A method and system for preparing a solder paste

Abstract

The present application relates to the technical field of solder paste preparation, and particularly relates to a solder paste preparation method and system, wherein the method comprises the following steps: step 1: obtaining metal particles of different shapes and measuring characteristic sizes of the metal particles of different shapes; step 2: calculating corresponding densities according to the measured characteristic sizes of the metal particles of different shapes and mass ratios between the metal particles of different shapes; step 3: when the solder paste is configured, selecting a mass ratio corresponding to the maximum density from the calculated densities to configure the metal particles of different shapes; and step 4: uniformly mixing the configured mixed metal particles with a preset solvent to obtain the solder paste. The solder paste preparation method can obtain an optimal proportion of metal particle materials, and then prepare a solder paste with high quality.

Description

Technical Field

[0001] This invention relates to the field of solder paste preparation technology, and in particular to a method and system for preparing solder paste. Background Technology

[0002] Third-generation wide-bandgap semiconductor devices (such as SiC and GaN) are characterized by high frequency, high power density, and high junction temperature, with their full-load operating temperature expected to exceed 200°C. This temperature far exceeds the highest temperature that traditional Si-based packaging technology can withstand (150°C). Therefore, there is an urgent need to develop new process methods and interconnect materials that meet the thermal interconnect requirements of wide-bandgap semiconductor devices.

[0003] Low-temperature silver / copper sintering interconnect technology has become the preferred interconnect material for heat-resistant packaging of wide-bandgap semiconductor devices, and its research and application are becoming increasingly widespread. Sintered silver / copper interconnect layers have a porous structure, and the pores within them can limit the conductivity of the interconnect layer to some extent. Compared to traditional single-peak spherical silver / copper solder paste, multi-peak non-spherical silver / copper solder paste can significantly increase particle density, thereby effectively reducing the porosity of the sintered silver / copper structure and improving the mechanical properties, electrical conductivity, and thermal conductivity of the sintered joint.

[0004] While there is some research foundation on multi-peak silver / copper solder paste both domestically and internationally, this research is based on repeated experiments and tests to obtain the optimal ratio of multi-peak micro / nano particles at specific sizes, and effective theoretical guidance is still lacking. Therefore, in-depth research is needed on the ratio of micro / nano particles in solder paste preparation methods. Summary of the Invention

[0005] Therefore, the technical problem to be solved by the present invention is to overcome the fact that the preparation methods of solder paste in the prior art are all based on experiments or tests regarding the ratio of micro and nano particles, and lack in-depth research on the ratio of micro and nano particles.

[0006] To solve the above-mentioned technical problems, the present invention provides a method for preparing solder paste, comprising:

[0007] Step 1: Obtain metal particles of different shapes and measure the characteristic dimensions of the metal particles of different shapes;

[0008] Step 2: Based on the measured characteristic dimensions of metal particles of different shapes and the mass ratio between metal particles of different shapes, calculate the corresponding density. The methods for calculating density include:

[0009] Mix and add metal particles of different shapes, or combine metal particles of different shapes in a preset ratio;

[0010] Set the basic parameters of the metal particles; the basic parameters include: three-dimensional spatial boundary, particle feature size, preset step size, target motion direction and number of each particle;

[0011] Based on the sum of the Z-axis coordinates of the highest point of the existing particle and the preset distance, generate the three-dimensional coordinates of the target particle on the current height plane where the sum of the Z-axis coordinates of the highest point and the preset distance is located;

[0012] Within the three-dimensional spatial boundary, the target particle is moved along the target movement direction with a preset step size, the three-dimensional coordinates of the target particle are updated, and the target particle and the existing particles are judged according to preset conditions until all the target particles to be placed are placed. Then, the density is calculated by the Monte Carlo method of solving pi.

[0013] Step 3: When preparing the solder paste, select the mass ratio corresponding to the maximum density from the calculated density to prepare metal particles of different shapes;

[0014] Step 4: Mix the prepared mixed metal particles with the preset solvent evenly to obtain solder paste.

[0015] In one embodiment of the present invention, the target particle and the existing particles are compared under preset conditions, including:

[0016] Determine whether the target particle overlaps with the existing particles; if they do not overlap, then determine the particle stability.

[0017] If the particle meets the stability condition, the target particle is added to the existing particle sequence, and it is determined whether all the target particles to be deployed have been placed; if all have been placed, the loop ends and the density calculation is performed.

[0018] In one embodiment of the present invention, if it is determined that the target particle overlaps with the existing particle, the target particle is discarded, and the sum of the Z-axis coordinates of the highest point of the existing particle and the preset distance is returned to generate the three-dimensional coordinates of the new target particle on the current height plane where the sum of the Z-axis coordinates of the highest point and the preset distance is located.

[0019] In one embodiment of the present invention, the operation of determining overlap includes:

[0020] When both the target particle and the existing particle are spheres, calculate the distance between the centers of the moving sphere and the existing sphere;

[0021] When the particles are a mixture of non-spherical and spherical particles, there are three cases:

[0022] The first case is: when judging the overlap between spheres, calculate the distance between the centers of the moving sphere and the existing sphere;

[0023] The second scenario involves determining whether the sphere overlaps with the elliptical plate. The target particle is transformed using a spatial coordinate transformation formula to establish a new three-dimensional coordinate system based on a slanted ellipse in space. Other particles are then transformed into this new three-dimensional coordinate system for further evaluation. In the new three-dimensional coordinate system x′O′y′ plane, the circle is externally tangent to the ellipse, and the trajectory of the circle's center forms an envelope. A preliminary determination of whether the sphere overlaps with the elliptical plate is made by checking whether the center of the projection of the sphere onto the x′O′y′ plane falls within the outer ellipse. The target is then evaluated using the relationship between the sphere's center Z′ and the half-thickness of the elliptical plate. The specific formula is as follows:

[0024]

[0025] The third scenario is as follows: When determining whether two elliptical pieces overlap, the target particle is transformed into a new three-dimensional coordinate system using a spatial coordinate transformation formula. Other particles are then transformed into the new three-dimensional coordinate system for judgment. During the judgment, multiple scattered points are used to describe the operation of the outer surface of the elliptical piece. The overlap is determined by whether the scattered points fall into the interior of other elliptical pieces. The slanted ellipse is an elliptical piece that is tilted in three-dimensional space.

[0026] In one embodiment of the present invention, the stability condition includes:

[0027] Any spherical particle has at least three contact points with other particles or boundaries;

[0028] When the elliptical disc moves, it does not participate in collisions, and only the effect of gravity is considered;

[0029] When the elliptic plate is stable, apply a displacement of the target length along a preset direction to make the elliptic plate reach the position of the lowest relative potential energy.

[0030] In one embodiment of the present invention, if it is determined that the particle does not meet the stability condition, the force analysis of the target particle is performed, the target motion direction is updated, and the target particle is moved along the target motion direction by a preset step size.

[0031] In one embodiment of the present invention, if the center of the projection of the sphere onto the new system x′O′y′ plane falls between the outer ellipse and the central ellipse, the force on the sphere is directed along the negative direction of the thickness of the elliptical plate; if the center of the projection falls inside the central ellipse, the force on the sphere is directed along the major axis, minor axis and direction, and obliquely downward.

[0032] In one embodiment of the present invention, if not all particles are placed, the three-dimensional coordinates of the new target particle are generated on the current height plane where the sum of the Z-axis coordinates of the highest point of the existing particles and the preset distance is located.

[0033] In one embodiment of the present invention, the preset solvent is any one of ethylene glycol, polyethylene glycol 200, polyethylene glycol 300, glycerol, and diethylene glycol.

[0034] The present invention also provides a solder paste preparation system, employing the above-described solder paste preparation method, comprising:

[0035] Acquisition and Measurement Module: Used to acquire metal particles of different shapes and measure the characteristic dimensions of metal particles of different shapes;

[0036] The calculation module is used to calculate the corresponding density based on the measured characteristic dimensions of metal particles of different shapes and the mass ratio between metal particles of different shapes. The density calculation methods include:

[0037] Mix and add metal particles of different shapes, or combine metal particles of different shapes in a preset ratio;

[0038] Set the basic parameters of the metal particles; the basic parameters include: three-dimensional spatial boundary, particle feature size, preset step size, target motion direction and number of each particle;

[0039] Based on the sum of the Z-axis coordinates of the highest point of the existing particle and the preset distance, generate the three-dimensional coordinates of the target particle on the current height plane where the sum of the Z-axis coordinates of the highest point and the preset distance is located;

[0040] Within the three-dimensional spatial boundary, the target particle is moved along the target movement direction with a preset step size, the three-dimensional coordinates of the target particle are updated, and the target particle and the existing particles are judged according to preset conditions until all the target particles to be placed are placed. Then, the density is calculated by the Monte Carlo method of solving pi.

[0041] Selection module: used to select the mass ratio corresponding to the maximum approximate density from the calculated density when configuring solder paste to configure metal particles of different shapes;

[0042] Preparation module: Used to uniformly mix the prepared mixed metal particles with a preset solvent to obtain solder paste.

[0043] Compared with the prior art, the above-described technical solution of the present invention has the following advantages:

[0044] The solder paste preparation method and system described in this invention can use the obtained optimal particle ratio for the preparation of multi-peak silver / copper solder paste. Compared with the traditional method of continuously stacking particles by solving the lowest potential energy position using a solver, the optimal particle ratio calculated by this invention (obtained through density calculation) has a significantly reduced running time and a denser particle density with the same number of particles.

[0045] The present invention is simple to calculate and fast to assume particle stability conditions, collision force and gravity when calculating the optimal particle ratio.

[0046] The silver and / or copper particles of the present invention are not limited to a fixed size; the size of each spherical particle can be different, and variations in the major and minor axes of elliptical pieces can also be achieved, for example.

[0047] This invention can improve the computational simulation efficiency of stacking and construct a model of multi-peak non-spherical particles. It can quickly and effectively obtain the density of multi-peak non-spherical particles, providing theoretical guidance for the development of high-performance multi-peak silver / copper solder paste and accelerating the research progress of new materials. Attached Figure Description

[0048] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings, wherein:

[0049] Figure 1 This is a flowchart of a method for preparing solder paste provided in a preferred embodiment of the present invention;

[0050] Figure 2 This is a diagram illustrating the process of launching equal-diameter spheres / hybrid spheres according to a preferred embodiment of the present invention;

[0051] Figure 3 This is a diagram illustrating the stability conditions and force analysis for determining the number of contact points in a preferred embodiment of the present invention.

[0052] Figure 4 This is a schematic diagram of Monte Carlo calculation of pi provided in a preferred embodiment of the present invention;

[0053] Figure 5 This is a diagram illustrating the mixing and dispensing process of spheres and elliptical pieces provided in a preferred embodiment of the present invention.

[0054] Figure 6 This is a schematic diagram of a preferred embodiment of the present invention, which uses a corresponding number of scattered points to replace the elliptical boundary.

[0055] Figure 7 This is a schematic diagram showing the elliptical pieces stacked together at a certain location in a preferred embodiment of the present invention;

[0056] Figure 8 This is a schematic diagram of adjusting the position of the ellipse by changing (x0, y0) according to a preferred embodiment of the present invention.

[0057] Figure 9 This is a schematic diagram showing the position of the sphere relative to the elliptical sheet after undergoing spatial coordinate transformation, provided in a preferred embodiment of the present invention.

[0058] Figure 10This is an elliptical envelope diagram provided in a preferred embodiment of the present invention;

[0059] Figure 11 These are four cross-sectional views of a small particle with a size r = 1 provided in a preferred embodiment of the present invention;

[0060] Figure 12 This is a three-dimensional diagram corresponding to the specific embodiment one provided in the preferred embodiment of the present invention;

[0061] Figure 13 The density corresponding to each size in the specific implementation example provided in the preferred embodiment of the present invention;

[0062] Figure 14 This is a cross-sectional view of r1 / r2 = 0.2 in a preferred embodiment of the present invention;

[0063] Figure 15 This is a three-dimensional diagram corresponding to the specific embodiment two provided in the preferred embodiment of the present invention;

[0064] Figure 16 This is a density diagram showing the mass percentages corresponding to the three size ratios in a specific embodiment of the preferred embodiment of the present invention, in Specific Example 2.

[0065] Figure 17 This is a two-dimensional cross-sectional view of a single simulation in a specific embodiment three provided in the preferred embodiment of the present invention;

[0066] Figure 18 This is a three-dimensional diagram corresponding to the specific embodiment three provided in the preferred embodiment of the present invention;

[0067] Figure 19 This is a comprehensive density diagram for each mass ratio in a specific embodiment three provided in the preferred embodiment of the present invention;

[0068] Figure 20 This is a 3D diagram corresponding to a certain operation in the fourth specific embodiment of the preferred embodiment of the present invention;

[0069] Figure 21 This is a density diagram corresponding to each mass percentage in the specific embodiment four provided in the preferred embodiment of the present invention;

[0070] Figure 22 This is a three-dimensional packing diagram of bimodal spherical and non-spherical particles when σ = 80% provided in a preferred embodiment of the present invention;

[0071] Figure 23 This is a schematic diagram illustrating the particle density variation under different sphere / elliptical sheet mass ratios provided in a preferred embodiment of the present invention.

[0072] Figure 24This is a schematic diagram of the microstructure of sintered copper patterns with different proportions provided in a preferred embodiment of the present invention;

[0073] Figure 25 This is a schematic diagram showing the change in resistivity of the sintered copper pattern with the content of submicron particles in a preferred embodiment of the present invention. Detailed Implementation

[0074] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0075] To overcome the problems of existing technologies, this invention proposes a method for preparing solder paste. This embodiment mainly improves the calculation method for the density of multi-peak non-spherical particles. By simulating the particle loading process based on their own gravity and collisions, a random distribution process is achieved in space, involving spheres of equal diameter, two different diameters, three different diameters, etc. Based on this, a random distribution method capable of mixing different particles is designed using spatial coordinate transformation formulas and digital image processing techniques. Based on the simulation results, a corresponding algorithm is designed using Monte Carlo methods to calculate the density. This reveals the relationship between density and the mass ratio of various particles when multiple particles are distributed. Finally, the optimized particle ratio is used in the preparation of multi-peak silver / copper solder paste.

[0076] The method for preparing solder paste in this embodiment specifically includes the following steps:

[0077] Step 1: Obtain metal particles of different shapes (e.g., spherical or elliptical), and measure the characteristic dimensions of the metal particles of different shapes;

[0078] It should be noted that the types of metal particles (such as silver particles, copper particles, etc.) can be the same or different. The characteristic dimensions of metal particles of different shapes may include, for example, the radius of spherical particles, and the major axis, minor axis, and thickness of elliptical plate-shaped particles.

[0079] Step 2: Calculate the corresponding density based on the measured characteristic dimensions of metal particles of different shapes and the mass ratio between metal particles of different shapes;

[0080] Step 3: When preparing the solder paste, select the mass ratio corresponding to the maximum density from the calculated density to prepare metal particles of different shapes;

[0081] Step 4: Mix the prepared mixed metal particles with the preset solvent evenly to prepare multi-peak solder paste.

[0082] The metal particles in step 1 can be, for example, silver and / or copper particles, which can be all silver particles, all copper particles, or a combination of silver and copper particles.

[0083] The mass ratio between metal particles of different shapes (taking silver and / or copper particles as an example) in step 2 includes at least two different shapes of silver and / or copper particles, for example, the following situations:

[0084] (1) It can be the mass ratio between two types of spherical silver particles with different radii (a total of two types); or the mass ratio between two types of elliptical copper particles with different radii (a total of two types).

[0085] (2) It can also be the mass ratio between spherical silver particles and elliptical copper particles (a total of 2 types).

[0086] (3) Or it could be the mass ratio between two types of elliptical silver particles of different sizes and one type of spherical copper particle (a total of three types).

[0087] In step 3, when selecting the mass ratio corresponding to the maximum approximate density from the calculated density to configure metal particles of different shapes (taking silver and / or copper particles as an example), it is assumed that step 2 uses the mass ratio between two types of spherical silver particles with different radii (a total of two types). There are three assumed mass ratios: 2:1, 3:1, and 4:1. If 3:1 corresponds to the maximum approximate density, then the mass ratio of 3:1 is selected.

[0088] The preset solvent in step 4 includes, but is not limited to, any one of ethylene glycol (EG), polyethylene glycol 200, polyethylene glycol 300, glycerol, and diethylene glycol.

[0089] The following example illustrates this: Micrometer-sized copper (elliptical sheet, major axis 2±0.05μm, minor axis 1.6±0.04μm, thickness 0.3±0.03μm) and submicrometer-sized copper (sphere, diameter 0.2±0.02μm). In the simulation algorithm for multi-peak non-spherical particle packing, this embodiment sets the parameters of the spherical particles to r1=0.5 according to the principle of proportional scaling, and the parameters of the elliptical particles to a=5 (half of the major axis of the elliptical sheet), b=4 (half of the minor axis of the elliptical sheet), d=0.75 (half of the thickness of the elliptical sheet), θ max =10°, num_point=16, submicron spherical particle mass percentage σ ranges from 50% to 100%. Figure 22 This is a three-dimensional overlay plot when σ = 80%. From... Figure 23 According to the simulated density plot, the density curve reaches its maximum value when σ = 70%.

[0090] To verify the feasibility of computer-aided design of multi-peaked non-spherical copper solder paste, multiple sets of multi-peaked non-spherical copper solder pastes were prepared by mechanically mixing micron-sized copper flakes, submicron-sized copper particles, and PEG 300 solvent in different proportions. Next, the copper solder paste was printed onto glass slides using stencil printing and sintered at 280℃ in a nitrogen atmosphere for 30 minutes. Finally, the surface morphology and microstructure of the sintered copper patterns were observed using a scanning electron microscope (SEM, EVO18, Carl Zeiss-Ag), and the resistivity of the sintered copper patterns was evaluated using a four-probe resistivity meter (ST2263, Suzhou Lattice Electronics). Figure 24 The surface microstructures of sintered copper patterns with different submicron particle contents are shown. As can be seen from the figures, the surface of the sintered copper becomes denser and the porosity decreases significantly with increasing submicron particle content. Figure 25 The resistivity variation of sintered copper patterns with different submicron particle contents is shown. The resistivity of the sintered copper pattern is lowest when the submicron particle content is 70%. However, when the submicron particle content exceeds 70%, macroscopic cracks appear in the sintered pattern, resulting in a relatively high macroscopic resistivity even when the local microstructure is particularly dense. The macroscopic cracks may be due to the higher sintering activity of the submicron particles, coupled with lower particle density, leading to uneven densification shrinkage during sintering. Therefore, this embodiment suggests that the sintering test results of the multi-peak non-spherical copper solder paste are consistent with the optimal ratio designed by computer-aided design.

[0091] The calculation methods for density in step 2 include:

[0092] S201: Mix and place metal particles of different shapes, or combine metal particles of different shapes in a preset ratio. In this embodiment, the metal particles include, but are not limited to, circular pieces, elliptical pieces, spheres of equal diameter (several metal particles with the same radius), mixed spheres (several metal particles with different radii), and triangular pieces.

[0093] S202: Set the basic parameters of the metal particles; the basic parameters include: three-dimensional spatial boundary, particle feature size, preset step size, target motion direction and number of each particle;

[0094] S203: Based on the sum of the Z-axis coordinates of the highest point of the existing particle and the preset distance, generate the three-dimensional coordinates of the target particle on the current height plane where the sum of the Z-axis coordinates of the highest point and the preset distance is located;

[0095] S204: Within the three-dimensional space boundary, the target particle is moved along the target movement direction with a preset step size, the three-dimensional coordinates of the target particle are updated, and the target particle and the existing particles are judged according to preset conditions until all the target particles to be placed (the number of target particles to be placed is set in advance) are placed. Then, the density is calculated by the Monte Carlo method of solving pi, and the result after the calculation is saved to the target file.

[0096] S205: Based on the calculation results, draw a three-dimensional diagram or a two-dimensional cross-sectional diagram.

[0097] In some possible implementations, a preset condition judgment is made between the target particle and the existing particles, including:

[0098] Determine whether the target particle overlaps with the existing particles; if they do not overlap, then determine the particle stability.

[0099] If the particle meets the stability condition, the target particle is added to the existing particle sequence, and it is determined whether all the target particles to be deployed have been placed; if all have been placed, the loop ends and the density calculation is performed.

[0100] In some possible implementations, if it is determined that the target particle overlaps with the existing particle, the target particle is discarded, and the sum of the Z-axis coordinates of the highest point of the existing particle and a preset distance is returned to generate the three-dimensional coordinates of the new target particle on the current height plane where the sum of the Z-axis coordinates of the highest point and the preset distance is located.

[0101] In some possible implementations, the operation of determining overlap includes:

[0102] When both the target particle and the existing particle are spheres, calculate the distance between the centers of the moving sphere and the existing sphere;

[0103] When the particles are a mixture of non-spherical and spherical particles (this embodiment does not consider the mixing of purely non-spherical particles, but must be a mixture of spherical and non-spherical particles), there are three cases:

[0104] The first case is: when judging the overlap between spheres, calculate the distance between the centers of the moving sphere and the existing sphere;

[0105] The second scenario involves determining whether the sphere overlaps with the elliptical plate. The target particle is transformed using a spatial coordinate transformation formula to establish a new three-dimensional coordinate system based on a slanted ellipse in space. Other particles are then transformed into this new three-dimensional coordinate system for further evaluation. In the new three-dimensional coordinate system x′O′y′ plane, the circle is externally tangent to the ellipse, and the trajectory of the circle's center forms an envelope. A preliminary determination of whether the sphere overlaps with the elliptical plate is made by checking whether the center of the projection of the sphere onto the x′O′y′ plane falls within the outer ellipse. The target is then evaluated using the relationship between the sphere's center Z′ and the half-thickness of the elliptical plate. The specific formula is as follows:

[0106]

[0107] The third scenario is as follows: When determining whether two elliptical pieces overlap, the target particle is transformed into a new three-dimensional coordinate system using a spatial coordinate transformation formula. Other particles are then transformed into the new three-dimensional coordinate system for judgment. During the judgment, multiple scattered points are used to describe the operation of the outer surface of the elliptical piece. The overlap is determined by whether the scattered points fall into the interior of other elliptical pieces. The slanted ellipse is an elliptical piece that is tilted in three-dimensional space (not placed horizontally).

[0108] In some possible implementations, the stability conditions include:

[0109] Any spherical particle has at least three contact points with other particles or boundaries;

[0110] When the elliptical disc moves, it does not participate in collisions, and only the effect of gravity is considered;

[0111] When the elliptical piece is stable, a displacement of the target length is applied to the elliptical piece along a preset direction so that the elliptical piece reaches the position of the relative lowest potential energy (the elliptical piece does not participate in the collision, but only falls down within the three-dimensional space boundary to reach the position of the relative lowest potential energy, which may not be the lowest potential energy position in three-dimensional space).

[0112] In some possible implementations, if it is determined that the particle does not meet the stability condition, then the force analysis of the target particle is performed, the target motion direction is updated, and the target particle is moved along the target motion direction by a preset step size.

[0113] In some possible implementations, if the center of the projection of the sphere onto the x′O′y′ plane of the new system falls between the outer ellipse and the central ellipse, the direction of the force on the sphere is along the negative direction of the thickness of the elliptical plate; if the center of the projection falls inside the central ellipse, the direction of the force on the sphere is along the major axis, minor axis and direction, and obliquely downward.

[0114] In some possible implementations, if not all particles are placed, the system returns the sum of the Z-axis coordinates of the highest point of the existing particles and a preset distance, and generates the three-dimensional coordinates of the new target particles on the current height plane where the sum of the Z-axis coordinates of the highest point and the preset distance is located.

[0115] It should be noted that, due to the special nature of the elliptical plate, this invention is divided into two parts: equal diameter spheres / mixed spheres and a mixture of elliptical plates and spheres.

[0116] In one example, spheres of equal diameter / mixed spheres:

[0117] Considering the influence of gravity, to achieve the random drop process, the coordinates (x0, y0, z0) of the ball's center point are randomly generated within a plane at a certain height, denoted as O0. The initial direction of motion is downward, denoted as dir = [0, 0, -1]. The ball moves from its initial position according to a set step size. O0 and dir are continuously updated iteratively until the ball stabilizes.

[0118] See Figure 2 , Figure 2 This is a diagram illustrating the process of dropping equal-diameter spheres / mixed spheres.

[0119] Step 1, set basic parameters:

[0120] Three-dimensional space boundary (taking a cuboid as an example, only its length and width need to be set, the height is unlimited, and the size setting format is a one-dimensional vector, such as S=[a,b], where a and b represent half of the length and width);

[0121] Particle size: The radii of different spherical particles are represented by r1, r2, r3... respectively;

[0122] Step size: The total distance the particle travels in each motion, taken as 0.1·r1;

[0123] Direction of motion (dir): Due to gravity, the initial direction of motion is dir = [0, 0, -1]. Later, through collisions with particles and spatial boundaries, dir is continuously updated during subsequent motion.

[0124] The number of each particle: The number of each particle is calculated based on its mass ratio and size relationship. Various balls are represented by numbers and set as a one-dimensional vector called sequence p. This sequence is shuffled to achieve random drop.

[0125] For two particles, the ratio of the mass of the smaller particle to the mass of the larger particle is: ratio = [e, g]; where e + g = 10.

[0126] Number of small particles: Number of large particles: By setting each large particle as a percentage of the total number of particles to be equivalent to n0 large particles, we can calculate the number of large particles: n2 = g·n0; the number of small particles: n1 = ra1·n2; thus, the number of each particle: num0 = [n1,n2]; using 0 to represent small particles and 1 to represent large particles, we have p = [0,0,0,……,1,1,1,1,……]; where the p sequence contains n1 zeros and n2 ones. Then, the sequence is shuffled.

[0127] Step two: Based on the z-axis coordinates of the highest point of the existing particles, add a preset distance to the z-axis coordinates of the highest point to obtain new z-axis coordinates. Randomly generate a center point (x0, y0, z0) on the plane at this height (i.e., the new z-axis coordinates). This particle is called the new particle. The specific size is determined by the sequence p. If there are already 1000 particles, and the 1001st number in sequence p is 0, then the size of the new particle is the particle size corresponding to the number 0.

[0128] Step 3: The new particle moves along the direction of motion dir with a fixed step size step, updating the coordinates of the sphere's center point (x0, y0, z0). Then, the distance dis between the new particle and existing particles at this position is calculated. Next, three checks need to be performed;

[0129] Decision 1: Determine if the new particle overlaps with existing particles. If they overlap, discard the new particle and return to step 2. If they do not overlap, proceed to decision 2.

[0130] The condition for determining non-overlapping is that when the distance between two particles is dis = 2·r, they are just in contact. However, under the conditions that the contact point needs to be calculated and there is no large overlap, it is assumed that when dis ≥ 1.9·r, the particles do not overlap.

[0131] Therefore, the non-overlapping condition is dis ≥ 1.9·r; Where: (x0, y0, z0) are the current coordinates of the new particle, (x i ,y i ,z i ) represents the coordinates of existing particles.

[0132] Judgment 2: If the number of contact points is insufficient to meet the stability condition, perform force analysis on the new particle, update the motion direction (dir), and repeat step 3. If the number of contact points meets the stability condition, add the new particle to the existing particle sequence and proceed to Judgment 3.

[0133] See Figure 3 , Figure 3To determine the stability condition and force analysis diagram for particle 2, the following points should be noted regarding the stability condition and force analysis for particle 2: Particle stability condition assumption: Any spherical particle has at least three contact points with other particles or boundaries; Particle collision force assumption: The force exerted on the particle at each contact point is the same in magnitude; Resultant force assumption: The resultant force on the particle at each contact point is equal to the gravity.

[0134] It should be noted that the stability of the bottom layer of particles does not require three contact points. Generally, the first layer often has only one contact point with the bottom of the space, but it can still be stable. Therefore, to avoid this situation, before the actual deployment, the space is divided into grids, the sequence is shuffled, and traversed to generate a layer of small particles at the bottom layer (this layer does not participate in the particle counting).

[0135] For example, when a new particle has two contact points, and the direction of the force exerted on the new particle by the two contact points is tow1 = (t x1 ,t y1 ,t z1 ), tow2=(t x2 ,t y2 ,t z2 Based on the particle collision force assumption, under the vector composition rule, we have tow3 = (t x1 +t x2 ,t y1 +t y2 ,t z1 +t z2 After normalization, tow3 = (t x3 ,t y3 ,t z3 ), the gravity unit vector tow0=(0,0,-1), based on the assumption of the resultant force on the particle, dir is updated after the collision; dir=tow3+tow0.

[0136] Decision 3: Have all particles been placed? If all particles have been placed, break the loop and proceed to step 4. If any particles have not been placed, return to step 2.

[0137] Step four, density calculation. Density calculation uses the Monte Carlo method for solving pi (π). For example... Figure 4 To solve for pi in Monte Carlo simulation, generate T random points within a square with side length 1, and count the number N points that fall inside the circle. To avoid the influence of spatial boundaries during deployment, a core area is delineated within the deployed space for density calculation. The calculation is then saved to a specified file.

[0138] Step 5: Automatically generate and save the 3D graphics / 2D cross-sectional views of the simulation results through self-coding.

[0139] In another example, spheres and elliptical pieces are mixed:

[0140] See Figure 5 , Figure 5 A diagram illustrating the process of mixing and dropping spheres and elliptical pieces.

[0141] Step 1: Set basic parameters: 3D spatial boundary, step size, and direction of motion (dir). These three parameters are the same as those for spheres of equal diameter / hybrid spheres; particle size, sphere particle radius r, semi-major axis a, semi-minor axis b, and semi-thickness d of the ellipse; maximum allowable tilt angle θ of the ellipse: In reality, ellipse pieces are not flat in space, but have a certain tilt angle. Take θ = ±10°; num_point value. Select num_point scattered points on an ellipse to replace all the points on the top. Since the distance between the ellipse and other particles cannot be calculated using the center distance between spheres as in the case of spheres, the ellipse can only be replaced by the upper, middle, and lower elliptical surfaces, and each elliptical surface is replaced by num_point points. Therefore, an ellipse is actually described by 3·num_point scattered points. Substitute these scattered points into the equations of other particles, and by determining whether these scattered points are located inside existing particles, it can be determined whether the ellipse overlaps with other particles. The value of num_point can be determined according to Table 1. Figure 6 Make a selection. Figure 6 The corresponding number of scattered points are used to replace the elliptical boundary.

[0142] Table 1

[0143]

[0144] Because the dimensions of the elliptical discs measured in the laboratory differed significantly from the dimensions of the spheres, and because the elliptical discs lacked the regularity of a sphere, the number of elliptical discs was fixed in the actual simulation (generally set to 20). Based on the set mass ratio, sphere:elliptical disc = ratio[e,g], the corresponding number of spheres was calculated according to the set dimensions. Other operations were performed using the same method for spheres of equal diameter / mixed spheres.

[0145] For example, spheres: elliptical slices (the number of elliptical slices is set to nu), ratio = [e, g], then the number of spheres num: Let 0 represent an elliptical piece and 1 represent a spherical particle, then p = [0,0,0,……,1,1,1,1,……11]. Shuffle the sequence p (the sequence p contains nu of 0s and num of 1s).

[0146] Step two: Based on the z-axis coordinates of the highest point of the existing particles, and adding a preset distance, randomly generate a center point (x0, y0, z0) on the height plane where the sum of the z-axis coordinates of the highest point and the preset distance lies. This particle is called the new particle. The specific size is determined by the sequence p. If there are already 1000 particles, and the 1001st number in sequence p is 0, then the size of the new particle is the particle size corresponding to the number 0.

[0147] Step 3: The new particle moves along the direction of motion (dir) with a fixed step size (step), updating the center point coordinates. Then, three checks need to be performed:

[0148] Decision 1: Determine if the new particle overlaps with existing particles. If they overlap, discard the new particle and return to step 2. If they do not overlap, proceed to decision 2.

[0149] The conditions for determining non-overlapping are as follows: Spheres with the same diameter or mixed diameters are not required to overlap, which will not be elaborated here; the determination of non-overlapping between ellipses is essentially a determination of whether a point is inside the ellipse.

[0150] Determining the position of a spatial ellipse requires 12 parameters, such as [x0, y0, z0, n1, n2, n3, v1, v2, v3, u, u2, u3].

[0151] Where: (x0, y0, z0) are the coordinates of the center point of the ellipse; (n1, n2, n3) are the directions of the half-thickness; (v1, v2, v3) are the directions of the major semi-axis; (u, u2, u3) are the directions of the minor semi-axis.

[0152] Parametric equations of the central elliptical surface of the spatial elliptical plate:

[0153] Parametric equations of the upper and lower elliptical surfaces of the spatial elliptical plate:

[0154] After the new ellipse is determined, the coordinates of the 3·num_point scattered points are determined according to the two parametric equations above.

[0155] Spatial coordinate transformation formula:

[0156] For example, the overlap determination between the new ellipse and the first ellipse piece:

[0157] Because the first ellipse is tilted at a certain angle in space, it is not conducive to judgment. Therefore, a new coordinate system is established with its major semi-axis, minor semi-axis, semi-thickness, and center point as the x', y', and z' axes, and the origin o'. The 3·num_point scattered points representing the new ellipse are transformed to the new coordinate system using the spatial coordinate transformation formula mentioned above. The judgment is then performed. The judgment process is as follows:

[0158] First, take the absolute values ​​of the z' coordinates of the 3 * num_point scattered points, considering only the cases where they are above the x'o'y' plane. Then, extract the coordinates of the smallest z' value. If z' satisfies... min If z' ≥ d, it means that the ellipses do not overlap. If z' does not satisfy d, then the ellipses do not overlap. min If ≥d, continue with the overlap check.

[0159] Secondly, when z′ is not satisfied min Given that z′ ≥ d, we select all scattered points from 3 * num_points that do not satisfy z′ ≥ d. In this case, we can ignore the z′ axis, and the problem is transformed into a planar problem: whether these scattered points lie inside an ellipse with a as the major semi-axis, b as the minor semi-axis, and centered at the origin. If they do not satisfy the condition... This indicates that the new ellipse does not overlap with the existing ellipse, so return to step three and continue the loop. If the condition is met... This indicates that there is an overlap between the new ellipse and the existing ellipse. In this case, the core parameters (x0, y0, z0) of the new ellipse are returned to the values ​​from the previous loop, and the ellipse position is adjusted.

[0160] Ellipse Position Adjustment: Due to the special nature of ellipses, they do not participate in collisions during the simulation and only follow the principle of minimum potential energy. From the previous operation to this point, it means that without changing (x0, y0), z0 has already reached its minimum value. Therefore, (x0, y0, z0) is saved to (x... t ,y t ,z min Then change (x0, y0) and repeat step three. If z0 is returned in the final result... <z min If the condition is met, then save the new ellipse. If not, then use (x... t ,y t ,z min )save.

[0161] Change the selection of (x0, y0): Randomize the selection in four directions: [1, 0, 0], [-1, 0, 0], [0, 1, 0], and [0, -1, 0]. Then, offset (x0, y0) by a certain distance according to the selected direction to create a new (x0, y0). Without this operation, the following will occur: Figure 4 In this situation, the elliptical pieces continuously stack higher at a certain position, while other positions remain empty. See details. Figure 7 This is a schematic diagram showing how elliptical pieces are stacked together in a specific location. Figure 8 A schematic diagram showing how to adjust the position of the ellipse to change (x0, y0).

[0162] When the generated moving particles are spheres, the moving spheres undergo iteration in the same way as in the random stacking algorithm for spheres. The iteration process will not be elaborated here. The difference lies in the analysis of the overlap, contact, and force conditions between the moving spheres and the elliptical cylinders.

[0163] Whether the sphere and the elliptical cylinder overlap needs to be determined regardless of whether the moving particle is a sphere or an elliptical cylinder. However, the contact and force between the sphere and the elliptical cylinder are only necessary when the moving particle is a sphere.

[0164] With elliptical cylinder Let O0 be x′, y′, z′, and O′ in the new coordinate system. Using the spatial coordinate transformation formula described above, the coordinates of the sphere's center [x0, y0, z0] are transformed to [x', y′, z′] in the new coordinate system. The relationship between the transformed sphere and the elliptical cylinder is shown below. Figure 9 .

[0165] First, ignore z', meaning all particles are projected onto the x'o'y' plane. Since a sphere's projection onto any plane is always a circle with the same radius as the sphere, while an elliptical cylinder projects as an ellipse with a as its major axis, b as its minor axis, and its center at the origin, the problem is temporarily transformed into determining whether the circle and the ellipse overlap on the plane.

[0166] If, on a plane, a circle is always externally tangent to an ellipse, then the locus of the circle's center will form an envelope outside the ellipse (e.g., ...). Figure 10 At this point, the following will occur:

[0167] Ellipse parametric equations:

[0168] Parametric equation of a circle:

[0169] In the formula, [x′,y′] are the coordinates of the center of the circle projected onto the x'o'y' plane, and r is the radius of the corresponding circle.

[0170] If the circle is always tangent to the ellipse, then the equation of the center of the circle (the equation of the envelope) is:

[0171] from Figure 10 As can be seen, the envelope is actually a quasi-ellipse, so we use the equation of an ellipse to approximate it. The approximate elliptical equation of the outer envelope is:

[0172] Approximate elliptic equation of the outer envelope:

[0173] Therefore, only the spherical coordinates need to satisfy... We can assume that the sphere and the elliptical cylinder do not overlap, where r0 is the radius of the moving sphere.

[0174] Although the above operations can initially determine that there is no overlap between some spheres and the elliptic cylinder, this is not enough. It is also necessary to then determine the spheres whose projected centers fall inside the envelope line. Take the absolute value of the coordinates of the sphere center r0 and only consider the case above the c'o'y' plane.

[0175] If |z′|>d + r0 is satisfied, it means that there is no contact between the sphere and the ellipse, where r0 is the radius of the moving sphere;

[0176] If |z′|>d + r0 is not satisfied, then continue to make a judgment;

[0177] If both the formula d + r0 - step ≤ |z′| ≤ d + r0 and are satisfied, it means that the moving sphere contacts the upper elliptical surface of the elliptic cylinder. The contact force is along the major axis, minor axis and direction, and is guaranteed to be obliquely downward. (For the moving sphere, it can only contact the upper elliptical surface, rather than the lower elliptical surface. When it is used to judge the moving ellipse and the sphere, the contact situation does not need to be considered.)

[0178] If the formula d + r0 - step ≤ |z′| ≤ d + r0 is not satisfied but is satisfied, it means that there is an overlap between the sphere and the elliptic cylinder. The remaining cases are that the sphere is located between the elliptic cylinder and the outer envelope line. At this time, it can be simply considered that this part of the sphere contacts the side surface of the elliptic cylinder. The contact force is along the negative direction of the semi-thickness d of the elliptic cylinder. It is also possible to then make the following judgment:

[0179] <00​​​​​​​​​​​​​​​​​​​​

[0186]

[0187] Judgment 2: When the new particle is a sphere, particle stability is assessed. If the number of contact points is insufficient to meet the stability condition, force analysis is performed on the new sphere, the motion direction dir is updated, and step 3 is repeated. If the number of contact points meets the stability condition, the new particle is added to the existing particle sequence, and judgment 3 (spheres of equal diameter / mixed spheres) is performed.

[0188] Decision 3: Have all particles been placed? If all particles have been placed, break the loop and proceed to step 4. If any particles have not been placed, return to step 2.

[0189] Step four: Density calculation. Whether a point is inside an elliptical plate is determined by referring to the method for determining whether two elliptical plates are used. The rest is the same as for spheres / mixed spheres of equal diameter.

[0190] Step 5: Automatically generate and save the 3D graphics / 2D cross-sectional views of the simulation results through self-coding.

[0191] In Specific Implementation Method 1, for spheres of equal diameter: The spatial boundary S = [20, 20], particle size r = 1, and particle count 8000; the spatial boundary S = [20, 20], particle size r = 2, and particle count 1000; the spatial boundary S = [20, 20], particle size r = 3, and particle count 800; the spatial boundary S = [20, 20], particle size r = 4, and particle count 500; the spatial boundary S = [20, 20], particle size r = 5, and particle count 400; the spatial boundary S = [20, 20], particle size r = 6, and particle count 200. See details below. Figure 11 Four cross-sectional views of small particles with size r = 1. Figure 12 This is the 3D diagram corresponding to the first specific embodiment described above. Figure 13 This refers to the density corresponding to each size in the specific implementation example above.

[0192] In the second specific implementation method, the dual-particle hybrid sphere is configured as follows: The spatial boundary is set to S = [20, 20], the small particle size r1 = 1, and the large particle size r2 = 5, i.e., r1 / r2 = 0.2. The mass of the small particles ranges from 0 to 1 of the total mass, with two large particles for every 0.1% of the total mass. Alternatively, the spatial boundary is set to S = [20, 20], the small particle size r1 = 1, and the large particle size r2 = 4, i.e., r1 / r2 = 0.25. The mass of the small particles ranges from 0 to 1 of the total mass, with two large particles for every 0.1% of the total mass. Another implementation method is set to S = [20, 20], the small particle size r1 = 1, and the large particle size r2 = 2.5, i.e., r1 / r2 = 0.4. The mass of the small particles ranges from 0 to 1 of the total mass, with two large particles for every 0.1% of the total mass. See details below. Figure 14 For one of the times r1 / r2 = 0.2, see the cross-sectional view. Figure 15 This is the corresponding 3D diagram in the second specific embodiment described above. Figure 16 This is a density diagram showing the mass percentage corresponding to the three size ratios in the above-mentioned specific implementation example two.

[0193] In the third specific implementation method, the three-particle mixed sphere is configured with the following spatial boundaries: S = [40, 40], small particle size r1 = 1, medium particle size r2 = 4, and large particle size r3 = 16, i.e., r1 / r2 = 0.25 and r2 / r3 = 0.25. For every 0.1% of the total mass of the large particles, there are two large particles. Small particles account for 0% of the total mass, medium particles range from 0 to 1%; small particles account for 0.1% of the total mass, medium particles range from 0 to 0.9%; small particles account for 0.2% of the total mass, medium particles range from 0 to 0.8%; small particles account for 0.3% of the total mass, medium particles range from 0 to 0.7%; small particles account for 0.4% of the total mass, medium particles range from 0 to 0.6%; small particles account for 0.5% of the total mass, medium particles range from 0 to 0.5%; small particles account for 0.6% of the total mass, medium particles range from 0 to 0.4%; small particles account for 0.7% of the total mass, medium particles range from 0 to 0.3%; small particles account for 0.8% of the total mass, medium particles range from 0 to 0.2%; small particles account for 0.9% of the total mass, medium particles range from 0 to 0.1%; small particles account for 1% of the total mass, medium particles account for 0%. See details below. Figure 17 This is a two-dimensional cross-sectional view of a single simulation in the above-described specific embodiment three. Figure 18 This is the corresponding 3D diagram in the above specific embodiment three. Figure 19 This is a comprehensive density diagram for each mass ratio in the above-described specific embodiment three.

[0194] In the fourth specific implementation method, spheres and elliptical plates are mixed: the spatial boundary is set to S = [25, 25], the maximum tilt angle is 10°, the num_point value is 16, the sphere particle size is r = 1, and the elliptical plate size is a = 10, b = 8, d = 3. The mass of the sphere particle accounts for 0-1% of the total mass. The number of elliptical plates is fixed at 20. See details... Figure 20 This is the 3D graph corresponding to a certain operation in the above specific embodiment four. Figure 21 This is a density diagram corresponding to each mass percentage in the above specific embodiment four.

[0195] The dimensions of the sphere and elliptical disc are derived from actual measurements, scaled down accordingly. Figure 21 It can be seen that the density reaches its maximum when the mass ratio of the microspheres reaches around 0.6. This is almost identical to the experimentally measured data.

[0196] The present invention also provides a solder paste preparation system, employing the solder paste preparation method described in any of the above embodiments, comprising:

[0197] Acquisition and Measurement Module: Used to acquire metal particles of different shapes and measure the characteristic dimensions of metal particles of different shapes;

[0198] The calculation module is used to calculate the corresponding density based on the measured characteristic dimensions of metal particles of different shapes and the mass ratio between metal particles of different shapes. The density calculation methods include:

[0199] Mix and add metal particles of different shapes, or combine metal particles of different shapes in a preset ratio;

[0200] Set the basic parameters of the metal particles; the basic parameters include: three-dimensional spatial boundary, particle feature size, preset step size, target motion direction and number of each particle;

[0201] Based on the sum of the Z-axis coordinates of the highest point of the existing particle and the preset distance, generate the three-dimensional coordinates of the target particle on the current height plane where the sum of the Z-axis coordinates of the highest point and the preset distance is located;

[0202] Within the three-dimensional spatial boundary, the target particle is moved along the target movement direction with a preset step size, the three-dimensional coordinates of the target particle are updated, and the target particle and the existing particles are judged according to preset conditions until all the target particles to be placed are placed. Then, the density is calculated by the Monte Carlo method of solving pi.

[0203] Selection module: used to select the mass ratio corresponding to the maximum approximate density from the calculated density when configuring solder paste to configure metal particles of different shapes;

[0204] Preparation module: Used to uniformly mix the prepared mixed metal particles with a preset solvent to obtain solder paste.

[0205] The present invention also provides an electronic device, including: a processor, a memory, and a bus, wherein the memory stores machine-readable instructions executable by the processor, and when the electronic device is running, the processor communicates with the memory via the bus, and the machine-readable instructions are executed by the processor to perform the steps of any of the solder paste preparation methods described in the above embodiments.

[0206] The present invention also provides a computer-readable storage medium storing a computer program, which, when executed by a processor, performs the steps of the solder paste preparation method as described in any of the above embodiments.

[0207] In summary, the solder paste preparation method and system provided by this invention can improve the computational simulation efficiency of stacking and construct a model of multi-peak non-spherical particles when preparing multi-peak silver / copper solder paste. It can quickly and effectively obtain the density of multi-peak non-spherical particles, providing theoretical guidance for the development of high-performance multi-peak silver / copper solder paste and accelerating the research progress of new materials.

[0208] 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.

[0209] This application is described with reference to flowchart illustrations and / or block diagrams of methods according to embodiments of this application.

[0210] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing solder paste, characterized in that, include: Step 1: Obtain metal particles of different shapes and measure the characteristic dimensions of the metal particles of different shapes; Step 2: Based on the measured characteristic dimensions of metal particles of different shapes and the mass ratio between metal particles of different shapes, calculate the corresponding density. The methods for calculating density include: Mix and add metal particles of different shapes, or combine metal particles of different shapes in a preset ratio; Set the basic parameters of the metal particles; the basic parameters include: three-dimensional spatial boundary, particle feature size, preset step size, target motion direction and number of each particle; Based on the sum of the Z-axis coordinates of the highest point of the existing particle and the preset distance, generate the three-dimensional coordinates of the target particle on the current height plane where the sum of the Z-axis coordinates of the highest point and the preset distance is located; Within the three-dimensional spatial boundary, the target particle is moved along the target movement direction with a preset step size, the three-dimensional coordinates of the target particle are updated, and the target particle and the existing particles are judged according to preset conditions until all the target particles to be placed are placed. Then, the density is calculated by the Monte Carlo method of solving pi. Step 3: When preparing the solder paste, select the mass ratio corresponding to the maximum density from the calculated density to prepare metal particles of different shapes; Step 4: Mix the prepared mixed metal particles with the preset solvent evenly to obtain solder paste.

2. The method for preparing solder paste according to claim 1, characterized in that, The target particle and the existing particles are compared under preset conditions, including: Determine whether the target particle overlaps with the existing particles; if they do not overlap, then determine the particle stability. If the particle meets the stability condition, the target particle is added to the existing particle sequence, and it is determined whether all the target particles to be deployed have been placed; if all have been placed, the loop ends and the density calculation is performed.

3. The method for preparing solder paste according to claim 2, characterized in that, If it is determined that the target particle overlaps with the existing particle, the target particle is discarded, and the three-dimensional coordinates of the new target particle are generated on the current height plane where the sum of the Z-axis coordinates of the highest point of the existing particle and the preset distance is located.

4. The method for preparing solder paste according to claim 2, characterized in that, The operations for determining overlap include: When both the target particle and the existing particle are spheres, calculate the distance between the centers of the moving sphere and the existing sphere; When the particles are a mixture of non-spherical and spherical particles, there are three cases: The first case is: when judging the overlap between spheres, calculate the distance between the centers of the moving sphere and the existing sphere; The second scenario involves determining the overlap between the sphere and the elliptical disc. The target particle is then transformed using a spatial coordinate transformation formula to establish a new three-dimensional coordinate system based on a slanted ellipse in space. Other particles are then transferred to this new three-dimensional coordinate system for further evaluation. The plane is externally tangent to the ellipse, and the trajectory of the circle's center forms the envelope; by determining the position of the sphere in the new three-dimensional coordinate system... To preliminarily determine whether the sphere and the elliptical disc overlap, we can check whether the center of the plane projection falls inside the outer ellipse; using the center of the sphere... Target determination is performed based on the relationship between the elliptical sheet's half-thickness and the target. The third scenario is as follows: When determining whether two elliptical pieces overlap, the target particle is transformed into a new three-dimensional coordinate system using a spatial coordinate transformation formula. Other particles are then transformed into the new three-dimensional coordinate system for judgment. During the judgment, multiple scattered points are used to describe the operation of the outer surface of the elliptical piece. The overlap is determined by whether the scattered points fall into the interior of other elliptical pieces. The ellipse is an elliptical piece that is tilted in three-dimensional space.

5. The method for preparing solder paste according to claim 2, characterized in that, The stability conditions include: Any spherical particle has at least three contact points with other particles or boundaries; When the elliptical disc moves, it does not participate in collisions, and only the effect of gravity is considered; When the elliptic plate is stable, apply a displacement of the target length along a preset direction to make the elliptic plate reach the position of the lowest relative potential energy.

6. The method for preparing solder paste according to claim 2, characterized in that, If the particle is determined not to meet the stability condition, a force analysis is performed on the target particle, the target motion direction is updated, and the target particle is moved along the target motion direction by a preset step size.

7. The method for preparing solder paste according to claim 4, wherein the sphere is in the new three-dimensional coordinate system If the center of the projection falls between the outer ellipse and the central ellipse, the force on the sphere is directed along the negative direction of the elliptical thickness; if the center of the projection falls inside the central ellipse, the force on the sphere is directed diagonally downwards.

8. The method for preparing solder paste according to claim 3, characterized in that, If not all particles are placed, the system returns the sum of the Z-axis coordinates of the highest point of the existing particles and the preset distance, and generates the three-dimensional coordinates of the new target particle on the current height plane where the sum of the Z-axis coordinates of the highest point and the preset distance is located.

9. The method for preparing solder paste according to claim 3, characterized in that, The preset solvent is any one of ethylene glycol, polyethylene glycol 200, polyethylene glycol 300, glycerol, and diethylene glycol.

10. A solder paste preparation system, employing the solder paste preparation method according to any one of claims 1-9, characterized in that, include: Acquisition and Measurement Module: Used to acquire metal particles of different shapes and measure the characteristic dimensions of metal particles of different shapes; The calculation module is used to calculate the corresponding density based on the measured characteristic dimensions of metal particles of different shapes and the mass ratio between metal particles of different shapes. The density calculation methods include: Mix and add metal particles of different shapes, or combine metal particles of different shapes in a preset ratio; Set the basic parameters of the metal particles; the basic parameters include: three-dimensional spatial boundary, particle feature size, preset step size, target motion direction and number of each particle; Based on the sum of the Z-axis coordinates of the highest point of the existing particle and the preset distance, generate the three-dimensional coordinates of the target particle on the current height plane where the sum of the Z-axis coordinates of the highest point and the preset distance is located; Within the three-dimensional spatial boundary, the target particle is moved along the target movement direction with a preset step size, the three-dimensional coordinates of the target particle are updated, and the target particle and the existing particles are judged according to preset conditions until all the target particles to be placed are placed. Then, the density is calculated by the Monte Carlo method of solving pi. Selection module: used to select the mass ratio corresponding to the maximum approximate density from the calculated density when configuring solder paste to configure metal particles of different shapes; Preparation module: Used to uniformly mix the prepared mixed metal particles with a preset solvent to obtain solder paste.

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