A method, apparatus and system for soldering a circuit board with controllable solder joint shape

Abstract

The present application relates to the technical field of welding connection, in particular to a kind of circuit board welding method, equipment and system with controllable weld point shape.The method obtains the wet area of pad, effective solder reference volume range and metal content ratio, converts scanned solder paste point cloud into height matrix;By integrating height matrix, the effective pad is screened by obtaining solder paste total volume, and the invalid accumulation outside wet area is deducted to extract effective solder volume;Obtain effective volume proportion, combined with projection coincidence degree, center deviation and edge height distribution, obtain solder paste spreading degree;The volume deviation term of effective solder volume relative to effective solder reference volume range is compared with the spreading loss term formed by solder paste spreading degree, and the source of weld point shape deviation is determined according to the dominant relationship of the two, and welding process adjustment is executed.The present application effectively distinguishes tin supply anomaly and spreading out of control, avoids blind parameter adjustment, and realizes high-precision closed-loop process correction.

Description

Technical Field

[0001] This invention relates to the field of welding connection technology, and specifically to a circuit board welding method, equipment and system with controllable solder joint shape. Background Technology

[0002] In surface mount technology (SMT) of printed circuit boards (PCBs), solder paste printing is often a critical pre-process step for solder joint formation. Solder paste is transferred from a stencil to the pads, and after component placement, it enters a reflow oven. The solder melts at high temperature, wetting, spreading, and cooling between the pads and component terminals to form the solder joint. An ideal solder joint typically needs to meet specific requirements for height, bottom wetting range, edge shrinkage, and connection reliability. Excessive height, insufficient height, eccentric buildup, or edge overflow can all lead to serious defects such as bridging, cold solder joints, or insufficient connection strength.

[0003] Currently, quality control of circuit board soldering processes largely relies on 3D solder paste inspection equipment for interception. Existing detection and control logic typically only extracts the total volume, maximum height, or total area of ​​the printed solder paste and compares it with preset fixed tolerances, using this as the basis for product alarms or release. This approach essentially equates "solder paste printing volume meeting standards" directly with "having a good foundation for solder joint formation." However, in actual mass production, factors such as stencil wear, circuit board alignment deviation, solder paste viscosity drift, and changes in workshop temperature and humidity can cause solder joint shapes to deviate significantly from the target even if the total volume of printed solder paste is within the target range. This can be due to local collapse, severe eccentricity, or a large amount of solder paste overflowing beyond the effective wetting boundary of the pads. Secondly, the causes of abnormal solder joint shapes are usually complex, with volume abnormalities and shape deterioration often coexisting. Existing technologies cannot analyze the core causal relationship of mixed defects. This confusion between the root cause and the causal relationship makes it impossible for the system to output precise process adjustment instructions to the front-end equipment, which can easily lead to incorrect adjustments and even damage other originally normal qualified pads, making it difficult to achieve high-precision and consistent closed-loop process correction. Summary of the Invention

[0004] To address the technical problems of existing PCB soldering quality control methods failing to effectively constrain the three-dimensional morphology of solder paste with the actual wetting and adhesion capacity of the pads, and being unable to accurately distinguish between abnormal solder supply and uncontrolled spread when facing mixed defects, leading to blind process adjustments and easily causing cascading damage, the present invention aims to provide a PCB soldering method, equipment, and system with controllable solder joint shape. The specific technical solution adopted is as follows: In a first aspect, one embodiment of the present invention provides a circuit board soldering method with controllable solder joint shape, the method comprising the following steps: Obtain the wetting area, effective solder reference volume range, and metal content ratio of solder paste for each pad within the same production batch; scan the solder paste point cloud of each pad and convert it into a height matrix; Integrate the height matrix to obtain the total solder paste volume of each pad to filter valid pads; based on the total solder paste volume of each valid pad, the build-up volume outside the wetting area, and the metal content ratio, obtain the effective solder volume of each valid pad; Based on the effective volume of solder, total volume of solder paste, and metal content ratio of effective pads, the effective volume ratio of each effective pad is obtained; based on the overlap between the solder paste projection area and the wetting area of ​​each effective pad, combined with the spatial deviation formed by the deviation of the center position of solder paste accumulation relative to the center position of the pad and the height distribution of the solder paste edge area, and constraining the spatial deviation by the effective volume ratio, the degree of solder paste spread of each effective pad is obtained. The volume deviation of the effective solder volume of each effective pad relative to the effective solder reference volume range is compared with the spreading loss caused by the degree of solder paste spreading. The dominant relationship between the volume deviation and the spreading loss is determined, the source of the solder joint shape deviation of each effective pad is obtained, and the soldering process is adjusted.

[0005] Furthermore, the method for integrating the height matrix to obtain the total solder paste volume of each pad and then filtering out valid pads is as follows: For any pad, integrate and sum the products of the area and height values ​​of each grid in the height matrix corresponding to the pad to obtain the total volume of solder paste for that pad; When the total volume of solder paste is less than or equal to the preset missing volume threshold, the pad is marked as an abnormal pad and an abnormal alarm is triggered, and no further analysis is performed. When the total volume of solder paste exceeds the preset missing volume threshold, the pad is marked as a valid pad.

[0006] Furthermore, the method for obtaining the effective volume of the solder is as follows: For any valid pad, isolated residual meshes located outside the wetted area of ​​the valid pad in the height matrix of the valid pad, as well as meshes extending into or beyond the preset allowable edge stacking range, are collectively determined as invalid edge meshes. The product of the area and height of the invalid edge mesh is integrated and summed to obtain the stacking volume outside the wetted area of ​​the valid pad; The effective solder paste base volume of the effective pad is obtained by subtracting the accumulated volume outside the wetting area from the total volume of solder paste on the effective pad. The effective solder paste volume is obtained by multiplying the effective solder paste base volume by the metal content ratio.

[0007] Furthermore, the method for obtaining the effective volume percentage is as follows: For any valid pad, multiply the total volume of solder paste of the valid pad by the metal content ratio to obtain the total volume of pure solder of the valid pad; Calculate the ratio of the effective solder volume of the effective pad to the total volume of pure solder to obtain the effective volume ratio of the effective pad.

[0008] Furthermore, the method for obtaining the spatial deviation is as follows: For any valid pad, calculate the Euclidean distance between the center position of the solder paste buildup and the center position of the pad, and use it as the offset distance of the valid pad; When the offset distance is within the preset allowable eccentricity range, the center offset of the effective pad is set to 0. When the offset distance is not within the preset allowable eccentricity range, calculate the absolute value of the difference between the offset distance and the nearest boundary value of the preset allowable eccentricity range, divide the absolute value of the difference by the span value of the preset allowable eccentricity range, and obtain the center offset of the effective pad; if the center offset is greater than the preset offset upper limit threshold, then truncate the center offset to the preset offset upper limit threshold. The solder paste edge region of the effective pad is obtained by expanding the contour of the wetted area boundary of the effective pad outward. The target direction interval pointing to the adjacent pad is determined within the solder paste edge region of the effective pad. In the solder paste edge region corresponding to the target direction interval, the grid with the largest height value in the height matrix is ​​extracted as the local high point. When a local high point is within the preset allowable edge stacking range, the edge stacking risk item of the effective pad is set to 0; When a local high point is not located within the preset allowable edge stacking range, the overflow distance of the local high point relative to the boundary of the preset allowable edge stacking range is divided by the preset bridging safety tolerance span to obtain the edge stacking risk item of the effective pad; if the edge stacking risk item is greater than the preset stacking upper limit threshold, the edge stacking risk item is truncated to the preset stacking upper limit threshold. The center offset term is added to the edge stacking risk term to obtain the spatial deviation of the effective pad.

[0009] Furthermore, the method for obtaining the degree of solder paste spread is as follows: For any valid pad, calculate the ratio of the overlapping area of ​​the solder paste projection area and the wetted area of ​​the valid pad to the total area of ​​the wetted area, and use it as the projection overlap term of the valid pad. The ratio of the spatial deviation of the effective pad to the effective volume ratio is negatively correlated and normalized, and used as the attenuation term of the effective pad. The product of the projection overlap term and the attenuation term of the effective pad is taken as the solder paste spread degree of the effective pad.

[0010] Furthermore, the method for obtaining the source of the solder joint shape deviation is as follows: For any valid pad, when the effective volume of solder on the valid pad is within the effective solder reference volume range, the volume deviation term of the valid pad is set to 0; When the effective volume of solder on the effective pad is not within the effective solder reference volume range, the absolute value of the excess is divided by the span value of the effective solder reference volume range to obtain the volume deviation of the effective pad; if the volume deviation is greater than the preset cutoff upper limit, the volume deviation is cut off to the preset cutoff upper limit. Subtract the solder paste spread of the effective pad from the constant 1 to obtain the spread loss term of the effective pad; The difference between the volume deviation term and the spread loss term is used as the numerator, and the sum of the volume deviation term, the spread loss term, and a preset minimum positive number is used as the denominator. The numerator is divided by the denominator to obtain the abnormal source of the valid pad. When the source of the anomaly is greater than the preset direction determination threshold and the volume deviation is greater than the preset volume deviation threshold, the source of the solder joint shape deviation of the effective solder pad is determined to be an abnormal solder paste supply. When the abnormal source is less than a negative preset direction determination threshold and the solder paste spreading degree is less than a preset solder paste spreading degree threshold, the solder joint shape of the effective pad is determined to be deviated from the source as spreading imbalance. When the absolute value of the abnormal source is less than or equal to the preset pointing determination threshold, and the volume deviation is less than or equal to the preset volume deviation threshold and the solder paste spreading degree is greater than or equal to the preset solder paste spreading degree threshold, the source of the solder joint shape deviation of the effective pad is determined to be a reflow compensable deviation. When the absolute value of the abnormal source is less than or equal to the preset pointing determination threshold, and the volume deviation is greater than the preset volume deviation threshold or the solder paste spreading degree is less than the preset solder paste spreading degree threshold, the source of the solder joint shape deviation of the effective pad is determined to be a compound severe abnormal deviation. If the valid pad does not meet any of the above conditions, the source of the deviation of the valid pad's solder joint shape is determined to be a controlled normal fluctuation.

[0011] Furthermore, the method for adjusting the welding process is as follows: The source of solder joint shape deviation for all valid pads on the current circuit board is obtained. When the source of solder joint shape deviation for any valid pad is a compound severe abnormal deviation, an abnormal shutdown prompt is output in real time, the current circuit board is intercepted, and a manual intervention verification and correction command is triggered. When the proportion of valid pads with abnormal solder paste supply to all valid pads is greater than the preset whole board trend threshold, if more than half of the valid pads with abnormal solder paste supply show that the effective solder volume is lower than the lower limit of the effective solder reference volume range, a first printing adjustment command to increase the amount of solder paste transfer is output to the printing equipment and applied to subsequent circuit boards; if more than half of the valid pads with abnormal solder paste supply show that the effective solder volume is higher than the upper limit of the effective solder reference volume range, a second printing adjustment command to decrease the amount of solder paste transfer is output and applied to subsequent circuit boards. When the proportion of the number of valid pads with uneven spreading is greater than the preset whole board trend threshold, an alignment compensation command is output to the printing equipment and applied to subsequent circuit boards. When the proportion of the number of valid pads with unbalanced spreading to all valid pads is less than or equal to the preset whole board trend threshold, a stencil maintenance prompt for correcting the local state is output. Extract the valid pads that are determined to be compensable for reflow deviation, and retrieve the signed excess amount when the volume deviation of the valid pad is generated; if the signed excess amount generally shows an over-excess trend greater than zero, generate a fine-tuning direction to extend the heat preservation time or increase the preheating temperature; if the signed excess amount generally shows a shortage trend less than zero, generate a fine-tuning direction to shorten the heat preservation time or decrease the preheating temperature; and accumulate and statistically analyze the fine-tuning directions among multiple circuit boards being processed continuously. When the number of circuit boards with the same type of fine-tuning direction accumulated reaches a preset number threshold, perform optimization adjustment on the global temperature curve of the reflow equipment, which will be applied to subsequent processing batches.

[0012] Secondly, another embodiment of the present invention provides a circuit board soldering system with controllable solder joint shape, the system comprising: The data acquisition module is used to acquire the wetting area, effective solder reference volume range, and metal content ratio of each pad in the same production batch; scan the solder paste point cloud of each pad and convert it into a height matrix; The solder effective volume acquisition module is used to integrate the height matrix to obtain the total solder paste volume of each pad to filter effective pads; based on the total solder paste volume of each effective pad, the accumulation volume outside the wetting area, and the metal content ratio, the effective solder volume of each effective pad is obtained. The solder paste spreading degree acquisition module is used to obtain the effective volume ratio of each effective pad based on the effective volume of solder, the total volume of solder paste, and the metal content ratio of the effective pads. Based on the overlap between the solder paste projection area and the wetting area of ​​each effective pad, and combined with the spatial deviation formed by the deviation of the center position of the solder paste accumulation relative to the center position of the pad and the height distribution of the solder paste edge area, the effective volume ratio is used to constrain the spatial deviation to obtain the solder paste spreading degree of each effective pad. The soldering process adjustment module is used to compare the volume deviation of the effective solder volume of each effective pad relative to the effective solder reference volume range with the spreading loss caused by the degree of solder paste spreading, determine the dominant relationship between the volume deviation and the spreading loss, obtain the source of the solder joint shape deviation of each effective pad, and adjust the soldering process.

[0013] Thirdly, another embodiment of the present invention provides a circuit board soldering device with controllable solder joint shape. The device includes: a memory, a processor, and a computer program stored in the memory and running on the processor. When the processor executes the computer program, it implements the steps of any of the above methods.

[0014] The present invention has the following beneficial effects: This invention first integrates the height matrix to obtain the total solder paste volume of each pad to filter effective pads. This determines the macroscopic physical quantity of solder paste actually transferred to the circuit board in the current printing process, which helps to promptly intercept serious printing errors caused by complete blockage of the stencil apertures and avoids wasting computing power by bringing invalid empty data into subsequent calculations. To eliminate interference from volatile components and invalid overflow parts that cannot participate in the formation of the target solder joint during reflow soldering, the effective volume of solder for each effective pad is obtained based on the total solder paste volume, the accumulation volume outside the wetting area, and the metal content ratio. This accurately reflects the amount of pure metal that can actually participate in reflow forming and be transformed into a solid solder joint, which helps to ensure that the subsequent volume deviation evaluation has a very high physical authenticity. To comprehensively characterize the three-dimensional formable state of effective solder paste on the pads and avoid ignoring the risk of local collapse or overflow bridging due to simple volume evaluation, the overlap between the solder paste projection area and the wetting area of ​​each effective pad is used as a basis, combined with the position of the solder paste accumulation center relative to the center of the pad. The spatial deviation formed by the deviation of the center position and the height distribution of the solder paste edge area is constrained by the effective volume ratio to obtain the solder paste spreading degree of each effective pad. This accurately reflects the comprehensive physical state of the effective solder being stably supported within the pad wetting boundary, which is helpful for subsequent precise separation of the source of defects, whether it is insufficient supply or positional loss. In order to accurately isolate the most influential root cause from the complex mixed defects, the volume deviation of the effective solder volume of each effective pad relative to the effective solder reference volume range is compared with the spreading loss term formed by the solder paste spreading degree. The dominant relationship between the volume deviation term and the spreading loss term is determined, and the relative strength of the numerical difference indicates the root cause of the evolution of process error. This allows the source of the solder joint shape deviation of each effective pad to be obtained, breaking the limitation of existing technology that confuses volume abnormality with shape deterioration. This enables accurate welding process adjustment and avoids blindly adjusting equipment parameters, which may cause other qualified pads to be damaged. This achieves high-precision and highly consistent closed-loop process correction. Attached Figure Description

[0015] Figure 1 This is a schematic flowchart illustrating a circuit board soldering method with controllable solder joint shape, provided in one embodiment of the present invention. Figure 2 This is a structural diagram of a circuit board welding system with controllable solder joint shape, provided as an embodiment of the present invention. Detailed Implementation

[0016] The following description, in conjunction with the accompanying drawings, details the specific solution of the circuit board welding method, equipment, and system with controllable solder joint shape provided by the present invention.

[0017] Example 1: This invention proposes a circuit board soldering method with controllable solder joint shape. Please refer to [link / reference]. Figure 1 The diagram illustrates a schematic flowchart of a circuit board soldering method with controllable solder joint shape according to an embodiment of the present invention. The method includes the following steps: Step S1: Obtain the wetting area, effective solder reference volume range, and metal content ratio of solder paste for each pad within the same production batch; scan the solder paste point cloud of each pad and convert it into a height matrix.

[0018] Specifically, to eliminate interference from stencil wear between different batches, changes in workshop temperature and humidity, and solder paste viscosity drift, and to ensure the targeted and accurate adjustment of processes, the solder pads within the same production batch are analyzed to ensure that the acquired data truly reflects the current process status. To clarify the physical boundaries that allow for stable reception and spread of the melted solder, the wetting area of ​​each solder pad within the same production batch is obtained by reading the circuit board design documents, serving as a spatial benchmark for distinguishing between effective accumulation and ineffective overflow. By extracting product reliability design specifications or statistical data based on historical qualified solder joint samples, the effective solder reference volume range for each solder pad within the same production batch is obtained, characterizing the pure solder volume required to form the ideal target solder joint after reflow. By consulting the material specifications of the solder paste used or reading the process setting parameters, the metal content ratio of the solder paste is obtained, which can be used to convert the printed solder paste volume into the actual pure solder volume retained after reflow, eliminating volume calculation errors caused by volatile components such as flux.

[0019] Considering that simple two-dimensional area detection cannot reflect the uneven thickness and local collapse of solder paste, in order to accurately extract the three-dimensional spatial distribution characteristics of solder paste on the pads, a 3D laser scanner or 3D solder paste inspection device is used to scan the solder paste point cloud of each pad to obtain a high-precision three-dimensional surface morphology. Then, the point cloud data is denoised to remove outliers caused by reflection or dust. The circuit board surface outside the pad without solder paste is used as the zero-height reference surface fitting benchmark. The coordinates of the denoised point cloud are aligned to the corresponding pad reference coordinate system, and the data is divided into regular grids according to a preset resolution and then converted into height. The height matrix is ​​obtained as follows: a local reference coordinate system is established with the geometric center of each pad as the origin. The pad reference plane is used as the XY plane, which is divided into a two-dimensional regular grid according to the XY axis resolution of the 3D scanning device. The 3D point cloud data traversed by each pad is mapped to the corresponding grid according to the XY coordinates. For grids containing multiple scattered points, the average Z-axis height of the corresponding scattered points is taken as the height value of the corresponding grid. For grids with no scattered points, the height value is assigned to zero. This constructs a height matrix where the row and column positions of each pad correspond to the planar coordinates, and the element values ​​correspond to the solder paste thickness. This eliminates errors caused by circuit board warping and placement tilt, ensuring a precise spatial correspondence between the actual printed shape and the pad reference data, providing a standardized data foundation for subsequent volume calculation and evaluation of spread deviation.

[0020] Step S2: Integrate the height matrix to obtain the total solder paste volume of each pad to filter valid pads; based on the total solder paste volume of each valid pad, the accumulation volume outside the wetting area, and the metal content ratio, obtain the effective solder volume of each valid pad.

[0021] Specifically, considering that a single point cloud data cannot directly quantify the total supply of solder paste, in order to obtain macroscopic volume data that can assess printing quality, the total volume of solder paste for each pad is obtained by integrating the height matrix. This accurately reflects the total physical quantity of solder paste actually transferred to the circuit board during the current printing process. It is known that solder paste loss may occur during circuit board printing due to reasons such as stencil clogging. To avoid wasting computing power and causing deadlocks in the decision logic by including meaningless empty data in subsequent calculations, severe loss states are intercepted and judged based on the total solder paste volume. This filters out valid pads that meet the basic forming threshold, which helps improve the execution efficiency of the algorithm and the effectiveness of the judgment results. To eliminate interference from volatile components of solder paste during reflow soldering and invalid overflow portions that cannot participate in the formation of the target solder joint, and to restore the actual amount of metal participating in the forming, the effective volume of solder for each valid pad is obtained based on the total volume of solder paste for each valid pad, the accumulation volume outside the wetting area, and the metal content ratio. This ensures that the final basic data used for evaluation and adjustment truly matches the state of the solder joint after reflow forming.

[0022] Preferably, in one feasible method of this embodiment, the effective solder pad is obtained as follows: Considering that the height matrix essentially records the solder paste thickness distribution of each tiny region, in order to convert discrete spatial information into a scalar expression of total quantity, for any solder pad, the product of the area and height value of each grid of the height matrix corresponding to the solder pad is integrated and accumulated to obtain the total solder paste volume of the solder pad, accurately reflecting the overall solder paste supply status of the solder pad; Considering that missing prints or extremely low solder are fatal production failures, there is no need to enter into complex shape analysis, therefore, this embodiment sets a preset missing print volume threshold of 10% of the lower limit of the effective solder reference volume range of the solder pad, to ensure that fatal printing defects are intercepted at the first time. The implementer can set the preset missing print volume threshold according to the component type and reliability requirements, which is not limited here. When the total volume of solder paste is less than or equal to the preset missing volume threshold, it indicates that the pad has a serious missing volume or the stencil is completely blocked. In order to prevent defective products from flowing into the next placement process, the pad is marked as an abnormal pad and an abnormal alarm is triggered. No further analysis is performed. When the total volume of solder paste is greater than the preset missing volume threshold, it indicates that the pad has a basic solder paste supply that can support the subsequent three-dimensional morphology analysis. The pad is marked as a valid pad.

[0023] Preferably, in one feasible embodiment, the method for obtaining the effective solder volume is as follows: Considering that solder paste outside the pad wetting boundary is highly unlikely to shrink towards the center of the pad during reflow, but instead forms isolated solder balls or causes bridging short circuits, in order to accurately remove this portion of solder paste that does not contribute to the forming or is even harmful, for any effective pad, isolated residual grids located outside the wetting area of ​​the effective pad in the height matrix of the effective pad, as well as grids extending into or beyond the preset allowable edge accumulation range, are jointly determined as invalid edge grids, thus locking the unusable solder paste distribution area from the spatial source; In this embodiment, the preset allowable edge accumulation range is set to 15% of the upper limit safety distance between adjacent pads, ensuring that it not only accommodates reasonable normal printing tolerances, but also... Strictly define the overflow area with high bridging risk. Implementers can set a preset allowable edge accumulation range based on the density of components on the circuit board and the pin spacing, which is not limited here. It should be noted that the preset allowable edge accumulation range is a ring-shaped tolerance buffer zone formed by taking the physical outer edge contour of the wetted area of ​​the effective pad as a reference and expanding outward along a direction parallel to the surface of the circuit board. In addition, the method for determining isolated residual meshes is as follows: extract the set of continuous non-zero height meshes with the largest area in the height matrix through connected component analysis as the main solder paste. Non-zero meshes that are not connected to the main solder paste and whose shortest Euclidean distance from the main solder paste is greater than the preset scattering threshold (set to 3 times the diagonal size of the mesh in this embodiment, which is not limited here) are determined to be isolated residual meshes. To quantify the proportion of invalid solder paste stripped out, the product of the area and height of the invalid edge mesh is integrated and accumulated to obtain the accumulation volume outside the wetting area of ​​the effective pad, thus achieving accurate measurement of the invalid components. To obtain the solder paste body that is truly within the acceptable range, the total volume of solder paste in the effective pad is subtracted from the accumulation volume outside the wetting area to obtain the effective solder paste base volume of the effective pad. Considering that the effective solder paste base volume still contains a large amount of non-metallic carriers such as flux that will evaporate and disappear during reflow, in order to extract the amount of pure metal that can eventually be converted into solid solder joints, the effective solder paste base volume is multiplied by the metal content ratio to obtain the effective solder volume of the effective pad. Through the above subtraction mechanism and material conversion, the subsequent volume deviation assessment is ensured to have extremely high physical authenticity.

[0024] Step S3: Based on the effective volume of solder, total volume of solder paste, and metal content ratio of the effective pads, obtain the effective volume ratio of each effective pad; based on the overlap between the solder paste projection area and the wetting area of ​​each effective pad, combined with the spatial deviation formed by the deviation of the center position of the solder paste accumulation relative to the center position of the pad and the height distribution of the solder paste edge area, and constrain the spatial deviation by the effective volume ratio, obtain the solder paste spreading degree of each effective pad.

[0025] Specifically, in order to assess the usable proportion that can actually be used for forming from the overall printing status, the structural losses caused by printing overflow or severe scattering are isolated. Then, based on the effective volume of solder, the total volume of solder paste, and the metal content ratio of each effective pad, the effective volume ratio of each effective pad is obtained. This accurately reflects the quality weight of the printed solder paste that is truly within the controllable wetting range of the effective pad, which is beneficial for subsequent measurement of the ability of usable solder to resist spatial morphology degradation. Considering that even if the effective solder paste volume meets the standard, if its spatial distribution deviates significantly from the center of the pad or is concentrated in large quantities at the edge, it can still cause defects such as misalignment or bridging during reflow. Simple volume indicators cannot reflect these defects caused by improper spreading and receiving positions. In order to comprehensively characterize the forming state of solder paste on the pad, the overlap between the solder paste projection area and the wetting area of ​​each effective pad is used as the basis. This is combined with the spatial deviation formed by the deviation of the center position of the solder paste accumulation relative to the center position of the pad and the height distribution of the solder paste edge area. The effective volume ratio is used to constrain the spatial deviation to obtain the degree of solder paste spreading for each effective pad. This accurately reflects the comprehensive physical state of the effective solder being stably received within the pad wetting boundary, which is helpful for subsequent accurate separation of the source of defects, whether it is insufficient supply or location out of control. Among them, the greater the degree of solder paste spreading, the higher the retention rate of the solder paste on the corresponding effective pad, and the more firmly it covers the wetting range, the higher the probability of successfully forming the target solder joint shape after reflow.

[0026] Preferably, in one feasible manner of this embodiment, the method for obtaining the effective volume ratio is as follows: for any effective pad, multiply the total volume of solder paste of the effective pad by the metal content ratio to obtain the total volume of pure solder of the effective pad, accurately restoring the sum of all metal components printed in the effective pad; then, calculate the ratio of the effective volume of solder to the total volume of pure solder to obtain the effective volume ratio of the effective pad.

[0027] Preferably, in one feasible embodiment of this invention, the method for obtaining the spatial offset is as follows: For any valid pad, firstly, the center position of the solder paste accumulation of the valid pad is determined by calculating the geometric center of the coordinates of all grids with height values ​​greater than zero in the height matrix, and the center position of the valid pad is determined by reading the design geometric data of the valid pad; then, the Euclidean distance between the center position of the solder paste accumulation of the valid pad and the center position of the pad is calculated as the offset distance of the valid pad, which accurately reflects the degree of overall printing alignment deviation of the valid pad; wherein, the method for obtaining the Euclidean distance is well known and will not be described in detail. When the offset distance is within the preset allowable eccentricity range, it indicates that the alignment deviation of the effective pad is completely within the surface tension self-correction capability of reflow soldering. In this case, the center offset term of the effective pad is set to 0. When the offset distance is not within the preset allowable eccentricity range, it indicates that the solder paste eccentricity of the effective pad has exceeded the self-correction boundary, which can easily lead to poor wetting on one side. In this case, the absolute value of the difference between the offset distance and the nearest boundary value of the preset allowable eccentricity range is calculated. The absolute value of the difference is divided by the span value of the preset allowable eccentricity range (i.e., the difference between the upper and lower limits of the preset allowable eccentricity range) to obtain the center offset term of the effective pad. Considering that extreme splashing or extreme misalignment of the circuit board may cause abnormal offset distances, To prevent local anomalies from causing weight erratic behavior and masking other key features in subsequent mathematical calculations, if the center offset exceeds a preset offset upper limit threshold, the center offset is truncated to the preset offset upper limit threshold to ensure stable risk assessment output under any extreme conditions. In this embodiment, the preset allowable eccentricity range is set to 10% to 20% of the effective pad width to ensure a balance between printing efficiency and self-centering correction upper limit. Implementers can set the preset allowable eccentricity range according to the placement accuracy of the pick-and-place machine and the component pin size, which is not limited here. The preset offset upper limit threshold is set to 1 to ensure standardized normalization. Implementers can set the preset offset upper limit threshold according to the algorithm weight tolerance, which is not limited here. Furthermore, considering that in addition to overall center offset, abnormal buildup at the edge of the solder paste can easily cause short circuits by flowing towards adjacent pads during reflow melting and collapse, in order to monitor this high-risk overflow collapse trend, the solder paste edge region of the effective pad is first obtained by extending the contour of the wetted area boundary of the effective pad outward (i.e., the set of grids covered by the preset annular width of the outward extension of the outer contour of the wetted area). Then, the target direction interval pointing to adjacent pads within the solder paste edge region of the effective pad (i.e., the dangerous sector most prone to bridging short circuits) is determined by coordinate vector mapping. It should be noted that when there are no adjacent pads around the effective pad or the distance to the nearest adjacent pad is greater than the preset insulation safety distance, the entire solder paste edge region of the effective pad is taken as the target direction interval pointing to adjacent pads. By expanding the search range to the entire circumference to monitor the collapse or splashing of isolated pads and prevent null pointer exceptions in the algorithm calls, this embodiment sets a preset insulation safety distance of 3 times the width of the effective pad to ensure that long-distance pads that are physically impossible to bridge can be safely filtered out, avoiding invalid directional constraints. Implementers can set the preset insulation safety distance according to the design specifications of the circuit board and the thermal collapse flow characteristics of the solder paste, which is not limited here. Finally, in the solder paste edge region corresponding to the target direction interval, the grid with the largest height value in the height matrix is ​​extracted as the local high point to accurately lock the danger point with the largest spillover potential energy. If there are at least two grids with the largest height value, one of them can be selected as the local high point, or the geometric center of these grids can be taken as the equivalent local high point, which is not limited here. When a local high point is within the preset allowable edge stacking range, it indicates that although there is stacking at the edge, it is still within the safe distance isolation zone and will not cause a short circuit. Therefore, the edge stacking risk item of the effective pad is set to 0. When a local high point is not within the preset allowable edge stacking range, it indicates that the high-risk point has exceeded the safety red line and has a strong bridging flow trend. At this time, the overflow distance of the local high point relative to the boundary of the preset allowable edge stacking range (i.e., the shortest vertical Euclidean distance from the geometric center of the grid corresponding to the local high point to the outermost boundary contour line of the preset allowable edge stacking range) is divided by the preset bridging safety tolerance span to obtain the edge stacking risk item of the effective pad, which quantifies the severity of the overflow distance encroaching on the safety boundary. Considering that overflow distance may also generate huge outliers due to abnormal solder spikes, if the edge stacking risk item exceeds the preset stacking upper limit threshold, the edge stacking risk item is truncated to the preset stacking upper limit threshold to avoid a single high point destroying the rationality of the overall evaluation; in this embodiment, the preset bridging safety tolerance span is set to 50% of the distance between the effective pad and the adjacent pad to ensure sufficient rheological redundancy space. Implementers can set the preset bridging safety tolerance span according to the rheological characteristics of the solder paste, which is not limited here; the preset stacking upper limit threshold is set to 1 to ensure that it is at the same scalar level as the center offset item. Implementers can set the preset stacking upper limit threshold according to the algorithm weight tolerance, which is not limited here; In order to comprehensively measure the deviation trend of the overall coordinates and the flow risk of local edges, the center offset term and the edge accumulation risk term are added together to form the spatial deviation of the effective pad.

[0028] Preferably, in one feasible embodiment of this invention, the method for obtaining the degree of solder paste spread is as follows: For any effective pad, calculate the ratio of the overlap area between the solder paste projection area (i.e., the two-dimensional contour area formed by the orthographic projection of the grid with a height greater than zero in the height matrix) and the wetting area to the total area of ​​the wetting area. This ratio is used as the projection overlap term for the effective pad. The larger the projection overlap term, the more fully the solder paste of the effective pad falls on the safe base that can be normally wetted and supported. In order to measure the resistance of available solder to spatial deviation and the rate of quality decay caused by deviation, the ratio of the spatial deviation of the effective pad to the effective volume ratio is negatively correlated and normalized. This ratio is used as the support decay term for the effective pad, accurately reflecting that when the effective solder base is insufficient, the same spatial deviation will cause a more severe collapse in support quality. This embodiment uses... The ratio of the effective pad's spatial deviation to the effective volume percentage is negatively correlated and normalized, where exp is an exponential function with the natural constant as the base, and x is the ratio of the effective pad's spatial deviation to the effective volume percentage. It should be noted that, considering the possibility that the effective volume percentage may be 0 in the case of complete missing printing or extreme scraping, in order to avoid arithmetic overflow or program crash due to a zero denominator, the sum of the effective volume percentage and a preset minimum positive number is used as the denominator. In this embodiment, the preset minimum positive number is set to 0.001 to ensure that the program's strong robustness is maintained without affecting the normal mathematical characteristics. Implementers can set the preset minimum positive number according to the computer's floating-point precision, which is not limited here. In order to integrate the spread base foundation with the attenuation state of spatial deterioration, and then use the product of the projection overlap term and the bearing attenuation term of the effective pad as the solder paste spread degree of the effective pad, a complete physical model of "overlap as the basis and deviation as the weakening" was constructed through multiplicative coupling relationship.

[0029] Step S4: Compare the volume deviation of the effective solder volume of each effective pad relative to the effective solder reference volume range with the spreading loss caused by the degree of solder paste spreading, determine the dominant relationship between the volume deviation and the spreading loss, obtain the source of solder joint shape deviation for each effective pad, and adjust the soldering process accordingly.

[0030] Specifically, considering that the causes of abnormal solder joint shape in actual production are usually complex, with volume abnormalities and shape deterioration often coexisting, it is easy to lead to incorrect process adjustment if the core causal relationship between the two is not analyzed. In order to accurately isolate the most influential root cause from mixed defects, the volume deviation of the effective solder volume of each effective pad relative to the effective solder reference volume range is compared with the spreading loss caused by the degree of solder paste spreading. The dominant relationship between the volume deviation and the spreading loss is determined, and the relative strength of the numerical difference indicates the root cause of the evolution of process error. In this way, the source of solder joint shape deviation of each effective pad can be obtained, and accurate soldering process adjustment can be carried out. This avoids blindly adjusting equipment parameters, which may cause other qualified pads to be damaged as a result, and achieves closed-loop high-precision process correction.

[0031] Preferably, in one feasible embodiment of this invention, the method for obtaining the source of solder joint shape deviation is as follows: For any valid solder pad, when the effective volume of solder on the valid solder pad is within the effective solder reference volume range, it indicates that the metal supply of solder paste on the valid solder pad fully meets the design forming requirements, and at this time, the volume deviation of the valid solder pad is set to 0; when the effective volume of solder on the valid solder pad is not within the effective solder reference volume range, it indicates that the solder supply of the valid solder pad has a substantial shortage or redundancy. In order to quantify the relative severity of this absolute error, the absolute value of the excess amount (i.e., the amount of solder on the valid solder pad) is set to 0. The volume deviation term of the effective pad is obtained by dividing the absolute value of the difference between the effective volume and the nearest boundary value of the effective solder reference volume range by the span value of the effective solder reference volume range (i.e., the difference between the upper and lower limits of the effective solder reference volume range). Considering that a very small number of severe spikes or giant solder lumps can cause the excess to be amplified infinitely and destroy the sensitive range of subsequent judgment logic, if the volume deviation term is greater than the preset cutoff upper limit, the volume deviation term is truncated to the preset cutoff upper limit, forcibly confining extreme anomalies within a controllable analysis range. In this embodiment, the preset cutoff upper limit is set to 1 to ensure that the volume deviation term and the subsequent spread loss term are at the same level. Within the normalized dimension range, to avoid a single extreme value monopolizing the judgment result, implementers can set a preset cutoff upper limit based on the maximum allowable abnormal peak limit, which is not limited here; Considering that solder paste spreading degree characterizes the probability of conforming to the forming safety boundary, in order to transform it into a defect metric comparable to volume deviation, the solder paste spreading degree of the effective pad is subtracted from a constant of 1 to obtain the spreading loss term of the effective pad, completing the logical reversal from "positive quality" to "reverse loss". To further construct a standardized dominant factor adjudicator, the difference between the volume deviation term and the spreading loss term is used as the numerator, and the sum of the volume deviation term, the spreading loss term, and a preset minimum positive number (also preset to 0.001 to avoid calculation crashes caused by both numerator and denominator being zero under ideal printing conditions) is used as the denominator. The numerator is then divided by the denominator to obtain the source of the anomaly of the effective pad, accurately reflecting whether the defect of the effective pad is dominated by "solder supply" or by "positional misalignment" tilt, which is beneficial. This allows for the subsequent invocation of different types of control methods. Simultaneously, considering that volume deviation and solder paste spreading must exceed tolerance thresholds to have intervention value, and to prevent the process equipment from frequently adjusting due to minor fluctuations, this embodiment sets a preset direction judgment threshold of 0.1 to ensure that samples with an absolute advantage in dominant factors are selected. The implementer can set the preset direction judgment threshold according to the sensitivity of process correction, which is not limited here. A preset volume deviation threshold of 0.2 is set to ensure that normal volume fluctuations within a reasonable range are allowed. The implementer can set the preset volume deviation threshold according to the component reliability tolerance, which is not limited here. A preset solder paste spreading threshold of 0.85 is set to ensure that minor edge deformation interference is filtered out. The implementer can set the preset solder paste spreading threshold according to the repair capability of reflow surface tension, which is not limited here. When the source of the anomaly is greater than the preset direction judgment threshold, and the volume deviation is greater than the preset volume deviation threshold, it indicates that the volume deviation has a dominant weight and has exceeded the process baseline. In this case, the source of the solder joint shape deviation of the effective pad is determined to be an abnormality in solder paste supply, and the problem is directly locked onto the printing press's printing omissions, squeegee pressure, or stencil thickness. When the source of the anomaly is less than the negative preset direction judgment threshold, and the solder paste spreading degree is less than the preset solder paste spreading degree threshold, it indicates that the solder supply is basically normal, but the solder paste is severely biased or overflows into the danger zone. In this case, the source of the solder joint shape deviation of the effective pad is determined to be spreading imbalance, and the focus of the investigation shifts to the positioning accuracy of the circuit board or local mesh contamination. When the absolute value of the source of the anomaly is less than or equal to the preset direction judgment threshold, and the volume deviation is less than or equal to the preset volume deviation threshold, and the solder paste spreading degree is greater than or equal to the preset solder paste spreading degree threshold, it indicates that the two... If neither of these conditions results in overwhelming damage and the absolute deviation is minimal, the source of the solder joint shape deviation for the effective pad is determined to be a reflow-compensable deviation, and the correction task is safely transferred to the high-temperature self-correction capability of the reflow oven. When the absolute value of the abnormal source is less than or equal to the preset direction judgment threshold, and the volume deviation is greater than the preset volume deviation threshold or the solder paste spreading degree is less than the preset solder paste spreading degree threshold, it indicates that both volume abnormality and uncontrolled spreading defects occur simultaneously and are of equal severity, and cannot be recovered by compensation in a single process. In this case, the source of the solder joint shape deviation for the effective pad is determined to be a composite severe abnormal deviation, avoiding the issuance of erroneous single adjustment instructions that could further worsen the defect. If the effective pad does not meet any of the above conditions, it indicates that the effective pad does not have a significant defect with a clear bias. In this case, the source of the solder joint shape deviation for the effective pad is determined to be a controlled normal fluctuation, and it is directly released into the subsequent process.

[0032] Preferably, in one feasible way of this embodiment, the method for adjusting the soldering process is as follows: In order to avoid command conflicts caused by independent adjustment of a single solder pad and to achieve macroscopic process control, the source of the solder joint shape deviation of all effective solder pads on the current circuit board is obtained. When the source of the solder joint shape deviation of any effective solder pad is a compound severe abnormal deviation, it indicates that the solder supply and spreading acceptance status of the area have been severely collapsed and cannot be compensated by a single process. In order to prevent defective products from flowing into the subsequent surface mount process and to avoid the automatic closed-loop adjustment system from falling into the oscillation deadlock of conflict parameter adjustment, an abnormal shutdown prompt is output in real time, the current circuit board is intercepted, and a manual intervention verification and correction instruction is triggered, prompting the operator to conduct a comprehensive investigation of systemic physical faults such as stencil damage, solder paste drying and severe deformation of the circuit board. When the proportion of valid pads with abnormal solder paste supply exceeds the preset overall board trend threshold, it indicates a systematic deviation in solder supply from the current printing parameters or stencil status. If more than half of the valid pads with abnormal solder paste supply exhibit a solder volume below the lower limit of the effective solder volume reference range, it indicates a solder shortage across the entire board or a large area. To compensate for this defect, a first printing adjustment command is sent to the printing equipment to increase solder paste transfer, affecting subsequent circuit boards. This could include prompting for increased squeegee pressure or optimized demolding speed. If the solder paste supply is abnormal... If more than half of the effective solder pads are abnormal, it indicates that the effective solder volume is higher than the upper limit of the effective solder reference volume range, indicating a serious oversupply of solder. In order to suppress the risk of short circuit due to solder bridging, a second printing adjustment command is output to reduce the amount of solder paste transferred, which is applied to subsequent circuit boards, such as prompting to reduce the printing speed or clean the bottom of the stencil. In this embodiment, the preset whole board trend threshold is set to 0.6 to ensure that global parameter adjustment is triggered only when systematic deviation is dominant, avoiding misadjustment caused by fluctuations in individual solder pads. Implementers can set the preset whole board trend threshold according to the production line yield requirements and equipment stability, which is not limited here. When the proportion of valid pads with uneven spreading is greater than the preset whole board trend threshold, it indicates that the main cause of the defect is the systematic translational misalignment of the overall coordinates. In order to eliminate the overall alignment deviation, an alignment compensation command is output to the printing equipment, which is applied to the subsequent circuit boards, triggering the machine vision system to recalibrate or correct the clamping position of the circuit boards. When the proportion of valid pads with uneven spreading is less than or equal to the preset whole board trend threshold, it indicates that the overall alignment is acceptable, but only individual or local areas have collapsed, overflowed or blocked mesh. In order to restore the forming state of the local mesh, a stencil maintenance prompt is output to correct the local state, triggering an automatic wiping mechanism or manual intervention to clean stubborn solder paste residue. To fully utilize thermorheological properties for flexible correction without frequently interfering with the front-end printing equipment, the effective pads that can be compensated for by reflow are extracted, and the excess amount with the sign at the time of volume deviation of the effective pad is retrieved as the basis for determining the reflow heat requirement. If the excess amount with the sign generally shows an over-excess trend greater than zero, it indicates that the local heat capacity of the solder paste has increased, requiring additional heat energy to ensure complete melting and full spread of the solder, thus generating a fine-tuning direction to extend the holding time or increase the preheating temperature. If the excess amount with the sign generally shows a shortage trend less than zero, it indicates that the local heat capacity of the solder paste has decreased, requiring additional heat energy to prevent premature evaporation of flux or high temperature damage. Excessive oxidation can lead to fine-tuning of the circuit board's orientation, resulting in shorter holding time or lower preheating temperature. To filter out random fluctuations in the circuit board's orientation and to accumulate and statistically analyze these fine-tuning orientations across multiple circuit boards being processed consecutively, thus preventing lag or excessive oscillations in single-board adjustments due to the high thermal inertia of the reflow oven, when the number of circuit boards with the same fine-tuning orientation reaches a preset threshold, it indicates that the small tolerance is not a random fluctuation but has evolved into a stable, systematic shift trend. To proactively intercept this trend without disrupting production capacity, the global temperature curve of the reflow equipment is optimized and adjusted at this point, affecting subsequent batches and eliminating potential problems at their inception. In this embodiment, a preset threshold of 6 is set to ensure that the true trend is captured in the early stages of the thermal fluctuation cycle and that a sufficient sample size is maintained. Implementers can set the preset threshold based on the temperature control response time of the reflow oven's temperature zone; this is not limited here.

[0033] In summary, this embodiment obtains the wetting area of ​​the solder pad, the effective solder reference volume range, and the metal content ratio, and converts the scanned solder paste point cloud into a height matrix. By integrating the height matrix, the total solder paste volume is obtained, effective solder pads are screened, and invalid accumulation outside the wetting area is subtracted to extract the effective solder volume. The effective volume ratio is obtained, and combined with projection overlap, center deviation, and edge height distribution, the solder paste spreading degree is obtained. The volume deviation term of the effective solder volume relative to the effective solder reference volume range is compared with the spreading loss term formed by the solder paste spreading degree. Based on the dominant relationship between the two, the source of solder joint shape deviation is determined, and soldering process adjustments are performed. This invention effectively distinguishes between abnormal solder supply and uncontrolled spreading, avoids blind parameter adjustments, and achieves high-precision closed-loop process correction.

[0034] Example 2: This invention also proposes a circuit board soldering system with controllable solder joint shape; please refer to [link to relevant documentation]. Figure 2 The diagram illustrates a circuit board welding system with controllable solder joint shape according to an embodiment of the present invention. The system includes: a data acquisition module 10, a solder effective volume acquisition module 20, a solder paste spreading degree acquisition module 30, and a welding process adjustment module 40.

[0035] The data acquisition module 10 is used to acquire the wetting area, effective solder reference volume range, and metal content ratio of each pad in the same production batch; scan the solder paste point cloud of each pad and convert it into a height matrix; The solder effective volume acquisition module 20 is used to integrate the height matrix to obtain the total solder paste volume of each pad to filter effective pads; based on the total solder paste volume of each effective pad, the accumulation volume outside the wetting area and the metal content ratio, the effective solder volume of each effective pad is obtained. The solder paste spreading degree acquisition module 30 is used to obtain the effective volume ratio of each effective pad based on the effective volume of solder, the total volume of solder paste, and the metal content ratio of the effective pads; based on the overlap between the solder paste projection area and the wetting area of ​​each effective pad, combined with the spatial deviation formed by the deviation of the center position of the solder paste accumulation relative to the center position of the pad and the height distribution of the solder paste edge area, and constraining the spatial deviation by the effective volume ratio, the solder paste spreading degree of each effective pad is obtained. The welding process adjustment module 40 is used to compare the volume deviation of the effective solder volume of each effective pad relative to the effective solder reference volume range with the spreading loss caused by the degree of solder paste spreading, determine the dominant relationship between the volume deviation and the spreading loss, obtain the source of the solder joint shape deviation of each effective pad, and perform welding process adjustment.

[0036] It should be noted that the circuit board welding system with controllable solder joint shape provided in the above embodiments and the circuit board welding method with controllable solder joint shape belong to the same concept. The specific implementation process can be found in the method embodiments, and will not be repeated here.

[0037] Example 3: This invention also proposes a circuit board soldering device with controllable solder joint shape. The device includes a memory and a processor. The memory stores executable program code, and the processor calls and executes the executable program code to perform the circuit board soldering method with controllable solder joint shape provided by this invention. Specifically, the device can be a chip, component, or module. The chip may include a connected processor and memory; the memory stores instructions, and when the processor calls and executes the instructions, the chip can perform the circuit board soldering method with controllable solder joint shape provided in the above embodiments.

Claims

1. A circuit board soldering method with controllable solder joint shape, characterized in that, The method includes the following steps: Obtain the wetting area, effective solder reference volume range, and metal content ratio of solder paste for each pad within the same production batch; scan the solder paste point cloud of each pad and convert it into a height matrix; Integrate the height matrix to obtain the total solder paste volume of each pad to filter valid pads; based on the total solder paste volume of each valid pad, the build-up volume outside the wetting area, and the metal content ratio, obtain the effective solder volume of each valid pad; Based on the effective volume of solder, total volume of solder paste, and metal content ratio of effective pads, the effective volume ratio of each effective pad is obtained; based on the overlap between the solder paste projection area and the wetting area of ​​each effective pad, combined with the spatial deviation formed by the deviation of the center position of solder paste accumulation relative to the center position of the pad and the height distribution of the solder paste edge area, and constraining the spatial deviation by the effective volume ratio, the degree of solder paste spread of each effective pad is obtained. The volume deviation of the effective solder volume of each effective pad relative to the effective solder reference volume range is compared with the spreading loss caused by the degree of solder paste spreading. The dominant relationship between the volume deviation and the spreading loss is determined, the source of the solder joint shape deviation of each effective pad is obtained, and the soldering process is adjusted.

2. The circuit board soldering method with controllable solder joint shape as described in claim 1, characterized in that, The method for integrating the height matrix to obtain the total solder paste volume of each pad and then filtering out valid pads is as follows: For any pad, integrate and sum the products of the area and height values ​​of each grid in the height matrix corresponding to the pad to obtain the total volume of solder paste for that pad; When the total volume of solder paste is less than or equal to the preset missing volume threshold, the pad is marked as an abnormal pad and an abnormal alarm is triggered, and no further analysis is performed. When the total volume of solder paste exceeds the preset missing volume threshold, the pad is marked as a valid pad.

3. The circuit board soldering method with controllable solder joint shape as described in claim 1, characterized in that, The method for obtaining the effective volume of the solder is as follows: For any valid pad, isolated residual meshes located outside the wetted area of ​​the valid pad in the height matrix of the valid pad, as well as meshes extending into or beyond the preset allowable edge stacking range, are collectively determined as invalid edge meshes. The product of the area and height of the invalid edge mesh is integrated and summed to obtain the stacking volume outside the wetted area of ​​the valid pad; The effective solder paste base volume of the effective pad is obtained by subtracting the accumulated volume outside the wetting area from the total volume of solder paste on the effective pad. The effective solder paste volume is obtained by multiplying the effective solder paste base volume by the metal content ratio.

4. The circuit board soldering method with controllable solder joint shape as described in claim 1, characterized in that, The method for obtaining the effective volume percentage is as follows: For any valid pad, multiply the total volume of solder paste of the valid pad by the metal content ratio to obtain the total volume of pure solder of the valid pad; Calculate the ratio of the effective solder volume of the effective pad to the total volume of pure solder to obtain the effective volume ratio of the effective pad.

5. The circuit board soldering method with controllable solder joint shape as described in claim 1, characterized in that, The method for obtaining the spatial deviation is as follows: For any valid pad, calculate the Euclidean distance between the center position of the solder paste buildup and the center position of the pad, and use it as the offset distance of the valid pad; When the offset distance is within the preset allowable eccentricity range, the center offset of the effective pad is set to 0. When the offset distance is not within the preset allowable eccentricity range, calculate the absolute value of the difference between the offset distance and the nearest boundary value of the preset allowable eccentricity range, divide the absolute value of the difference by the span value of the preset allowable eccentricity range, and obtain the center offset of the effective pad. If the center offset is greater than the preset offset upper limit threshold, the center offset will be truncated to the preset offset upper limit threshold. The solder paste edge region of the effective pad is obtained by expanding the contour of the wetted area boundary of the effective pad outward. The target direction interval pointing to the adjacent pad is determined within the solder paste edge region of the effective pad. In the solder paste edge region corresponding to the target direction interval, the grid with the largest height value in the height matrix is ​​extracted as the local high point. When a local high point is within the preset allowable edge stacking range, the edge stacking risk item of the effective pad is set to 0; When a local high point is not located within the preset allowable edge stacking range, the overflow distance of the local high point relative to the boundary of the preset allowable edge stacking range is divided by the preset bridging safety tolerance span to obtain the edge stacking risk item of the effective pad. If the edge stacking risk item is greater than the preset stacking upper limit threshold, then the edge stacking risk item will be truncated to the preset stacking upper limit threshold. The center offset term is added to the edge stacking risk term to obtain the spatial deviation of the effective pad.

6. The circuit board soldering method with controllable solder joint shape as described in claim 1, characterized in that, The method for obtaining the degree of solder paste spread is as follows: For any valid pad, calculate the ratio of the overlapping area of ​​the solder paste projection area and the wetted area of ​​the valid pad to the total area of ​​the wetted area, and use it as the projection overlap term of the valid pad. The ratio of the spatial deviation of the effective pad to the effective volume ratio is negatively correlated and normalized, and used as the attenuation term of the effective pad. The product of the projection overlap term and the attenuation term of the effective pad is taken as the solder paste spread degree of the effective pad.

7. The circuit board soldering method with controllable solder joint shape as described in claim 5, characterized in that, The method for obtaining the source of the deviation in solder joint shape is as follows: For any valid pad, when the effective volume of solder on the valid pad is within the effective solder reference volume range, the volume deviation term of the valid pad is set to 0; When the effective volume of solder on the effective pad is not within the effective solder reference volume range, the absolute value of the excess is divided by the span value of the effective solder reference volume range to obtain the volume deviation of the effective pad. If the volume deviation exceeds the preset truncation limit, the volume deviation will be truncated to the preset truncation limit. Subtract the solder paste spread of the effective pad from the constant 1 to obtain the spread loss term of the effective pad; The difference between the volume deviation term and the spread loss term is used as the numerator, and the sum of the volume deviation term, the spread loss term, and a preset minimum positive number is used as the denominator. The numerator is divided by the denominator to obtain the abnormal source of the valid pad. When the source of the anomaly is greater than the preset direction determination threshold and the volume deviation is greater than the preset volume deviation threshold, the source of the solder joint shape deviation of the effective solder pad is determined to be an abnormal solder paste supply. When the abnormal source is less than a negative preset direction determination threshold and the solder paste spreading degree is less than a preset solder paste spreading degree threshold, the solder joint shape of the effective pad is determined to be deviated from the source as spreading imbalance. When the absolute value of the abnormal source is less than or equal to the preset pointing determination threshold, and the volume deviation is less than or equal to the preset volume deviation threshold and the solder paste spreading degree is greater than or equal to the preset solder paste spreading degree threshold, the source of the solder joint shape deviation of the effective pad is determined to be a reflow compensable deviation. When the absolute value of the abnormal source is less than or equal to the preset pointing determination threshold, and the volume deviation is greater than the preset volume deviation threshold or the solder paste spreading degree is less than the preset solder paste spreading degree threshold, the source of the solder joint shape deviation of the effective pad is determined to be a compound severe abnormal deviation. If the valid pad does not meet any of the above conditions, the source of the deviation of the valid pad's solder joint shape is determined to be a controlled normal fluctuation.

8. The circuit board soldering method with controllable solder joint shape as described in claim 7, characterized in that, The method for adjusting the welding process is as follows: The source of solder joint shape deviation for all valid pads on the current circuit board is obtained. When the source of solder joint shape deviation for any valid pad is a compound severe abnormal deviation, an abnormal shutdown prompt is output in real time, the current circuit board is intercepted, and a manual intervention verification and correction command is triggered. When the proportion of valid pads with abnormal solder paste supply to all valid pads is greater than the preset whole board trend threshold, if more than half of the valid pads with abnormal solder paste supply show that the effective solder volume is lower than the lower limit of the effective solder reference volume range, a first printing adjustment command to increase the amount of solder paste transfer is output to the printing equipment and applied to subsequent circuit boards; if more than half of the valid pads with abnormal solder paste supply show that the effective solder volume is higher than the upper limit of the effective solder reference volume range, a second printing adjustment command to decrease the amount of solder paste transfer is output and applied to subsequent circuit boards. When the proportion of the number of valid pads with uneven spreading is greater than the preset whole board trend threshold, an alignment compensation command is output to the printing equipment and applied to subsequent circuit boards. When the proportion of the number of valid pads with unbalanced spreading to all valid pads is less than or equal to the preset whole board trend threshold, a stencil maintenance prompt for correcting the local state is output. Extract the valid pads that are determined to be able to compensate for the deviation by reflow, and retrieve the signed excess amount when the volume deviation of the valid pad is generated; if the overall signed excess amount shows an over-excess trend greater than zero, then generate a fine-tuning direction to extend the heat preservation time or increase the preheating temperature. If the total amount of the marked excess is less than zero, a fine-tuning instruction will be generated to shorten the heat preservation time or reduce the preheating temperature. The fine-tuning direction is accumulated and statistically analyzed among multiple circuit boards being processed continuously. When the number of circuit boards with the same fine-tuning direction reaches a preset threshold, the global temperature curve of the reflow equipment is optimized and adjusted, which is then applied to subsequent processing batches.

9. A circuit board soldering system with controllable solder joint shape, characterized in that, The system includes: The data acquisition module is used to acquire the wetting area, effective solder reference volume range, and metal content ratio of each pad in the same production batch; scan the solder paste point cloud of each pad and convert it into a height matrix; The solder effective volume acquisition module is used to integrate the height matrix to obtain the total solder paste volume of each pad to filter effective pads; based on the total solder paste volume of each effective pad, the accumulation volume outside the wetting area, and the metal content ratio, the effective solder volume of each effective pad is obtained. The solder paste spreading degree acquisition module is used to obtain the effective volume ratio of each effective pad based on the effective volume of solder, the total volume of solder paste, and the metal content ratio of the effective pads. Based on the overlap between the solder paste projection area and the wetting area of ​​each effective pad, and combined with the spatial deviation formed by the deviation of the center position of the solder paste accumulation relative to the center position of the pad and the height distribution of the solder paste edge area, the effective volume ratio is used to constrain the spatial deviation to obtain the solder paste spreading degree of each effective pad. The soldering process adjustment module is used to compare the volume deviation of the effective solder volume of each effective pad relative to the effective solder reference volume range with the spreading loss caused by the degree of solder paste spreading, determine the dominant relationship between the volume deviation and the spreading loss, obtain the source of the solder joint shape deviation of each effective pad, and adjust the soldering process.

10. A circuit board soldering device with controllable solder joint shape, comprising a memory, a processor, and a computer program stored in the memory and running on the processor, characterized in that, When the processor executes the computer program, it implements the steps of the circuit board soldering method with controllable solder joint shape as described in any one of claims 1-8.

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