CN114423150A

CN114423150A - Tinned flexible circuit board

Info

Publication number: CN114423150A
Application number: CN202210111153.8A
Authority: CN
Inventors: 孙士卫; 黄庆林
Original assignee: Dalian Jixing Electronics Inc ltd
Current assignee: Dalian Jixing Electronics Inc ltd
Priority date: 2022-01-27
Filing date: 2022-01-27
Publication date: 2022-04-29

Abstract

The invention discloses a tinned flexible circuit board, which comprises a flexible circuit board substrate, wherein the flexible circuit board substrate comprises a top layer copper foil, a base film and a bottom layer copper foil which are sequentially arranged from top to bottom; a plurality of substrate through holes are formed in one side of the flexible circuit board substrate, a layer of carbon powder is attached to the inner wall of each substrate through hole, and a via hole tin plating layer covers the layer of carbon powder, so that the top copper foil and the bottom copper foil are electrically conducted. And etching circuit areas on the top layer copper foil and the bottom layer copper foil respectively, wherein the circuit areas are covered with tin plating layers. The method has the advantages that a tinning mode replaces a copper plating mode, so that the production cost is reduced, and the production efficiency and the product percent of pass are improved; the tin coating is used as an etching protective layer, so that poor etching is effectively prevented, the product quality is ensured, and the fine circuit processing capacity is improved.

Description

Tinned flexible circuit board

Technical Field

The invention relates to the technical field of flexible circuit boards, in particular to a tinned flexible circuit board.

Background

The flexible circuit board is called as a 'soft board' in short, is commonly called as FPC in the industry, is a printed circuit board made of flexible insulating base materials, and has the advantages that many rigid printed circuit boards do not have. For example it may be freely bent, folded, etc. The flexible circuit board can greatly reduce the volume of the electronic product, and is suitable for the development of the electronic product towards high density, miniaturization and high reliability. Therefore, the flexible circuit board is widely applied to the fields or products of aerospace, military, mobile communication, laptop computers, computer peripherals, PDAs, digital cameras and the like.

Along with the continuous development of the industry, the application field of the flexible circuit board is continuously increased, the demand is continuously increased, the requirements on the flexible circuit board are also diversified, and in order to better meet the market demand and reduce the production cost, the product structure needs to be continuously optimized.

Disclosure of Invention

The invention aims to provide a tinned flexible circuit board, which replaces the existing copper plating mode by a tinning mode, reduces the production cost, and improves the manufacturing efficiency and the product percent of pass.

In order to achieve the purpose, the application provides a tinned flexible circuit board, which comprises a flexible circuit board substrate, wherein the flexible circuit board substrate comprises a top layer copper foil, a base film and a bottom layer copper foil which are sequentially arranged from top to bottom; a plurality of substrate through holes are formed in one side of the flexible circuit board substrate, a layer of carbon powder is attached to the inner wall of each substrate through hole, and a via hole tin plating layer covers the layer of carbon powder, so that the top copper foil and the bottom copper foil are electrically conducted.

Furthermore, circuit areas are etched on the top copper foil and the bottom copper foil respectively, and the circuit areas are covered with tin plating layers.

Furthermore, before the circuit area is etched, a top layer dry film is laid on the top layer copper foil, a bottom layer dry film is laid under the bottom layer copper foil, and a part of the top layer dry film and a part of the bottom layer dry film are removed in an exposure and development mode to obtain the circuit area. The dry film is a high molecular material, and can generate a polymerization reaction after being irradiated by ultraviolet rays to form a stable substance to be attached to the board surface, thereby achieving the functions of blocking electroplating and etching.

Further, the residual top layer dry film and the residual bottom layer dry film are removed through the film removing line, the copper foil needing to be corroded is exposed, and then the exposed copper foil is etched through alkaline etching to form the needed circuit.

Further, the thickness of the tin coating is 10-20 um.

Furthermore, the basement membrane is made of polyimide.

Compared with the prior art, the technical scheme adopted by the invention has the advantages that: the method has the advantages that a tinning mode replaces a copper plating mode, so that the production cost is reduced, and the production efficiency and the product percent of pass are improved; the tin coating is used as an etching protective layer, so that poor etching is effectively prevented, the product quality is ensured, and the fine circuit processing capacity is improved.

Drawings

FIG. 1 is a schematic view of a substrate structure of a flexible circuit board;

FIG. 2 is a schematic diagram of a flexible circuit board base material after a dry film is laid;

FIG. 3 is a schematic diagram of a dry film on a substrate of a flexible circuit board after exposure and development;

FIG. 4 is a schematic diagram of a flexible circuit board substrate after a circuit area is tinned;

FIG. 5 is a schematic diagram of the flexible circuit board substrate after the dry film is removed;

FIG. 6 is a schematic diagram of the flexible circuit board after etching.

Wherein: 1. the copper foil comprises a top copper foil, 2 a bottom copper foil, 3 a base film, 4 a substrate through hole, 5 a top dry film, 6 a bottom dry film, 7 a top tin plating layer, 8 a bottom tin plating layer and 9 a via hole tin plating layer.

Detailed Description

In order to make the objects, technical solutions and advantages of the present application more apparent, the present application is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the application, i.e., the embodiments described are only a subset of, and not all embodiments of the application. The components of the embodiments of the present application, generally described and illustrated in the figures herein, can be arranged and designed in a wide variety of different configurations.

Thus, the following detailed description of the embodiments of the present application, presented in the accompanying drawings, is not intended to limit the scope of the claimed application, but is merely representative of selected embodiments of the application. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present application without making any creative effort, shall fall within the protection scope of the present application.

Example 1

The embodiment provides a tinned flexible line way board, includes: the flexible circuit board comprises a flexible circuit board base material, wherein the flexible circuit board base material comprises a top layer copper foil, a base film and a bottom layer copper foil which are sequentially arranged from top to bottom; a plurality of substrate through holes are formed in one side of the substrate of the flexible circuit board, a layer of carbon powder is attached to the inner wall of each substrate through hole, a via hole tin plating layer covers the layer of carbon powder, the top copper foil and the bottom copper foil are connected through a circuit, and the electric performance conduction is realized. And etching circuit areas on the top layer copper foil and the bottom layer copper foil respectively, wherein the circuit areas are covered with tin plating layers. The tin coating is also divided into a top tin coating and a bottom tin coating, and the copper foil on the inner side can be protected from corrosion during etching.

The manufacturing method of the tinned flexible circuit board comprises the following steps: firstly, drilling a substrate through hole on a substrate of a flexible circuit board, as shown in figure 1; then, the drilled substrate passes through a black hole line, so that a layer of carbon powder is attached to the wall of the through hole of the substrate, the primary electrical conduction between the top copper foil and the bottom copper foil is realized, and then the top dry film and the bottom dry film are respectively pressed on the front side and the back side of the substrate of the flexible circuit board, as shown in fig. 2; removing part of the top dry film and part of the bottom dry film by exposure and development to obtain a circuit area, as shown in fig. 3; plating a tin layer with the thickness of 10-20um on the circuit area and plating a via hole tin layer outside the carbon powder layer by a tin plating process, as shown in figure 4; removing the remaining top dry film and bottom dry film through a film removing line, and exposing the copper foil to be etched, as shown in fig. 5; the exposed copper foil is etched away by alkaline etching to form the desired circuit, as shown in fig. 6.

The foregoing descriptions of specific exemplary embodiments of the present invention have been presented for purposes of illustration and description. It is not intended to limit the invention to the precise form disclosed, and obviously many modifications and variations are possible in light of the above teaching. The exemplary embodiments were chosen and described in order to explain certain principles of the invention and its practical application to enable one skilled in the art to make and use various exemplary embodiments of the invention and various alternatives and modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims and their equivalents.

Claims

1. The tinned flexible circuit board is characterized by comprising a flexible circuit board substrate, wherein the flexible circuit board substrate comprises a top layer copper foil, a base film and a bottom layer copper foil which are sequentially arranged from top to bottom; a plurality of substrate through holes are formed in one side of the flexible circuit board substrate, a layer of carbon powder is attached to the inner wall of each substrate through hole, and a via hole tin plating layer covers the layer of carbon powder, so that the top copper foil and the bottom copper foil are electrically conducted.

2. The tin-plated flexible wiring board of claim 1, wherein a wiring region is etched on each of the top copper foil and the bottom copper foil, and the wiring region is covered with a tin-plated layer.

3. The tin-plated flexible wiring board of claim 2, wherein the top dry film is laid on the top copper foil and the bottom dry film is laid under the bottom copper foil before etching the wiring region, and the wiring region is obtained by removing part of the top dry film and part of the bottom dry film by exposure and development.

4. The tin-plated flexible wiring board of claim 3, wherein the remaining portions of the top dry film and the bottom dry film are removed by a film stripping line to expose the copper foil to be etched, and the exposed copper foil is etched by alkaline etching to form the desired circuit.

5. The tin-plated flexible wiring board of claim 2, wherein the tin-plated layer has a thickness of 10 to 20 μm.

6. The tin-plated flexible wiring board according to claim 1, wherein the base film is made of polyimide.