Method for producing a powder of a metal material for flexible circuit boards by gas atomization

Abstract

The present application relates to the field of metal processing, and provides a method for preparing flexible circuit board metal material powder by gas atomization, wherein a metal raw material for preparing a flexible circuit board is smelted to obtain a metal liquid, the metal liquid is introduced into an atomization device by using a pressure device for atomization, the metal liquid is broken by conveying high-pressure gas during the atomization process to form metal liquid droplets, the metal liquid droplets are cooled and collected to obtain metal powder. The method can effectively prepare flexible circuit board special metal powder with high sphericity, narrow particle size distribution and low oxygen content by stable control of the metal liquid, significantly improve the flowability and spreading uniformity of the powder, and is suitable for precision printing or additive manufacturing process, avoids the problems of large particle size deviation and high defect rate caused by traditional atomization method, and the prepared metal powder has excellent conductivity and flexibility after sintering, and is suitable for the manufacturing of flexible electronic devices in high-frequency and high-flexure scenarios.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of metal processing, in particular to a method for preparing flexible circuit board metal material powder by gas atomization. BACKGROUND

[0002] Flexible circuit board is widely used in various high-density integrated fields. With the development of light and thin electronic products, the manufacturing process of FPC has increasingly strict requirements on line width / line spacing, usually reaching micron level or even higher precision. Electronic paste, as the core material for forming conductive circuit, directly determines the printing quality and conductive performance of FPC.

[0003] Electronic paste is mainly composed of three parts: metal functional phase, bonding phase and organic carrier. The metal functional phase is usually the powder of conductive metals such as silver and copper. The physical properties such as particle size distribution, morphology and tap density of the metal functional phase have a decisive influence on the printing adaptability, sintering behavior and electrical performance of the final circuit of the paste. High fine powder rate is beneficial to realize high densification sintering at low temperature, thereby improving the resolution and conductivity of the circuit. High sphericity powder can improve the rheological properties of the paste, ensure the stability of the printing process and the consistency of sintering shrinkage, and avoid defects such as circuit deformation and warping.

[0004] At present, gas atomization technology is one of the main methods for preparing metal powder for electronic paste. Specifically, high-pressure gas is used to break the molten metal into small droplets, which are then cooled and shaped into spherical powder under the action of surface tension. Traditional gas atomization process often aims to achieve high yield, but it is difficult to simultaneously optimize the fine powder rate and sphericity. For example, increasing the gas-liquid ratio or atomization pressure to improve fine powder yield leads to irregular powder morphology and increased satellite powder. Excessive pursuit of sphericity will reduce the output efficiency of ultra-fine powder. In addition, the stability of the metal liquid flow during atomization has a significant impact on powder quality. If the liquid flow swings, breaks or drips, it will result in wide particle size distribution, inconsistent morphology, and a large amount of waste powder.

[0005] Therefore, the existing gas atomization technology still needs to be further improved to accurately control the behavior of the metal liquid flow, thereby obtaining metal powder with high sphericity while ensuring high fine powder rate, and meeting the manufacturing requirements of high-end FPC. SUMMARY

[0006] The purpose of the present application is to provide a method for preparing flexible circuit board metal material powder by gas atomization, to solve one or more technical problems existing in the prior art, and to provide at least one beneficial option or create conditions.

[0007] The application provides a method for preparing flexible circuit board metal material powder by gas atomization. The method comprises the following steps: melting metal raw materials for preparing a flexible circuit board to obtain a metal liquid; using a pressure device to pass the metal liquid into an atomization device for atomization; in the atomization process, the metal liquid is broken by conveying high-pressure gas to form metal liquid droplets; the metal liquid droplets are cooled and collected to obtain metal powder. The method can effectively prepare flexible circuit board special metal powder with high sphericity, narrow particle size distribution and low oxygen content, significantly improve the flowability and spreading uniformity of the powder, and is suitable for precision printing or additive manufacturing process. The method avoids the problems of large particle size deviation and high defect rate caused by traditional atomization method. The prepared metal powder has excellent conductivity and flexibility after sintering, and is suitable for the manufacturing of flexible electronic devices in high-frequency and high-flexure scenarios.

[0008] In order to achieve the above-mentioned purpose, according to an aspect of the application, a method for preparing flexible circuit board metal material powder by gas atomization is provided, the method comprising the following steps:

[0009] Melting metal raw materials for preparing a flexible circuit board to obtain a metal liquid;

[0010] Using a pressure device to pass the metal liquid into an atomization device for atomization;

[0011] In the atomization process, the metal liquid is broken by conveying high-pressure gas to form metal liquid droplets;

[0012] Cooling and collecting the metal liquid droplets to obtain metal powder.

[0013] Further, the method for melting the metal raw materials to obtain the metal liquid is as follows: the metal raw materials are placed in a melting furnace for melting, heat is generated in the metal by electromagnetic induction to melt the metal raw materials, and the metal liquid is obtained; in the melting process, an inert gas is provided to maintain a low-oxygen environment (oxygen content is less than 20 ppm, and some active metals which are prone to oxidation can be controlled to be less than 1-10 ppm); a crucible is arranged in the melting furnace to hold the metal liquid, and the crucible is provided with a flow guide pipe at the bottom.

[0014] Further, the method for using the pressure device to pass the metal liquid into the atomization device is as follows:

[0015] A pressure device is installed at the top of the crucible, and the pressure device is used to continuously apply pressure to the metal liquid, so that the metal liquid flows out of the crucible and enters an atomization cabin in the atomization device.

[0016] Preferably, the pressure device is a back pressure regulator or a hydraulic servo valve.

[0017] Further, in the process of passing the metal liquid into the atomization device, the method further comprises metal liquid stability control.

[0018] Further, the method for stabilizing the metal liquid specifically comprises: installing a camera outside the atomization cabin in the atomization device, aiming the lens of the camera at the lower part of the flow guide pipe of the crucible through the observation window, and the camera is a CCD industrial camera equipped with a telecentric lens;

[0019] The camera continuously captures images of the metal liquid flowing out of the crucible and transmits the images to the terminal, the shooting interval of the camera is set by the user, and is usually set to [100, 1000] frame rate, and the received images are detected in real time in the terminal, and if an abnormal liquid flow image is detected, the liquid flow pressure is adjusted to keep the metal liquid stable;

[0020] The beneficial effect of this step is that the stability of the metal liquid flow directly determines the particle size distribution and morphology consistency of the atomized powder, and if the liquid flow fluctuates or breaks during atomization, irregular powder or satellite particles are easily produced, reducing product quality. The method of this step can dynamically maintain the continuity and stability of the metal liquid flow by real-time capture of the morphological characteristics of the metal liquid flow below the flow guide pipe through a high-resolution CCD industrial camera, combined with image processing technology and feedback control, which can make the metal liquid droplets form uniformly and significantly reduce the particle size deviation and defect rate of the powder.

[0021] Further, the received metal liquid flow images are detected in real time, specifically including detecting whether the liquid flow diameter of the metal liquid deviates from the preset interval, whether the liquid flow of the metal liquid swings, whether the liquid flow of the metal liquid breaks, drips, or disappears.

[0022] Further, if an abnormal liquid flow image is detected, the liquid flow pressure is adjusted, including:

[0023] If it is detected that the liquid flow diameter of the metal liquid deviates from the preset interval, the back pressure of the crucible is changed by adjusting the pressure device to make the liquid flow of the metal liquid return to the preset interval;

[0024] If it is detected that the liquid flow of the metal liquid swings, the liquid flow of the metal liquid is stabilized without swinging by adjusting the pressure of the high-pressure gas; the size of the high-pressure gas pressure is specifically adjusted by the control system of the atomization device;

[0025] If it is detected that the liquid flow of the metal liquid breaks, drips, or disappears, a warning signal is sent to the monitoring room, the crucible is quickly lifted to make the flow guide pipe leave the atomization cabin, preventing the metal liquid from solidifying at the nozzle and causing serious equipment accidents, and at the same time, the atomization process is stopped to avoid waste powder.

[0026] Preferably, the image processing algorithm used to detect whether the liquid flow diameter of the metal liquid deviates from the preset interval is an edge detection algorithm, the image processing algorithm used to detect whether the liquid flow of the metal liquid swings is an optical flow estimation difference method, and the image processing algorithm used to detect whether the liquid flow of the metal liquid breaks, drips, or disappears is a connected domain analysis algorithm.

[0027] Since early abnormality recognition of the metal liquid flow state can better improve the quality of powder production, preferably, the method for detecting the liquid flow abnormal image can also be:

[0028] Arrange the N images newly received by the terminal in ascending order of receiving time (i.e. the latest received image is arranged at the end) and form an image sequence SCN, denote SCN(i) as the i-th of the N images in the image sequence SCN (SCN(N) means the latest received image), i is the serial number, i=1, 2, …, N, and SV i denotes the sum of all pixel values in the image SCN(i), and SV1, SV2, …, SV N The average value of these N values is denoted as ASV; N is set to a value in the interval [50, 200].

[0029] Denote fc(i) as the liquid flow configuration of the image SCN(i), and the calculation method of fc(i) is: denote Sp(i) as the number of pixels contained in SCN(i), and the value obtained by dividing ASV by Sp(i) is denoted as D(i), and the value obtained by dividing the sum of all pixel values greater than D(i) in the image SCN(i) by the sum of all pixel values less than D(i) in the image SCN(i) is taken as the liquid flow configuration fc(i) of SCN(i);

[0030] For the N liquid flow configurations fc(1), fc(2), …, fc(N) corresponding to the N images, denote the value obtained by subtracting fc(1) from fc(N) as f1; if the value of f1 is positive, the through-flow interval is defined as [0, f1]; if the value of f1 is negative, the through-flow interval is defined as [f1, 0];

[0031] According to the N liquid flow configurations, calculate the cross-flow degree, if the value of the cross-flow degree is located outside the through-flow interval, mark SCN(N) as a liquid flow abnormal image, at the same time, stabilize the metal liquid by adjusting the pressure of the high-pressure gas, and send a warning signal to the monitoring room.

[0032] Further, the method for calculating the cross-flow degree according to the N liquid flow configurations is:

[0033] S1, set a variable j, the initial value of j is set to 2, the traversal range of j is [2, N-1], and denote fp j-1 = fp1 = fc(2) - fc(1), initialize the variable C0 = fp j-1 , and go to S2;

[0034] S2, denote the value obtained by subtracting fc(j) from fc(j+1) as fp j , if the value of fp j × fp j-1 is greater than 0, update the value of C0 as fpj +C0; if fp j x fp j-1 if the value of C0 is less than 0, the value of C0 is updated to fp j x (1 + |C0| ÷ j) + C0, and go to S3;

[0035] S3, if the value of variable j is less than N-1, the value of j is increased by 1 and go to S2; if the value of variable j is equal to or greater than N-1, go to S4;

[0036] S4, record the value of C0 as the abnormal flow degree.

[0037] The beneficial effect of this step is that: although the traditional edge detection and optical flow estimation algorithm can identify specific types of abnormalities such as diameter deviation or oscillation, it is difficult to capture the early abnormal characteristics of the liquid flow. The slight high-frequency tremor of the liquid flow edge and the change of the overall brightness of the liquid flow in the flowing state are often the signal that the balance between the internal pressure of the liquid flow and the external atomization gas dynamic field is broken. At the same time, due to the inherent physical delay and inertia of the gas atomization process system, there is a response window that needs a fixed time from the perception of the abnormality to the pressure regulation. If the liquid flow has already appeared obvious oscillation or flow break, the intervention of the control system of the atomization device has already lagged a lot. Therefore, capturing and regulating the early abnormal characteristics of the liquid flow is the key to ensure high fine powder rate and obtain high sphericity of the metal powder. The method of this step determines the abnormality by analyzing the dynamic change trend of the liquid flow degree in the continuous image sequence, and amplifies the change mode of the liquid flow (is it continuous or oscillating) in an accumulative differential C0 and directional weighting (statement S2) manner. If the value of the liquid flow degree representing the liquid flow state shows a large amplitude of continuous decline or rise, the abnormal flow degree will exceed the through-flow interval, representing that it has appeared a trend of instability and needs early intervention. On the contrary, if the liquid flow degree shows a fluctuation mode (as long as the overall fluctuation amplitude is not too large, too large will cause the difference between the abnormal flow degree and fc(1) and fc(N) to be large and also trigger an early warning), the abnormal flow degree will not exceed the through-flow interval, and there is no need for pressure adjustment intervention at this time. Therefore, the early warning of the liquid flow stability through the abnormal flow degree can obtain more response time when the liquid flow diameter has not yet deviated obviously or has just appeared slight oscillation, which can effectively avoid the generation of waste powder.

[0038] Further, the method for breaking the metal liquid by delivering high-pressure gas to form metal liquid droplets in the atomization process is specifically:

[0039] delivering high-pressure gas and accelerating the high-pressure gas to form high-speed gas flow through the annular gap nozzle in the atomization device, and the high-speed gas flow breaks the metal liquid into metal liquid droplets; wherein the high-pressure gas refers to high-pressure liquefied argon or high-pressure liquefied nitrogen.

[0040] Further, the method for cooling the metal liquid droplets and collecting to obtain the metal powder specifically comprises: cooling and solidifying the metal liquid droplets in the flying process to obtain spherical metal powder, and collecting, screening and vacuum packaging the spherical metal powder through the collecting device located at the bottom of the atomization tower in the atomization device.

[0041] The method can effectively prepare the special metal powder for the flexible circuit board with high sphericity, narrow particle size distribution and low oxygen content, significantly improve the flowability and spreading uniformity of the powder, and is suitable for precise printing or additive manufacturing process, avoids the problems of large particle size deviation and high defect rate caused by the traditional atomization method, and the prepared metal powder has excellent conductivity and flexibility after sintering, and is suitable for the manufacturing of flexible electronic devices in high-frequency and high-flexure scenarios. BRIEF DESCRIPTION OF DRAWINGS

[0042] Figure 1 The flowchart of the method for preparing the metal material powder for the flexible circuit board by gas atomization is shown. DETAILED DESCRIPTION

[0043] The concept, specific structure and technical effects of the present application will be described clearly and completely in combination with the embodiments and the drawings to fully understand the purpose, scheme and effects of the present application. It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

[0044] In the description of the present application, one or more is meant to be one or more, more than two, greater than, less than, more than, etc. are understood to not include the number, above, below, etc. are understood to include the number. If it is described as first, second, it is only used to distinguish the technical features for the purpose, and cannot be understood as indicating or implying the relative importance or implicitly indicating the number of indicated technical features or implicitly indicating the sequence of indicated technical features.

[0045] As Figure 1 The flowchart of the method for preparing the metal material powder for the flexible circuit board by gas atomization according to the present application is shown, and the method for preparing the metal material powder for the flexible circuit board by gas atomization according to the embodiment of the present application will be described below in combination with Figure 1 The flowchart of the method for preparing the metal material powder for the flexible circuit board by gas atomization according to the present application is shown, and the method for preparing the metal material powder for the flexible circuit board by gas atomization according to the embodiment of the present application will be described below in combination with

[0046] The present application provides a method for preparing a metal material powder for a flexible circuit board by gas atomization, which comprises the following steps:

[0047] Melting the metal raw material for preparing the flexible circuit board to obtain a metal liquid;

[0048] Using a pressure device to pass the metal liquid into an atomization device for atomization;

[0049] The metal liquid is broken by conveying high-pressure gas in the atomization process to form metal liquid drops;

[0050] The metal liquid drops are cooled and collected to obtain metal powder.

[0051] Further, the method for obtaining the metal liquid by smelting the metal raw material specifically comprises: placing the metal raw material into a smelting furnace for smelting, generating heat in the metal by electromagnetic induction to melt the metal raw material and obtain the metal liquid; wherein, a low-oxygen environment is maintained by providing inert gas during the smelting process; a crucible is arranged in the smelting furnace for containing the metal liquid, and the crucible is provided with a flow guide pipe at the bottom.

[0052] Further, the method for using the pressure device to pass the metal liquid into the atomization device specifically comprises:

[0053] A pressure device is arranged at the top of the crucible, which is used to push the metal liquid out of the crucible and accurately control the flow rate of the metal liquid. The pressure device is used to continuously apply pressure to the metal liquid, so that the metal liquid slowly flows out of the crucible in the form of a thin stream and enters the atomization cabin in the atomization device.

[0054] Specifically, the pressure device is a back pressure regulator.

[0055] Further, the method for passing the metal liquid into the atomization device further comprises metal liquid stability control.

[0056] Further, the method for metal liquid stability control specifically comprises: a camera is arranged outside the atomization cabin in the atomization device, the lens of the camera is aimed at the lower part of the flow guide pipe of the crucible through an observation window, a backlight or a sidelight (a high-brightness LED light source) is provided for the camera so that the camera can clearly capture the image of the liquid stream of the metal liquid, and the camera is a CCD industrial camera equipped with a telecentric lens.

[0057] The camera is used to continuously capture the image of the metal liquid flowing out of the crucible and transmit the image to a terminal. The received image is detected in real time in the terminal. If an abnormal liquid stream image is detected, the liquid stream pressure is adjusted to keep the metal liquid stable.

[0058] The metal liquid stability means that the diameter and center line position of the metal liquid do not deviate from the preset interval, and the liquid stream of the metal liquid is straight, continuous and without swing.

[0059] Specifically, the received image of the liquid stream of the metal liquid is detected in real time. Before detection, the image of the liquid stream of the metal liquid is saved after foreground extraction (the purpose is to extract the liquid stream target and delete the irrelevant background part for detection).

[0060] Further, the received image of the liquid stream of the metal liquid is detected in real time, which specifically comprises detecting whether the diameter of the liquid stream of the metal liquid deviates from the preset interval, whether the liquid stream of the metal liquid swings, whether the liquid stream of the metal liquid breaks, leaks or disappears.

[0061] Further, if the liquid flow abnormal image is detected, the liquid flow pressure is adjusted, including:

[0062] If the liquid flow diameter of the metal liquid deviates from the preset interval, the back pressure of the crucible is changed by adjusting the pressure device to make the liquid flow of the metal liquid return to the preset interval. Specifically, when the liquid flow diameter of the metal liquid exceeds the upper limit of the preset interval, the pressure supplied by the pressure device is reduced to slow down the flow rate of the metal liquid, and the liquid flow becomes thin; when the liquid flow diameter of the metal liquid is lower than the lower limit of the preset interval, the pressure supplied by the pressure device is increased to accelerate the flow rate of the metal liquid, and the liquid flow becomes thick.

[0063] If the liquid flow of the metal liquid is detected to swing, the pressure of the high-pressure gas is adjusted to make the liquid flow of the metal liquid stable and non-swinging; the size of the high-pressure gas pressure is specifically adjusted by the control system of the atomization device;

[0064] If the liquid flow of the metal liquid is monitored to break, drip or disappear, a warning signal is sent to the monitoring room, and the crucible is quickly lifted to make the flow guide pipe leave the atomization cabin, so as to prevent the metal liquid from solidifying at the nozzle to cause serious equipment accidents, and at the same time, the atomization process is stopped to avoid waste powder in production.

[0065] Since early abnormal identification of the metal liquid flow state can better improve the quality of powder production, preferably, the method for detecting the liquid flow abnormal image can also be:

[0066] The N images newly received by the terminal are arranged in ascending order of receiving time (i.e., the newly received image is arranged at the end) and composed into an image sequence SCN, SCN(i) is recorded as the i-th of the N images in the image sequence SCN (SCN(N) means the newly received image), i is a serial number, i=1,2,…,N, and SV i represents the sum of all pixel values in the image SCN(i), and SV1,SV2,…,SV N The average value of the N values is recorded as ASV; N is set to 100;

[0067] fc(i) is recorded as the liquid flow configuration of the image SCN(i), and the calculation method of fc(i) is: Sp(i) represents the number of pixels contained in SCN(i), and the value obtained by dividing ASV by Sp(i) is recorded as D(i); the value obtained by dividing the sum of all pixel values greater than D(i) in the image SCN(i) by the sum of all pixel values less than D(i) in the image SCN(i) is taken as the liquid flow configuration fc(i) of SCN(i);

[0068] For N liquid flow configurations fc(1), fc(2), …, fc(N) corresponding to N image pairs, the value obtained by subtracting fc(1) from fc(N) is denoted as f1; if the value of f1 is positive, the through-flow interval is defined as [0, f1]; if the value of f1 is negative, the through-flow interval is defined as [f1, 0];

[0069] According to the N liquid flow configurations, the cross-flow degree is calculated, and if the value of the cross-flow degree is located outside the through-flow interval, the SCN(N) is marked as a liquid flow abnormal image, the metal liquid is stabilized by adjusting the pressure of the high-pressure gas, and a warning signal is sent to the monitoring room.

[0070] Further, the method for calculating the cross-flow degree according to the N liquid flow configurations is:

[0071] S1, a variable j is set, the initial value of j is set to 2, the traversal range of j is [2, N-1], fc(j) represents the jth value of the N liquid flow configurations, and fp j-1 = fp1= fc(2)-fc(1), the variable C0 is initialized as fp j-1 , and S2 is turned to;

[0072] S2, the value obtained by subtracting fc(j) from fc(j+1) is denoted as fp j , if fp j × fp j-1 is greater than 0, the value of C0 is updated as fp j +C0; if fp j × fp j-1 is less than 0, the value of C0 is updated as fp j ×(1+|C0|÷j)+C0, and S3 is turned to;

[0073] S3, if the value of the variable j is less than N-1, the value of j is increased by 1 and S2 is turned to; if the value of the variable j is equal to or greater than N-1, S4 is turned to;

[0074] S4, the value of C0 is denoted as the cross-flow degree.

[0075] Further, the method for breaking the metal liquid into metal liquid droplets by delivering high-pressure gas during atomization is:

[0076] The high-pressure gas is introduced, and the high-pressure gas is accelerated by the annular slit nozzle in the atomization device to form a high-speed gas flow, and the high-speed gas flow breaks the metal liquid into a large number of micron-sized metal liquid droplets; wherein the high-pressure gas refers to high-pressure liquefied argon gas or high-pressure liquefied nitrogen gas.

[0077] Further, the method for cooling the metal liquid droplets and collecting to obtain the metal powder is specifically: cooling and solidifying the metal liquid droplets in the flying process to obtain spherical metal powder, and collecting, screening and vacuum packaging the spherical metal powder by the collecting device located at the bottom of the atomization tower in the atomization device.

[0078] The application provides a method for preparing flexible circuit board metal material powder by gas atomization, which comprises the following steps: melting metal raw materials for preparing flexible circuit boards to obtain metal liquid, using a pressure device to pass the metal liquid into an atomization device for atomization, breaking the metal liquid by conveying high-pressure gas during the atomization process to form metal liquid droplets, cooling the metal liquid droplets and collecting to obtain metal powder. The method can effectively prepare flexible circuit board special metal powder with high sphericity, narrow particle size distribution and low oxygen content by stable control of the metal liquid, significantly improve the flowability and spreading uniformity of the powder, and is suitable for precise printing or additive manufacturing process, avoids the problems of large particle size deviation and high defect rate caused by traditional atomization method, and the prepared metal powder has excellent conductivity and flexibility after sintering, and is suitable for the manufacturing of flexible electronic devices in high-frequency and high-flexure scenarios. Although the description of the application has been quite detailed and several embodiments have been described in particular, it is not intended to be limited to any of these details or embodiments or any special embodiment, so as to effectively cover the intended scope of the application. In addition, the application is described above in the embodiments that the inventors can foresee, and the purpose is to provide a useful description, and non-essential modifications to the application that have not yet been foreseen can still represent equivalent modifications to the application.

Claims

1. A method of gas atomizing a flexible circuit board metal material powder, characterized by, The method comprises the following steps: Melting the metal raw material for preparing the flexible circuit board to obtain a metal liquid; Using a pressure device to pass the metal liquid into an atomization device for atomization; In the atomization process, the metal liquid is broken by conveying high-pressure gas to form metal liquid droplets; Cooling the metal liquid droplets and collecting to obtain metal powder; Wherein, in the process of passing the metal liquid into the atomization device, it also comprises metal liquid stability control; The method of metal liquid stability control is specifically: installing a camera outside the atomization cabin in the atomization device, aiming the lens of the camera at the lower part of the flow guide pipe of the crucible through the observation window, and the camera is a CCD industrial camera equipped with a telecentric lens; continuously shooting the image of the metal liquid flowing out of the crucible using the camera and transmitting the image to the terminal, and detecting the received image in real time in the terminal, if the abnormal liquid flow image is detected, adjust the liquid flow pressure to keep the metal liquid stable; The method for detecting liquid flow abnormal image is: arranging N images newly received by the terminal in ascending order of receiving time and forming an image sequence SCN, denoting SCN(i) as the i-th of the N images in the image sequence SCN, i is a serial number, i=1, 2, …, N, and denoting SV i as the sum of all pixel values in the image SCN(i); SV1, SV2, …, SV N The average value of the N values is denoted as ASV; N is set as a value in the interval [50, 200]. Let fc(i) be the liquid flow structure of the image SCN(i), the calculation method of fc(i) is: let Sp(i) represent the number of pixels contained in SCN(i), let the value obtained by dividing ASV by Sp(i) be D(i), and the value obtained by dividing the sum of all pixel values greater than D(i) in the image SCN(i) by the sum of all pixel values less than D(i) in the image SCN(i) is taken as the liquid flow structure fc(i) of SCN(i); For N liquid flow structures fc(1), fc(2), …, fc(N) corresponding to N images, let f1 be the value obtained by subtracting fc(1) from fc(N); if the value of f1 is positive, the flow interval is defined as [0, f1]; if the value of f1 is negative, the flow interval is defined as [f1, 0]; According to the N liquid flow structures, calculate the heteroflow degree, if the value of the heteroflow degree is located outside the flow interval, mark SCN(N) as an abnormal liquid flow image, at the same time, stabilize the metal liquid by adjusting the pressure of the high-pressure gas, and send a warning signal to the monitoring room; The method for calculating the cross flow degree according to N liquid flow degrees is as follows: S1, setting a variable j, the initial value of j is set as 2, the traversal range of j is [2, N-1], and fp j-1 = fp1= fc(2)-fc(1), initializing a variable C0=fp j-1 , and turning to S2. S2, let fp be the value obtained by subtracting fc(j) from fc(j+1). j If fp j ×fp j-1 If the value of C0 is greater than 0, then update the value of C0 to fp. j +C0; if fp j ×fp j-1 If the value of C0 is less than 0, then update the value of C0 to fp. j ×(1+|C0|÷j)+C0, go to S3; S3, if the value of variable j is less than N-1, increase the value of j by 1 and go to S2; if the value of variable j is equal to or greater than N-1, go to S4; S4, let the value of C0 be the heteroflow degree.

2. The method of claim 1, wherein the metal material powder for a flexible circuit board is prepared by an aerosolization process. The method for melting the metal raw material to obtain the metal liquid is specifically: placing the metal raw material into a melting furnace for melting, generating heat inside the metal by electromagnetic induction to melt the metal raw material, and obtaining the metal liquid; wherein, a low-oxygen environment is maintained by providing inert gas during the melting process; a crucible is placed in the melting furnace for containing the metal liquid, and the crucible has a flow guide pipe at the bottom.

3. The method of claim 1, wherein the metal material powder for a flexible circuit board is prepared by gas atomization. The method for using a pressure device to pass the metal liquid into an atomization device is specifically: installing a pressure device on the top of the crucible, and continuously applying pressure to the metal liquid using the pressure device, so that the metal liquid flows out of the crucible and enters the atomization cabin in the atomization device.

4. The method of claim 1, wherein the metal material powder for a flexible circuit board is prepared by gas atomization. If an abnormal liquid flow image is detected, adjust the liquid flow pressure, including: if the liquid flow diameter of the metal liquid deviates from the preset interval, change the back pressure of the crucible by adjusting the pressure device to make the liquid flow of the metal liquid return to the preset interval; If the swing of the metal liquid flow is detected, the swing of the metal liquid flow is stabilized by adjusting the pressure of the high-pressure gas; the adjustment of the pressure of the high-pressure gas is specifically performed by a control system of the atomization device; If the breakage, dripping or disappearance of the metal liquid flow is monitored, a pre-warning signal is sent to a monitoring room, and the crucible is lifted to make the flow guide pipe leave the atomization cabin.

5. The method of claim 1, wherein the metal material powder for a flexible circuit board is prepared by gas atomization. The method for breaking the metal liquid by conveying the high-pressure gas to form the metal liquid droplets during the atomization process specifically comprises the following steps: the high-pressure gas is introduced, and the high-pressure gas is accelerated by the ring slit type nozzle in the atomization device to form a high-speed gas flow, and the high-speed gas flow breaks the metal liquid into the metal liquid droplets.

6. The method of claim 1, wherein the metal material powder for a flexible circuit board is prepared by gas atomization. The method for cooling the metal liquid droplets and collecting the metal powder specifically comprises the following steps: the metal liquid droplets are cooled and solidified during the flight of the metal liquid droplets to obtain spherical metal powder, and the spherical metal powder is collected, screened and vacuum packaged by the collecting device located at the bottom of the atomization tower in the atomization device.

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