High-reliability vehicle-mounted module FPC structure and preparation method thereof
By employing a four-layer structure and precision machining technology, the electromagnetic shielding effect, mechanical strength, and bonding strength of the vehicle-mounted FPC are improved, solving the reliability problem of traditional FPCs in the vehicle environment and achieving signal stability and durability.
Patent Information
- Application Number
- CN202511692315.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-18
- Publication Date
- 2026-02-27
AI Technical Summary
Traditional automotive FPCs suffer from poor anti-static capabilities, insufficient mechanical strength, unsatisfactory electromagnetic shielding, and weak bonding structures, making it difficult to meet the high reliability requirements of the automotive environment.
The FPC design employs a four-layer structure, including a substrate layer, first and second rolled copper layers, an FR4 reinforcement layer, a cover layer, and an EMI shielding layer. Combined with copper ground lines, grid copper, and a shaped bonding structure, it ensures signal stability and connection reliability through precision machining and laser engraving technology.
It achieves improved electromagnetic shielding across the entire frequency band, enhanced bending resistance, stronger bonding strength, adaptability to a wide temperature range in vehicles, extended service life, and improved product consistency.
Smart Images
Figure CN121586150A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of flexible printed circuit board technology, and in particular to a high-reliability automotive module FPC structure and its fabrication method. Background Technology
[0002] As the core of vehicle interaction, in-vehicle touch displays place extremely high demands on the performance of FPCs. Traditional FPCs have the following drawbacks: poor anti-static capability, which easily leads to signal interference; insufficient mechanical strength, which makes them prone to tearing under vibration; unsatisfactory electromagnetic shielding effect, affecting signal stability; and insufficient bonding strength, which makes connections prone to loosening.
[0003] For example, while existing technologies have solved some problems, they still suffer from single shielding layers, weak bonding structures, and the special characteristics of the vehicle environment (such as temperature changes and electromagnetic interference) require FPCs to have higher reliability.
[0004] To address these shortcomings, a high-reliability vehicle-mounted module FPC structure and its fabrication method are provided to solve the aforementioned technical problems. Summary of the Invention
[0005] To address the technical problems mentioned in the background section, this invention provides a high-reliability vehicle-mounted module FPC structure and its fabrication method.
[0006] The present invention is achieved by the following technical solution: a high-reliability vehicle module FPC structure, including a substrate layer, a first rolled copper layer, an FR4 reinforcement layer, a second rolled copper layer, a cover layer, an EMI shielding layer and a shaped bonding structure. The first rolled copper layer and the second rolled copper layer are symmetrically arranged to form a four-layer rolled copper structure, and a copper ground line is reserved at the edge of the upper and lower circuit layers. The two layers outside the upper and lower circuit surfaces are covered with a grid of copper.
[0007] As a further improvement to the above solution, the substrate layer is made of polyimide film with a thickness of 25-50μm, which has high heat resistance and flexibility, preferably with a thickness of 30μm, to adapt to temperature changes and mechanical stress in the vehicle environment.
[0008] As a further improvement to the above scheme, the thickness of both the first rolled copper layer and the second rolled copper layer is 12-18μm, preferably 15μm, the purity of the rolled copper is not less than 99.9%, and the conductivity is ≥58MS / m, to ensure the stability and low loss of signal transmission.
[0009] As a further improvement to the above solution, the EMI shielding layer is made of black EMI material, which completely covers the front and back of the FPC body, with a surface resistance of less than 1Ω / sq and a thickness of 10-20μm, preferably 15μm, to achieve full-band electromagnetic shielding.
[0010] As a further improvement of the above solution, the cross-shaped binding structure is located at the FPC binding position, formed by CNC precision machining, with a dimensional tolerance of ±0.02 mm, surface gold plating treatment, a gold plating thickness of 0.5 μm, and a binding strength ≥49 N to prevent loosening of the connection under vibration conditions.
[0011] As a further improvement of the above solution, the laying density of the grid copper is 100 - 150 mesh / in², preferably 120 mesh / in², the coverage rate is not less than 95%, and the grid line width is 0.1 - 0.2 mm, forming a uniform shielding network to enhance the anti-interference ability.
[0012] As a further improvement of the above solution, the width of the copper ground wire is 0.5 - 1.0 mm, the edge distance from the center of the line is 0.2 mm, and the line width tolerance is ±0.05 mm, controlled by laser engraving to improve the anti-tearing and anti-static effects.
[0013] A preparation method for a highly reliable vehicle-mounted module FPC structure includes the following steps:
[0014] a. Select high-quality rolled copper as the base material and design and manufacture it according to a four-layer symmetrical structure;
[0015] b. Precisely control the width and position of the copper ground wires at the edges of the upper and lower circuit layers to ensure the anti-tearing and anti-static effects;
[0016] c. Uniformly lay grid copper on the two layers outside the upper and lower circuit surfaces to ensure the integrity of the shielding layer;
[0017] d. Completely wrap the front and back of the FPC body with black EMI material to make it closely covered;
[0018] e. For the cross-shaped structure at the binding position, adopt a special processing technology to ensure the shape and dimensional accuracy;
[0019] f. When processing the PIN, strictly control the inner shrinkage dimension to be 0.3 mm
[0020] As a further improvement of the above solution, in step a, the vacuum lamination process is adopted, with a pressure of 2.5 - 3.5 MPa, a temperature of 180 ± 5 °C, and a time of 60 - 90 min to ensure no bubbles in the interlayer bonding; in step b, the control of the copper ground wire adopts laser engraving technology with an accuracy of 0.01 mm and real-time optical detection.
[0021] As a further improvement of the above solution, in step f, the inner shrinkage dimension of the PIN foot is controlled within 0.3 ± 0.05 mm, the laser cutting process is adopted, and optical detection is carried out after cutting to ensure no burrs and deviations; in step d, the wrapping of the EMI material adopts the hot pressing process, with a temperature of 150 °C, a holding pressure time of 30 s, and the uniformity of the coverage is monitored by infrared thermal imaging.
[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0023] (i) This invention achieves full-band electromagnetic shielding through a triple shielding design of copper ground wire, copper grid and EMI material, improving shielding effectiveness by ≥15dB and effectively solving the signal interference problem in the vehicle environment.
[0024] (ii) The present invention uses rolled copper material and FR4 reinforcement layer structure, which makes the FPC withstand more than 1 million bending cycles, with a bonding strength of ≥49N, and adaptable to a wide temperature range of -45℃ to 125℃ in vehicles.
[0025] (iii) This invention controls key dimensions through laser engraving and CNC machining, avoiding short circuit risks and improving product consistency and service life. Attached Figure Description
[0026] Figure 1 This is a schematic diagram of the high-reliability vehicle-mounted module FPC structure of the present invention;
[0027] Figure 2 This is a flow chart of the FPC preparation process of the present invention.
[0028] Explanation of key symbols:
[0029] 1. Substrate layer; 2. First rolled copper layer; 3. FR4 reinforcement layer; 4. Second rolled copper layer; 5. Cover layer; 6. EMI shielding layer; 7. T-shaped bonding structure. Detailed Implementation
[0030] The present invention will now be further described in conjunction with the accompanying drawings and specific embodiments. It should be noted that, without conflict, the various embodiments or technical features described below can be arbitrarily combined to form new embodiments.
[0031] Example 1:
[0032] Please combine Figure 1 This embodiment presents a high-reliability vehicle-mounted module FPC structure:
[0033] It includes a substrate layer 1, a first rolled copper layer 2, an FR4 reinforcement layer 3, a second rolled copper layer 4, a cover layer 5, an EMI shielding layer 6, and a shaped bonding structure 7. The first rolled copper layer 2 and the second rolled copper layer 4 are symmetrically arranged to form a four-layer rolled copper structure, and a copper ground line is reserved at the edge of the upper and lower circuit layers. The two layers outside the upper and lower circuit surfaces are covered with a grid of copper.
[0034] The substrate layer 1 is made of polyimide film with a thickness of 25-50μm, which has high heat resistance and flexibility. The preferred thickness is 30μm to adapt to temperature changes and mechanical stress in the vehicle environment.
[0035] The thicknesses of both the first rolled copper layer 2 and the second rolled copper layer 4 are 12 - 18 μm, preferably 15 μm. The purity of the rolled copper is not less than 99.9%, and the conductivity is ≥58 MS / m, ensuring the stability and low loss of signal transmission.
[0036] The EMI shielding layer 6 is a black EMI material that completely covers the front and back of the FPC body. The surface resistance is less than 1 Ω / sq, and the thickness is 10 - 20 μm, preferably 15 μm, achieving full-band electromagnetic shielding.
[0037] The cross-shaped bonding structure 7 is located at the FPC bonding position, formed by CNC precision machining. The dimensional tolerance is ±0.02 mm, the surface is gold-plated, and the gold-plating thickness is 0.5 μm. The bonding strength is ≥49 N, preventing connection loosening under vibration conditions.
[0038] The laying density of the grid copper is 100 - 150 meshes / in², preferably 120 meshes / in², the coverage rate is not less than 95%, and the grid line width is 0.1 - 0.2 mm, forming a uniform shielding network and enhancing the anti-interference ability.
[0039] The width of the copper ground wire is 0.5 - 1.0 mm, the edge distance from the center of the line is 0.2 mm, and the line width tolerance is ±0.05 mm, controlled by laser engraving to improve the anti-tearing and anti-static effects.
[0040] Example 2: Please refer to Figure 2 , A preparation method for a highly reliable in-vehicle module FPC structure in this embodiment includes the following steps:
[0041] a. Select high-quality rolled copper as the base material and design and manufacture it according to a four-layer symmetric structure;
[0042] Specifically, step a (lamination process): Use a vacuum laminator, control the pressure at 3.0 MPa (range 2.5 - 3.5 MPa), the temperature at 180 ± 5 °C, and the time at 75 min (range 60 - 90 min). Before lamination, perform plasma treatment on the surface of the rolled copper to improve adhesion. After lamination, use X-ray to detect the interlayer bonding quality to ensure no bubbles or delamination.
[0043] b. Precisely control the width and position of the copper ground wires at the edges of the upper and lower circuit layers to ensure the anti-tearing and anti-static effects;
[0044] Specifically, step b (copper ground wire control): Use a high-precision laser engraving device. Set the width of the copper ground wire to 0.8 mm (range 0.5 - 1.0 mm), the edge distance from the center of the line to be 0.2 mm, and the tolerance to be ±0.05 mm. During the engraving process, use a real-time optical detection system to detect the line width consistency every 10 cm. When the deviation exceeds 0.01 mm, automatically adjust the laser parameters.
[0045] c. Uniformly lay two layers of grid copper outside the upper and lower circuit surfaces to ensure the integrity of the shielding layer;
[0046] Specifically, step c (grid copper laying): Through an automated laying device, the grid copper density is 120 mesh / in² (range 100 - 150 mesh / in²), the coverage rate ≥ 95%, and the grid line width is 0.15 mm. After laying, conduct an electrical performance test to ensure that the resistance of the shielding layer is uniform, with a deviation < 5%.
[0047] d. Completely wrap the front and back of the FPC body with black EMI material to make it closely covered;
[0048] Specifically, step d (EMI wrapping): Adopt a hot pressing process, with a temperature of 150 °C and a holding pressure time of 30 s. Before hot pressing, pre-bake the EMI material (80 °C, 30 min) to remove moisture. After wrapping, use an infrared thermal imager to detect the coverage uniformity, with no omission areas. The EMI material completely covers the front and back of the FPC, and the thickness tolerance is ±2 μm.
[0049] e. For the cross-shaped structure at the bonding position, adopt a special processing technology to ensure the shape and dimensional accuracy;
[0050] Specifically, step e (cross-shaped structure processing): Use a five-axis CNC machine tool to process the cross-shaped structure, with a dimensional tolerance of ±0.02 mm. After processing, conduct electroplating treatment: first nickel plating (thickness 3 μm), then gold plating (thickness 0.5 μm) to improve corrosion resistance and connection reliability. The bonding strength test uses a tensile machine to ensure ≥ 49 N.
[0051] f. When processing the PIN, strictly control the retraction size to be 0.3 mm.
[0052] Specifically, step f (PIN foot processing): Adopt an ultraviolet laser cutting machine to control the retraction size of the PIN foot to be 0.3 mm (tolerance ±0.05 mm), the cutting speed is 100 mm / s, and the accuracy is 0.01 mm. After cutting, use a microscope to detect the incision quality, with no burrs or cracks. At the same time, conduct an insulation resistance test to ensure that the retraction design avoids short circuits.
[0053] Experimental data verification and comparison:
[0054] Test Project Traditional FPC This invention Increase Test Standards Shielding effectiveness (dB) 45 (1GHz) ≥60 (1GHz) ≥33% IEC61000-4-21 Bending resistance (times) 300,000 1 million 233% IPC-6013 Bond strength (N) 35 49 40% IPC-TM-650 High temperature stability (°C) 85 125 Extended to 47℃ IEC60068-2-14 Working life (years) 5-8 ≥10 ≥25% Accelerated aging test
[0055] in:
[0056] In step a, a vacuum lamination process is used, with a pressure of 2.5-3.5 MPa, a temperature of 180±5℃, and a time of 60-90 min, to ensure that there are no air bubbles in the interlayer bonding.
[0057] In step b, the copper ground wire is controlled using laser engraving technology with an accuracy of 0.01mm, and real-time optical detection is performed.
[0058] In step f, the pin indentation size is controlled within 0.3±0.05mm. Laser cutting is used, and optical inspection is performed after cutting to ensure there are no burrs or deviations.
[0059] In step d, the EMI material is wrapped using a hot-pressing process at a temperature of 150°C and a holding time of 30 seconds, and infrared thermal imaging is used to monitor the uniformity of coverage.
[0060] Furthermore, the substrate layer 1 is made of Ube UB series polyimide film from Japan, with a thickness of 30μm and a heat resistance temperature of up to 260℃; the rolled copper foil has a purity of 99.9%, a thickness of 15μm, and a conductivity of ≥58MS / m; the EMI material is a conductive carbon-filled polymer with a surface resistance of <1Ω / sq and a thickness of 15μm; the FR4 reinforcement layer 3 uses standard FR4 material with a thickness of 0.5mm to improve mechanical strength.
[0061] Example 3: Combination Figure 1 and Figure 2 Based on Examples 1 and 2, optimizations were made for extreme in-vehicle environments (such as high temperature and high humidity):
[0062] Material optimization: The substrate layer 1 is replaced with a high-temperature resistant polyimide film (35μm thick, heat resistant to 300℃); the thickness of the rolled copper layer is increased to 18μm to improve the current carrying capacity (allowing a 20% increase in current density); the EMI material is selected to be a moisture- and heat-resistant type (surface resistance <0.5Ω / sq, passes 85℃ / 85%RH test for 500 hours).
[0063] Process optimization: In step a, the vacuum lamination temperature is adjusted to 185℃ and the time is extended to 90min to ensure interlayer stability at high temperature; in step d, a secondary curing process (120℃, 60min) is added to the EMI wrapping to improve adhesion; in step f, the pin indentation size is finely adjusted to 0.32mm to compensate for high temperature expansion.
[0064] Quality control: Environmental simulation testing was added. After 1000 cycles of temperature cycling from -45℃ to 125℃, the performance degradation of FPC was <5%; under vibration testing (frequency 10-2000Hz, acceleration 5G), there was no structural damage.
[0065] This embodiment is applicable to high-end automotive display modules. Tests show that after continuous operation for 1000 hours in an environment of 125℃ / 90%RH, the shielding effectiveness remains ≥60dB and the bonding strength is ≥48N.
[0066] The above embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention shall fall within the scope of protection claimed by the present invention.
Claims
1. A high-reliability vehicle-mounted module FPC structure, characterized in that: It includes a base material layer (1), a first rolled copper layer (2), an FR4 reinforcement layer (3), a second rolled copper layer (4), a cover layer (5), an EMI shielding layer (6) and a cross-shaped bonding structure (7). The first rolled copper layer (2) and the second rolled copper layer (4) are symmetrically arranged to form a four-layer rolled copper structure, and a copper ground line is reserved around the edges of the upper and lower circuit layers. The two layers outside the upper and lower circuit surfaces are covered with grid copper.
2. The high-reliability vehicle-mounted module FPC structure according to claim 1, characterized in that: The base material layer (1) is made of polyimide film with a thickness of 25 - 50μm, having high heat resistance and flexibility. Preferably, the thickness is 30μm to adapt to the temperature changes and mechanical stresses in the vehicle-mounted environment.
3. The high-reliability vehicle-mounted module FPC structure according to claim 1, characterized in that: The thicknesses of the first rolled copper layer (2) and the second rolled copper layer (4) are both 12 - 18μm, preferably 15μm. The purity of the rolled copper is not less than 99.9%, and the conductivity is ≥58MS / m to ensure the stability and low loss of signal transmission.
4. The high-reliability vehicle-mounted module FPC structure according to claim 1, characterized in that: The EMI shielding layer (6) is a black EMI material that completely covers the front and back of the FPC body. The surface resistance is less than 1Ω / sq, and the thickness is 10 - 20μm, preferably 15μm, to achieve full-band electromagnetic shielding.
5. The high-reliability vehicle-mounted module FPC structure according to claim 1, characterized in that: The cross-shaped bonding structure (7) is located at the FPC bonding position, formed by CNC precision machining. The dimensional tolerance is ±0.02mm, and the surface is gold-plated with a gold-plating thickness of 0.5μm. The bonding strength is ≥49N to prevent loosening of the connection under vibration conditions.
6. The high-reliability vehicle-mounted module FPC structure according to claim 1, characterized in that: The laying density of the grid copper is 100 - 150 meshes / in², preferably 120 meshes / in², and the coverage rate is not less than 95%. The width of the grid line is 0.1 - 0.2mm to form a uniform shielding network and enhance the anti-interference ability.
7. The high-reliability vehicle-mounted module FPC structure according to claim 1, characterized in that: The width of the copper ground line is 0.5 - 1.0mm, the edge distance from the center of the line is 0.2mm, and the line width tolerance is ±0.05mm, which is controlled by laser engraving to improve the anti-tearing and anti-static effects.
8. A method for fabricating a high-reliability vehicle-mounted module FPC structure, characterized in that, It includes the following steps: a. Select high-quality rolled copper as the base material and design and manufacture it according to a four-layer symmetrical structure; b. Precisely control the width and position of the copper ground line at the edges of the upper and lower circuit layers to ensure the anti-tearing and anti-static effects; c. Uniformly lay grid copper on the two layers outside the upper and lower circuit surfaces to ensure the integrity of the shielding layer; d. Completely wrap the black EMI material on the front and back of the FPC body to make it tightly covered; e. For the cross-shaped structure at the bonding position, adopt a special processing technology to ensure the shape and dimensional accuracy; f. When processing the PIN, strictly control the inner shrinkage dimension to be 0.3mm.
9. The preparation method according to claim 8, characterized in that: In step a, the vacuum lamination process is adopted with a pressure of 2.5 - 3.5MPa, a temperature of 180 ± 5℃, and a time of 60 - 90min to ensure no bubbles in the interlayer bonding. In step b, the control of the copper ground line adopts laser engraving technology with an accuracy of 0.01mm, and real-time optical detection is carried out.
10. The preparation method according to claim 8, characterized in that: In step f, the inner shrinkage dimension of the PIN foot is controlled within 0.3 ± 0.05mm, and the laser cutting process is adopted. After cutting, optical detection is carried out to ensure no burrs and deviations. In step d, the wrapping of the EMI material adopts the hot pressing process with a temperature of 150℃ and a holding pressure time of 30s, and the uniformity of the coverage is monitored by infrared thermal imaging.