FPC (Flexible Printed Circuit) structure for pulse thermocompression welding

Abstract

The utility model discloses a flexible printed circuit (FPC) structure for pulse thermocompression welding, which comprises an FPC board welded with a printed circuit board (PCB), the FPC board comprises a copper-based FPC main body, a protective film attached to one side or two sides of the copper-based FPC main body, and a plurality of windowing structures arranged on the protective film, the copper-based FPC main body is provided with a plurality of copper-based connecting parts exposed in the plurality of windowing structures, the plurality of copper-based connecting parts of the FPC board are connected with the plurality of bonding pad structures of the PCB through pulse thermocompression welding, and before welding, a layer of OSP solderability preservative film is arranged on the surface of the exposed copper-based connecting part through an Osp process, and the OSP solderability preservative film is arranged on the surface of the exposed copper-based connecting part. The OSP solderability preservative film is used as a barrier layer between a copper-based FPC main body and air so as to prevent a copper-based connecting part from being exposed in the air to be oxidized and corroded, has a good anti-oxidation effect, can well protect the FPC, meets the requirements of a Hotbar welding process, reduces the production cost and ensures the performance of the FPC.

Description

Technical Field

[0001] This utility model relates to the field of flexible printed circuit board technology, specifically to an FPC structure for pulse hot-press welding. Background Technology

[0002] With the development of information electronic products, FPC (generally referring to flexible circuit boards) is a widely used type of circuit board product. In particular, it has the characteristics of being thin, flexible, rollable, low voltage, low power consumption, and low power consumption. Through embedded circuit design, it can embed a large number of compact components in a limited space. The automotive battery modules on the market use FPC busbars to replace the traditional wire harness connection method in order to achieve the purpose of collecting information such as battery module voltage and temperature.

[0003] The connection between existing FPC boards and PCB boards is typically achieved using the HOTBAR process. This process uses hot pressing to melt solder and connect two electronic components that need to be connected. Usually, a flexible FPC is soldered onto a rigid PCB. The PCB has several pads or gold fingers for soldering to the FPC, and the FPC exposes copper substrates for connecting to these gold fingers. However, the FPC substrate is susceptible to acid and humidity, and cannot be stored for long periods. Once opened, it needs to be used as soon as possible because copper substrates exposed to air are prone to oxidation, leading to oxidation and corrosion of the exposed copper substrates on the FPC. This is detrimental to product soldering and affects product quality. Traditionally, chemical immersion gold treatment is used to prevent oxidation of the FPC, a complex and costly process. Therefore, current production processes require anti-oxidation treatment of the copper substrate surface of the FPC to ensure stable and reliable connection quality between the FPC and the PCB. Utility Model Content

[0004] Therefore, the technical problem to be solved by this utility model is to overcome the problem that the exposed copper substrate on the FPC is prone to oxidation and corrosion, which affects the welding quality between the FPC and the PCB and results in poor reliability. This invention provides an FPC structure that performs anti-oxidation treatment on the surface of the copper substrate of the FPC to ensure stable and reliable connection quality between the FPC and the PCB.

[0005] To solve the above-mentioned technical problems, this utility model provides an FPC structure for pulse hot press welding, including an FPC board welded to a PCB board. The PCB board includes multiple pad structures. The FPC board includes a copper-based FPC body and a protective film attached to one or both sides of the copper-based FPC body, and multiple window structures formed on the protective film. The copper-based FPC body is provided with multiple copper-based connecting parts exposed in the multiple window structures corresponding to the multiple pad structures. The copper-based connecting parts are connected to the pad structures through the window structures. An OSP solder resist film is provided on the surface of the copper-based connecting parts, and the OSP solder resist film is located in the corresponding window structure.

[0006] As a preferred embodiment, flux is applied between the copper-based connector and the pad structure of the PCB board, and the OSP solder mask is removed by the flux during high-temperature soldering to expose the surface of the copper-based connector.

[0007] As a preferred embodiment, the flux is a solder structure applied to the pad structure.

[0008] As a preferred embodiment, the copper-based connector 14 is a copper-based FPC body exposed in the window structure, and the thickness of the OSP solder mask is 0.2um-0.4um.

[0009] As a preferred embodiment, the FPC board has a connecting portion that extends and adheres to the PCB board, and the connecting portion is provided with a plurality of copper-based connecting portions.

[0010] As a preferred embodiment, the FPC board has multiple outwardly extending sampling pieces on its side, and multiple sampling lines connecting the multiple sampling pieces and multiple copper base connection parts are formed on the copper-based FPC body.

[0011] As a preferred embodiment, the sampling sheet is a copper foil sheet integrally formed on the side of the copper-based FPC body;

[0012] As a preferred embodiment, the sampling sheet is a nickel sheet structure welded to the side of the copper-based FPC body.

[0013] Compared with the prior art, the technical solution of this utility model has the following advantages:

[0014] 1. In the FPC structure provided by this utility model, multiple copper-based connecting parts are exposed at multiple window structure positions on the FPC board. These copper-based connecting parts are welded to multiple pad structures on the PCB board through a hot-press welding process. Before welding, an OSP solder mask is applied to the surface of the exposed copper-based connecting parts using an OSP process. The OSP solder mask is an organic non-metallic film layer made using the OSP process, which has a simple process control, low cost, and low price. Its function is to act as a barrier layer between the copper-based FPC body and the air to prevent the copper-based connecting parts from being exposed to air and oxidized and corroded. It has a good anti-oxidation effect. Furthermore, this OSP solder mask loses its anti-oxidation protection after being passed through a high-temperature furnace, thus exposing the copper-based connecting parts for welding to the pad structures. The advantage of this technical solution is that the OSP process can effectively protect the FPC, meet the requirements of the Hotbar welding process, and is environmentally friendly. It greatly reduces production costs and ensures the performance of the FPC, thereby ensuring a stable and reliable connection quality between the FPC board and the PCB board.

[0015] 2. In the FPC structure provided by this utility model, flux for welding is applied between the pad structure and the copper base connection. During subsequent high-temperature welding, this OSP solder mask is easily and quickly removed by the molten flux, requiring no special treatment. This allows the exposed copper base connection surface to immediately bond with molten solder to form a strong solder joint in a very short time, thereby completing the welding connection between the copper base connection of the FPC and the pad structure of the PCB. The welding is stable and reliable. Attached Figure Description

[0016] To more clearly illustrate the specific embodiments of this utility model or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this utility model. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0017] Figure 1 A schematic diagram of the stacked structure of the FPC structure provided for the utility model;

[0018] Figure 2 A schematic diagram of the FPC structure provided for the utility model.

[0019] Figure descriptions: 1. FPC board; 10. Connector; 11. Copper-based FPC body; 12. Protective film; 13. Protective film adhesive layer; 14. Copper-based connector; 2. OSP solder resist film; 3. Window structure; 4. Sampling sheet. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0021] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can also refer to the internal connection of two components; and they can refer to a wireless connection or a wired connection. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0022] Furthermore, the technical features involved in the different embodiments of this utility model described below can be combined with each other as long as they do not conflict with each other.

[0023] Example

[0024] This utility model provides, for example Figure 1-2 The illustrated FPC structure for pulse thermoforming includes an FPC board soldered to a PCB board. The PCB board has a plurality of solder pads. The FPC board 1 includes a copper-based FPC body 11 and a protective film 12 adhered to one or both sides of the copper-based FPC body 11, and a plurality of window structures 3 formed on the protective film 12. The protective film 12 is adhered to the copper-based FPC body 11 with an adhesive layer, and a protective film is formed between the protective film 12 and the copper-based FPC body 11. The adhesive layer 13 provides insulation and protection to both sides of the copper-based FPC body through the protective film 12. The copper-based FPC body 11 has multiple copper-based connecting parts 14 exposed in multiple window structures 3 corresponding to multiple pad structures. The copper-based connecting parts 14 are welded to the pad structures through the window structures 3. The function of the window structures is to expose the copper-based connecting parts for connecting the pad structures. The surface of the copper-based connecting parts 14 is provided with an OSP solder resist film 2, which is accommodated in the corresponding window structure.

[0025] The above-described implementation method is the core technical solution of this embodiment. The FPC board 1 has multiple copper-based connecting parts 14 exposed at multiple window structures 3. The FPC board is welded to multiple pad structures on the PCB board via these copper-based connecting parts through a thermo-press welding process (the PCB board is not shown in the attached diagram). Before welding, an OSP solder mask 2 is applied to the surface of the exposed copper-based connecting parts 14 using an OSP process. This OSP solder mask 2 is an organic non-metallic film layer made using the OSP process. Compared to the traditional immersion gold process, it has simpler process control, lower cost, and is cheaper. Its function is to protect the copper-based FPC body 11. The OSP (Optical Sealant Protection) layer acts as a barrier between the copper-based connector 14 and the air to prevent oxidation and corrosion. It has excellent anti-oxidation properties. During the molding and welding process, this OSP loses its anti-oxidation protection after passing through a high-temperature furnace, thus exposing the copper-based connector 14 for welding to the pad structure. The advantage of this technical solution is that the OSP process can effectively protect the FPC, meet the requirements of the Hotbar welding process, and is environmentally friendly. It greatly reduces production costs and ensures the performance of the FPC, thereby ensuring a stable and reliable connection between the FPC board 1 and the PCB board.

[0026] The following is combined Figure 1-2 The specific setup method between the FPC board and the PCB board is explained in detail:

[0027] Flux is applied between the copper-based connector 14 and the pad structure. During high-temperature soldering, the OSP solder mask 2 is removed by the flux to expose the surface of the copper-based connector 14. More preferably, the flux is a solder structure applied to the pad structure. With this configuration, the OSP solder mask 2 is easily and quickly removed by the molten flux during subsequent high-temperature soldering, requiring no special treatment. This allows the exposed surface of the copper-based connector 14 to immediately bond with the molten solder to form a strong solder joint in a very short time, thus completing the soldering connection between the copper-based connector of the FPC board 1 and the pad structure of the PCB board, resulting in a stable and reliable soldering connection.

[0028] In this embodiment, the copper-based connecting part 14 is the copper base sheet of the copper-based FPC body 11 exposed in the window structure 3. The OSP solder mask 2 is an organic coating used to prevent the copper base sheet of the FPC board from oxidizing before soldering, that is, to protect the solderability of the copper base sheet from being damaged. The thickness of this OSP solder mask is 0.2um-0.4um. After the surface of the copper base sheet of the FPC board using this technical solution is treated with OSP process, a molecular film is formed on the surface of the copper base sheet. During the reflow soldering process, when a certain temperature is reached, this OSP solder mask layer is relatively easy to evaporate, thereby naturally exposing the copper base sheet and completing the soldering with the pad structure.

[0029] In a further preferred configuration, the surface of the pad structure is provided with at least one layer of metal plating, which is a nickel-gold plating film disposed on the surface of the pad structure. With this configuration, the PCB board is plated with a nickel-gold plating film on the surface of the pads through a chemical gold plating process during the production process. This is used to prevent the surface of the PCB board pads from being oxidized or corroded, and to facilitate soldering contact. The nickel-gold plating film can achieve good electrical performance during the long-term use of the PCB board and can protect the PCB board for a long time.

[0030] In this embodiment, as Figure 1 As shown, the FPC board has a flexible and extendable connecting portion 10 that is attached to the PCB board. The connecting portion 10 is provided with a plurality of copper-based connecting portions 14. The FPC board 1 and the PCB board are connected by pulse hot-press welding to achieve the corresponding connection between the plurality of copper-based connecting portions and the plurality of pad structures. After cooling and solidification, the copper-based connecting portions 14 and the pad structures form a permanent electromechanical connection through the solidified solder. The connection is stable and reliable, which is conducive to the automated production of the product.

[0031] like Figure 2 As shown, multiple sampling plates 4 extending outward are provided on the side of the FPC board 1, and multiple sampling lines connecting the multiple sampling plates and multiple copper-based connection parts 14 are formed on the copper-based FPC body 11. This realizes the circuit connection between the FPC board 1 and the PCB board. The FPC enables the power battery to perform overcurrent protection, temperature acquisition, and voltage acquisition functions, effectively monitoring the voltage and temperature of the battery cells, thereby protecting the automotive power battery cells. The sampling plates are connected to the cells of the automotive power battery. Based on the FPC board 1 as a sampling channel connecting the cells and the controller, the FPC board 1 can accurately collect information such as the voltage of the cells through the sampling plates. In a further preferred configuration, the sampling piece 4 is a copper foil sheet integrally formed on the side of the copper-based FPC body 11. The integral structure has good stability, is easy to form and manufacture, and simplifies the production process. Alternatively, the sampling piece 4 can be a nickel sheet structure welded to the side of the copper-based FPC body 11. The nickel sheet structure has good weldability and plays an important role in connecting and conducting electricity between the FPC and the battery cell, dissipating heat, enhancing structural strength, and preventing oxidation.

[0032] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the protection scope of this invention.

Claims

1. A FPC structure for pulse thermal compression bonding, comprising a FPC board (1) to be bonded with a PCB board, and a plurality of pad structures are provided on the PCB board correspondingly, characterized in that: The FPC board (1) comprises a copper-based FPC body (11) and a protective film (12) attached to one side or both sides of the copper-based FPC body (11), and a plurality of window structures (3) opened on the protective film (12), the copper-based FPC body (11) is provided with a plurality of copper-based connecting parts (14) exposed in the plurality of window structures (3), the copper-based connecting parts (14) are connected with the pad structure through the window structure (3), and the surface of the copper-based connecting part (14) is provided with an OSP presoldering film (2).

2. The FPC structure for use in impulse heat staking according to claim 1, characterized in that: The copper-based connecting part (14) and the pad structure of the PCB board are coated with a flux, and the OSP presoldering film (2) is removed by the flux during high-temperature welding to expose the surface of the copper-based connecting part (14).

3. The FPC structure for use in impulse heat staking according to claim 2, characterized in that: The flux is a soldering tin structure coated on the OSP presoldering film (2) or the pad structure.

4. The FPC structure for use in impulse heat staking according to claim 1, characterized in that: The copper-based connecting part (14) is a copper-based sheet exposed in the window structure of the copper-based FPC body, and the thickness of the OSP presoldering film (2) is 0.2-0.4 um.

5. The FPC structure for use in impulse heat staking according to any one of claims 1 to 4, characterized in that: The FPC board (1) has an extension connection part (10) attached to the PCB board, and the connection part (10) is provided with a plurality of copper-based connecting parts (14).

6. The FPC structure for use in impulse thermal compression bonding according to claim 1, characterized by: The FPC board (1) is provided with a plurality of sampling sheets (4) extending outward on the side edge, and a plurality of sampling lines connecting the plurality of sampling sheets and the plurality of copper-based connecting parts (14) are formed on the copper-based FPC body (11).

7. The FPC structure for use in impulse heat staking according to claim 6, characterized in that: The sampling sheet (4) is a copper foil sheet integrally formed on the side edge of the copper-based FPC body (11).

8. The FPC structure for use in impulse heat staking according to claim 6, characterized in that: The sampling sheet (4) is a nickel sheet structure welded on the side edge of the copper-based FPC body (11).

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