A tin-plated flexible circuit board

Abstract

This invention discloses a tin-plated flexible circuit board, comprising a flexible circuit board substrate, which includes a top copper foil, a base film, and a bottom copper foil arranged sequentially from top to bottom. Multiple substrate through-holes are formed on one side of the flexible circuit board substrate, and a layer of carbon powder is attached to the inner wall of each through-hole. A tin-plated layer with through-holes is then covered on the carbon powder layer to achieve electrical conductivity between the top and bottom copper foils. Circuit areas are etched onto the top and bottom copper foils, and these circuit areas are covered with a tin-plated layer. This application replaces copper plating with tin plating, reducing production costs and improving production efficiency and product yield. Using a tin-plated layer as an etching protection layer effectively prevents defective etching, ensures product quality, and improves the ability to process fine circuits.

Description

Technical Field

[0001] This invention relates to the field of flexible circuit board technology, and specifically to a tin-plated flexible circuit board. Background Technology

[0002] Flexible printed circuit boards (FPCs), also known as flexible boards or simply "flexible boards," are printed circuit boards made of flexible insulating substrates. They possess many advantages that rigid printed circuit boards lack. For example, they can be freely bent, coiled, and folded. Using FPCs can significantly reduce the size of electronic products, meeting the needs of electronic products moving towards higher density, miniaturization, and higher reliability. Therefore, FPCs are widely used in aerospace, military, mobile communications, laptops, computer peripherals, PDAs, digital cameras, and other fields and products.

[0003] As the industry continues to develop, the application areas of flexible printed circuit boards are constantly increasing, and the demand is also growing. The requirements for them are also becoming more diverse. In order to better meet market demands and reduce production costs, it is necessary to continuously optimize the product structure. Summary of the Invention

[0004] The purpose of this invention is to provide a tin-plated flexible circuit board, which replaces the existing copper plating method with tin plating, thereby reducing production costs and improving manufacturing efficiency and product qualification rate.

[0005] To achieve the above objectives, this application proposes a tin-plated flexible circuit board, comprising a flexible circuit board substrate, wherein the flexible circuit board substrate comprises a top copper foil, a base film and a bottom copper foil arranged sequentially from top to bottom; a plurality of substrate through holes are opened on one side of the flexible circuit board substrate, and a layer of carbon powder is attached to the inner wall of each substrate through hole, and a through-hole tin plating layer is covered on the carbon powder layer to realize electrical conduction between the top copper foil and the bottom copper foil.

[0006] Furthermore, circuit areas are etched on the top and bottom copper foils respectively, and these circuit areas are covered with a tin plating layer.

[0007] Furthermore, before etching the circuit area, a top dry film is laid on the top copper foil, and a bottom dry film is laid under the bottom copper foil. Part of the top and bottom dry films are removed by exposure and development to obtain the circuit area. The dry film is a polymer material that undergoes a polymerization reaction when exposed to ultraviolet light, forming a stable substance that adheres to the board surface, thus blocking electroplating and etching.

[0008] Furthermore, the remaining top and bottom dry films are removed through the stripping line, exposing the copper foil that needs to be etched away. Then, alkaline etching is used to etch away the exposed copper foil to form the required circuit.

[0009] Furthermore, the thickness of the tin plating layer is 10-20 μm.

[0010] Furthermore, the base film is made of polyimide.

[0011] Compared with the prior art, the above technical solutions adopted in this invention have the following advantages: This application replaces copper plating with tin plating, which reduces production costs and improves production efficiency and product qualification rate; using a tin plating layer as an etching protection layer effectively prevents poor etching, ensures product quality, and improves the fine circuit processing capability. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of the flexible circuit board substrate structure.

[0013] Figure 2 A schematic diagram showing the process of laying a dry film on a flexible circuit board substrate.

[0014] Figure 3 This is a schematic diagram of the dry film exposure and development process on a flexible circuit board substrate.

[0015] Figure 4 A schematic diagram of the circuit area on a flexible circuit board substrate after tin plating.

[0016] Figure 5 A schematic diagram showing the flexible circuit board substrate after the dry film has been removed.

[0017] Figure 6 This is a schematic diagram of the etched substrate of a flexible circuit board.

[0018] Among them: 1. Top copper foil, 2. Bottom copper foil, 3. Base film, 4. Substrate via, 5. Top dry film, 6. Bottom dry film, 7. Top tin plating layer, 8. Bottom tin plating layer, 9. Through-hole tin plating layer. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of this application and are not intended to limit this application; that is, the described embodiments are only a part of the embodiments of this application, and not all of them. The components of the embodiments of this application described and shown in the accompanying drawings can typically be arranged and designed in various different configurations.

[0020] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0021] Example 1

[0022] This embodiment provides a tin-plated flexible circuit board, comprising: a flexible circuit board substrate, the flexible circuit board substrate including a top copper foil, a base film, and a bottom copper foil arranged sequentially from top to bottom; multiple substrate through holes are formed on one side of the flexible circuit board substrate, and a layer of carbon powder is attached to the inner wall of each substrate through hole. A tin-plated layer with through holes is covered on this carbon powder layer, connecting the circuits between the top copper foil and the bottom copper foil to achieve electrical conductivity. Circuit areas are etched on the top copper foil and the bottom copper foil, and these circuit areas are covered with a tin-plated layer. The tin-plated layer is also divided into a top tin-plated layer and a bottom tin-plated layer, which can protect the inner copper foil from corrosion during etching.

[0023] The manufacturing method of the aforementioned tin-plated flexible circuit board is as follows: First, through holes are drilled in the flexible circuit board substrate, such as... Figure 1 As shown; then, the drilled substrate is passed through black hole lines, so that a layer of carbon powder adheres to the hole wall of the substrate, realizing preliminary electrical conduction between the top and bottom copper foils. Then, top and bottom dry films are pressed onto the front and back sides of the flexible circuit board substrate respectively, as shown. Figure 2 As shown; the circuit area is obtained by removing part of the top dry film and part of the bottom dry film through exposure and development, as shown. Figure 3 As shown; a 10-20µm thick tin layer is plated onto the circuit area using a tin plating process, and a tin plating layer is plated onto the outside of the carbon powder layer for vias, as shown. Figure 4 As shown; the remaining top and bottom dry films are removed through the stripping line, exposing the copper foil that needs to be etched, such as... Figure 5 As shown; then, alkaline etching is used to etch away the exposed copper foil to form the desired circuitry, such as... Figure 6 As shown.

[0024] The foregoing description of specific exemplary embodiments of the invention is for illustrative and explanatory purposes. These descriptions are not intended to limit the invention to the precise forms disclosed, and it will be apparent that many changes and variations can be made in accordance with the foregoing teachings. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application, thereby enabling those skilled in the art to implement and utilize various different exemplary embodiments of the invention, as well as various different choices and variations. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. A method for manufacturing a tin-plated flexible circuit board, characterized in that, include First, through-holes are drilled on the flexible circuit board substrate. Then, the drilled substrate is passed through a black hole line to attach a layer of carbon powder to the hole wall, achieving preliminary electrical conduction between the top and bottom copper foils. Next, top dry film and bottom dry film are pressed on the front and back sides of the flexible circuit board substrate respectively. Part of the top dry film and part of the bottom dry film are removed by exposure and development to obtain the circuit area. A 10-20um thick tin layer is plated on the circuit area by tin plating process, and a through-hole tin plating layer is plated on the outside of the carbon powder layer. The remaining top dry film and bottom dry film are removed by stripping line to expose the copper foil that needs to be etched. Then, the exposed copper foil is etched away by alkaline etching to form the required circuit. The tin-plated flexible circuit board includes a flexible circuit board substrate, which includes a top copper foil, a base film, and a bottom copper foil arranged sequentially from top to bottom. A plurality of substrate through holes are opened on one side of the flexible circuit board substrate, and a layer of carbon powder is attached to the inner wall of each substrate through hole. The carbon powder is covered with a through-hole tin plating layer to realize electrical conduction between the top copper foil and the bottom copper foil. Circuit areas are etched on the top copper foil and the bottom copper foil respectively, and the circuit areas are covered with a tin plating layer. Before etching out the circuit area, a top dry film is laid on the top copper foil and a bottom dry film is laid under the bottom copper foil. The circuit area is obtained by removing part of the top dry film and part of the bottom dry film through exposure and development. The remaining top and bottom dry films are removed by the stripping line, exposing the copper foil that needs to be etched away. The exposed copper foil is then etched away by alkaline etching to form the required circuit. The thickness of the tin plating layer is 10-20 μm; The base membrane is made of polyimide.

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