An integrated manufacturing method for multilayer interconnected stretchable flexible circuits

Abstract

This invention relates to an integrated manufacturing method for multilayer interconnected stretchable flexible circuits. It involves obtaining the lowest-positioned uninstalled components in each vertical column to form a candidate set, and using a relation matrix to organize the candidate set and intermediate sets with direct electrical connections to the candidate set into a working set. Horizontal and ramp bases are planned, and the base layer, conductive circuit, and component mounting are integrally printed. This process is repeated layer by layer upwards, eliminating the need for manual design of vias, leads, or layer alignment, achieving a fully automated transformation from three-dimensional layout to physical forming. Furthermore, the ramp base creates smooth conductive ramps between components of different heights, avoiding vertical vias or flying wires. This disperses stress during stretching deformation, reducing the risk of breakage and eliminating thermal damage and stress concentration points caused by laser drilling from the design source, significantly improving the mechanical reliability of the stretchable flexible circuit under repeated stretching and bending deformation.

Description

Technical Field

[0001] This invention relates to the field of flexible electronics technology, and more specifically, to an integrated manufacturing method for a multilayer interconnected stretchable flexible circuit. Background Technology

[0002] Stretchable electronics, due to its ability to maintain stable electrical properties even under mechanical deformation, has become a core technology for next-generation wearable devices, bio-integrated devices, and soft robots. Among them, multilayer flexible electronic devices integrate multiple functional units such as sensing, energy storage, processing, and communication in three-dimensional space, enabling higher space utilization, integration, and functional diversity.

[0003] Current methods for manufacturing multilayer flexible circuits primarily employ a laser ablation-backfill strategy: first, a laser is used to create holes in the flexible dielectric layer, then conductive materials such as liquid metal are filled in to achieve interlayer interconnection. However, this method suffers from problems such as thermal damage, stress concentration, and cumbersome processes. More importantly, existing technologies lack a systematic design methodology; the placement of components and the design of interconnect structures mainly rely on manual experience, making it difficult to achieve automated and precise manufacturing of complex three-dimensional circuits. Summary of the Invention

[0004] The technical problem to be solved by this invention is how to achieve automated manufacturing of multilayer flexible circuits while ensuring the manufacturing precision of multilayer flexible circuits.

[0005] This invention provides an integrated manufacturing method for multilayer interconnected stretchable flexible circuits, comprising the following steps: S1. Obtain the three-dimensional coordinates of all planned packaged components and divide them into vertical columns according to the planar coordinates of each component; construct a relationship matrix according to the electrical connection relationship between components; and construct an initially empty transit set, in which the state of the components includes not installed and installed, with the initial state of each component being not installed. S2, select the lowest-positioned uninstalled component in each vertical column to form a candidate set; S3, take the candidate set and the elements in the intermediate set that have a direct electrical connection with the candidate set to form the current working set; S4 is the horizontal base for the uninstalled components in the current work set. The existing horizontal base is reused for the installed components. According to the relationship matrix, the ramp base is planned for each pair of components with direct electrical connection. The base of the uninstalled area is the lowest height in the candidate set and the transfer set. S5, the integrated printing of the planned base stage, horizontal base stage and ramp base stage, forming the base layer, and printing conductive circuits along the horizontal base stage and ramp base stage, and installing the components in the candidate set onto the corresponding horizontal base stage, with the component status marked as installed; S6. Based on the relationship matrix, select components in the candidate set that still have a direct electrical connection with the uninstalled components and add them to the transfer set; remove components in the transfer set that do not have a direct electrical connection with the uninstalled components. S7, return to S2, until all components are installed. Then, fill all areas to the highest point in the longitudinal position according to the boundary dimensions of the stretchable flexible circuit. Finally, print the package to obtain the stretchable flexible circuit.

[0006] Compared with existing technologies, this application has the following advantages: by obtaining the lowest vertically positioned uninstalled components in each column to form a candidate set, and using a relation matrix to form a working set of components with direct electrical connections to the candidate set and intermediate set, and planning horizontal and ramp bases, a base layer is integrally printed, and conductive circuits and component mounting are printed. This process is repeated layer by layer upwards, and the entire process does not require manual design of vias, leads, or layer alignment, realizing a fully automated transformation from three-dimensional layout to physical forming. Moreover, the ramp base can form a smooth conductive ramp between components of different heights, avoiding vertical vias or flying wires, and dispersing stress during stretching deformation, making it less prone to breakage. This eliminates the thermal damage and stress concentration points caused by laser drilling from the design source, significantly improving the mechanical reliability of stretchable flexible circuits under repeated stretching and bending deformation.

[0007] In one possible implementation, the set of all planned packaged elements in step S1 is: , Indicates the total number of components; the first The three-dimensional coordinates of each component are ,in, This refers to the longitudinal position direction of the component, and also the thickness direction of the stretchable flexible circuit; Then define the equivalence relation for identical planar coordinates: ; The set of all vertical columns is: ; in, ; If plane coordinates If multiple elements correspond to a vertical column, then they are arranged according to their vertical coordinates. Perform ascending sorting and create an ascending Z-axis linked list of elements within each vertical column; if there is only one element, then the vertical column contains only one element.

[0008] In one possible implementation, constructing the relationship matrix based on the electrical connection relationships between components in step S1 includes: The three-dimensional coordinates of all components on a stretchable flexible circuit are represented as follows: The relation matrix is ​​then... for An dimensional matrix is ​​represented as: ; Among them, elements Defined as: , indicating the first The first component and the second The components are directly electrically connected; , indicating the first The first component and the second The components do not have a direct electrical connection.

[0009] In one possible implementation, step S2, which involves selecting the lowest-positioned uninstalled element in each vertical column to form a candidate set, includes: Define the state function of the component: ; For any vertical column Vertical column The collection of all uninstalled components is: ; like Then from the vertical column Select the component with the lowest vertical position: ; Candidate set , This represents the Lth basal layer formed from bottom to top.

[0010] In one possible implementation, the current working set in step S3 is: ; Seeking the middle, Indicates the first The intermediate set of the base layer.

[0011] In one possible implementation, the slope angle of the ramp base is... satisfy: ; In the formula, This represents the height difference between two horizontal bases that have a direct electrical connection. 'The straight-line distance between two horizontal bases that have a direct electrical connection.' The value range is 1°-89°.

[0012] In one possible implementation, the upper surface of the horizontal base is provided with a circuit channel for accommodating conductive circuits, the circuit channel having a width of 50μm-30μm and a depth of 50μm-100μm.

[0013] Compared with existing technologies, the depth and width range of the circuit channel can ensure the precise filling of liquid metal and avoid short circuits, while also matching the precision of the printing nozzle to achieve high-resolution conductive circuit printing.

[0014] In one possible implementation, in step S5, a horizontal and sloping base plate are integrally printed using a photocurable precursor liquid through digital light processing technology to form a base layer. The photocuring precursor is a mixture of isoborneol acrylate, benzyl acrylate, polyurethane acrylate and photoinitiator in a mass ratio of 20:50:30:1.

[0015] Compared with existing technologies, the resulting photocurable precursor liquid has both good stretchability and molding precision, meeting the mechanical performance requirements and printing precision of the substrate layer for stretchable flexible circuits.

[0016] In one possible implementation, in step S5, a conductive circuit is printed using direct ink writing printing technology with liquid metal along a path along the upper surface of a horizontal base, the sloping surface of a ramp base, and the upper surface of another horizontal base. The two horizontal bases are used to mount a pair of components with a direct electrical connection. The liquid metal is a eutectic gallium-indium alloy, which is heated at 50-70°C before printing to reduce surface tension.

[0017] Compared with existing technologies, eutectic gallium indium alloy has excellent conductivity and tensile properties, making it an ideal conductive material for flexible circuits. Heat treatment at 50-70℃ before printing can effectively reduce its surface tension, improve its wettability and filling ability on sloped surfaces, and ensure the continuity and uniformity of conductive circuits on slopes.

[0018] In one possible implementation, the element includes at least one of a resistor, capacitor, inductor, light-emitting diode, chip, sensor, or energy storage device.

[0019] Compared with existing technologies, the components cover passive components, active devices, sensing units and energy units, which reflects the versatility and wide applicability of the method of the present invention, and can integrate various functional components according to different application requirements. Attached Figure Description

[0020] Figure 1 This is a flowchart illustrating the method described in this application. Detailed Implementation

[0021] First, those skilled in the art should understand that these embodiments are merely used to explain the technical principles of the embodiments of this application and are not intended to limit the scope of protection of the embodiments of this application. Those skilled in the art can make adjustments as needed to adapt to specific application scenarios.

[0022] In the description of the embodiments of this application, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected" and "linked" 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. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this application based on the specific circumstances.

[0023] In the embodiments of this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0024] The present application will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0025] See Figure 1 As shown in the figure, this application discloses an integrated manufacturing method for a multilayer interconnected stretchable flexible circuit, specifically including: Step 1: Obtain the 3D coordinates of all planned packaged components and divide them into vertical columns based on the planar coordinates of each component; construct a relationship matrix based on the electrical connection relationships between components; and construct an initially empty transit set; the state of the components includes not installed and installed, and the initial state of each component is not installed. In this embodiment, all components in the planned package are derived from all components of the stretchable flexible circuit to be fabricated. The planar coordinates in the three-dimensional coordinates of each component represent the coordinates of its geometric center or package reference point. The set of all components in the planned package is... The three-dimensional coordinates of all components on a stretchable flexible circuit are represented as follows: ; Indicates the total number of components; the first The three-dimensional coordinates of each component are ,in, This refers to the longitudinal position of the component, and also the thickness direction of the stretchable flexible circuit.

[0026] Define the state function of the component: .

[0027] Define the equivalence relation for identical planar coordinates: ; The set of all vertical columns is: ; in, ; If plane coordinates If multiple elements correspond to a vertical column, then they are arranged according to their vertical coordinates. Perform ascending sorting and create an ascending Z-axis linked list of elements within each vertical column; if there is only one element, then the vertical column contains only one element.

[0028] The relation matrix for An dimensional matrix is ​​represented as: ; Among them, elements Defined as: , indicating the first The component and the first The components are directly electrically connected; , indicating the first The component and the first The components do not have a direct electrical connection.

[0029] The stretchable flexible circuit to be prepared in this embodiment is a double-layer stretchable flexible circuit, containing three components, and the coordinates of component A are... Coordinates of component B Coordinates of component C ,unit Component A is directly electrically connected to component B, and component B is directly electrically connected to component C, forming a coordinate set. relation matrix for An dimensional matrix is ​​represented as: .

[0030] Step 2: Select the lowest-positioned uninstalled component in each vertical column to form a candidate set; specifically including: For any vertical column Vertical column The collection of all uninstalled components is: ; like Then from the vertical column Select the component with the lowest vertical position: ; Candidate set , This represents the Lth basal layer stacked from bottom to top.

[0031] Step 3: Select the candidate set, and the intermediate set and the components that have a direct electrical connection with the candidate set to form the current working set, represented as: ; Seeking the middle, Indicates the first The intermediate set of the base layer.

[0032] Step 4: Plan horizontal bases for uninstalled components in the work set, reuse existing horizontal bases for installed components, and plan ramp bases for each pair of components with direct electrical connections according to the relationship matrix. The base of the component-free area is the lowest vertical position in the candidate set and transit set. In this embodiment, the shape and area of ​​the horizontal base are determined according to the pad layout or bottom contour of the corresponding component, and the projection of the horizontal base on the XOY plane extends outward from the center of the plane coordinates of its corresponding component. The slope angle of the sloping base satisfy: ; In the formula, This represents the height difference between two bases that have a direct electrical connection. The straight-line distance between two bases that have a direct electrical connection. The value range is 1°-89°.

[0033] This application embodiment has three vertical columns, and the candidate set with the lowest vertical position in each vertical column is... For each element in the candidate set, a base is planned, and according to the relationship matrix, a ramp base is used to connect element A and element B, and a ramp base is used to connect element B and element C.

[0034] Step 5: Print the planned base platform, horizontal base platform and ramp base platform in one piece to form the base layer, and print conductive circuits along the horizontal base platform and ramp base platform. Install the components in the candidate set onto the corresponding horizontal base platform, and mark the component status as installed.

[0035] This application embodiment utilizes digital light processing technology to integrally print components A, B, and C using a photocurable precursor liquid, forming a horizontal base platform and a ramp base platform connecting components A and B, and another ramp base platform connecting components B and C, thus creating a base layer. To ensure the base layer possesses good tensile strength and molding accuracy, meeting the mechanical performance requirements and printing precision of the stretchable flexible circuit, this application employs a photocurable precursor liquid composed of isoborneol acrylate, benzyl acrylate, polyurethane acrylate, and a photoinitiator in a mass ratio of 20:50:30:1 for 3D printing, integrally molding the base layer. The printing parameters are set as follows: single-layer curing thickness 50 μm, single-layer exposure time 1.5 s.

[0036] Furthermore, in order to ensure the precise filling of liquid metal and avoid short circuits, the upper surface of the horizontal base is provided with circuit channels for accommodating conductive circuits. The width of the circuit channels is 50μm-300μm and the depth is 50μm-100μm. This ensures that the precision of the circuit channels matches that of the printing nozzles, thereby enabling the printing of high-resolution conductive circuits.

[0037] This application embodiment uses direct ink writing printing technology and liquid metal to print conductive circuits along the path of the upper surface of a horizontal base, the sloping surface of a ramp base, and the upper surface of another horizontal base, and installs corresponding components at each mounting position; the two horizontal bases are used to install a pair of components with a direct electrical connection relationship.

[0038] To ensure the continuity and uniformity of the conductive circuit, the liquid metal in this embodiment is a eutectic gallium-indium alloy. Eutectic gallium-indium alloy has excellent conductivity and tensile properties, making it an ideal conductive material for flexible circuits. Heat treatment at 50-70°C before printing can effectively reduce its surface tension and improve its wettability and filling ability on sloping surfaces.

[0039] Step 6: Based on the relationship matrix, select components in the candidate set that still have a direct electrical connection with the uninstalled components and add them to the transfer set; remove components in the transfer set that do not have a direct electrical connection with the uninstalled components.

[0040] Step 7: Return to S2 until all components are installed. Then, fill the component-free area to the highest point in the vertical direction according to the boundary dimensions of the stretchable flexible circuit. Finally, print the package to obtain the stretchable flexible circuit.

[0041] It should be noted that the stretchable flexible circuit of this application method is designed before manufacturing. To ensure that components with direct electrical connections are connected to the ramp base, components with direct electrical connections in the stretchable flexible circuit will not be located in the same vertical column. Furthermore, this embodiment only uses three components as an example, but the method of this invention is not limited to this. Additionally, the technique of stacking and printing ramp bases, horizontal bases, and base plates layer by layer is a conventional technique in 3D printing and will not be elaborated upon here. Depending on the actual application requirements, a greater number of components can be integrated, and the component types can include any combination of resistors, capacitors, inductors, light-emitting diodes, chips, sensors, energy storage devices, etc., all of which can be automatically planned and manufactured layer by layer through the iterative algorithm of this invention.

[0042] Comparative experiment: To compare performance, a double-layer circuit with interconnected vias was fabricated using a laser ablation-fill method. A double-layer substrate (without a ramp) was printed using the same photocurable resin. Then, through-holes with a diameter of approximately 200 μm were ablated at the locations requiring interconnection using a 355 nm ultraviolet laser. Subsequently, heated EGaIn was injected into the holes using a laser-cured laser (DIW). This process encountered problems such as incomplete filling, poor hole wall wettability, and the need for repeated operations. The final sample was used as a control sample.

[0043] Systematic tests were conducted on the double-layer stretchable flexible circuit printed in this application and a comparative sample. In the tensile cycle test at 100% strain, the resistance change rate of the double-layer stretchable flexible circuit was still less than 2% after 11,000 cycles at 100% strain, while the comparative sample broke circuit after approximately 5,000 cycles. In the bending cycle test, the resistance change rate of the double-layer stretchable flexible circuit was still less than 0.1% after 13,000 cycles, while the comparative sample broke circuit after approximately 7,800 cycles. The experimental results fully demonstrate the superiority of the method of this invention.

[0044] The method described in this application is applicable to the large-scale automated manufacturing of various stretchable and flexible circuits, particularly suitable for wearable electronic devices, biomedical sensors, and soft robot sensing systems. By directly driving 3D printing equipment with design data, rapid conversion from circuit schematics to physical products can be achieved, demonstrating significant industrial application value.

[0045] In the description of the embodiments of this application, it should be noted that the terms "inner" and "outer" and other terms indicating direction or positional relationship are based on the direction or positional relationship shown in the drawings. This is only for the convenience of description and does not indicate or imply that the device or component must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of this application.

[0046] In the description of this application, the references to terms such as "an embodiment," "some embodiments," "in this embodiment," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in a suitable manner in any one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0047] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. An integrated manufacturing method for a multilayer interconnected stretchable flexible circuit, characterized in that, Includes the following steps: S1, obtain the three-dimensional coordinates of all planned packaged components, and divide them into vertical columns according to the planar coordinates of each component; construct a relationship matrix based on the electrical connection relationships between the components; And construct an initially empty transit set, with the state of the components including not installed and installed, and the initial state of each component is not installed; S2, select the lowest-positioned uninstalled component in each vertical column to form a candidate set; S3, take the components in the candidate set and the components in the transit set that have a direct electrical connection with the candidate set to form the current working set; S4 is the horizontal base for the uninstalled components in the current work set. The existing horizontal base is reused for the installed components. According to the relationship matrix, the ramp base is planned for each pair of components with direct electrical connection. The base of the uninstalled area is the lowest height in the candidate set and the transfer set. S5, the integrated printing of the planned base stage, horizontal base stage and ramp base stage, forming the base layer, and printing conductive circuits along the horizontal base stage and ramp base stage, and installing the components in the candidate set onto the corresponding horizontal base stage, with the component status marked as installed; S6. Based on the relationship matrix, select components in the candidate set that still have a direct electrical connection with the uninstalled components and add them to the transfer set; remove components in the transfer set that do not have a direct electrical connection with the uninstalled components. S7, return to S2, until all components are installed. Then, fill all areas to the highest point in the longitudinal position according to the boundary dimensions of the stretchable flexible circuit, and finally print the package.

2. The integrated manufacturing method of the multilayer interconnected stretchable flexible circuit according to claim 1, characterized in that, The set of all planned packaged components in step S1 is , Indicates the total number of components; the first The three-dimensional coordinates of each component are ,in, This refers to the longitudinal position direction of the component, and also the thickness direction of the stretchable flexible circuit; Then define the equivalence relation for identical planar coordinates: ； The set of all vertical columns is: ； in, ; If plane coordinates If multiple elements correspond to a vertical column, then they are arranged according to their vertical coordinates. Perform ascending sorting and create an ascending Z-axis linked list of elements within each vertical column; if there is only one element, then the vertical column contains only one element.

3. The integrated manufacturing method of the multilayer interconnected stretchable flexible circuit according to claim 2, characterized in that, Step S1 involves constructing a relationship matrix based on the electrical connections between components, including: The three-dimensional coordinates of all components on a stretchable flexible circuit are represented as follows: The relation matrix is ​​then... for An dimensional matrix is ​​represented as: ； Among them, elements Defined as: , indicating the first The component and the first The components are directly electrically connected; , indicating the first The component and the first The components do not have a direct electrical connection.

4. The integrated manufacturing method of the multilayer interconnected stretchable flexible circuit according to claim 3, characterized in that, In step S2, the candidate set is formed by selecting the lowest-positioned uninstalled element in each vertical column, including: Define the state function of the component: ； For any vertical column Vertical column The collection of all uninstalled components is: ； like Then from the vertical column Select the component with the lowest vertical position: ； Candidate set , This represents the Lth basal layer from bottom to top.

5. The integrated manufacturing method of the multilayer interconnected stretchable flexible circuit according to claim 4, characterized in that, The current working set in step S3 is: ； Seeking the middle, Indicates the first The intermediate set of the base layer.

6. The integrated manufacturing method of the multilayer interconnected stretchable flexible circuit according to claim 1, characterized in that, The slope angle of the sloping base satisfy: ； In the formula, This represents the height difference between two horizontal bases that have a direct electrical connection. The straight-line distance between two horizontal bases that have a direct electrical connection. The value range is 1°-89°.

7. The integrated manufacturing method of the multilayer interconnected stretchable flexible circuit according to claim 1, characterized in that, The upper surface of the horizontal base is provided with a circuit channel for accommodating conductive circuits, the width of the circuit channel being 50μm-30μm and the depth being 50μm-100μm.

8. The integrated manufacturing method of the multilayer interconnected stretchable flexible circuit according to claim 1, characterized in that, In step S5, digital light processing technology is used to print horizontal and sloping base plates in an integrated manner using photocurable precursor liquid to form the base layer. The photocuring precursor is a mixture of isoborneol acrylate, benzyl acrylate, polyurethane acrylate and photoinitiator in a mass ratio of 20:50:30:

1.

9. The integrated manufacturing method of the multilayer interconnected stretchable flexible circuit according to claim 1, characterized in that, In step S5, direct ink writing printing technology is used to print conductive circuits along the path of the upper surface of a horizontal base, the slope surface of a ramp base, and the upper surface of another horizontal base using liquid metal. The two horizontal bases are used to mount a pair of components with a direct electrical connection. The liquid metal is a eutectic gallium-indium alloy, which is heated at 50-70°C before printing to reduce surface tension.

10. The integrated manufacturing method of the multilayer interconnected stretchable flexible circuit according to claim 1, characterized in that, The component includes at least one of a resistor, capacitor, inductor, light-emitting diode, chip, sensor, or energy storage device.

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