SMT (surface mount technology)

Abstract

The invention provides an SMT (Surface Mount Technology) process, relates to the technical field of electronic manufacturing, remarkably improves the chip mounting precision by adopting advanced technologies such as plasma cleaning, laser positioning, visual identification, machine learning, sectional temperature control and automatic detection, can realize submicron chip mounting precision, and improves the chip mounting efficiency. And the connection deviation between the element and the circuit board is effectively reduced.

Description

Technical Field

[0001] The present invention relates to the field of electronic manufacturing technology, and particularly to an SMT (Surface Mount Technology) chip mounting process. Background Art

[0002] In the existing SMT chip mounting process, there are some common problems. For example, the chip mounting accuracy is not high enough, resulting in deviations in the connection between electronic components and the circuit board, which affects the performance and stability of electronic products. In addition, the traditional chip mounting process has low efficiency, especially when dealing with small and high-precision electronic components, which requires a large amount of time and manpower. At the same time, the welding quality is difficult to guarantee, and defects such as false soldering and short circuit are likely to occur, increasing the defective rate and maintenance cost of products. Moreover, the existing process lacks flexibility in dealing with complex circuit board layouts and diverse component requirements, and it is difficult to meet the rapidly changing market demands. Additionally, during the chip mounting process, the circuit board and components will undergo thermal deformation under the influence of heat, etc., further affecting the chip mounting accuracy, and the existing process often lacks effective thermal deformation compensation measures. During the reflow soldering process, oxygen in the air will react with the solder to cause oxidation, reducing the welding quality and resulting in problems such as decreased solder joint strength and reliability. The existing process also needs to strengthen the protection measures in this regard. In addition, in the traditional solder paste printing process, unreasonable stencil opening design and inaccurate squeegee pressure control are likely to cause uneven solder paste printing, affecting the subsequent welding quality and component mounting effect. Summary of the Invention

[0003] The purpose of the present invention is to provide an SMT chip mounting process to solve the problems of low chip mounting accuracy, low efficiency, unstable welding quality, and lack of flexibility in the existing technology, and at the same time effectively address the problem of reduced accuracy caused by thermal deformation during the chip mounting process, improve the quality of reflow soldering, and optimize the solder paste printing effect.

[0004] To solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0005] An SMT chip mounting process includes the following steps:

[0006] Pretreatment stage: Clean and surface-treat the circuit board, and use plasma cleaning technology to remove impurities such as oil stains and oxides on the surface of the circuit board, improving the activity and adhesion of the circuit board surface. At the same time, inspect and screen the electronic components to ensure that the quality and specifications of the components meet the requirements.

[0007] Solder paste printing: Use high-precision printing equipment and adopt laser positioning technology to accurately control the printing position and thickness of the solder paste. Adopt a stencil design with a gradient change in the aperture ratio. The aperture ratio in the central area of the stencil is 92%, and the aperture ratio in the edge area is 88% to adapt to the solder paste demand at different positions. Combine a pressure feedback system to dynamically adjust the squeegee pressure, which can be adjusted within the range of 80 - 120N according to the actual printing situation. Optimize the solder paste formula and printing parameters according to the type and size of electronic components to ensure that the solder paste can evenly cover the pads on the circuit board.

[0008] Chip placement operation: Adopt a vision recognition system and a high-precision chip mounter to perform real-time positioning and adjustment of electronic components. Use machine learning algorithms to automatically adjust the working parameters of the chip mounter according to the shape, size, and position information of the components, realizing fast and accurate chip placement operations. For small and high-precision components, adopt vacuum adsorption and micro-positioning technology to improve the placement accuracy and stability.

[0009] Dynamic thermal deformation compensation: In the chip placement stage, introduce a dynamic thermal deformation compensation system (DTCS) to correct the component position in real time. The DTCS includes an infrared thermal imaging module, a laser displacement sensor, and a deformation prediction algorithm based on LSTM (Long Short-Term Memory network).

[0010] The infrared thermal imaging module monitors the temperature distribution of the circuit board and components during the chip placement process in real time, obtains temperature data, and provides basic information for thermal deformation analysis. Since temperature change is one of the main factors causing thermal deformation, by accurately monitoring the temperature, the potential risk areas of thermal deformation can be better understood.

[0011] The laser displacement sensor measures the surface morphology of the circuit board and components in real time, obtains real-time displacement data, and accurately captures the tiny position changes caused by thermal deformation or other factors.

[0012] The deformation prediction algorithm based on LSTM comprehensively analyzes and processes the data obtained by the infrared thermal imaging module and the laser displacement sensor. The LSTM network can effectively process time series data. By learning and analyzing historical temperature data, displacement data, and other relevant process parameters, it predicts the thermal deformation trend of the circuit board and components under the current process conditions. According to the prediction results, the motion parameters of the chip mounter are adjusted in real time to correct the placement position of the components, compensating for the position deviation caused by thermal deformation, and ensuring that the components can be accurately placed at the target position.

[0013] Reflow soldering: In the reflow soldering process, adopt segmented temperature control technology, and set a reasonable temperature curve according to the characteristics of different types of electronic components and solder paste. Through real-time monitoring and feedback systems, accurately control the soldering temperature and time to ensure the soldering quality and reduce the occurrence of defects such as solder bridging and short circuits.

[0014] Local nitrogen protection: Introduce local nitrogen protection in the peak area of reflow soldering. Specifically, a nitrogen supply device is set in the peak temperature area of the reflow soldering equipment. Through specially designed gas distribution pipes and nozzles, nitrogen is evenly delivered to the soldering areas of the circuit board and components. In the peak area, when the temperature reaches near the melting point of the solder, the nitrogen supply is turned on, reducing the oxygen content in the soldering area to an extremely low level (for example, the oxygen concentration is less than 1%), effectively inhibiting the oxidation reaction of the solder. Nitrogen is continuously supplied throughout the peak area until the peak stage ends, ensuring that the soldering area is always in a low-oxygen protection atmosphere during the critical processes of solder melting and solidification.

[0015] Quality inspection: Use automated optical inspection equipment (AOI) and X-ray inspection equipment (AXI) to comprehensively inspect the circuit board after chip mounting and soldering. Utilize artificial intelligence algorithms to analyze and identify the inspection images, quickly and accurately detect defects and defective products, and perform marking and classification processing.

[0016] In the preprocessing stage, when the circuit board is subjected to plasma cleaning, the cleaning time is 5 - 7 minutes and the gas flow rate is 100 - 150 ml / min.

[0017] Further, in the solder paste printing step, the printing pressure is 4 - 6 N and the printing speed is 18 - 22 mm / s.

[0018] Further, in the chip mounting operation, when the mounter mounts small and high-precision components, the suction height error is controlled within ±20 μm and the angular deviation is controlled within ±0.3°.

[0019] Further, in the dynamic thermal deformation compensation system, the sampling frequency of the infrared thermal imaging module is 5 times per second, and the sampling frequency of the laser displacement sensor is 10 times per second.

[0020] Further, in the reflow soldering step, the nitrogen flow rate in the peak area is 5 - 7 L / min, the temperature range in the peak area is 230°C - 250°C, and the peak temperature holding time is 30 - 40 s.

[0021] An electronic manufacturing device for performing the SMT chip mounting process, characterized by comprising:

[0022] A plasma cleaning device for preprocessing and cleaning the circuit board;

[0023] A printing device equipped with a laser positioning system for performing solder paste printing;

[0024] Pick-and-place machine, integrated with a vision recognition system and a dynamic thermal deformation compensation system. The dynamic thermal deformation compensation system includes an infrared thermal imaging module, a laser displacement sensor, and a deformation prediction algorithm based on LSTM;

[0025] Reflow soldering equipment, equipped with a segmented temperature control system and a local nitrogen protection device. The local nitrogen protection device includes a nitrogen supply device, a gas distribution pipeline, and a nozzle;

[0026] Automated optical inspection equipment and X-ray inspection equipment, equipped with an artificial intelligence algorithm analysis system for quality inspection of the circuit board after patching and soldering.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] The SMT patching process of the present invention significantly improves the patching accuracy by adopting advanced technologies such as plasma cleaning, laser positioning, vision recognition, machine learning, segmented temperature control, and automated inspection. It can achieve a patching accuracy of sub-micron level, effectively reducing the deviation of the connection between components and the circuit board.

[0029] Introducing a dynamic thermal deformation compensation system (DTCS) effectively solves the problem of reduced accuracy caused by thermal deformation during the patching process, further improving the accuracy and stability of patching.

[0030] Introducing local nitrogen protection in the peak area of reflow soldering greatly reduces the oxidation of solder, improves the soldering quality. The strength and reliability of solder joints are significantly enhanced, reducing the occurrence rate of defects such as solder bridging and brittle solder joints caused by oxidation, and further reducing the defective rate to less than 1% (compared with the case without nitrogen protection, the defective rate can be reduced by about 30% more).

[0031] Adopting a stencil design with a gradient change in the aperture ratio and dynamically adjusting the squeegee pressure through a pressure feedback system optimizes the solder paste printing effect, enabling the solder paste to cover the pads more evenly, reducing soldering defects caused by uneven solder paste printing, and improving the soldering quality and the reliability of component mounting.

[0032] Improves the patching efficiency. Compared with the traditional process, when processing the same quantity and type of components, it can save more than 30% of the time. Enhances the flexibility of the process, can adapt to different types and specifications of electronic components and complex circuit board layouts, meeting the market demand for diversified electronic products. Description of the Drawings

[0033] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the accompanying drawings required in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can also be obtained based on these drawings.

[0034] Figure 1 It is the logic diagram of the present invention. Specific embodiments

[0035] The following will clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only some of the embodiments of the present invention, rather than all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0036] Such as Figure 1 As shown, an SMT chip mounting process includes the following steps:

[0037] Pretreatment: Place the circuit board to be chip-mounted in a plasma cleaning device, set the cleaning parameters, such as the cleaning time is 5 minutes and the gas flow rate is 100 ml / min, and conduct a comprehensive cleaning of the circuit board. At the same time, conduct an appearance inspection and electrical performance test on the electronic components, and reject the unqualified components.

[0038] Solder paste printing: Fix the cleaned circuit board on the printing device, determine the positions of the pads through the laser positioning system, and adjust the height and angle of the printing head. Install a stencil with a gradient change in the aperture ratio. The aperture ratio in the central area of the stencil is 92%, and the aperture ratio in the edge area is 88%. Turn on the pressure feedback system, and initially set the squeegee pressure to 100 N. Select a suitable solder paste formulation according to the type and size of the electronic components. When starting to print, the pressure feedback system monitors the squeegee pressure and the printing situation of the solder paste in real time. When it detects uneven solder paste printing or abnormal pressure, it automatically adjusts the squeegee pressure to vary within the range of 80 - 120 N to ensure that the solder paste can be accurately printed on the pads. Set the printing pressure to 5 N and the printing speed to 20 mm / s for solder paste printing.

[0039] Chip mounting operation: Place the screened electronic components on the feeder of the chip mounter, start the vision recognition system, and identify and position the components. Use machine learning algorithms to automatically adjust the working parameters of the chip mounter, such as the pick-up height and placement angle, according to the characteristic information of the components. For small components such as 0402, use vacuum adsorption and micro-positioning technologies to accurately mount the components on the circuit board.

[0040] Dynamic thermal deformation compensation operation:

[0041] Turn on the infrared thermal imaging module, set the sampling frequency to 5 times per second, perform real-time temperature monitoring on the circuit board and components, and transmit the temperature data to the control system in real time.

[0042] The laser displacement sensor measures the surface morphology of the circuit board and components at a sampling frequency of 10 times per second, obtains real-time displacement data, and transmits it to the control system.

[0043] The deformation prediction algorithm based on LSTM processes the temperature data and displacement data transmitted in real time, combines historical process data and preset model parameters, and predicts the thermal deformation trend. When it is predicted that there is a thermal deformation that may affect the placement accuracy, the algorithm calculates the corresponding position correction amount and sends a correction instruction to the control system of the mounter.

[0044] The control system of the mounter adjusts the motion parameters of the mounter in real time according to the correction instruction, and precisely corrects the placement position of the components.

[0045] Reflow soldering: Send the circuit board after placement into the reflow soldering furnace and set a segmented temperature curve. For example, in the preheating stage, the temperature rises from room temperature to 150 °C at a heating rate of 3 °C / s and the holding time is 60 s; in the holding stage, the temperature is maintained between 150 °C and 180 °C for 120 s; in the reflow stage, the temperature quickly rises to 230 °C and the peak temperature holding time is 30 s; in the cooling stage, the temperature drops from 230 °C to room temperature at a cooling rate of 5 °C / s.

[0046] Local nitrogen protection operation: In the peak temperature area of the reflow soldering equipment (i.e., the area where the temperature reaches about 230 °C), turn on the nitrogen supply device. Set the nitrogen flow rate to 5 L / min, and through the gas distribution pipeline and nozzle, make the nitrogen evenly cover the welding area of the circuit board and components. During the entire peak stage (lasting 30 s), maintain the continuous supply of nitrogen, and monitor the oxygen concentration in the welding area in real time to ensure that it is maintained below 1%. When the peak stage ends, gradually turn off the nitrogen supply.

[0047] Quality inspection: Pass the soldered circuit board through the AOI inspection equipment and AXI inspection equipment in sequence, and use artificial intelligence algorithms to analyze the inspection images. If defects are detected, the system will automatically mark the defect positions and classify the defective products.

[0048] Example 1: SMT placement of a smartphone circuit board

[0049] Circuit board and component situation: The smartphone circuit board has the characteristics of high density and miniaturization, with a variety of component types, including small resistors and capacitors such as 0201 and 0402, as well as chips packaged in BGA (Ball Grid Array).

[0050] Specific process steps:

[0051] Pretreatment: Put the smartphone circuit board into the plasma cleaning equipment, set the cleaning time to 6 minutes and the gas flow rate to 120 ml / min to remove surface impurities. Strictly screen the electronic components, and focus on checking the pin flatness and coplanarity of the BGA chips.

[0052] Solder paste printing: Use a high-precision printing device, install a stencil with a gradient change in the aperture ratio, and for 0201 components, adjust the solder paste formula to a low-viscosity and high-activity type. Ensure the printing accuracy reaches ±5 μm through laser positioning. Initially set the squeegee pressure to 100 N, and the pressure feedback system automatically adjusts the pressure between 80 - 120 N according to the printing situation. Set the printing pressure to 4 N and the printing speed to 18 mm / s.

[0053] Chip placement operation: Start the vision recognition system and use machine learning algorithms to quickly identify components. For 0201 resistors and capacitors, adopt vacuum adsorption and micro-positioning technologies, and control the pick-up height error of the chip mounter within ±10 μm. For BGA chips, accurately align the pins and pads through the vision system, and use the high-precision motion system of the chip mounter for placement, with the angular deviation controlled within ±0.1°.

[0054] Dynamic thermal deformation compensation: During the process of mounting BGA chips and small components, the infrared thermal imaging module monitors that the local temperature of the circuit board rises in real time, with the highest temperature reaching 50°C, and the laser displacement sensor detects that there is a small convex deformation on the surface of the circuit board, with the maximum displacement of 20 μm. The deformation prediction algorithm based on LSTM predicts that as the chip placement process progresses, the deformation will further increase, affecting the chip placement accuracy. The algorithm calculates the position correction amount of the BGA chip as +15 μm in the X-axis direction, -10 μm in the Y-axis direction, and the angle correction amount as +0.05°, and sends it to the chip mounter. The chip mounter adjusts the motion parameters according to the correction instructions to ensure the accurate placement of the BGA chip.

[0055] Reflow soldering: Set the temperature curve according to the characteristics of BGA chips and small components. In the preheating stage, the temperature rises from room temperature to 160°C at a heating rate of 3.5°C / s and remains for 65 s; in the holding stage, the temperature is between 160°C - 185°C for 130 s; in the reflow stage, the temperature rises to 240°C and the peak value is maintained for 35 s; in the cooling stage, it drops to room temperature at a rate of 6°C / s.

[0056] Local nitrogen protection: At the peak temperature zone (around 240°C) of reflow soldering, turn on the nitrogen supply device and set the nitrogen flow rate to 6 L / min. Through the gas distribution pipeline and nozzles, make the nitrogen evenly cover the soldering areas of the circuit board and components. Monitor the oxygen concentration in the soldering area in real time and keep it below 1%. Continuously supply nitrogen throughout the peak stage (35 s).

[0057] Quality inspection: After AOI and AXI inspections, use artificial intelligence algorithms to identify minute defects, such as the offset of 0201 components and the poor soldering of BGA chips. The inspection results show that the defective rate of this batch of smartphone circuit boards is only 0.5%. Compared with the situation without nitrogen protection, the defective rate has decreased by approximately 35%. There is a significant reduction compared to traditional processes, and due to the optimization of the solder paste printing effect, the defects caused by solder paste problems have decreased by approximately 40%.

[0058] Example 2: SMT chip mounting of an automotive electronic control unit (ECU) circuit board

[0059] Circuit board and component situation: Automotive ECU circuit boards have extremely high requirements for reliability and stability. Components include high-power transistors, inductors, etc., as well as some small logic chips and sensor components.

[0060] Specific process steps:

[0061] Pretreatment: Perform plasma cleaning on the automotive ECU circuit board for 7 minutes with a gas flow rate of 150 ml / min to ensure the cleanliness of the circuit board surface. Conduct strict electrical performance tests on components such as high-power transistors.

[0062] Solder paste printing: For the pads of high-power transistors, adjust the solder paste formula to a type with high thermal conductivity and high reliability. Install a stencil with a gradient change in the open area ratio, and use laser positioning to ensure that the printing position accuracy reaches ±8 μm. Initially set the squeegee pressure to 105 N, and the pressure feedback system automatically adjusts the pressure within the range of 80 - 120 N according to the actual printing situation. Set the printing pressure to 6 N and the printing speed to 22 mm / s.

[0063] Chip mounting operation: Through the vision recognition system and machine learning algorithms, accurately identify different types of components. For high-power transistors, use special fixtures for adsorption and placement to ensure their accurate and firm positions. For small logic chips, utilize vacuum adsorption and micro-positioning technologies to achieve fast and precise chip mounting. The parameters of the chip mounter are automatically adjusted according to the component type, and the pick-up height error is controlled within ±15 μm and the angle deviation is controlled within ±0.2°.

[0064] Dynamic Thermal Deformation Compensation: During the chip mounting process, the infrared thermal imaging module detects that due to the preheating of high-power transistors, the local temperature of the circuit board reaches 70°C, and the laser displacement sensor detects a 30-μm deformation in the corresponding area of the circuit board. The deformation prediction algorithm based on LSTM predicts that the deformation will intensify during the subsequent soldering process. The calculated position correction amounts for the small logic chip are -20 μm in the X-axis direction and +15 μm in the Y-axis direction, and the angle correction amount is -0.1°. These are sent to the chip mounter. The chip mounter makes timely adjustments to ensure the accurate mounting of components.

[0065] Reflow Soldering: According to the thermal characteristics of different components, a segmented temperature curve is set. In the preheating stage, the temperature rises from room temperature to 170°C at a heating rate of 4°C / s and remains for 70 s; in the heat preservation stage, the temperature is between 170°C and 190°C for 140 s; in the reflow stage, the temperature rises to 250°C and the peak value is maintained for 40 s; in the cooling stage, it drops to room temperature at a rate of 7°C / s.

[0066] Local Nitrogen Protection: In the peak area (around 250°C) of reflow soldering, the nitrogen supply device is turned on, and the nitrogen flow rate is set to 7 L / min. Through the gas distribution pipeline and nozzle, nitrogen is evenly covered on the soldering areas of the circuit board and components. The oxygen concentration in the soldering area is monitored in real time and kept below 1%. Nitrogen is continuously supplied throughout the peak stage (40 s).

[0067] Quality Inspection: After AOI and AXI inspections, artificial intelligence algorithms are used to analyze complex soldering structures, such as the soldering quality of high-power transistors and the internal connections of multi-layer circuit boards. The inspection results show that the defective rate of this batch of automotive ECU circuit boards is 0.3%. Compared with the situation without nitrogen protection, the defective rate is reduced by about 30%, meeting the requirements of automotive electronics for high reliability, and the soldering defects are reduced by about 35% due to the improvement of solder paste printing.

[0068] Example 3: SMT Chip Mounting of Industrial Control Circuit Boards

[0069] Circuit Board and Component Conditions: Industrial control circuit boards usually contain various interface components, relays, etc. The component sizes and types vary greatly, and higher flexibility in the process is required.

[0070] Specific Process Steps:

[0071] Pretreatment: Place the industrial control circuit board in a plasma cleaning device for 5 minutes with a gas flow rate of 100 ml / min. Conduct a comprehensive inspection of various types of components, including the pin integrity of interface components and the contact performance of relays. For the RJ45 interface, focus on checking whether the pins are bent, deformed, etc.; for relays, ensure the normal opening and closing of their contacts and that the resistance value is within the specified range through electrical tests.

[0072] Solder paste printing: According to the pad sizes and shapes of different components, flexibly adjust the solder paste formula and printing parameters. Install a stencil with a gradient change in the open area ratio. For interface components, use a special printing template to ensure uniform coverage of the solder paste. Initially set the squeegee pressure to 90 N, and the pressure feedback system automatically adjusts the pressure between 80 - 120 N according to the printing situation. Set the printing pressure to 5 N and the printing speed to 20 mm / s. For fine interface components with a pin pitch of 0.5 mm, select a solder paste with low viscosity and high thixotropy to ensure that the solder paste can be accurately printed on the narrow pads without bridging; for relays with larger pad sizes, use a solder paste with slightly higher viscosity to ensure the stability of the solder paste during printing.

[0073] Chip placement operation: Utilize a vision recognition system and machine learning algorithms to quickly identify components of different sizes and shapes. For large relays, use mechanical grasping and precise positioning techniques for placement. Through precise control of the robotic arm, ensure that the pins of the relay are accurately aligned with the pads, with the position deviation controlled within ±0.1 mm; for small components such as 0603 packaged resistors and capacitors, use vacuum adsorption and micro-positioning techniques, with the pick-up height error of the mounter controlled within ±20 μm and the angle deviation controlled within ±0.3°. During the chip placement process, the vision recognition system monitors the position and posture of the components in real-time, and the machine learning algorithms dynamically adjust the working parameters of the mounter based on the monitored data and preset component parameters to ensure accurate placement of each component.

[0074] Dynamic thermal deformation compensation: During the chip placement process, the infrared thermal imaging module monitors that due to the heat generated by multiple components working simultaneously, the overall temperature of the circuit board rises, with an average temperature reaching 45°C, and the laser displacement sensor detects a 25-μm deformation at the edge of the circuit board. The deformation prediction algorithm based on LSTM processes the real-time transmitted temperature data and displacement data, combines historical process data and preset model parameters, and predicts the thermal deformation trend. When it is predicted that the placement position of the interface component may be affected, the algorithm calculates the position correction amount of the interface component as +10 μm in the X-axis direction, +10 μm in the Y-axis direction, and the angle correction amount as +0.15°, and sends it to the mounter. After the mounter adjusts according to the instruction, the accurate placement of the component is completed.

[0075] Reflow soldering: Set the temperature profile according to the comprehensive thermal characteristics of the components. In the preheating stage, the temperature rises from room temperature to 155°C at a heating rate of 3.2°C / s and is maintained for 60 s; in the holding stage, the temperature is between 155°C - 180°C for 120 s; in the reflow stage, the temperature rises to 235°C and the peak is maintained for 30 s; in the cooling stage, it drops to room temperature at a rate of 5°C / s. For different types of components, during the reflow soldering process, through a real-time monitoring system, fine-tune the temperature in different areas to ensure that each component can be soldered under suitable temperature conditions.

[0076] Local nitrogen protection: At the peak zone (around 235°C) of reflow soldering, turn on the nitrogen supply device and set the nitrogen flow rate to 5.5 L / min. Through the gas distribution pipeline and nozzle, make the nitrogen evenly cover the soldering areas of the circuit board and components. Real-time monitor the oxygen concentration in the soldering area and keep it below 1%. Continuously supply nitrogen throughout the peak stage (30 s). Quality inspection: Through AOI and AXI inspections, use artificial intelligence algorithms to analyze the soldering and chip mounting quality of different types of components. For interface components, focus on detecting whether the pins are firmly soldered and if there are any dry joints; for relays, check the fullness of the solder joints and the reliability of the electrical connections. The inspection results show that the defective rate of this batch of industrial control circuit boards is 0.9%, reflecting the good performance of this process when dealing with complex circuit boards and diverse components. Due to the adoption of the process of the present invention, the defects caused by uneven solder paste printing and thermal deformation are reduced by about 30%, effectively improving the quality and reliability of the products.

Claims

1. An SMT chip mounting process, characterized in that, It includes the following steps: Pretreatment stage: The circuit board is subjected to plasma cleaning to remove impurities such as surface oil stains and oxides, and the electronic components are inspected and screened; Solder paste printing: Using printing equipment, laser positioning technology is adopted to control the position and thickness of solder paste printing, and the solder paste formula and printing parameters are optimized according to the type and size of electronic components; Chip mounting operation: A vision recognition system and a chip mounter are adopted. Using machine learning algorithms, the working parameters of the chip mounter are automatically adjusted according to the shape, size and position information of the components. Vacuum adsorption and micro-positioning technology are used for small and high-precision components; Reflow soldering: Segmented temperature control technology is adopted. A reasonable temperature curve is set according to the characteristics of different types of electronic components and solder paste. Local nitrogen protection is introduced in the peak area of reflow soldering. Nitrogen is evenly transported to the welding areas of the circuit board and components through a nitrogen supply device, a gas distribution pipeline and a nozzle; Quality inspection: Automated optical inspection equipment and X-ray inspection equipment are adopted. Using artificial intelligence algorithms, the circuit board after chip mounting and soldering is comprehensively inspected, and defects and defective products are marked and classified; 2. The SMT chip mounting process according to claim 1, wherein, In the solder paste printing stage, a stencil design with a gradient change in the opening ratio is adopted. The opening ratio in the central area of the stencil is 92%, and the opening ratio in the edge area is 88%. The pressure feedback system is combined to dynamically adjust the squeegee pressure, and the squeegee pressure can be adjusted within the range of 80-120N according to the actual printing situation.

3. A SMT chip mounting process according to claim 1, characterized in that, In the chip mounting stage, a dynamic thermal deformation compensation system is introduced to correct the component position in real time. The dynamic thermal deformation compensation system includes an infrared thermal imaging module, a laser displacement sensor and a deformation prediction algorithm based on LSTM. The infrared thermal imaging module monitors the temperature distribution of the circuit board and components in real time. The laser displacement sensor measures the surface morphology of the circuit board and components in real time. The deformation prediction algorithm based on LSTM comprehensively analyzes and processes the data obtained by the infrared thermal imaging module and the laser displacement sensor, predicts the thermal deformation trend and adjusts the motion parameters of the chip mounter in real time.

4. The SMT chip mounting process according to claim 1, wherein, In the pretreatment stage, when the circuit board is subjected to plasma cleaning, the cleaning time is 5-7 minutes, and the gas flow rate is 100-150 ml / min.

5. The SMT chip mounting process according to claim 1, characterized in that, In the solder paste printing step, the printing pressure is 4-6N, and the printing speed is 18-22 mm / s.

6. The SMT chip mounting process according to claim 1, wherein In the chip mounting operation, when the chip mounter mounts small and high-precision components, the suction height error is controlled within ±20μm, and the angle deviation is controlled within ±0.3°.

7. The SMT chip mounting process according to claim 1, wherein In the dynamic thermal deformation compensation system, the sampling frequency of the infrared thermal imaging module is 5 times per second, and the sampling frequency of the laser displacement sensor is 10 times per second.

8. The SMT chip mounting process according to claim 1, wherein, In the reflow soldering step, the nitrogen flow rate in the peak area is 5-7 L / min, the temperature range in the peak area is 230°C-250°C, and the peak temperature holding time is 30-40 s.

9. An electronic manufacturing device for performing the SMT chip mounting process according to any one of claims 1-8, characterized in that, It includes: A plasma cleaning device for preprocessing and cleaning the circuit board; Printing equipment equipped with a laser positioning system for solder paste printing; A chip mounter integrated with a vision recognition system and a dynamic thermal deformation compensation system, the dynamic thermal deformation compensation system including an infrared thermal imaging module, a laser displacement sensor and a deformation prediction algorithm based on LSTM; A reflow soldering device provided with a segmented temperature control system and a local nitrogen protection device, the local nitrogen protection device including a nitrogen supply device, a gas distribution pipeline and a nozzle; Automated optical inspection equipment and X-ray inspection equipment equipped with an artificial intelligence algorithm analysis system for quality inspection of the circuit board after chip mounting and soldering.

Images