A method and apparatus for thermal gas flow assisted laser sintering of conductive silver paste tracks

Abstract

The application discloses a hot air flow assisted laser sintering method and device for conductive silver paste circuit, relates to the technical field of 3D printing of conductive silver paste circuit, and the sintering method comprises the following steps: adopting hot air flow in front and laser beam in back to synchronously scan and sinter the conductive silver paste circuit deposited on the circuit substrate once, the application introduces low-temperature hot air flow pre-sintering before the laser beam sintering of the conductive silver paste circuit, preferentially thermally decomposes the organic matter coated on the surface of silver particles, and provides polymerization force for the silver particles in a dispersed state after the organic matter volatilization under the air flow pressure and inhibits the growth of air hole defects, so that the grain boundary diffusion and neck growth of the silver particles are greatly promoted when sintering, the sintering process has higher circuit densification degree, better conductive performance, effectively inhibits circuit expansion, and has a smooth circuit surface morphology, so that the ablation of the substrate is avoided and the sintering efficiency is greatly improved.

Description

Technical Field

[0001] This invention relates to a hot airflow-assisted laser sintering method and apparatus for conductive silver paste circuits, belonging to the field of 3D printing technology for conductive silver paste circuits. Background Technology

[0002] Structure-circuit integrated additive manufacturing technology is an advanced manufacturing technology developed by integrating mature additive manufacturing technology with new materials and processes. It uses fused deposition modeling (FDM) to form complex structures, and simultaneously employs direct ink writing (DIW) and inkjet printing (IJP) technologies to print conductive silver paste lines on the structure and sinter them to form the circuitry within the structure. Electronic components are then embedded in-line, ultimately creating electronic products containing structures, circuitry, and electronic components. This manufacturing technology has enormous potential and broad commercial application prospects.

[0003] During the sintering of conductive silver paste circuits, due to the temperature resistance limitations of the conductive silver paste circuit substrate (structure) and the requirements of online sintering, the most suitable sintering process for conductive silver paste circuits is currently laser sintering. This involves directly applying a laser beam to the surface of the conductive silver paste circuit. The diameter of the laser spot is smaller than the linewidth, thus avoiding the ablation of the substrate by the laser beam. Because the laser spot energy is concentrated, the scanning speed on the surface of the conductive silver paste circuit is relatively fast, resulting in high sintering efficiency.

[0004] Currently, laser-sintered conductive silver paste circuits not only suffer from severe internal porosity defects, resulting in low density and poor conductivity, but the growth of these defects also causes the conductive silver paste circuits to expand, leading to surface bumps. This is because the high-energy laser beam directly sintersects the conductive silver paste circuits. Due to the high operating temperature, while the reaction temperature required for the decomposition and volatilization of organic matter in the silver paste is relatively low, the rapid and intense decomposition and volatilization of organic matter under high temperature causes a large amount of gaseous and decomposed gases to disturb the interior of the conductive silver paste circuits, forming pores. Furthermore, at the high temperature, silver particles also simultaneously polymerize and solidify, solidifying the pore structure within the conductive silver paste circuits and forming porosity defects. This results in low internal density, high resistivity, and poor conductivity. In addition, the densification of the conductive silver paste circuit surface prevents the volatilization of internal gases, leaving the gases trapped beneath the dense surface layer. The continued expansion of these gases causes the conductive silver paste circuits to passively expand and bulge, forming bumps. This makes the surface of the conductive silver paste circuits rough and inconsistent.

[0005] Based on the above research, it was found that the thermal reaction characteristics of conductive silver paste circuits exhibit the characteristic that the decomposition and volatilization of organic matter requires a relatively low temperature reaction, while the agglomeration of silver particles requires a high energy level. Therefore, the sintering temperature curve of high-quality sintered conductive silver paste circuits should be a step-like temperature change process, starting low and then increasing. However, the single energy supply of laser sintering cannot simultaneously meet the combined low and high temperature changes. Therefore, the limitations of the laser sintering process are the fundamental reason for the occurrence of porosity defects, poor conductivity, and surface roughness in conductive silver paste circuits. Therefore, it is necessary to explore new sintering processes based on the thermal reaction characteristics of silver paste to suppress the generation of porosity defects and surface roughness in conductive silver paste circuits, thereby obtaining defect-free, high-density, and highly conductive silver paste circuits with good surface morphology consistency. Summary of the Invention

[0006] The purpose of this invention is to address the problems of poor conductivity and rough, inconsistent surface morphology caused by internal porosity defects in existing laser-sintered conductive silver paste circuits. This invention proposes a hot-airflow-assisted laser sintering method and apparatus to effectively suppress internal porosity defects in sintered conductive silver paste circuits and improve the conductivity and surface consistency of the conductive silver paste circuits.

[0007] The present invention specifically adopts the following technical solution: a hot airflow-assisted laser sintering method for conductive silver paste circuits, characterized in that: a hot airflow is used in front and a laser beam is used behind to simultaneously perform scanning single-pass sintering on the conductive silver paste circuit on the circuit board; wherein, the hot airflow provides pre-sintering for the conductive silver paste circuit, preferentially thermally decomposes the organic matter coated on the surface of the silver particles, and provides cohesion and inhibits the growth of pore defects for the dispersed silver particles after the organic matter volatilizes through the airflow pressure, forming a semi-solidified conductive silver paste circuit without internal pore defects, with tightly bonded silver particles, dense interior, and no protrusions on the surface; laser sintering provides further sintering for the semi-solidified conductive silver paste circuit, promoting grain boundary diffusion and neck growth of silver particles, and finally forming a conductive silver paste circuit without pore defects, highly dense, highly conductive, and with high surface morphology consistency.

[0008] In a preferred embodiment, the focused spot of the laser beam acts on the surface of the conductive silver paste circuit, and the diameter of the focused spot is smaller than the linewidth of the conductive silver paste circuit; the diameter of the jet range of the hot gas is larger than the linewidth of the conductive silver paste circuit, and the gas flow pressure of the hot gas provides a driving force for the aggregation of dispersed silver particles and a suppressing force for the growth of pores and the resulting expansion of the conductive silver paste circuit surface.

[0009] In a preferred embodiment, the conductive silver paste circuit material contains organic matter with a thermal decomposition temperature of less than 200°C. The organic matter coats the surface of the nano-silver particles, dispersing the silver particles and preventing aggregation. The sintering temperature of the hot gas flow is determined based on the decomposition temperature of the organic matter in the conductive silver paste circuit, and the sintering temperature of the hot gas flow is 200°C to 280°C. The power of the laser beam is 5W to 15W. The scanning speed of the laser beam is 0.2 to 1mm / s. The hot gas flow is located 5mm to 15mm in front of the laser beam scanning direction.

[0010] This invention also proposes a hot airflow-assisted laser sintering device for conductive silver paste circuits, comprising: a substrate, a laser, an airflow heater, an airflow heater fine-tuning platform, a CCD camera, a CCD camera fixture, and a robotic arm. The substrate, laser, airflow heater fine-tuning platform, and CCD camera are vertically fixed downwards to the end of the robotic arm. The CCD camera is vertically fixed to the left side of the substrate by the CCD camera fixture and connected to a control system via a CCD camera data cable. The laser is vertically fixed to the middle of the substrate by a laser fixture, and the laser is coaxial with the vertical rotation axis at the end of the robotic arm. The laser is connected to a laser controller via an optical fiber. The airflow heater fine-tuning platform is fixed to the right side of the substrate. The device is vertically fixed to the fine-tuning platform of the airflow heater. Compressed air is supplied to the airflow heater by an air compressor through an air pipe. The fine-tuning platform enables horizontal alignment of the airflow nozzle and the focused spot of the laser beam in the Z direction and adjusts the distance between the spot and the airflow nozzle in the X direction. The robotic arm uses a CCD camera to calibrate the trajectory of the conductive silver paste line, obtains the robotic arm's movement trajectory, and corrects the positional deviation between the CCD camera and the laser. This ensures that the focused spot of the laser carried by the robotic arm and the nozzle of the airflow heater are always aligned with the surface of the conductive silver paste line. The vertical axis rotation at the end of the robotic arm ensures that the nozzle is always in front of the laser spot's movement direction and always preferentially acts on the conductive silver paste line. Finally, the robotic arm carrying the laser and the airflow heater achieves single-scan sintering of the conductive silver paste line.

[0011] The present invention also proposes that the airflow heater fine-tuning platform includes an X-axis moving slider, a plurality of X-axis moving slider pressure plates, a Z-axis moving slider, a Z-axis moving slider clamping plate, and an airflow heater fixture. The plurality of X-axis moving slider pressure plates are fixedly mounted on the base plate to restrict the movement of the X-axis moving slider in the Y direction, thereby realizing the translation of the X-axis moving slider in the X horizontal direction. The Z-axis moving slider clamping plate is fixedly disposed on both sides of the X-axis moving slider to limit the Z-axis moving slider in the Y-axis direction, thereby realizing the translation of the Z-axis moving slider in the vertical direction. The airflow heater is vertically fixed to the outside of the Z-axis moving slider by the airflow heater fixture.

[0012] In a preferred embodiment, the inner surface of the X-axis moving slider is provided with transverse bosses at the top and bottom positions, and the transverse bosses are mounted on the X-axis moving guide rails provided on the right side of the substrate. The inner surface of the Z-axis moving slider is provided with first bosses on the left and right sides, and the first bosses are mounted on the Z-axis moving guide rails on the left and right sides of the outer surface of the X-axis moving slider.

[0013] In a preferred embodiment, an airflow nozzle is provided at the airflow outlet below the airflow heater. The airflow heater is connected to the airflow nozzle by a thread. The jet direction of the airflow nozzle forms a certain angle with the horizontal position. The airflow nozzle is located in the plane formed by the two center lines of the airflow heater and the laser. A quick-connect fitting for the air pipe is designed above the airflow heater. The quick-connect fitting for the air pipe is connected to the air pipe. The airflow heater is connected to an external air pump through the air pipe. The temperature of the airflow heater is controlled by a temperature controller.

[0014] In a preferred embodiment, the airflow heater moves laterally and vertically by adjusting the X-axis and Z-axis sliders. When the laser spot is focused on the conductive silver paste circuit surface, the airflow nozzle is adjusted to move to a position 0.5mm-1.5mm above the conductive silver paste circuit surface, and the airflow nozzle is moved to a specific distance from the laser spot in the X direction.

[0015] In a preferred embodiment, a transverse slot is provided on the substrate, and a first threaded hole is provided on the X-axis moving slider. A first fastening bolt is installed into the first threaded hole of the X-axis moving slider through the transverse slot, so that the X-axis moving slider moves to a designated position and locks. A vertical slot is provided on the X-axis moving slider, and a second threaded hole is provided on the Z-axis moving slider. A second fastening bolt is installed into the second threaded hole of the Z-axis moving slider through the vertical slot, so that the Z-axis moving slider moves to a designated position and locks.

[0016] As a preferred embodiment, a CCD camera is used to capture images of the conductive silver paste circuit in real time. A controller moves a robotic arm to capture the position of the conductive silver paste circuit in the image captured by the CCD camera and calibrate the trajectory of the conductive silver paste circuit with coordinates. This ensures that the movement trajectory of the CCD camera is consistent with the trajectory of the conductive silver paste circuit. Then, the deviation between the position coordinates of the CCD camera and the position coordinates of the laser spot is measured. Through deviation compensation at the actuator, the movement of the laser beam spot and the airflow nozzle in the sintering device is always along the trajectory of the conductive silver paste circuit, thereby achieving scanning sintering where the laser spot and the jet airflow are always aligned with the surface of the conductive silver paste circuit.

[0017] The beneficial effects achieved by this invention are as follows: First, this invention innovatively proposes a hot airflow-assisted laser sintering method and apparatus for conductive silver paste circuits. By innovatively introducing a low-temperature hot airflow for pre-sintering before laser beam sintering of the conductive silver paste circuit, the organic matter coated on the surface of the silver particles is preferentially thermally decomposed. The airflow pressure provides cohesion to the dispersed silver particles after the organic matter volatilizes and inhibits the growth of porosity defects. This promotes grain boundary diffusion and neck growth of the silver particles during laser sintering. Compared with laser sintering, this sintering process results in a higher degree of circuit densification, superior conductivity, effective suppression of circuit expansion, and a smooth circuit surface morphology. Second, the temperature of the hot airflow heated by the airflow heater in this sintering apparatus is lower than the withstand temperature of the conductive silver paste circuit substrate, avoiding ablation of the substrate by the hot airflow. Furthermore, the diameter of the laser beam acting on the surface of the conductive silver paste circuit is smaller than the circuit linewidth, thus the high-temperature laser beam will not cause damage. The substrate is subjected to ablation. Third, the sintering device is designed with X and Z axis moving platforms, which makes the relative position of the hot airflow and the laser beam adjustable. This not only makes it easy to adjust the height of the airflow nozzle according to the laser focal length and installation error, thereby achieving the same height of the laser spot (focused spot) and the airflow nozzle Z axis, but also allows for adaptive adjustment of the X-axis distance between the hot airflow and the laser beam according to the sintering effect of the conductive silver paste circuit. This effectively controls the interval between the low-temperature action of the hot airflow on the conductive silver paste circuit and the high-temperature action of the laser beam. Fourth, the sintering device is equipped with a CCD camera. By using the CCD camera to capture images of the conductive silver paste circuit, the alignment of the CCD camera and the conductive silver paste circuit can be achieved quickly and accurately by manipulating the robotic arm. By converting the coordinates of the CCD camera to the coordinates of the laser spot, the motion trajectory coordinates required for the sintering device of the conductive silver paste circuit can be obtained, thereby realizing the programming of the robotic arm's motion trajectory. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the sintering principle of conductive silver paste circuits using the hot airflow-assisted laser sintering method for conductive silver paste circuits according to the present invention.

[0019] Figure 2 This is a schematic diagram of the structure of the hot airflow-assisted laser sintering device of the present invention;

[0020] Figure 3 This is a schematic diagram showing the connection between the CCD camera fixture, the laser fixture, and the substrate.

[0021] Figure 4 A schematic diagram of the X-axis moving device structure;

[0022] Figure 5 for Figure 4 A diagram showing the view from the right.

[0023] Figure 6 This is a schematic diagram of the Z-axis moving device structure;

[0024] Figure 7 for Figure 6 A cross-sectional view;

[0025] Figure 8 A schematic diagram of the X-axis and Z-axis slider position locking devices;

[0026] Figure 9 This is a schematic diagram of the sintering system;

[0027] Figure 10 This is a schematic diagram of the cross-sectional morphology of internal defects in a conductive silver paste circuit.

[0028] The markings in the diagram represent: 1-Laser beam, 2-Laser fixture, 3-Laser, 4-CCD camera, 5-CCD camera fixture, 6-Air pipe, 7-Airflow heater, 8-X-axis moving slider pressure plate, 9-Substrate, 10-Z-axis moving slider, 11-Z-axis moving slider clamping plate, 12-Airflow heater fixture, 13-X-axis moving slider, 14-Airflow nozzle; 31-Fiber optic cable, 41-CCD camera data cable, 91-Threaded hole for CCD camera fixture, 92-Threaded hole for laser fixture, 93-X-axis moving guide rail, 94-Horizontal slot, 95-Vertical slot, 96-Second fastening bolt, 97-First fastening bolt, 101-First boss, 111-Conductive silver paste circuit placement platform, 112-Sintering device, 113-Machinery arm end, 114-Machinery arm, 133-Z-axis moving guide rail, 134-Horizontal boss. Detailed Implementation

[0029] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0030] Example 1: Combination Figure 1 This embodiment proposes a hot airflow-assisted laser sintering method for conductive silver paste circuits. The specific implementation details of the sintering method are as follows:

[0031] A single-pass scanning sintering method is used to simultaneously perform conductive silver paste lines deposited on a circuit board with a hot airflow in front and a laser beam behind. Specifically, 1) the hot airflow provides pre-sintering for the conductive silver paste lines, preferentially thermally decomposes the organic matter coated on the surface of the silver particles, and provides cohesion for the dispersed silver particles after the organic matter volatilizes through airflow pressure and inhibits the growth of pore defects, forming a semi-solidified conductive silver paste line without internal pore defects, with tightly bonded silver particles, relatively dense, and without surface bumps; 2) laser sintering provides further sintering for the semi-solidified conductive silver paste lines, promotes grain boundary diffusion and neck growth of silver particles, and finally forms a conductive silver paste line without pore defects, highly dense, highly conductive, and with a high degree of surface morphology consistency.

[0032] In this process, the laser beam is focused onto the surface of the conductive silver paste circuit, with the spot diameter being smaller than the line width to prevent ablation of the substrate. The diameter of the hot air jet is larger than the line width of the conductive silver paste circuit, providing sufficient energy for the thermal decomposition of organic matter in the conductive silver paste circuit. Furthermore, the airflow pressure provides the driving force for the aggregation of dispersed silver particles and the suppressing force for the growth of pores and the resulting expansion of the conductive silver paste circuit surface.

[0033] The hot gas sintering temperature is determined based on the decomposition temperature of organic matter in the conductive silver paste circuit, and the hot gas sintering temperature is 200℃-280℃; the laser beam power is 5W-15W; the scanning speed is 0.2-1mm / s; and the hot gas is located 5mm-15mm in front of the laser beam scanning direction.

[0034] Example 2: This example proposes a hot airflow-assisted laser sintering device for conductive silver paste circuits, including: a laser 3, an airflow heater 7, an airflow nozzle 14, an X-axis moving slider 13, a Z-axis moving slider 10, a CCD camera 4, a laser fixture 2, an airflow heater fixture 12, a CCD camera fixture 5, an X-axis moving slider pressure plate 8, a Z-axis moving slider clamping plate 11, and a substrate 9, etc.

[0035] The substrate 9 has two threaded holes 91 on its lower left side for CCD camera clamping. CCD camera clamp 5 is fixed to the left side of substrate 9 with bolts. CCD camera 4 is fixed to CCD camera clamp 5 with bolts. CCD camera 4's shooting direction is vertically downward. It is connected to the control system via CCD camera data cable 41 to transmit the conductive silver paste line image captured by the CCD camera to the control system display screen in real time. The substrate 9 has two threaded holes 92 on the right side of the CCD camera in the middle for laser clamping. Laser clamp 2 is fixed to substrate 9 with bolts. Laser 3 is fixed to laser clamp 2 with bolts. The laser 3 is installed vertically downwards, ensuring that the laser 3 is coaxial with the vertical axis of the end of the robotic arm 114. The fixed height will be determined during subsequent debugging. The laser 3 is connected to the laser controller via optical fiber, and the laser power is adjustable through the laser controller. Parallel X-axis moving guide rails 93 are designed on the upper and lower right sides of the substrate 9. The substrate 9 is designed with countersunk holes, and the substrate 9 is installed on the end of the robotic arm 113 by bolts. The multi-degree-of-freedom robotic arm carries the sintering device to perform the sintering operation. Through the programming of the robotic arm, the sintering device can scan the surface of the conductive silver paste line at a fixed speed according to the conductive silver paste line trajectory, i.e., sintering.

[0036] The inner surface of the X-axis sliding slider 13 has transverse bosses 134 at the top and bottom positions. These bosses 134 are in contact with the surface of the X-axis moving guide rail 93, and the X-axis sliding slider 13 is constrained on the guide rail by the X-axis sliding slider clamp 8 mounted on the base plate 9. Furthermore, the outer side of the parallel X-axis moving guide rail 93 has limit bosses to restrict the movement of the X-axis sliding slider 13 in the Z direction, ensuring that the X-axis sliding slider 13 moves only in a transverse linear direction. Figure 4 and Figure 5 .

[0037] The outer surface of the X-axis slider 13 has parallel Z-axis guide rails 133 on both sides. The inner surface of the Z-axis slider 10 has vertical first protrusions 101 on both sides for mounting and fitting onto the Z-axis guide rails 133. The Z-axis slider 10 is fixed to the inverted "L"-shaped Z-axis slider clamps 11 on both sides of the X-axis slider 13 by bolts, limiting the Z-axis slider 10 to linear vertical movement on the Z-axis guide rails 133. This allows the Z-axis slider 10 to move only along a vertical line. Figure 6 and Figure 7 .

[0038] The substrate 9 has a horizontal slot 94, and the X-axis slider 13 has a threaded hole. A first fastening bolt 97 passes through the horizontal slot 94 and is installed into the threaded hole, allowing the X-axis slider 13 to move to a designated position and lock. The X-axis slider 13 has a vertical slot 95, and the Z-axis slider 10 has a threaded hole. A second fastening bolt 96 passes through the vertical slot 95 and is installed into the threaded hole, allowing the Z-axis slider 10 to move to a designated position and lock. (See...) Figure 8 .

[0039] The airflow heater 7 is vertically fixed to the Z-axis moving slider 10 by bolts using the airflow heater fixture 12. The upper part is the air inlet and the lower part is the air outlet. It is ensured that the plane formed by the two center lines of the laser 3 is parallel to the surface of the X-axis moving guide rail 93.

[0040] The airflow heater 7 has a threaded outlet for connecting to the airflow nozzle 14. The nozzle 14 has an inner diameter of 3mm and is positioned at a 45° angle relative to the horizontal, aligning with the laser beam. A quick-connect fitting for the air pipe is located above the airflow heater 7 for connecting to the air pipe 6, which in turn connects to the air pump, which provides compressed air. The airflow heater 7 is precisely temperature-controlled by a temperature controller, allowing the airflow temperature to be controlled between 50℃ and 350℃.

[0041] The airflow heater 7 can move horizontally and vertically based on the X-axis slider 13 and the Z-axis slider 10. The vertical movement range of the airflow nozzle relative to the horizontal plane where the focused laser spot is located is ±10mm. When the airflow nozzle and the focused laser spot are horizontally aligned in the vertical direction, the airflow nozzle can move 0-20mm to the right of the spot. This allows for adjustment of the horizontal alignment of the airflow nozzle 14 and the laser spot in the vertical direction and the specific distance in the X direction, thereby meeting the specific conductive silver paste circuit sintering process.

[0042] With the help of CCD camera 4, the conductive silver paste circuit can be captured in real time. By controlling the movement of robotic arm 114, the position of the conductive silver paste circuit is captured in the CCD image and the coordinate of the conductive silver paste circuit trajectory is calibrated so that the CCD camera movement trajectory is consistent with the conductive silver paste circuit trajectory. Then, the deviation between the CCD camera position coordinates and the laser spot position coordinates is measured. Through deviation compensation, the movement of the laser spot and the airflow nozzle in the sintering device is always along the conductive silver paste circuit trajectory.

[0043] Example 3: Based on Examples 1 and 2, the workflow of this example consists of the following two parts.

[0044] 1. Sintering trajectory programming: The controller controls the robotic arm 114 to move the sintering device 112 and align the laser spot focus with the conductive silver paste circuit surface. At this time, the Z-axis slider 10 is moved to adjust the airflow nozzle to a position 0.5mm-1.5mm above the conductive silver paste circuit surface. In the X direction, the X-axis slider 13 is moved to a specific distance from the laser spot. Then, the second fastening bolt 96 and the first fastening bolt 97 are tightened to lock the position of the airflow heater 7. Afterwards, the control... The device opens the CCD camera 4 and manipulates the robotic arm 114 via the controller to align the crosshair in the CCD camera image with the conductive silver paste line. This allows for the calibration of the starting, inflection point, and coordinates of the robotic arm 114's movement. The deviation between the CCD camera 4 and the laser spot coordinates, as well as the rotation angle of the sintering device, are measured in the sintering apparatus 112. The deviation in the robotic arm's motion coordinates is then corrected to ensure that the trajectory of the laser spot and the center of the hot airflow coincides with the trajectory of the conductive silver paste line. This ensures that the scanning motion of the laser spot and the hot airflow in the sintering apparatus always follows the conductive silver paste line trajectory. Figure 9 As shown.

[0045] 2. Sintering Process: First, the laser power is set to a specific power via the laser controller. Then, the gas pump throttle valve is opened and the gas flow rate is set. The gas flow heater temperature controller is turned on and set to a specific temperature. After the real-time temperature of the sensor reaches the set temperature and stabilizes, the programmed robotic arm movement button is activated. Driven by the robotic arm 114, the sintering device 112 begins sintering the conductive silver paste lines placed on the conductive silver paste line placement platform 111 from the starting end. The sintering scanning speed is set by the robotic arm controller. The laser power, gas flow temperature, and scanning speed are adjustable according to the sintering process parameters.

[0046] Laser sintering and hot airflow assisted laser sintering were used to sinter conductive silver paste circuits at the same 8W laser power and 0.5mm / s scanning speed. The internal morphology of the conductive silver paste circuits after sintering is as follows: Figure 10 As shown, Figure 10 Comparative Example a in the table shows the laser sintering process, and Comparative Example b shows the hot airflow assisted laser sintering process. The cross-sectional area and resistivity are shown in Table 1.

[0047] Table 1 Cross-sectional area and resistivity of conductive silver paste circuits

[0048]

[0049] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0050] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1The computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to operate in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The functions specified in one or more boxes. These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable apparatus for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A hot gas flow-assisted laser sintering method for conductive silver paste circuits, characterized in that: A single-pass scanning sintering method is adopted to simultaneously perform conductive silver paste lines deposited on a circuit substrate using a hot airflow in front and a laser beam (1) behind. The hot airflow provides pre-sintering for the conductive silver paste lines, thermally decomposes the organic matter coating the surface of the silver particles, and provides cohesion and inhibits the growth of porosity defects in the dispersed silver particles after the organic matter volatilizes through airflow pressure, forming a semi-solidified conductive silver paste line without internal porosity defects, with tightly bonded silver particles and no surface protrusions. Laser sintering provides further sintering for the semi-solidified conductive silver paste line, promoting grain boundary diffusion and neck growth of the silver particles, ultimately forming a conductive silver paste line without porosity defects and with high surface morphology consistency. The method also includes a hot airflow-assisted laser sintering device, including: a substrate (9), a laser (3), a gas flow heater (7), a gas flow heater fine-tuning platform, and a CCD camera (…). 4) CCD camera fixture (5) and robotic arm (114), wherein the substrate (9), laser (3), airflow heater fine-tuning platform and CCD camera (4) are respectively fixed vertically downward at the end of the robotic arm (114). The CCD camera (4) is vertically fixed on the left side of the substrate (9) by the CCD camera fixture (5) and connected to the control system through the CCD camera data cable (41). The laser (3) is vertically fixed in the middle of the substrate (9) by the laser fixture (2). The laser (3) is coaxial with the vertical rotation axis at the end of the robotic arm (114). The laser (3) is connected to the laser controller through the optical fiber (31). The airflow heater fine-tuning platform is fixed on the right side of the substrate (9). The airflow heater (7) is vertically fixed downward on the airflow heater fine-tuning platform. The airflow heater fine-tuning platform includes an X-axis moving slider (13), several X-axis moving slider pressure plates (8), a Z-axis moving slider (10), a Z-axis moving slider clamping plate (11), and an airflow heater clamping fixture (12). Several X-axis moving slider pressure plates (8) are fixedly installed on the base plate (9) to restrict the movement of the X-axis moving slider (13) in the Y direction, thereby realizing the translation of the X-axis moving slider (13) in the X horizontal direction. The Z-axis moving slider clamping plate (11) is fixedly set on both sides of the X-axis moving slider (13) to limit the Z-axis moving slider (10) in the Y direction, thereby realizing the translation of the Z-axis moving slider (10) in the vertical direction. The airflow heater (7) is vertically fixed to the outside of the Z-axis moving slider (10) by the airflow heater clamping fixture (12).

2. The hot gas flow-assisted laser sintering method for conductive silver paste circuits according to claim 1, characterized in that, The focused spot of the laser beam (1) acts on the surface of the conductive silver paste circuit, and the diameter of the focused spot is smaller than the linewidth of the conductive silver paste circuit; the diameter of the jet range of the hot air is larger than the linewidth of the conductive silver paste circuit, and the air pressure of the hot air provides a driving force for the aggregation of dispersed silver particles and a suppressing force for the growth of pores and the resulting expansion of the conductive silver paste circuit.

3. The hot gas flow-assisted laser sintering method for conductive silver paste circuits according to claim 1, characterized in that, The conductive silver paste circuit material contains organic matter, the thermal decomposition temperature of which is less than 200°C. The organic matter coats the surface of the nano-silver particles to disperse the silver particles and prevent aggregation. The sintering temperature of the hot airflow is determined based on the decomposition temperature of the organic matter in the conductive silver paste circuit. The sintering temperature of the hot airflow is 200°C to 280°C. The power of the laser beam (1) is 5W to 15W. The scanning speed of the laser beam (1) is 0.2 to 1mm / s. The hot airflow is located 5mm to 15mm in front of the scanning direction of the laser beam (1).

4. The hot gas flow-assisted laser sintering method for conductive silver paste circuits according to claim 1, characterized in that, The inner surface of the X-axis sliding slider (13) is provided with transverse bosses (134) at the upper and lower positions. The transverse bosses (134) are mounted on the X-axis moving guide rail (93) provided on the right side of the substrate (9). The inner surface of the Z-axis sliding slider (10) is provided with first bosses (101) on the left and right sides. The first bosses (101) are mounted on the Z-axis moving guide rails (133) on the left and right sides of the outer surface of the X-axis sliding slider (13).

5. The hot gas flow-assisted laser sintering method for conductive silver paste circuits according to claim 1, characterized in that, The airflow heater (7) is provided with an airflow nozzle (14) at the airflow outlet below it. The airflow heater (7) is connected to the airflow nozzle (14) by a thread. The spray direction of the airflow nozzle (14) is at a 45° angle to the horizontal position. The airflow nozzle (14) is located in the plane formed by the two center lines of the airflow heater (7) and the laser (3). A quick-connect fitting for the air pipe is designed above the airflow heater (7). The quick-connect fitting for the air pipe is connected to the air pipe (6). The airflow heater (7) is connected to an external air pump through the air pipe (6). The temperature of the airflow heater (7) is controlled by a temperature controller.

6. The hot gas flow-assisted laser sintering method for conductive silver paste circuits according to claim 1, characterized in that, The airflow heater (7) moves horizontally and vertically by adjusting the X-axis slider (13) and the Z-axis slider (10). When the laser spot is focused on the conductive silver paste line surface, the airflow nozzle (14) is adjusted to move to 0.5mm-1.5mm above the conductive silver paste line surface. In the X direction, the airflow nozzle (14) is moved to a distance of ±10mm from the laser spot.

7. The hot gas flow-assisted laser sintering method for conductive silver paste circuits according to claim 1, characterized in that, The substrate (9) is provided with a horizontal slot (94), and the X-axis moving slider (13) is provided with a first threaded hole. The first fastening bolt (97) passes through the horizontal slot (94) and is installed into the first threaded hole of the X-axis moving slider (13) to realize the X-axis moving slider (13) moving to a designated position and locking. The X-axis moving slider (13) is provided with a vertical slot (95), and the Z-axis moving slider (10) is provided with a second threaded hole. The second fastening bolt (96) passes through the vertical slot (95) and is installed into the second threaded hole of the Z-axis moving slider (10) to realize the Z-axis moving slider (10) moving to a designated position and locking.

8. A hot-airflow-assisted laser sintering method for conductive silver paste circuits according to claim 5, characterized in that, Using a CCD camera (4), the conductive silver paste line is captured in real time. The robotic arm (114) is moved by the controller. The position of the conductive silver paste line is captured in the conductive silver paste line image captured by the CCD camera (4), and the coordinate of the conductive silver paste line trajectory is calibrated so that the movement trajectory of the CCD camera (4) is consistent with the trajectory of the conductive silver paste line. Then, the deviation between the position coordinates of the CCD camera (4) and the position coordinates of the laser spot is measured. Through coordinate deviation compensation, the movement of the laser beam (1) laser spot and the airflow nozzle (14) in the sintering device is always along the trajectory of the conductive silver paste line, thereby realizing that the laser spot and the jet airflow are always aligned with the surface of the conductive silver paste line for scanning sintering.

Images