A PCB solder paste printing result monitoring method, system, device and medium

Abstract

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

Description

Technical Field

[0001] This invention relates to the field of data processing technology, specifically to a method, system, device, and medium for monitoring PCB solder paste printing results. Background Technology

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

[0003] Traditional solder paste printing result monitoring mainly relies 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 are prone to causing solder paste deformation or contamination in high-speed production lines, damaging the precision pad structure; optical inspection is sensitive to the reflectivity differences of transparent / matte solder paste materials, especially in miniaturized BGA (Ball Grid Array) or QFN (Quad Flat No-Leader) package areas, where light diffraction and shadow effects lead to high errors in three-dimensional contour reconstruction, affecting monitoring results; more importantly, existing technologies cannot achieve real-time closed-loop monitoring of the printing process, and can only perform sampling inspections after printing. This allows defective products to flow into the reflow soldering stage, resulting in hidden defects such as bridging and cold solder joints, leading to high rework rates and material waste; finally, although infrared thermal imaging technology developed in recent years can obtain temperature field distribution non-contactly, current methods only rely on the absolute value of temperature at a single point or a fixed threshold for judgment, without considering the dynamic coupling relationship between solder paste thickness and heat conduction. All these shortcomings combined make it difficult for existing technologies to meet the process requirements of solder paste printing thickness for high-end PCBs such as 5G communication modules and automotive electronics. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a method, system, device, and medium for monitoring PCB solder paste printing results.

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

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

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

[0008] Optionally, the fluctuation index can be obtained based on the first and second thermal change indices, and expressed as follows: ;in, As a volatility indicator, As the primary indicator of thermal change, As the second thermal change index, This is the scaling factor.

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

[0010] Optionally, the first thermal conductivity index, obtained from the first infrared temperature and the third infrared temperature, is expressed as follows: ;in, As the primary indicator of thermal conductivity, For the thermal conductivity of solder paste, The first infrared temperature, For the third infrared temperature and, The density of the solder paste, The specific heat capacity of solder paste, The distance between the first and second detection points. This is a 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 both the first thermal conductivity index and the second thermal conductivity index are within the target index range; if so, it is determined that the solder paste printing has no thickness defects; if not, it is determined that the solder paste printing has thickness defects.

[0012] A PCB solder paste printing result monitoring system is also provided. The system includes: an acquisition module, used to acquire the 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 incident on 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 at intervals of the preset time period; a first data processing module, used to acquire a first infrared temperature at the first detection point at the first moment, and a second infrared temperature at the first detection point at the second moment, to acquire a first thermal change index based on a first change model, the first infrared temperature, and the second infrared temperature, and to acquire a first thermal change index at the second detection point at the first moment. A third infrared temperature is obtained, and a fourth infrared temperature is obtained at a second detection point at a second time. A second thermal change index is obtained based on a second change model, the third infrared temperature, and the fourth infrared temperature. A second data processing module is used to obtain a fluctuation index based on the first and second thermal change indices, obtain a basic index range, and obtain a target index range based on the fluctuation index and the basic index range. A monitoring module is used to obtain a first thermal conduction index based on the first and third infrared temperatures, obtain a second thermal conduction index based on the second and fourth infrared temperatures, and obtain solder paste printing results based on the first thermal conduction index, the second thermal conduction index, and the target index range.

[0013] The beneficial effects of this invention are reflected in:

[0014] In the entire PCB solder paste printing result monitoring method, an innovative non-contact infrared thermal conduction dynamic coupling analysis method effectively solves the problems of contamination risk, reflectivity sensitivity, insufficient real-time performance, and lack of thickness-thermal conduction correlation in traditional solder paste printing monitoring technologies. Firstly, based on the synchronous acquisition and dynamic modeling of the spatiotemporal temperature field at dual detection points, high-precision inversion of solder paste thickness distribution is achieved: the direct heating characteristics of the first detection point accurately reflect the material's heat absorption efficiency, while 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 environmental interference errors from a single detection point. Furthermore, through an 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), capturing thickness-sensitive transient thermal conduction characteristics within a wide time domain range from milliseconds to seconds. This approach overcomes the signal distortion problem caused by traditional fixed sampling frequencies. Furthermore, it adopts a two-layer evaluation architecture of fluctuation index and dynamic target range. It quantifies the probability of thermal conduction anomalies through exponential mapping and achieves intelligent threshold scaling by combining a historical good product database, resulting in extremely high recognition accuracy and a significantly reduced false alarm rate in thickness deviation detection. In addition, the compensation and correction of the fluctuation index and basic index range effectively suppresses the parasitic thermal effects caused by complex PCB structures (ceramic substrates, embedded components, high-density BGA arrays), ensuring that the comparison results of the first and second thermal conduction indices have small deviations from the true values. Attached Figure Description

[0015] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn to scale.

[0016] Figure 1 This is a schematic diagram of the steps in the PCB solder paste printing result monitoring method of the present invention;

[0017] Figure 2 This is a schematic diagram of a portion of step S3 in the PCB solder paste printing result monitoring method of the present invention;

[0018] Figure 3 This is a schematic diagram of a portion of step S4 in the PCB solder paste printing result monitoring method of the present invention;

[0019] Figure 4 This is a block diagram illustrating an electronic device according to an embodiment of the present invention.

[0020] Figure label:

[0021] 700 - Electronic device; 701 - Processor; 702 - Memory; 703 - Multimedia component; 704 - I / O interface; 705 - Communication component. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0023] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0024] It should be noted that similar reference numerals and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Furthermore, the terms "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0025] like Figure 1 As shown, a method for monitoring PCB solder paste printing results is provided, including:

[0026] S1. Obtain the solder paste printing area and the first and second detection points located within the solder paste printing area, and obtain the infrared information of the infrared light directed towards the first detection point, and obtain a preset time period based on the infrared information, and obtain the first and second moments at a preset time interval.

[0027] S2. At the first moment, obtain the first infrared temperature at the first detection point, and at the second moment, obtain the second infrared temperature at the first detection point. Based on the first change model, the first infrared temperature and the second infrared temperature, obtain the first thermal change index. At the first moment, obtain the third infrared temperature at the second detection point, and at the second moment, obtain the fourth infrared temperature at the second detection point. Based on the second change model, the third infrared temperature and the fourth infrared temperature, obtain the second thermal change index.

[0028] S3. Obtain the fluctuation index based on the first and second thermal change indices, and obtain the basic index range. Then, obtain the target index range based on the fluctuation index and the basic index range.

[0029] S4. Obtain the first thermal conductivity index based on the first infrared temperature and the third infrared temperature, obtain the second thermal conductivity index based on the second infrared temperature and the fourth infrared temperature, and obtain the solder paste printing result based on the first thermal conductivity index, the second thermal conductivity index and the target index range.

[0030] In this embodiment, it should be noted that in S1, the geometric distribution of pads in the PCB design file is first identified by machine vision, and the boundary coordinates of the area to be tested are dynamically defined in conjunction with the movement trajectory of the solder paste printer. Then, two positions are selected within the solder paste printing area as the first detection point and the second detection point. The first detection point is located at the center of the infrared light source to ensure heating and uniformity, while the second detection point is offset along the main direction of heat diffusion on the substrate. The distance can be set according to 1 / 3 to 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 adjacent pads in the diagonal direction are preferentially selected as detection points to ensure both spatial resolution and reflect the solder paste thickness characteristics. The infrared information acquisition module simultaneously acquires the radiation power spectral density curve of the light source. By analyzing the attenuation characteristics of a specific wavelength (such as the 3-5μm mid-infrared band), the absorption efficiency of the solder paste surface for infrared energy is calculated, and the key 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 the millisecond level to capture the transient temperature field with a fast response; while in the case of lead-free solder paste with low absorbance, the sampling window is extended to the second level to ensure sufficient accumulation of conductive heat energy.

[0031] In S2, the dynamic impact of solder paste thickness on heat conduction is analyzed through temperature differences at 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 to radiant energy. The thermal inertia effect of the heated area is quantified by the relative change rate of two temperature measurements within a preset time period, and a first thermal change index is generated. 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, and a second thermal change index is calculated by coupling the time-varying rate of the two temperature differences with 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.

[0032] In S3, a dynamic evaluation mechanism is established to eliminate the interference of environmental noise and process fluctuations on thickness judgment by quantifying the synergistic differences in the thermal conduction behavior of the two detection points. Based on the absolute value of the difference between the first and second thermal change indices, and mapping them to the [0,1) interval, a fluctuation index characterizing the probability of abnormal conduction is generated. This index comprehensively considers the spatiotemporal coupling effect of direct radiation heating and indirect thermal conduction. For example, when the solder paste thickness is insufficient, the temperature difference change rate of the first detection point decreases due to insufficient heat absorption, while the second detection point exhibits an abnormal temperature rise due to the shortened thermal diffusion path. The asymmetric deviation between the two is amplified by an exponential function, significantly increasing the fluctuation value. Furthermore, based on the basic index range of historical good product data statistics, 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 the sensitivity of capturing small defects; when the fluctuation value approaches zero, the target range can approach the basic threshold to ensure normal process.

[0033] In S4, based on the temperature gradient and material thermal properties at the first and second detection points, the temperature difference signal is converted into a first thermal conductivity index and a second thermal conductivity index to represent the solder paste printing thickness. This means the spatiotemporal temperature difference signal is transformed into a physical index characterizing the solder paste thickness, and defect determination is achieved through a dynamic threshold mechanism. The first thermal conductivity index is constructed using the initial temperature difference between directly and indirectly affected hot spots. Its physical meaning is the transient heat transfer rate within the solder paste layer, integrating the coupling effects of multiple parameters such as material thermal conductivity, specific heat capacity, and geometric spacing. The second thermal conductivity index quantifies the cumulative dissipation characteristics of heat energy in the substrate-solder paste composite structure based on the temperature difference change after a preset time period. The two indices are compared with dynamically generated target ranges: if both indices are within the range, it indicates uniform thickness and a complete heat transfer path; if either index exceeds the limit, an anomaly determination is triggered, and the direction of deviation can pinpoint the defect type. For example, a simultaneous upward deviation of the indices suggests enhanced thermal conductivity due to localized thinning, while an outward deviation reflects an abnormal thickness gradient.

[0034] In summary, the innovative non-contact infrared thermal conduction dynamic coupling analysis method effectively solves the problems of contamination risk, reflectivity sensitivity, insufficient real-time performance, and lack of thickness-thermal conduction correlation in traditional solder paste printing monitoring technologies. Firstly, based on the synchronous acquisition and dynamic modeling of the spatiotemporal temperature field at dual detection points, high-precision inversion of solder paste thickness distribution is achieved: the direct heating characteristics of the first detection point accurately reflect the material's heat absorption efficiency, while the indirect heating behavior of the second detection point analyzes the spatial attenuation law of the heat diffusion path. The two methods work together to eliminate environmental interference errors from a single detection point. Furthermore, through an adaptive time window adjustment mechanism driven by infrared spectral characteristics, the method 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), capturing thickness-sensitive transient thermal conduction characteristics within a wide time domain ranging from milliseconds to seconds. This approach overcomes the signal distortion problem caused by traditional fixed sampling frequencies. Furthermore, it adopts a two-layer evaluation architecture of fluctuation index and dynamic target range. It quantifies the probability of thermal conduction anomalies through exponential mapping and achieves intelligent threshold scaling by combining a historical good product database, resulting in extremely high recognition accuracy and a significantly reduced false alarm rate in thickness deviation detection. In addition, the compensation and correction of the fluctuation index and basic index range effectively suppresses the parasitic thermal effects caused by complex PCB structures (ceramic substrates, embedded components, high-density BGA arrays), ensuring that the comparison results of the first and second thermal conduction indices have small deviations from the true values.

[0035] In one implementation, the first change model (direct heating, direct infrared light exposure) in S2, which is based on the first change model, the first infrared temperature, and the second infrared temperature to obtain the first thermal change index, is expressed as follows:

[0036] ;in,

[0037] As the primary indicator of thermal change, The first infrared temperature, The second infrared temperature, This is a preset time period.

[0038] In this embodiment, it should be noted that the temperature change rate term This dynamic rate of change is used to quantify the temperature change rate, including at the first detection point, directly reflecting the solder paste's ability to absorb infrared energy. After absorbing infrared energy, the temperature of the solder paste layer increases linearly over time, and the rate of change remains stable. Too thin a layer leads to a decrease in the material's heat capacity, resulting in a higher rate of temperature change (faster heating); too thick a layer leads to an increase in heat capacity, resulting in a lower rate of temperature change (slower heating). Traditional methods only use the absolute value of temperature at a single point, while this dynamic rate of change, through differences in the time dimension, directly relates to the influence of thickness on thermal inertia, solving the problem that a fixed threshold cannot adapt to different thicknesses.

[0039] Furthermore, Equivalent to the direct heating coefficient of the first detection point, where the molecules The radiant intensity of an infrared light source is positively correlated with its power; the denominator... The initial temperature of the second detection point is introduced to suppress the interference of temperature and ambient thermal background at the first moment. 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 lost and the temperature rises faster. Therefore, the higher the temperature at the first moment, the lower the direct heating coefficient, which is used to suppress the contribution of rapid heat change to the first thermal change index.

[0040] For example, the temperature change of silver-containing solder paste (high heat absorption rate) is measured within a 0.5-second time window. Parameters: =100℃, =30℃, =50℃, =0.5s. The final calculation yielded the first thermal change index. =32.

[0041] In one implementation, the second change model (indirect heating, heat conduction) in S2, which is based on the second change model, the third infrared temperature, and the fourth infrared temperature to obtain the second thermal change index, is represented as follows:

[0042] ;in,

[0043] As the second thermal change index, The third infrared temperature, The fourth infrared temperature, For a preset time period, The temperature of infrared light, This is the distance between the first and second detection points.

[0044] In this embodiment, it should be noted that the temperature difference rate term... This is used to quantify the rate of temperature change in the indirectly heated area per unit time. The temperature rise rate at the second detection point is dominated by the heat conduction at the first detection point, and its rate is negatively correlated with the solder paste thickness: the greater the thickness, the higher the thermal resistance, the less heat is conducted to the second point, and the lower the temperature rise rate.

[0045] Furthermore, the distance increment coefficient This is used to compensate for the nonlinear attenuation of heat conduction with distance. Among them, Simulates the natural decay of heat flux in a medium; In the case of d approaching 0 (two points are adjacent), The closer d is to 1, the less abnormal amplification caused by close-range thermal coupling should be avoided. The larger d is (for long distances), the better. The closer it is to 2, the more sensitive it is to long-distance conduction, compensating for the temperature drop caused by heat loss during heat conduction.

[0046] In summary, traditional optical methods suffer from reconstruction errors in micro-pads (such as 0.2mm pitch QFNs) due to light occlusion. This model, however, directly correlates physical distance with heat diffusion efficiency by utilizing the spatial attenuation characteristics of the heat conduction path, and is unaffected by surface topography reflections. In multilayer PCBs, if the second detection point is located in a heat sink area (such as a copper foil layer): the actual heat conduction path is extended due to the substrate's embedded structure, but the geometric distance traversed by the model (not the actual path length) simplifies the calculation. (Coefficient) The exponential form partially compensates for heat loss caused by path bending.

[0047] For example, the conductivity characteristics of lead-free solder paste (low thermal conductivity) are tested within a 1-second time window, with a distance of d = 0.3 mm between two test points. =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, therefore the second thermal change index =26*1.2592=32.7392.

[0048] In one implementation, the fluctuation index obtained in S3 based on the first thermal change index and the second thermal change index is expressed as follows:

[0049] ;in,

[0050] As a volatility indicator, As the primary indicator of thermal change, As the second thermal change index, This is the scaling factor.

[0051] In this embodiment, it should be noted that, Used to quantify the difference in thermal change rates between two detection points, ignoring directionality; absolute value eliminates the risk of positive and negative cancellation, focusing on the intensity of the difference. Exponential decay term. This method maps differences of any magnitude to the interval (0, 1], where the larger the difference, the smaller the value, thus addressing the problem of traditional thresholding methods being insensitive to the magnitude of the difference: when When =0, e^{0}=1, D=0 (no fluctuation); when The larger, It tends towards 0; at the same time, the nonlinear mapping enhances the sensitivity to small differences, such as The increase in D is significant when it increases from 5 to 10. (Scaling factor) Adjust the difference sensitivity to adapt to different process scenarios, taking a value 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 large temperature drift in workshops), set... =0.05, reducing false alarms; its calibration method can be based on historical data of good and defective samples. Distribution, optimization To maximize the discriminative power of D.

[0052] Furthermore, fluctuations in workshop temperature can lead to and Synchronous drift, but absolute difference Relatively stable; Example: A temperature rise of 10℃ makes... From 30 to 40, From 25 to 35, the absolute value of the difference remains 5, and D remains unchanged. In micro pad inspection, small thickness differences (e.g., ±3μm) require high sensitivity. Let beta = 0.2, when... When β = 5, D = 1 - e^{1} ≈ 0.632; in large-area pad inspection, larger process fluctuations are permissible. Let beta = 0.05, for the same difference... =5, D=1-e^{0.25}≈0.221.

[0053] In summary, the expression The fluctuation index is obtained through the first and second thermal change indices, and the target index range is obtained based on the fluctuation index and the range of the basic index. In essence, this is achieved by quantifying the synergistic difference in heat conduction between the two detection points. The design of D is essentially to construct a range correction factor that maps the intensity of process fluctuations to the tolerance range of the index range. If the difference in the synergy of heat conduction between two detection points is greater, the fluctuation index will be larger and the target index range will be smaller and more stringent.

[0054] For example, based on the above embodiments... =32, =32.7392. Let... ,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.

[0055] like Figure 2 As shown, in one implementation, obtaining the target indicator range based on the volatility indicator and the basic indicator range in step S3 includes:

[0056] S31. Obtain the minimum and maximum basic indicators based on the range of basic indicators;

[0057] S32. Obtain the target minimum indicator based on the volatility indicator and the basic minimum indicator, and obtain the target maximum indicator based on the volatility indicator and the basic maximum indicator.

[0058] S33. Obtain the target indicator range based on the minimum and maximum target indicators.

[0059] In this embodiment, it should be noted that in S31, by statistically analyzing historical good product data, the system extracts the distribution characteristics of thermal conductivity indicators under stable process conditions to determine the basic minimum and basic maximum indicators. These basic values ​​represent the typical fluctuation range of the first and second thermal conductivity indicators when the solder paste thickness is within the acceptable range. For example, under defect-free conditions, the thermal conductivity indicators are affected by inherent factors such as material properties and ambient temperature, and their distribution exhibits normal or skewed characteristics. After removing outliers through cluster analysis, the basic range is set as a confidence interval covering 99% of the good product data, providing an initial anchor point for subsequent dynamic adjustments. For example, the basic indicator range can be [0.01, 0.02].

[0060] In S32, the boundary of the base range is dynamically adjusted through the volatility index (D). The target minimum index is generated by adding the volatility index multiplied by the base minimum index to the base minimum index, and the target maximum index is generated by subtracting the volatility index multiplied by the base maximum index from the base maximum index. When D increases (the probability of anomalies increases), the lower limit moves up and the upper limit moves down, narrowing the tolerance range to improve sensitivity to insufficient thickness.

[0061] In S33, the corrected boundary values ​​are integrated to generate the final target index range. This range serves as the dynamic threshold for defect determination in S4, directly correlated with the real-time process status. Through dynamic range adjustment, the system achieves a balance between detection accuracy and anti-interference capability, significantly reducing the cross-coupling effect of false negatives and false alarms, and meeting the process requirements of multiple scenarios.

[0062] In one embodiment, the first thermal conductivity index obtained in S4 based on the first infrared temperature and the third infrared temperature is expressed as follows:

[0063] ;in,

[0064] As the primary indicator of thermal conductivity, For the thermal conductivity of solder paste, The first infrared temperature, For the third infrared temperature and, The density of the solder paste, The specific heat capacity of solder paste, The distance between the first and second detection points. This is a preset time period.

[0065] In this embodiment, it should be noted that the temperature difference term... In this process, the initial temperature difference between the heat source and the conduction point is quantified, reflecting the driving force of heat flow. The greater the thickness, the stronger the heat flow resistance, and the less actual heat is conducted under the same temperature difference. At the same time, the influence of the ambient temperature baseline is eliminated, focusing only on the relative temperature difference between the two points, rather than the absolute temperature value, to avoid temperature drift interference in the workshop.

[0066] Furthermore, The thermal conductivity of solder paste materials is positively correlated with the content of metal particles (e.g., the Sn / Ag / Cu ratio). Example: Silver-containing solder paste (high thermal conductivity). =50, lead-free solder paste (low thermal conductivity) =30.

[0067] Furthermore, heat capacity item This represents the ability of a unit volume of solder paste to store heat. middle, Simulate the spatial decay of three-dimensional heat diffusion (in Fourier's law, heat flux density is inversely proportional to the square of the distance). The preset time period is used to eliminate rate deviations caused by different sampling intervals.

[0068] In summary, this model achieves dynamic coupling between thickness and thermal conduction; it is also resistant to reflectivity interference. Traditional optical methods suffer from measurement errors due to the low reflectivity of matte solder paste, while this model directly correlates the essential properties of the material through thermal property parameters, independent of surface optical characteristics; it also ensures real-time performance, requiring only temperature values ​​at two time points, with low computational complexity, meeting the millisecond-level response requirements of production lines (traditional 3D imaging requires second-level processing).

[0069] For example, in the scenario of detecting silver-containing solder paste ( =50) Thickness on 0.2mm pitch BGA pads.

[0070] parameter: =85℃, =70℃, d=0.2mm, =8400kg / m 3 , =230J / kgK, =0.5s. Substituting into the expression, we get... 0.019. Similarly, using the same expression, substitute... and Thus, the second thermal conductivity index was obtained.

[0071] Result Analysis: If the target index range (after adjustment by S3) is [0.011, 0.019], It is 0.019, and if The value is 0.018, both of which are within the target range. The printing result is qualified and does not trigger the alarm for being too thin or too thick. The feedback is sent to the printing press in real time to adjust the squeegee pressure and the position of the stencil.

[0072] like Figure 3 As shown, in one embodiment, obtaining the solder paste printing result in S4 based on the first thermal conductivity index, the second thermal conductivity index, and the target thermal conductivity threshold includes:

[0073] S41. Determine whether both the first and second thermal conductivity indicators are within the target range.

[0074] S42. If so, then the solder paste printing is determined to have no thickness defects;

[0075] S43. If not, then the solder paste printing is determined to have a thickness defect.

[0076] In this embodiment, it should be noted that in S41, the first thermal conductivity index (which tends to characterize transient thermal conduction rate) and the second thermal conductivity index (which tends to reflect steady-state thermal accumulation effect) are simultaneously compared with the dynamically generated target index range. This step requires that both indices be within the target range simultaneously through a logical "AND" relationship, avoiding misjudgment caused by environmental noise or local interference from a single index. For example, in the case of a multilayer ceramic substrate, the first thermal conductivity index may still be within the normal range due to thermal hysteresis, but the second thermal conductivity index may be lower due to rapid heat dissipation of the substrate. The joint judgment of the two indices can effectively distinguish between true thickness defects and substrate material interference.

[0077] In S42, when the thickness is uniform and the heat conduction path is complete, transient and steady-state thermal behavior must satisfy 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%), both indicators can remain stable within the elastic target range. The system only records minor adjustments to process parameters rather than triggering defect alarms, thereby reducing unnecessary downtime caused by equipment vibration or material batch differences.

[0078] In S43, a defect determination is triggered when any indicator exceeds the limit, and the defect type is located by the deviation direction: simultaneous upward deviation of both indicators indicates local overthrow (abnormally increased thermal conductivity) or metal filler accumulation (surge in thermal conductivity); simultaneous downward deviation of both indicators indicates overall overthrow (increased thermal resistance) or void defects (impeded thermal diffusion). Linking with the process database, the defect type is mapped to specific parameter adjustment suggestions (such as scraper pressure compensation value, stencil cleaning cycle), achieving closed-loop control from detection to process optimization, preventing defects from flowing into subsequent processes.

[0079] A PCB solder paste printing result monitoring system is also provided, the system including:

[0080] The acquisition module is used to acquire the solder paste printing area and the first detection point and the second detection point located in the solder paste printing area, acquire the infrared information of the infrared light directed toward the first detection point, acquire a preset time period based on the infrared information, and acquire the first moment and the second moment at a preset time interval.

[0081] The first data processing module is used to acquire a first infrared temperature at a first detection point at a first moment, and acquire a second infrared temperature at a second detection point at a second moment, acquire a first thermal change index based on a first change model, the first infrared temperature and the second infrared temperature, acquire a third infrared temperature at a second detection point at a first moment, acquire a fourth infrared temperature at a second detection point at a second moment, and acquire a second thermal change index based on a second change model, the third infrared temperature and the fourth infrared temperature.

[0082] The second data processing module is used to obtain the fluctuation index based on the first thermal change index and the second thermal change index, obtain the basic index range, and obtain the target index range based on the fluctuation index and the basic index range.

[0083] The monitoring module is used to obtain a first thermal conductivity index based on a first infrared temperature and a third infrared temperature, and a second thermal conductivity index based on a second infrared temperature and a fourth infrared temperature, and to obtain the solder paste printing result based on the first thermal conductivity index, the second thermal conductivity index, and the target index range.

[0084] In this embodiment, it should be noted that the specific method of performing the operation of the above-mentioned PCB solder paste printing result monitoring system has been described in detail in the embodiments of the PCB solder paste printing result monitoring method, and will not be elaborated here.

[0085] Figure 4 This is a block diagram of an electronic device illustrating a method for monitoring PCB solder paste printing results according to an exemplary embodiment. Figure 4 As shown, the electronic device 700 may include: a processor 701 and a memory 702. The electronic device 700 may also include one or more of a multimedia component 703, an I / O interface 704 (input / output interface), and a communication component 705.

[0086] The processor 701 controls the overall operation of the electronic device 700 to complete all or part of the steps in the PCB solder paste printing result monitoring method described above. The memory 702 stores 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, and application-related data such as contact data, 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 audio components. The screen may be, for example, a touchscreen, 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 memory 702 or transmitted via communication component 705. The audio component also includes at least one speaker for outputting audio signals. I / O interface 704 provides an interface between processor 701 and other interface modules, such as a keyboard, mouse, buttons, etc. These buttons may be virtual or physical buttons. 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 technologies, or a combination thereof, is not limited here. Therefore, the corresponding communication component 705 may include: a Wi-Fi module, a Bluetooth module, an NFC module, etc.

[0087] In an exemplary embodiment, the electronic device 700 may 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 perform the PCB solder paste printing result monitoring method described above.

[0088] In another exemplary embodiment, a computer-readable storage medium including program instructions is also provided, which, when executed by a processor, implement the steps of the PCB solder paste printing result monitoring method described above. For example, the computer-readable storage medium may be the memory 702 including program instructions, which may be executed by the processor 701 of the electronic device 700 to complete the PCB solder paste printing result monitoring method described above.

[0089] In another exemplary embodiment, a computer program product is also provided, comprising a computer program executable by a programmable device, the computer program having a code portion for performing the above-described PCB solder paste printing result monitoring method when executed by the programmable device.

[0090] The preferred embodiments of this disclosure have been described in detail above with reference to the accompanying drawings. However, this disclosure is not limited to the specific details of the above embodiments. Within the scope of the technical concept of this disclosure, various simple modifications can be made to the technical solutions of this disclosure, and these simple modifications all fall within the protection scope of this disclosure.

[0091] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, this disclosure will not describe the various possible combinations separately.

[0092] Furthermore, various different embodiments of this disclosure can be combined in any way, as long as they do not violate the spirit of this disclosure, they should also be regarded as the content disclosed in this disclosure.

[0093] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention.

Claims

1. A method for monitoring PCB solder paste printing results, characterized in that, include: The solder paste printing area, the first detection point, and the second detection point are obtained. The first detection point is located in the area directly illuminated by the infrared light source within the solder paste printing area, and the second detection point is located in the heat diffusion area within the solder paste printing area other than the area directly illuminated by the infrared light source. It acquires infrared information of infrared light directed toward the first detection point, and obtains a preset time period based on the infrared information, and acquires the first moment and the second moment at a preset time interval. At the first moment, the first infrared temperature is obtained at the first detection point, and at the second moment, the second infrared temperature is obtained at the first detection point. The first thermal change index is obtained based on the first change model, the first infrared temperature, and the second infrared temperature. The first change model is expressed as follows: ;in, As the primary indicator of thermal change, The first infrared temperature, The second infrared temperature, The temperature of the infrared light source, For a preset time period; And at the first moment, the third infrared temperature is obtained at the second detection point, and at the second moment, the fourth infrared temperature is obtained at the second detection point; The second thermal change index is obtained based on the second change model, the third infrared temperature, and the fourth infrared temperature. The second change model is expressed as follows: ;in, As the second thermal change index, The third infrared temperature, The fourth infrared temperature, The distance between the first and second detection points; The fluctuation index is obtained based on the first and second thermal change indices, and is expressed as follows: ;in, As a volatility indicator, This is the scaling factor; It also obtains the range of basic indicators based on historical good product data, and obtains the range of target indicators based on the fluctuation indicators and the range of basic indicators; The first thermal conductivity index is obtained based on the first infrared temperature and the third infrared temperature, and is expressed as follows: ;in, As the primary indicator of thermal conductivity, For the thermal conductivity of solder paste, The density of the solder paste, The specific heat capacity of solder paste; The second thermal conductivity index is obtained based on the second infrared temperature and the fourth infrared temperature, and the solder paste printing result is obtained based on 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 process of obtaining the target indicator range based on the volatility indicator and the basic indicator range includes: Obtain the minimum and maximum basic indicators based on the range of basic indicators; The target minimum indicator is obtained based on the volatility indicator and the basic minimum indicator, and the target maximum indicator is obtained based on the volatility indicator and the basic maximum indicator. The target indicator range is obtained based on the minimum and maximum target indicators.

3. The PCB solder paste printing result monitoring method according to claim 1, characterized in that, The process of obtaining solder paste printing results based on the first thermal conductivity index, the second thermal conductivity index, and the target thermal conductivity threshold includes: Determine whether both the first and second heat conduction indices are within the target range; If so, then the solder paste printing is determined to have no thickness defects; If not, then the solder paste printing is determined to have a thickness defect.

4. A PCB solder paste printing result monitoring system, characterized in that, The system is used to implement the PCB solder paste printing result monitoring method as described in any one of claims 1 to 3, the system comprising: The acquisition module is used to acquire the solder paste printing area and the first detection point and the second detection point located in the solder paste printing area, acquire the infrared information of the infrared light directed toward the first detection point, acquire a preset time period based on the infrared information, and acquire the first moment and the second moment at a preset time interval. The first data processing module is used to acquire a first infrared temperature at a first detection point at a first moment, and acquire a second infrared temperature at a second detection point at a second moment, acquire a first thermal change index based on a first change model, the first infrared temperature and the second infrared temperature, acquire a third infrared temperature at a second detection point at a first moment, acquire a fourth infrared temperature at a second detection point at a second moment, and acquire a second thermal change index based on a second change model, the third infrared temperature and the fourth infrared temperature. The second data processing module is used to obtain the fluctuation index based on the first thermal change index and the second thermal change index, obtain the basic index range, and obtain the 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 based on a first infrared temperature and a third infrared temperature, and a second thermal conductivity index based on a second infrared temperature and a fourth infrared temperature, and to obtain the solder paste printing result based on the first thermal conductivity index, the second thermal conductivity index, and the target index range.

5. An electronic device, characterized in that, include: A memory on which computer programs are stored; A processor is 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 3.

6. A non-transitory computer-readable storage medium having a computer program stored thereon, characterized in that, When executed by the processor, the program implements the PCB solder paste printing result monitoring method according to any one of claims 1 to 3.

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