An intelligent optimization control method for SMT reflow soldering temperature curve

Abstract

The present application relates to the field of industrial automation control, and specifically discloses a kind of SMT reflow soldering temperature curve intelligent optimization control method, comprising: collecting measuring point temperature time series data forms board surface temperature field sequence, extracts measuring point temperature range and obtains board surface temperature spatial dispersion, analyzes and judges non-uniform form with soldering point process window containment relationship;If non-uniform form is formed, compare the heating phase to extract the peak value arrival order to determine the cold point hot spot to obtain the relative lag diagram, combined with component heat capacity label to determine the dominant imbalance class;Mapping cold point hot spot to upper and lower heating components in temperature zone to obtain heating misplacement diagram, deduce the heat distribution to cold point side;According to the adjustment result of heat distribution, adjust the upper and lower heating components of each temperature zone to generate coordinated control parameters, and recollect the corrected temperature field sequence to obtain the corrected dispersion;According to the corrected dispersion, the uniformity of the board surface temperature is obtained, which meets the soldering point process window containment output coordinated control parameters as the optimized temperature curve parameters, while avoiding false welding and component damage, the spatial uniformity of the board surface temperature is improved.

Description

Technical Field

[0001] This invention relates to the field of industrial automation control, specifically to an intelligent optimization control method for SMT reflow soldering temperature profile. Background Technology

[0002] During reflow soldering, the same printed circuit board often contains both high-capacity components such as ball grid array devices and thick copper areas, and low-capacity components such as chip resistors and capacitors. Due to the significant difference in heat capacity, the two types of components are heated at different rates in the furnace, resulting in a slow-heating cold spot and a fast-heating hot spot on the board surface, with a large spatial temperature difference between them. If the cold spot temperature is insufficient, the solder joint will not melt fully, easily resulting in a cold solder joint; if the hot spot temperature is too high, it may cause thermal damage to the components. Moreover, both types of defects may occur simultaneously. Therefore, the spatial uniformity of the board surface temperature directly affects whether the solder joints can fall into the process window simultaneously.

[0003] Existing reflow soldering control schemes mostly focus on the average temperature of each temperature zone as the controlled object, controlling the process by adjusting the zone temperature. This approach fails to detect and suppress the spatial temperature difference between cold and hot spots within the board. In practice, offline temperature sensing plates are often used to locate cold spots, with manual tightening of settings. However, this method relies on static trial and error and does not establish real-time closed-loop control of the temperature field within the board surface. When the product mix density is high and the heat capacity distribution is complex, relying solely on average temperature control of each temperature zone is insufficient to simultaneously address both cold and hot spots.

[0004] Therefore, it is necessary to dynamically adjust the heating power distribution and chain speed of each temperature zone online based on multi-point temperature feedback at the board level, so that cold and hot points can enter the acceptable process range simultaneously, thereby improving the temperature uniformity of the board surface.

[0005] Therefore, this invention provides an intelligent optimization and control method for SMT reflow soldering temperature profile. Summary of the Invention

[0006] The purpose of this invention is to provide an intelligent optimization and control method for SMT reflow soldering temperature profiles to solve the aforementioned background problems.

[0007] The objective of this invention can be achieved through the following technical solution: a method for intelligent optimization and control of SMT reflow soldering temperature profile, comprising: Temperature time-series data of measuring points on the surface of the printed circuit board in the reflow oven are collected, aligned and spliced ​​to form the temperature field sequence of the board surface, and the temperature range of the measuring points is extracted to obtain the temperature spatial dispersion of the board surface; the relationship between the temperature spatial dispersion of the board surface and the containment relationship of the solder joint process window is analyzed to determine whether the board surface has formed a non-uniform shape in order to perform temperature adjustment. If a non-uniform shape is formed, the temperature field sequence on the plate is compared between the heating phases of the measuring points and the peak arrival order is extracted to determine the cold and hot points and obtain the relative hysteresis diagram to form feedback control; based on the relative hysteresis diagram and the corresponding element heat capacity label of each measuring point, the dominant imbalance type of the non-uniform shape is determined. Based on the dominant imbalance class and the relative hysteresis diagram, the spatial locations of cold and hot points are mapped to the corresponding temperature zones and upper and lower heating components to obtain the heating misalignment diagram; the heat distribution direction that each temperature zone and upper and lower heating components need to be transferred to the cold point side is derived, and the heat distribution direction adjustment result is generated. Based on the heat distribution adjustment results, the temperature zones and the upper and lower heating components are coordinated and adjusted to generate co-control parameters. The plate surface temperature field sequence is sampled in real time as control feedback to obtain the corrected temperature field sequence. Based on the corrected temperature field sequence, the plate surface temperature spatial dispersion is extracted again and recorded as the corrected dispersion to correct the temperature distribution in a closed loop. Based on the correction of dispersion, the convergence deviation between cold and hot spots is evaluated to obtain the temperature uniformity of the board surface. When the temperature uniformity of the board surface meets the containment relationship of the solder joint process window, the co-control parameters are output as the optimized temperature control curve.

[0008] Furthermore, the process of determining whether the board surface forms a non-uniform shape is as follows: Temperature time series data of each measuring point is collected, and range discretization analysis is performed to obtain the spatial dispersion of the plate surface; and the maximum value of the temperature values ​​of all measuring points is selected as the peak temperature of the plate surface based on the temperature time series data, and the sampling time corresponding to the peak temperature of the plate surface is marked as the peak time of the plate surface. Obtain the spatial dispersion of the plate temperature corresponding to the peak value moment; If the spatial dispersion of the plate temperature at the peak moment is greater than the window temperature width of the solder joint process window, it is determined that the plate surface has formed a non-uniform shape with both cold and hot spots.

[0009] Furthermore, the process of performing range discretization analysis is as follows: The furnace position corresponding to each measuring point is obtained, the temperature time series data of each measuring point is classified according to the furnace position, and the plate surface temperature field sequence is obtained by splicing the data column by column at the same sampling time with a unified sampling time sequence as the alignment reference. Based on the temperature field sequence of the plate, the difference between the highest and lowest temperatures of all measuring points at each sampling time is extracted as the temperature difference range between measuring points, and the plate temperature spatial dispersion is obtained by arranging them in chronological order.

[0010] Furthermore, the process of identifying cold and hot spots and obtaining the relative lag plot is as follows: The arrival time of the peak value in the temperature sequence of each measuring point is extracted from the plate temperature field sequence, and the peak value arrival order is obtained by arranging them according to the time sequence. The measuring point with the smallest peak arrival time in the peak arrival sequence is marked as a hot spot, and the measuring point with the largest peak arrival time is marked as a cold spot, with the hot spot as the benchmark measuring point; Subtract the peak arrival time of each measuring point from the peak arrival time of the reference measuring point to obtain the hysteresis of each measuring point, and mark them according to their positions in the furnace to form a relative hysteresis diagram.

[0011] Furthermore, the process of determining the dominant imbalance class of non-uniform morphology is as follows: Obtain the heat capacity category of the corresponding element at each measuring point, and divide the measuring points into the plate area corresponding to the large heat capacity element and the plate area corresponding to the small heat capacity element; If the cold spot is located in the plate area corresponding to the large heat capacity element and the hot spot is located in the plate area corresponding to the small heat capacity element, and the hysteresis of the measuring point corresponding to the large heat capacity element is generally greater than the hysteresis of the measuring point corresponding to the small heat capacity element, then the dominant imbalance type is determined to be the hysteresis type; otherwise, the dominant imbalance type is determined to be the overheating type.

[0012] Furthermore, the process of generating the heat distribution adjustment result is as follows: Based on the dominant imbalance class and the relative lag diagram, a heating misalignment diagram is obtained by spatial mapping analysis of cold spots and hot spots. If the dominant imbalance is a lag type, the heating direction is derived from the heating misalignment diagram as transferring heating power from the temperature zone of the hot spot to the temperature zone of the cold spot along the chain speed direction. If the dominant imbalance is a bias type, the component associated with the measuring point with the large lag is determined to be the weaker side, and the heating direction is to transfer heating power from the stronger side to the weaker side within the temperature zone of the cold spot. The heating direction is marked zone by zone to obtain the heating direction adjustment result.

[0013] Furthermore, the process of obtaining the heating misalignment map is as follows: Read the furnace positions and hysteresis of cold and hot spots in the relative hysteresis diagram, and obtain the temperature zone layout parameters of the start and end axial coordinates of each temperature zone along the chain speed direction. The cumulative displacement of the chain speed is calculated by multiplying the peak value of the plate surface with the chain speed. This displacement is then superimposed on the furnace positions of the cold and hot points to determine the temperature zones of the cold and hot points. Obtain the printed circuit board component layout data and extract the component placement surface, and associate the cold spots and hot spots with the upper heating components or lower heating components of their respective temperature zones; The heating misalignment diagram is obtained by marking the temperature zones of cold points and hot points, the upper or lower heating components associated with cold points and hot points, the upper or lower heating components associated with hot points, and the hysteresis between cold and hot points according to their positions in the furnace.

[0014] Furthermore, the process of generating co-control parameters is as follows: Based on the heat distribution adjustment results, the set values ​​of each temperature zone and the power distribution between the upper and lower heating components within the temperature zone are adjusted in a coordinated manner. The coordinated adjustment gives the temperature zone set value, power distribution and chain speed together in the same adjustment, and constrains the total heating power to remain equal before and after the adjustment. After each coordinated adjustment is completed, the adjusted temperature zone set value, power distribution and chain speed are combined and recorded as a set of values ​​to obtain the coordinated control parameters.

[0015] Furthermore, the process of obtaining the temperature uniformity of the plate surface is as follows: The maximum spatial temperature difference is generated based on the corrected dispersion and determined as the plate surface temperature uniformity.

[0016] Furthermore, the process of outputting co-control parameters as parameters for optimizing the temperature curve is as follows: When the temperature uniformity of the board surface is less than or equal to the window temperature width of the solder joint process window, the output co-control parameter is the optimized temperature curve parameter; If the board surface temperature is greater than the window temperature width of the solder joint process window, then continue to perform collaborative adjustments to generate new collaborative control parameters until the board surface temperature uniformity is less than or equal to the window temperature width of the solder joint process window, then output the collaborative control parameters as the optimized temperature curve parameters. If the board temperature is still greater than the window temperature width of the solder joint process window when the number of collaborative adjustments reaches the preset maximum number of iterations, then the collaborative control parameter corresponding to the minimum temperature difference convergence degree is output as the parameter for optimizing the temperature curve.

[0017] The beneficial effects of this invention are as follows: 1. Collect temperature time-series data from measuring points on the surface of the printed circuit board in the reflow oven, align and stitch them to form a temperature field sequence on the board surface, and extract the temperature range of the measuring points to obtain the spatial dispersion of the board surface temperature; analyze the containment relationship between the spatial dispersion of the board surface temperature and the solder joint process window to determine whether the board surface has formed a non-uniform shape; transform the spatial temperature difference of the measuring points on the board surface into a specific non-uniform shape index, and change the determination of whether the board surface temperature is uniform from offline temperature measurement based on experience to an automated control criterion.

[0018] 2. If a non-uniform shape is formed, the temperature field sequence on the plate is analyzed by comparing the heating phase between measurement points and extracting the peak arrival order to identify cold and hot points and obtain a relative hysteresis diagram. Based on the relative hysteresis diagram and the corresponding element heat capacity labeling at each measurement point, the dominant imbalance type of the non-uniform shape is determined. The dominant imbalance type is quickly distinguished from the dominant imbalance type of heat capacity difference and the dominant imbalance type of upper and lower heating components to avoid misadjustment caused by indiscriminate compensation for non-uniform shapes. Based on the dominant imbalance type and the relative hysteresis diagram, the spatial positions of cold and hot points are mapped to the corresponding temperature zones and upper and lower heating components to obtain a heating misalignment diagram. The heat distribution direction that needs to be transferred to the cold point side for each temperature zone and upper and lower heating components is derived to generate the heat distribution direction adjustment result. The overall temperature difference problem is located to the specific temperature zone and upper and lower heating components, so that the direction of heating power transfer is clear and executable.

[0019] 3. Based on the heat distribution adjustment results, the temperature zones and upper and lower heating components are coordinated and adjusted to generate co-control parameters. The corrected temperature field sequence is obtained by real-time re-sampling of the board surface temperature field sequence. Based on the corrected temperature field sequence, the spatial dispersion of the board surface temperature is re-extracted and recorded as the corrected dispersion. Under the premise of not increasing the total heating power, cold points are compensated in a directional manner and hot spots are suppressed from overheating. A closed-loop iteration is formed through real-time re-sampling. The convergence degree of the temperature difference between cold points and hot spots is evaluated based on the corrected dispersion to obtain the board surface temperature uniformity. When the board surface temperature uniformity meets the solder joint process window containment relationship, the co-control parameters are output as the parameters for optimizing the temperature curve. The optimization parameters are output using the solder joint process window containment relationship as the convergence criterion to ensure that cold points and hot spots enter the process window simultaneously and avoid cold solder joints and thermal damage. Attached Figure Description

[0020] The invention will now be further described with reference to the accompanying drawings.

[0021] Figure 1 This is a flowchart of the steps of an intelligent optimization control method for SMT reflow soldering temperature profile according to the present invention. Figure 2 This is a logic diagram of the output optimized temperature curve parameters in this invention; Figure 3 This is a functional module diagram of an intelligent optimization control method for SMT reflow soldering temperature profile in this invention. Detailed Implementation

[0022] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with specific embodiments. Example 1

[0023] like Figure 1 As shown, an intelligent optimization and control method for SMT reflow soldering temperature profile includes: S1: Collect temperature time series data of measuring points on the surface of the printed circuit board in the reflow oven, align and splice them to form the temperature field sequence of the board surface, and extract the temperature range of the measuring points to obtain the temperature spatial dispersion of the board surface; analyze the containment relationship between the temperature spatial dispersion of the board surface and the solder joint process window, and determine whether the board surface forms a non-uniform shape in order to perform temperature adjustment. The process of collecting temperature time-series data from measuring points on the surface of the printed circuit board inside the reflow oven, aligning and stitching them to form a temperature field sequence on the board surface, and extracting the temperature range of the measuring points to obtain the spatial dispersion of the board surface temperature is as follows: During the reflow soldering process of the printed circuit board in the reflow oven, multiple measuring points are set on the surface of the printed circuit board. The measuring points are located in the board area corresponding to the large heat capacity element and the board area corresponding to the small heat capacity element, respectively. A thermocouple is installed at each measuring point. The signal lead of the thermocouple is connected to a data logger. The data logger continuously collects the temperature at each measuring point at equal time intervals to obtain the temperature time series data of each measuring point. Temperature time series data consists of a sampling time sequence and the temperature value of the measuring point corresponding to each sampling time in the sampling time sequence. The sampling time sequence records the time process of temperature measurement. When setting up the measurement points, record the position of each measurement point inside the reflow oven. The position inside the oven is calibrated using the position coordinates under the coordinate system of the printed circuit board surface and saved along with the temperature time series data. Among them, the furnace position calibration enables spatial comparability of temperature time series data at different measuring points, thus allowing temperature values ​​at different furnace positions to be compared within the same spatial frame at the same sampling time. The temperature time series data of each measuring point are classified according to their location inside the furnace, so that each location inside the furnace corresponds to a temperature sequence with the sampling time as the horizontal axis and the measuring point temperature as the vertical axis. Using a unified sampling time sequence as the alignment benchmark, the temperature sequences of all measuring points are spliced ​​together column by column at the same sampling time, and the spliced ​​data are arranged according to the position inside the furnace to form the plate surface temperature field sequence. It is understandable that the plate surface temperature field sequence is a temperature dataset with the sampling time as the time dimension and the furnace position as the spatial dimension. Specifically, it is arranged in matrix form, where each row corresponds to a sampling time and each column corresponds to a furnace position. The value of each element in the matrix is ​​the temperature value of the measuring point at the corresponding sampling time and furnace position. The spatial slice of the plate surface temperature field sequence at each sampling time reflects the plate surface temperature distribution at each sampling time. Based on the plate temperature field sequence, the highest and lowest temperatures among all the temperature values ​​of all measuring points at each sampling time are extracted, and the temperature difference range between measuring points at each sampling time is obtained by subtracting the lowest temperature from the highest temperature. Arrange the temperature difference range between the measurement points corresponding to all sampling times covered by the plate temperature field sequence in chronological order to obtain the spatial dispersion of plate temperature as it changes with sampling time. Among them, the spatial dispersion of board surface temperature characterizes the change of the maximum spatial temperature difference between cold and hot spots on the surface of the printed circuit board during the reflow soldering process as a function of sampling time. The process of analyzing the spatial dispersion of the board surface temperature and the containment relationship of the solder joint process window to determine whether the board surface has formed a non-uniform shape is as follows: The maximum value of the temperature at all measuring points during the reflow soldering process is taken as the peak temperature of the board surface. The sampling time corresponding to the maximum value is marked as the peak time of the board surface. The spatial dispersion of the board surface temperature corresponding to the peak time is obtained. The spatial dispersion of the board surface temperature reflects the maximum spatial temperature difference between cold spots and hot spots during the peak stage. The board surface morphology is determined based on the relationship between the spatial dispersion of the board surface temperature at the peak moment and the containment relationship of the solder joint process window. It should be noted that the solder joint process window is the temperature range allowed for a reliable solder joint connection. The solder joint process window is jointly defined by the minimum temperature required for the solder joint to fully melt and the maximum temperature allowed for the component to avoid thermal damage. If the temperature is lower than the minimum temperature required for the solder joint to fully melt, a cold solder joint will be formed; if the temperature is higher than the maximum temperature allowed for the component to avoid thermal damage, the component will be damaged. The temperature width of the solder joint process window is the difference between the minimum temperature required for the solder joint to fully melt and the maximum temperature allowed for the component to avoid thermal damage. The temperature width reflects the temperature span that the same solder joint process window can simultaneously encompass. Among them, the containment relationship refers to whether the window temperature width of the solder joint process window can simultaneously contain the maximum spatial temperature difference between the cold point and the hot point, which is characterized by the spatial dispersion of the plate surface temperature at the peak moment of the plate surface at the same temperature level. If the spatial dispersion of the plate temperature at the peak moment is greater than the window temperature width of the solder joint process window, the same solder joint process window cannot simultaneously contain cold spots and hot spots at the same temperature level, and it is determined that the plate surface forms a non-uniform shape in which cold spots and hot spots coexist. If the spatial dispersion of the plate temperature corresponding to the peak moment is less than or equal to the window temperature width of the solder joint process window, the same solder joint process window can simultaneously contain cold spots and hot spots at the same temperature level, and it is determined that the plate surface has not formed a non-uniform shape in which cold spots and hot spots coexist. S2: If a non-uniform shape is formed, the temperature field sequence of the plate surface is compared between the heating phases of the measurement points and the peak arrival order is extracted to determine the cold and hot points and obtain the relative hysteresis diagram to form feedback control; based on the relative hysteresis diagram and the corresponding element heat capacity label of each measurement point, the dominant imbalance type of the non-uniform shape is determined. If a non-uniform shape is formed, the process of comparing the heating phase between measurement points and extracting the peak arrival order of the temperature field sequence on the plate surface to determine cold and hot points and obtain the relative hysteresis diagram is as follows: The temperature sequence of each measuring point is extracted from the plate surface temperature field sequence according to the position in the furnace. The maximum value of the temperature value of each measuring point is found in the temperature sequence of each measuring point. The sampling time corresponding to the maximum value of the temperature value of the measuring point is marked as the peak arrival time of the corresponding measuring point. The peak arrival times of each measuring point are marked on the same time axis. By comparing the timing of the peak temperature at different measuring points in different locations inside the furnace, the relative misalignment of the heating phase at each measuring point can be obtained. The relative misalignment of the heating phase at each measuring point is characterized by the difference in the peak arrival time. Measuring points with a later peak arrival time have a relatively delayed heating phase, while measuring points with an earlier peak arrival time have a relatively advanced heating phase. Extract the peak arrival time of each measuring point and arrange them according to the time sequence to obtain the peak arrival order; The measuring point that reaches the peak temperature first in the peak temperature arrival sequence corresponds to the plate area with the fastest temperature rise, i.e., the hot spot; the measuring point that reaches the peak temperature last corresponds to the plate area with the slowest temperature rise, i.e., the cold spot. Using the measurement point that reaches the peak temperature earliest in the peak arrival sequence as the reference measurement point, the peak arrival time of each measurement point is subtracted from the peak arrival time of the reference measurement point to obtain the lag of each measurement point relative to the reference measurement point. The lag is then marked on the plate frame with the furnace position as the spatial coordinate to form a relative lag diagram between cold and hot points. Among them, the relative lag diagram of cold points and hot points shows the degree of lag between cold points and hot points on the plate. The degree of lag is measured by the difference between the arrival time of the peak of the cold point and the arrival time of the peak of the hot point. The difference between the arrival time of the peak of the cold point and the arrival time of the peak of the hot point represents the phase delay of the heating of the cold point relative to the hot point. The process of determining the dominant imbalance type of non-uniform morphology based on the relative hysteresis diagram and the corresponding element heat capacity labeling at each measuring point is as follows: In step S1, the heat capacity category of the component corresponding to each measuring point is recorded when setting up the measuring points. The heat capacity category of the component corresponding to each measuring point is used as the component heat capacity label in step S2. The component heat capacity labeling divides the measuring points into two categories: those located on the plate area corresponding to large heat capacity components and those located on the plate area corresponding to small heat capacity components. The component heat capacity labeling provides a heat capacity basis for distinguishing the non-uniform morphology-dominated imbalance type. The hysteresis at each measuring point in the relative hysteresis diagram is correlated and compared with the component heat capacity label: If the cold spot is located in the plate area corresponding to the large heat capacity element and the hot spot is located in the plate area corresponding to the small heat capacity element, and the overall hysteresis of the measuring point corresponding to the large heat capacity element is greater than the hysteresis of the measuring point corresponding to the small heat capacity element, then the non-uniform shape is determined to be dominated by local heat capacity differences, and the dominant imbalance type is determined to be the hysteresis type. If the distribution of cold and hot spots does not follow the above pattern according to the component's heat capacity label, then the non-uniform shape is determined to be dominated by the imbalance of heating from top to bottom, and the dominant imbalance type is determined to be the overheating type. It should be noted that the identification basis for the overheating type is that the measurement points with large hysteresis in the relative hysteresis diagram are not concentrated in the plate area corresponding to the large heat capacity element, but correspond to the side where the upper and lower heating components are weaker. Moreover, the measurement points with large hysteresis include the measurement points corresponding to both the large heat capacity element and the small heat capacity element, indicating that the hysteresis is not caused by the difference in heat capacity. The non-uniform morphology of the hysteresis type and the overheating type is mainly caused by two types of factors: element-side factors and heating-side factors. The dominant imbalance type of the non-uniform morphology must be one of the hysteresis type and the overheating type. S3: Based on the dominant imbalance class and the relative hysteresis diagram, the spatial locations of cold and hot points are mapped to the corresponding temperature zones and upper and lower heating components to obtain the heating misalignment diagram; the heat distribution direction that each temperature zone and upper and lower heating components need to be transferred to the cold point side is derived, and the heat distribution direction adjustment result is generated. The process of mapping the spatial locations of cold and hot spots to the corresponding temperature zones and upper and lower heating components, based on the dominant imbalance class and the relative hysteresis diagram, to obtain the heating misalignment diagram is as follows: Read the positions of cold spots and hot spots in the furnace in the coordinate system of the printed circuit board surface from the relative hysteresis diagram, and read the hysteresis of cold spots and hot spots relative to the reference measurement point. The temperature zone layout parameters of the reflow oven are obtained and stored in the control system in the form of an array or table. The starting and ending axial coordinates of each temperature zone arranged sequentially along the chain speed direction are recorded, and each temperature zone is identified by a unique temperature zone number. The control system determines the temperature zone number to which the cold and hot points belong by querying the starting and ending axial coordinate range of each temperature zone in the temperature zone layout parameters based on the axial coordinates of the cold and hot points in the oven. Wherein, chain speed is the conveying speed of the reflow oven conveyor chain; Each temperature zone of the reflow oven is equipped with an upper heating element and a lower heating element. The upper heating element is located on one side of the top surface of the printed circuit board, and the lower heating element is located on one side of the bottom surface of the printed circuit board. The peak time marked in step S1 is used as the reference time for spatial position mapping. The cumulative displacement of the printed circuit board at the peak time of the board surface is calculated based on the peak time of the board surface and the chain speed. The cumulative displacement of the chain speed is the product of the chain speed and the peak time of the board surface. The furnace positions of the cold and hot points are superimposed along the chain speed direction to accumulate the chain speed displacement, thus obtaining the furnace axial coordinates of the cold and hot points at the peak moment on the plate surface. By comparing the furnace axial coordinates of the cold and hot points with the start and end axial coordinates of the temperature zone layout parameters, the temperature zones to which the cold points and hot points belong can be determined. Among them, the starting and ending axial coordinates of the furnace axial coordinates and the temperature zone layout parameters are all based on the reflow oven inlet as the axial origin. Specifically, determining the temperature zones of the cold and hot points allows the spatial locations of the cold and hot points to be assigned to specific heating sections of the reflow oven, providing a spatial reference for deriving the heat distribution direction. Obtain PCB component layout data. The PCB component layout data records the placement surface of each component on the top or bottom surface of the PCB, which is provided by the PCB design documents. Based on the component layout surface corresponding to the measuring point, cold points and hot points are respectively associated with the upper heating component or lower heating component of their respective temperature zones. If the component corresponding to the measuring point is located on the top surface of the printed circuit board, it is associated with the upper heating component; if the component corresponding to the measuring point is located on the bottom surface of the printed circuit board, it is associated with the lower heating component. The temperature zones of cold spots and hot spots, the upper or lower heating components associated with cold spots and hot spots, and the hysteresis of cold spots and hot spots are marked on the coordinate system of the printed circuit board surface according to their positions in the furnace. Cold spots and hot spots and their associated heating components are distinguished by different marks or colors, and the axial boundaries of each temperature zone are marked to obtain a heating misalignment diagram. It should be noted that the heating misalignment diagram shows the misalignment relationship between cold points and hot points in terms of temperature zone and upper and lower heating components, and marks the axial spacing between the temperature zone to which the cold point belongs and the temperature zone to which the hot point belongs along the chain speed direction; the heating misalignment diagram enables step S4 to locate the upper or lower heating component that needs to be enhanced according to the temperature zone to which the cold point belongs and the upper or lower heating component associated with the cold point, and avoids overheating the temperature zone to which the hot point belongs. The process of deriving the heat distribution direction that needs to be shifted towards the cold point side for each temperature zone and the upper and lower heating components, and generating the heat distribution direction adjustment result, is as follows: If the dominant imbalance is a delayed type, then based on the temperature zones of the cold and hot points in the heating misalignment diagram, the heat distribution direction is deduced to be the transfer of heating power from the temperature zone of the hot point to the temperature zone of the cold point along the chain speed direction. For the temperature zone of the lagging lower cold point, both the upper and lower heating components need to increase their heating power. The heat distribution direction should be adjusted so that the temperature zone of the cold point is generally increased towards the cold point. The heating power of the temperature zone of the hot point should be reduced to avoid the hot point overheating. If the dominant imbalance is of the overheating type, then based on the upper or lower heating component associated with the measuring point with the large hysteresis in the heating misalignment diagram, determine the weaker side of the upper or lower heating component. The heat distribution direction of the biased heating type is to transfer the heating power from the side with stronger effect of the upper heating component and the lower heating component to the side with weaker effect within the temperature zone of the cold point, so that the upper heating component and the lower heating component are balanced towards the cold point. If the measurement point with a large lag is mainly associated with the upper heating component under the heat-biased type, then the upper heating component is the weaker side. The power allocation of the upper heating component to the temperature zone of the cold point is increased and the power allocation of the lower heating component is reduced accordingly. If the measurement point with a large lag is mainly associated with the lower heating component under the heat-biased type, then the lower heating component is the weaker side. The power allocation of the lower heating component to the temperature zone of the cold point is increased and the power allocation of the upper heating component is reduced accordingly. It is understandable that the heat distribution direction includes axial heat distribution direction and layer heat distribution direction. Axial heat distribution direction describes the transfer of heating power along the chain speed direction to the temperature zone to which the cold point belongs, while layer heat distribution direction describes the transfer between the upper heating component and the lower heating component to the side associated with the cold point. The determined heat distribution direction is marked according to the temperature zone of the cold point and the temperature zone of the hot point, as well as the upper heating component and the lower heating component, to obtain the heat distribution direction adjustment result that can be used for coordinated adjustment in step S4; The results of the heat distribution adjustment clearly indicate the trend of increase or decrease in heating power in each temperature zone and on the cold side of the upper and lower heating components, so that the coordinated adjustment in step S4 has a directional basis; The technical solution of this invention is as follows: Temperature time-series data from measurement points on the surface of the printed circuit board inside the reflow oven are collected, aligned and stitched to form a temperature field sequence on the board surface, and the temperature range of the measurement points is extracted to obtain the spatial dispersion of the board surface temperature; the relationship between the spatial dispersion of the board surface temperature and the solder joint process window is analyzed to determine whether a non-uniform shape has formed on the board surface; the spatial temperature difference of the measurement points on the board surface is converted into a specific non-uniform shape index, transforming the determination of whether the board surface temperature is uniform from offline temperature measurement based on experience into an automated control criterion; if a non-uniform shape is formed, the heating phase comparison between measurement points and the peak arrival order are extracted to determine cold and hot points. The system obtains a relative hysteresis diagram; based on the relative hysteresis diagram and the corresponding element heat capacity labels at each measuring point, it determines the dominant imbalance type of the non-uniform shape; it quickly distinguishes between heat capacity difference-dominated and upper / lower heating imbalance-dominated, avoiding misadjustment caused by indiscriminate compensation for non-uniform shapes; based on the dominant imbalance type and the relative hysteresis diagram, it maps the spatial positions of cold and hot points to the corresponding temperature zones and upper / lower heating components, obtaining a heating misalignment diagram; it derives the heat distribution direction that each temperature zone and upper / lower heating component needs to transfer to the cold point side, generating heat distribution direction adjustment results; it locates the overall temperature difference problem to specific temperature zones and upper / lower heating components, making the heating power transfer direction clear and executable.

[0024] Example 2 Please see Figures 1-2 As shown, an intelligent optimization and control method for SMT reflow soldering temperature profile includes: S4: Based on the heat distribution adjustment results, the temperature zones and the upper and lower heating components are coordinated and adjusted to generate co-control parameters. The plate surface temperature field sequence is sampled in real time as control feedback to obtain the corrected temperature field sequence. Based on the corrected temperature field sequence, the plate surface temperature spatial dispersion is extracted again and recorded as the corrected dispersion to correct the temperature distribution in a closed loop. The process of coordinating the adjustment of each temperature zone and the upper and lower heating components based on the heat distribution adjustment results to generate co-control parameters, and obtaining the corrected temperature field sequence by real-time re-sampling of the plate surface temperature field sequence is as follows: Based on the obtained heat distribution adjustment results, the set values ​​of each temperature zone of the reflow oven and the power distribution between the upper and lower heating components in each temperature zone are adjusted in a coordinated manner. Among them, the temperature zone setting value is the temperature value given to each temperature zone of the reflow oven during the reflow soldering process, and the power allocation is the heating power value occupied by the upper heating component and the lower heating component in the same temperature zone. The temperature zone setting value and power allocation are given and executed by the control system of the reflow oven zone by zone. The coordinated adjustment refers to setting the temperature zone, power distribution between the upper and lower heating components, and chain speed all at the same time, avoiding new heating imbalances caused by adjusting only one item; The constraint is to keep the total heating power equal before and after the adjustment. That is, while increasing the heating power on one side according to the heat distribution adjustment result, the heating power on the other side is reduced by an equal amount. This allows the heating power to be transferred between temperature zones and between the upper heating component and the lower heating component without increasing the total heating power. This ensures that the cold points are heated while the hot points are not overheated. When the dominant imbalance is a lag type, the temperature setting value of the cold point's temperature zone is increased according to the axial heat distribution direction, and the power distribution of the upper heating component and the lower heating component in the cold point's temperature zone is increased simultaneously. At the same time, the temperature setting value of the hot point's temperature zone is reduced by an equal amount, and the power distribution of the upper heating component and the lower heating component in the hot point's temperature zone is reduced by an equal amount, so that the heating power is transferred from the hot point's temperature zone to the cold point's temperature zone along the chain speed direction. When the dominant imbalance is a hysteresis type, in addition to transferring the heating power according to the axial heat distribution, the chain speed is also reduced to prolong the heating time of the printed circuit board in the temperature zone of the cold point. The heating time of the printed circuit board in the temperature zone to which the cold point belongs is obtained by dividing the difference between the start and end axial coordinates of the temperature zone to which the cold point belongs, as recorded by the temperature zone layout parameters, by the chain speed. The amount of reduction in chain speed is determined by the amount of extension of the heating time of the printed circuit board in the temperature zone to which the cold point belongs, which is equal to the amount of lag of the cold point relative to the reference measuring point in the relative lag diagram. When the dominant imbalance type is the overheating type, the power distribution of the weaker side of the upper heating component and the lower heating component is increased in the temperature zone of the cold point according to the layer-to-layer heat distribution, and the power distribution of the stronger side is reduced by an equal amount. The temperature zone setting value of the cold point remains unchanged. When the dominant imbalance type is the overheating type, the lag of the cold point relative to the reference measuring point is not caused by insufficient heating time. The chain speed remains unchanged, and the heating power is transferred only in the temperature zone to which the cold point belongs to the heat distribution direction according to the layer. It should be noted that the coordinated adjustment is implemented step by step in a single-step adjustment manner. The single-step adjustment manner is the smallest adjustment increment that the reflow oven control system can distinguish for the temperature zone setpoint, power distribution and chain speed. The step-by-step adjustment ensures that the transfer of heating power does not exceed the welding point process window. Each time a coordinated adjustment is completed, the adjusted temperature zone settings, the power distribution between the upper and lower heating components in each temperature zone, and the chain speed are combined and recorded into a set of values ​​to obtain the coordinated control parameters. The control parameters are issued from the reflow oven's control system to each temperature zone and conveyor chain and take effect immediately. After the control parameters take effect, the reflow oven performs reflow soldering on the printed circuit board according to the control parameters. During the process of the printed circuit board passing through the reflow oven after the co-control parameter takes effect, the positions of the measurement points set up in step S1 and the recorded positions inside the oven remain unchanged. The thermocouples and data loggers continuously resample the temperature at each measurement point at the same time interval as in step S1 to obtain the temperature time series data of each measurement point after the co-control parameter takes effect. The temperature time series data of each measuring point obtained by resampling are classified according to their position in the furnace, and the data are spliced ​​column by column at the same sampling time with a unified sampling time sequence as the alignment benchmark. The spliced ​​data are arranged according to their position in the furnace to form a corrected temperature field sequence. Among them, the corrected temperature field sequence and the plate surface temperature field sequence have the same sampling time dimension and furnace position dimension. The spatial slice corresponding to each sampling time of the corrected temperature field sequence reflects the plate surface temperature distribution at each sampling time after the co-control parameter takes effect. The process of re-extracting the spatial dispersion of the plate surface temperature based on the corrected temperature field sequence, denoted as the corrected dispersion, is as follows: Based on the corrected temperature field sequence, the temperature difference range between measuring points is extracted in step S1. The highest and lowest temperatures among all measuring point temperature values ​​at each sampling time are extracted. The temperature difference range between measuring points at each sampling time is obtained by subtracting the lowest temperature from the highest temperature. Arrange the temperature difference ranges between the measurement points corresponding to all sampling times covered by the corrected temperature field sequence in chronological order to obtain the corrected dispersion that corresponds one-to-one with the co-control parameters. Among them, the corrected dispersion characterizes the change process of the maximum spatial temperature difference between cold and hot spots on the surface of the printed circuit board as a function of sampling time after the co-control parameters take effect; The maximum value of the temperature at the measuring point and the sampling time corresponding to the maximum value are re-found by defining the peak temperature and the plate peak time in step S1 according to the corrected temperature field sequence, and the corrected dispersion corresponding to the redefined plate peak time is obtained. It is understandable that the corrected dispersion and the plate surface temperature spatial dispersion obtained in step S1 are extracted using the same method and fall on the same sampling time sequence. The values ​​corresponding to the corrected dispersion and the plate surface temperature spatial dispersion at the plate surface peak time can be directly compared, providing a data basis for step S5 to evaluate the convergence of the temperature difference between cold and hot spots on the plate surface.

[0025] S5: Based on the correction of dispersion, evaluate the convergence deviation of cold and hot spots to obtain the temperature uniformity of the board surface; when the temperature uniformity of the board surface meets the containment relationship of the solder joint process window, output the co-control parameters as the parameters for optimizing the temperature curve. The process of obtaining the plate surface temperature uniformity based on the convergence deviation of cold and hot spots by correcting the dispersion is as follows: The value of the plate surface temperature spatial dispersion obtained in step S1 at its plate surface peak time is used as the benchmark for the maximum spatial temperature difference between cold and hot points before the co-control parameter takes effect. The value of the corrected dispersion obtained in step S4 at its plate surface peak time is used as the maximum spatial temperature difference between cold and hot points after the co-control parameter takes effect. The value of the corrected dispersion at the peak time of the plate surface is obtained by extracting the temperature difference range between the measuring points in step S1 according to the corrected temperature field sequence obtained in step S4. That is, at each sampling time, the difference between the highest and lowest temperatures among all the temperature values ​​of the measuring points is taken, and the temperature difference range between the measuring points corresponding to the newly determined peak time of the plate surface is used as the value of the corrected dispersion at the peak time of the plate surface. The difference between the maximum space temperature difference benchmark and the maximum space temperature difference is calculated, and the ratio of the difference calculation result to the maximum space temperature difference benchmark is calculated to obtain the degree of convergence of the temperature difference between the cold and hot spots on the plate. It should be noted that the greater the degree of temperature difference convergence, the more significant the effect of the co-control parameter on narrowing the temperature difference between the cold and hot points; the smaller the degree of temperature difference convergence, the weaker the effect of the co-control parameter on narrowing the temperature difference between the cold and hot points. The maximum spatial temperature difference corresponding to the peak value of the plate surface after the co-control parameter takes effect is defined as the plate surface temperature uniformity; the smaller the plate surface temperature uniformity value, the more uniform the spatial distribution of plate surface temperature. When the temperature uniformity of the board surface meets the containment relationship of the solder joint process window, the process of outputting the co-control parameters as the parameters for optimizing the temperature curve is as follows: When the temperature uniformity of the board surface meets the containment relationship of the solder joint process window, the co-control parameters obtained in step S4 are output as the parameters of the optimized temperature curve. The containment relationship of the solder joint process window is defined by the window temperature width of the solder joint process window when the temperature uniformity of the board surface is less than or equal to that of the solder joint process window. This containment relationship and the containment relationship defined in step S1 use the same window temperature width as the judgment criterion. If the temperature uniformity of the board surface is greater than the window temperature width of the solder joint process window, it is determined that the co-control parameters have not enabled the cold and hot points to enter the solder joint process window synchronously. The process returns to step S4 and continues to coordinate the temperature zone setting, the power distribution of the upper heating component and the lower heating component, and the chain speed according to the heat distribution direction, and generates new co-control parameters; so that the degree of temperature difference convergence gradually increases with each co-control adjustment. After the newly generated co-control parameters take effect, the corrected dispersion obtained by the corrected temperature field sequence is extracted again according to this step, and the temperature difference convergence degree and the temperature uniformity of the board surface are calculated. The spatial temperature difference narrowing progress characterized by the temperature difference convergence degree is used as the basis for iterative convergence until the average temperature of the board surface meets the requirements of the solder joint process window. If the temperature uniformity of the board surface is still greater than the temperature width of the solder joint process window when the number of collaborative adjustments reaches the preset maximum number of iterations, then the collaborative control parameter corresponding to the minimum temperature difference convergence degree is output as the parameter for optimizing the temperature curve. When the containment relationship of the solder joint process window is satisfied, the same solder joint process window can contain both cold and hot spots at the same temperature level. The cold and hot spots on the board surface no longer form a non-uniform shape where the maximum spatial temperature difference in the peak stage exceeds the window temperature width. The optimized temperature profile parameters are the set values ​​for each temperature zone of the reflow oven, the power distribution between the upper and lower heating components in each temperature zone, and the coordinated combination of the chain speed. This coordinated combination ensures that cold spots and hot spots fall into the solder joint process window simultaneously, thus avoiding the simultaneous occurrence of cold solder joints and component damage. After the optimized temperature curve parameters are sent to the reflow oven control system, the temperature uniformity of the board surface is converged within the window temperature width, and the spatial temperature difference between cold and hot spots on the board surface changes from a non-uniform state to a uniform state, thus improving the spatial uniformity of the board surface temperature. The technical solution of this invention is as follows: Based on the heat distribution adjustment results, each temperature zone and the upper and lower heating components are coordinated and co-control parameters are generated. The corrected temperature field sequence is obtained by real-time re-sampling of the board surface temperature field sequence. The spatial dispersion of the board surface temperature is re-extracted based on the corrected temperature field sequence and denoted as the corrected dispersion. Cold spots are compensated in a directional manner and hot spots are suppressed from overheating without increasing the total heating power, and a closed-loop iteration is formed through real-time re-sampling. The convergence degree of the temperature difference between cold spots and hot spots is evaluated based on the corrected dispersion to obtain the board surface temperature uniformity. When the board surface temperature uniformity satisfies the solder joint process window containment relationship, the co-control parameters are output as optimized temperature curve parameters. Optimized parameters are output using the solder joint process window containment relationship as the convergence criterion to ensure that cold spots and hot spots enter the process window simultaneously and to avoid incomplete soldering and thermal damage.

[0026] Example 3 Please see Figure 3 As shown, an intelligent optimization and control system for SMT reflow soldering temperature profiles includes the following modules: Temperature field anomaly detection module: Collects temperature time series data of measuring points on the surface of printed circuit board in reflow oven, aligns and splices them to form the temperature field sequence of the board surface, and extracts the temperature range of the measuring points to obtain the temperature spatial dispersion of the board surface; analyzes the containment relationship between the temperature spatial dispersion of the board surface and the solder joint process window, and determines whether the board surface has formed a non-uniform shape in order to perform temperature adjustment. Imbalance identification module: If a non-uniform shape is formed, the temperature field sequence of the plate surface is compared between the heating phases of the measuring points and the peak arrival order is extracted to determine the cold points and hot points and obtain the relative hysteresis diagram to form feedback control; based on the relative hysteresis diagram and the corresponding element heat capacity label of each measuring point, the dominant imbalance type of the non-uniform shape is determined. Heat distribution orientation module: Based on the dominant imbalance class and relative hysteresis diagram, the spatial positions of cold and hot points are mapped to the corresponding temperature zones and upper and lower heating components to obtain the heating misalignment diagram; the heat distribution direction that each temperature zone and upper and lower heating components need to be transferred to the cold point side is derived, and the heat distribution orientation adjustment result is generated; Collaborative correction module: Based on the heat distribution adjustment results, it performs collaborative adjustment on each temperature zone and the upper and lower heating components and generates collaborative control parameters. It also re-samples the plate surface temperature field sequence in real time as control feedback to obtain the corrected temperature field sequence. Based on the corrected temperature field sequence, it re-extracts the plate surface temperature spatial dispersion, which is recorded as the correction dispersion to correct the temperature distribution in a closed loop. Uniformity optimization module: Based on the correction of dispersion, the convergence deviation of cold and hot spots is evaluated to obtain the temperature uniformity of the board surface; when the temperature uniformity of the board surface meets the containment relationship of the solder joint process window, the co-control parameters are output as the optimized temperature control curve.

[0027] 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 optimization and control of SMT reflow soldering temperature profile, characterized in that: include: Temperature time-series data of measuring points on the surface of the printed circuit board in the reflow oven are collected, aligned and spliced ​​to form the temperature field sequence of the board surface, and the temperature range of the measuring points is extracted to obtain the temperature spatial dispersion of the board surface; the relationship between the temperature spatial dispersion of the board surface and the containment relationship of the solder joint process window is analyzed to determine whether the board surface has formed a non-uniform shape in order to perform temperature adjustment. If a non-uniform shape is formed, the temperature field sequence on the plate is compared between the heating phases of the measuring points and the peak arrival order is extracted to determine the cold and hot points and obtain the relative hysteresis diagram to form feedback control; based on the relative hysteresis diagram and the corresponding element heat capacity label of each measuring point, the dominant imbalance type of the non-uniform shape is determined. Based on the dominant imbalance class and the relative hysteresis diagram, the spatial locations of cold and hot points are mapped to the corresponding temperature zones and upper and lower heating components to obtain the heating misalignment diagram; Derive the heat distribution direction that each temperature zone and the upper and lower heating components need to shift towards the cold point, and generate the heat distribution direction adjustment result; Based on the heat distribution adjustment results, the temperature zones and the upper and lower heating components are coordinated and adjusted to generate co-control parameters. The plate surface temperature field sequence is sampled in real time as control feedback to obtain the corrected temperature field sequence. Based on the corrected temperature field sequence, the plate surface temperature spatial dispersion is extracted again and recorded as the corrected dispersion to correct the temperature distribution in a closed loop. Based on the correction of dispersion, the convergence deviation between cold and hot spots is evaluated to obtain the temperature uniformity of the board surface. When the temperature uniformity of the board surface meets the containment relationship of the solder joint process window, the co-control parameters are output as the optimized temperature control curve.

2. The intelligent optimization and control method for SMT reflow soldering temperature profile according to claim 1, characterized in that: The process of determining whether the board surface has formed a non-uniform shape is as follows: Temperature time series data of each measuring point is collected, and range discretization analysis is performed to obtain the spatial dispersion of the plate surface; and the maximum value of the temperature values ​​of all measuring points is selected as the peak temperature of the plate surface based on the temperature time series data, and the sampling time corresponding to the peak temperature of the plate surface is marked as the peak time of the plate surface. Obtain the spatial dispersion of the plate temperature corresponding to the peak value moment; If the spatial dispersion of the plate temperature at the peak moment is greater than the window temperature width of the solder joint process window, it is determined that the plate surface has formed a non-uniform shape with both cold and hot spots.

3. The intelligent optimization and control method for SMT reflow soldering temperature profile according to claim 2, characterized in that: The process of performing range discretization analysis is as follows: The furnace position corresponding to each measuring point is obtained, the temperature time series data of each measuring point is classified according to the furnace position, and the plate surface temperature field sequence is obtained by splicing the data column by column at the same sampling time with a unified sampling time sequence as the alignment reference. Based on the temperature field sequence of the plate, the difference between the highest and lowest temperatures of all measuring points at each sampling time is extracted as the temperature difference range between measuring points, and the plate temperature spatial dispersion is obtained by arranging them in chronological order.

4. The intelligent optimization and control method for SMT reflow soldering temperature profile according to claim 1, characterized in that: The process of identifying cold spots and hot spots and obtaining the relative lag plot is as follows: The arrival time of the peak value in the temperature sequence of each measuring point is extracted from the plate temperature field sequence, and the peak value arrival order is obtained by arranging them according to the time sequence. The measuring point with the smallest peak arrival time in the peak arrival sequence is marked as a hot spot, and the measuring point with the largest peak arrival time is marked as a cold spot, with the hot spot as the benchmark measuring point; Subtract the peak arrival time of each measuring point from the peak arrival time of the reference measuring point to obtain the hysteresis of each measuring point, and mark them according to their positions in the furnace to form a relative hysteresis diagram.

5. The intelligent optimization control method for SMT reflow soldering temperature profile according to claim 1, characterized in that: The process of determining the dominant imbalance class of a non-uniform morphology is as follows: Obtain the heat capacity category of the corresponding element at each measuring point, and divide the measuring points into the plate area corresponding to the large heat capacity element and the plate area corresponding to the small heat capacity element; If the cold spot is located in the plate area corresponding to the large heat capacity element and the hot spot is located in the plate area corresponding to the small heat capacity element, and the hysteresis of the measuring point corresponding to the large heat capacity element is generally greater than the hysteresis of the measuring point corresponding to the small heat capacity element, then the dominant imbalance type is determined to be the hysteresis type; otherwise, the dominant imbalance type is determined to be the overheating type.

6. The intelligent optimization control method for SMT reflow soldering temperature profile according to claim 1, characterized in that: The process of generating the heat distribution direction adjustment result is as follows: Based on the dominant imbalance class and the relative lag diagram, a heating misalignment diagram is obtained by spatial mapping analysis of cold spots and hot spots. If the dominant imbalance is a lag type, the heating direction is derived from the heating misalignment diagram as transferring heating power from the temperature zone of the hot spot to the temperature zone of the cold spot along the chain speed direction. If the dominant imbalance is a bias type, the component associated with the measuring point with the large lag is determined to be the weaker side, and the heating direction is to transfer heating power from the stronger side to the weaker side within the temperature zone of the cold spot. The heating direction is marked zone by zone to obtain the heating direction adjustment result.

7. The intelligent optimization control method for SMT reflow soldering temperature profile according to claim 6, characterized in that: The process of obtaining the heating misalignment diagram is as follows: Read the furnace positions and hysteresis of cold and hot spots in the relative hysteresis diagram, and obtain the temperature zone layout parameters of the start and end axial coordinates of each temperature zone along the chain speed direction. The cumulative displacement of the chain speed is calculated by multiplying the peak value of the plate surface with the chain speed. This displacement is then superimposed on the furnace positions of the cold and hot points to determine the temperature zones of the cold and hot points. Obtain the printed circuit board component layout data and extract the component placement surface, and associate the cold spots and hot spots with the upper heating components or lower heating components of their respective temperature zones; The heating misalignment diagram is obtained by marking the temperature zones of cold points and hot points, the upper or lower heating components associated with cold points and hot points, the upper or lower heating components associated with hot points, and the hysteresis between cold and hot points according to their positions in the furnace.

8. The intelligent optimization control method for SMT reflow soldering temperature profile according to claim 1, characterized in that: The process of generating co-control parameters is as follows: Based on the heat distribution adjustment results, the set values ​​of each temperature zone and the power distribution between the upper and lower heating components within the temperature zone are adjusted in a coordinated manner. The coordinated adjustment gives the temperature zone set value, power distribution and chain speed together in the same adjustment, and constrains the total heating power to remain equal before and after the adjustment. After each coordinated adjustment is completed, the adjusted temperature zone set value, power distribution and chain speed are combined and recorded as a set of values ​​to obtain the coordinated control parameters.

9. The intelligent optimization control method for SMT reflow soldering temperature profile according to claim 1, characterized in that: The process of obtaining the plate surface temperature uniformity is as follows: The maximum spatial temperature difference is generated based on the corrected dispersion and determined as the plate surface temperature uniformity.

10. The intelligent optimization control method for SMT reflow soldering temperature profile according to claim 1, characterized in that: The process of outputting co-control parameters as parameters for optimizing the temperature curve is as follows: When the temperature uniformity of the board surface is less than or equal to the window temperature width of the solder joint process window, the output co-control parameter is the optimized temperature curve parameter; If the board surface temperature is greater than the window temperature width of the solder joint process window, then continue to perform collaborative adjustments to generate new collaborative control parameters until the board surface temperature uniformity is less than or equal to the window temperature width of the solder joint process window, then output the collaborative control parameters as the optimized temperature curve parameters. If the board temperature is still greater than the window temperature width of the solder joint process window when the number of collaborative adjustments reaches the preset maximum number of iterations, then the collaborative control parameter corresponding to the minimum temperature difference convergence degree is output as the parameter for optimizing the temperature curve.

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