CN111225497B

CN111225497B - Local ultrathin hollowed double-layer FPC product and manufacturing method thereof

Info

Publication number: CN111225497B
Application number: CN202010138370.7A
Authority: CN
Inventors: 曹先贵; 袁林辉; 邹锋
Original assignee: Suiwa High Technology Electronic Industries Xiamen Co ltd; Shenzhen Mindray Bio Medical Electronics Co Ltd
Current assignee: Suiwa High Technology Electronic Industries Xiamen Co ltd; Shenzhen Mindray Bio Medical Electronics Co Ltd
Priority date: 2020-03-03
Filing date: 2020-03-03
Publication date: 2021-03-02
Anticipated expiration: 2040-03-03
Also published as: CN111225497A

Abstract

The invention relates to a local ultrathin hollowed double-layer FPC product and a manufacturing method thereof. According to the invention, the thin double-layer copper is adopted to separately process the electro-coppering twice, the first local electro-coppering is used for completing PTH hole connection in a non-key area, the second local electro-coppering is used for thickening the copper thickness of the hollow finger area, and CVLs with different thicknesses are pressed on the key area and the non-key area twice, so that the CVLs of the product are not layered and the key area is ultrathin, and the thickness requirement of the medical ultrasonic probe is further met.

Description

Local ultrathin hollowed double-layer FPC product and manufacturing method thereof

Technical Field

The invention relates to the field of flexible circuit board manufacturing processes, in particular to a local ultrathin hollowed double-layer FPC product and a manufacturing method thereof.

Background

The flexible printed circuit board is a flexible printed circuit board with high reliability and excellent performance, which is made of polyimide or polyester film as base material. The method has the characteristics of high wiring density, light weight and thin thickness. In the art, FPC products having copper thickness of 10 micrometers or less and total thickness of 50 micrometers or less are referred to as ultra-thin FPC products. The typical ultrathin FPC product is used for manufacturing a medical ultrasonic probe, the FPC of the medical ultrasonic probe has the advantages that the assembly space of the product is small, the FPC structure is compact, the wiring density of the product is high, meanwhile, copper in a key area ultrasonic wave transmitting and recovering area of the product needs to be thin and the thickness of the copper needs to be uniform (+/-1.0 micron), the assembly area space is small, the position where the product is connected with other accessories is manually welded, hollow fingers need to be adopted, and the copper in the hollow finger area needs to be thick.

The conventional double-sided hollow finger process is manufactured by adopting a thick copper local copper reduction process, the copper thickness tolerance of thick copper is large, the thickness deviation of the remaining copper after copper reduction is large (+/-2.0 microns), and the copper thickness control requirement of an ultrasonic probe cannot be met (+/-1.0 micron). And adopt thin copper technology direct manufacturing two-sided fretwork finger board, the fretwork region leads to the fretwork finger fracture easily in the manufacturing process because of the copper is thin, and the customer assembles the time and after the assembly finger fracture easily, and production preparation yield is low, and the quality risk is high.

Disclosure of Invention

The invention aims to provide a local ultrathin hollowed double-layer FPC product and a manufacturing method thereof, so as to solve the problems. Therefore, the invention adopts the following specific technical scheme:

according to an aspect of the present invention, there is provided a partially ultrathin hollow double-layer FPC product that can be used to manufacture a medical ultrasonic probe. The local ultrathin hollowed double-layer FPC product is provided with a key area and a non-key area, wherein the copper thickness of the key area is smaller than that of the non-key area, a thin covering film and a thick covering film are respectively pasted on the key area and the non-key area, and hollowed fingers are arranged on the non-key area. The local in the local ultra-thin is referred to as a critical area.

Further, the thickness of copper in the critical area is 5 +/-0.5 microns, the PI thickness of the thin covering film is 8 microns, the glue thickness is 15 microns, and the PI thickness of the thick covering film is 25 microns and the glue thickness is 25 microns.

According to another aspect of the invention, a method for manufacturing the local ultrathin hollow double-layer FPC product is provided, which comprises the following steps:

s1, drilling a pin hole, a direction hole and a PTH hole in an FCCL material of ultrathin double-sided copper;

s2, carrying out hole metallization treatment on the copper surface of the FCCL through a black hole process (or a shadow or PTH or organic conductive film process);

s3, performing first copper electroplating to form a layer of thin copper in the PTH and on the surface copper of the non-critical area;

s4, carrying out second copper electroplating to increase the copper thickness of the hollow fingers to be more than 20 micrometers;

s5, removing the redundant copper layer through dry film pasting, exposure development and etching processes, and enabling the designed pattern of the copper metal layer to be reserved on the FCCL;

s6, pasting and pressing a thin cover film with a graph window in the key area, and pasting and pressing a thick cover film with a graph window in the non-key area;

s7, removing the FCCL PI part of the hollowed-out finger area by adopting laser, and reserving copper of the hollowed-out finger;

s8, performing surface treatment on the surface of the exposed copper metal;

and S9, cutting the product according to the appearance of the product by using a cutting process to form the required local ultrathin hollowed double-layer FPC product.

Further, the FCCL material has a copper thickness of 5 ± 0.5 microns and a PI thickness of 25 microns.

Further, the specific process of S3 is:

s31, attaching an anti-electroplating photosensitive dry film or an anti-electroplating photosensitive wet film on a silk screen to the FCCL copper surface subjected to hole metallization;

s32, exposing a film with a pattern on the photosensitive dry film or the photosensitive wet film by using UV light (first exposure), wherein the copper in a key area needs to be protected during pattern design;

s33, developing through a developing solution to expose copper in a non-critical area and copper in a PTH hole;

s34, first electroplating copper to form a layer of thin copper in the PTH hole and on the exposed surface copper;

and S35, removing the photosensitive dry film or the photosensitive wet film.

Further, the first copper electroplating in S3 forms a thin copper layer having a thickness of 6 μm or more.

Further, the specific process of S4 is:

s41, attaching an anti-electroplating photosensitive dry film or an anti-electroplating photosensitive wet film on a screen printing screen to the product subjected to the first copper plating;

s42, exposing the photosensitive dry film or the photosensitive wet film through a film with patterns by using UV light (secondary exposure), wherein the copper in the hollow finger area is required to be protected during pattern design;

s43, developing through a developing solution;

s44, electroplating copper for the second time, wherein the thickness of the copper in the hollow finger area is increased to be more than 20 micrometers;

and S45, removing the photosensitive dry film or the photosensitive wet film.

Furthermore, the windowing pattern of the covering film is formed by adopting a die cutting mode, a plane cutting mode and a laser cutting mode.

Further, the thin cover film has a PI thickness of 8 microns and a glue thickness of 15 microns, and the thick cover film has a PI thickness of 25 microns and a glue thickness of 25 microns.

Further, the surface treatment process comprises electroplating pure gold, electroplating nickel gold, nickel-palladium-gold, silver or tin.

By adopting the technical scheme, the invention has the beneficial effects that: according to the invention, the thin double-layer copper is adopted to separately process the electro-coppering twice, the first local electro-coppering is used for completing PTH hole connection in a non-key area, the second local electro-coppering is used for thickening the copper thickness of the hollow finger area, and CVLs with different thicknesses are pressed on the key area and the non-key area twice, so that the CVLs of the product are not layered and the key area is ultrathin, and the thickness requirement of the medical ultrasonic probe is further met.

Drawings

To further illustrate the various embodiments, the invention provides the accompanying drawings. The accompanying drawings, which are incorporated in and constitute a part of this disclosure, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the embodiments. Those skilled in the art will appreciate still other possible embodiments and advantages of the present invention with reference to these figures. Elements in the figures are not drawn to scale and like reference numerals are generally used to indicate like elements.

FIG. 1 is a flow chart of a method for manufacturing a partially ultrathin hollow double-layer FPC product according to the present invention;

FIG. 2 is a flow chart of a first copper electroplating;

FIG. 3 is a flow chart of a second copper electroplating;

FIG. 4 is a flow chart of etching;

FIG. 5 is a schematic structural diagram of a partially ultrathin hollowed-out double-layer FPC product manufactured by the method of the present invention.

Detailed Description

The invention will now be further described with reference to the accompanying drawings and detailed description.

As shown in fig. 1 to 5, a method for manufacturing a local ultra-thin hollow double-layer FPC product includes the following steps:

s1, drilling (for example, by adopting a laser process or a CNC mechanical drilling process) pin holes, direction holes and PTH holes in the FCCL material of the ultrathin double-sided copper. The copper thickness of the FCCL material is 4-8 microns according to customer requirements, the copper thickness of the FCCL material adopted in the embodiment is 5 ± 0.5 micron, and the PI thickness is 25 microns.

And S2, carrying out hole metallization treatment on the copper surface of the FCCL through a black hole process (or a shadow or PTH or organic conductive film process).

S3, performing first copper electroplating to form a layer of thin copper in the PTH and on the surface copper of the non-critical area.

As shown in fig. 2, the specific process is as follows:

s32, exposing a film with a pattern on the photosensitive dry film or the photosensitive wet film by using UV light (first exposure), wherein the copper in a key area needs to be protected during pattern design and is not electroplated with a new copper layer;

s33, developing the exposed product by using a developing solution to expose the copper in the non-critical area and the copper in the PTH hole;

s34, performing first copper electroplating on the developed product to form a layer of thin copper (for example, the thickness of the copper is more than 6 microns) in the PTH hole and on the exposed surface copper, namely thickening the thickness of the copper in the hole and on the surface by electroplating to realize the purpose of conducting the upper surface and the lower surface;

and S35, removing the photosensitive dry film or the photosensitive wet film (for example, adopting a release agent).

And S4, carrying out second copper electroplating to increase the copper thickness of the hollow finger to be more than 20 microns. As shown in fig. 3, the specific process is as follows:

s42, exposing the photosensitive dry film or the photosensitive wet film through a film with a pattern by using UV light (secondary exposure), wherein the pattern design needs to ensure that copper in the hollow finger area is not protected, and a new copper layer can be electroplated;

s43, developing the exposed product by a developing solution;

s44, carrying out second copper electroplating on the developed product, and increasing the copper thickness of the hollow fingers to be more than 20 microns;

and S45, removing the photosensitive dry film or the photosensitive wet film (for example, adopting a release agent).

And S5, removing the redundant copper layer through processes of photosensitive film pasting, exposure development and etching, and keeping the designed pattern of the copper metal layer on the FCCL. As shown in fig. 4, the specific process is as follows:

s51, carrying out micro-etching (or grinding or sand blasting) treatment on the product after the secondary copper plating;

s52, attaching an anti-etching photosensitive dry film or an anti-etching photosensitive wet film on a silk screen to the processed product;

s53, exposing a film with a pattern on the etching-resistant photosensitive dry film or the etching-resistant photosensitive wet film by using UV light (third exposure), wherein the pattern is a pattern designed by customer wiring;

s54, developing the exposed product by a developing solution;

and S55, etching the developed product by using etching solution, and stripping the exposed etching-resistant photosensitive dry film or etching-resistant photosensitive wet film by using a stripping agent to ensure that the pattern of the designed copper metal layer is reserved on the FCCL.

And S6, pasting and pressing a thin covering film with a pattern window in the key area, and pasting and pressing a thick covering film with a pattern window in the non-key area. Specifically, a thin cover film with a pattern window (in this embodiment, a cover film with PI of 8um and glue of 15 um) is bonded to a critical area of the product, and is temporarily pressed, and a thick cover film with a pattern window (in this embodiment, a cover film with PI of 25um and glue of 25 um) is bonded to another area (non-critical area), and is temporarily pressed, and then is quickly pressed and thermally cured. The windowing pattern of the cover film can be formed by punching, plane cutting, laser cutting and the like.

And S7, removing the FCCL PI part of the hollow finger area by adopting laser, and reserving copper of the hollow finger.

S8, carrying out surface treatment on the surface of the exposed copper metal, wherein the surface treatment process comprises pure gold electroplating, nickel gold melting, nickel palladium gold melting, silver melting or tin melting and the like.

And S9, cutting the product according to the appearance of the product by using a cutting process to form the required local ultrathin hollowed double-layer FPC product, as shown in figure 5. Specifically, the local ultrathin hollowed double-layer FPC product comprises a key area and a non-key area, wherein the copper thickness of the key area is smaller than that of the non-key area, specifically, the copper layer of the key area is an FCCL original copper layer, the copper thickness of the key area is 5 +/-0.5 microns, hollowed fingers are arranged on the non-key area, and the copper layers of the hollowed fingers comprise an FCCL original copper layer, a primary copper plating layer and a secondary copper plating layer; the copper layer of the PTH hole region in the non-critical area comprises an FCCL original copper layer and a primary copper plating layer; and a thin cover film and a thick cover film are respectively stuck to the key area and the non-key area, specifically, the PI thickness of the thin cover film is 8 micrometers, the glue thickness is 15 micrometers, and the PI thickness of the thick cover film is 25 micrometers and the glue thickness is 25 micrometers. The local in the local ultra-thin is referred to as a critical area.

According to the invention, the thin double-layer copper is adopted to separately process the electro-coppering twice, the first local electro-coppering is used for completing PTH hole connection in a non-key area, the second local electro-coppering is used for thickening the copper thickness of the hollow finger area, and simultaneously, the covering films (CVLs) with different thicknesses are pasted and pressed on the key area and the non-key area twice, so that the CVLs of the product are not layered and the key area is ultrathin, and the thickness requirement of the medical ultrasonic probe is further met.

While the invention has been particularly shown and described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims

1. The local ultrathin hollowed-out double-layer FPC product is characterized by comprising a key area and a non-key area, wherein the copper thickness of the key area is smaller than that of the non-key area, a thin cover film and a thick cover film are respectively adhered to the key area and the non-key area, and hollowed-out fingers are arranged on the non-key area.

2. The local ultra-thin hollow double-layer FPC product of claim 1, wherein the thickness of copper in a critical area is 5 +/-0.5 microns, the PI thickness of a thin coverlay film is 8 microns, the glue thickness is 15 microns, and the PI thickness of a thick coverlay film is 25 microns, and the glue thickness is 25 microns.

3. The manufacturing method of the local ultrathin hollow double-layer FPC product of claim 1, characterized by comprising the following steps:

s2, carrying out hole metallization treatment on the copper surface of the FCCL;

s5, removing the redundant copper layer through processes of photosensitive film pasting, exposure development and etching, and enabling the pattern of the designed copper metal layer to be reserved on the FCCL;

s8, performing surface treatment on the surface of the exposed copper metal;

4. The method of claim 3, wherein the FCCL material has a copper thickness of 5 ± 0.5 microns and a PI thickness of 25 microns.

5. The manufacturing method according to claim 3, wherein the specific process of S3 is as follows:

and S35, removing the photosensitive dry film or the photosensitive wet film.

6. The method of claim 3 or 5, wherein the first copper electroplating step of S3 is performed to form a thin copper layer with a thickness of 6 μm or more.

7. The manufacturing method of claim 5, wherein the specific process of S4 is as follows:

s43, developing through a developing solution;

and S45, removing the photosensitive dry film or the photosensitive wet film.

8. The method of claim 3, wherein the windowed pattern of the cover film is formed by die cutting, planar cutting, or laser cutting.

9. The method of claim 3, wherein the thin cover film has a PI thickness of 8 microns and the glue thickness of 15 microns, and the thick cover film has a PI thickness of 25 microns and the glue thickness of 25 microns.

10. The method of claim 3, wherein the surface treatment comprises electroplating pure gold, electroplating nickel gold, nickel-palladium-gold, silver or tin.