Single-sided board multiplexing structure applied to wireless charging system

Abstract

The utility model provides a single-sided board multiplexing structure applied to a wireless charging system. The single-sided board multiplexing structure comprises a first single-sided FPC board which comprises a first copper layer, a first base film and a cover film; the second single-sided FPC board comprises a second copper layer, a second base film and a covering film; the thickness of the bonding layer is 3-8 microns, and the bonding layer is located between the first single-face FPC board and the second single-face FPC board and used for fixing the first single-face FPC board and the second single-face FPC board; and the copper layers of the first single-sided FPC board and the second single-sided FPC board are respectively positioned on the outer sides, and interlayer conduction is realized through the bonding layer. According to the utility model, two single-sided boards are overlapped to replace a traditional double-sided board structure, so that the material cost is reduced by more than 25%; through hole electroplating (PTH), double-side etching and other complex processes are omitted, the production process is simplified, and the comprehensive cost is reduced by 18%-22%; the single-sided board is processed in a split manner, so that the alignment error of double-sided imaging is avoided, and the yield loss is reduced; interlayer conduction is achieved through filling of the conductive adhesive or the solder, a traditional electroplating process is replaced, and the process complexity and the defect risk are reduced.

Description

Technical Field

[0001] This utility model relates to the technical field of flexible printed circuit boards (FPC) and wireless charging, specifically to a single-sided reusable structure applied to a wireless charging system. Background Technology

[0002] In the field of wireless charging systems, flexible printed circuit boards (FPCs) are a core component, and their design must balance electrical performance, mechanical reliability, and manufacturing cost. Traditionally, double-sided and single-sided boards are the two main solutions, but both have significant limitations.

[0003] Limitations of traditional double-sided panels:

[0004] 1. High cost: Double-sided boards require double-sided copper-clad film (such as polyimide film), and the material cost is more than 30% higher than that of single-sided boards; its manufacturing process involves double-sided patterning etching, drilling and through-hole plating (PTH), which is complex and results in significant yield loss.

[0005] 2. The conflict between thickness and flexibility: The base film thickness of a typical double-sided panel is usually ≥25μm (including the copper layer), and the total thickness after stacking the cover film reaches 61.5μm, which limits the bending performance of flexible devices. In addition, ultra-thin copper thickness (such as 12μm) further increases costs due to the difficulty of the process.

[0006] 3. Reliability risk: Through-hole electroplating is prone to voids or fractures due to mechanical stress (such as bending), which leads to a long-term decrease in reliability. The bending life is usually less than 60,000 cycles.

[0007] Bottlenecks of single-sided boards:

[0008] While single-sided boards offer advantages such as low cost (simple single-sided etching process) and thinness (typical total thickness 37μm), their single-layer wiring structure has inherent drawbacks:

[0009] 1. Insufficient current density and heat dissipation: The thickness of a single copper layer cannot meet the current density requirements of medium and high power wireless charging (such as above 15W), resulting in low heat dissipation efficiency and easy temperature rise issues.

[0010] 2. Limited inductance performance: The inductance (Q value) of a single copper layer is low, making it difficult to adapt to fast charging standards. The measured power limit is usually ≤10W.

[0011] The aforementioned issues make it difficult for traditional solutions to achieve a balance in scenarios with stringent requirements for cost, thickness, and power, such as consumer electronics (e.g., foldable phones, TWS earphones) and automotive electronics. Therefore, there is an urgent need for an innovative structural design that can retain the cost and flexibility advantages of single-panel displays while overcoming their performance bottlenecks. Utility Model Content

[0012] To address the shortcomings of existing technologies, the purpose of this invention is to provide a single-panel multiplex structure for use in wireless charging systems.

[0013] According to the present invention, a single-panel multiplex structure for use in a wireless charging system includes:

[0014] The first single-sided FPC board includes a first copper layer, a first base film, and a cover film;

[0015] The second single-sided FPC board includes a second copper layer, a second base film, and a cover film.

[0016] Adhesive layer: 3-8μm thick, located between the first single-sided FPC board and the second single-sided FPC board, used to fix the two together;

[0017] The copper layers of the first single-sided FPC board and the second single-sided FPC board are located on the outer side, and interlayer conductivity is achieved through the adhesive layer.

[0018] Preferably, the adhesive layer is a conductive adhesive or a tin wire filling layer, used to replace the electroplated through-hole PTH.

[0019] Preferably, the adhesive layer has a thickness of 5 μm and is made of epoxy resin or acrylic adhesive.

[0020] Preferably, the first single-sided FPC board has a total thickness of 37 μm and includes a 12 μm first copper layer, a 12.5 μm first base film, and a 12.5 μm cover film; the second single-sided FPC board has a total thickness of 24.5 μm and includes a 12 μm second copper layer and a 12.5 μm second base film.

[0021] Preferably, the interlayer conductivity between the first single-sided FPC board and the second single-sided FPC board is achieved through staggered HUB soldering, with large through holes on the upper layer and small pads on the lower layer, and the through holes are filled with solder and connected to the pads on the lower layer.

[0022] Preferably, the first base film and the second base film are polyimide films, and the thickness of a single layer of the first base film and the second base film is 12.5 μm.

[0023] Preferably, the total thickness of the structure is 61.5-66.5 μm, suitable for wireless charging systems with a power of 10-20W.

[0024] Preferably, the bending life of the structure is ≥85,000 cycles, and there is no delamination within 500 hours in an environment with a temperature of 85 degrees and a humidity of 85%RH.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. This utility model uses two single-sided panels stacked together to replace the traditional double-sided panel structure, reducing material costs by more than 25% (the cost of single-sided panel base film is much lower than that of double-sided copper-clad film); it eliminates complex processes such as electroplated through-hole (PTH) and double-sided etching, simplifying the production process and reducing overall costs by 18%-22%; the separate processing of single-sided panels avoids alignment errors in double-sided patterning, reducing yield loss; and interlayer conductivity is achieved through conductive adhesive or solder filling, replacing the traditional electroplating process, reducing process complexity and defect risks.

[0027] 2. The thin adhesive layer (5μm) design of this utility model improves the interlayer bonding strength (≥1.5N / mm), and there is no delamination after 500 hours in a high temperature and humidity environment of 85℃ / 85%RH; the bending life reaches 85,000 cycles (70% higher than traditional double-sided boards), meeting the long-term use requirements of flexible devices; the electrical performance is close to that of double-sided boards, with an inductance (LS) difference of ≤3% and an equivalent resistance (RS) difference of ≤15mΩ, supporting 10-20W medium-power wireless charging with a measured efficiency of 92%; the total thickness is only 66.5μm (including the adhesive layer), which is slightly larger than that of traditional double-sided boards (typical value 61.5μm), but the overall module thickness is controllable, making it suitable for ultra-thin devices such as foldable screen phones; the flexible base film (12.5μm polyimide) combined with the thin adhesive layer improves bending performance and is suitable for vehicle vibration and temperature shock (-40℃~105℃);

[0028] 3. This utility model is compatible with the needs of multiple fields such as consumer electronics (e.g., 10-15W fast charging for mobile phones), automotive electronics (15W wireless charging module for vehicles), and IoT devices (TWS earphones, smartwatch coils); it can be adapted to special scenarios such as high frequency and high temperature by adjusting the base film or adhesive layer material, and has high design flexibility; it reduces the use of chemical reagents in the electroplating process, reducing environmental pollution; and it improves material utilization, which is in line with the trend of green manufacturing. Attached Figure Description

[0029] Other features, objects, and advantages of this invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0030] Figure 1 This is a schematic diagram of a traditional double-sided panel structure;

[0031] Figure 2 This is a schematic diagram of the structure of this utility model.

[0032] in:

[0033] Covering film 1, adhesive layer 4

[0034] First copper layer 2 Second copper layer 5

[0035] First base film 3 Second base film 6 Detailed Implementation

[0036] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the present invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0037] Example 1:

[0038] Reference Figure 2 According to the present invention, a single-sided FPC board for use in a wireless charging system includes: a first single-sided FPC board comprising a first copper layer, a first base film, and a cover film; a second single-sided FPC board comprising a second copper layer, a second base film, and a cover film; and an adhesive layer with a thickness of 3-8 μm, located between the first single-sided FPC board and the second single-sided FPC board for fixing the two together; the copper layers of the first single-sided FPC board and the second single-sided FPC board are located on the outer sides, and interlayer conductivity is achieved through the adhesive layer.

[0039] The adhesive layer is a conductive adhesive or solder wire filler layer, used to replace the plated through-hole (PTH). The adhesive layer is 5μm thick and made of epoxy resin or acrylic adhesive.

[0040] The first single-sided FPC board has a total thickness of 37μm, comprising a 12μm first copper layer, a 12.5μm first base film, and a 12.5μm cover film; the second single-sided FPC board has a total thickness of 24.5μm, comprising a 12μm second copper layer and a 12.5μm second base film. Interlayer connectivity between the first and second single-sided FPC boards is achieved through staggered HUB soldering, with large vias on the upper layer and small pads on the lower layer. Solder is used to fill the vias and connect them to the lower layer pads.

[0041] The first and second base films are polyimide films, and the thickness of a single layer of the first and second base films is 12.5 μm.

[0042] The total thickness of the structure is 61.5-66.5μm, suitable for wireless charging systems with power of 10-20W. The structure has a bending life of ≥85,000 cycles, and no delamination occurs within 500 hours in an environment with a temperature of 85 degrees Celsius and a humidity of 85%RH.

[0043] Example 2:

[0044] This invention belongs to the field of flexible printed circuit board (FPC) and wireless charging technology. Specifically, it relates to a solution that replaces the traditional double-sided board by using a structure that reuses a single-sided board with a thin adhesive layer. This solution combines the cost advantages of a single-sided board with the performance potential of a double-sided board and is suitable for scenarios such as consumer electronics and automotive electronics where cost and flexibility are equally important.

[0045] Reference Figure 1 and Figure 2 A low-cost flexible circuit board structure includes: a first single-sided FPC board comprising a 12μm copper layer, a 12.5μm base film, and a 12.5μm cover film, with a total thickness of 37μm; a second single-sided FPC board comprising a 12μm copper layer, a 12.5μm base film, and a total thickness of 24.5μm; and an adhesive layer with a thickness of 5μm, located between the two single-sided boards and fixing them together.

[0046] Separate processing: Two single-sided panels are etched independently to avoid the alignment error of double-sided patterning on both sides of the double-sided panel;

[0047] Adhesive bonding replaces electroplating: Conductive bonding or tin wire is used to achieve interlayer conductivity, eliminating the need for plated through-hole (PTH) steps.

[0048] HUB soldering: It adopts a staggered design of large through holes (upper layer) and small pads (lower layer) and uses solder to fill and achieve reliable interconnection.

[0049] Comparison of technical advantages

[0050]

[0051]

[0052] 1. Electrical performance

[0053] Inductance (LS): ≤0.07μH (<3%) difference from conventional double-sided boards at 100kHz;

[0054] Equivalent resistance (RS): difference ≤15mΩ (skin effect is controllable).

[0055]

[0056] 2. Mechanical reliability

[0057] Bending test: Under the IPC-6013 standard, it can withstand 65,000 bending cycles (70% higher than traditional double-sided panels);

[0058] High temperature and high humidity: No delamination after 500 hours in an environment of 85℃ / 85%RH (adhesive layer bonding strength ≥1.5N / mm).

[0059] 3. Cost Analysis

[0060] Material costs: Reduced by 25% (cost of single-sided base film for double-sided panels < cost of base film for double-sided panels);

[0061] Process cost: By saving electroplating and double-sided alignment processes, the overall cost is reduced by 18%-22%.

[0062] 4. Application Scenarios:

[0063] Consumer electronics: Supports 10-15W wireless fast charging for mobile phones, and is compatible with ultra-thin designs (such as foldable screen phones);

[0064] Automotive electronics: Compatible with 15W wireless charging modules for vehicles, resistant to vibration and temperature shock (-40℃~105℃);

[0065] IoT devices: Providing cost-effective coil solutions for TWS earphones and smartwatches.

[0066] 5. Industrial Applicability

[0067] Technical feasibility: The bonding process is mature (e.g., epoxy resin or acrylic adhesive), but the adaptability of the adhesive layer to high temperature resistance (welding) and conductivity (if required) needs to be verified. Interlayer alignment accuracy can be achieved using existing equipment (e.g., CCD positioning).

[0068] 6. Commercial value: Cost reduction of 10-30% (actual calculation required), suitable for cost-sensitive FPC application scenarios such as consumer electronics and automotive electronics.

[0069] This invention belongs to the field of wireless charging technology, specifically involving a solution for reusing a single-sided panel to replace a double-sided panel. In addition to showing a price advantage, it also applies a more convenient hub soldering method in terms of process. Simply put, it is a sample between a single-sided panel and a double-sided panel, which has better performance than a single-sided panel and a lower price than a double-sided panel, providing a new approach to cost reduction.

[0070] This invention breaks through the traditional double-sided panel design concept, proposing a superimposed structure of "two single-sided panels + ultra-thin base film + low-thickness adhesive layer" to replace the traditional double-sided panel. Specifically, the solution includes the following core components:

[0071] Single-sided panel structure: It adopts two independent single-sided panels, each with copper on one side. The base film thickness can be selected from conventional 12.5μm polyimide or other flexible materials. The manufacturing process of single-sided panels is simple and has a high yield.

[0072] Adhesive layer design: An adhesive layer with a thickness of only 5μm (such as epoxy resin or acrylic adhesive) is placed between the two single-sided panels, and interlayer bonding is achieved through a hot pressing process;

[0073] Total thickness: The total thickness of the superimposed base film is 25μm (2 layers of 12.5μm) plus 5μm (adhesive layer), totaling 30μm. This is 5μm thicker than the total thickness of the base film of traditional double-sided panels (usually 25μm or more). The overall module thickness (5μm adhesive layer / total module thickness 61.5μm) will be increased by 8.13%.

[0074] Cost savings: Single-sided panel manufacturing eliminates the need for double-sided patterning processes, improving material utilization and allowing the use of low-cost conventional base films, resulting in an overall cost reduction of 20%-30%.

[0075] Simplified process: The production process of single-sided panels is short, and the lamination process only requires one gluing, reducing the risk of defects caused by multiple etching and electroplating processes in traditional double-sided panels;

[0076] Performance improvement: Reducing the thickness of the adhesive layer can improve the interlayer bonding strength and heat dissipation efficiency, while the reduction in total thickness enhances the flexibility and bending life of the FPC (experiments show that the bending resistance is increased by about 15%).

[0077] Design flexibility: It can be adapted to special application scenarios such as high frequency and high temperature by adjusting the type of base film or adhesive layer material of the single panel.

[0078] Those skilled in the art can understand this embodiment as a more specific description of Embodiment 1.

[0079] In the description of this application, it should be understood that the terms "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0080] The specific embodiments of this utility model have been described above. It should be understood that this utility model is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the substantive content of this utility model. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. A single-sided reusable structure for use in a wireless charging system, characterized in that, include: The first single-sided FPC board includes a first copper layer, a first base film, and a cover film; The second single-sided FPC board includes a second copper layer, a second base film, and a cover film. Adhesive layer: 3-8μm thick, located between the first single-sided FPC board and the second single-sided FPC board, used to fix the two together; The copper layers of the first single-sided FPC board and the second single-sided FPC board are located on the outer side, and interlayer conductivity is achieved through the adhesive layer.

2. The single-panel multiplex structure for use in a wireless charging system according to claim 1, characterized in that, The adhesive layer is a conductive adhesive or a tin wire filling layer, used to replace the electroplated through-hole PTH.

3. The single-panel multiplex structure for use in a wireless charging system according to claim 1, characterized in that, The adhesive layer has a thickness of 5 μm and is made of epoxy resin or acrylic adhesive.

4. The single-panel multiplex structure for use in a wireless charging system according to claim 1, characterized in that, The first single-sided FPC board has a total thickness of 37μm and includes a 12μm first copper layer, a 12.5μm first base film, and a 12.5μm cover film; the second single-sided FPC board has a total thickness of 24.5μm and includes a 12μm second copper layer and a 12.5μm second base film.

5. The single-sided multiplexed structure for use in a wireless charging system according to claim 1, characterized in that, Interlayer conductivity between the first and second single-sided FPC boards is achieved through staggered HUB soldering, with large through holes on the upper layer and small pads on the lower layer. Solder is used to fill the through holes and connect them to the pads on the lower layer.

6. The single-sided multiplexed structure for use in a wireless charging system according to claim 1, characterized in that, The first and second base films are polyimide films, and the thickness of a single layer of the first and second base films is 12.5 μm.

7. The single-sided multiplexed structure for use in a wireless charging system according to claim 1, characterized in that, The total thickness of the structure is 61.5-66.5μm, making it suitable for wireless charging systems with a power of 10-20W.

8. The single-sided multiplexed structure for use in a wireless charging system according to claim 1, characterized in that, The structure has a bending life of ≥85,000 cycles and no delamination within 500 hours in an environment with a temperature of 85 degrees Celsius and a humidity of 85%RH.

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