Stretchable circuit board and method of making the same

Abstract

In order to overcome the problems of large impedance and insufficient service life of the existing stretchable circuit board, the present application provides a stretchable circuit board and a preparation method thereof, the stretchable circuit board comprises an elastic substrate and an elastic packaging layer, the elastic packaging layer covers one side surface of the elastic substrate, one side of the elastic substrate towards the elastic packaging layer is formed with a fiber reinforced area, the fiber reinforced area is provided with a glass fiber layer penetrating in the elastic substrate, the fiber reinforced area is provided with a circuit slot, the glass fiber layer is partially penetrated in the circuit slot, the circuit slot is filled with a liquid metal coating, and a circuit pattern is formed by the liquid metal coating in the circuit slot.

Description

Technical Field

[0001] This invention belongs to the field of circuit board technology, specifically relating to a stretchable circuit board and its preparation method. Background Technology

[0002] With the rapid development of flexible electronics, wearable devices and intelligent robots, higher requirements are placed on the deformation adaptability of circuit boards. They not only need to have bending characteristics to adapt to curved surface installation scenarios, but also need to achieve a certain degree of tensile performance to meet the deformation needs of the equipment during dynamic operation.

[0003] Currently, most flexible circuit boards use polyimide as the substrate material, which is widely used in the field of flexible electronics due to its excellent insulation properties, heat resistance, and mechanical strength. However, the molecular chain structure of polyimide substrates determines that it can only achieve limited bending deformation and has extremely poor tensile properties. This has obvious limitations in applications that require stretching and adaptation, and cannot meet the needs of dynamic deformation of equipment.

[0004] To overcome this limitation, a stretchable circuit board has been proposed in related technologies. This circuit board uses an elastically deformable elastomer (such as silicone rubber, polyurethane, etc.) as a substrate, and liquid metal circuits are set on the surface or inside of the elastomer substrate. By combining the elastic deformation capability of the elastomer substrate with the flow deformation characteristics of liquid metal, the stretchability of the circuit board is achieved, which expands the application scenarios of the circuit board to a certain extent.

[0005] However, this type of stretchable circuit board based on liquid metal and elastomer still has significant drawbacks: Firstly, liquid metal is in a fluid state at room temperature, making it difficult to maintain a stable shape. Especially after being energized, the viscosity of the liquid metal decreases and its fluidity increases as the circuit heats up. This causes it to aggregate under surface tension, resulting in a reduction in the conductive area of ​​some circuit locations and a significant increase in circuit impedance. This problem makes it difficult for this type of circuit board to adapt to the signal transmission stability requirements of complex circuit layouts, and it also cannot meet the conductivity requirements of high-current load scenarios. Secondly, the circuit board has poor tensile fatigue resistance. During repeated stretching and recovery cycles, the liquid metal circuitry easily forms weak areas due to uneven deformation. The stretching and recovery process further promotes the aggregation and contraction of the liquid metal, leading to a continuous increase in circuit impedance and ultimately causing an open circuit failure. Furthermore, each stretching and recovery cycle exacerbates the aggregation of liquid metal, significantly increasing the risk of circuit breakage and severely affecting the service life and reliability of the circuit board. Summary of the Invention

[0006] To address the problems of high impedance and insufficient lifespan of existing stretchable circuit boards, this invention provides a stretchable circuit board and its manufacturing method.

[0007] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows:

[0008] On one hand, the present invention provides a stretchable circuit board, including an elastic substrate and an elastic encapsulation layer. The elastic encapsulation layer covers one side surface of the elastic substrate. A fiber reinforcement region is formed on the side of the elastic substrate facing the elastic encapsulation layer. A glass fiber layer is disposed in the fiber reinforcement region and inserted into the elastic substrate. A circuit groove is formed in the fiber reinforcement region. The glass fiber layer is partially inserted into the circuit groove. The circuit groove is filled with a liquid metal coating, and a circuit pattern is formed by the liquid metal coating in the circuit groove.

[0009] Optionally, the elastic substrate is one or more of hydrogenated styrene-butadiene block copolymer and polydimethylsiloxane; and / or,

[0010] The elastic encapsulation layer is one or more of hydrogenated styrene-butadiene block copolymer, polydimethylsiloxane, polyester elastomer, and polyurethane elastomer.

[0011] Optionally, the fiber layer is selected from chopped glass fibers or glass fiber mesh.

[0012] Optionally, the width of the line groove is 50~600μm and the depth of the line groove is 50~200μm.

[0013] Optionally, the liquid metal coating is prepared from a liquid metal paint, which comprises the following components by weight:

[0014] The composition includes 40-60 parts liquid metal, 10-30 parts filler, 6-22.4 parts bonding resin, 0.5-2 parts 3-aminopropyltriethoxysilane, 0.1-0.2 parts citric acid, and 10-15 parts solvent.

[0015] Optionally, the liquid metal is selected from a gallium-indium-zinc alloy, wherein the mass ratio of gallium, indium, and zinc is (60~76):(16~25):(0.5~2); and / or,

[0016] The filler is selected from one or more of alumina and silica; and / or,

[0017] The bonding resin is selected from one or more of epoxy resin and polyurethane; and / or,

[0018] The solvent is selected from one or more of n-decane, toluene, and cyclohexane.

[0019] Optionally, it also includes a metal pin, one end of which is located between the elastic substrate and the elastic encapsulation layer, one end of which is electrically connected to the circuit groove, and the other end of which extends out of the elastic substrate and the elastic encapsulation layer.

[0020] Another embodiment of the present invention provides a method for manufacturing the stretchable circuit board as described above, comprising the following steps:

[0021] S1. Provide an elastomer prepolymer, lay a glass fiber layer on one side surface of the elastomer prepolymer, apply a vacuum, and after the elastomer prepolymer has fully impregnated the glass fiber layer, cure the elastomer prepolymer to obtain an elastic substrate and a fiber-reinforced region formed on one side of the elastic substrate.

[0022] S2. A laser is used to ablate the fiber-reinforced area according to the required circuit pattern to form a circuit groove, in which a glass fiber layer is retained.

[0023] S3. Liquid metal coating is printed at the corresponding position of the circuit groove and cured to obtain the circuit pattern;

[0024] S4. Encapsulate the surface of the circuit pattern to form a flexible encapsulation layer.

[0025] Optionally, the ablation process uses a CO2 laser with a laser power density of 0.9~1.95 W / cm². 2 The scanning speed is 200~600mm / s.

[0026] Optionally, after laser ablation, the side of the elastic substrate with the circuit groove is subjected to plasma surface treatment.

[0027] The stretchable circuit board provided by this invention, with a glass fiber layer inserted into the elastic substrate and the circuit grooves, enhances the overall structural strength and deformation uniformity of the substrate. By creating circuit grooves in the fiber-reinforced region of the elastic substrate, the circuit grooves physically constrain the liquid metal coating, while the glass fiber layer anchors the liquid metal coating, effectively suppressing the aggregation tendency of the liquid metal due to surface tension, hindering its aggregation and shrinkage, avoiding a reduction in local electrical conductivity area, and significantly reducing circuit impedance. During the stretching recovery process, the stability of the electrical conductivity area in the circuit grooves is also ensured, reducing the risk of circuit breakage in each deformation cycle, extending the lifespan and reliability of the circuit board, and meeting the stability requirements of complex circuit signal transmission and high current loads. Simultaneously, the integration of the circuit grooves and the glass fiber layer in the fiber-reinforced region ensures the consistency of the circuit pattern with the elastic substrate's shape under stretching, avoiding the problem of tensile stress concentration. An elastic encapsulation layer covers the surface of the elastic substrate, further encapsulating and fixing the liquid metal coating within the circuit grooves. Combined with the supporting effect of the fiber-reinforced region, this achieves a synergistic improvement in stretchability and structural stability. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the structure of the stretchable circuit board provided by the present invention;

[0029] Figure 2 This is a flowchart illustrating the fabrication process of the stretchable circuit board provided by the present invention.

[0030] The reference numerals in the accompanying drawings are as follows:

[0031] 1. Elastic substrate; 1a. Elastomer prepolymer; 11. Fiber-reinforced region; 111. Glass fiber layer; 112. Circuit groove; 113. Liquid metal coating; 2. Elastic encapsulation layer; 3. Metal leads. Detailed Implementation

[0032] To make the technical problems solved, technical solutions, and beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0033] like Figure 1As shown, an embodiment of the present invention provides a stretchable circuit board, including an elastic substrate 1 and an elastic encapsulation layer 2. The elastic encapsulation layer 2 covers one side surface of the elastic substrate 1. A fiber reinforcement region 11 is formed on the side of the elastic substrate 1 facing the elastic encapsulation layer 2. A glass fiber layer 111 is disposed in the fiber reinforcement region 11 and passes through the elastic substrate 1. A circuit groove 112 is formed in the fiber reinforcement region 11. The glass fiber layer 111 is partially disposed in the circuit groove 112. The circuit groove 112 is filled with a liquid metal coating 113, and a circuit pattern is formed by the liquid metal coating 113 in the circuit groove 112.

[0034] According to the stretchable circuit board provided by the present invention, the glass fiber layer 111, which is disposed in the elastic substrate 1 and the circuit groove 112, can enhance the overall structural strength and deformation uniformity of the substrate. By opening the circuit groove 112 in the fiber reinforcement region 11 of the elastic substrate 1, the circuit groove 112 forms a physical constraint on the liquid metal coating 113. At the same time, the glass fiber layer 111 anchors the liquid metal coating 113, effectively suppressing the aggregation tendency of the liquid metal due to surface tension, preventing its aggregation and shrinkage, avoiding the reduction of local electrical conduction area, and significantly reducing the circuit impedance. During the stretch recovery process, the stability of the electrical conduction area in the circuit groove 112 can also be guaranteed, reducing the risk of circuit breakage in each deformation cycle, extending the service life and reliability of the circuit board, and meeting the requirements of complex circuit signal transmission stability and high current load. At the same time, the circuit groove 112 and the glass fiber layer of the fiber reinforcement region 11 are integrated, which can ensure the consistency of the circuit pattern with the shape of the elastic substrate 1 when stretched, avoiding the problem of tensile stress concentration. The elastic encapsulation layer 2 covers the surface of the elastic substrate 1, further encapsulating and fixing the liquid metal coating 113 in the circuit groove 112. Combined with the supporting role of the fiber reinforcement area 11, it achieves a synergistic improvement in stretchability and structural stability.

[0035] In some embodiments, the thickness of the glass fiber layer 111 is 50~200μm.

[0036] In some embodiments, the cross-sectional shape of the line groove 112 is trapezoidal or U-shaped.

[0037] In some embodiments, the elastic substrate 1 is one or more of hydrogenated styrene-butadiene block copolymer and polydimethylsiloxane.

[0038] In some embodiments, the elastic encapsulation layer 2 is one or more of hydrogenated styrene-butadiene block copolymer, polydimethylsiloxane, polyester elastomer, and polyurethane elastomer.

[0039] The elastic substrate 1 materials, such as hydrogenated styrene-butadiene block copolymer and polydimethylsiloxane, have both excellent elastic deformation capability and chemical stability. Their molecular structure characteristics can form a good wetting bond with the glass fiber layer 111, ensuring the structural strength of the fiber reinforcement region 11. The above-mentioned materials selected for the elastic encapsulation layer 2 have good compatibility with the elastic substrate 1 and the liquid metal coating 113, and can form a tight encapsulation interface, reducing the risk of interlayer delamination during deformation.

[0040] In some embodiments, when the elastic substrate 1 and the elastic encapsulation layer 2 are made of different materials, the difference in their glass transition temperatures does not exceed 20°C, so as to avoid peeling caused by the difference in interlayer shrinkage due to temperature changes.

[0041] In some embodiments, the fiber layer is selected from chopped glass fibers or glass fiber mesh.

[0042] Short glass fiber can be evenly dispersed in the fiber reinforcement area 11 to achieve uniform reinforcement of the substrate and avoid uneven local deformation; the glass fiber mesh cloth forms continuous support with its mesh structure and efficiently transmits stress when stretched. Both fiber forms can specifically improve the deformation resistance of the circuit groove 112 and the liquid metal circuit, and further suppress the accumulation of liquid metal.

[0043] In some embodiments, the chopped glass fibers have a length of 0.5-3 mm and a diameter of 5-15 μm, and their volume fraction in the fiber-reinforced region 11 is 15%-30%, which can achieve uniform reinforcement of the substrate. In some embodiments, the glass fiber mesh has a mesh count of 200-400 mesh, a single fiber diameter of 8-20 μm, a mesh aperture of 50-100 μm, and the mesh lines form a 45° angle with the extension direction of the line groove 112, which can more efficiently disperse stress during stretching.

[0044] In some embodiments, the width of the line groove 112 is 50~600μm, and the depth of the line groove 112 is 50~200μm.

[0045] This size range matches the precision of laser ablation processing and liquid metal coating printing process, ensuring the forming quality of the circuit groove 112 and the fullness of coating filling, and reducing processing defects or performance risks caused by improper dimensions.

[0046] In some embodiments, the spacing between adjacent line slots 112 is 1.5 to 3 times the width of the line slot 112, and the spacing is not less than 100 μm, to avoid signal interference between lines or liquid metal penetration.

[0047] In some embodiments, the liquid metal coating 113 is prepared from a liquid metal paint, which comprises the following components by weight:

[0048] The composition includes 40-60 parts liquid metal, 10-30 parts filler, 6-22.4 parts bonding resin, 0.5-2 parts 3-aminopropyltriethoxysilane, 0.1-0.2 parts citric acid, and 10-15 parts solvent.

[0049] The bonding resin can firmly bond the liquid metal particles to the filler and form a strong adhesion with the inner wall of the circuit groove 112 and the glass fiber layer 111, thus inhibiting the accumulation of liquid metal from the chemical bonding level.

[0050] Fillers can enhance the mechanical strength of coatings and improve their resistance to tensile deformation.

[0051] Furthermore, in order to improve the wettability of the liquid metal coating with the glass fiber layer 111 in the circuit groove 112, 3-aminopropyltriethoxysilane is added to the liquid metal coating. 3-aminopropyltriethoxysilane has siloxane groups, which can form siloxane bonds with glass fibers through hydrolysis and condensation. At the same time, the amino groups on 3-aminopropyltriethoxysilane can chelate with metals such as gallium and indium in the liquid metal, thereby effectively adsorbing some of the liquid metal onto the surface of the glass fiber. This inhibits the aggregation of liquid metal on the one hand, and utilizes the glass fiber to achieve the ductility and stability of conductivity on the other hand.

[0052] The liquid metal in the liquid metal coating is easily oxidized in the air to form gallium oxide and indium oxide, which is not conducive to the wetting of the liquid metal coating and the glass fiber layer 111 in the circuit groove 112. By adding citric acid to the liquid metal coating, which is a reducing weak acid, the formation of gallium oxide and indium oxide in the liquid metal coating can be reduced, thereby ensuring that the liquid metal coating fully adheres to the glass fiber layer 111 during operation.

[0053] In some embodiments, the liquid metal is selected from gallium-indium-zinc alloy, wherein the mass ratio of gallium, indium, and zinc is (60~76):(16~25):(0.5~2).

[0054] The mass ratio of gallium to indium enables the liquid metal to exhibit liquid properties at room temperature, thereby ensuring the stability of its electrical conductivity and good recovery ability during tensile deformation. The addition of zinc to the liquid metal can suppress the formation of gallium oxide and indium oxide on its surface and improve the wettability of the liquid metal with the glass fiber layer 111.

[0055] In some embodiments, the filler is selected from one or more of alumina and silicon dioxide.

[0056] Alumina and silica fillers have high hardness and good compatibility with resin, which can effectively enhance the strength of the coating.

[0057] In some embodiments, the adhesive resin is selected from one or more of epoxy resin and polyurethane.

[0058] Epoxy resin and polyurethane have strong adhesion and are suitable for elastic substrate material 1.

[0059] In some embodiments, the solvent is selected from one or more of n-decane, toluene, and cyclohexane.

[0060] Solvents such as n-decane have excellent solubility, which can ensure uniform dispersion of the coating and ensure consistent coating quality after printing.

[0061] In some embodiments, a metal pin 3 is further included, one end of which is located between the elastic substrate 1 and the elastic encapsulation layer 2, one end of which is electrically connected to the circuit groove 112, and the other end of which extends out of the elastic substrate 1 and the elastic encapsulation layer 2.

[0062] In some embodiments, the metal pin 3 is made of brass or nickel alloy, with a tin or gold plating layer thickness of 3~10μm to improve conductivity and corrosion resistance.

[0063] In some embodiments, the end of the metal pin 3 located between the elastic substrate 1 and the encapsulation layer is flat, with a width 1.2 to 1.5 times the width of the wiring groove 112, a length of 5 to 10 mm, and a contact area with the liquid metal coating 113 ≥ 0.5 mm². 2 This reduces contact resistance.

[0064] In some embodiments, the metal pin 3 extends to a length of 3-8 mm and has a bent structure at the end with a bending angle of 90° to facilitate docking with connectors of external devices.

[0065] The extended metal pins 3 facilitate the connection between the circuit board and external devices, and the connection method is adapted to the stretchable characteristics of the circuit board, so that the connection stability will not be compromised due to deformation, thus expanding the application adaptability of the circuit board in wearable devices and other scenarios.

[0066] like Figure 2 As shown, another embodiment of the present invention provides a method for manufacturing the stretchable circuit board as described above, comprising the following steps:

[0067] S1. Provide an elastomer prepolymer, lay a glass fiber layer on one side surface of the elastomer prepolymer, apply a vacuum, and after the elastomer prepolymer has fully impregnated the glass fiber layer, cure the elastomer prepolymer to obtain an elastic substrate and a fiber-reinforced region formed on one side of the elastic substrate.

[0068] S2. A laser is used to ablate the fiber-reinforced area according to the required circuit pattern to form a circuit groove, in which a glass fiber layer is retained.

[0069] S3. Liquid metal coating is printed at the corresponding position of the circuit groove and cured to obtain the circuit pattern;

[0070] S4. Encapsulate the surface of the circuit pattern to form a flexible encapsulation layer.

[0071] The process of impregnating the glass fiber layer with an elastomer prepolymer and then curing it ensures a tight bond between the glass fiber layer and the elastic substrate, avoiding reinforcement failure caused by interlayer voids; laser ablation preserves the glass fiber layer in the circuit groove, precisely achieving anchoring support for the liquid metal coating.

[0072] In some embodiments, in step S1, when the elastomer prepolymer is selected from polydimethylsiloxane prepolymer, the curing temperature is 100~120℃ and the time is 1~2h to ensure that the substrate is fully cured and formed.

[0073] In some embodiments, the ablation process uses a CO2 laser with a laser power density of 0.9~1.95 W / cm². 2 The scanning speed is 200~600mm / s.

[0074] In laser ablation, since the resin ablation temperature of the elastomer is much lower than the pyrolysis temperature of the glass fiber, the elastic substrate can be fully ablated while the glass fiber layer is preserved by controlling the power density and scanning speed of the laser.

[0075] Within the range of laser power density and scanning speed, the elastic substrate can be efficiently ablated to form a circuit groove, and the dimensional accuracy of the groove can be precisely controlled to avoid excessive ablation that damages the glass fiber layer or insufficient ablation that results in an incomplete groove shape. In some embodiments, when a single ablation is insufficient to achieve the expected circuit groove depth, multiple ablation processes can be performed.

[0076] In some embodiments, after laser ablation, the side of the elastic substrate with the circuit groove is subjected to plasma surface treatment.

[0077] Plasma surface treatment can further clean impurities generated by laser ablation in the glass fiber layer of the circuit groove, and introduce active functional groups, significantly improving the adhesion of liquid metal coating to the circuit groove wall and glass fiber layer, avoiding the coating from peeling off from the substrate during tensile deformation, and further inhibiting the accumulation of liquid metal.

[0078] In some embodiments, the plasma surface treatment uses a mixture of argon and oxygen in a volume ratio of (3~5):1, a gas flow rate of 10~20L / min, and a processing power of 100~200W.

[0079] In some embodiments, the plasma treatment time is 30-60 seconds and the treatment distance is 5-10 mm. After treatment, the contact angle of the elastic substrate surface is reduced to below 30°, which significantly improves the wettability with liquid metal coatings.

[0080] In some embodiments, the printing method in step S3 is screen printing, with a screen mesh count of 100~200 mesh, a squeegee hardness of 60~80A, a printing pressure of 0.1~0.3MPa, and curing conditions of 80~100℃ for 1~2h.

[0081] In some embodiments, step S3 further includes placing the metal pins on the edge surface of the elastic substrate and bringing the metal pin portions into contact with the liquid metal coating in the circuit groove. During packaging in step S4, the metal pins are simultaneously packaged.

[0082] The present invention will be further illustrated by the following examples.

[0083] Example 1

[0084] This embodiment illustrates the stretchable circuit board and its preparation method disclosed in this invention, including the following steps:

[0085] Step S1: Fabrication of the elastic substrate and fiber-reinforced region

[0086] Take 90g of PDMS prepolymer and 9g of curing agent, stir evenly (500r / min, 5min), and pour into a polytetrafluoroethylene mold (120mm×60mm×200μm).

[0087] Lay the glass fiber mesh flat on the surface of the prepolymer, place it in a vacuum drying oven, evacuate to -0.092 MPa, and maintain for 20 minutes (stop after observing that there are no bubbles).

[0088] Transfer to a forced-air oven and cure at 110℃ for 1.5h. Allow to cool naturally to room temperature to obtain an elastic substrate with fiber-reinforced region (glass fiber layer buried depth 70μm).

[0089] Step S2: Laser ablation of the circuit groove

[0090] A CO2 laser processing machine was used, with a spot diameter of 30μm and a power density of 1.5W / cm². 2 Scanning speed 400mm / s;

[0091] Main line slot: single scan depth 60μm, 3 scans (total depth 180μm); branch line slot: single scan depth 40μm, 2 scans (total depth 80μm).

[0092] After ablation, the residue in the tank was purged with 0.3MPa compressed air (purging time 10s, distance 5mm), and no residue was observed under a microscope.

[0093] Plasma surface treatment: Argon-oxygen mixed gas (volume ratio 4:1), flow rate 15L / min, power 150W, treatment distance 8mm, time 45s;

[0094] Post-processing inspection: substrate surface contact angle 25° (contact angle measuring instrument);

[0095] Step S3: Circuit Forming

[0096] The following weight components were mixed and ultrasonically dispersed to obtain a liquid metal coating:

[0097] 45 parts of gallium indium zinc alloy (mass ratio 70:22:1), 15 parts of nano alumina, 15 parts of two-component epoxy resin, 1 part of 3-aminopropyltriethoxysilane, 0.1 parts of citric acid, and 15 parts of n-decane.

[0098] Screen printing: Liquid metal coating is used for screen printing on the circuit groove. A 200-mesh stainless steel wire mesh is selected, the squeegee hardness is 70A, the printing pressure is 0.2MPa, and the coating is applied twice along the direction of the circuit groove.

[0099] Curing: Place in an oven and cure at 90℃ for 1.5 hours. After cooling, a circuit pattern will be formed.

[0100] Insert the embedded end of the metal pin into the end of the branch line groove (in contact with the liquid metal coating), and adjust the extension end to extend 5mm beyond the edge of the elastic substrate;

[0101] Step S4: Packaging

[0102] Take 45g of PDMS prepolymer for packaging and 4.5g of curing agent, stir evenly and then coat it on the surface of the circuit pattern (coating thickness 500μm).

[0103] Place in an oven and cure at 80°C for 2 hours. Allow to cool naturally to obtain the finished stretchable circuit board.

[0104] Example 2

[0105] This embodiment illustrates the stretchable circuit board and its preparation method disclosed in this invention, including most of the operational steps in Embodiment 1, with the following differences:

[0106] The liquid metal is selected from a gallium-indium alloy (mass ratio 70:23).

[0107] Example 3

[0108] This embodiment illustrates the stretchable circuit board and its preparation method disclosed in this invention, including most of the operational steps in Embodiment 1, with the following differences:

[0109] The weight composition of liquid metal coatings is as follows:

[0110] 45 parts of gallium indium zinc alloy (mass ratio 70:22:1), 15 parts of nano alumina, 15 parts of two-component epoxy resin, 1 part of tetraethoxysilane, 0.1 parts of citric acid, and 15 parts of n-decane.

[0111] Example 4

[0112] This embodiment illustrates the stretchable circuit board and its preparation method disclosed in this invention, including most of the operational steps in Embodiment 1, with the following differences:

[0113] The weight composition of liquid metal coatings is as follows:

[0114] 45 parts of gallium indium zinc alloy (mass ratio 70:22:1), 15 parts of nano alumina, 15 parts of two-component epoxy resin, 1 part of 3-aminopropyltriethoxysilane, and 15 parts of n-decane.

[0115] Comparative Example 1

[0116] This comparative example is used to illustrate the stretchable circuit board and its preparation method disclosed in this invention, including most of the operational steps in Example 1, with the following differences:

[0117] In step S1, the fiberglass mesh is not laid.

[0118] In step S2, laser ablation of the circuit grooves is performed directly on the elastic substrate without fiber reinforcement.

[0119] Performance testing

[0120] The stretchable circuit board prepared above was subjected to the following performance tests:

[0121] Using a 100mm×20mm circuit board sample, the impedance of the main circuit was measured with a digital multimeter, and the initial impedance was recorded.

[0122] Using an electronic universal testing machine, the circuit board sample is fixed on the fixture, and the stretching direction is consistent with the line extension direction; the stretching amplitude is set to 30% (original length 100mm, stretched to 130mm), the stretching rate is 50mm / min, the recovery rate is 50mm / min, and the number of cycles is 1000.

[0123] After the stretching cycle, use a digital multimeter to measure the impedance of the main circuit.

[0124] The test results are entered into Table 1.

[0125] Table 1

[0126]

[0127] As shown in Table 1, the stretchable circuit boards of Examples 1-4 of this invention exhibit significantly better performance than Comparative Example 1 (without a glass fiber layer). Comparative Example 1, lacking a glass fiber layer to anchor the liquid metal, had an initial impedance of 68 mΩ and opened directly after 1000 cycles of 30% stretching. In contrast, Example 1, relying on the synergistic effect of the glass fiber layer and the circuit groove, had an initial impedance of only 13 mΩ, rising only to 15 mΩ after stretching, showing minimal impedance change and no open circuit. This highlights the crucial role of the glass fiber layer in inhibiting liquid metal aggregation and improving tensile fatigue resistance. Comparing Examples 1 with 2 (liquid metal without zinc), 3 (without 3-aminopropyltriethoxysilane), and 4 (without citric acid), it is evident that zinc inhibits metal oxidation, 3-aminopropyltriethoxysilane enhances the bond between the liquid metal and glass fiber, and citric acid reduces oxide formation; these three factors synergistically further optimize impedance and stability. In summary, this invention effectively solves the problems of high impedance and easy open circuits in traditional stretchable circuit boards through the glass fiber layer and optimized coating composition.

[0128] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A stretchable circuit board, characterized in that, The device includes an elastic substrate and an elastic encapsulation layer. The elastic encapsulation layer covers one side surface of the elastic substrate. A fiber reinforcement region is formed on the side of the elastic substrate facing the elastic encapsulation layer. A glass fiber layer is disposed in the fiber reinforcement region and passes through the elastic substrate. A circuit groove is formed in the fiber reinforcement region. The glass fiber layer is partially disposed in the circuit groove. The circuit groove is filled with a liquid metal coating, and a circuit pattern is formed by the liquid metal coating in the circuit groove. The liquid metal coating is prepared from a liquid metal paint, which comprises the following components by weight: The mixture contains 40-60 parts liquid metal, 10-30 parts filler, 6-22.4 parts adhesive resin, 0.5-2 parts 3-aminopropyltriethoxysilane, 0.1-0.2 parts citric acid, and 10-15 parts solvent.

2. The stretchable circuit board according to claim 1, characterized in that, The elastic substrate is one or more of hydrogenated styrene-butadiene block copolymer and polydimethylsiloxane; and / or The elastic encapsulation layer is one or more of hydrogenated styrene-butadiene block copolymer, polydimethylsiloxane, polyester elastomer, and polyurethane elastomer.

3. The stretchable circuit board according to claim 1, characterized in that, The fiber layer is selected from chopped glass fibers or glass fiber mesh.

4. The stretchable circuit board according to claim 1, characterized in that, The width of the line groove is 50~600μm, and the depth of the line groove is 50~200μm.

5. The stretchable circuit board according to claim 1, characterized in that, The liquid metal is selected from a gallium-indium-zinc alloy, wherein the mass ratio of gallium, indium, and zinc is (60~76):(16~25):(0.5~2); and / or, The filler is selected from one or more of alumina and silica; and / or, The bonding resin is selected from one or more of epoxy resin and polyurethane; and / or, The solvent is selected from one or more of n-decane, toluene, and cyclohexane.

6. The stretchable circuit board according to claim 1, characterized in that, It also includes a metal pin, one end of which is located between the elastic substrate and the elastic encapsulation layer, one end of which is electrically connected to the circuit groove, and the other end of which extends out of the elastic substrate and the elastic encapsulation layer.

7. The method for manufacturing a stretchable circuit board according to any one of claims 1 to 6, characterized in that, The following steps are included: S1. Provide an elastomer prepolymer, lay a glass fiber layer on one side surface of the elastomer prepolymer, apply a vacuum, and after the elastomer prepolymer has fully impregnated the glass fiber layer, cure the elastomer prepolymer to obtain an elastic substrate and a fiber-reinforced region formed on one side of the elastic substrate. S2. A laser is used to ablate the fiber-reinforced area according to the required circuit pattern to form a circuit groove, in which a glass fiber layer is retained. S3. Liquid metal coating is printed at the position corresponding to the circuit groove and cured to obtain the circuit pattern; S4. Encapsulate the surface of the circuit pattern to form a flexible encapsulation layer.

8. The method for preparing a stretchable circuit board according to claim 7, characterized in that, The ablation process uses a CO2 laser with a power density of 0.9~1.95 W / cm². 2 The scanning speed is 200~600mm / s.

9. The method for manufacturing a stretchable circuit board according to claim 7, characterized in that, After laser ablation, the side of the elastic substrate with the circuit groove is subjected to plasma surface treatment.

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