Rigid-flex circuit board with gradient buffer layer
By combining a gradient buffer layer and a dynamic heat dissipation structure, the problems of uneven mechanical transition and functional loss during bending of rigid-flex circuit boards are solved, resulting in a longer service life and better electromagnetic shielding.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- DIGITAL PRINTED CIRCUIT BOARD CO LTD
- Filing Date
- 2025-05-21
- Publication Date
- 2026-05-29
Smart Images
Figure CN224305990U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of circuit board technology, and in particular to a rigid-flexible circuit board with a gradient buffer layer. Background Technology
[0002] Chinese Patent Publication No. CN221634040U, published on August 30, 2024, discloses a rigid-flex printed circuit board (PCB) comprising a rigid circuit board. The rigid circuit board has a first fixing groove on its outer surface, and a second fixing groove on the side of the first fixing groove away from its opening. In this rigid-flex PCB, the first elastic plate, being slightly rigider than the flexible circuit board, has a larger bending radius when bent. When the flexible circuit board bends upwards, it follows the bending radius of the first elastic plate, thus distributing the bending force of the flexible circuit board across the first elastic plate. This avoids the flexible circuit board bending directly at the connection point with the rigid circuit board, preventing breakage at the bending point due to a small bending radius after prolonged use, which would result in a short lifespan and difficulty in long-term use. The existing technology has the following drawbacks: 1. By stacking multiple layers of elastic rubber (the first elastic plate) and TPU plastic (the second elastic plate), and utilizing the hardness gradient of the elastic materials to disperse stress, the mechanical transition is not smooth enough, affecting the bending life; 2. It lacks heat dissipation and electromagnetic shielding functions, reducing its service life. Given this situation, improvements are urgently needed. Utility Model Content
[0003] Based on this, the purpose of this utility model is to provide a rigid-flexible circuit board with a gradient buffer layer, which has a smooth mechanical transition, improves bending life, and has heat dissipation and electromagnetic shielding functions, thereby improving service life.
[0004] This utility model provides a rigid-flexible integrated circuit board with a gradient buffer layer, including a rigid circuit board and a flexible circuit board. The rigid circuit board has stepped perforated grooves on its surface. The bonding area between the rigid circuit board and the flexible circuit board is constructed in the following order: gradient buffer layer, dynamic heat dissipation structure, and electromagnetic shielding skin. The gradient buffer layer covers the entire bonding area surface of the rigid circuit board, including the ungrooved solid area and the inner and outer edges of the perforated grooves, and from the inside out includes: a metal support layer, a conductive soft adhesive layer, and a wave-shaped groove layer. The surface of the wave-shaped groove layer is formed with biomimetic wave grooves by laser direct writing. A heat dissipation structure is laid flat above the gradient buffer layer, including a microfluidic substrate, a phase change heat storage material layer, and thermally conductive vias; an electromagnetic shielding skin three-dimensionally covers the entire outer surface of the bonding area, including, from the outside to the inside: a braided shielding layer, a wave-absorbing medium layer, and a conductive adhesive layer; the copper conductors of the flexible circuit board extend to the outside of the rigid circuit board through a corrugated groove, and a plug-in mechanism is provided at the exposed end of the flexible circuit board. The plug-in mechanism includes a gold-plated nickel boss provided on the rigid circuit board and a stainless steel groove provided at the exposed end of the flexible circuit board, and the stainless steel groove is filled with copper-doped conductive silicone.
[0005] Preferably, the depth of the stepped hollow groove is 30-50% of the thickness of the rigid board, the inner edge of the groove is formed with a 45°±2° chamfer by laser cutting, and the width of the groove matches the width of the bending area of the flexible circuit board with a gap ≤0.2mm.
[0006] Preferably, the metal support layer is a Ni-Ti shape memory alloy sheet with a thickness of 0.05-0.1mm, which is connected to the copper foil of the rigid circuit board by laser micro-soldering points;
[0007] The conductive soft adhesive layer is a polyurethane / silicone composite layer with a thickness of 0.2-0.5 mm, and a 45° cross-arranged silver nanowire honeycomb grid is embedded inside; the ratio of the peak spacing of the wavy groove to the side length of the silver nanowire honeycomb grid is 1:1.2-1:1.5, and the inner surface of the wavy groove is coated with KH550 silane coupling agent to form a chemical bond with the flexible board copper wire.
[0008] The thickness of the corrugated groove layer is set to 0.3-0.8 mm Fe. 3+ - A PDMS elastomer layer, the surface of which is formed with biomimetic wave grooves by laser direct writing. The groove depth is 30-50% of the layer thickness, extending into the stepped hollow groove and forming a mechanical interlock with the copper wires of the flexible circuit board. The fitting depth is ≥50% and the fitting accuracy is ±0.02mm.
[0009] Preferably, the microchannel substrate is a 0.3-0.5mm thick polyimide plate with serpentine microchannels etched on its surface, and a U-shaped bend is provided at the root of the exposed working area to avoid thermal stress; the phase change thermal storage material layer is a paraffin / graphene composite filling the microchannels with a thermal conductivity ≥15W / mK; the thermally conductive vias are blind vias with a diameter ≤50μm, connecting the microchannels to the copper layer of the rigid circuit board, with a copper plating thickness ≥10μm; the radius of curvature R of the U-shaped bend is 0.5-1.0mm, the bending angle θ is 90°-120°, and the distance between the bend and the exposed area of the flexible board is ≥0.3mm.
[0010] Preferably, the woven shielding layer is made of 45° twill copper-plated aramid fiber cloth with a single filament diameter of 12-15μm, and a honeycomb-shaped metal grid window is opened in the exposed area of the flexible circuit board with a grid side length of 0.3mm; the absorbing medium layer is made of FeSiAl / epoxy resin layer, with FeSiAl flake powder having an aspect ratio ≥10:1 and magnetically oriented alignment; the conductive adhesive layer is made of AgNWs / PDMS adhesive layer, bonded to the corrugated slot layer by vacuum hot pressing; the opening area of the honeycomb-shaped metal grid window accounts for 30-50%, the gold plating thickness of the grid edge is ≥0.5μm, and a SiO2 protective layer with a thickness of 50nm±5nm is coated by nano-sealing process; the copper powder of the copper-doped conductive silicone has a copper powder particle size of 5-10μm, a volume percentage of 30-50%, a Shore hardness of 40-60A, and a volume resistivity ≤1×10⁻⁶. -3 Ω·cm, copper powder distribution uniformity deviation ≤5%.
[0011] Preferably, the exposed area of the flexible circuit board is ≤15mm in length, the conductors are serpentine with wavelength λ=2mm and amplitude A=0.5mm; the height of the gold-plated nickel boss is 0.3-0.6mm with a tolerance of ±0.01mm; and the depth of the stainless steel groove is 0.35-0.7mm.
[0012] The beneficial effects of this utility model are as follows: Through the gradient buffer layer, including the metal support layer, the conductive soft rubber layer, and the corrugated groove layer, a transition between rigidity and flexibility is achieved. The corrugated groove and the flexible circuit board are mechanically interlocked, resulting in a smoother mechanical transition and improved bending life. The microfluidic channel of the dynamic heat dissipation structure uses phase change material, and combined with the electromagnetic shielding skin, a three-dimensional full enclosure is achieved, which reduces thermal resistance and also achieves electromagnetic shielding function, thus improving service life. Attached Figure Description
[0013] Figure 1 This is a cross-sectional view of the present invention.
[0014] Figure 2 This is a cross-sectional view of the gradient buffer layer.
[0015] Figure 3 This is a cross-sectional view of the electromagnetic shielding skin.
[0016] The attached figures are labeled as follows: rigid circuit board 10, flexible circuit board 12, stepped hollow groove 11, dynamic heat dissipation structure 14, gradient buffer layer 13, electromagnetic shielding skin 15, metal support layer 19, conductive soft adhesive layer 18, wavy card slot layer 17, gold-plated nickel boss 16, braided shielding layer 22, wave-absorbing medium layer 21, conductive adhesive layer 20, and chamfer 23. Detailed Implementation
[0017] To further understand the features, technical means, and specific objectives and functions achieved by this utility model, the following detailed description of this utility model is provided in conjunction with specific embodiments and accompanying drawings.
[0018] In this utility model, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., 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; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.
[0019] Please refer to Figure 1-3 As shown, this utility model provides a rigid-flex circuit board with a gradient buffer layer, including a rigid circuit board 10 and a flexible circuit board 12. The rigid circuit board 10 has stepped perforated grooves 11 on its surface. The bonding area between the rigid circuit board 10 and the flexible circuit board 12 is constructed in the following order: gradient buffer layer 13, dynamic heat dissipation structure 14, and electromagnetic shielding skin 15. The gradient buffer layer 13 covers the entire bonding area surface of the rigid circuit board 10, including the ungrooved solid area and the inner and outer edges of the perforated grooves 11. From the inside out, it includes: a metal support layer 19, a conductive soft adhesive layer 18, and a wavy groove layer 17. The surface of the wavy groove layer 17 is formed by laser direct writing to resemble... A wave-shaped groove is formed; a dynamic heat dissipation structure 14 is laid flat on top of the gradient buffer layer 13, including a microfluidic substrate, a phase change heat storage material layer, and thermally conductive vias; an electromagnetic shielding skin 15 three-dimensionally covers the entire outer surface of the bonding area, including, from the outside to the inside: a braided shielding layer 22, a wave-absorbing medium layer 21, and a conductive adhesive layer 20; the copper conductors of the flexible circuit board 12 extend to the outside of the rigid circuit board through the wave-shaped groove, and a plug-in mechanism is provided at the exposed end of the flexible circuit board 12. The plug-in mechanism includes a gold-plated nickel boss 16 provided on the rigid circuit board 10 and a stainless steel groove provided at the exposed end of the flexible circuit board 12. The stainless steel groove is filled with copper-doped conductive silicone.
[0020] The depth of the stepped hollow groove 11 is 30-50% of the thickness of the rigid board. The inner edge of the groove is formed by laser cutting to form a 45°±2° chamfer 23. The width of the groove matches the width of the bending area of the flexible circuit board 12 and the gap is ≤0.2mm.
[0021] The metal support layer 19 is a Ni-Ti shape memory alloy sheet with a thickness of 0.05-0.1mm, which is connected to the copper foil of the rigid circuit board 10 by laser micro solder joints;
[0022] The conductive soft adhesive layer 18 is a polyurethane / silicone composite layer with a thickness of 0.2-0.5 mm, and is embedded with a 45° cross-arranged silver nanowire honeycomb grid. The ratio of the peak spacing of the wavy groove to the side length of the silver nanowire honeycomb grid is 1:1.2-1:1.5. The inner surface of the wavy groove is coated with KH550 silane coupling agent to form a chemical bond with the copper wire of the flexible board.
[0023] The thickness of the corrugated card slot layer 17 is set to 0.3-0.8 mm of Fe. 3+ -PDMS elastomer layer, the surface of which is formed by laser direct writing to form biomimetic wave grooves, the groove depth is 30-50% of the layer thickness, extending into the stepped hollow groove 11 and forming a mechanical interlock with the copper wires of the flexible circuit board (12), the fitting depth is ≥50% and the fitting accuracy is ±0.02mm.
[0024] Preferably, the microchannel substrate is a 0.3-0.5mm thick polyimide plate with serpentine microchannels etched on its surface, and a U-shaped bend is provided at the root of the exposed working area to avoid thermal stress; the phase change heat storage material layer is a paraffin / graphene composite filling the microchannels with a thermal conductivity ≥15W / mK; the thermally conductive vias are blind vias with a diameter ≤50μm, which connect the microchannels to the copper layer of the rigid circuit board 10, with a copper plating thickness ≥10μm; the radius of curvature R of the U-shaped bend is 0.5-1.0mm, the bending angle θ is 90°-120°, and the distance between the bend and the exposed area of the flexible board is ≥0.3mm.
[0025] The braided shielding layer is made of 45° twill copper-plated aramid fiber cloth with a single filament diameter of 12-15μm. A honeycomb-shaped metal grid window is opened in the exposed area of the flexible circuit board 12, with a grid side length of 0.3mm. The absorbing dielectric layer is a FeSiAl / epoxy resin layer, with FeSiAl flake powder having an aspect ratio ≥10:1 and magnetically oriented alignment. The conductive adhesive layer is an AgNWs / PDMS adhesive layer, bonded to the corrugated slot layer via vacuum hot pressing. The opening area of the honeycomb-shaped metal grid window accounts for 30-50%, the gold plating thickness at the grid edges is ≥0.5μm, and a SiO2 protective layer with a thickness of 50nm±5nm is coated using a nano-sealing process. The copper powder in the copper-doped conductive silicone has a particle size of 5-10μm, a volume percentage of 30-50%, a Shore hardness of 40-60A, and a volume resistivity ≤1×10⁻⁶. -3Ω·cm, copper powder distribution uniformity deviation ≤5%.
[0026] The exposed area of the flexible circuit board 12 has a length ≤15mm, the conductors are serpentine, the wavelength λ=2mm, and the amplitude A=0.5mm; the height of the gold-plated nickel boss 16 is 0.3-0.6mm, with a tolerance of ±0.01mm; the depth of the stainless steel groove is 0.35-0.7mm.
[0027] In this embodiment, a gradient buffer layer, including a metal support layer, a conductive soft adhesive layer, and a corrugated groove layer, is used to achieve a transition between rigidity and flexibility. The corrugated groove is mechanically interlocked with the flexible circuit board, resulting in a smoother mechanical transition and improved bending life. The microfluidic channel of the dynamic heat dissipation structure, combined with phase change material and electromagnetic shielding skin, achieves three-dimensional full enclosure, which reduces thermal resistance and achieves electromagnetic shielding function, thus improving service life.
[0028] The above-described embodiments are merely one implementation of this utility model, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this utility model patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this utility model, and these all fall within the protection scope of this utility model. Therefore, the protection scope of this utility model patent should be determined by the appended claims.
Claims
1. A rigid-flex circuit board with a gradient buffer layer, comprising a rigid circuit board (10) and a flexible circuit board (12), characterized in that: The rigid circuit board (10) has stepped hollow grooves (11) on its surface. The bonding area between the rigid circuit board (10) and the flexible circuit board (12) is constructed in the following order: gradient buffer layer (13), dynamic heat dissipation structure (14), and electromagnetic shielding skin (15). The gradient buffer layer (13) covers the entire bonding area of the rigid circuit board (10), including the ungrooved solid area and the inner and outer edges of the hollow grooves (11), and includes, from the inside to the outside: metal support layer (19), conductive soft adhesive layer (18), and wave groove layer (17). The surface of the wave groove layer (17) is formed by laser direct writing to create biomimetic wave grooves. The dynamic heat dissipation structure (14) is laid flat on the surface of the flexible circuit board (12). Above the gradient buffer layer (13), there are microfluidic substrates, phase change heat storage material layers, and thermally conductive vias; the electromagnetic shielding skin (15) covers the entire outer surface of the bonding area in three dimensions, and from the outside to the inside, it includes: a braided shielding layer (22), a wave-absorbing medium layer (21), and a conductive adhesive layer (20); the copper wires of the flexible circuit board (12) extend to the outside of the rigid circuit board through the wave grooves, and the exposed area of the flexible circuit board (12) is provided with a plug-in mechanism, which includes a gold-plated nickel boss (16) provided on the rigid circuit board (10) and a stainless steel groove provided at the exposed area of the flexible circuit board (12), and the stainless steel groove is filled with copper-doped conductive silicone.
2. The rigid-flexible circuit board with a gradient buffer layer according to claim 1, characterized in that: The stepped hollow groove (11) has a groove depth of 30-50% of the thickness of the hard board. The inner edge of the groove is formed by laser cutting to form a 45°±2° chamfer (23). The groove width matches the width of the bending area of the flexible circuit board (12) and the gap is ≤0.2mm.
3. A rigid-flexible circuit board with a gradient buffer layer according to claim 1, characterized in that: The metal support layer (19) is a Ni-Ti shape memory alloy sheet with a thickness of 0.05-0.1mm, which is connected to the copper foil of the rigid circuit board (10) by laser micro soldering points; The conductive soft adhesive layer (18) is a polyurethane / silicone composite layer with a thickness of 0.2-0.5 mm, and is embedded with a 45° cross-arranged silver nanowire honeycomb grid; the ratio of the peak spacing of the wavy groove to the side length of the silver nanowire honeycomb grid is 1:1.2-1:1.5, and the inner surface of the wavy groove is coated with KH550 silane coupling agent to form a chemical bond with the flexible copper wire; The thickness of the corrugated groove layer (17) is set to 0.3-0.8 mm of Fe. 3+ -PDMS elastomer layer, the surface of which is formed with biomimetic wave grooves by laser direct writing, the groove depth is 30-50% of the layer thickness, extending into the stepped hollow groove (11) and forming a mechanical interlock with the copper wires of the flexible circuit board (12), with an interlocking depth ≥50% and an interlocking accuracy of ±0.02mm.
4. A rigid-flexible circuit board with a gradient buffer layer according to claim 1, characterized in that: The microchannel substrate is a 0.3-0.5mm thick polyimide plate with serpentine microchannels etched on its surface. A U-shaped bend is provided at the root of the exposed working area to avoid thermal stress. The phase change heat storage material layer is a paraffin / graphene composite filling the microchannels with a thermal conductivity ≥15W / mK. The thermally conductive vias are blind holes with a diameter ≤50μm, which connect the microchannels to the copper layer of the rigid circuit board (10) with a copper plating thickness ≥10μm. The radius of curvature R of the U-shaped bend is 0.5-1.0mm, the bending angle θ is 90°-120°, and the distance between the bend and the exposed area of the flexible board is ≥0.3mm.
5. A rigid-flexible circuit board with a gradient buffer layer according to claim 1, characterized in that: The woven shielding layer is made of 45° twill copper-plated aramid fiber cloth with a single filament diameter of 12-15μm. A honeycomb metal grid window is opened in the exposed area of the flexible circuit board (12), with a grid side length of 0.3mm. The absorbing medium layer is made of FeSiAl / epoxy resin layer, with FeSiAl flake powder having an aspect ratio ≥10:1 and magnetic field orientation. The conductive adhesive layer is made of AgNWs / PDMS adhesive layer, which is bonded to the corrugated card slot layer by vacuum hot pressing. The opening area of the honeycomb metal grid window accounts for 30-50%, the gold plating thickness of the grid edge is ≥0.5μm, and a SiO2 protective layer with a thickness of 50nm±5nm is coated by nano-sealing process. The copper powder of the copper-doped conductive silicone has a particle size of 5-10μm, a volume percentage of 30-50%, a Shore hardness of 40-60A, and a volume resistivity ≤1×10 -3 Ω·cm, copper powder distribution uniformity deviation ≤5%.
6. A rigid-flexible circuit board with a gradient buffer layer according to claim 1, characterized in that: The exposed area of the flexible circuit board (12) is ≤15mm in length, the conductors are serpentine, the wavelength λ=2mm, and the amplitude A=0.5mm; the height of the gold-plated nickel boss (16) is 0.3-0.6mm, with a tolerance of ±0.01mm; the depth of the stainless steel groove is 0.35-0.7mm.