holes with the same hole position and hole diameter. And then determining the number and the size of typesetting, photoplotting each layer of film, making a drilling file and a die drawing.

The material composition is as follows: the inner layer material is a double-sided copper clad laminate composed of a polyimide film (PI for short) adhesive-free PI base material 1, a copper foil 2 and a copper foil 3. The upper outer layer material is a single-sided copper clad laminate consisting of a polyimide film (PI for short) adhesive-free PI base material 7 and a copper foil 9, the lower outer layer material is a single-sided copper clad laminate consisting of a polyimide film (PI for short) adhesive-free PI base material 12 and a copper foil 13, and the inner layer and the outer layer are laminated and bonded through hot-pressing adhesives 4 and 6. Two

cover films

10 and 14 are arranged on the upper and lower sides.

Preparing an inner-layer double-sided circuit:

cutting a double-sided copper clad laminate composed of a PI substrate 1, a copper foil 2 and a copper foil 3 according to the required size, drilling a through hole 15 communicated with the copper foil 2 and the copper foil 3 as a through hole by numerical control drilling or laser drilling, metalizing the through hole 15 by black holes and copper plating procedures, pasting dry films on two sides, exposing, developing, etching and stripping inner-layer circuits to form a double-sided circuit or an inner-layer plate semi-finished product with a part of the double-sided circuit and a part of one side of the inner-layer circuit as a single-sided circuit and a pad 8 and a finger 11.

Manufacturing the upper outer layer and the lower outer layer:

the upper outer layer adopts a single-sided copper clad laminate consisting of a PI non-adhesive base material 7 and a copper foil 9 and a semi-cured hot-pressing adhesive 4, the lower outer layer adopts a single-sided copper clad laminate consisting of a PI non-adhesive base material 12 and a copper foil 13 and a semi-cured hot-pressing adhesive 6, the two materials are cut into required sizes, the PI surface of the single-sided copper clad laminate is attached to the hot-pressing adhesive and is subjected to over-molding, and then numerical control drilling or laser drilling is carried out to drill out required positioning holes. Then, according to the design requirement, a die or a laser machine is used for windowing, and parts needing inner layer exposure, such as the inner layer part circuit 21, the bonding pad 8, the finger 5, the inner layer part PI base material 111, the finger 11 and the like, are punched or cut out, wherein the parts can be in a circular shape, a square shape, a long strip shape or other special shapes, and an outer layer semi-finished product for windowing and abdicating at a specified position is formed.

The inner layer and the outer layer are combined:

with step three outer well semi-manufactured goods of stepping down about, with step two well semi-manufactured goods of inlayer etching, adopt the tool to counterpoint according to the locating hole to with the flat head electric iron heat all around and scald pre-fixing, then carry out the pressfitting with the laminator, the pressfitting parameter is: the temperature is 180 ℃, the pressure is 120kg, the time is 100 seconds, and then the mixture is baked for 60 minutes in an oven at 160 ℃. A semi-finished four-layer board with a circuit on the inner layer, a copper-clad surface on the outer layer and a window on a specified position is formed, and the inner layer part circuit 21, the bonding pad 8, the finger 5, the inner layer part PI base material 111 and the finger 11 are visible.

Fifthly, carrying out numerical control drilling or laser drilling:

and fourthly, performing numerical control drilling or laser drilling on the combined semi-finished four-layer board to form through holes 16 communicated with the copper foil 9, the copper foil 2, the copper foil 3 and the copper foil 13 as through holes according to the designed aperture and hole position.

Sixthly, surface processing:

and fifthly, carrying out plasma and surface treatment on the plate with the drilled holes, and removing the glue residue in the holes and the oxide on the plate surface.

Plating-resistant adhesive tapes are attached to the exposed portions of the inner sides of the sides:

pasting an electroplating-resistant adhesive tape on the plate processed in the step sixteenth by using the exposed inner layer of the electroplating-resistant adhesive, and then performing plastic coating to firmly adhere the electroplating-resistant adhesive tape so as to protect the inner layer from adsorbing carbon powder when black holes are formed.

Black hole treatment:

and (4) carrying out black hole treatment on the plate protected by the inner layer of the step-quieting, and tearing off the electroplating-resistant adhesive tape, so that the plate surface without the electroplating-resistant adhesive tape and the via hole adsorb a layer of carbon powder and are conductive. And the part of the anti-electroplating adhesive tape is torn off without carbon powder, so that the anti-electroplating adhesive tape is not conductive.

Self-skin inner layer circuit pad and finger protection:

because some exposed parts of the inner layer are the bonding pads and the fingers, some of the bonding pads and the fingers are communicated with the outer layer, and some of the bonding pads and the fingers are not communicated, if the bonding pads and the fingers are not protected, a layer of copper is plated when the bonding pads and the fingers are communicated with the outer layer during copper plating, the bonding pads and the fingers are thicker and brighter, and the bonding pads and the fingers are not communicated with the outer layer, so that the bonding pads and the fingers are thinner and darker, and the. Therefore, precise protection of the pads and fingers is necessary.

And tearing off the plate of the electroplating-resistant adhesive tape from the black hole, cleaning, pasting photosensitive dry films on two sides, aligning and exposing by using an inner-layer protection film, covering and protecting windowing parts such as an inner-layer PI or an inner-layer bonding pad and a copper foil of fingers by the dry films after developing, and exposing parts of the through hole and the outer layer needing copper plating.

The method comprises the following steps of copper electroplating:

and (3) plating copper on the inner-layer circuit bonding pad and the finger-protected plate in the step, wherein the part without the protection of the dry film in the electroplating process has adsorbed carbon powder which can be conductive, the plate surface and the hole are plated with a layer of copper, and the part protected by the dry film can not be conductive and is not plated with copper. The exposed portions of the inner layer are not plated with copper.

Leaving the inner layer exposed by the withdrawn film:

and (4) carrying out film removing treatment on the board plated with copper, and removing the protective dry film to expose the inner layer. And forming a multi-layer plate semi-finished product with the inner layer partially exposed, the outer layer and the through holes plated with copper.

Manufacturing a water-absorption outer layer circuit:

the plate after the copper plating and film removing is subjected to photo-sensitive dry film pasting and outer layer circuit film alignment, after exposure, development, etching and film removing, a semi-finished four-layer plate with an inner layer copper foil 2, an inner layer circuit on the copper foil, an upper outer layer copper foil 9 and a lower outer layer copper foil 13 with outer layer circuits is formed, and meanwhile, the inner layer part circuit 21, the inner layer part PI base material 111 and the outer layer part PI base material 71, a bonding pad 8 and a finger 11 on the inner layer, and fingers 22 and fingers 5 (namely head and tail fingers) corresponding to the inner layer part circuit 21 are exposed on a required part of the semi-finished product. At this time, the end composed of the inner layer portion PI base material 11, the finger 22, the hot-press adhesive 4, and the outer layer portion PI base material 71 is the thinnest and is easy to bend or bend, and the portion can be pressed against the screen of the mobile phone.

In addition, according to the design requirements of the upper layer or the lower layer, some other side exposed out of the PI substrate of the inner layer cannot have a circuit, and the copper foil at the position needs to be etched. The thermocompression bonding paste 6 and the PI substrate 12 on the outer layer without the wiring portion serve as an insulating layer for the inner layer and the outer layer and also as a protective film for the wiring on the inner layer. When the outer cover film is pasted, the cover film at the position is only required to be windowed, at the moment, the other end is composed of a PI base material 1, a copper foil 3, a finger 5, a hot-pressing adhesive 6 and a PI base material 12, and the position can be connected with a mobile phone mainboard in an inserting mode.

The selection paste covers the upper and lower layers:

surface cleaning treatment is carried out on the semi-finished product with the inner layer and the upper and lower outer layer circuits which is manufactured by the steps, then the windowed covering film 10 and the windowed covering film 14 are aligned with the semi-finished product by a jig, and hot pressing, baking and curing are carried out.

Self-absorption electroless nickel gold plating:

performing chemical nickel gold plating on the board after the step of selecting the core and curing to plate a nickel layer with a specified thickness on the gold finger and the bonding pad;

processing of the subsequent conventional process:

and (3) attaching a shielding film, reinforcing and the like to the nickel-gold plated plate, and then performing procedures such as electrical measurement, shape punching and the like.

The utility model discloses a production technology of multilayer flexible line way board that the inlayer is naked, its characterized in that: the method comprises the following steps: structural design; manufacturing an inner layer double-sided circuit; manufacturing an upper outer layer and a lower outer layer; combining an inner layer and an outer layer; numerical control drilling or laser drilling; surface treatment; sticking an anti-electroplating adhesive tape on the exposed part of the inner layer; black hole treatment; inner layer circuit pad and finger protection; electroplating copper; removing the film to expose the inner layer; manufacturing an outer layer circuit; pasting a lower cover film; chemically plating nickel and gold; and (5) processing by subsequent conventional procedures.

The utility model discloses outer substrate and circuit about some position that need bend or buckle can be not had to the multiply wood, only exposes the single face or the two-sided part of inlayer, makes this position thickness attenuation, is convenient for bend or buckle, and other positions still are the multiply wood. The purpose of simultaneously considering the circuit and the flexibility or the bending property is achieved. The utility model discloses the pad or the golden finger of inlayer also can be exposed simultaneously.

The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other. The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. The utility model provides a local naked multilayer flexible line way board of inlayer which characterized in that: the copper clad laminate comprises a PI substrate, a double-sided copper clad laminate consisting of an upper double-sided copper foil and a lower double-sided copper foil, wherein the upper single-sided copper clad laminate consisting of the PI substrate and the copper foil is bonded on the upper copper foil through hot-pressing glue;

the through hole of the upper and lower double-sided copper foils of the communicated double-sided copper-clad plate is a through hole, and the through hole of the upper and lower double-sided copper foils of the communicated double-sided copper-clad plate, the copper foil of the upper single-sided copper-clad plate and the copper foil of the lower single-sided copper-clad plate are through holes;

the inner layer part circuit, the inner layer part PI base material, the outer layer part PI base material, the inner layer welding pad and the fingers are exposed.