Non-deployable curved surface micro conformal circuit additive manufacturing method based on electric field driving

Abstract

The invention relates to the technical field of micro-nano additive manufacturing and electronic manufacturing, in particular to a non-deployable curved surface micro conformal circuit additive manufacturing method based on electric field driving. A circuit pattern mask is needed at any non-deployable three-dimensional curved surface conformal manufacturing position, and an imprinting working soft mold consistent with the female mold plate in structure is prepared through secondary mold turning; secondly, conformal imprinting and shape restoring are carried out, and a groove structure consistent with the geometric pattern of the circuit is obtained on the curved-surface base material in the modes of etching, roughening treatment and the like; then, the groove is filled with a seed layer, and the groove is filled with high-conductivity metal through the electroplating technology; afterwards, dissimilar metal in the groove is molten and strengthened through laser, after the metal is cooled, the metal and the coarsened microstructure in the groove form an interlocking structure, and the binding force between the metal layer and the base material is greatly enhanced; and finally, performing post-treatment on the surface of the sample piece through processes such as polishing and the like to obtain the final curved surface conformal circuit with the embedded conductive circuit.

Description

Technical Field

[0001] The present application belongs to the field of micro-nano additive manufacturing and electronic manufacturing technology, and specifically relates to an electric field-driven non-developable curved surface micro-conformal circuit additive manufacturing method. Background Art

[0002] As a cutting-edge technology, three-dimensional curved electronic circuits achieve miniaturization, lightweight and functional diversification of electronic devices by directly integrating electronic components and circuits on three-dimensional curved structures. This technology breaks through the limitations of traditional planar circuits and provides more possibilities for the innovative design of electronic products. It is widely used in many fields such as biomedicine, wearable devices, smart skins, curved conformal antennas, frequency selective surfaces (FSS), structural health monitoring, bioelectronics, military communications, radar, navigation, etc., and has become a research hotspot in the field of electronic manufacturing. However, with the continuous expansion of application scenarios, the service environment has become more and more harsh and challenging, and higher and higher requirements are placed on curved conformal circuits. For example, hypersonic missiles and aircraft need to withstand extremely harsh service environments such as high vibration, high impact, and high temperature. Therefore, higher requirements are placed on the circuit's high conductivity, high precision, strong adhesion, and high reliability. However, various existing manufacturing technologies still face many challenges in manufacturing high-performance curved conformal circuits.

[0003] At present, the commonly used technologies for manufacturing curved conformal circuits mainly include laser direct writing technology, holographic lithography technology, splicing method, transfer method, integrated molded electronics, aerosol jet printing, inkjet printing and electrohydrodynamic jet printing. Although each technology has demonstrated its unique functions, there are still certain limitations for non-developable arbitrary complex curved substrates. For example, laser direct writing technology requires high-precision laser equipment and complex control systems, which is costly. At the same time, for some special materials or curved shapes, its processing effect may be limited. Holographic lithography technology also faces the limitations of high cost, high processing environment requirements and processing efficiency. Although splicing and transfer methods have shown application potential in the manufacture of spherical antennas, spherical LED arrays and spherical solar cell arrays, they may have great difficulties in dealing with complex arbitrary surfaces, especially for non-developable free-form surfaces. Further research is needed. Integrated molded electronics technology has high requirements on the performance of the electronic materials used, and often requires the materials to have good plasticity, conductivity, temperature resistance and corrosion resistance. Although the jet printing technology can directly realize large-area, high-precision manufacturing of micro-nano structures on various substrates such as flat / curved surfaces, organic / inorganic, etc., the printing accuracy and quality may be affected for non-developable curved surfaces or high curvature areas; when manufacturing complex non-developable three-dimensional curved circuits, the printing speed and efficiency will also be subject to certain limitations. In addition, most of the curved conformal circuits manufactured by these existing manufacturing technologies are embossed circuits attached to the surface of the curved substrate, which have many reliability problems, such as poor adhesion between the circuit and the substrate, and difficulty in adapting to the current harsh and harsh service environment. The embossed circuit will cause the device surface to be high in roughness and is susceptible to physical damage such as mechanical stress, scratches, and impacts, which may cause the circuit to break; when the circuit is exposed to the air for a long time, oxidation or corrosion may occur, thereby affecting the conductivity and stability of the circuit.

[0004] In summary, the manufacturing of three-dimensional non-developable curved electronic circuits mainly faces the following challenges: First, it is difficult for existing manufacturing technologies to achieve the manufacturing of high-resolution, high-performance conformal circuits on non-developable, multi-curvature, and arbitrarily complex curved substrates; second, the preparation process is complex, and the equipment cost, manufacturing accuracy, and efficiency are limited; third, the embossed (surface) curved circuits have poor adhesion, and the circuit reliability is poor in the face of harsh conditions such as high vibration and large impact. Therefore, how to achieve efficient, low-cost, and high-consistency manufacturing of embedded high-resolution, high-performance (high conductivity, high adhesion) curved conformal circuits on non-developable, multi-curvature, and arbitrarily complex curved substrates is still a problem that needs to be solved urgently.

[0005] The information in this background technology section is only intended to enhance the understanding of the overall background of the application and should not be construed as an admission or any form of suggestion that the information constitutes the prior art already known to a person of ordinary skill in the art. Summary of the invention

[0006] In order to solve the above problems, especially the difficulty of existing manufacturing technology to realize the efficient, low-cost and high-consistency manufacturing of embedded high-resolution, high-performance curved conformal circuits on non-developable, multi-curvature and arbitrarily complex curved substrates, this application proposes an electric field-driven non-developable curved micro-conformal circuit additive manufacturing method.

[0007] In some embodiments of the present application, a method for additive manufacturing of a non-developable curved surface micro-conformal circuit based on electric field driving is provided, comprising the following steps:

[0008] Step 1: Master mold manufacturing, using molten printing material as the printing material to print a large-sized, non-jointed, non-developable surface micro-nano master mold;

[0009] Step 2: Replicate the embossing soft mold and manufacture a working soft mold for embossing through a secondary mold replication process;

[0010] Step 3: Spread embossing glue on the surface of the curved substrate, cover the embossing working soft mold on the embossing glue, emboss the circuit pattern, and replicate the circuit pattern on the embossing glue;

[0011] Step 4: Replicate a groove consistent with the conformal circuit on the curved substrate using etching technology, and perform roughening and optional modification on the surface of the groove;

[0012] Step 5: Using nano-conductive ink, deposit a nano-conductive seed layer in the groove;

[0013] Step 6: Precision electroplating and depositing conductive metal, continuing to electroplating and depositing conductive metal on the nano-conductive seed layer in the groove of the curved substrate, so that the metal material is completely filled in the groove of the curved substrate;

[0014] Step 7: Laser melting heterogeneous interface strengthening, heating and melting the conductive metal and seed layer in the electroplating groove, so that the molten material is completely filled into the micro-nano structure of the roughened substrate groove, and the heterogeneous interface forms an interlocking structure to achieve strong adhesion between the conductive pattern and the substrate;

[0015] Step 8: Post-process the surface of the curved substrate to remove excess metal on the surface of the curved substrate and complete the manufacture of the three-dimensional curved conformal circuit.

[0016] In some embodiments of the present application, the master mold manufacturing in step 1 includes the following steps:

[0017] (1) Using a processing machine tool to manufacture a physical model of the processing object;

[0018] (2) Using thermoplastic polymer molten material as the printing material, a conformal circuit pattern is printed on the surface of the physical model to complete the manufacturing of the imprinted master mold.

[0019] In some embodiments of the present application, the step 2 of replicating the embossed soft mold comprises the following steps:

[0020] (1) Replicating the intermediate soft mold (groove circuit pattern): pouring the first liquid material onto the master mold, and demolding after solidification to produce an intermediate soft mold;

[0021] (2) Replicating the embossed soft mold (embossed circuit pattern): pouring the second liquid material onto the intermediate soft mold and completely curing it;

[0022] (3) Separating the replica embossing soft mold from the intermediate soft mold;

[0023] (4) Flipping the replica embossing soft mold: Flip the replica embossing soft mold as a whole, spray a release agent on the surface, and manufacture a working soft mold for embossing.

[0024] In some embodiments of the present application, the step 3 of coating the curved substrate surface with embossing glue to emboss the circuit pattern comprises the following steps:

[0025] (1) coating a layer of embossing adhesive on the surface of the substrate;

[0026] (2) aligning the imprint working soft mold manufactured in step 2 with the curved substrate, and applying pressure to achieve conformal contact between the soft mold and the curved substrate;

[0027] (3) Replicate the soft mold structure on the imprint glue and reduce the thickness of the residual layer by applying air pressure and electric field force;

[0028] (4) releasing the embossing force, maintaining the shape for a period of time, and then curing the embossing glue;

[0029] (5) After the embossing adhesive is completely cured, the soft mold is separated from the embossed pattern by peel-off demolding, thereby achieving efficient and high-precision preforming of three-dimensional graphics.

[0030] In some embodiments of the present application, the step 4 utilizes etching technology to replicate a groove consistent with the conformal circuit on the substrate, and performs roughening and modification on the surface of the groove, including the following steps:

[0031] (1) Removing the embossing residual layer;

[0032] (2) using the photoresist of the replicated pattern as a mask, and using wet etching to etch a circuit pattern groove in the curved substrate;

[0033] (3) removing photoresist;

[0034] (4) Roughening the grooves of the curved substrate to form irregular micro-nano structures in the grooves of the curved substrate; and determining whether to further modify the grooves to achieve super-hydrophilicity according to needs.

[0035] In some embodiments of the present application, manufacturing the seed layer in step 5 includes the following steps:

[0036] (1) Using nano conductive ink material as printing material, filling the nano conductive material ink into the groove;

[0037] (2) The nano-conductive ink filled in the groove is sintered and made conductive to complete the manufacture of the nano-seed layer.

[0038] In some embodiments of the present application, the precision electroplating deposition of conductive metal in step 6 comprises the following steps:

[0039] The electroplating process is used to continuously deposit the conductive metal on the seed layer of the groove of the curved substrate, so that the groove of the curved substrate is completely filled with the metal material.

[0040] In some embodiments of the present application, the laser melting heterogeneous interface strengthening in step 7 includes the following steps:

[0041] (1) Installing the electroplated workpiece onto a five-axis electric field-assisted fluid / laser multi-module three-dimensional surface graphics printing device; using a positioning camera and combining alignment marks to align the workpiece on the printing device;

[0042] (2) Using a laser, the electroplated conductive metal and the seed layer are heated and melted according to the planned circuit pattern printing path. The molten metal is completely filled into the micro-nano structure of the roughened substrate groove. After the metal cools, an interlocking structure is formed at the heterogeneous interface between the metal and the roughened groove. The interlocking structure is used to achieve strong adhesion between the metal pattern and the substrate.

[0043] In some embodiments of the present application, the surface post-treatment of the curved substrate in step 8 comprises the following steps:

[0044] The excess metal material outside the groove of the curved substrate and the part of the metal filling the groove of the curved substrate that is higher than the surface of the substrate are removed to complete the manufacture of the curved conformal circuit on the curved substrate.

[0045] In some embodiments of the present application, the melting printing material in step 1 includes but is not limited to polymethyl methacrylate (PMMA), polycaprolactone (PCL), polylactic acid (PLA), etc.

[0046] In some embodiments of the present application, the master mold manufacturing method in step 1 includes but is not limited to five-axis linkage electric field driven melt jet micro-nano 3D printing, electron beam lithography, femtosecond laser direct writing, aerosol jet printing, etc.

[0047] In some embodiments of the present application, the printing substrate in step 1 includes but is not limited to ceramics, glass, sapphire, resin, etc.;

[0048] In some embodiments of the present application, the mold replication material in step 2 is, but is not limited to, polydimethylsiloxane (PDMS), fluoropolymer, etc.;

[0049] In some embodiments of the present application, the method of coating the embossing glue on the surface of the curved substrate in step 3 includes but is not limited to a pulling film-forming method, a spraying method, and the like.

[0050] In some embodiments of the present application, the embossing glue curing method in step 3 includes but is not limited to UV curing, heating curing, etc.

[0051] In some embodiments of the present application, the etching method in step 4 includes but is not limited to wet etching and dry etching.

[0052] In some embodiments of the present application, the method for roughening the grooves of the curved substrate in step 4 includes but is not limited to chemical roughening, laser roughening, etc. In addition, further modification treatment can be performed as needed to achieve high hydrophilicity.

[0053] In some embodiments of the present application, the nano-conductive ink curing method in step 5 includes but is not limited to heating curing, laser sintering curing, etc.

[0054] In some embodiments of the present application, the conductive metal material electroplated in step 6 includes but is not limited to gold, silver, copper, nickel, etc.

[0055] In some embodiments of the present application, the surface post-treatment in step 8 includes but is not limited to polishing, laser cleaning, plasma cleaning, etc.

[0056] In some embodiments of the present application, the groove is a micro-nano scale groove, preferably a nano-scale groove.

[0057] Compared with the prior art, this application has the following beneficial effects:

[0058] (1) The method proposed in the present application can realize the manufacture of nanoscale and sub-microscale high-resolution, high-performance surface conformal embedded circuits on any complex three-dimensional surface, especially on non-developable, multi-curvature surface substrates, by manufacturing a master template, through mold transfer, precise embossing process and metal filling process.

[0059] (2) The present application performs etching, roughening, filling, melt strengthening and other treatments on the substrate, so that the conductive metal is embedded in the groove of the substrate to form an embedded interlocking structure, thereby achieving strong adhesion between the metal pattern and the substrate, having excellent mechanical properties, and achieving an interface bonding strength better than 50MPa.

[0060] (3) The method proposed in this application can realize low-cost, mass production, which can greatly improve production efficiency. By optimizing the process flow and automated equipment, the production cycle can be further shortened, production costs can be reduced, and production efficiency can be improved.

[0061] (4) The method proposed in this application is applicable to a variety of materials, including polymers, metals, and composite materials, and has good material compatibility.

[0062] (6) The present application continues to electroplating and deposits a highly conductive metal on the seed layer filled in the groove, and uses a high-power laser to melt and combine dissimilar metal materials to form a highly conductive alloy with excellent conductivity; through post-processing processes such as polishing, an embedded conductive pattern with extremely small surface roughness can be further obtained without affecting the surface morphology of the device.

[0063] (7) Broad application prospects. With the popularization of curved electronic products and the continuous development of microelectronics manufacturing processes, curved conformal circuit technology has shown great application prospects in the fields of national defense, military, aerospace, information communication, structural electronics, and three-dimensional sensing. For example, in the fields of frequency selective surfaces (FSS), conformal antennas, smart skins, and curved circuit boards, this technology can play an important role. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] The drawings in the specification, which constitute a part of the present application, are used to provide further understanding of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute improper limitations on the present application.

[0065] Figure 1 A schematic diagram of the structure of a five-axis linkage electric field assisted fluid / laser multi-module three-dimensional surface graphics printing equipment in some embodiments of the present application;

[0066] Figure 2 A schematic flow chart of a method for additive manufacturing of non-developable curved surface micro-conformal circuits based on electric field driving in some embodiments of the present application; DETAILED DESCRIPTION

[0067] In order to enable those skilled in the art to better understand the technical solution of the present disclosure, the present disclosure is described in detail below in conjunction with the accompanying drawings and specific implementation methods, but this is not intended to limit the present disclosure.

[0068] All terms (including technical terms or scientific terms) used in the present disclosure have the same meanings as those understood by ordinary technicians in the field to which the present disclosure belongs, unless otherwise specifically defined. It should also be understood that terms defined in general dictionaries, such as general dictionaries, should be interpreted as having meanings consistent with their meanings in the context of the relevant technology, and should not be interpreted in an idealized or extremely formal sense, unless explicitly defined herein.

[0069] Technologies, methods, and equipment known to ordinary technicians in the relevant art may not be discussed in detail, but where appropriate, the technologies, methods, and equipment should be considered part of the specification.

[0070] The following is combined with Figure 1 and 2 To illustrate the detailed technical solution of this application.

[0071] Figure 1 This is a structural schematic diagram of a five-axis linkage electric field assisted fluid / laser multi-module three-dimensional surface graphics printing equipment in some embodiments of the present application, which includes an XYZ workbench that can drive the print head to move up and down, left and right, and forward and backward. A curved substrate is placed on the printing platform. An independent motor arranged on the printing platform can drive the curved substrate to move horizontally or flip. Laser 1 and laser 2 are placed near the print head and can be used to solidify the printed material. A positioning camera can locate the printing position and an observation camera can observe the printing situation.

[0072] Example 1

[0073] This example uses a ceramic matrix material as a three-dimensional curved surface substrate to specifically illustrate the detailed process of the electric field-assisted three-dimensional curved surface embedded conformal circuit manufacturing method proposed in this application.

[0074] Step 1: Master mold manufacturing (large-size, non-spliced, non-developable surface micro-nano mold).

[0075] The processing object (ceramic substrate) is digitally inverted, and a self-developed five-axis linkage electric field driven melt jet deposition micro-nano 3D printer is used to print a polycaprolactone (PCL) pattern on a ceramic substrate as an imprint mold master. The PCL master mold in this embodiment is a wire grid structure with a line width of 400nm and a spacing of 200μm.

[0076] Step 2: Copy the embossing soft mold.

[0077] Using the PCL master template printed in step 1, a working soft mold for embossing is manufactured through a secondary mold replication process. The prepared working soft mold has the same characteristic structure as the PCL master template, with a convex structure line width of 400nm and a spacing of 200μm. The specific process is as follows:

[0078] (1) Copy the intermediate soft mold (groove circuit pattern), pour material A, i.e., the first liquid material: a liquid PDMS material mixed with silver particles, onto the master mold, heat and solidify it, and then use a peel-off demolding method to demold it, so as to manufacture an intermediate soft mold, such as Figure 2 (b)

[0079] (2) Replicating the embossed soft mold (embossed circuit pattern). Pour material B, i.e., the second liquid material, fluoropolymer, into the concave surface of the intermediate soft mold, centrifugally rotate the fluoropolymer to uniformly conform to the inner surface of the intermediate soft mold, and then heat it to fully cure it;

[0080] (3) The cured replica embossing soft mold is separated from the intermediate soft mold by a peeling demoulding method (demolding) to produce an embossing soft mold, such as Figure 2 (c)

[0081] (4) Flipping the replica embossing soft mold. Flip the inner and outer surfaces of the replica embossing soft mold, spray a release agent on the inner surface with microstructures to produce a working soft mold for embossing, and conformally attach a layer of conductive PET as a backing to the outer surface of the working soft mold for embossing. Figure 2 As shown in (d, e).

[0082] Step 3: Apply embossing glue on the surface of the curved substrate and emboss the circuit pattern.

[0083] The electric field assisted imprinting (force-electric synergistic imprinting) technology is used to conformally imprint on a ceramic substrate coated with an imprinting glue to replicate the groove structure of the circuit pattern, such as Figure 2 (e) is shown. The specific process is as follows:

[0084] (1) spraying a layer of embossing adhesive mixed with silver conductive particles on the surface of the ceramic substrate by a spraying method, and installing an electrode ring at the bottom of the substrate so that the electrode ring is in contact with the embossing adhesive;

[0085] (2) aligning the imprint working soft mold manufactured in step 2 with the substrate, and then conformally attaching it to the surface of the substrate and applying auxiliary gas pressure to achieve complete conformal contact between the soft mold and the three-dimensional ceramic substrate;

[0086] (3) Using electric field assisted imprinting technology, the electrode ring at the bottom of the ceramic substrate is connected to the negative electrode of the high-voltage power supply, and the conductive PET on the upper surface of the working soft mold is connected to the positive electrode of the high-voltage power supply. Through the applied electric field force, the imprinting glue fully fills the grooves on the mold surface. Under the dual effects of air pressure and electric field force, the thickness of the residual layer is further reduced, and the soft mold structure is replicated on the imprinting glue;

[0087] (4) releasing the imprinting force (electric field force and gas-assisted pressure) and maintaining the shape for a period of time, and then irradiating with ultraviolet light for a certain period of time to completely cure the imprinting glue;

[0088] (5) After the embossing adhesive is completely cured, the soft mold is separated from the embossed pattern by peel-off demolding (demolding sequentially from the periphery to the center), thereby achieving efficient and high-precision preforming of three-dimensional graphics.

[0089] Step 4: Use etching technology to replicate a groove consistent with the conformal circuit on the substrate, and roughen and modify the surface of the groove. The specific process is as follows:

[0090] (1) Use laser to remove the residual layer of embossing;

[0091] (2) using the photoresist of the replicated pattern as a mask, wet-etching the ceramic substrate with an acidic etching solution consisting of 92-98 wt.% of concentrated sulfuric acid and 0.1-8 wt.% of cryolite, and 0.1-8 wt.% of boric acid, to etch a circuit pattern groove in the curved substrate;

[0092] (3) using a degumming agent to remove all photoresist masks;

[0093] (4) A high-power laser is used to roughen the grooves of the curved substrate to form irregular micro-nano structures in the grooves of the curved substrate.

[0094] Step 5: Filling seed layer based on charge injection electrowetting and electric field driven jet micro-nano 3D printing.

[0095] (1) Using the printing module of the five-axis electric field-assisted fluid / laser multi-module three-dimensional surface graphics printing equipment, nanosilver ink is filled in the grooves of the ceramic surface as the seed layer for the subsequent electroplating process. The conductive material is squeezed out of the print head under the action of electric field force, gravity, etc. and deposited in the grooves of the ceramic surface. Then, using the charge injection electrowetting effect, the charges on the inner surface of the substrate groove and the surface of the ink will show a tendency of opposite charges to attract each other, driving the ink to move downward, thereby filling the submicroscale grooves, such as Figure 2 (g) as shown.

[0096] Step 6: Precision electroplating deposits copper.

[0097] Using the electroplating process, copper is continuously electroplated and deposited on the seed layer of the curved substrate groove to completely fill the groove of the curved substrate with copper. Figure 2 (h). The specific process is as follows:

[0098] The sample prepared in step 5 was connected to the negative pole of the DC power supply by connecting the connecting wire from the seed layer, and the positive pole was connected to the copper plate. The sample was placed in a plating solution composed of 300 g / L copper sulfate and 20 g / L copper chloride for electroplating. The current density was set to 1 A / dm 2 , the electroforming time is about 5min.

[0099] Step 7: Laser melting heterogeneous interface strengthening.

[0100] Through high-intensity laser tracking processing of the conductor, the seed layer metal and the electroplated deposited metal are melted and combined, the heterogeneous interface is eliminated, and a highly conductive alloy is formed. At the same time, the molten metal fills the roughened grooves to further enhance the bonding force between the metal layer and the ceramic substrate. The specific process is as follows:

[0101] (1) Reinstall the electroplated workpiece onto the five-axis electric field-assisted fluid / laser multi-module three-dimensional surface graphics printing equipment. Use a positioning camera and alignment marks to align the workpiece on the printing equipment;

[0102] (2) Using laser 2 (high power mode), and following the planned circuit pattern printing path, the electroplated copper and seed layer are heated and melted, so that the molten metal is completely filled into the micro-nano structure of the roughened substrate groove. After the metal cools, an interlocking structure is formed between the metal and the roughened groove heterogeneous interface. The interlocking structure is used to achieve strong adhesion between the metal pattern and the substrate, such as Figure 2 (i) as shown.

[0103] Step 8: Post-processing of the curved substrate surface: Use a polishing machine to polish away the excess metal material outside the curved substrate groove and the part of the curved substrate groove filled with metal that is higher than the substrate surface. Figure 2 (j) shows. The manufacturing of curved conformal circuits is completed on curved substrates, such as Figure 2 (k) as shown.

[0104] Example 2

[0105] This example uses polymer PEEK material as a three-dimensional curved surface substrate to specifically illustrate the detailed process of the electric field-assisted three-dimensional curved surface embedded conformal circuit manufacturing method proposed in this application.

[0106] Step 1: Master mold manufacturing (large-size, non-spliced, non-developable surface micro-nano mold).

[0107] The processing object (ceramic substrate) is digitally inverted, and a self-developed five-axis linkage electric field driven melt jet deposition micro-nano 3D printer is used to print a polycaprolactone (PCL) pattern on a ceramic substrate as an imprint mold master. The PCL master mold in this embodiment is a wire grid structure with a line width of 500nm and a spacing of 300μm.

[0108] Step 2: Copy the embossing soft mold.

[0109] Using the PCL master template printed in step 1, a working soft mold for embossing is manufactured through a secondary mold replication process. The prepared working soft mold has the same characteristic structure as the PCL master template, with a convex structure line width of 500nm and a spacing of 300μm. The specific process is as follows:

[0110] (1) Replicate the intermediate soft mold (groove circuit pattern), pour the liquid PDMS material mixed with silver particles onto the master mold, heat and solidify it, and then use the peel-off demolding method to demold it to produce an intermediate soft mold, such as Figure 2 (b)

[0111] (2) Replicating the embossed soft mold (embossed circuit pattern). Pour the fluoropolymer into the concave surface of the intermediate soft mold, centrifuge to make the fluoropolymer conform to the inner surface of the intermediate soft mold, and then heat it to fully cure it;

[0112] (3) The cured replica embossing soft mold is separated from the intermediate soft mold by a peeling demoulding method (demolding) to produce an embossing soft mold, such as Figure 2 (c)

[0113] (4) Flipping the replica embossing soft mold. Flip the inner and outer surfaces of the replica embossing soft mold, spray a release agent on the inner surface with microstructures to produce a working soft mold for embossing, and conformally attach a layer of conductive PET as a backing to the outer surface of the working soft mold for embossing. Figure 2 As shown in (d, e).

[0114] Step 3: Apply embossing glue on the surface of the curved substrate and emboss the circuit pattern.

[0115] The electric field assisted imprinting (force-electric synergistic imprinting) technology is used to conformally imprint on a ceramic substrate coated with an imprinting glue to replicate the groove structure of the circuit pattern, such as Figure 2 (e) is shown. The specific process is as follows:

[0116] (6) spraying a layer of embossing adhesive mixed with silver conductive particles on the surface of the ceramic substrate by a spraying method, and installing an electrode ring at the bottom of the substrate so that the electrode ring is in contact with the embossing adhesive;

[0117] (7) aligning the imprint working soft mold manufactured in step 2 with the substrate, and then conformally attaching it to the surface of the substrate and applying auxiliary gas pressure to achieve complete conformal contact between the soft mold and the three-dimensional ceramic substrate;

[0118] (8) Using electric field assisted imprinting technology, the electrode ring at the bottom of the ceramic substrate is connected to the negative electrode of the high-voltage power supply, and the conductive PET on the upper surface of the working soft mold is connected to the positive electrode of the high-voltage power supply. Through the applied electric field force, the imprinting glue fully fills the grooves on the mold surface. Under the dual action of air pressure and electric field force, the thickness of the residual layer is further reduced, and the soft mold structure is replicated on the imprinting glue;

[0119] (9) releasing the imprinting force (electric field force and gas-assisted pressure) and maintaining the shape for a period of time, and then irradiating with ultraviolet light for a certain period of time to completely cure the imprinting glue;

[0120] (10) After the embossing adhesive is completely cured, the soft mold is separated from the embossed pattern by peel-off demolding (demolding sequentially from the periphery to the center), thereby achieving efficient and high-precision preforming of three-dimensional graphics.

[0121] Step 4: Use etching technology to replicate a groove consistent with the conformal circuit on the substrate, and roughen and modify the surface of the groove. The specific process is as follows:

[0122] (5) Use laser to remove the residual layer of embossing;

[0123] (6) using the photoresist of the replicated pattern as a mask, wet-etching the ceramic substrate with an acidic etching solution consisting of 92-98 wt.% of concentrated sulfuric acid and 0.1-8 wt.% of cryolite, and 0.1-8 wt.% of boric acid, to etch a circuit pattern groove in the curved substrate;

[0124] (7) Use a degumming agent to remove all photoresist masks;

[0125] (8) A high-power laser is used to roughen the grooves of the curved substrate to form irregular micro-nano structures in the grooves of the curved substrate.

[0126] Step 5: Filling seed layer based on charge injection electrowetting and electric field driven jet micro-nano 3D printing.

[0127] (2) Use the printing module of the five-axis electric field-assisted fluid / laser multi-module three-dimensional surface graphics printing equipment to fill the grooves of the ceramic surface with nanosilver ink as the seed layer for the subsequent electroplating process. The conductive material is squeezed out of the print head under the action of electric field force, gravity, etc. and deposited into the grooves of the ceramic surface. Then, using the charge injection electrowetting effect, the charges on the inner surface of the substrate groove and the surface of the ink will show a tendency of opposite charges to attract each other, driving the ink to move downward, thereby filling the submicroscale grooves, such as Figure 2 (g) as shown.

[0128] Step 6: Precision electroplating deposits copper.

[0129] Using the electroplating process, copper is continuously electroplated and deposited on the seed layer of the curved substrate groove to completely fill the groove of the curved substrate with copper. Figure 2 (h). The specific process is as follows:

[0130] The sample prepared in step 5 was connected to the negative pole of the DC power supply by connecting the connecting wire from the seed layer, and the positive pole was connected to the copper plate. The sample was placed in a plating solution composed of 300 g / L copper sulfate and 20 g / L copper chloride for electroplating. The current density was set to 1 A / dm 2 , the electroforming time is about 5min.

[0131] Step 7: Laser melting heterogeneous interface strengthening.

[0132] Through high-intensity laser tracking processing of the conductor, the seed layer metal and the electroplated deposited metal are melted and combined, the heterogeneous interface is eliminated, and a highly conductive alloy is formed. At the same time, the molten metal fills the roughened grooves to further enhance the bonding force between the metal layer and the ceramic substrate. The specific process is as follows:

[0133] (3) Reinstall the electroplated workpiece onto the five-axis electric field-assisted fluid / laser multi-module three-dimensional surface graphics printing equipment. Use a positioning camera and alignment marks to align the workpiece on the printing equipment;

[0134] (4) Using laser 2 (high power mode), and following the planned circuit pattern printing path, the electroplated copper and seed layer are heated and melted, so that the molten metal is completely filled into the micro-nano structure of the roughened substrate groove. After the metal cools, an interlocking structure is formed between the metal and the roughened groove heterogeneous interface. The interlocking structure is used to achieve strong adhesion between the metal pattern and the substrate, such as Figure 2 (i) as shown.

[0135] Step 8: Post-processing of the curved substrate surface: Use a polishing machine to polish away the excess metal material outside the curved substrate groove and the part of the curved substrate groove filled with metal that is higher than the substrate surface. Figure 2 (j) shows. The manufacturing of curved conformal circuits is completed on curved substrates, such as Figure 2 (k) as shown.

[0136] Example 3

[0137] This example uses a fiber-reinforced (glass fiber, carbon fiber, aramid, etc.) polymer matrix material as a three-dimensional curved surface substrate to specifically illustrate the detailed process of the electric field-assisted three-dimensional curved surface embedded conformal circuit manufacturing method proposed in this application.

[0138] Step 1: Master mold manufacturing (large-size, non-spliced, non-developable surface micro-nano mold).

[0139] The processing object (ceramic substrate) is digitally inverted, and a self-developed five-axis linkage electric field driven melt jet deposition micro-nano 3D printer is used to print a polycaprolactone (PCL) pattern on a ceramic substrate as an imprint mold master. The PCL master mold in this embodiment is a wire grid structure with a line width of 500nm and a spacing of 500μm.

[0140] Step 2: Copy the embossing soft mold.

[0141] Using the PCL master template printed in step 1, a working soft mold for embossing is manufactured through a secondary mold replication process. The prepared working soft mold has the same characteristic structure as the PCL master template, with a convex structure line width of 500nm and a spacing of 500μm. The specific process is as follows:

[0142] (1) Replicate the intermediate soft mold (groove circuit pattern), pour the liquid PDMS material mixed with silver particles onto the master mold, heat and solidify it, and then use the peel-off demolding method to demold it to produce an intermediate soft mold, such as Figure 2 (b)

[0143] (2) Replicating the embossed soft mold (embossed circuit pattern). Pour the fluoropolymer into the concave surface of the intermediate soft mold, centrifuge to make the fluoropolymer conform to the inner surface of the intermediate soft mold, and then heat it to fully cure it;

[0144] (3) The cured replica embossing soft mold is separated from the intermediate soft mold by a peeling demoulding method (demolding) to produce an embossing soft mold, such as Figure 2 (c)

[0145] (4) Flipping the replica embossing soft mold. Flip the inner and outer surfaces of the replica embossing soft mold, spray a release agent on the inner surface with microstructures to produce a working soft mold for embossing, and conformally attach a layer of conductive PET as a backing to the outer surface of the working soft mold for embossing. Figure 2 As shown in (d, e).

[0146] Step 3: Apply embossing glue on the surface of the curved substrate and emboss the circuit pattern.

[0147] The electric field assisted imprinting (force-electric synergistic imprinting) technology is used to conformally imprint on a ceramic substrate coated with an imprinting glue to replicate the groove structure of the circuit pattern, such as Figure 2 (e) is shown. The specific process is as follows:

[0148] (11) spraying a layer of embossing adhesive mixed with silver conductive particles on the surface of the ceramic substrate by a spraying method, and installing an electrode ring at the bottom of the substrate so that the electrode ring is in contact with the embossing adhesive;

[0149] (12) aligning the imprint working soft mold manufactured in step 2 with the substrate, and then conformally attaching it to the surface of the substrate and applying auxiliary gas pressure to achieve complete conformal contact between the soft mold and the three-dimensional ceramic substrate;

[0150] (13) Using electric field assisted imprinting technology, the electrode ring at the bottom of the ceramic substrate is connected to the negative electrode of the high-voltage power supply, and the conductive PET on the upper surface of the working soft mold is connected to the positive electrode of the high-voltage power supply. Through the applied electric field force, the imprinting glue fully fills the grooves on the mold surface. Under the dual action of air pressure and electric field force, the thickness of the residual layer is further reduced, and the soft mold structure is replicated on the imprinting glue;

[0151] (14) releasing the imprinting force (electric field force and gas-assisted pressure) and maintaining the shape for a period of time, and then irradiating with ultraviolet light for a certain period of time to completely cure the imprinting glue;

[0152] (15) After the embossing adhesive is completely cured, the soft mold is separated from the embossed pattern by peel-off demolding (sequential demolding from the periphery to the center), thereby achieving efficient and high-precision preforming of three-dimensional graphics.

[0153] Step 4: Use etching technology to replicate a groove consistent with the conformal circuit on the substrate, and roughen and modify the surface of the groove. The specific process is as follows:

[0154] (9) Using laser to remove the residual layer of embossing;

[0155] (10) using the photoresist of the replicated pattern as a mask, wet-etching the ceramic substrate with an acidic etching solution consisting of 92-98 wt.% of concentrated sulfuric acid, 0.1-8 wt.% of cryolite, and 0.1-8 wt.% of boric acid to etch a circuit pattern groove in the curved substrate;

[0156] (11) removing all photoresist masks using a degumming agent;

[0157] (12) A high-power laser is used to roughen the grooves of the curved substrate to form irregular micro-nano structures in the grooves of the curved substrate.

[0158] Step 5: Filling seed layer based on charge injection electrowetting and electric field driven jet micro-nano 3D printing.

[0159] (3) Use the printing module of the five-axis linkage electric field assisted fluid / laser multi-module three-dimensional surface graphics printing equipment to fill the nanosilver ink in the groove of the ceramic surface as the seed layer for the subsequent electroplating process. The conductive material is squeezed out from the print head under the action of electric field force, gravity, etc. and deposited in the groove of the ceramic surface. Then, using the charge injection electrowetting effect, the charges on the inner surface of the substrate groove and the surface of the ink will show a tendency of opposite charges to attract each other, driving the ink to move downward, thereby filling the submicroscale grooves, such as Figure 2 (g) as shown.

[0160] Step 6: Precision electroplating deposits copper.

[0161] Using the electroplating process, copper is continuously electroplated and deposited on the seed layer of the curved substrate groove to completely fill the groove of the curved substrate with copper. Figure 2 (h). The specific process is as follows:

[0162] The sample prepared in step 5 was connected to the negative pole of the DC power supply by connecting the connecting wire from the seed layer, and the positive pole was connected to the copper plate. The sample was placed in a plating solution composed of 300 g / L copper sulfate and 20 g / L copper chloride for electroplating. The current density was set to 1 A / dm 2 , the electroforming time is about 5min.

[0163] Step 7: Laser melting heterogeneous interface strengthening.

[0164] Through high-intensity laser tracking processing of the conductor, the seed layer metal and the electroplated deposited metal are melted and combined, the heterogeneous interface is eliminated, and a highly conductive alloy is formed. At the same time, the molten metal fills the roughened grooves to further enhance the bonding force between the metal layer and the ceramic substrate. The specific process is as follows:

[0165] (5) Reinstall the electroplated workpiece onto the five-axis electric field-assisted fluid / laser multi-module three-dimensional surface graphics printing equipment. Use a positioning camera and alignment marks to align the workpiece on the printing equipment;

[0166] (6) Using laser 2 (high power mode), and following the planned circuit pattern printing path, the electroplated copper and seed layer are heated and melted, so that the molten metal is completely filled into the micro-nano structure of the roughened substrate groove. After the metal cools, an interlocking structure is formed between the metal and the roughened groove heterogeneous interface. The interlocking structure is used to achieve strong adhesion between the metal pattern and the substrate, such as Figure 2 (i) as shown.

[0167] Step 8: Post-processing of the curved substrate surface: Use a polishing machine to polish away the excess metal material outside the curved substrate groove and the part of the curved substrate groove filled with metal that is higher than the substrate surface. Figure 2 (j) shows. The manufacturing of curved conformal circuits is completed on curved substrates, such as Figure 2 (k) as shown.

[0168] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for additive manufacturing of non-developable surface micro-conformal circuits based on electric field drive, characterized in that: The following steps are involved: Step 1: Master mold manufacturing, using molten polymer material as printing material to print a large-sized, non-jointed, non-developable surface micro-nano master mold; Step 2: Replicate the embossing soft mold and manufacture a working soft mold for embossing through a secondary mold replication process; Step 3: Spread embossing glue on the surface of the curved substrate, cover the embossing working soft mold on the embossing glue, emboss the circuit pattern, and replicate the circuit pattern on the embossing glue; Step 4: Replicate a groove consistent with the conformal circuit on the curved substrate using etching technology, and perform roughening and optional modification on the surface of the groove; Step 5: Using nano-conductive ink, deposit a nano-conductive seed layer in the groove; Step 6: Precision electroplating and depositing conductive metal, continuing to electroplating and depositing conductive metal on the nano-conductive seed layer in the groove of the curved substrate, so that the metal material is completely filled in the groove of the curved substrate; Step 7: Laser melting heterogeneous interface strengthening, heating and melting the conductive metal and seed layer in the electroplating groove, so that the molten material is completely filled into the micro-nano structure of the roughened substrate groove, and the heterogeneous interface forms an interlocking structure to achieve strong adhesion between the conductive pattern and the substrate; Step 8: Post-process the surface of the curved substrate to remove excess metal on the surface of the curved substrate and complete the manufacture of the three-dimensional curved conformal circuit.

2. The method for additive manufacturing of non-developable curved surface micro-conformal circuits based on electric field drive according to claim 1, characterized in that: The master mold manufacturing in step 1 includes the following steps: (1) Using a processing machine tool to manufacture a physical model of the processing object; (2) Using thermoplastic polymer molten material as the printing material, a conformal circuit pattern is printed on the surface of the physical model to complete the manufacturing of the imprinted master mold.

3. The method for additive manufacturing of non-developable surface micro-conformal circuits based on electric field drive according to claim 1, characterized in that: The step 2 of replicating the embossed soft mold comprises the following steps: (1) Replicating the intermediate soft mold: pouring the first liquid material onto the master mold, and demolding after solidification to produce the intermediate soft mold; (2) Replicating the imprinted soft mold: pouring the second liquid material onto the intermediate soft mold and completely curing it; (3) Separating the replica embossing soft mold from the intermediate soft mold; (4) Flipping the replica embossing soft mold: Flip the replica embossing soft mold as a whole, spray a release agent on the surface, and manufacture a working soft mold for embossing.

4. The method for additive manufacturing of non-developable surface micro-conformal circuits based on electric field drive according to claim 1, characterized in that: The step 3 of coating the curved substrate surface with embossing glue to emboss the circuit pattern comprises the following steps: (1) coating a layer of embossing adhesive on the surface of the substrate; (2) aligning the imprint working soft mold manufactured in step 2 with the curved substrate, and applying pressure to achieve conformal contact between the soft mold and the curved substrate; (3) Replicate the soft mold structure on the imprint glue and reduce the thickness of the residual layer by applying air pressure and electric field force; (4) releasing the embossing force, maintaining the shape for a period of time, and then curing the embossing glue; (5) After the embossing adhesive is completely cured, the soft mold is separated from the embossed pattern by peel-off demolding, thereby achieving efficient and high-precision preforming of three-dimensional graphics.

5. The method for additive manufacturing of non-developable surface micro-conformal circuits based on electric field drive according to claim 1, characterized in that: The step 4 uses etching technology to replicate a groove consistent with the conformal circuit on the substrate, and roughens and modifies the surface of the groove, including the following steps: (1) Removing the embossing residual layer; (2) using the photoresist of the replicated pattern as a mask, and using wet etching to etch a circuit pattern groove in the curved substrate; (3) removing the photoresist; (4) Roughening the grooves of the curved substrate to form irregular micro-nano structures in the grooves of the curved substrate; and determining whether to further modify the grooves to achieve super-hydrophilicity according to needs.

6. The method for additive manufacturing of non-developable surface micro-conformal circuits based on electric field drive according to claim 1, characterized in that: The manufacturing of the seed layer in step 5 comprises the following steps: (1) Using nano conductive ink material as printing material, filling the nano conductive material ink into the groove; (2) The nano-conductive ink filled in the groove is sintered and made conductive to complete the manufacture of the nano-seed layer.

7. The method for additive manufacturing of non-developable curved surface micro-conformal circuits based on electric field drive according to claim 1, characterized in that: The precision electroplating deposition of conductive metal in step 6 comprises the following steps: The electroplating process is used to continuously deposit the conductive metal on the seed layer of the groove of the curved substrate, so that the groove of the curved substrate is completely filled with the metal material.

8. The method for additive manufacturing of non-developable curved surface micro-conformal circuits based on electric field drive according to claim 1, characterized in that: The laser melting heterogeneous interface strengthening in step 7 comprises the following steps: (1) Fixing the electroplated workpiece at a preset position; (2) Using a laser, the electroplated conductive metal and the seed layer are heated and melted according to the planned circuit pattern printing path. The molten metal is completely filled into the micro-nano structure of the roughened substrate groove. After the metal cools, an interlocking structure is formed at the heterogeneous interface between the metal and the roughened groove. The interlocking structure is used to achieve strong adhesion between the metal pattern and the substrate.

9. The method for additive manufacturing of non-developable curved surface micro-conformal circuits based on electric field drive according to claim 1, characterized in that: The surface post-treatment of the curved substrate in step 8 comprises the following steps: The excess metal material outside the groove of the curved substrate and the part of the metal filling the groove of the curved substrate that is higher than the surface of the substrate are removed to complete the manufacture of the curved conformal circuit on the curved substrate.

10. The method for additive manufacturing of non-developable surface micro-conformal circuits based on electric field drive according to claim 1, characterized in that: The melt printing material in step 1 includes one or more of polymethyl methacrylate (PMMA), polycaprolactone (PCL), and polylactic acid (PLA); The master mold manufacturing method in step 1 includes one or more of five-axis linkage electric field driven melt jet micro-nano 3D printing, electron beam lithography, femtosecond laser direct writing, and aerosol jet printing; The printing substrate in step 1 includes one or more of ceramic, glass, sapphire, and resin; The mold replication material in step 2 includes polydimethylsiloxane (PDMS) or fluoropolymer.

11. The method for additive manufacturing of non-developable curved surface micro-conformal circuits based on electric field drive according to claim 1, characterized in that: The method of coating the embossing adhesive on the surface of the curved substrate in step 3 includes a film-forming method or a spraying method; The embossing glue curing method in step 3 includes UV curing and heating curing; The etching method in step 4 includes wet etching or dry etching; The method for roughening the groove of the curved substrate in step 4 includes chemical roughening or laser roughening. In addition, further modification treatment can be performed as needed to achieve high hydrophilicity; The nano conductive ink curing method in step 5 includes heating curing or laser sintering curing; The electroplated conductive metal material in step 6 includes one or more of gold, silver, copper, and nickel; The surface post-treatment in step 8 includes one or more of polishing, laser cleaning, and plasma cleaning.

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