A post-mounting thermal field dynamic compensation SMT solder joint forming regulation system

Abstract

The application discloses a kind of SMT weld joint forming regulation and control systems of post-mounting thermal field dynamic compensation, it is related to the technical field of surface mounting technology, comprising: thermal field real-time acquisition module, the thermal field real-time acquisition module is used to continuously acquire the temperature distribution data of SMT weld joint area after mounting is completed, the temperature distribution data includes the temperature value of each space point in weld joint area and its corresponding time stamp, the temperature distribution data of weld joint area is continuously obtained by the thermal field real-time acquisition module, realizes the online, non-contact monitoring of weld joint thermal field after mounting, thermal field feature extraction and deviation calculation module compares actual thermal field with standard thermal field model point by point, can accurately locate local overheating or supercooling area, dynamic compensation regulation and control module generates local heat generation, heat dissipation or heat preservation control signal according to deviation, realizes closed-loop dynamic adjustment, significantly improve the uniformity and reliability of weld joint forming.

Description

Technical Field

[0001] This invention relates to the technical field of surface mount technology, specifically to an SMT solder joint forming control system with dynamic thermal field compensation after mounting. Background Technology

[0002] In SMT reflow soldering, the quality of solder joint formation directly determines the reliability and electrical connection performance of electronic products. Traditional reflow soldering usually adopts an overall heating method, controlling the heating, holding and cooling process of the entire PCB board through a preset temperature profile. However, with the miniaturization and high density of electronic components and the increasing complexity of PCB design, the thermal environment faced by solder joints in different areas during reflow soldering is becoming increasingly different. Especially after mounting, due to the differences in heat absorption capacity, heat dissipation conditions and component heat capacity in different locations of the PCB board, the local thermal field distribution in the solder joint area is uneven, resulting in soldering defects such as cold solder joints, tombstoning, voids and cold solder joints.

[0003] In the existing technology, some reflow soldering equipment is equipped with an oven temperature tester or thermocouple array to monitor the temperature inside the oven or the temperature of the PCB board. However, these monitoring methods are usually offline or lagging, and cannot perform real-time dynamic compensation of the local thermal field after mounting and before the solder joints are cured. In addition, some high-end equipment attempts to use hot air or infrared heating zone control, but its control strategy is based on a preset static temperature curve and fails to adaptively adjust according to the actual thermal field deviation of the solder joint area. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides an SMT solder joint forming control system with dynamic thermal field compensation after mounting. This system solves the problem that some existing reflow soldering equipment is equipped with oven temperature testers or thermocouple arrays to monitor the temperature inside the oven or the PCB surface. However, these monitoring methods are usually offline or lagging, and cannot perform real-time dynamic compensation of the local thermal field after mounting and before the solder joints solidify. In addition, some high-end equipment attempts to use hot air or infrared heating zone control, but their control strategies are based on preset static temperature curves and fail to adaptively adjust according to the actual thermal field deviation in the solder joint area.

[0005] To achieve the above objectives, the present invention provides the following technical solution: an SMT solder joint forming control system with dynamic thermal field compensation after mounting, comprising: The real-time thermal field acquisition module is used to continuously acquire temperature distribution data of the SMT solder joint area after the mounting is completed. The temperature distribution data includes the temperature value of each spatial point in the solder joint area and its corresponding timestamp. A thermal field feature extraction module is connected to the real-time thermal field acquisition module and is used to extract thermal field features of the solder joint area from the temperature distribution data. The thermal field features include at least temperature gradient features and peak temperature features. A thermal field deviation calculation module is connected to the thermal field feature extraction module. It is used to compare the extracted thermal field features with a preset standard thermal field model point by point or region by point to calculate the thermal field deviation. The thermal field deviation includes temperature amplitude deviation, temperature gradient deviation and temperature rise rate deviation. A dynamic compensation and control module is connected to the thermal field deviation calculation module. It is used to generate a dynamic compensation control signal based on the thermal field deviation and send the dynamic compensation control signal to the thermal compensation execution interface to adjust the local heat input or heat output of the solder joint area in real time so that the actual solder joint thermal field approaches the standard thermal field model.

[0006] In some embodiments, the real-time thermal field acquisition module includes an infrared thermal imaging acquisition unit. The infrared thermal imaging acquisition unit acquires infrared radiation images of the solder joint area at a sampling frequency of not less than a preset frame rate, and converts them into a temperature matrix through radiation calibration. The row and column indices of the temperature matrix correspond to the spatial coordinates of the solder joint area.

[0007] In some embodiments, the thermal field feature extraction module includes: A temperature gradient calculation unit is used to calculate the magnitude and direction angle of the temperature gradient along the transverse, longitudinal and diagonal directions within the solder joint area; A peak temperature detection unit is used to identify the highest temperature value of each solder joint within the solder joint area and its arrival time. A thermal field feature vector generation unit is used to combine the temperature gradient magnitude, orientation angle, peak temperature and arrival time into a multidimensional thermal field feature vector.

[0008] In some embodiments, the standard thermal field model is a set of spatiotemporal temperature distribution curves corresponding to the ideal solder joint formation obtained in advance through process experiments or simulations. The standard thermal field model includes multiple temperature ranges and the allowable temperature deviation threshold for each range.

[0009] In some embodiments, the thermal field deviation calculation module includes: A region segmentation unit is used to align the actual collected temperature distribution data with the standard thermal field model according to the solder joint location; The point-by-point deviation calculation unit is used to calculate the temperature amplitude deviation, temperature gradient deviation, and temperature rise rate deviation of each spatial point in each zone, and to perform weighted summation according to preset weighting coefficients to obtain the comprehensive thermal field deviation of each zone. A global deviation fusion unit is used to weight and fuse the comprehensive thermal field deviation of each zone according to the solder joint density to obtain the global thermal field deviation.

[0010] In some embodiments, the dynamic compensation and control module includes: The compensation strategy generation unit is used to match the corresponding compensation mode from the preset compensation rule library according to the sign and magnitude of the thermal field deviation. The compensation mode includes local heating mode, local heat dissipation mode and heat preservation mode. The compensation calculation unit is used to input the thermal field deviation into the pre-trained thermal compensation control model and output the thermal compensation power or thermal compensation duration of each compensation region. The compensation instruction encoding unit is used to encapsulate the thermal compensation power or thermal compensation duration into the dynamic compensation control signal and send it to the thermal compensation execution interface.

[0011] In some embodiments, the pre-trained thermal compensation control model is a closed-loop control model constructed based on a PID control algorithm or a fuzzy logic control algorithm. The input of the model is the thermal field deviation and the rate of change of the deviation, and the output is the compensation power correction value or the compensation time correction value.

[0012] In some embodiments, a thermal field prediction and compensation module is further included. The thermal field prediction and compensation module is connected to the thermal field deviation calculation module and is used to calculate the predicted thermal field deviation at the next sampling time based on the thermal field deviation sequence of multiple consecutive sampling times before the current time using a time series prediction algorithm, and send the predicted thermal field deviation to the dynamic compensation and control module in advance to generate a feedforward compensation control signal.

[0013] In some embodiments, a thermal field quality assessment module is also included, which is used to calculate the thermal field control quality factor based on the historical data of thermal field deviation recorded during the entire post-mounting thermal field control process after the solder joint is cured, compare the thermal field control quality factor with a preset qualified threshold, and output a solder joint forming quality level signal.

[0014] In some embodiments, a thermal field model self-learning module is also included, which is used to collect actual temperature distribution data and corresponding final solder joint forming quality indicators during the thermal field control process after each mounting, and to use machine learning algorithms to iteratively optimize the standard thermal field model and update the temperature threshold and allowable deviation range in the model.

[0015] Beneficial Effects: This invention provides an SMT solder joint forming control system with dynamic thermal field compensation after placement. It solves the problem that some existing reflow soldering equipment is equipped with oven temperature testers or thermocouple arrays to monitor the oven temperature or PCB surface temperature. However, these monitoring methods are usually offline or lagging, unable to provide real-time dynamic compensation for local thermal fields after placement and before solder joint curing. Furthermore, some high-end equipment attempts to use hot air or infrared heating zone control, but their control strategies are based on preset static temperature curves and fail to adaptively adjust according to the actual thermal field deviation in the solder joint area. This invention continuously acquires temperature distribution data of the solder joint area through a real-time thermal field acquisition module, realizing online, non-contact monitoring of the solder joint thermal field after placement. The thermal field feature extraction and deviation calculation module compares the actual thermal field with a standard... The thermal field model performs point-by-point comparisons to accurately locate local overheated or undercooled areas. The dynamic compensation and control module generates local heating, heat dissipation, or heat preservation control signals based on the deviation, achieving closed-loop dynamic adjustment and significantly improving the uniformity and reliability of solder joint formation. By introducing predictive compensation and self-learning mechanisms, the thermal field model self-learning module collects actual temperature distribution data and final solder joint formation quality indicators during the thermal field control process after each mounting. Iterative optimization of the standard thermal field model is performed using machine learning algorithms, updating the temperature thresholds and allowable deviation ranges in the model. This mechanism enables the system to adapt to the optimal thermal field settings under different PCB layouts, different component combinations, and different environmental conditions. With the accumulation of production data, the system's control accuracy and adaptability continue to improve, demonstrating a high level of intelligence and significant application value. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the overall structure of the SMT solder joint forming control system with dynamic thermal field compensation after mounting as described in Embodiment 1 of the present invention.

[0017] Figure 2 This is a schematic diagram of the internal structure of the thermal field deviation calculation module described in Embodiment 2 of the present invention.

[0018] Figure 3 This is a schematic diagram of the control logic of the dynamic compensation and control module described in Embodiment 3 of the present invention.

[0019] Figure 4 This is a schematic diagram of the control logic including the thermal field prediction and compensation module as described in Embodiment 4 of the present invention.

[0020] Figure 5 This is a schematic diagram of the control logic including the thermal field quality assessment module as described in Embodiment 5 of the present invention.

[0021] Figure 6 This is a schematic diagram of the control logic including the thermal field model self-learning module as described in Embodiment Six of the present invention.

[0022] 100. Real-time thermal field acquisition module; 200. Thermal field feature extraction module; 300. Thermal field deviation calculation module; 310. Region segmentation unit; 320. Point-by-point deviation calculation unit; 330. Global deviation fusion unit; 400. Dynamic compensation and control module; 410. Compensation strategy generation unit; 420. Compensation amount calculation unit; 430. Compensation command encoding unit; 500. Thermal field prediction and compensation module; 600. Thermal field quality assessment module; 700. Thermal field model self-learning module; 800. Standard thermal field model. Detailed Implementation

[0023] 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.

[0024] Example 1: According to the appendix of the instruction manual Figure 1 It is known that a dynamic thermal compensation SMT solder joint forming control system after mounting includes: The real-time thermal field acquisition module is used to continuously acquire temperature distribution data of the SMT solder joint area after the mounting is completed. The temperature distribution data includes the temperature value of each spatial point in the solder joint area and its corresponding timestamp. The thermal field feature extraction module is connected to the real-time thermal field acquisition module and is used to extract the thermal field features of the solder joint area from the temperature distribution data. The thermal field features include at least temperature gradient features and peak temperature features. The thermal field deviation calculation module is connected to the thermal field feature extraction module. It is used to compare the extracted thermal field features with the preset standard thermal field model point by point or region to calculate the thermal field deviation. The thermal field deviation includes temperature amplitude deviation, temperature gradient deviation and temperature rise rate deviation. The dynamic compensation and control module is connected to the thermal field deviation calculation module. It is used to generate a dynamic compensation control signal based on the thermal field deviation and send the dynamic compensation control signal to the thermal compensation execution interface to adjust the local heat input or heat output of the solder joint area in real time, so that the actual solder joint thermal field approaches the standard thermal field model.

[0025] In some embodiments, the real-time thermal field acquisition module includes an infrared thermal imaging acquisition unit. The infrared thermal imaging acquisition unit acquires infrared radiation images of the solder joint area at a sampling frequency of not less than a preset frame rate, and converts them into a temperature matrix through radiation calibration. The row and column indices of the temperature matrix correspond to the spatial coordinates of the solder joint area.

[0026] In some embodiments, the thermal field feature extraction module includes: The temperature gradient calculation unit is used to calculate the magnitude and direction angle of the temperature gradient along the transverse, longitudinal, and diagonal directions within the solder joint area. Peak temperature detection unit: The peak temperature detection unit is used to identify the highest temperature value of each solder joint in the solder joint area and its arrival time. The thermal field feature vector generation unit is used to combine the temperature gradient magnitude, orientation angle, peak temperature and arrival time into a multidimensional thermal field feature vector.

[0027] This embodiment describes the core workflow of the system.

[0028] First, the real-time thermal field acquisition module employs an infrared thermal imaging unit. During the critical period after mounting and before solder joint curing, the infrared thermal imager continuously captures infrared radiation images of the solder joint area at a preset frame rate. Through blackbody calibration, the radiation intensity of each pixel is converted into a temperature value, forming a temperature matrix T(x,y,t), where x and y are spatial coordinates, and t is the sampling time. The temperature distribution data includes the temperature values ​​of each spatial point within the solder joint area and their corresponding timestamps.

[0029] After receiving the temperature matrix, the thermal field feature extraction module uses its internal temperature gradient calculation unit to calculate the temperature gradient magnitude G(x,y,t) and direction angle θ(x,y,t) of each pixel along the horizontal (x-direction), vertical (y-direction), and diagonal directions using the Sobel operator or the central difference method. The peak temperature detection unit traverses the pixel region corresponding to each solder joint, identifying the highest temperature value T_peak and its arrival time t_peak during the entire heating process. The thermal field feature vector generation unit combines the above parameters into a multi-dimensional thermal field feature vector F(t). F(t)=[G_x(t),G_y(t),G_diag(t),θ(t),T_peak,t_peak] Where G_x(t), G_y(t), and G_diag(t) are the regional mean values ​​of the temperature gradient magnitudes in the horizontal, vertical, and diagonal directions, respectively. This eigenvector comprehensively describes the transient thermal field characteristics of the solder joint region.

[0030] The thermal field deviation calculation module compares the extracted thermal field features with a preset standard thermal field model. The standard thermal field model is a set of spatiotemporal temperature distribution curves corresponding to ideal solder joint formation, obtained through numerous process experiments or finite element simulations. It includes multiple temperature zones (e.g., preheating zone, reflow zone, cooling zone) and the allowable temperature deviation threshold for each zone. The deviation calculation module calculates the temperature amplitude deviation ΔT(x,y,t) = T_actual(x,y,t) - T_standard(x,y,t), the temperature gradient deviation ΔG(x,y,t), and the temperature rise rate deviation ΔR(x,y,t) point by point. The temperature rise rate is obtained through time difference: R(x,y,t) = (T(x,y,t) - T(x,y,t - Δt)) / Δt. These deviations constitute the set of thermal field deviations.

[0031] After receiving the thermal field deviation, the dynamic compensation and control module generates a dynamic compensation control signal. Specifically, the compensation strategy generation unit determines the mode based on the sign and magnitude of ΔT: if ΔT is negative and its absolute value exceeds a threshold, it matches the "local heating mode"; if ΔT is positive and exceeds a threshold, it matches the "local heat dissipation mode"; if the deviation is within the allowable range, it matches the "heat preservation mode". The compensation amount calculation unit uses a pre-trained PID control model, with ΔT and the deviation change rate d(ΔT) / dt as inputs, and outputs the thermal compensation power correction value ΔP or the compensation duration Δt_comp. The compensation instruction encoding unit encapsulates these parameters into control signals and sends them to the thermal compensation execution interface, thereby adjusting the local thermal input or output of the solder joint area in real time.

[0032] Example 2: According to the appendix of the instruction manual Figure 2 It is known that in some embodiments, the standard thermal field model is a set of spatiotemporal temperature distribution curves corresponding to the ideal solder joint formation obtained in advance through process experiments or simulations. The standard thermal field model includes multiple temperature ranges and the allowable temperature deviation threshold for each range.

[0033] In some embodiments, the thermal field deviation calculation module includes: The region segmentation unit is used to align the actual collected temperature distribution data with the standard thermal field model according to the location of the solder joints. The point-by-point deviation calculation unit is used to calculate the temperature amplitude deviation, temperature gradient deviation, and temperature rise rate deviation of each spatial point in each zone, and to perform weighted summation according to preset weighting coefficients to obtain the comprehensive thermal field deviation of each zone. The global deviation fusion unit is used to weight and fuse the comprehensive thermal field deviation of each zone according to the solder joint density to obtain the global thermal field deviation.

[0034] This embodiment further describes the structure of the standard thermal field model and the internal implementation of the thermal field deviation calculation module.

[0035] The standard thermal field model M_std is a structured dataset that defines an ideal temperature profile T_i_std(t) for each solder joint i, including the target temperature value and upper and lower thresholds T_i_low(t) and T_i_high(t) on the time axis. The model also includes the maximum allowable temperature gradient G_i_max and the optimal temperature rise rate R_i_opt for each solder joint. The temperature zones in the model are divided based on the solder paste activation temperature and alloy melting point, such as a preheating zone (room temperature to 150°C), a homogenizing zone (150°C to 200°C), a reflow zone (above the melting point of 217°C), and a cooling zone (below 150°C).

[0036] The thermal field deviation calculation module includes a region segmentation unit, a point-by-point deviation calculation unit, and a global deviation fusion unit. The region segmentation unit uses the solder joint coordinates from the PCB design file to align the actually acquired temperature matrix T_actual(x,y,t) with the standard thermal field model according to the solder joint positions, with each solder joint corresponding to a pixel sub-region. The point-by-point deviation calculation unit calculates the following deviation within each partition for each sampling time t: Temperature amplitude deviation: ΔT_i(t) = T_i_actual(t) - T_i_std(t) Temperature gradient deviation: ΔG_i(t) = G_i_actual(t) - G_i_max (only included if greater than zero) Temperature rise rate deviation: ΔR_i(t) = R_i_actual(t) - R_i_opt Then, by weighting and summing according to the preset weighting coefficients w_T, w_G, and w_R, the comprehensive thermal field deviation E_i(t) of the i-th solder joint region is obtained: E_i(t)=w_T·ΔT_i(t)+w_G·max(ΔG_i(t),0)+w_R·ΔR_i(t) Where w_T+w_G+w_R=1. The global deviation fusion unit calculates the global thermal field deviation E_global(t) based on the density factor ρ_i (e.g., the number of solder joints per unit area) of each solder joint region: E_global(t)=(∑ρ_i·E_i(t)) / ∑ρ_i This global deviation is used to trigger adjustments to the overall compensation strategy.

[0037] Example 3: According to the appendix of the instruction manual Figure 3 It is understood that, in some embodiments, the dynamic compensation and control module includes: The compensation strategy generation unit is used to match the corresponding compensation mode from the preset compensation rule library according to the sign and magnitude of the thermal field deviation. The compensation modes include local heating mode, local heat dissipation mode and heat preservation mode. The compensation calculation unit is used to input the thermal field deviation into the pre-trained thermal compensation control model and output the thermal compensation power or thermal compensation duration of each compensation region. The compensation instruction encoding unit is used to encapsulate the thermal compensation power or thermal compensation duration into a dynamic compensation control signal and send it to the thermal compensation execution interface.

[0038] In some embodiments, the pre-trained thermal compensation control model is a closed-loop control model constructed based on a PID control algorithm or a fuzzy logic control algorithm. The input of the model is the thermal field deviation and the rate of change of the deviation, and the output is the compensation power correction value or the compensation time correction value.

[0039] This embodiment describes in detail the generation of compensation strategies, calculation of compensation amounts, and instruction encoding in the dynamic compensation control module.

[0040] The compensation strategy generation unit has a built-in compensation rule base, which is stored in an "if-then" format. For example: If ΔT_i(t) < -5℃ and the duration exceeds 0.5 seconds, then the mode is "local heating" and the target area is the area around solder joint i.

[0041] If ΔT_i(t) > +8℃, then the mode is "local heat dissipation".

[0042] If |ΔT_i(t)| < 2℃ and |ΔR_i(t)| < 1℃ / s, then the mode is "heat preservation".

[0043] The compensation calculation unit employs a fuzzy logic control model. The input variables are ΔT and d(ΔT) / dt, which are divided into fuzzy subsets (e.g., negative large, negative small, zero, positive small, positive large). The output variable is either the compensation power correction value ΔP (duty cycle) or the compensation duration Δt_comp (milliseconds). A fuzzy rule is, for example, that if both ΔT and d(ΔT) / dt are negative large, then ΔP is positive large. The accurate compensation amount is obtained through defuzzification (e.g., the centroid method). This model is pre-trained or designed offline and is capable of adapting to nonlinear thermal processes.

[0044] The compensation command encoding unit combines ΔP or Δt_comp with the target area address and the action time into a standard format control data packet, which is then sent to the thermal compensation execution interface via a fieldbus (such as RS485, CAN, or Ethernet). The execution interface is responsible for driving the corresponding heat source or cooling source to operate.

[0045] Example 4: According to the appendix of the instruction manual Figure 4 It is understood that in some embodiments, a thermal field prediction and compensation module is also included. The thermal field prediction and compensation module is connected to the thermal field deviation calculation module and is used to calculate the predicted thermal field deviation at the next sampling time based on the thermal field deviation sequence of multiple consecutive sampling times before the current time using a time series prediction algorithm, and send the predicted thermal field deviation to the dynamic compensation and control module in advance to generate a feedforward compensation control signal.

[0046] This embodiment adds a thermal field prediction and compensation module. This module is connected to the thermal field deviation calculation module and reads the thermal field deviation sequence {E_global(tk·Δt)} from N consecutive sampling times (e.g., N=5) prior to the current time, k=1...N. Using a time series prediction algorithm—Autoregressive Moving Average (ARMA) model or simple linear extrapolation—it predicts the global thermal field deviation E_global_pre(t+Δt) at the next sampling time. The prediction formula can be expressed as: E_global_pre(t+Δt)=a1·E_global(t)+a2·E_global(t-Δt)+...+aN·E_global(t-(N-1)Δt) The coefficients a1...aN are obtained through least-squares fitting of historical data. The predicted deviation is sent to the dynamic compensation and control module in advance, which generates a feedforward compensation control signal C_ff based on this deviation. This signal is then superimposed with the feedback compensation signal C_fb based on the current deviation to form the total control signal C_total = C_fb + C_ff. Feedforward compensation can effectively overcome the large hysteresis characteristic of the thermal system and shorten the response time.

[0047] Example 5: According to the appendix of the instruction manual Figure 5 It is understood that in some embodiments, a thermal field quality assessment module is also included, which is used to calculate the thermal field control quality factor based on the historical data of thermal field deviation recorded during the entire post-mounting thermal field control process after the solder joint is cured, and compare the thermal field control quality factor with the preset qualified threshold, and output the solder joint forming quality level signal.

[0048] This embodiment adds a thermal field quality assessment module. After the solder joints have cured (i.e., the entire thermal compensation and control cycle has ended), this module reads the stored historical records of thermal field deviations and calculates the thermal field control quality factor Q. One calculation method is as follows: Q=1-(1 / T_total)∫[|ΔT(t)| / ΔT_max+|ΔR(t)| / ΔR_max]dt Where T_total is the total control time, and ΔT_max and ΔR_max are the maximum allowable deviations. Q ranges from 0 to 1, with a larger value indicating better control effect. Q is compared with a preset qualified threshold Q_th (e.g., 0.85): if Q ≥ Q_th, an "excellent" level signal is output; if Q is between 0.7 and 0.85, a "qualified" level signal is output; if Q < 0.7, a "unqualified" level signal is output, and an alarm is sent to the host computer, prompting the operator to check the process parameters or equipment status.

[0049] Example 6: According to the appendix of the instruction manual Figure 6 It is understood that in some embodiments, a thermal field model self-learning module is also included, which is used to collect the actual temperature distribution data and the corresponding final solder joint forming quality index during the thermal field control process after each mounting, and to use machine learning algorithms to iteratively optimize the standard thermal field model and update the temperature threshold and allowable deviation range in the model.

[0050] This embodiment adds a self-learning module for the thermal field model. This module collects the actual temperature distribution data T_actual(x,y,t) during the thermal field control process after each mounting, as well as the final solder joint forming quality index M_quality (such as solder joint void rate, wetting angle, shear strength, etc., which can be obtained through AOI or X-ray inspection). A mapping model from actual thermal field characteristics to forming quality is established using machine learning algorithms (such as neural networks or random forests). Then, with the goal of maximizing the output of high-quality solder joints, the parameters such as temperature threshold and allowable deviation range in the standard thermal field model are iteratively optimized. Specifically, the loss function Loss=1-Q_avg is defined, where Q_avg is the average quality factor of all solder joints in the batch, and the optimal combination of model parameters is searched using Bayesian optimization or a genetic algorithm. The updated standard thermal field model automatically replaces the old version for production control in subsequent batches. The self-learning module enables the system to adapt to the optimal thermal field settings under different products and environmental conditions, achieving intelligent adaptive control.

[0051] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, the phrase "comprising an element defined as..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes the element.

[0052] It is worth noting that all standard parts used in this invention can be purchased from the market, and irregularly shaped parts can be customized according to the description and drawings. The specific connection methods of each part all adopt conventional methods such as bolts, rivets, and welding that are mature in the prior art. The models of electrical structure equipment involved can be selected according to the user's needs, as long as they meet the requirements of this application. In addition, the circuit connection adopts conventional connection methods in the prior art. The supporting electrical structures such as the control, current detection, position feedback, predictive voltage synchronization, and parameter adjustment of the electrical equipment are all existing technologies, such as PLC controllers and module structures, so they will not be described in detail here.

[0053] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A dynamic thermal field compensation system for SMT solder joint forming control after mounting, characterized in that, include: The real-time thermal field acquisition module is used to continuously acquire temperature distribution data of the SMT solder joint area after the mounting is completed. The temperature distribution data includes the temperature value of each spatial point in the solder joint area and its corresponding timestamp. A thermal field feature extraction module is connected to the real-time thermal field acquisition module and is used to extract thermal field features of the solder joint area from the temperature distribution data. The thermal field features include at least temperature gradient features and peak temperature features. A thermal field deviation calculation module is connected to the thermal field feature extraction module. It is used to compare the extracted thermal field features with a preset standard thermal field model point by point or region by point to calculate the thermal field deviation. The thermal field deviation includes temperature amplitude deviation, temperature gradient deviation and temperature rise rate deviation. A dynamic compensation and control module is connected to the thermal field deviation calculation module. It is used to generate a dynamic compensation control signal based on the thermal field deviation and send the dynamic compensation control signal to the thermal compensation execution interface to adjust the local heat input or heat output of the solder joint area in real time so that the actual solder joint thermal field approaches the standard thermal field model.

2. The SMT solder joint forming control system with dynamic thermal field compensation after mounting according to claim 1, characterized in that, The real-time thermal field acquisition module includes an infrared thermal imaging acquisition unit. The infrared thermal imaging acquisition unit acquires infrared radiation images of the solder joint area at a sampling frequency of not less than a preset frame rate, and converts them into a temperature matrix through radiation calibration. The row and column indices of the temperature matrix correspond to the spatial coordinates of the solder joint area.

3. The SMT solder joint forming control system with dynamic thermal field compensation after mounting according to claim 1, characterized in that, The thermal field feature extraction module includes: A temperature gradient calculation unit is used to calculate the magnitude and direction angle of the temperature gradient along the transverse, longitudinal and diagonal directions within the solder joint area; A peak temperature detection unit is used to identify the highest temperature value of each solder joint within the solder joint area and its arrival time. A thermal field feature vector generation unit is used to combine the temperature gradient magnitude, orientation angle, peak temperature and arrival time into a multidimensional thermal field feature vector.

4. The SMT solder joint forming control system with dynamic thermal field compensation after mounting according to claim 1, characterized in that, The standard thermal field model is a set of spatiotemporal temperature distribution curves corresponding to the ideal solder joint formation obtained in advance through process experiments or simulations. The standard thermal field model includes multiple temperature ranges and the allowable temperature deviation threshold for each range.

5. The SMT solder joint forming control system with dynamic thermal field compensation after mounting according to claim 4, characterized in that, The thermal field deviation calculation module includes: A region segmentation unit is used to align the actual collected temperature distribution data with the standard thermal field model according to the solder joint location; The point-by-point deviation calculation unit is used to calculate the temperature amplitude deviation, temperature gradient deviation, and temperature rise rate deviation of each spatial point in each zone, and to perform weighted summation according to preset weighting coefficients to obtain the comprehensive thermal field deviation of each zone. A global deviation fusion unit is used to weight and fuse the comprehensive thermal field deviation of each zone according to the solder joint density to obtain the global thermal field deviation.

6. The SMT solder joint forming control system with dynamic thermal field compensation after mounting according to claim 1, characterized in that, The dynamic compensation and control module includes: The compensation strategy generation unit is used to match the corresponding compensation mode from the preset compensation rule library according to the sign and magnitude of the thermal field deviation. The compensation mode includes local heating mode, local heat dissipation mode and heat preservation mode. The compensation calculation unit is used to input the thermal field deviation into the pre-trained thermal compensation control model and output the thermal compensation power or thermal compensation duration of each compensation region. The compensation instruction encoding unit is used to encapsulate the thermal compensation power or thermal compensation duration into the dynamic compensation control signal and send it to the thermal compensation execution interface.

7. The SMT solder joint forming control system with dynamic thermal field compensation after mounting according to claim 6, characterized in that, The pre-trained thermal compensation control model is a closed-loop control model built based on PID control algorithm or fuzzy logic control algorithm. The input of the model is the thermal field deviation and the rate of change of deviation, and the output is the compensation power correction value or the compensation time correction value.

8. The SMT solder joint forming control system with dynamic thermal field compensation after mounting according to claim 1, characterized in that, It also includes a thermal field prediction and compensation module, which is connected to the thermal field deviation calculation module. The thermal field prediction and compensation module is used to calculate the predicted thermal field deviation at the next sampling time based on the thermal field deviation sequence of multiple consecutive sampling times before the current time using a time series prediction algorithm, and send the predicted thermal field deviation to the dynamic compensation and control module in advance to generate a feedforward compensation control signal.

9. The SMT solder joint forming control system with dynamic thermal field compensation after mounting according to claim 1, characterized in that, It also includes a thermal field quality assessment module, which is used to calculate the thermal field control quality factor based on the historical data of thermal field deviation recorded during the entire post-mounting thermal field control process after the solder joint is cured, and compare the thermal field control quality factor with the preset qualified threshold to output the solder joint forming quality level signal.

10. The SMT solder joint forming control system with dynamic thermal field compensation after mounting according to claim 1, characterized in that, It also includes a thermal field model self-learning module, which is used to collect the actual temperature distribution data and the corresponding final solder joint forming quality index during the thermal field control process after each mounting, and to use machine learning algorithms to iteratively optimize the standard thermal field model and update the temperature threshold and allowable deviation range in the model.

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