PCBA patch offset intelligent correction method and system

Abstract

The present application relates to the technical field of offset correction, and specifically discloses a PCBA patch offset intelligent correction method and system, comprising the following steps: step S1: obtaining a set of patch component pad coordinate points, and pre-calibrating a holding torque threshold value thereof; step S2: setting a plurality of collection points in a reflow soldering furnace, and collecting control parameters such as real-time collection of point coordinates, temperature, wind speed, wind direction, etc., and accordingly constructing a spatial distribution model of the furnace heat field and wind field; step S3: dividing the component pads into two pad groups, obtaining the center temperature and temperature change rate of each pad group based on the heat field model, and calculating the surface tension deflection torque caused by the temperature difference between the two ends; combining the wind speed and wind direction of the corresponding area obtained by the wind field model, calculating the aerodynamic deflection torque, and vector synthesizing to obtain the total offset driving torque; and step S4: comparing the total offset driving torque with the preset threshold value, judging whether the component is a risk component, and if so, generating a compensation value parameter set.

Description

Technical Field

[0001] This invention relates to the field of offset correction technology, specifically to a method and system for intelligent correction of PCBA patch offset. Background Technology

[0002] In the PCBA surface mount technology (SMT) manufacturing field, reflow soldering is the core step that determines the component soldering accuracy. However, the existing reflow soldering process has multiple technical bottlenecks, which can easily cause component misalignment and seriously affect product yield.

[0003] In existing technologies, during reflow soldering, uncontrolled preheating rates and uneven temperature distribution in different zones can lead to thermal imbalance at both ends of components, causing the surface tension of the molten solder to become disordered. Under the influence of this unbalanced tension, components are pulled at an angle. Improper hot air speed adjustment, such as excessively high air speeds, can directly blow away lightweight components, causing the entire batch of components to shift in the same direction. Furthermore, improper control of the cooling rate can cause PCB warping and deformation, further amplifying component shift. These process defects overlap, resulting in a systematic and batch-wide shift problem.

[0004] In addition, existing calibration methods mostly rely on manual adjustment after visual inspection, which is not only inefficient but also unable to accurately trace the root cause of the offset and make it difficult to achieve dynamic compensation. Although some offline detection equipment can identify the offset, it lacks real-time linkage with the reflow soldering equipment and cannot be corrected in time during the process, making it difficult to fundamentally solve the offset problem. Furthermore, traditional process parameter adjustments lack data support and are difficult to adapt to complex and ever-changing processing scenarios. Summary of the Invention

[0005] The purpose of this invention is to provide a method and system for intelligent correction of PCBA patch offset, thereby solving the above-mentioned technical problems.

[0006] The objective of this invention can be achieved through the following technical solutions: A method for intelligent correction of PCBA surface mount offset includes the following steps: Step S1: Obtain the set of pad coordinate points of the surface mount component and pre-calibrate the holding torque threshold of the surface mount component; Step S2: Select several sampling points in the reflow oven. When the surface mount component starts reflow soldering, collect the control parameters at each sampling point in real time. The control parameters include the coordinates of the sampling point, temperature, wind speed and wind direction. And establish the spatial distribution of the thermal field and the spatial distribution of the wind field based on the coordinates of each sampling point and the control parameters. Step S3: Divide all the pads of the surface mount component into two pad groups. For any pad group, obtain the center temperature and center temperature change rate of the pad group based on the thermal field spatial distribution. According to the center temperature and center temperature change rate of the two pad groups, obtain the surface tension deflection torque at both ends of the pad. And according to the wind field spatial distribution, obtain the wind speed and wind direction at the pad group, and obtain the aerodynamic deflection torque. Vector synthesize the surface tension deflection torque and the aerodynamic deflection torque to obtain the total offset driving torque. Step S4: Compare the total offset driving torque with the holding torque threshold to determine whether the patch element is a risky element; if the patch element is a risky element, generate a set of compensation value parameters for the patch element.

[0007] As a further aspect of the present invention: the process of obtaining the pad coordinates includes: Choose any point on the PCBA board as the origin, take the plane of the PCBA board as the XY axis plane, and take the direction perpendicular to the PCBA board as the Z axis to establish a coordinate system; obtain the coordinates of the center points of each pad corresponding to the surface mount component in the coordinate system to obtain the pad coordinate point set of the surface mount component.

[0008] As a further aspect of the present invention: the calibration process of the holding torque threshold includes: For any pad, obtain the wettable perimeter of the pad, multiply the preset solder surface tension coefficient by the wettable perimeter to obtain the initial wetting force value; according to the preset wetting angle of the surface mount element on the pad, project the initial wetting force value into the normal direction perpendicular to the pad to obtain the maximum normal holding force of the pad; obtain the distance between the centroid of the surface mount element and the geometric center point of the pad, and cross-multiply the maximum normal holding force with the distance to obtain the holding torque of the pad; vector sum the holding torques of each pad to obtain the holding torque threshold of the surface mount element.

[0009] As a further aspect of the present invention: the process of establishing the spatial distribution of the thermal field includes: Using the coordinate system as a reference, the temperature at each sampling point in the reflow oven is interpolated by planar gridding according to the coordinates of each sampling point; and according to the speed at which the PCBA board moves longitudinally along the furnace chamber of the reflow oven and the sampling timestamp corresponding to the temperature at the sampling point, the temperatures collected at different sampling timestamps are spatiotemporally aligned in the coordinate system to obtain the spatial distribution of the thermal field.

[0010] As a further aspect of the present invention: the process of establishing the spatial distribution of the wind field includes: Using the coordinate system as a reference, the equidistant two-dimensional grid is reused to project the wind speed and direction of each collection point in the reflow oven onto the equidistant two-dimensional grid according to the coordinates of each collection point relative to the XY axis plane of the coordinate system. For any grid node, a search range with a preset radius is defined with the grid node as the center. Collection points falling within the search range are selected, and the wind speed and direction within the search range are interpolated using the inverse distance weighting method. Based on the speed at which the PCBA board moves longitudinally along the furnace of the reflow oven and the collection timestamp of the collection point, the wind speed and direction at different collection timestamps are spatiotemporally aligned on the coordinate system to obtain the spatial distribution of the wind field.

[0011] As a further aspect of the present invention: the process of obtaining the center temperature and center temperature change rate of the pad group based on the aforementioned thermal field spatial distribution includes: Obtain the coordinates of the geometric center of the pad group in the coordinate system, and denot them as the center coordinates of the pad group; in the equally spaced two-dimensional grid of the thermal field spatial distribution, take the center coordinates of the group as the target point, determine all a number of grid nodes within a preset target radius around the target point, obtain the average temperature of all grid nodes, and obtain the center temperature of the pad group; obtain the temperature of each grid node at the first n acquisition timestamps, perform a lookup calculation on each temperature to obtain the temperature change rate of the grid node, and obtain the average temperature change rate of all grid nodes to obtain the center temperature change rate.

[0012] As a further aspect of the present invention: the process of obtaining the surface tension deflection torque at both ends of the pad includes: The system is divided into a first pad group and a second pad group along a preset component offset sensitive axis. The difference between the center temperatures of the first pad group and the second pad group is obtained and recorded as the average temperature difference between the pad groups. The difference between the center temperature change rate of the first pad group and the center temperature change rate of the second pad group is also obtained and recorded as the average temperature change rate difference between the pad groups. The average temperature difference and the average temperature change rate difference are input into a preset solder wetting characteristic data table. The solder wetting characteristic data table uses the average temperature difference and the average temperature change rate as indexes to obtain the solder wetting characteristics of the first pad group and the second pad group respectively, achieving the preset... The required time for the peak wetting force is determined, and the wetting force imbalance generated by the first pad group and the second pad group during the melt wetting process is obtained respectively. The spatial distance between the geometric center point of the first pad group and the geometric center point of the second pad group is obtained. The wetting force imbalance is multiplied by the spatial distance to obtain the magnitude of the surface tension deflection torque. The direction from the geometric center point of the first pad group to the geometric center point of the second pad group is recorded as the direction of the surface tension deflection torque. The surface tension deflection torque is obtained based on the magnitude and direction of the surface tension deflection torque.

[0013] This application also provides a PCBA surface mount offset intelligent correction system, including: Data preprocessing module: Obtains the set of pad coordinate points of the surface mount component and pre-calibrates the holding torque threshold of the surface mount component; Control parameter analysis module: Several acquisition points are selected in the reflow oven. When the surface mount component starts reflow soldering, the control parameters at each acquisition point are acquired in real time. The control parameters include the coordinates of the acquisition point, temperature, wind speed and wind direction; and the spatial distribution of the thermal field and the spatial distribution of the wind field are established based on the coordinates of each acquisition point and the control parameters. Offset Analysis Module: Divides all pads of the surface mount component into two pad groups. For any pad group, the center temperature and center temperature change rate of the pad group are obtained based on the thermal field spatial distribution. The surface tension deflection torque at both ends of the pads is obtained based on the center temperature and center temperature change rate of the two pad groups. The wind speed and wind direction at the pad group are obtained based on the wind field spatial distribution, and the aerodynamic deflection torque is obtained. The surface tension deflection torque and the aerodynamic deflection torque are vectorially synthesized to obtain the total offset driving torque. Correction module: compares the total offset driving torque with the holding torque threshold to determine whether the patch element is a risky element; if the patch element is a risky element, it generates a set of compensation value parameters for the patch element.

[0014] The beneficial effects of this invention are as follows: This invention establishes a coordinate system to map the furnace temperature field and air field into an interpolable spatial distribution, using a group of solder pads instead of a single solder pad for heat analysis, adapting to all types of components from two-terminal to array packages; it also introduces a solder wetting characteristic data table, directly querying the wetting force imbalance and time difference from the temperature difference and temperature change rate difference between solder pad groups, quantifying the thermally induced surface tension deflection torque; it calculates the component's windward aerodynamic deflection torque and vector synthesizes it with the thermally induced torque to obtain the total offset driving torque during the solder melting stage; furthermore, it uses the board surface temperature distribution combined with the thermal expansion coefficient of each layer of material to calculate layered thermal stress, extracting the dynamic warpage displacement field and converting it into… The offset amplification factor corrects the warp coupling of the driving torque, ensuring that the predicted offset value closely matches the actual process state. Based on a multivariate regression mapping database, the system autonomously calculates quantitative compensation values ​​for temperature, temperature change rate, wind speed, and wind direction for specific heating elements or fans, with the offset exceeding the limit as the objective and the total adjustment amplitude as the criterion. Feedforward adjustment is implemented before solder solidification to proactively balance heating from the source, suppress wind deviation, and reduce the temperature gradient in the thickness direction of the thinner board to control warping. The entire process of this invention enables pre-identification and precise intervention of component-level offset risks, significantly reducing the soldering offset defect rate, improving the first-pass yield of PCBA, and reducing manual review and rework costs. Attached Figure Description

[0015] The invention will now be further described with reference to the accompanying drawings.

[0016] Figure 1 This is a schematic diagram illustrating the steps of a PCBA patch offset intelligent correction method according to the present invention.

[0017] Figure 2 This is a schematic diagram of the structure of a PCBA patch offset intelligent correction system according to the present invention. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] Please see Figure 1-2 As shown, this invention provides a smart correction method for PCBA surface mount offset, comprising the following steps: Step S1: Obtain the set of pad coordinate points of the surface mount component and pre-calibrate the holding torque threshold of the surface mount component.

[0020] In a preferred embodiment of the present invention, the process of obtaining the pad coordinates includes: Choose any point on the PCBA board as the origin, take the plane of the PCBA board as the XY axis plane, and take the direction perpendicular to the PCBA board as the Z axis to establish a coordinate system; obtain the coordinates of the center points of each pad corresponding to the surface mount component in the coordinate system to obtain the pad coordinate point set of the surface mount component.

[0021] In a preferred embodiment of the present invention, the calibration process of the holding torque threshold includes: For any pad, obtain the wettable perimeter of the pad, multiply the preset solder surface tension coefficient by the wettable perimeter to obtain the initial wetting force value; according to the preset wetting angle of the surface mount element on the pad, project the initial wetting force value into the normal direction perpendicular to the pad to obtain the maximum normal holding force of the pad; obtain the distance between the centroid of the surface mount element and the geometric center point of the pad, and cross-multiply the maximum normal holding force with the distance to obtain the holding torque of the pad; vector sum the holding torques of each pad to obtain the holding torque threshold of the surface mount element.

[0022] It should be noted that the wettable perimeter is the total length of the edge of the pad where it contacts the surface mount component solder tip at the closed boundary, and the effective solder meniscus can be formed. Its value is determined by the geometry of the pad and the opening boundary of the solder mask layer. The preset solder surface tension coefficient is a constant related to temperature, based on the specific surface free energy of the solder metal composition in the molten state. The preset wetting angle is the contact angle between the solder meniscus and the normal direction of the pad plane when the surface mount component solder tip is immersed in molten solder. This contact angle is pre-calibrated through immersion experiments based on the surface treatment method of the component solder tip and the type of solder.

[0023] Step S2: Select several sampling points in the reflow oven. When the surface mount component starts reflow soldering, collect the control parameters at each sampling point in real time. The control parameters include the coordinates of the sampling point, temperature, wind speed and wind direction. And establish the spatial distribution of the thermal field and the spatial distribution of the wind field based on the coordinates of each sampling point and the control parameters.

[0024] In a preferred embodiment of the present invention, the process of establishing the spatial distribution of the thermal field includes: Using the coordinate system as a reference, the temperature at each sampling point in the reflow oven is interpolated by planar gridding according to the coordinates of each sampling point; and according to the speed at which the PCBA board moves longitudinally along the furnace chamber of the reflow oven and the sampling timestamp corresponding to the temperature at the sampling point, the temperatures collected at different sampling timestamps are spatiotemporally aligned in the coordinate system to obtain the spatial distribution of the thermal field.

[0025] Specifically, the planar meshing interpolation process employs an inverse distance weighting method, and the process includes: Using the coordinate system as a reference, a two-dimensional grid with equal spacing covering the XY axis plane is pre-constructed on the XY axis plane where the PCBA board is located. The two-dimensional grid with equal spacing consists of several grid nodes arranged in rows and columns. Each grid node has a definite XY coordinate in the coordinate system. The temperature of each sampling point during reflow soldering is projected onto the two-dimensional grid with equal spacing according to the coordinate of the sampling point relative to the XY axis plane of the coordinate system. For any grid node, a search range with a preset radius is defined with the grid node as the center. Sampling points falling within the search range are selected, and the interpolated temperature of the grid node is calculated using the inverse distance weighting method. That is, the temperature of the sampling points is weighted and averaged using the reciprocal of the planar distance from each sampling point to the grid node as the weight to obtain the temperature value of each grid node.

[0026] It should be noted that the purpose of the spatiotemporal alignment is to compensate for the measurement position offset caused by the movement of the PCBA board, so that the temperature of each grid node on the equally spaced two-dimensional grid corresponds to the board surface temperature distribution under the same acquisition time stamp.

[0027] In a preferred embodiment of the present invention, the process of establishing the spatial distribution of the wind field includes: Using the coordinate system as a reference, the equidistant two-dimensional grid is reused to project the wind speed and direction of each collection point in the reflow oven onto the equidistant two-dimensional grid according to the coordinates of each collection point relative to the XY axis plane of the coordinate system. For any grid node, a search range with a preset radius is defined with the grid node as the center. Collection points falling within the search range are selected, and the wind speed and direction within the search range are interpolated using the inverse distance weighting method. Based on the speed at which the PCBA board moves longitudinally along the furnace of the reflow oven and the collection timestamp of the collection point, the wind speed and direction at different collection timestamps are spatiotemporally aligned on the coordinate system to obtain the spatial distribution of the wind field.

[0028] Step S3: Divide all the pads of the surface mount component into two pad groups. For any pad group, obtain the center temperature and center temperature change rate of the pad group based on the thermal field spatial distribution. According to the center temperature and center temperature change rate of the two pad groups, obtain the surface tension deflection torque at both ends of the pad. And according to the wind field spatial distribution, obtain the wind speed and wind direction at the pad group to obtain the aerodynamic deflection torque. Vector synthesize the surface tension deflection torque and the aerodynamic deflection torque to obtain the total offset driving torque.

[0029] In a preferred embodiment of the present invention, the process of dividing all the pads of the surface mount component into two pad groups includes dividing them into a first pad group and a second pad group along a preset component offset sensitive axis direction.

[0030] Specifically, the component offset sensitive axis direction is a direction pre-determined based on the geometric characteristics of the surface mount component pad layout, which is the direction in which the surface mount component is most likely to deflect under unbalanced forces. The determination process includes: For a two-terminal component with pads symmetrically distributed at both ends, the direction of the offset sensitive axis is the direction of the line connecting the geometric centers of the two pads; for a component with pads distributed in a quadrilateral shape, the direction of the offset sensitive axis is the shorter of the lines connecting the midpoints of opposite sides; for a component with pads distributed in an array, the direction of the offset sensitive axis is the direction of the main axis of the array arrangement.

[0031] In a preferred embodiment of the present invention, the process of obtaining the center temperature and center temperature change rate of the pad group based on the spatial distribution of the thermal field includes: Obtain the coordinates of the geometric center of the pad group in the coordinate system, and denot them as the center coordinates of the pad group; in the equally spaced two-dimensional grid of the thermal field spatial distribution, take the center coordinates of the group as the target point, determine all a number of grid nodes within a preset target radius around the target point, obtain the average temperature of all grid nodes, and obtain the center temperature of the pad group; obtain the temperature of each grid node at the first n acquisition timestamps, perform a lookup calculation on each temperature to obtain the temperature change rate of the grid node, and obtain the average temperature change rate of all grid nodes to obtain the center temperature change rate.

[0032] In a preferred embodiment of the present invention, the process of obtaining the surface tension deflection torque at both ends of the pad includes: The difference between the center temperatures of the first and second pad groups is obtained and recorded as the average temperature difference between the pad groups. The difference between the center temperature change rate of the first and second pad groups is also obtained and recorded as the average temperature change rate difference between the pad groups. The average temperature difference and the average temperature change rate difference are input into a preset solder wetting characteristic data table. This table, indexed by the average temperature difference and the average temperature change rate, obtains the time required for the solder of each pad group to reach a preset peak wetting force. The imbalance of wetting forces generated between the first pad group and the second pad group during the melt wetting process is obtained; the spatial distance between the geometric center point of the first pad group and the geometric center point of the second pad group is obtained; the imbalance of wetting forces is multiplied by the spatial distance to obtain the magnitude of the surface tension deflection torque; and the direction from the geometric center point of the first pad group to the geometric center point of the second pad group is recorded as the direction of the surface tension deflection torque; the surface tension deflection torque is obtained based on the magnitude and direction of the surface tension deflection torque.

[0033] It should be noted that the process of setting the solder wetting characteristic data table includes: A test platform with controllable temperature difference and temperature change rate difference was constructed. Pad pairs of the same specifications as the surface mount component were placed on the test platform. Each pad pair was connected to an independent heating module to apply different temperature profiles to the two pads. Several sets of temperature change rate conditions were set. In each condition, the two pads were heated from room temperature to above the solder melting point at different rates, and held at a preset peak temperature. The real-time temperature and temperature difference changes of each pad were recorded. In each set of experimental conditions, the wetting force of the solder on the two pads to the component solder joints was measured in real time over time. The curves were transformed to extract the moment when the wetting force of each pad first reached the preset peak wetting force, and the peak wetting force time difference between two pads was obtained. The difference between the peak wetting force of two pads in the melting and wetting stage was also extracted as the wetting force imbalance under the working condition. The temperature difference, temperature change rate difference, peak wetting force time difference, and wetting force imbalance between two pads corresponding to each working condition were recorded as a set of data records. After covering several working conditions, the temperature difference and temperature change rate difference were used as two-dimensional indexes, and the peak wetting force time difference and wetting force imbalance were used as output values ​​to construct a solder wetting characteristic data table.

[0034] In a preferred embodiment of the present invention, the process of obtaining the aerodynamic deflection torque includes: For any pad group, the coordinates of the group center of the pad group are obtained as the wind field sampling point in the coordinate system; in the equally spaced two-dimensional grid of the wind field spatial distribution, all several grid nodes within a preset target radius around the wind field sampling point are obtained, the average wind speed at all grid nodes and the average wind direction at all grid nodes are obtained, and the wind speed and wind direction of the pad group are obtained, and are recorded as group wind speed and group direction respectively. The average value between the group wind speed of the first pad group and the group wind speed of the second pad group is obtained to obtain the equivalent wind speed acting on the surface mount component; the average direction between the group direction of the first pad group and the group direction of the second pad group is obtained to obtain the equivalent wind direction acting on the surface mount component; and the wind pressure F is obtained based on the equivalent wind direction. wind =(1 / 2)×Cd×ρ×A proj ×V eq 2 Where Cd is the preset aerodynamic drag coefficient, ρ is the air density in the reflow oven, and A proj V is the equivalent windward projected area of ​​the patch element in the direction of incoming flow. eq The equivalent wind speed of the patch element is given; the aerodynamic deflection torque is obtained based on the direction of the equivalent wind direction and the magnitude of the wind pressure.

[0035] Specifically, wind pressure F wind The direction vector is taken as the unit vector of the equivalent wind direction, denoted as e. wind The aerodynamic deflection torque M of the patch elementaero =r×(F wind ·e wind ), where r is the vector pointing from the centroid coordinate of the surface mount element to the center of the projection of the surface mount element onto the pad plane in the coordinate system, i.e., the lever arm vector, whose modulus is the height of the centroid and whose direction is perpendicular from the centroid to the pad plane.

[0036] Step S4: Compare the total offset driving torque with the holding torque threshold to determine whether the patch element is a risky element; if the patch element is a risky element, generate a set of compensation value parameters for the patch element.

[0037] In a preferred embodiment of the present invention, the process of determining whether the patch element is a risk element includes: Obtain the scalar value of the total offset driving torque. If the scalar value is greater than the holding torque threshold, it is determined that the patch element has shifted and is recorded as a risk element; otherwise, it is determined that the patch element has not shifted and is recorded as a safe element.

[0038] In a preferred embodiment of the present invention, the process of generating the compensation value parameter set of the patch element includes: The difference between the scalar value of the total offset driving torque of the risk element and the holding torque threshold is used as the offset suppression requirement, and the direction of the total offset driving torque is used as the offset direction. In the preset multivariate regression mapping relationship library, the spatial distribution of the thermal field and the spatial distribution of the wind field at the location of the risk element are used as the current operating condition input, the offset suppression requirement is used as the target reduction amount, and the offset direction is used as the constraint direction to retrieve multiple sets of candidate compensation value combinations in reverse. Each set of candidate compensation value combinations includes a temperature compensation value or a temperature change rate compensation value for at least one heating element, or a wind speed compensation value or a wind direction compensation value for at least one fan. Using the minimum adjustment amount as the preferred criterion, the set of compensation value parameters that minimizes the total adjustment range of the heating element or fan is selected from the several sets of candidate compensation value combinations as the compensation value parameter set for the risk element.

[0039] A PCBA surface mount misalignment intelligent correction system includes: Data preprocessing module: Obtains the set of pad coordinate points of the surface mount component and pre-calibrates the holding torque threshold of the surface mount component; Control parameter analysis module: Several acquisition points are selected in the reflow oven. When the surface mount component starts reflow soldering, the control parameters at each acquisition point are acquired in real time. The control parameters include the coordinates of the acquisition point, temperature, wind speed and wind direction; and the spatial distribution of the thermal field and the spatial distribution of the wind field are established based on the coordinates of each acquisition point and the control parameters. Offset Analysis Module: Divides all pads of the surface mount component into two pad groups. For any pad group, the center temperature and center temperature change rate of the pad group are obtained based on the thermal field spatial distribution. The surface tension deflection torque at both ends of the pads is obtained based on the center temperature and center temperature change rate of the two pad groups. The wind speed and wind direction at the pad group are obtained based on the wind field spatial distribution, and the aerodynamic deflection torque is obtained. The surface tension deflection torque and the aerodynamic deflection torque are vectorially synthesized to obtain the total offset driving torque. Correction module: compares the total offset driving torque with the holding torque threshold to determine whether the patch element is a risky element; if the patch element is a risky element, it generates a set of compensation value parameters for the patch element.

[0040] The foregoing has provided a detailed description of one embodiment of the present invention, but this description is merely a preferred embodiment and should not be construed as limiting the scope of the invention. All equivalent variations and modifications made within the scope of the present invention should still fall within the scope of the present invention.

Claims

1. A method for intelligent correction of PCBA surface mount offset, characterized in that, Includes the following steps: Step S1: Obtain the set of pad coordinate points of the surface mount component and pre-calibrate the holding torque threshold of the surface mount component; Step S2: Select several sampling points in the reflow oven. When the surface mount component starts reflow soldering, collect the control parameters at each sampling point in real time. The control parameters include the coordinates of the sampling point, temperature, wind speed and wind direction. And establish the spatial distribution of the thermal field and the spatial distribution of the wind field based on the coordinates of each sampling point and the control parameters. Step S3: Divide all the pads of the surface mount component into two pad groups. For any pad group, obtain the center temperature and center temperature change rate of the pad group based on the thermal field spatial distribution. According to the center temperature and center temperature change rate of the two pad groups, obtain the surface tension deflection torque at both ends of the pad. And according to the wind field spatial distribution, obtain the wind speed and wind direction at the pad group, and obtain the aerodynamic deflection torque. Vector synthesize the surface tension deflection torque and the aerodynamic deflection torque to obtain the total offset driving torque. Step S4: Compare the total offset driving torque with the holding torque threshold to determine whether the patch element is a risk element; If the patch element is a risky element, then a set of compensation value parameters for the patch element is generated.

2. The intelligent correction method for PCBA surface mount offset according to claim 1, characterized in that, In step S1, the process of obtaining the pad coordinates includes: Choose any point on the PCBA board as the origin, take the plane of the PCBA board as the XY axis plane, and take the direction perpendicular to the PCBA board as the Z axis to establish a coordinate system; obtain the coordinates of the center points of each pad corresponding to the surface mount component in the coordinate system to obtain the pad coordinate point set of the surface mount component.

3. The intelligent correction method for PCBA surface mount offset according to claim 1, characterized in that, In step S1, the calibration process of the holding torque threshold includes: For any pad, obtain the wettable perimeter of the pad, multiply the preset solder surface tension coefficient by the wettable perimeter to obtain the initial wetting force value; according to the preset wetting angle of the surface mount element on the pad, project the initial wetting force value into the normal direction perpendicular to the pad to obtain the maximum normal holding force of the pad; obtain the distance between the centroid of the surface mount element and the geometric center point of the pad, and cross-multiply the maximum normal holding force with the distance to obtain the holding torque of the pad; vector sum the holding torques of each pad to obtain the holding torque threshold of the surface mount element.

4. The intelligent correction method for PCBA surface mount offset according to claim 1, characterized in that, In step S2, the process of establishing the spatial distribution of the thermal field includes: Using the coordinate system as a reference, the temperature at each sampling point in the reflow oven is interpolated by planar gridding according to the coordinates of each sampling point; and according to the speed at which the PCBA board moves longitudinally along the furnace chamber of the reflow oven and the sampling timestamp corresponding to the temperature at the sampling point, the temperatures collected at different sampling timestamps are spatiotemporally aligned in the coordinate system to obtain the spatial distribution of the thermal field.

5. The intelligent correction method for PCBA surface mount offset according to claim 1, characterized in that, In step S2, the process of establishing the spatial distribution of the wind field includes: Using the coordinate system as a reference, the equidistant two-dimensional grid is reused to project the wind speed and direction of each collection point in the reflow oven onto the equidistant two-dimensional grid according to the coordinates of each collection point relative to the XY axis plane of the coordinate system. For any grid node, a search range with a preset radius is defined with the grid node as the center. Collection points falling within the search range are selected, and the wind speed and direction within the search range are interpolated using the inverse distance weighting method. Based on the speed at which the PCBA board moves longitudinally along the furnace of the reflow oven and the collection timestamp of the collection point, the wind speed and direction at different collection timestamps are spatiotemporally aligned on the coordinate system to obtain the spatial distribution of the wind field.

6. The intelligent correction method for PCBA surface mount offset according to claim 1, characterized in that, In step S3, the process of obtaining the center temperature and center temperature change rate of the pad group based on the spatial distribution of the thermal field includes: Obtain the coordinates of the geometric center of the pad group in the coordinate system, and denot them as the center coordinates of the pad group; in the equally spaced two-dimensional grid of the thermal field spatial distribution, take the center coordinates of the group as the target point, determine all a number of grid nodes within a preset target radius around the target point, obtain the average temperature of all grid nodes, and obtain the center temperature of the pad group; obtain the temperature of each grid node at the first n acquisition timestamps, perform a lookup calculation on each temperature to obtain the temperature change rate of the grid node, and obtain the average temperature change rate of all grid nodes to obtain the center temperature change rate.

7. The intelligent correction method for PCBA surface mount offset according to claim 1, characterized in that, In step S3, the process of obtaining the surface tension deflection torque at both ends of the pad includes: The system is divided into a first pad group and a second pad group along a preset component offset sensitive axis. The difference between the center temperatures of the first pad group and the second pad group is obtained and recorded as the average temperature difference between the pad groups. The difference between the center temperature change rate of the first pad group and the center temperature change rate of the second pad group is also obtained and recorded as the average temperature change rate difference between the pad groups. The average temperature difference and the average temperature change rate difference are input into a preset solder wetting characteristic data table. The solder wetting characteristic data table uses the average temperature difference and the average temperature change rate as indexes to obtain the solder wetting characteristics of the first pad group and the second pad group respectively, achieving the preset... The required time for the peak wetting force is determined, and the wetting force imbalance generated by the first pad group and the second pad group during the melt wetting process is obtained respectively. The spatial distance between the geometric center point of the first pad group and the geometric center point of the second pad group is obtained. The wetting force imbalance is multiplied by the spatial distance to obtain the magnitude of the surface tension deflection torque. The direction from the geometric center point of the first pad group to the geometric center point of the second pad group is recorded as the direction of the surface tension deflection torque. The surface tension deflection torque is obtained based on the magnitude and direction of the surface tension deflection torque.

8. A PCBA surface mount misalignment intelligent correction system, characterized in that, include: Data preprocessing module: Obtains the set of pad coordinate points of the surface mount component and pre-calibrates the holding torque threshold of the surface mount component; Control parameter analysis module: Several acquisition points are selected in the reflow oven. When the surface mount component starts reflow soldering, the control parameters at each acquisition point are acquired in real time. The control parameters include the coordinates of the acquisition point, temperature, wind speed and wind direction; and the spatial distribution of the thermal field and the spatial distribution of the wind field are established based on the coordinates of each acquisition point and the control parameters. Offset Analysis Module: Divides all pads of the surface mount component into two pad groups. For any pad group, the center temperature and center temperature change rate of the pad group are obtained based on the thermal field spatial distribution. The surface tension deflection torque at both ends of the pads is obtained based on the center temperature and center temperature change rate of the two pad groups. The wind speed and wind direction at the pad group are obtained based on the wind field spatial distribution, and the aerodynamic deflection torque is obtained. The surface tension deflection torque and the aerodynamic deflection torque are vectorially synthesized to obtain the total offset driving torque. Correction module: compares the total offset driving torque with the holding torque threshold to determine whether the patch element is a risky element; If the patch element is a risky element, then a set of compensation value parameters for the patch element is generated.

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