LED chip mass transfer tin paste quantity detection and tin supplement system and method

Abstract

The application provides an LED chip mass transfer tin paste quantity detection and tin supplement system and method, and belongs to the technical field of LED mass transfer. The system solves the significant deficiencies of the prior art in high-precision requirements, complex PCB adaptability, defect rate control and micro-fabrication cost-effectiveness. The system comprises a tin paste supply module, a chip bearing and moving module, a tin paste dipping module, a tin paste quantity detection module, a control system and a tin supplement and removal module. The application realizes tin paste quantity detection on the LED chip through the tin paste quantity detection module, judges whether tin supplement or removal is needed through the control system, and realizes corresponding tin supplement or removal operation through the tin supplement and removal module. The application can improve the efficiency and quality of LED chip mass transfer and reduce production cost.

Description

Technical Field

[0001] This application relates to the field of LED mass transfer technology, and in particular to a system and method for detecting and replenishing solder paste during mass transfer of LED chips. Background Technology

[0002] In traditional mass transfer processes for LED chips, SMT stencil printing of solder paste is a common method. However, stencil printing has several drawbacks, such as high stencil manufacturing costs, limited lifespan, and the potential for uneven solder paste thickness and clogging during the printing process, affecting chip soldering quality and production efficiency. Furthermore, traditional processes lack precise control over solder paste volume, easily leading to insufficient or excessive solder on the chip, which in turn causes soldering defects such as cold solder joints and short circuits, reducing product reliability and yield.

[0003] Specifically, the core shortcomings of existing SMT stencil printing technology mainly lie in the bottlenecks of accuracy, consistency, and miniaturization:

[0004] 1. Limited solder paste deposition accuracy:

[0005] Stencil manufacturing limits: Micro-pitch components (such as 01005, 0.3mm pitch BGA) require extremely small openings. Existing laser cutting / electroforming technologies have problems with insufficient hole wall roughness and tension uniformity, which affect solder paste release and volume accuracy.

[0006] Alignment accuracy challenge: It is difficult for equipment vision systems and mechanical precision to achieve full-area nanometer-level alignment on high-density, large-size PCBs, and PCB deformation exacerbates this problem.

[0007] 2. Challenges in process stability and defect control:

[0008] Solder paste behavior is uncontrollable: the viscosity of solder paste is significantly affected by ambient temperature and humidity and shear rate, which can easily lead to defects such as insufficient filling, bridging, and spikes, especially in high aspect ratio openings.

[0009] The process is highly sensitive to fluctuations: the squeegee pressure / speed and demolding parameters require precise adjustment; even minor deformations or uneven support in the equipment / stencil / PCB can lead to printing defects. Stencil clogging and cleaning effectiveness depend on manual intervention.

[0010] 3. The contradiction between miniaturization and cost:

[0011] Approaching the physical limits: The solder paste release theory (area ratio / aspect ratio) for ultramicropores (<100μm) faces challenges, as the reduction in solder powder particle size exacerbates the risks of agglomeration, oxidation, and pore blockage.

[0012] High cost pressure: The investment, maintenance and consumables (soldering paste, wiping cloth) of high-precision steel mesh (nano-coating, special materials) and equipment are expensive, and fluctuations in yield further increase costs.

[0013] In summary, existing technologies have significant shortcomings in meeting high-precision requirements, adaptability to complex PCBs, defect rate control, and cost-effectiveness in miniaturization, which restricts the development of advanced packaging and miniaturization.

[0014] Therefore, developing a stencil-free and solder paste-free method for mass transfer of LED chips, and achieving accurate detection and replenishment of solder paste on the chip, is of great practical significance. Summary of the Invention

[0015] To address the aforementioned technical issues, this application proposes a system and method for detecting and replenishing solder paste during mass transfer of LED chips, which can improve the efficiency and quality of mass transfer of LED chips and reduce production costs.

[0016] The technical solution adopted in this application is: a system for detecting and replenishing solder paste in large-scale LED chip transfer, comprising:

[0017] Solder paste supply module: Used to deliver solder paste to the solder paste dispensing module, providing sufficient solder paste for chip dispensing;

[0018] Chip carrier and movement module: The transfer head accurately moves the chip to the position of the solder paste dispensing module. After the dispensing operation is completed, the chip is then moved to the solder paste amount detection module for detection.

[0019] Solder paste dispensing module: Used to bring the chip into contact with solder paste, and control the chip to dispense an appropriate amount of solder paste according to preset parameters and process requirements;

[0020] Solder paste quantity detection module: used to detect the amount of solder paste dipped into the chip in real time and transmit the detection data to the control system;

[0021] Control system: Receives detection data and compares it with the preset target solder paste amount to determine whether additional soldering or desoldering is required;

[0022] Solder replenishment and desoldering module: According to the instructions of the control system, it performs solder replenishment or desoldering operations on the chip. After the operation is completed, the chip is moved to the solder paste level detection module for detection to ensure that the solder paste level meets the requirements.

[0023] Furthermore, the solder paste quantity detection module includes:

[0024] Optical inspection module: It adopts a high-resolution 3D laser profilometer to obtain the three-dimensional contour information of the solder paste on the chip surface using triangulation; and transmits the acquired three-dimensional contour data to the control system, which uses image processing algorithms to segment and extract features of the solder paste area and calculate the actual volume of solder paste dipped.

[0025] Weight detection module: Includes a high-precision miniature weighing sensor installed below the transfer head, used to measure the weight change of the chip before and after being dipped in solder paste, and indirectly obtain the weight of the solder paste.

[0026] Furthermore, the control system includes an industrial computer, which has a built-in solder replenishment quantity balancing algorithm and a back-end soldering strategy. The solder replenishment quantity balancing algorithm takes the soldering quality requirements of the chip as the target, establishes a balancing model of the solder replenishment quantity based on the activity of the solder paste, the size of the chip and the pin distribution, and adopts a PID control algorithm to adjust the compensation coefficient according to the activity of the solder paste. Based on the error between the detected solder paste volume and the target solder paste volume, it calculates the volume of solder paste that needs to be replenished.

[0027] Furthermore, the back-end soldering strategy sets a threshold for back-end soldering based on the chip type and soldering requirements. When the amount of solder exceeds a certain range, the chip is transferred to the back-end soldering station for resoldering.

[0028] Furthermore, the solder replenishment and desoldering modules include:

[0029] The solder paste replenishment device consists of a miniature solder paste injector, a high-precision stepper motor, and a pressure control module. When a chip is found to be lacking solder, the pressure control module calculates the volume of solder paste that needs to be replenished based on the amount of solder missing, and controls the stepper motor to drive the injector to squeeze out an appropriate amount of solder paste to the area of ​​the chip lacking solder.

[0030] Excess solder paste handling device: It adopts a rotating solder tray with a surface coated with solder-absorbing material. By controlling the rotation speed and contact time, it can absorb excess solder paste. When too much solder paste is detected on the chip, the chip is brought into contact with the rotating solder tray for a certain period of time, so that the excess solder paste is absorbed by the solder tray.

[0031] Furthermore, after soldering, the amount of solder paste on the chip is checked again. If there is still a lack of solder, a pin-plating process is performed to add more solder.

[0032] A method for mass transfer of LED chips includes the following steps:

[0033] S1: Substrate and chip pretreatment: Prepare the target substrate and the LED chips to be transferred, screen the LED chips to be transferred to ensure that the chip quality is qualified, and arrange or group them as necessary; then clean and surface treat the screened LED chips to remove impurities and oxide layers from the chip surface.

[0034] S2: Chip Pickup: Using micro-nano manipulation technology, the chip is accurately picked up from the original carrier board and transferred to the transfer head;

[0035] S3: Solder paste application: Immerse the transfer head directly into the solder paste tank so that the chip is coated with an appropriate amount of solder paste;

[0036] S4: Solder paste quantity detection and replenishment: The LED chip mass transfer solder paste quantity detection and replenishment system is used to detect the chip before and after applying solder paste to determine whether soldering or replenishment is required.

[0037] S5: Chip Transfer: Using high-precision transfer equipment or motion platform, the chip dipped in solder paste is accurately transferred to a designated position on the target substrate; during the transfer process, the position and orientation of the chip are monitored in real time through a vision positioning system to ensure accurate placement of the chip;

[0038] S6: Soldering: Heating and soldering the chip transferred to the target substrate to melt the solder paste and achieve electrical connection and mechanical fixation between the chip and the target substrate;

[0039] S7: Electrical connection check: Check whether the electrical connection between the chip and the target substrate is normal;

[0040] S8: Quality Inspection: Perform comprehensive performance testing on the transferred chip.

[0041] Furthermore, in step S3, the amount of solder paste dipped into the chip is controlled by optimizing the shape of the transfer head, as well as the surface treatment and dipping parameters, including dipping depth, speed, and time.

[0042] Further, step S4 includes:

[0043] S41: Solder paste quantity detection: After the chip is dipped in solder paste, a 3D laser profilometer is used to acquire the three-dimensional contour data of the solder paste on the chip surface. The data is then transmitted to an industrial control computer for image processing and analysis to calculate the volume of the solder paste. At the same time, a miniature weighing sensor is used to measure the weight change of the chip before and after the solder paste is dipped in, and the weight of the solder paste is obtained. The volume and weight data are fused to determine whether the amount of solder paste dipped in the chip meets the process requirements.

[0044] S42: Solder shortage replenishment operation: When a chip is found to be short of solder, the system calculates the volume of solder paste that needs to be replenished based on the amount of solder missing; based on the activity level of the solder paste, the system selects appropriate solder replenishment pressure, speed and time parameters from the solder replenishment parameter database, controls the stepper motor to drive the syringe of the needle solder replenishment device, and squeezes an appropriate amount of solder paste onto the short solder part of the chip. During the solder replenishment process, the pressure and displacement of the syringe are monitored in real time.

[0045] S43: Solder excess handling operation: If too much solder paste is detected on the chip, control the rotation of the solder pad to bring the chip into contact with the solder pad for a certain period of time so that the excess solder paste is absorbed; after soldering, check the amount of solder paste on the chip again. If there is still a lack of solder, repeat the solder replenishment operation and adjust the amount and position of replenishment.

[0046] S44: Solder replenishment quantity balancing: Using a solder replenishment quantity balancing algorithm, the amount of solder paste and soldering quality feedback of the chip are monitored in real time based on the chip's soldering quality requirements, solder paste activity, chip size and pin distribution, and the amount and location of solder replenishment are dynamically adjusted; when the amount of solder replenishment exceeds 20% of the target volume, the chip is transferred to the back-end reflow soldering station, and the reflow soldering temperature profile and time parameters are adjusted according to the solder paste activity for reflow soldering.

[0047] Furthermore, the quality inspection in step S8 includes the brightness, color, and wavelength of the LED chip, and then determines whether the quality inspection is qualified. If the inspection is qualified, it proceeds to the post-processing stage; if the inspection is unqualified, it further determines whether the chip is repairable; for repairable chips, the chips are repaired and then the quality inspection is performed again; for unrepairable chips, the chips are transferred again, and steps S1-S8 are executed again. When all chips have been transferred, the quality inspection is qualified, and the post-processing is completed, the mass transfer of LED chips is completed.

[0048] The advantages of this application compared to existing technologies are as follows: This application provides a mass transfer manufacturing technology for LED chips that eliminates the need for stencils and solder paste printing. The core technology involves directly applying solder paste to the transfer head, replacing traditional stencil printing, significantly reducing stencil costs and process defects. The technical solution includes two major innovations:

[0049] 1) High-efficiency transfer process: After plasma cleaning, the chip is dipped into solder paste by a microstructure transfer head with optimized parameters (depth 0.5-1mm, speed 1-5mm / s); and high-precision visual positioning (accuracy ≤ ±5μm) ensures accurate chip placement, and customized reflow soldering curves ensure soldering quality.

[0050] 2) Intelligent closed-loop control of solder paste volume:

[0051] By combining 3D laser scanning (volume accuracy ±1μm) and weighing sensor (weight accuracy ±0.1mg) in a dual-modal detection, the amount of solder paste is determined comprehensively through a density model.

[0052] It can dynamically replenish solder: when solder is insufficient, the micro-needle device can precisely replenish solder as needed (step angle 0.01°); when there is too much solder, the high-speed rotating solder tray can absorb excess solder paste.

[0053] Adaptive control: Based on the solder paste activity level and chip characteristics, the PID algorithm is used to adjust the solder replenishment parameters in real time, and automatic resoldering is triggered when the limit is exceeded.

[0054] Advantages: Completely avoids stencil clogging / uneven solder paste issues, improves solder paste control precision by more than 50%, reduces the risk of cold solder joints / short circuits, and significantly optimizes yield and production efficiency. Attached Figure Description

[0055] The following description, in conjunction with the accompanying drawings, further illustrates this application:

[0056] Figure 1 A flowchart illustrating the method provided in this application embodiment;

[0057] Figure 2 This is a schematic diagram of the system structure provided in the embodiments of this application;

[0058] Figure 3 A flowchart of the solder replenishment quantity balancing algorithm provided in the embodiments of this application;

[0059] Figure 4 A schematic diagram of a three-dimensional model of the system provided in this application embodiment;

[0060] In the diagram: 1 is the transfer drive layer, 11 is the high-precision linear motor module, 12 is the vacuum adsorption control unit, 2 is the chip carrier layer, 21 is the chip surface, 22 is the chip bottom surface, 3 is the solder replenishment / soldering execution layer, and 31 is the needle-plating solder replenishment injector module. Detailed Implementation

[0061] like Figures 1 to 4 As shown, this application provides a system for detecting and replenishing solder paste during mass transfer of LED chips, such as... Figure 2 As shown, the system includes:

[0062] Solder paste supply module: delivers solder paste to the solder paste dispensing module through pipes or other means, providing sufficient solder paste for chip dispensing.

[0063] Chip carrier and movement module: Accurately moves the chip to the position of the solder paste dispensing module, completes the dispensing operation, and then moves the chip to the solder paste quantity detection module for detection.

[0064] Solder paste application module: Makes the chip come into contact with solder paste, and controls the chip to apply an appropriate amount of solder paste according to preset parameters and process requirements.

[0065] Solder paste quantity detection module: It uses optical detection, weight detection and other technologies to detect the amount of solder paste dipped into the chip in real time and transmits the detection data to the control system.

[0066] The solder paste quantity detection module includes:

[0067] Optical Inspection Module: Employs a high-resolution 3D laser profilometer (such as the Keyence LK-G series) to acquire the three-dimensional contour information of solder paste on the chip surface using triangulation. Its measurement accuracy reaches ±1μm, with a scanning speed of 10kHz, enabling rapid and accurate detection of the solder paste's height, area, and volume. The acquired 3D contour data is then transmitted to an industrial control computer, where image processing algorithms (such as the OpenCV library) are used to segment and extract features from the solder paste area, calculating the actual volume of solder paste applied.

[0068] The weight detection module includes a high-precision miniature weighing sensor (such as the HBM PW25 series) mounted below the transfer head. This sensor measures the weight change of the chip before and after solder paste application, indirectly determining the weight of the solder paste. The miniature weighing sensor has a range of 0-5g and an accuracy of ±0.1mg. By fusing the solder paste volume data obtained from the optical detection module with the weight data from the weight detection module, and establishing a solder paste density model (considering the composition and activity of the solder paste), the module can more accurately determine whether the amount of solder paste meets the process requirements.

[0069] Control system: Receives detection data and compares it with the preset target solder paste amount to determine whether solder replenishment or desoldering is required. If necessary, it sends instructions to the solder replenishment and desoldering modules.

[0070] The control system includes an industrial computer, which has a built-in solder replenishment quantity balancing algorithm module and a back-end soldering strategy.

[0071] The algorithm works by establishing a solder paste replenishment quantity balance model based on factors such as solder paste activity, chip size, and pin distribution, with the target being the chip's soldering quality requirements. This model considers the diffusion and shrinkage characteristics of the solder paste during the soldering process, as well as the impact of different solder paste activities on soldering strength. By monitoring the amount of solder paste and soldering quality feedback in real time, the algorithm dynamically adjusts the amount and location of solder paste replenishment to achieve optimal balance in the replenishment process.

[0072] Algorithm Implementation: A PID control algorithm is employed, adjusting the solder paste activity correction coefficient based on the solder paste activity. The required solder paste volume is calculated based on the error between the detected solder paste volume and the target solder paste volume, and the amount of solder to be added is limited.

[0073] The specific process of the algorithm is as follows: Figure 3 As shown, starting from acquiring initial data, the process involves calculating the target solder paste amount, judging errors, determining the activity level, calculating and adjusting the compensation amount, and finally deciding whether back-end resoldering is needed based on the solder replenishment situation. The entire process forms a closed loop, ensuring precise control of the chip's solder paste amount and improving soldering quality. Through differentiated processing of different activity solder pastes and reasonable limitations on the compensation amount, the problems of excessive solder replenishment or removal are effectively avoided, ensuring the stability and reliability of the production process.

[0074] The solder paste quantity balance model takes chip soldering quality as its core objective, integrates key factors such as solder paste activity and chip characteristics, and achieves dynamic and precise control of solder paste quantity through a PID control algorithm. The core mathematical logic is as follows:

[0075] (I) Core Objective Function

[0076] The model aims to approximate the actual solder paste amount Qactual on the chip with the target solder paste amount Qtarget, minimizing the accumulated solder replenishment error. The objective function is:

[0077] ;

[0078] In the formula: J is the target optimization index (the weighted integral of the squared error and the squared control quantity).

[0079] e(τ) = Qtarget(τ) - Qactual(τ) represents the solder paste quantity deviation at time τ (target value - actual value).

[0080] u(τ) is the solder replenishment control amount at time τ (syringe extrusion amount / solder tray adsorption amount).

[0081] λ is the weighting coefficient for solder replenishment control (0.01~0.1, adjusted according to solder paste activity).

[0082] (II) Calculation model for target solder paste amount Qtarget

[0083] The target solder paste amount is determined by the chip characteristics and soldering requirements, and is expressed as:

[0084] Qtarget=ks·Spad·hopt+Ka·f(A);

[0085] Where: ks represents the substrate pad correction factor (0.9~1.1, which is related to the pad material and roughness).

[0086] Spad = n·ssingle, representing the total pad area (n is the number of pins, ssingle is the area of ​​a single pad, in μm). 2 );

[0087] hopt indicates the optimal solder paste thickness (20~50μm);

[0088] Ka represents the solder paste activity correction coefficient, also known as the solder paste activity adjustment compensation coefficient;

[0089] f(A) = 10⁻³·(1-A)·Spad represents the activity compensation function (A is the solder paste activity level, A∈[0,1], unit μm). 3 ).

[0090] (III) PID Soldering Control Algorithm

[0091] The solder replenishment control quantity u(t) is calculated using a PID algorithm, integrating proportional (P), integral (I), and derivative (D) regulation:

[0092] u(t) = Kp·e(t) + ;

[0093] PID core parameters:

[0094] Kp: Proportioning coefficient (high activity 0.8~1.2, medium activity 1.0~1.5, low activity 1.2~1.8);

[0095] Ki = Kp / (5~10): Integral coefficient (to eliminate static error);

[0096] Kd=Kp·(0.1~0.3): Differential coefficient (to suppress overshoot).

[0097] Solder paste quantity deviation e(t) calculation (dual-modal detection fusion):

[0098] Combining 3D laser volume detection and weighing detection improves deviation accuracy:

[0099] Qactual=α+βα·Vlaser+β·mweigh / ρsoldere(t)=Qtarget-Qactual;

[0100] In the formula: α=0.6, which represents the volume detection weight (3D laser accuracy ±1μm);

[0101] β=0.4, representing the weight detection weight (weighing sensor accuracy ±0.1mg).

[0102] ρsolder = 7.3 × 10 -9 ~7.5×10 -9 g / μm 3 , indicates the density of solder paste at room temperature;

[0103] Vlaser indicates the volume of solder paste detected by laser (unit: μm). 3 );

[0104] mweigh indicates the weight of the solder paste measured by weighing (in grams).

[0105] (iv) Constraints and back-end welding triggering

[0106] 1. Solder replenishment constraint: -0.1Qtarget≤u(t)≤0.2Qtarget (desoldering not exceeding 10%, solder replenishment not exceeding 20%).

[0107] 2. Equipment parameter constraints: syringe displacement ≤ 50μm, solder tray rotation speed ≤ 1000rpm;

[0108] 3. Re-soldering trigger: When the amount of solder added exceeds the target by 20%, the back-end re-soldering is initiated, and the correction parameters are as follows:

[0109] Tpeak=Tbase+kt·Qtarget u(t)-0.2Qtarget tweld=tbase+kt'·Qtarget u(t)-0.2Qtarget;

[0110] In the formula: Tpeak represents the peak temperature of the soldering repair, in °C, and its value is obtained by correcting the base peak temperature based on the amount of solder added; Tbase represents the base peak temperature of the soldering repair, which is the reference value of the peak temperature, ranging from 230 to 250 °C, and is the basic parameter for correcting the soldering repair temperature; kt represents the correction coefficient for the peak temperature of the soldering repair, in °C, ranging from 5 to 10 °C, and is used to quantify the correction range of the peak temperature due to the amount of solder added; tweld represents the duration of the soldering repair, in seconds, and its value is obtained by correcting the base soldering repair time based on the amount of solder added; tbase represents the base duration of the soldering repair, which is the reference value of the soldering repair time, ranging from 60 to 90 seconds, and is the basic parameter for correcting the soldering repair time; kt' represents the correction coefficient for the duration of the soldering repair, in seconds, ranging from 10 to 15 seconds, and is used to quantify the correction range of the duration of the soldering repair due to the amount of solder added.

[0111] Tbase=230-250℃, kt=5~10℃;

[0112] tbase=60-90s, kt'=10~15s.

[0113] Ka is the core correction parameter of the PID algorithm, used to match the flow differences of different active solder pastes and optimize the soldering accuracy. Its specific meaning and calculation are explained below:

[0114] (I) Core Definitions and Range of Values

[0115] Definition: The coefficients of PID parameters are dynamically adjusted according to the solder paste activity level to solve the problems of excessive soldering of high-activity solder paste and insufficient soldering of low-activity solder paste;

[0116] Value range: Ka∈[0.8,1.2], the higher the activity, the smaller the coefficient, and the lower the activity, the larger the coefficient.

[0117] (II) Classification of Solder Paste Activity Levels

[0118] As shown in Table 1 below.

[0119] Table 1. Classification of Solder Paste Activity Levels

[0120] .

[0121] (III) Compensation Coefficient Calculation Model

[0122] Linear interpolation calculation based on solder paste activity value: Ka = 1.2 - 0.4 × (C / Cmax);

[0123] Where C represents the actual flux activity percentage (C∈[0,100%]); Cmax=85% represents the high activity threshold;

[0124] Example: Ka = 0.8 for high activity (C = 85%), Ka ≈ 0.91 for medium activity (C = 75%), and Ka ≈ 1.01 for low activity (C = 64%).

[0125] (iv) Application in PID Algorithm

[0126] The core parameters of the PID controller are corrected using Ka: Kp′=Kp×Ka, Ki′=Ki×Ka, Kd′=Kd×Ka; where Kp′ is the corrected proportional coefficient, Ki′ is the corrected integral coefficient, and Kd′ is the corrected derivative coefficient.

[0127] Baseline parameters (default for medium activity): Kp=1.2, Ki=0.15, Kd=0.3;

[0128] After high activity correction: Kp′=0.96, Ki′=0.12, Kd′=0.24;

[0129] After low activity correction: Kp′=1.21, Ki′=0.15, Kd′=0.30.

[0130] (v) Dynamic adjustment rules

[0131] 1. Real-time calibration: When the diffusion area deviation exceeds ±8% after solder replenishment, adjust Ka±0.01 for every 1% exceeding the deviation.

[0132] 2. Environmental adaptability: For every 10% increase in humidity, the Ka of low-activity solder paste increases by an additional 0.02.

[0133] 3. Threshold limitation: After correction, Ka∈[0.7,1.3] to avoid parameter overflow.

[0134] (vi) Application effect

[0135] The soldering error of high-activity solder paste was reduced from ±7% to ±3.2%;

[0136] The soldering error for low-activity solder paste has been reduced from ±9% to ±4.5%.

[0137] The soldering strength consistency of different active solder pastes is improved by more than 20%.

[0138] Back-end soldering strategy: A threshold for back-end soldering is set based on the chip type and soldering requirements. When the amount of solder exceeds a certain range (e.g., exceeding 20% ​​of the target volume), the chip is transferred to the back-end soldering station for further soldering. Back-end soldering uses a reflow soldering process; the temperature profile and time parameters are adjusted according to the solder paste's activity to ensure soldering quality.

[0139] Solder replenishment and desoldering module: According to the instructions of the control system, it performs solder replenishment or desoldering operations on the chip. After the operation is completed, the chip is moved to the solder paste level detection module for detection to ensure that the solder paste level meets the requirements.

[0140] The solder replenishment and desoldering modules include:

[0141] The solder paste replenishment device consists of a miniature solder paste injector, a high-precision stepper motor, and a pressure control module. The miniature solder paste injector has an inner diameter of 0.1mm, allowing for precise control of the solder paste extrusion volume. The stepper motor has a step angle of 0.01°, enabling precise control of minute displacements. When a chip is detected to be lacking solder, the pressure control module calculates the required volume of solder paste based on the amount lacking and controls the stepper motor to drive the injector to extrude an appropriate amount of solder paste to the deficient area of ​​the chip. During the replenishment process, the accuracy of the replenishment amount is ensured by real-time monitoring of the injector's pressure and displacement.

[0142] Solder replenishment parameter optimization: Solder pastes with different activity levels exhibit varying flowability and wettability during the replenishment process. Based on the solder paste's activity level (e.g., high, medium, low), parameters such as replenishment pressure, speed, and time are adjusted. For example, for low-activity solder paste, the replenishment pressure and heating temperature are appropriately increased to improve its flowability. Through extensive process experiments, a database of replenishment parameters for different activity levels of solder paste is established to provide a reference for actual production.

[0143] The solder paste handling unit (soldering device) uses a rotating soldering tray coated with a special solder-absorbing material (such as porous ceramic). The rotation speed of the soldering tray is adjustable from 0-1000 rpm. By controlling the rotation speed and contact time, excess solder paste is absorbed. When excessive solder paste is detected on the chip, the chip is brought into contact with the rotating soldering tray for a certain period of time, allowing the excess solder paste to be absorbed. After soldering, the solder paste level on the chip is checked again. If there is still insufficient solder, a pin bonding process is performed for additional solder.

[0144] Tinning adjustment after soldering: When performing tinning after soldering, adjust the amount and position of tinning according to the amount of solder paste remaining after soldering and the soldering requirements of the chip to ensure that the final amount of solder paste meets the process standards.

[0145] Back-end soldering station: When the amount of solder exceeds a certain threshold, the control system moves the chip to the back-end soldering station for resoldering to ensure soldering quality.

[0146] This schematic diagram illustrates the main components and workflow of the chip solder paste dispensing detection and replenishment system. The various modules cooperate with each other to form a closed-loop control system, ensuring that the amount of solder paste dispensed by the chip meets the process requirements.

[0147] This application also provides a method for mass transfer of LED chips, such as... Figure 1 As shown, it includes the following steps:

[0148] S1: Substrate and chip pretreatment: Prepare the target substrate and the LED chips to be transferred. The target substrate is used to prepare for the subsequent chip transfer. Ensure that the surface of the target substrate is clean and flat. Perform cleaning, coating and other operations as needed.

[0149] The LED chips to be transferred are screened to ensure they meet quality standards and then arranged or grouped as necessary. The screened LED chips are then cleaned and surface-treated to remove impurities and oxide layers, improving the wettability between the chip and solder paste. Plasma cleaning or chemical cleaning methods can be used. After cleaning, a thin layer of flux is applied to the chip surface to enhance the soldering effect.

[0150] Specifically, the LED chip can be placed in a plasma cleaning device and cleaned for 5-10 minutes under specific gas atmosphere (such as argon or oxygen) and power conditions to remove impurities and oxide layers from the chip surface. Then, a layer of flux is evenly coated onto the chip surface using a spray method.

[0151] S2: Chip Pickup: Using micro-nano manipulation techniques, such as electrostatic adsorption and vacuum adsorption, the chip is accurately picked up from the original carrier and transferred to the transfer head.

[0152] S3: Solder Paste Application: The transfer head is directly immersed in the solder paste bath to allow the chip to pick up an appropriate amount of solder paste. The amount of solder paste applied to the chip is controlled by optimizing the design of the transfer head and the application parameters (such as application depth, speed, and time).

[0153] In this step of the embodiment, the dipping depth is controlled at 0.5-1mm, the dipping speed is 1-5mm / s, and the dipping time is 1-3s. By optimizing the shape and surface treatment of the transfer head, such as using a microstructured surface, the uniformity of solder paste dipping is improved.

[0154] S4: Solder Paste Amount Detection and Replenishment: Based on the LED chip mass transfer solder paste amount detection and replenishment system, the chip is inspected before and after solder paste application to determine whether soldering or replenishment is needed, including:

[0155] S41: Solder Paste Amount Detection: After the chip is dipped in solder paste, a 3D laser profilometer acquires the three-dimensional contour data of the solder paste on the chip surface. This data is transmitted to an industrial control computer for image processing and analysis to calculate the volume of the solder paste. Simultaneously, a miniature weighing sensor measures the weight change of the chip before and after solder paste application, obtaining the weight of the solder paste. The volume and weight data are then combined to determine whether the amount of solder paste applied to the chip meets the process requirements.

[0156] S42: Solder Shortage Replenishment Operation: When a solder shortage is detected on a chip, the system calculates the required volume of solder paste to be replenished based on the amount of solder missing. According to the solder paste's activity level, appropriate replenishment parameters such as pressure, speed, and time are selected from the replenishment parameter database. A stepper motor drives the syringe of the solder paste replenishment device to extrude an appropriate amount of solder paste to the solder-deficient area of ​​the chip. The pressure and displacement of the syringe are monitored in real time during the replenishment process.

[0157] S43: Solder Excess Handling Operation: If excessive solder paste is detected on the chip, control the rotation of the solder pad to bring the chip into contact with the pad for a certain period of time, allowing the excess solder paste to be absorbed. After soldering, check the solder paste level on the chip again. If solder is still insufficient, repeat the solder replenishment operation, adjusting the amount and location of the replenishment.

[0158] S44: Solder Replenishment Balance: Utilizing a solder replenishment balance algorithm, the system monitors the solder paste quantity and soldering quality feedback in real time based on factors such as chip soldering quality requirements, solder paste activity, chip size, and pin distribution. It dynamically adjusts the amount and location of solder replenishment. When the amount of solder replenishment exceeds 20% of the target volume, the chip is transferred to the back-end reflow soldering station, where the reflow temperature profile and time parameters are adjusted according to the solder paste activity for further reflow soldering.

[0159] S5: Chip Transfer: Using high-precision transfer equipment or motion platforms, chips dipped in solder paste are accurately transferred to designated positions on the target substrate. During the transfer process, the chip's position and orientation are monitored in real time through a vision positioning system to ensure accurate placement.

[0160] In this step of the embodiment, a high-precision transfer device (such as a flip chip mounter) can be used to monitor the position and orientation of the chip in real time through a vision positioning system, accurately transferring the chip dipped in solder paste onto the target substrate. During the transfer process, the placement accuracy of the chip is ensured to be within ±5μm.

[0161] S6: Soldering: The chip transferred to the target substrate is heated and soldered to melt the solder paste and achieve electrical connection and mechanical fixation between the chip and the target substrate. Methods such as hot pressing and adhesives can be used to firmly fix the chip to the target substrate, ensuring that the chip will not shift during subsequent use. Then, based on the characteristics of the solder paste and the chip's soldering requirements, the soldering process parameters (such as soldering temperature, time, pressure, etc.) are optimized.

[0162] In this step of the embodiment, the chip transferred to the target substrate is placed in a reflow oven. Based on the characteristics of the solder paste and the soldering requirements of the chip, appropriate soldering temperature profiles and time parameters are set. For example, for common Sn-Ag-Cu solder paste, the peak soldering temperature is controlled at 230-250℃, and the soldering time is 60-90 seconds.

[0163] S7: Electrical connection check: Check whether the electrical connection between the chip and the target substrate is normal to ensure that the chip can work properly.

[0164] S8: Quality Inspection: A comprehensive performance test is performed on the transferred chips, including parameters such as brightness, color, and wavelength. The quality of the chip is then assessed based on the test results. If the chip passes the test, it proceeds to the post-processing stage, such as packaging and applying a protective layer. If the chip fails the test, its repairability is further assessed. Repairable chips are repaired and then re-tested. Unrepairable chips are either transferred again or the entire process is repeated. Once all chips have been transferred, passed quality inspection, and completed post-processing, the mass transfer is complete.

[0165] Figure 4 A feasible system partial structure embodiment is given. The figure shows, from top to bottom, a transfer driving layer 1 (i.e., transfer head), a chip carrier layer 2 (i.e., and solder replenishment / removal execution layer 3). The transfer driving layer 1 uses a high-precision linear motor module 11 and a vacuum adsorption control unit 12 to achieve adsorption and transfer of the chip carrier layer. The positioning accuracy of the high-precision linear motor module 11 is 0.5μm, and the negative pressure range of the vacuum adsorption control unit 12 is -0.05~0.1Mpa. Furthermore, a miniature weighing sensor is installed on the transfer driving layer 1, which can measure the weight of the chip carrier layer 2 before and after the mass transfer, thereby detecting the amount of solder paste dipped onto the chip carrier layer 2 after the solder paste is dipped.

[0166] The top surface of the chip carrier layer 2 is an array of LED chips that have already undergone mass transfer, and the bottom surface of the chip carrier layer 2 is the electrode pads of the arranged LED chips (illustrated by the upper and lower layers separated in the middle in the figure. Those skilled in the art should understand that the two separated layers are actually a whole. The figure is a visual illustration to more intuitively show the arrangement of the chips and electrode pads). By using a 3D laser profilometer to perform contour detection on the top and bottom surfaces of the chip carrier layer, it is possible to detect the arrangement of LED chips on the top surface and the shape of the LED chip electrode pads on the bottom surface. This allows for more accurate positioning of electrode pads with excess solder or those requiring additional solder.

[0167] The solder replenishment / removal execution layer 3 includes a needle-plating solder replenishment injector module 31 and a stepper motor drive unit. The solder replenishment / removal execution layer 3 can move up and down through the stepper motor drive unit, and the needle-plating solder replenishment injector module 31 can rotate in the plane, so that the solder replenishment / removal execution layer 3 can be accurately moved to the position of the electrode pad to be soldered or removed.

[0168] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application 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 therein. 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 this application.

Claims

1. A system for detecting and replenishing solder paste during mass transfer of LED chips, characterized in that: include: Solder paste supply module: Used to deliver solder paste to the solder paste dispensing module, providing sufficient solder paste for chip dispensing; Chip carrier and movement module: The transfer head accurately moves the chip to the position of the solder paste dispensing module. After the dispensing operation is completed, the chip is then moved to the solder paste amount detection module for detection. Solder paste dispensing module: Used to bring the chip into contact with solder paste, and control the chip to dispensing an appropriate amount of solder paste according to preset parameters and process requirements; Solder paste quantity detection module: used to detect the amount of solder paste dipped into the chip in real time and transmit the detection data to the control system; Control system: Receives detection data and compares it with the preset target solder paste amount to determine whether additional soldering or desoldering is required; Solder replenishment and desoldering module: According to the instructions of the control system, it performs solder replenishment or desoldering operations on the chip. After the operation is completed, the chip is moved to the solder paste level detection module for detection to ensure that the solder paste level meets the requirements.

2. The LED chip mass transfer solder paste quantity detection and replenishment system according to claim 1, characterized in that: The solder paste quantity detection module includes: Optical inspection module: It adopts a high-resolution 3D laser profilometer to obtain the three-dimensional contour information of the solder paste on the chip surface using triangulation; and transmits the acquired three-dimensional contour data to the control system, which uses image processing algorithms to segment and extract features of the solder paste area and calculate the actual volume of solder paste dipped. Weight detection module: Includes a high-precision miniature weighing sensor installed below the transfer head, used to measure the weight change of the chip before and after being dipped in solder paste, and indirectly obtain the weight of the solder paste.

3. The LED chip mass transfer solder paste quantity detection and replenishment system according to claim 1, characterized in that: The control system includes an industrial computer, which has a built-in solder replenishment quantity balancing algorithm and a back-end soldering strategy. The solder replenishment quantity balancing algorithm takes the soldering quality requirements of the chip as the target, establishes a balancing model of the amount of solder to be replenished based on the activity of the solder paste, the size of the chip and the pin distribution, and uses a PID control algorithm to adjust the compensation coefficient according to the activity of the solder paste. Based on the error between the detected solder paste volume and the target solder paste volume, it calculates the volume of solder paste that needs to be replenished.

4. The LED chip mass transfer solder paste quantity detection and replenishment system according to claim 3, characterized in that: The back-end soldering strategy sets a threshold for back-end soldering based on the chip type and soldering requirements. When the amount of solder exceeds a certain range, the chip is transferred to the back-end soldering station for resoldering.

5. The LED chip mass transfer solder paste quantity detection and replenishment system according to claim 1, characterized in that: The solder replenishment and desoldering modules include: The solder paste replenishment device consists of a miniature solder paste injector, a high-precision stepper motor, and a pressure control module. When a chip is found to be lacking solder, the pressure control module calculates the volume of solder paste that needs to be replenished based on the amount of solder missing, and controls the stepper motor to drive the injector to squeeze out an appropriate amount of solder paste to the area of ​​the chip lacking solder. Excess solder paste handling device: It adopts a rotating solder tray with a surface coated with solder-absorbing material. By controlling the rotation speed and contact time, it can absorb excess solder paste. When too much solder paste is detected on the chip, the chip is brought into contact with the rotating solder tray for a certain period of time, so that the excess solder paste is absorbed by the solder tray.

6. The LED chip mass transfer solder paste quantity detection and replenishment system according to claim 5, characterized in that: After soldering, the amount of solder paste on the chip is checked again. If there is still a lack of solder, a pin-plating process is performed to add more solder.

7. A method for mass transfer of LED chips, characterized in that: Includes the following steps: S1: Substrate and chip pretreatment: Prepare the target substrate and the LED chips to be transferred, screen the LED chips to be transferred to ensure that the chip quality is qualified, and arrange or group them as necessary; then clean and surface treat the screened LED chips to remove impurities and oxide layers from the chip surface. S2: Chip Pickup: Using micro-nano manipulation technology, the chip is accurately picked up from the original carrier board and transferred to the transfer head; S3: Solder paste application: Immerse the transfer head directly into the solder paste tank so that the chip is coated with an appropriate amount of solder paste; S4: Solder paste quantity detection and replenishment: Using the LED chip mass transfer solder paste quantity detection and replenishment system as described in any one of claims 1-6, the chip is detected before and after being dipped in solder paste to determine whether soldering or replenishment is required. S5: Chip Transfer: Using high-precision transfer equipment or motion platform, the chip dipped in solder paste is accurately transferred to a designated position on the target substrate; during the transfer process, the position and orientation of the chip are monitored in real time through a vision positioning system to ensure accurate placement of the chip; S6: Soldering: Heating and soldering the chip transferred to the target substrate to melt the solder paste and achieve electrical connection and mechanical fixation between the chip and the target substrate; S7: Electrical connection check: Check whether the electrical connection between the chip and the target substrate is normal; S8: Quality Inspection: Perform comprehensive performance testing on the transferred chip.

8. The method for mass transfer of LED chips according to claim 7, characterized in that: In step S3, the amount of solder paste dipped into the chip is controlled by optimizing the shape of the transfer head, surface treatment, and dipping parameters, including dipping depth, speed, and time.

9. The method for mass transfer of LED chips according to claim 7, characterized in that: Step S4 includes: S41: Solder paste quantity detection: After the chip is dipped in solder paste, a 3D laser profilometer is used to acquire the three-dimensional contour data of the solder paste on the chip surface. The data is then transmitted to an industrial control computer for image processing and analysis to calculate the volume of the solder paste. At the same time, a miniature weighing sensor is used to measure the weight change of the chip before and after the solder paste is dipped in, and the weight of the solder paste is obtained. The volume and weight data are fused to determine whether the amount of solder paste dipped in the chip meets the process requirements. S42: Solder shortage replenishment operation: When a chip is found to be short of solder, the system calculates the volume of solder paste that needs to be replenished based on the amount of solder missing; based on the activity level of the solder paste, the system selects appropriate solder replenishment pressure, speed and time parameters from the solder replenishment parameter database, controls the stepper motor to drive the syringe of the needle solder replenishment device, and squeezes an appropriate amount of solder paste onto the short solder part of the chip. During the solder replenishment process, the pressure and displacement of the syringe are monitored in real time. S43: Solder excess handling operation: If too much solder paste is detected on the chip, control the rotation of the solder pad to bring the chip into contact with the solder pad for a certain period of time so that the excess solder paste is absorbed; after soldering, check the amount of solder paste on the chip again. If there is still a lack of solder, repeat the solder replenishment operation and adjust the amount and position of replenishment. S44: Solder replenishment quantity balancing: Using a solder replenishment quantity balancing algorithm, the amount of solder paste and soldering quality feedback of the chip are monitored in real time based on the chip's soldering quality requirements, solder paste activity, chip size and pin distribution, and the amount and location of solder replenishment are dynamically adjusted; when the amount of solder replenishment exceeds 20% of the target volume, the chip is transferred to the back-end reflow soldering station, and the reflow soldering temperature profile and time parameters are adjusted according to the solder paste activity for reflow soldering.

10. The method for mass transfer of LED chips according to claim 7, characterized in that: Step S8 involves quality inspection of the LED chip's brightness, color, and wavelength. The quality of the inspection is then assessed to determine if it is up to standard. If it is up to standard, the chip proceeds to the post-processing stage. If it fails the inspection, the chip is further assessed to determine if it is repairable. Repairable chips are repaired and then re-inspected. Unrepairable chips are transferred again, and steps S1-S8 are executed again. Once all chips have been transferred, passed quality inspection, and completed post-processing, the mass transfer of LED chips is complete.

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