Method, system and equipment for monitoring solder paste printing result of PCB (Printed Circuit Board) and medium

Abstract

The invention discloses a PCB solder paste printing result monitoring method, system and device and a medium, and relates to the technical field of data processing, and the method comprises the steps: obtaining a solder paste printing area, a first detection point location and a second detection point location, obtaining infrared information, obtaining a preset time period, and obtaining a first moment and a second moment; acquiring a first infrared temperature, a second infrared temperature, a first thermal change index, a third infrared temperature, a fourth infrared temperature and a second thermal change index; acquiring a fluctuation index, acquiring a basic index range, and acquiring a target index range; and obtaining a first heat conduction index according to the first infrared temperature and the third infrared temperature, obtaining a second heat conduction index according to the second infrared temperature and the fourth infrared temperature, and obtaining a solder paste printing result according to the first heat conduction index, the second heat conduction index and the target index range. The method has the advantages of non-contact monitoring, high precision and self-adaptive threshold adjustment.

Description

Technical Field

[0001] The present invention relates to the field of data processing technology, and in particular to a method, system, equipment and medium for monitoring PCB solder paste printing results. Background Art

[0002] In the printed circuit board (PCB) manufacturing process, the quality of solder paste printing directly affects the reliability of subsequent patch soldering and product life.

[0003] Traditional solder paste printing monitoring relies primarily on offline contact measurement or optical imaging methods, such as laser thickness gauges, confocal microscopes, or automated optical inspection equipment. However, these technologies have significant limitations: contact probes can easily cause solder paste deformation or contamination on high-speed production lines, damaging delicate pad structures. Optical inspection is sensitive to differences in reflectivity between transparent and matte solder paste materials, particularly in the area of ​​miniaturized BGA (ball grid array) or QFN (quad flat no-lead) packages. Light diffraction and shadowing can lead to high errors in 3D contour reconstruction, affecting monitoring results. Furthermore, existing technologies cannot achieve real-time closed-loop monitoring of the printing process, requiring only post-printing spot checks. This can lead to hidden defects such as bridging and cold solder joints in defective products after they enter the reflow process, resulting in high rework rates and material waste. Finally, while recently developed infrared thermal imaging technology can acquire temperature field distributions contactlessly, existing methods rely solely on single-point absolute temperature values ​​or fixed thresholds, failing to consider the dynamic coupling between solder paste thickness and thermal conductivity. These limitations hinder existing technologies from meeting the solder paste printing thickness requirements of high-end PCBs, such as those used in 5G communication modules and automotive electronics. Summary of the Invention

[0004] In view of the defects in the prior art, the present invention provides a PCB solder paste printing result monitoring method, system, equipment and medium.

[0005] A method for monitoring PCB solder paste printing results includes: obtaining a solder paste printing area and a first detection point and a second detection point located within the solder paste printing area, obtaining infrared information of infrared light directed toward the first detection point, obtaining a preset time period based on the infrared information, and obtaining a first moment and a second moment separated by the preset time period; obtaining a first infrared temperature at the first detection point at a first moment, obtaining a second infrared temperature at the first detection point at a second moment, obtaining a first thermal change index based on a first change model, the first infrared temperature, and the second infrared temperature, obtaining a third infrared temperature at the second detection point at the first moment, obtaining a fourth infrared temperature at the second detection point at the second moment, and obtaining a second thermal change index based on a second change model, the third infrared temperature, and the fourth infrared temperature; obtaining a fluctuation index based on the first thermal change index and the second thermal change index, obtaining a basic index range, and obtaining a target index range based on the fluctuation index and the basic index range; obtaining a first thermal conductivity index based on the first infrared temperature and the third infrared temperature, obtaining a second thermal conductivity index based on the second infrared temperature and the fourth infrared temperature, and obtaining a solder paste printing result based on the first thermal conductivity index, the second thermal conductivity index, and the target index range.

[0006] Optionally, the first change model (direct heating, direct infrared light) in obtaining the first thermal change index based on the first change model, the first infrared temperature, and the second infrared temperature is expressed as: ;in, is the first thermal change indicator, is the first infrared temperature, is the second infrared temperature, The preset time period.

[0007] Optionally, the second change model (indirect heat reception, heat conduction) in obtaining the second thermal change index based on the second change model, the third infrared temperature, and the fourth infrared temperature is expressed as: ;in, is the second thermal change index, is the third infrared temperature, is the fourth infrared temperature, For the preset time period, is the temperature of infrared light, is the distance between the first detection point and the second detection point.

[0008] Optionally, the fluctuation index is obtained according to the first thermal change index and the second thermal change index as follows: ;in, is a volatility indicator, is the first thermal change indicator, is the second thermal change index, is the scaling factor.

[0009] Optionally, obtaining the target indicator range based on the fluctuation indicator and the basic indicator range includes: obtaining the basic minimum indicator and the basic maximum indicator based on the basic indicator range; obtaining the target minimum indicator based on the fluctuation indicator and the basic minimum indicator, and obtaining the target maximum indicator based on the fluctuation indicator and the basic maximum indicator; obtaining the target indicator range based on the target minimum indicator and the target maximum indicator.

[0010] Optionally, the first thermal conductivity index is obtained according to the first infrared temperature and the third infrared temperature as follows: ;in, is the first heat conduction index, is the thermal conductivity of solder paste, is the first infrared temperature, is the third infrared temperature and, is the solder paste density, is the specific heat capacity of solder paste, is the distance between the first detection point and the second detection point, The preset time period.

[0011] Optionally, obtaining the solder paste printing result based on the first thermal conductivity index, the second thermal conductivity index and the target thermal conductivity threshold includes: determining whether the first thermal conductivity index and the second thermal conductivity index are both within the target index range; if so, determining that the solder paste printing has no thickness defects; if not, determining that the solder paste printing has thickness defects.

[0012] A PCB solder paste printing result monitoring system is also provided, the system comprising: an acquisition module for acquiring a solder paste printing area and a first detection point and a second detection point located in the solder paste printing area, and acquiring infrared information of infrared light directed to the first detection point, and acquiring a preset time period according to the infrared information, and acquiring a first moment and a second moment separated by the preset time period; a first data processing module for acquiring a first infrared temperature at the first detection point at a first moment, and acquiring a second infrared temperature at the first detection point at a second moment, acquiring a first thermal change index based on a first change model, the first infrared temperature and the second infrared temperature, and acquiring a first thermal change index at the second detection point at the first moment. Take the third infrared temperature, and obtain the fourth infrared temperature at the second detection point at the second moment, and obtain the second thermal change index based on the second change model, the third infrared temperature and the fourth infrared temperature; the second data processing module is used to obtain the fluctuation index according to the first thermal change index and the second thermal change index, and obtain the basic index range, and obtain the target index range according to the fluctuation index and the basic index range; the monitoring module is used to obtain the first thermal conduction index according to the first infrared temperature and the third infrared temperature, and obtain the second thermal conduction index according to the second infrared temperature and the fourth infrared temperature, and obtain the solder paste printing result according to the first thermal conduction index, the second thermal conduction index and the target index range.

[0013] The beneficial effects of the present invention are embodied in: In the entire PCB solder paste printing result monitoring method, the innovative non-contact infrared thermal conduction dynamic coupling analysis method is used to effectively solve the problems of contamination risk, reflectivity sensitivity, lack of real-time performance, and lack of thickness-heat conduction correlation in traditional solder paste printing monitoring technology. First, based on the synchronous acquisition and dynamic modeling of the spatiotemporal temperature field of dual detection points, a high-precision inversion of the solder paste thickness distribution is achieved: the direct heating characteristics of the first detection point accurately reflect the heat absorption efficiency of the material, and the indirect heating behavior of the second detection point analyzes the spatial attenuation law of the heat diffusion path. The two work together to eliminate the environmental interference error of a single detection point; further, through the adaptive time window adjustment mechanism driven by infrared spectral characteristics, it is compatible with the thermal response characteristics of different solder paste materials (such as high-absorbency silver-containing solder paste and low-absorbency lead-free solder paste), and the thickness-sensitive thermal conduction transient characteristics are captured in a wide time domain range from milliseconds to seconds. The system overcomes the signal distortion problem caused by the traditional fixed sampling frequency. Furthermore, a two-layer evaluation architecture of fluctuation index and dynamic target range is adopted. It quantifies the probability of thermal conduction anomaly through exponential mapping and realizes intelligent scaling of thresholds in combination with the historical good product database, so as to achieve extremely high recognition accuracy in thickness deviation detection and greatly reduce the false alarm rate. Furthermore, the compensation correction of fluctuation index and basic index range effectively suppresses the parasitic heat effect caused by complex PCB structures (ceramic substrates, embedded components, high-density BGA arrays), ensuring that the comparison results of the first thermal conduction index and the second thermal conduction index have little deviation from the true value. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly describes the drawings required for the specific embodiments or the description of the prior art. Similar elements or parts are generally identified by similar reference numerals throughout the drawings. Elements or parts in the drawings are not necessarily drawn to scale.

[0015] Figure 1 Schematic diagram of the steps of the method for monitoring PCB solder paste printing results of the present invention; Figure 2 Schematic diagram of a portion of step S3 in the PCB solder paste printing result monitoring method of the present invention; Figure 3 This is a schematic diagram of a portion of step S4 in the method for monitoring PCB solder paste printing results of the present invention; Figure 4 The present invention is a block diagram of an electronic device according to an embodiment of the present invention.

[0016] Reference numerals: 700 - electronic device, 701 - processor, 702 - memory, 703 - multimedia component, 704 - I / O interface, 705 - communication component. DETAILED DESCRIPTION

[0017] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations.

[0018] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are intended to fall within the scope of protection of the present invention.

[0019] It should be noted that similar reference numerals and letters represent similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings. In addition, the terms "first," "second," etc. are used only to distinguish the descriptions and are not to be understood as indicating or implying relative importance.

[0020] like Figure 1 As shown, a method for monitoring PCB solder paste printing results is provided, comprising: S1. Obtain a solder paste printing area and a first detection point and a second detection point located within the solder paste printing area, obtain infrared information of infrared light directed toward the first detection point, obtain a preset time period based on the infrared information, and obtain a first moment and a second moment separated by the preset time period; S2. Obtaining a first infrared temperature at a first detection point at a first moment, and obtaining a second infrared temperature at the first detection point at a second moment, and obtaining a first thermal change index based on the first change model, the first infrared temperature, and the second infrared temperature; obtaining a third infrared temperature at the second detection point at the first moment, and obtaining a fourth infrared temperature at the second detection point at a second moment, and obtaining a second thermal change index based on the second change model, the third infrared temperature, and the fourth infrared temperature; S3, obtaining a fluctuation index according to the first thermal change index and the second thermal change index, obtaining a basic index range, and obtaining a target index range according to the fluctuation index and the basic index range, S4. Obtain a first thermal conductivity index according to the first infrared temperature and the third infrared temperature, obtain a second thermal conductivity index according to the second infrared temperature and the fourth infrared temperature, and obtain a solder paste printing result according to the first thermal conductivity index, the second thermal conductivity index and the target index range.

[0021] In this embodiment, it should be noted that in S1, machine vision is first used to identify the geometric distribution of the pads in the PCB design file. Combined with the motion trajectory of the solder paste printer, the boundary coordinates of the area to be measured are dynamically delineated. Two locations within the solder paste printing area are then selected as the first and second detection points. The first detection point is located directly in the center of the infrared light source to ensure uniform heating, while the second detection point is offset along the substrate's main heat diffusion direction. The distance can be set between 1 / 3 and 1 / 2 of the minimum pad spacing to avoid thermal interference from adjacent components. For example, in a 0.4mm pitch BGA pad array, two diagonally adjacent pads are preferentially selected as detection points to ensure both spatial resolution and the ability to characterize solder paste thickness. The infrared information acquisition module simultaneously acquires the light source's radiant power spectral density curve. By analyzing the attenuation characteristics of specific wavelengths (e.g., the 3-5μm mid-infrared band), the absorption efficiency of infrared energy on the solder paste surface is estimated, and the critical time window for temperature sampling is dynamically set accordingly. For example, for silver-containing solder paste with high absorbance, the preset time period is automatically shortened to milliseconds to capture the fast-responding transient temperature field; while in the lead-free solder paste scenario with low absorbance, the sampling window is extended to seconds to ensure sufficient accumulation of conductive heat energy.

[0022] In S2, the dynamic effect of solder paste thickness on thermal conduction is analyzed through the temperature difference between two time points. At the first detection point, the directional irradiation of the infrared light source causes its temperature change to directly reflect the absorption characteristics of the solder paste surface for radiant energy. The relative rate of change of the two temperature measurements within a preset time period is used to quantify the thermal inertia effect of the heated area and generate a first thermal change index. For the second detection point, its temperature change originates from the heat conduction process at the first point. The model introduces a distance attenuation factor to correct the spatial effect of the heat diffusion path. The second thermal change index is calculated by coupling the time-varying rate of the two temperature differences with the geometric parameters. For example, in a densely arranged micro-pad array, when the distance between the two detection points is large, the weight of the distance factor is automatically increased to compensate for the nonlinear deviation of conduction.

[0023] In S3, a dynamic evaluation mechanism is established to eliminate interference from environmental noise and process fluctuations in thickness assessment by quantifying the synergistic differences in thermal conduction behavior between the two inspection points. Based on the absolute value difference between the first and second thermal variation indicators and mapping it to the interval [0,1), a fluctuation index is generated to characterize the probability of abnormal conduction. This index comprehensively considers the spatiotemporal coupling effects of direct radiative heating and indirect heat conduction. For example, when solder paste thickness is insufficient, the temperature difference rate decreases at the first inspection point due to insufficient heat absorption, while the second inspection point exhibits an abnormal temperature rise due to a shortened heat diffusion path. The asymmetric deviation between the two, when amplified by an exponential function, significantly increases the fluctuation value. Furthermore, based on the baseline indicator range of historical good product data, the upper and lower limits are dynamically narrowed through nonlinear interpolation. When the fluctuation index is high, the target range must be strictly narrowed to ensure sensitivity in detecting minor defects. When the fluctuation value approaches zero, the target range can be moved closer to the baseline threshold to ensure a normal process.

[0024] In S4, based on the temperature gradients and material thermophysical properties at the first and second detection points, the temperature difference signal is converted into a first thermal conductivity indicator and a second thermal conductivity indicator, representing the printed solder paste thickness. This translates the spatiotemporal temperature difference signal into physical indicators representing solder paste thickness, and a dynamic threshold mechanism is used to determine defects. The first thermal conductivity indicator is constructed by the initial temperature difference between the direct and indirect receiving hot spots. Its physical meaning is the transient conduction rate of heat flow within the solder paste layer, integrating the coupled effects of multiple parameters such as material thermal conductivity, specific heat capacity, and geometric spacing. The second thermal conductivity indicator, based on the change in temperature difference over a preset time period, quantifies the cumulative dissipation of heat energy in the substrate-solder paste composite structure. Both indicators are compared against a dynamically generated target range. If both indicators are within the range, it indicates uniform thickness and a complete heat conduction path. If either indicator exceeds the limit, an abnormality is detected, and the direction of the deviation can be used to identify the defect type. For example, a synchronous upward deviation of the indicators indicates enhanced thermal conductivity due to localized thinness, while an anisotropic deviation indicates an abnormal thickness gradient.

[0025] In summary, in the entire PCB solder paste printing result monitoring method, the innovative non-contact infrared thermal conduction dynamic coupling analysis method effectively solves the problems of contamination risk, reflectivity sensitivity, lack of real-time performance, and lack of thickness-heat conduction correlation in traditional solder paste printing monitoring technology. First, based on the synchronous acquisition and dynamic modeling of the spatiotemporal temperature field of dual detection points, a high-precision inversion of the solder paste thickness distribution is achieved: the direct heating characteristics of the first detection point accurately reflect the heat absorption efficiency of the material, and the indirect heating behavior of the second detection point analyzes the spatial attenuation law of the heat diffusion path. The two work together to eliminate the environmental interference error of a single detection point; further, through the adaptive time window adjustment mechanism driven by infrared spectral characteristics, it is compatible with the thermal response characteristics of different solder paste materials (such as high-absorbency silver-containing solder paste and low-absorbency lead-free solder paste), and the thickness-sensitive thermal conduction transient characteristics are captured in a wide time domain range from milliseconds to seconds. The system overcomes the signal distortion problem caused by the traditional fixed sampling frequency. Furthermore, a two-layer evaluation architecture of fluctuation index and dynamic target range is adopted. It quantifies the probability of thermal conduction anomaly through exponential mapping and realizes intelligent scaling of thresholds in combination with the historical good product database, so as to achieve extremely high recognition accuracy in thickness deviation detection and greatly reduce the false alarm rate. Furthermore, the compensation correction of fluctuation index and basic index range effectively suppresses the parasitic heat effect caused by complex PCB structures (ceramic substrates, embedded components, high-density BGA arrays), ensuring that the comparison results of the first thermal conduction index and the second thermal conduction index have little deviation from the true value.

[0026] In one embodiment, the first change model (direct heating, direct infrared light) in obtaining the first thermal change indicator based on the first change model, the first infrared temperature, and the second infrared temperature in S2 is expressed as: ;in, is the first thermal change indicator, is the first infrared temperature, is the second infrared temperature, The preset time period.

[0027] In this embodiment, it should be noted that the temperature change rate term This method quantifies the rate of temperature change, including at the first detection point, and directly reflects the solder paste's ability to absorb infrared energy. After the solder paste layer absorbs infrared energy, its temperature rises linearly over time, with a stable rate of change. Too thin a thickness reduces the material's heat capacity and increases the temperature change rate (faster heating). Too thick a thickness increases the heat capacity and decreases the temperature change rate (slower heating). Traditional methods use only the absolute value of a single temperature point, but this dynamic rate of change directly correlates the effect of thickness on thermal inertia through time, resolving the problem of fixed thresholds being unable to adapt to varying thicknesses.

[0028] Further, Equivalent to the direct heating coefficient of the first detection point, where the numerator Characterizes the radiation intensity of the infrared light source, which is positively correlated with the light source power; the denominator The initial temperature of the second detection point is introduced to suppress the interference of the temperature at the first moment and the ambient thermal background. At the same time, since the first detection point is in contact with the heat source and is directly heated, the heat will not be dissipated and the temperature rises faster. Therefore, the higher the temperature at the first moment, the lower the direct heat coefficient, which is used to suppress the contribution of faster heat changes to the first thermal change index.

[0029] For example, the temperature change of silver solder paste (high heat absorption rate) is detected within a 0.5 second time window. Parameters: =100℃, =30℃, =50℃, =0.5s. The first thermal change index is finally calculated =32.

[0030] In one embodiment, the second change model (indirect heat reception, heat conduction) in obtaining the second thermal change index based on the second change model, the third infrared temperature, and the fourth infrared temperature in S2 is expressed as: ;in, is the second thermal change index, is the third infrared temperature, is the fourth infrared temperature, For the preset time period, is the temperature of infrared light, is the distance between the first detection point and the second detection point.

[0031] In this embodiment, it should be noted that the temperature difference rate term , used to quantify the rate of temperature change per unit time in an indirectly heated area. The temperature rise rate at the second test point is dominated by heat conduction from the first test point, and its rate is negatively correlated with solder paste thickness: thicker solder paste increases thermal resistance, reduces heat conduction to the second test point, and decreases the temperature rise rate.

[0032] Furthermore, the distance increment coefficient , used to compensate for the nonlinear attenuation characteristics of heat conduction with distance. Simulate the natural attenuation of heat flow in the medium; In the equation, when d approaches 0 (two points are adjacent), The closer it is to 1, the less likely it is to be amplified by thermal coupling at close distances. The closer it is to 2, the greater the sensitivity of long-distance conduction is, compensating for the attenuation of temperature changes caused by heat consumption due to heat conduction.

[0033] In summary, traditional optical methods can cause reconstruction errors in micro-pads (such as 0.2mm pitch QFNs) due to light obstruction. However, this model directly relates physical distance to heat diffusion efficiency through the spatial attenuation characteristics of the heat conduction path, and is not affected by surface topography reflections. In a multi-layer PCB, if the second detection point is located in the heat sink area (such as the copper foil layer): the actual heat conduction path is extended due to the embedded structure of the substrate, but the geometric distance (not the actual path length) used by the model simplifies the calculation. The exponential form partially compensates for the heat loss caused by the path bending.

[0034] For example, the conductive characteristics of lead-free solder paste (low thermal conductivity) are tested within a 1-second time window, with the distance between the two test points being d = 0.3 mm. =22℃, =35℃, =0.5s, d=0.3mm. Temperature difference rate term: (35-22) / 0.5=26℃ / s; distance increment coefficient: ≈2-0.7408=1.2592, then the second thermal change index =26*1.2592=32.7392.

[0035] In one embodiment, the fluctuation index obtained according to the first thermal change index and the second thermal change index in S3 is expressed as: ;in, is a volatility indicator, is the first thermal change indicator, is the second thermal change index, is the scaling factor.

[0036] In this embodiment, it should be noted that Used to quantify the difference in the rate of thermal change between two detection points, ignoring directionality; the absolute value eliminates the risk of positive and negative offsets and focuses on the intensity of the difference. , maps the difference of any magnitude to the interval (0, 1], the larger the difference, the smaller the value, solving the problem that the traditional threshold method is insensitive to the magnitude of the difference: when =0, e^{0}=1, D=0 (no fluctuation); when The bigger, tends to 0; at the same time, nonlinear mapping enhances sensitivity to small differences, such as From 5 to 10, D increases significantly. , adjust the difference sensitivity to adapt to different process scenarios, and take it between 0.05 and 0.2. For example: in high-precision scenarios (such as 5G modules), set beta=0.2; in high-noise scenarios (such as workshops with large temperature drift), set =0.05, reducing false alarms; its calibration method can be based on the good and defective samples in historical data Distribution, optimization Maximize the discrimination of D reasonably.

[0037] Furthermore, workshop temperature fluctuations can lead to and Synchronous drift, but the absolute value of the difference Relatively stable; Example: a temperature rise of 10°C causes From 30 to 40, From 25 to 35, the absolute value of the difference is still 5, and D remains unchanged. In micro-pad detection, small thickness differences (such as ±3μm) require high sensitivity. Assume beta = 0.2. =5, D=1-e^{1}≈0.632; in large-area pad inspection, larger process fluctuations are allowed, and beta=0.05 is set, with the same difference =5, D=1-e^{0.25}≈0.221.

[0038] In summary, the expression The fluctuation index is obtained by the first thermal change index and the second thermal change index, and the target index range is obtained according to the fluctuation index and the basic index range. In essence, it is achieved by quantifying the synergistic difference of heat conduction at the two detection points ( ), dynamically adjust the basic indicator range and generate a target indicator range that adapts to real-time process fluctuations. In other words, the design essence of D is to construct a range correction factor to map the intensity of process fluctuations to the tolerance expansion and contraction of the indicator range; if the difference in the synergy of heat conduction between the two detection points is greater, the fluctuation index will be greater, and the target indicator range will be smaller and more stringent.

[0039] For example, based on the above embodiment =32, =32.7392. ,but ≈0.07. This indicates that the difference in the synergy of heat conduction between the two detection points is small, the fluctuation index is also small, and the target index range is closer to the basic index range.

[0040] like Figure 2 As shown, in one embodiment, obtaining the target indicator range according to the fluctuation indicator and the basic indicator range in S3 includes: S31. Obtain the basic minimum index and the basic maximum index according to the basic index range; S32. Obtain a target minimum indicator based on the fluctuation indicator and the basic minimum indicator, and obtain a target maximum indicator based on the fluctuation indicator and the basic maximum indicator; S33. Obtain a target indicator range based on the target minimum indicator and the target maximum indicator.

[0041] In this embodiment, it should be noted that in S31, through the statistics of historical good product data, the system extracts the distribution characteristics of the thermal conductivity index under stable process conditions and determines the basic minimum index and the basic maximum index. These basic values ​​represent the typical fluctuation range of the first and second thermal conductivity indicators when the solder paste thickness is within the qualified range. For example, in a defect-free state, the thermal conductivity index is affected by inherent factors such as material properties and ambient temperature, and its distribution presents normal or skewed characteristics. After eliminating outliers through cluster analysis, the basic range is set to a confidence interval covering 99% of good product data, providing an initial anchor point for subsequent dynamic adjustments. For example, the basic indicator range can be [0.01, 0.02].

[0042] In S32, the boundaries of the basic range are dynamically adjusted using the fluctuation index (D). The target minimum index is generated by adding the basic minimum index to the fluctuation index multiplied by the basic minimum index. The target maximum index is generated by subtracting the fluctuation index from the basic maximum index multiplied by the basic maximum index. As D increases (increasing the probability of abnormality), the lower limit moves up and the upper limit moves down, narrowing the tolerance range to increase sensitivity to insufficient thickness.

[0043] In S33, the corrected boundary values ​​are integrated to generate the final target indicator range. This range serves as the dynamic threshold for defect determination in S4, directly linked to the real-time process status. By adjusting the dynamic range, the system achieves a balance between detection accuracy and interference immunity, significantly reducing the cross-coupling effect between missed detection rate and false alarm rate, and meeting the requirements of various process scenarios.

[0044] In one embodiment, obtaining the first thermal conductivity index according to the first infrared temperature and the third infrared temperature in S4 is expressed as: ;in, is the first heat conduction index, is the thermal conductivity of solder paste, is the first infrared temperature, is the third infrared temperature and, is the solder paste density, is the specific heat capacity of solder paste, is the distance between the first detection point and the second detection point, The preset time period.

[0045] In this embodiment, it should be noted that the temperature difference term It is used to quantify the initial temperature difference between the heat source point and the conduction point, reflecting the driving force of the heat flow. The greater the thickness, the greater the heat flow resistance, and the actual heat conduction under the same temperature difference is reduced. At the same time, it eliminates the influence of the ambient temperature baseline and only focuses on the relative temperature difference between the two points, rather than the absolute temperature value, to avoid interference from temperature drift in the workshop.

[0046] Further, Characterizes the thermal conductivity of solder paste materials and is positively correlated with the metal particle content (such as the Sn / Ag / Cu ratio). Example: Silver-containing solder paste (high thermal conductivity) =50, lead-free solder paste (low thermal conductivity) =30.

[0047] Furthermore, the heat capacity term Represents the ability of solder paste to store heat per unit volume. middle, Simulate the spatial attenuation of three-dimensional heat diffusion (according to Fourier's law, the heat flux density is inversely proportional to the square of the distance); It is a preset time period to eliminate rate deviation caused by different sampling intervals.

[0048] In summary, this method achieves dynamic coupling of thickness and heat conduction. It also resists reflectivity interference. Traditional optical methods suffer from measurement deviations due to the low reflectivity of matte solder paste. However, this model directly correlates the intrinsic material properties through thermophysical parameters and is independent of the surface optical characteristics. It also ensures real-time performance, requiring only two temperature values ​​at a time, with low computational complexity, meeting the millisecond-level response requirements of the production line (traditional 3D imaging requires seconds).

[0049] For example, the scenario is to detect silver solder paste ( =50) thickness on 0.2mm pitch BGA pads.

[0050] parameter: =85℃, =70℃, d=0.2mm, =8400kg / m 3 , =230J / kgK, =0.5s. Substitute into the expression and calculate, we get 0.019. Similarly, use the same expression and substitute and , and obtain the second heat conduction index.

[0051] Result analysis: If the target index range (after S3 adjustment) is [0.011, 0.019], is 0.019, and if It is 0.018, both of which are within the target index range. The printing result is qualified and does not trigger the alarm of too thin or too thick. Real-time feedback is given to the printing machine to adjust the scraper pressure and steel screen position.

[0052] like Figure 3 As shown, in one embodiment, obtaining the solder paste printing result according to the first thermal conductivity index, the second thermal conductivity index and the target thermal conductivity threshold in S4 includes: S41, determining whether the first heat conduction index and the second heat conduction index are both within the target index range; S42: If yes, it is determined that the solder paste printing has no thickness defects; S43. If not, it is determined that there is a thickness defect in the solder paste printing.

[0053] In this embodiment, it should be noted that in S41, the first thermal conductivity indicator (which tends to represent transient heat transfer rate) and the second thermal conductivity indicator (which tends to reflect steady-state heat accumulation effects) are simultaneously compared against a dynamically generated target indicator range. This step, through a logical "AND" relationship, requires that both indicators must be within the target range simultaneously, thus avoiding misjudgment of a single indicator due to environmental noise or local interference. For example, in a multilayer ceramic substrate scenario, the first thermal conductivity indicator may remain within the normal range due to thermal hysteresis, while the second thermal conductivity indicator may be low due to rapid heat dissipation from the substrate. The combined determination of these two indicators can effectively distinguish between true thickness defects and interference from the substrate material.

[0054] In S42, when thickness is uniform and the heat conduction path is intact, transient and steady-state thermal behavior must meet a synergistic balance between material properties and geometric constraints. For example, in lead-free solder paste printing, even with minor process fluctuations (such as squeegee pressure ±5%), dual indicators remain stable within the elastic target range. The system only records process parameter adjustments rather than triggering defect alarms, thus reducing unnecessary downtime caused by equipment vibration or material batch differences.

[0055] In S43, defect detection is triggered when any indicator exceeds a limit, and the defect type is determined by deviation direction. A simultaneous upward deviation of both indicators indicates localized thinness (abnormally increased thermal conductivity) or metal filler accumulation (a surge in thermal conductivity); a simultaneous downward deviation of both indicators indicates overall thickness (increased thermal resistance) or void defects (impeded thermal diffusion). Linked to the process database, defect types are mapped to specific parameter adjustment recommendations (such as blade pressure compensation and stencil cleaning cycle), achieving closed-loop control from detection to process optimization, preventing defects from flowing into subsequent steps.

[0056] A PCB solder paste printing result monitoring system is also provided, the system comprising: an acquisition module, configured to acquire a solder paste printing area and a first detection point and a second detection point located within the solder paste printing area, and to acquire infrared information of infrared light directed toward the first detection point, and to acquire a preset time period based on the infrared information, and to acquire a first moment and a second moment separated by the preset time period; a first data processing module, configured to obtain a first infrared temperature at a first detection point at a first moment, obtain a second infrared temperature at the first detection point at a second moment, obtain a first thermal change index based on the first change model, the first infrared temperature, and the second infrared temperature, obtain a third infrared temperature at the second detection point at the first moment, obtain a fourth infrared temperature at the second detection point at a second moment, and obtain a second thermal change index based on the second change model, the third infrared temperature, and the fourth infrared temperature; a second data processing module, configured to obtain a fluctuation index based on the first thermal change index and the second thermal change index, and obtain a basic index range, and obtain a target index range based on the fluctuation index and the basic index range; The monitoring module is used to obtain a first thermal conductivity index according to the first infrared temperature and the third infrared temperature, and to obtain a second thermal conductivity index according to the second infrared temperature and the fourth infrared temperature, and to obtain a solder paste printing result according to the first thermal conductivity index, the second thermal conductivity index and the target index range.

[0057] In this embodiment, it should be noted that, regarding the above-mentioned PCB solder paste printing result monitoring system, the specific manner of performing the operation has been described in detail in the embodiment of the PCB solder paste printing result monitoring method, and will not be elaborated here.

[0058] Figure 4 FIG. 1 is a block diagram of an electronic device for monitoring a PCB solder paste printing result according to an exemplary embodiment. Figure 4 As shown, the electronic device 700 may include: a processor 701 , a memory 702 , and may further include one or more of a multimedia component 703 , an I / O interface 704 (input / output interface), and a communication component 705 .

[0059] The processor 701 is used to control the overall operation of the electronic device 700 to complete all or part of the steps in the above-mentioned PCB solder paste printing result monitoring method. The memory 702 is used to store various types of data to support the operation of the electronic device 700. This data may include, for example, instructions for any application or method operating on the electronic device 700, as well as application-related data such as contact information, sent and received messages, images, audio, video, etc. The memory 702 can be implemented by any type of volatile or non-volatile storage device, or a combination thereof, such as static random access memory (SRAM), electrically erasable programmable read-only memory (EEPROM), erasable programmable read-only memory (EPROM), programmable read-only memory (PROM), read-only memory (ROM), magnetic storage, flash memory, magnetic disk, or optical disk. The multimedia component 703 may include a screen and an audio component. The screen may be, for example, a touch screen, and the audio component is used to output and / or input audio signals. For example, the audio component may include a microphone for receiving external audio signals. The received audio signals may be further stored in the memory 702 or transmitted via the communication component 705. The audio component also includes at least one speaker for outputting audio signals. The I / O interface 704 provides an interface between the processor 701 and other interface modules, which may be a keyboard, a mouse, buttons, etc. These buttons may be virtual buttons or physical buttons. The communication component 705 is used for wired or wireless communication between the electronic device 700 and other devices. Wireless communication, such as Wi-Fi, Bluetooth, Near Field Communication (NFC), 2G, 3G, 4G, NB-IOT, eMTC or other 5G, etc., or a combination of one or more thereof, is not limited here. Therefore, the corresponding communication component 705 may include: a Wi-Fi module, a Bluetooth module, an NFC module, etc.

[0060] In an exemplary embodiment, the electronic device 700 can be implemented by one or more application-specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field programmable gate arrays (FPGAs), controllers, microcontrollers, microprocessors, or other electronic components to execute the above-mentioned PCB solder paste printing result monitoring method.

[0061] In another exemplary embodiment, a computer-readable storage medium including program instructions is also provided. When executed by a processor, the program instructions implement the steps of the aforementioned method for monitoring PCB solder paste printing results. For example, the computer-readable storage medium may be the aforementioned memory 702 including the program instructions. The program instructions may be executed by the processor 701 of the electronic device 700 to implement the aforementioned method for monitoring PCB solder paste printing results.

[0062] In another exemplary embodiment, a computer program product is also provided, which includes a computer program that can be executed by a programmable device, and the computer program has a code portion for executing the above-mentioned PCB solder paste printing result monitoring method when executed by the programmable device.

[0063] The preferred embodiments of the present disclosure are described in detail above in conjunction with the accompanying drawings. However, the present disclosure is not limited to the specific details of the above embodiments. Within the technical concept of the present disclosure, various simple modifications can be made to the technical solutions of the present disclosure, and these simple modifications all fall within the scope of protection of the present disclosure.

[0064] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present disclosure will not further describe various possible combinations.

[0065] In addition, the various embodiments of the present disclosure may be arbitrarily combined, and as long as they do not violate the concept of the present disclosure, they should also be regarded as the contents disclosed by the present disclosure.

[0066] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention, and they should all be included in the scope of the claims and description of the present invention.

Claims

1. A method for monitoring PCB solder paste printing results, characterized in that: include: Obtaining a solder paste printing area and a first detection point and a second detection point located within the solder paste printing area, and obtaining infrared information of infrared light directed toward the first detection point, obtaining a preset time period based on the infrared information, and obtaining a first moment and a second moment separated by the preset time period; Acquire a first infrared temperature at a first detection point at a first moment, acquire a second infrared temperature at the first detection point at a second moment, and acquire a first thermal change index based on the first change model, the first infrared temperature, and the second infrared temperature; acquire a third infrared temperature at the second detection point at the first moment, and acquire a fourth infrared temperature at the second detection point at the second moment, and acquire a second thermal change index based on the second change model, the third infrared temperature, and the fourth infrared temperature; Obtaining a fluctuation index according to the first thermal change index and the second thermal change index, obtaining a basic index range, and obtaining a target index range according to the fluctuation index and the basic index range; A first thermal conductivity index is obtained according to the first infrared temperature and the third infrared temperature, a second thermal conductivity index is obtained according to the second infrared temperature and the fourth infrared temperature, and a solder paste printing result is obtained according to the first thermal conductivity index, the second thermal conductivity index and the target index range.

2. The PCB solder paste printing result monitoring method according to claim 1, characterized in that: The first change model (direct heating, direct infrared light) in obtaining the first thermal change index based on the first change model, the first infrared temperature, and the second infrared temperature is expressed as: ;in, is the first thermal change indicator, is the first infrared temperature, is the second infrared temperature, The preset time period.

3. The PCB solder paste printing result monitoring method according to claim 1, wherein: The second change model (indirect heat reception, heat conduction) in obtaining the second thermal change index based on the second change model, the third infrared temperature, and the fourth infrared temperature is expressed as: ;in, is the second thermal change index, is the third infrared temperature, is the fourth infrared temperature, For the preset time period, is the temperature of infrared light, is the distance between the first detection point and the second detection point.

4. The PCB solder paste printing result monitoring method according to claim 1, wherein: The fluctuation index obtained according to the first thermal change index and the second thermal change index is expressed as: ;in, is a volatility indicator, is the first thermal change indicator, is the second thermal change index, is the scaling factor.

5. The PCB solder paste printing result monitoring method according to claim 1, wherein: The acquisition of the target indicator range based on the fluctuation indicator and the basic indicator range includes: Obtain the basic minimum index and basic maximum index according to the basic index range; The target minimum index is obtained based on the volatility index and the basic minimum index, and the target maximum index is obtained based on the volatility index and the basic maximum index; Get the target indicator range based on the target minimum indicator and the target maximum indicator.

6. The PCB solder paste printing result monitoring method according to claim 1, characterized in that: The first thermal conductivity index obtained according to the first infrared temperature and the third infrared temperature is expressed as: ;in, is the first heat conduction index, is the thermal conductivity of solder paste, is the first infrared temperature, is the third infrared temperature and, is the solder paste density, is the specific heat capacity of solder paste, is the distance between the first detection point and the second detection point, The preset time period.

7. The PCB solder paste printing result monitoring method according to claim 1, characterized in that: Obtaining the solder paste printing result according to the first thermal conductivity index, the second thermal conductivity index and the target thermal conductivity threshold comprises: determining whether the first heat conduction index and the second heat conduction index are both within a target index range; If so, it is determined that the solder paste printing has no thickness defects; If not, it is determined that there is a thickness defect in the solder paste printing.

8. A PCB solder paste printing result monitoring system, characterized in that: The system comprises: an acquisition module, configured to acquire a solder paste printing area and a first detection point and a second detection point located within the solder paste printing area, and to acquire infrared information of infrared light directed toward the first detection point, and to acquire a preset time period based on the infrared information, and to acquire a first moment and a second moment separated by the preset time period; a first data processing module, configured to obtain a first infrared temperature at a first detection point at a first moment, obtain a second infrared temperature at the first detection point at a second moment, obtain a first thermal change index based on the first change model, the first infrared temperature, and the second infrared temperature, obtain a third infrared temperature at the second detection point at the first moment, obtain a fourth infrared temperature at the second detection point at a second moment, and obtain a second thermal change index based on the second change model, the third infrared temperature, and the fourth infrared temperature; a second data processing module, configured to obtain a fluctuation index based on the first thermal change index and the second thermal change index, and obtain a basic index range, and obtain a target index range based on the fluctuation index and the basic index range; The monitoring module is used to obtain a first thermal conductivity index according to the first infrared temperature and the third infrared temperature, and to obtain a second thermal conductivity index according to the second infrared temperature and the fourth infrared temperature, and to obtain a solder paste printing result according to the first thermal conductivity index, the second thermal conductivity index and the target index range.

9. An electronic device, characterized in that: include: a memory having a computer program stored thereon; A processor, configured to execute the computer program in the memory to implement the PCB solder paste printing result monitoring method according to any one of claims 1 to 7.

10. A non-transitory computer-readable storage medium having a computer program stored thereon, characterized in that: When the program is executed by a processor, the PCB solder paste printing result monitoring method described in any one of claims 1 to 7 is implemented.

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