Forming method of 3D printing curved surface multilayer circuit vertical interconnection structure

Abstract

The invention provides a forming method of a 3D printing curved surface multilayer circuit vertical interconnection structure. According to the method, high-conductivity interconnection structures with different characteristics and smooth surfaces can be integrally formed in the process of additive manufacturing of a multilayer circuit, and meanwhile any space structure can be formed on the curved surface in an additive mode. The method is high in flexibility, can be easily integrated in an additive manufacturing link of a multilayer circuit, can integrally form various interconnection structure features with different diameters and types, and avoids the problems that various modes need to be switched and some features cannot be formed in the prior art. In addition, a space special-shaped metal structure can be formed on an existing curved-surface circuit board in a printing mode, the circuit function is further expanded, and manufacturing of miniature antennas and sensors can be achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of conformal circuit manufacturing, and specifically relates to a molding method for a 3D printed curved multilayer circuit vertical interconnection structure. The method is an additive manufacturing method for a curved multilayer vertical interconnection structure, and is mainly used to realize vertical interconnection between curved multilayer circuits and ensure the integrity of electrical signals between the curved multilayer circuits. Background Art

[0002] As a key process for moving from separate multi-layer circuits to integrated circuits, vertical interconnection holes are designed in the manufacturing process of PCB boards to ensure the interconnection of electrical signals between multi-layer circuits, such as buried blind holes and metallized through-hole structures. Usually, the production of these through-holes is mainly achieved by chemical plating and plugging processes. The specific process is to form a through hole in the middle core board by mechanical drilling or laser etching, and then form a hole wall metallization by chemical plating or fill it with metal slurry (copper slurry, silver slurry, etc.) and solidify it to achieve the connection between the upper and lower layers, and then cover other metal layers. In engineering, for chemical plating and plugging of blind holes, due to the influence of hole diameter and depth, the chemical plating solution or plugging slurry cannot completely enter the hole, resulting in poor interconnection and conduction effect. Therefore, it is not recommended to use similar process treatments.

[0003] Most of the interconnection structures in existing curved multilayer circuits still draw on the realization ideas of interconnection holes in traditional PCBs, and use chemical plating, metal slurry plugging and mechanical interconnection methods (such as pins, springs, etc.) to realize the interconnection of curved multilayer circuits. For example: the interconnection holes of the multilayer housing in Chinese patent CN114552200B use chemical plating or sputtering technology to realize the interconnection of the upper and lower circuits of the curved housing; the formation of the interconnection holes announced in Chinese patent CN111613888B is achieved by mechanical drilling and laser drilling, and then the process of laser activation assisted chemical plating is used to realize the preparation of the interconnection holes, which is still a chemical plating process in essence; Chinese patent CN109755760B discloses the use of laser drilling + filling metal slurry to realize the connection of the upper and lower circuits; Chinese patent applications CN117096596A, CN117276879A, and CN117525873A disclose the use of spring pins, springs and rivets to realize the interconnection between curved multilayer circuits. In the process of preparing the dielectric layer and the conductor layer by integrating additive manufacturing, the above process will face the following problems: secondary positioning error caused by drilling + chemical plating, the inability to connect tiny blind holes by chemical plating and slurry plugging, in addition, online drilling makes it impossible to remove the debris at the bottom of the blind hole, laser drilling easily forms a conical structure, and there are different degrees of resin residues at the bottom of the hole due to focal length deviation on the curved surface, which will affect the connectivity effect.

[0004] Chinese patent application CN117712031A discloses the use of nano silver paste (silver powder: epoxy resin = 90:10) 3D printing to make vertical interconnection columns. After positioning, the conductive glue is still used to achieve the conduction between the upper and lower layers. The specific implementation details and effects are not discussed in detail. It is inferred that the self-supporting property of the paste is used to achieve a certain column height, but the printable height of the vertical column is limited and it is easily skewed due to gravity bias. The end face of the column is easily affected by the extrusion-type glue breakage, resulting in different wire drawing effects, and it is impossible to form a regular cone or flat end face. Chinese patent CN112123950B discloses the use of ceramic ink and conductive ink to alternately print to form metal columns or conductive rings, thereby achieving conductive interconnection. However, the flow of conductive ink and the surface tension climbing phenomenon of dielectric materials will cause the formed column to be similar to a "pagoda-shaped" stacking interface. The smaller the printing alternate layers, the "pagoda-shaped" stacking interface will evolve into a "hair-like" edge, resulting in a rough surface of the interconnection column, which has a great impact on high-frequency signal transmission.

[0005] Additive manufacturing of curved conformal integrated circuits is one of the important trends in the development of heterogeneous integrated circuits. How to achieve an interconnection structure with a smooth surface and reliable conductivity during the integrated manufacturing process of heterogeneous materials has become the key to improving the performance of additively manufactured electronic devices. Summary of the invention

[0006] The purpose of the present invention is to solve the shortcomings of the current additive manufacturing of curved multi-layer circuit interconnect structure molding, and to provide a 3D printing curved multi-layer circuit vertical interconnect structure molding method. This method can realize the integrated molding of high-conductivity interconnect structures with different features and smooth surfaces in the process of additive manufacturing of multi-layer circuits, and can additively mold any spatial structure on the curved surface. This method is highly flexible and easy to integrate into the additive manufacturing process of multi-layer circuits. It can integrate a variety of interconnect structure features with different diameters and types, avoiding the problem that the prior art needs to switch between multiple methods and that certain features cannot be molded. In addition, by printing, spatial special-shaped metal structures can be molded on existing curved circuit boards, further expanding the circuit function, and realizing the manufacture of micro antennas and sensors.

[0007] To achieve the above purpose, the technical solution provided by the present invention is:

[0008] A method for forming a 3D printed curved multilayer circuit vertical interconnection structure, which is special in that it includes the following steps:

[0009] Step 1: Install the medium substrate on a work platform with rotatable and movable functions, heat the medium substrate so that its surface temperature is always controlled above 120°C during the interconnection structure forming process, and at the same time, ensure that the axis of the print head of the 3D printing device is always kept in the direction of gravity;

[0010] The above-mentioned working platform can ensure that the medium substrate can rotate or translate at various angles, so as to facilitate the control of the angle between the normal of the deposited curved surface and the axis of the print head; the above-mentioned control of the surface temperature of the medium substrate is mainly to facilitate the rapid solidification of the deposited nanometal material, and the solidified metal layer can quickly conduct heat to ensure that the subsequent deposited material can quickly condense, thereby ensuring the continuous growth of the interconnected structure; and the main purpose of ensuring that the axis of the print head is always kept in the direction of gravity is that the ink droplets need to be ensured to fall vertically in the direction of gravity during the jet deposition process in order to control the deposition accuracy of the ink droplet landing point, otherwise the slight deflection of the print head will cause the flight trajectory of the ink droplets to be uncontrollable due to gravity factors;

[0011] Step 2: The position of the medium substrate is adjusted through the working platform so that the angle between the axis of the print head and the normal of the deposited curved surface of the medium substrate meets the printing requirements; the metal is deposited layer by layer to a specified height on the medium substrate according to the interconnection structure characteristics by using a 3D printing device to form an interconnection structure;

[0012] Step 3: using a 3D printing device to print a dielectric layer around the interconnection structure formed in step 2 using a dielectric resin and solidify the dielectric layer; wherein an isolation zone is provided between the dielectric layer and the interconnection structure;

[0013] When a low-viscosity dielectric resin is used to print a dielectric layer on a curved surface, the filling efficiency of the dielectric layer is very low. If the printed layer is too thick, it is easy to flow and spread due to gravity, resulting in uncontrollable thickness of the dielectric layer. If the printed layer is too thin, the molding efficiency of the dielectric layer is too low, and efficient engineering application cannot be achieved. Therefore, in order to avoid this situation, a dielectric resin with a relatively high viscosity (greater than or equal to 100 cP) is usually used to print the dielectric layer. However, when the viscosity of the printed dielectric layer is relatively high, a pillar climbing phenomenon will occur on the main body of the interconnect structure, and then a dielectric resin "eight"-shaped wrapping phenomenon will be formed around the end face of the interconnect structure. The ink subsequently deposited on the interconnect structure or connecting the interconnect structure wires will spread on the interface of the dielectric resin, resulting in the formation of a connection structure similar to an "eight"-shaped protrusion at the connection when printing the circuit connected to the interconnect structure, affecting the quality and reliability of the connection. Therefore, the present invention first arranges an isolation belt between the interconnect structure and the dielectric layer, and then uses a low-viscosity and low-surface-tension dielectric resin to fill the isolation belt. At this time, the pillar climbing phenomenon will be greatly improved due to the low surface tension of the dielectric resin in the isolation belt; at the same time, the dielectric layer previously printed with a higher-viscosity dielectric resin will also form a fence after curing, which also overcomes the spreading problem faced by printing a low-viscosity dielectric resin on a curved surface.

[0014] Of course, in actual operation, if it is necessary to use a dielectric resin with a lower viscosity (less than 100 cP) to print the medium layer due to certain requirements, if the process design and other means can be used to print the medium layer thickness that meets the molding efficiency and allows the surface tension of the medium layer to overcome gravity to avoid flow and spreading, then there is no need to set an isolation belt.

[0015] Step 4: Use 3D printing equipment to fully fill the isolation zone with dielectric resin and solidify it to make the isolation zone reach the specified height;

[0016] The dielectric resin used in the isolation tape and the dielectric resin used in the dielectric layer are of the same type or mutually compatible resin types, but the surface tension and viscosity of the dielectric resin used in the isolation tape are lower than the surface tension and viscosity of the dielectric resin used in the dielectric layer;

[0017] When filling the isolation zone, in order to prevent the uncured material in the filling area from flowing during the substrate flipping and moving process, generally after one isolation zone is filled and cured, the dielectric substrate is moved or flipped to switch to the isolation zone of the next interconnected structure for filling and curing;

[0018] Step 5: In order to expand the engagement area of ​​the interconnection structure so that it can be reliably connected to the circuit, a metal ring belt sheet layer needs to be printed along the circumference of the upper and lower ends of the interconnection structure, and then the circuit layer of the same layer is printed to connect with the metal ring belt sheet layer;

[0019] Step 6: Repeat steps 2 to 5 to form other interconnect structures on the surface of the dielectric substrate to complete the forming of the curved multi-layer circuit vertical interconnect structure; during the repetitive process, the surface temperature of the dielectric substrate must always be maintained above 120°C, because the filling of the isolation zone may affect the thermal conductivity of the dielectric substrate on which the resin is spread. As the resin thickens, the surface temperature will become lower and lower. If the surface temperature is too low, the metal ink will collapse and spread and cannot effectively form the body structure. Therefore, the temperature needs to be maintained above 120°C to ensure the solidification and spreading of the metal ink.

[0020] Furthermore, in step 2, piezoelectric inkjet is used to spray nano-metal ink, aerosol to spray nano-metal ink, or ion particle atomization spray deposition plasma atomized metal particles to form an interconnection structure on the dielectric substrate; specifically, piezoelectric inkjet and aerosol are mainly used to spray nano-scale metal inks (such as: nano-gold, nano-nickel, nano-copper, nano-silver, etc., and metalized inks with higher thermal conductivity are preferred in actual operation), while ion particle atomization spray deposition plasma atomized metal particles, the nozzle of the metal particles is accompanied by a laser for micro-melting treatment when the metal particles are ejected, and solidification and deposition are performed after falling on the substrate. Of course, you can also choose to use micro-pen direct writing technology to print low-melting point or eutectic metal materials (such as: eutectics composed of monomers or multiple compositions of metals such as tin, bismuth, indium, etc.), and by heating and extruding the molten material, it relies on surface tension and air cooling and solidification after extrusion to form a self-supporting interconnection structure, but the size of the interconnection structure formed in this way is relatively single size;

[0021] The interconnection structure is a solid core, thin-walled structure of a column, a tubular body or other arbitrary shapes; wherein, the size of a solid interconnection structure such as a column is not less than 50 μm, and the wall thickness of a tubular or thin-walled interconnection structure is not less than 100 μm. The formed interconnection structure can grow into any spatial structure in cooperation with the bottom working platform, for example, it can form a special structure such as a spatial cone or spiral, and laser irradiation heat transfer can be used on the formed interconnection structure to assist the growth of structural features. This is because the area of ​​the interconnection structure feature body that interacts with the air will gradually increase with the growth height, and the heat transfer efficiency to the growth surface will become lower and lower, thereby reducing the effect of ink droplet accumulation or possibly causing the inability to accumulate and form; therefore, in order to ensure that the growth surface of the interconnection structure maintains a certain temperature, laser irradiation can be used on the printed interconnection structure to increase the heat input of the printed structure and increase the temperature of the printing surface to compensate for the heat loss caused by its interaction with the air.

[0022] Furthermore, in step 2, the angle between the print head axis and the normal of the deposited curved surface of the medium substrate is 0 to ±45°. The print head axis is always kept in the direction of gravity. Normally, the print head axis coincides with the normal of the deposited curved surface, that is, the angle is 0°, but this cannot be satisfied in some interference scenarios. At this time, the maximum angle between the print head axis and the normal of the deposited curved surface can be controlled within the range of ±45°, which is mainly achieved by adjusting the position of the deposited curved surface through the working platform.

[0023] Furthermore, different from linear filling, in order to avoid the frizzy phenomenon on the edge, in step 2, the track deposited layer by layer to a specified height according to the interconnection structure characteristics is filled from the outside to the inside in a "U" shape;

[0024] For solid interconnection structures, the center area is reserved with a diameter of at least 60 to 100 μm as a non-printing filling area (the non-printing filling area does not need to be processed later, and the printing ink will automatically level out). This is because the printing line speed will gradually accumulate when the center area is filled in a circular pattern. If it is lower than 60 μm, the middle area will be high. The upper limit of the reserved diameter is set because if it is higher than 100 μm, the middle area will be concave later.

[0025] The specified height of the interconnection structure is greater than or equal to the thickness of the medium that passes through the two connected layers of circuits. The height of the printed interconnection structure can be formed in one step according to the height of the medium of the circuit layer to which it is connected without interfering with the filling of the surrounding dielectric resin (i.e., the filling isolation zone). The purpose is to avoid multiple stacking prints during the deposition process to cause joints (for example: the thickness of the medium between the two layers of circuits is 0.3mm, and the height of the interconnection column printed for the first time is 0.14mm. In this case, the interconnection column needs to be printed for the second time until the 0.3mm medium between the two layers of circuits is passed through; in this process, the printing of the interconnection column is divided into two times, so a joint will be formed on the column of the interconnection column. Although filling the dielectric resin can improve it, the characteristics of the joint position can still be clearly seen from the cross-section structure, so it is best to print to the specified height in one step); of course, the height of the interconnection structure is preferably higher than the thickness of the medium between the two connected layers of circuits to ensure the connectivity between subsequent circuits.

[0026] Furthermore, in step 3, the width of the isolation zone is less than or equal to 200 μm.

[0027] Furthermore, in step 4, under heating, the surface tension of the dielectric resin used to fill the isolation tape is lower than 15 dyn / cm, and the viscosity is lower than 12 cP to ensure that it naturally flows and fully fills the isolation tape. The material surface tension and viscosity of the material that meet this requirement by heating by a print head can also be applied; the expansion coefficient after curing is lower than 60 ppm to prevent the interconnect structure from cracking due to the mismatch between the expansion and contraction of the interconnect structure and the thermal service environment in the later stage.

[0028] In order to prevent the low-viscosity dielectric resin from infiltrating and covering the end face of the interconnection structure and affecting the conductivity of the subsequent sections, the isolation zone after filling is 30 to 70 μm lower than the upper end face of the interconnection structure. In addition, the central area of ​​the thin-walled structure or tubular interconnection structure is filled with printed low-viscosity dielectric resin, and the end face of the central area after filling is 30 to 70 μm lower than the upper end face of the interconnection structure, which is basically flush with the upper end face of the isolation zone.

[0029] Furthermore, in order to effectively ensure the stability of the interconnection structure, in step 5, the thickness of the metal ring belt sheet layer is consistent with the thickness of the same layer of the circuit layer, and the width of the metal ring belt is not less than 150μm. The specific width can be designed according to the actual multi-layer circuit.

[0030] Furthermore, the curing and shaping in step 3 and step 4 are both achieved by ultraviolet light.

[0031] At the same time, the present invention also provides a curved multilayer circuit board, which is special in that the vertical interconnection structure thereon is formed by the above-mentioned method. In addition, secondary additive manufacturing can be performed on the existing curved multilayer structure; the curved multilayer circuit board can ultimately be used for micro antennas, sensors, waveguides, inductors, and radio frequency shielding, etc.

[0032] The advantages of the present invention are:

[0033] 1. The forming method of the 3D printed curved multilayer circuit interconnection structure provided by the present invention is simpler than the existing process production process. During the process, there is no need to switch multiple tools with different diameters and grouting and filling treatment. Not only can interconnection structures with different diameters and different features be formed on the curved substrate at one time, for example: interconnection feature structures with different diameters such as φ150μm, φ250μm, φ320μm, and different shapes of elliptical bodies, square bodies, and annular columns, and even some special-shaped structures can be formed on the curved substrate at one time by printing, the size of the printed graphics can also be digitally controlled, and then grown into conductive columns of different sizes, which is easier to integrate into the additive manufacturing process of multilayer circuits.

[0034] 2. The interconnection structure forming method of the present invention can form a micro-metal interconnection structure in any space by growing in cooperation with the bottom working platform under unsupported conditions, thus solving the problem that the existing process cannot be manufactured.

[0035] 3. The interconnect structure forming method of the present invention can realize the interconnection between curved multi-layer circuits with high efficiency and high quality. The formed interconnect structure has a smooth surface and high conductivity, which can effectively reduce the loss caused by the electrical interconnection between layers caused by processes such as plugging holes, and realize the application of higher frequency bands. It is highly compatible with the integrated manufacturing process and easy to integrate, which can further promote the development of additive manufacturing multi-layer circuits.

[0036] 4. The interconnect structure forming method of the present invention controls the angle between the print head and the normal direction of the medium substrate surface by cooperating with the working platform, and always keeps the printing direction as the gravity direction. Not only can an interconnect structure of any angle be grown on the curved surface (the interconnect structure can be along any surface normal), but also different branch structures can be generated by secondary printing based on the printed interconnect structure. It can be applied to devices such as micro antennas, sensors, and inductors, and can be expanded in functionality through secondary manufacturing based on the existing circuit board structure, and has great application potential. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1The conventional interconnection structure shown in the present invention, wherein a is a metal pillar interconnection structure without a metal substrate, b is a metal pillar interconnection structure with a metal substrate, c is a metal tubular interconnection structure without a metal substrate, and d is a metal tubular interconnection structure with a metal substrate;

[0038] Figure 2 A schematic diagram of printing annular band layers at the top and bottom of interconnect pillars according to the present invention;

[0039] FIG3( a ) is a schematic diagram of a metal interconnect structure printed on a curved substrate;

[0040] FIG3( b ) is a process of filling dielectric material around the curved substrate interconnect structure;

[0041] FIG3( c ) is a schematic diagram of a secondary printed interconnection structure on a curved medium surface;

[0042] Figure 4 It is a schematic diagram of a curved surface printed spatial heterogeneous interconnection structure;

[0043] Figure 5 Print interconnect pillar morphologies with different numbers of layers for curved surfaces;

[0044] Figure 6 Vertical connection structure for printing curved multi-layer circuits;

[0045] Figure 7 X-ray scanning for printing curved multi-layer circuit interconnect structures;

[0046] Figure 8 Filling dielectric materials for curved surface printed multi-layer circuit interconnection structures;

[0047] Fig. 9 This is a cross-sectional view of a vertical interconnection column;

[0048] Fig.10 It is a schematic diagram of the inner and outer filling resin of the wall tube type interconnection structure;

[0049] Reference numerals:

[0050] 100-substrate; 101-metal substrate; 102-metal column; 103-metal wall tube; 104-metal ring belt sheet layer; 201-print head; 301-medium layer; 302-isolation belt; 401-main column; 402-branch column I; 403-branch column II. DETAILED DESCRIPTION

[0051] The present invention is a method for preparing a typical characteristic structure of a curved conformal multilayer circuit, and is a molding method for preparing a vertical interconnection structure of a curved multilayer circuit using 3D printing technology. The method uses piezoelectric inkjet, aerosol or ion particle atomization spray deposition and other methods to print and grow metal columns or metal wall tubes along the normal direction on the surface of a curved medium substrate, and the printing height is as high as possible from the thickness of the medium that runs through the two connected layers of lines; when printing the medium layer, an isolation zone is reserved around the metal column or metal wall tube, and then a light-curable dielectric resin material with low surface tension and low viscosity is selected to print and fill the isolation zone and the inside of the metal wall tube (for large-sized wall tube types, resin slurry needs to be filled to make the thickness of the inner and outer resin layers as consistent as possible, such as Fig.10 As shown, otherwise the subsequent resin layers cannot be stacked and formed), ensuring that the isolation belt and the internal filling height are 30 to 70 μm lower than the end face of the interconnection structure; printing a metal ring belt sheet layer around the outer sides of the upper and lower ends of the formed metal column / metal wall tube to ensure the reliability of the connection between the interconnection structure and the circuit layer.

[0052] In order to further illustrate the specific content of the present invention, the following is a detailed description of the process of forming a curved multi-layer circuit vertical interconnection structure in conjunction with the accompanying drawings and implementation examples. The specific process is shown in the following implementation example.

[0053] Embodiment 1:

[0054] This implementation case mainly describes the process of interconnection column printing and medium filling involved in the present invention.

[0055] The printing equipment is a five-axis electronic device additive manufacturing system (5X-3DPES) produced by Xi'an Ruite 3D Technology Co., Ltd.; the print head is a piezoelectric inkjet head with a nozzle of 50μm produced by Xi'an Ruite 3D; the printing material is nanosilver conductive ink (d50<60nm); the resin material of the printing medium layer is acrylic resin (viscosity 18000cP), and the resin material of the filling isolation belt is also acrylic resin (viscosity: 10cP, surface tension 23dyn / cm); the designed interconnection column has a diameter of 300μm and a height of 2mm; the flat substrate is a polyimide film, and the curved substrate is an aluminum alloy metal block that has been anodized and insulated. The specific steps are:

[0056] Step 1: Install and fix the polyimide film or aluminum alloy metal block on the turntable of the five-axis printing equipment. The temperature of the substrate surface is raised to 130℃±2℃ by controlling the heating program and infrared temperature measurement feedback. After the substrate surface temperature is kept stable, the turntable is controlled to move so that the deposited surface is perpendicular to the axis of the print head (the angle between the normal direction of the curved surface and the axis of the print head is 0°), and at the same time, ensure that the axis of the print head always remains in the direction of gravity;

[0057] Step 2: After the piezoelectric inkjet is used to adjust the inkjet parameters of the nanosilver ink, the printing track of the interconnected metal column is processed. Among them, the area within 60 μm of the center of the interconnected metal column is not filled, and the overall track is filled in a "U" shape. The interconnected metal column is printed on the flat polyimide film and the curved metal substrate, respectively, with different numbers of layers printed; Printing instructions Figure 1 As shown in Figure 3(a), the actual printing of interconnected metal pillars is shown in Figure 5 and Figure 6 .in, Figure 5 The printing growth of interconnected metal pillars with and without a metal substrate chassis was tested respectively. In the case of a metal substrate, the root of the conductive interconnect pillar is smaller, and with the same number of printing layers, the height is higher than that without a metal substrate.

[0058] Step 3: Print acrylic dielectric resin (viscosity 18000 cP) around the interconnected metal pillar structure, control the width of the isolation zone to 300 μm, and actually the isolation zone is only about 100 μm wide after the resin spreads and flows, and use 365 nm ultraviolet irradiation to achieve dielectric resin curing and shaping;

[0059] Step 4: Fill the isolation belt with acrylic resin (viscosity: 10 cP, surface tension 23 dyn / cm), ensuring that it fully fills the isolation belt. Immediately after filling each isolation belt, use UV irradiation to cure it, and then switch to the next isolation belt through the turntable to print the filling resin for filling and curing;

[0060] Step 5: After the isolation belt is printed and reaches a height of 1.95 mm as measured by a visual camera, it is 50 μm below the metal cylinder surface; a metal ring belt sheet layer with a diameter of 500 μm is printed around the end surface of the interconnect structure (such as Figure 2 As shown), the printing thickness is 10 μm, and a 10 μm conductive line of this layer is printed around the printed metal ring belt; see Figure 7 and Figure 8 shown.

[0061] Step 6: Repeat steps 2 to 5 to form a new interconnection structure on the surface of the dielectric substrate, as shown in FIG3(c). The temperature rise procedure is controlled so that the surface temperature reaches 130°C after the acrylic resin is filled. Fig. 9 It can be seen from the cross-section of the overall interconnected metal pillar that the edge of the interconnected metal pillar is relatively smooth, the internal structure formed by the cross-section is relatively dense, and the formed interconnected metal pillar can reach about 260μm.

[0062] Embodiment 2:

[0063] This implementation case is mainly to further illustrate that the molding method of the present invention can be used to print and grow any metal interconnection structure on the surface of a curved substrate.

[0064] The printing equipment is a five-axis electronic device additive manufacturing system (5X-3DPES) produced by Xi'an Ruite 3D Technology Co., Ltd.; the print head is a piezoelectric inkjet head with a nozzle of 30μm produced by Xi'an Ruite 3D; the printing material is nanosilver conductive ink (d50<20nm); the designed interconnected structure is in the shape of a spatial tree branch, with a main column diameter of 600μm and a height of 1.2mm; the branch column diameter is 250μm and the branch length is 0.6mm. The selected substrate is an aluminum alloy block with an anodized surface insulation treatment; the specific steps are:

[0065] Step 1: The aluminum alloy metal block 100 is mounted and fixed on the turntable of the five-axis printing equipment. The temperature of the substrate surface is raised to 150°C±5°C by controlling the heating program and infrared temperature measurement feedback. After the substrate surface temperature is kept stable, the turntable is controlled to move so that the deposited surface is perpendicular to the axis of the print head (i.e., the angle between the normal direction of the curved surface and the axis of the print head is 0°), and at the same time, the axis of the print head is ensured to always remain in the direction of gravity;

[0066] Step 2: After the piezoelectric inkjet is used to adjust the inkjet parameters of the nanosilver ink, the printing track of the interconnected structure is processed, wherein no filling process is performed within 60 μm of the center of the main column, and the overall track is filled in a "U" shape, and the interconnected metal column is printed on the curved metal substrate, and the main column 401 is printed to a height of 1.2 mm;

[0067] Step 3: By adjusting the turntable so that the axis of the main column 401 is 90° with the printing axis, the branch column I 402 is deposited on the surface of the main column 401 by inkjet printing until the height is 600 μm, and then the turntable is adjusted so that the main column 401 is rotated 60° every time to print a pillar until all the branch column I 402 are printed;

[0068] Step 4: Continue to adjust the turntable so that the print head axis and the main column 401 axis are at an angle of 45°. In addition, a 0.1w 1064nm laser is used on the main column 401, and the defocused spot is controlled at 200μm for irradiation treatment; the surface temperature of the branch column I 402 has reached 165°C. Continue to use piezoelectric inkjet to continue printing branch column II 403 on branch column I 402. After each printing is completed, the turntable is adjusted to the next branch column I 402 to print branch column II 403 until all branch columns II 403 are printed; the overall schematic diagram of the completed dendritic interconnection structure is as follows: Figure 4 shown.

[0069] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should be included in the protection scope of the present invention.

Claims

1. A method for forming a 3D printed curved multi-layer circuit vertical interconnection structure, characterized in that: The following steps are involved: Step 1: Install the medium substrate on a work platform with rotatable and movable functions, heat the medium substrate so that its surface temperature is always controlled above 120°C during the interconnection structure forming process, and at the same time, ensure that the axis of the print head of the 3D printing device is always kept in the direction of gravity; Step 2: The position of the medium substrate is adjusted through the working platform so that the angle between the axis of the print head and the normal of the deposited curved surface of the medium substrate meets the printing requirements; the metal is deposited layer by layer to a specified height on the medium substrate according to the interconnection structure characteristics by using a 3D printing device to form an interconnection structure; Step 3: using a 3D printing device to print a dielectric layer around the interconnection structure formed in step 2 using a dielectric resin and solidify the dielectric layer; wherein an isolation zone is provided between the dielectric layer and the interconnection structure; Step 4: Use 3D printing equipment to fully fill the isolation zone with dielectric resin and solidify it to make the isolation zone reach the specified height; The dielectric resin used in the isolation tape and the dielectric resin used in the dielectric layer are of the same type or mutually compatible resin types, and the surface tension and viscosity of the dielectric resin used in the isolation tape are lower than the surface tension and viscosity of the dielectric resin used in the dielectric layer; Step 5: Printing a metal ring belt sheet layer circumferentially along the upper and lower ends of the interconnection structure, and then printing a circuit layer on the same layer to connect with the metal ring belt sheet layer; Step 6: Repeat steps 2 to 5 to form other interconnect structures on the surface of the dielectric substrate to complete the formation of the vertical interconnect structure of the curved multilayer circuit.

2. The method for forming a 3D printed curved multi-layer circuit vertical interconnection structure according to claim 1, characterized in that: In step 2, piezoelectric inkjet is used to spray nano-metal ink, aerosol spray nano-metal ink, or ion particle atomization spray deposition plasma atomized metal particles to form an interconnection structure on the dielectric substrate; The interconnection structure is a solid, thin-walled structure in a column, a tube or other shapes.

3. The method for forming a 3D printed curved multilayer circuit vertical interconnection structure according to claim 1 or 2, characterized in that: In step 2, the angle between the axis of the print head and the normal of the deposited curved surface of the medium substrate is 0 to ±45°.

4. The method for forming a 3D printed curved multi-layer circuit vertical interconnection structure according to claim 3, characterized in that: In step 2, the track deposited layer by layer to a specified height according to the interconnection structure characteristics is filled from the outside to the inside in a "U" shape; For solid interconnect structures, a central area with a diameter of at least 60 to 100 μm is reserved as a non-printing filling area; The specified height of the interconnection structure is greater than or equal to the thickness of the medium penetrating between two layers of connected circuits.

5. The method for forming a 3D printed curved multi-layer circuit vertical interconnection structure according to claim 4, characterized in that: In step 3, the width of the isolation zone is less than or equal to 200 μm.

6. The method for forming a 3D printed curved multi-layer circuit vertical interconnection structure according to claim 5, characterized in that: In step 4, under heating, the surface tension of the dielectric resin used to fill the isolation tape is less than 15 dyn / cm, the viscosity is less than 12 cP, and the expansion coefficient after curing is less than 60 ppm; The filled isolation zone is 30 to 70 μm lower than the upper end surface of the interconnection structure.

7. The method for forming a 3D printed curved multi-layer circuit vertical interconnection structure according to claim 6, characterized in that: In step 5, the thickness of the metal ring belt sheet layer is consistent with the thickness of the circuit layer on the same layer, and the width of the metal ring belt is not less than 150 μm.

8. The method for forming a 3D printed curved multi-layer circuit vertical interconnection structure according to claim 7, characterized in that: The curing and shaping in step 3 and step 4 are both achieved by ultraviolet light.

9. A curved multi-layer circuit board, characterized in that: The vertical interconnection structure thereon is formed by the method described in any one of claims 1-8.

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