A chip soldering method and its soldering device

Abstract

The present application provides a chip soldering method and a soldering device thereof. The device includes: a 3D printing device that precisely prints solder onto the connection part between the chip and the substrate according to a preset path; a soldering device that solders the chip and the substrate; an ultrasonic detection module that detects the quality of the solder joints; a signal receiving and processing unit connected to the ultrasonic detection module, which analyzes the signals fed back by the ultrasonic detection module to judge the quality of the solder joints; a control system that adjusts the soldering parameters and printing parameters in real time according to the ultrasonic detection results and can timely repair serious defects. The present application monitors the solder joints in real time, adjusts the printing parameters and soldering parameters in real time according to the defects of the solder joints, or controls the printing nozzle of the 3D printing device and the soldering machine to perform secondary printing repair on the solder joints at the defective positions after adjusting the parameters, so as to avoid welding problems in the whole batch due to problems such as soldering parameters, resulting in low work efficiency.

Description

Technical Field

[0001] This application relates to the field of chip soldering technology, and particularly to a chip soldering method and its soldering device. Background Art

[0002] Chip soldering is a key process in modern electronic manufacturing, which connects the chip with carriers such as circuit boards to achieve electrical and mechanical connections. The existing soldering processes are mainly divided into the following categories:

[0003] I. Surface Mount Technology (SMT): The process flow of surface mount technology is as follows: solder paste is printed onto the pads of the circuit board through a stencil. The thickness and positional accuracy of the solder paste have a significant impact on the soldering quality. The pick-and-place machine uses a vacuum nozzle to accurately place the chip on the pad coated with solder paste, and then the circuit board is sent into the reflow oven. After passing through the preheating, heating-up, reflow, and cooling stages, the solder paste melts and then solidifies to complete the soldering of the chip and the circuit board. It is widely used in various electronic products, such as mobile phones, computer motherboards, etc., and is suitable for chip packages with small pin pitches and small sizes, enabling high-density assembly.

[0004] II. Through-Hole Technology (THT): The process flow of through-hole technology is as follows: first, the pins of the chip are inserted into the corresponding through-holes of the circuit board, and then fixed by wave soldering or manual soldering. During wave soldering, the circuit board passes through the molten solder wave on the conveyor belt, and the pins come into contact with the solder to complete the soldering. Manual soldering uses a soldering iron to solder each pin one by one. It is commonly used for chips with higher mechanical strength requirements and thicker pins, such as some power chips, sockets, etc., and is still used in traditional electronic devices and some special electronic modules.

[0005] III. Flip Chip Technology (FC): The process flow of flip chip technology is as follows: the active surface of the chip faces down and is directly connected to the circuit board through solder balls. First, metal bumps (such as copper pillars, tin-lead or lead-free solder balls, etc.) are made on the pads of the chip, and then the chip is flipped and aligned with the corresponding pads on the circuit board. The connection is achieved by heating to melt the solder balls. Sometimes, underfill is also filled between the chip and the circuit board to enhance the connection reliability. It is widely used in high-performance processors, FPGAs and other chips, which can provide a shorter electrical connection path, reduce signal transmission delay, improve chip performance, and at the same time achieve a higher packaging density.

[0006] After the chip welding is completed, quality monitoring is carried out. The detection methods usually include appearance detection, electrical detection, X-ray detection, etc. Among them, for appearance detection, the appearance of the solder joints is observed with the naked eye, magnifying glass or microscope to check for defects such as cold solder joints, short circuits, insufficient solder, solder balls, etc.; for electrical detection, equipment such as multimeters and oscilloscopes are used to detect the electrical connection performance between the chip and the circuit board after welding. By measuring parameters such as resistance, voltage, and current between the pins, it is judged whether there are electrical faults such as open circuits and short circuits to ensure that the chip can work normally; for X-ray detection, X-rays are used to penetrate the circuit board and the chip. According to the different absorption degrees of different materials for X-rays, an image is formed on the imaging plate or detector, and the internal structure of the solder joints can be observed to detect internal defects such as voids and cold solder joints.

[0007] As can be seen from the above, in the prior art, the detection of chips is usually carried out after welding, and the welding parameters during the welding process are all the same. If the selection is inappropriate, it may cause problems in the welding of the entire batch of chips. This application aims to monitor the welding quality in real time during the welding process, realize timely response and repair of welding defects, ensure the welding quality, and avoid problems in the welding of the entire batch due to problems such as welding parameters, resulting in low work efficiency.

[0008] After detailed retrieval by the applicant, no relevant technical solutions have been found, and a new technical solution needs to be provided to solve the above technical problems. Summary of the Invention

[0009] This application provides a chip welding method, which includes the following steps:

[0010] S1: Pretreat the chip and the substrate;

[0011] S2: Set the printing parameters of the 3D printing device and the welding parameters of the welder. The printing parameters include the moving speed of the printing nozzle, the solder extrusion amount, and the printing nozzle temperature; the welding parameters include the welding temperature, welding time, welding power, welding pressure, and welding frequency;

[0012] S3: Calibrate the ultrasonic detection module;

[0013] S4: The printing nozzle of the 3D printing device prints solder, and the chip is welded by the welder;

[0014] S5: During the welding process, the ultrasonic detection module detects the solder joints in real time to judge whether there are defects in the solder joints. Otherwise, continue welding. If yes, enter S6;

[0015] S6: The control system controls the printing nozzle to pause printing the solder, re - sets the printing parameters of the 3D printing device and / or the welding parameters of the welding machine, or after re - setting the printing parameters of the 3D printing device and / or the welding parameters of the welding machine, the control system controls the printing nozzle and the welding machine to perform printing repair on the solder joints at the defective positions.

[0016] S7: During the printing repair process, the ultrasonic detection module detects the solder joints in real - time to determine whether there are defects in the solder joints. Otherwise, continue welding. If yes, enter S6.

[0017] As a preferred solution, it further includes S8: For the chips with welding completed, use the ultrasonic detection module to comprehensively detect the quality of the solder joints.

[0018] As a preferred solution, in S5, the ultrasonic detection module completes the detection and feedback of whether there are defects in the solder joints before the solder joints solidify.

[0019] As a preferred solution, in S5, during the welding process, the ultrasonic detection module's real - time detection of the solder joints includes the following steps:

[0020] S51: In the system of the 3D printing device, add an information module that can real - time feedback the position of the printing nozzle, the printing speed, and the estimated forming time of the solder joints.

[0021] S52: Build a communication link between the 3D printing device and the ultrasonic transducer of the ultrasonic detection module to ensure that data between the two can be transmitted in real - time.

[0022] S53: In the 3D printing device and the ultrasonic transducer, set a unified time reference.

[0023] S54: According to the speed and path planning of the 3D printing device, predict the forming time of each solder joint in advance.

[0024] S55: Before the solder joint is expected to be formed, trigger the ultrasonic transducer in advance for pre - heating and preparation work.

[0025] S56: The ultrasonic transducer emits ultrasonic waves to the solder joint before the solder joint solidifies and sends a signal to the signal receiving and processing unit before solidification.

[0026] As a preferred solution, it further includes S57: According to the fluctuation of the actual speed of the 3D printing device, dynamically adjust the detection time point of the ultrasonic transducer in real - time.

[0027] As a preferred solution, in S5, the solder joint defects include void defects, crack defects, inclusion defects, and non - fusion defects.

[0028] As a preferred solution, in S6, when the printing nozzle pauses printing the solder and re - sets the printing parameters of the 3D printing device and / or the welding parameters of the welding, it includes that when the solder joint defect is a void defect, at least one parameter among the solder extrusion amount, the moving speed of the printing nozzle, the welding temperature, the welding time, the welding power, the welding pressure, and the welding frequency is adjusted; when the solder joint defect is a crack defect, at least one parameter among the printing nozzle temperature, the moving speed of the printing nozzle, the welding temperature, the welding time, the welding power, the welding pressure, and the welding frequency is adjusted; when the solder joint defect is an inclusion defect, at least one parameter among the moving speed of the printing nozzle, the welding temperature, the welding time, the welding pressure, and the welding frequency is adjusted; when the defect is a lack - of - fusion defect, at least one parameter among the moving speed of the printing nozzle, the welding temperature, the welding time, the welding pressure, the welding power, and the welding frequency is adjusted.

[0029] As a preferred solution, when the solder joint defect is a crack defect, the moving speed of the printing nozzle is adjusted according to the length and direction of the crack, and the temperature of the printing nozzle is adjusted according to the crack depth.

[0030] As a preferred solution, when the solder joint defect is a void defect, the calculation formula for the solder extrusion amount is: , where M represents the adjusted solder extrusion amount; represents the solder extrusion amount set in S2; represents the increased solder amount, = represents the density of the solder, represents the spreading and loss coefficient of the solder when filling the void, the value range of S is 1.2 - 1.5, V represents the volume of the void, , and r is the radius of the void.

[0031] As a preferred solution, when the solder joint defect is a void defect, the calculation formula for the solder extrusion amount is: , where M represents the adjusted solder extrusion amount; represents the solder extrusion amount set in S2; d represents the distance from the void position to the center of the solder joint, , the mid - line coordinates of the solder joint are ( , , ), the coordinates of the void position are (X, Y, Z); j represents the solder extrusion amount coefficient, and d and j are linearly related. When d increases by 1mm, j increases by 0.05.

[0032] As a preferred solution, when the solder joint defect is a crack defect, the calculation formula for the moving speed of the printing nozzle is: ; where, represents the adjusted moving speed of the printing nozzle; Represents the moving speed of the printing nozzle set in S2; Represents the crack length; D represents the amount of speed change corresponding to a unit crack length. For every 1 mm of crack length, the change in D is ; Represents the angle correction coefficient, , is the angle between the crack direction and the moving direction of the printing nozzle.

[0033] As a preferred solution, when the solder joint defect is a crack defect, the calculation formula for the temperature of the printing nozzle is: ; where Represents the adjusted temperature of the printing nozzle; Represents the temperature of the printing nozzle set in S2; h represents the crack depth; Represents the amount of temperature change corresponding to a unit crack depth. For every 1 μm of crack depth, the change in is 1.5.

[0034] A chip welding device, comprising:

[0035] 3D printing device: Precisely print solder along a preset path to the connection part between the chip and the substrate;

[0036] Welding device: Weld the chip and the substrate;

[0037] Ultrasonic detection module: Detect the quality of the solder joint;

[0038] Signal receiving and processing unit: Connected to the ultrasonic detection module. The signal receiving and processing unit analyzes the signal fed back by the ultrasonic detection module to judge the quality of the solder joint;

[0039] Control system: Re-set the printing parameters of the 3D printing device and / or the welding parameters of the welder according to the ultrasonic detection results, or after re-setting the printing parameters of the 3D printing device and / or the welding parameters of the welder, the control system controls the printing nozzle and the welder to print and repair the solder joints at the defective positions.

[0040] As a preferred solution, the 3D printing device includes a 3D printing nozzle, a solder delivery system, and a motion control platform:

[0041] Solder delivery system: Connected to the 3D printing nozzle, used to provide solder to the 3D printing nozzle;

[0042] 3D printing nozzle: Used to precisely print the solder delivered by the solder delivery system to the connection part between the chip and the substrate;

[0043] Motion control platform: Connected to the 3D printing nozzle, used to control the movement of the 3D printing nozzle.

[0044] As a preferred solution, the ultrasonic detection module includes an ultrasonic generator and an ultrasonic transducer:

[0045] Ultrasonic generator: generates high-frequency electrical signals;

[0046] Ultrasonic transducer: connected to the ultrasonic generator, converts the high-frequency electrical signal of the ultrasonic generator into ultrasonic waves, transmits them to the solder joints to be detected, receives the ultrasonic signals reflected and scattered by the solder joints, converts them into electrical signals, and transmits the electrical signals to the signal receiving and processing unit.

[0047] In this application, the photovoltaic panel is welded through the cooperation of a 3D printing device and an ultrasonic detection device, and has the following advantages:

[0048] (1) Utilize ultrasonic waves to monitor the internal quality of solder joints in real time, without contacting the solder joints, and can ensure the accuracy of defect detection;

[0049] (2) Adopt the precise control advantages of the 3D printing device for the moving speed of the printing nozzle, the solder extrusion amount, and the temperature of the printing nozzle to achieve timely response and repair of welding defects and ensure welding quality;

[0050] (3) Adjust the printing parameters of the 3D printing device and the welding parameters of the welding machine in real time according to the defects, or control the printing nozzle of the 3D printing device and the welding machine to perform secondary printing repair on the solder joints at the defective positions after adjusting the parameters; avoid welding problems in the entire batch due to problems with welding parameters, etc., resulting in low work efficiency. Specific embodiments

[0051] The following details the specific embodiments of the present invention. It should be noted that the specific embodiments described herein are only used to illustrate and explain the present invention and are not used to limit the present invention. Embodiment 1

[0052] This embodiment provides a chip welding method, including the following steps:

[0053] S1: Pretreat the chip and the substrate;

[0054] The pre-treatment of the chip mainly includes: carefully checking whether there are damaged or loose parts on the chip, and repairing or replacing them first if necessary; gently placing the inspected chip into the cleaning basket to avoid direct contact between the chip and the bottom of the cleaning tank during the cleaning process, reducing potential damage, selecting a suitable cleaning solution according to the type and degree of contamination of the chip, and controlling the concentration and pH value of the cleaning solution according to specific circumstances; setting appropriate cleaning time and temperature, and starting ultrasonic cleaning. Usually, the temperature of the cleaning solution should be controlled between 40°C and 60°C. Under the action of ultrasonic waves, the solvent molecules in the cleaning solution can more effectively penetrate into the tiny gaps on the chip surface to remove dirt, grease, etc. For some difficult-to-remove stains, high-pressure spraying can be used to assist cleaning, but it should be noted to avoid direct impact on the chip to prevent damage. Airflow can also be used to blow away insoluble pollutants such as dust and fibers on the chip surface; for the chip after the above cleaning, thoroughly rinse the chip with pure water to ensure the removal of cleaning agent residues; place the chip in a dry environment or use a drying device to dry it to ensure the surface of the chip is dry.

[0055] The pre-treatment of the substrate mainly includes: rust removal, degreasing, grinding, etc. on the substrate surface to remove impurities such as rust, oil stain, and scale on the surface, making the substrate surface clean and smooth to improve the bonding strength with the chip. Sandblasting, pickling, etc. can be used for surface cleaning; checking whether the size of the substrate meets the requirements, and performing cutting, straightening, etc. on the substrate that does not meet the requirements to ensure the dimensional accuracy of the substrate; appropriately roughening the substrate surface by methods such as brushing and micro-etching. The purpose is to increase the roughness of the substrate surface for better bonding with the chip. Usually, a cleaning solution and a micro-etching solution are used for treatment; cleaning the substrate by methods such as using solvents, ultrasonic cleaning, or distilled water to remove dust, oil stain, and other impurities on the surface to ensure the substrate surface is clean and create good conditions for subsequent processing steps; drying the cleaned substrate, which can be done by natural air drying, drying with a drying device, etc., to ensure the substrate surface is dry; judging whether chemical treatment of the substrate is needed according to specific requirements. For those that need it, chemical treatment such as pickling, alkali washing, etching, and oxidation can be carried out on the substrate to further improve the surface performance of the substrate, remove residual impurities, increase surface roughness, or provide special chemical activity.

[0056] S2: Set the printing parameters of the 3D printing device and the welding parameters of the welding machine. The welding parameters of the welding machine include welding temperature, welding time, welding power, welding pressure, and welding frequency. The setting of the welding temperature mainly depends on the melting point of the solder. Usually, the welding temperature needs to be set within the range of 40°C - 70°C above the melting point of the solder to ensure that the solder can be fully melted and achieve good welding results. At the same time, considering the thermal sensitivity of the chip and the solder joints, the temperature should not be too high to avoid damaging the chip. The setting of the welding time needs to ensure that the solder has enough time to melt, flow, and fully combine with the welded parts. However, too long a time will lead to heat accumulation, which may damage the chip or the structure around the solder joints. It needs to be determined in combination with the solder joint size, welding temperature, and welding process requirements. For example, for small chip solder joints, the welding time can be initially set at 0.3 - 0.5 seconds. The setting of the welding power is closely related to the welding temperature and welding time. It determines the energy transferred to the solder joint per unit time. The power size needs to be determined according to the characteristics of the welding equipment, the heat capacity of the solder joint, and the required welding speed. For example, for a common small welding equipment used for chip solder joint welding, the power can be initially set at 50W - 100W. If it is found that the welding temperature rises too slowly or the welding effect is not good subsequently, the power can be adjusted according to the actual situation. The welding pressure is mainly used to ensure close contact between the welded parts and the solder, and to promote metallurgical bonding during the welding process. The pressure size needs to consider the size and shape of the solder joint and the load-bearing capacity of the chip. Excessive pressure may damage the chip or the solder joint. For example, in chip solder joint welding, the welding pressure can be initially set at 0.2 - 0.5N. For the welding frequency, when the chip solder joint material is thicker, or strict requirements for heat input are needed, and overheating damage to the chip peripheral structure needs to be avoided, low-frequency welding can be used. For example, for solder joints with a thickness exceeding 1mm, to prevent chip damage caused by excessive heat accumulation, a lower frequency can be selected, generally between 10Hz - 50Hz. At low frequencies, the laser pulse interval time is longer, and the heat input is relatively dispersed, which is beneficial to controlling the temperature of the welding area. For example, when welding large-sized and heat-sensitive chip solder joints, a frequency of 15Hz can ensure the welding quality of the solder joints and reduce the thermal impact on the chip. For thinner solder joint materials, or when rapid welding is required to improve production efficiency, high-frequency welding is more suitable. For example, for solder joints with a thickness below 0.3mm, high-frequency welding can quickly achieve connection and ensure the continuity of the weld seam. Usually, it is between 100Hz - 500Hz. At high frequencies, the laser pulses are dense, which can quickly melt the solder and achieve efficient welding. For example, in large-scale chip production, for tiny and thin solder joints, using a frequency of 300Hz can significantly improve the welding speed and meet the production requirements.

[0057] The printing parameters include: the moving speed of the printing nozzle, the solder extrusion amount, and the printing nozzle temperature. When setting the printing parameters of the 3D printing device for chip welding, factors such as chip type, substrate material, and solder characteristics need to be comprehensively considered. Specifically as follows:

[0058] S21: Determine the range of basic parameters: Different solders have different characteristics such as melting points and viscosities, which are the basis for setting parameters. For example, for the commonly used tin-silver-copper (SAC) alloy solder with a melting point of approximately 217°C - 220°C, the lower limit of the printing nozzle temperature is determined to be slightly higher than the melting point; due to differences in the performance of different 3D printing devices, refer to the parameter range provided in the device manual for specific details.

[0059] S22: Set the printing nozzle temperature: Based on the melting point of the solder, the nozzle temperature should ensure that the solder is fully melted and has good fluidity. For example, for the tin-silver-copper (SAC) alloy solder, the initial setting temperature of the printing nozzle temperature can be set to 250°C - 280°C, which is 30°C - 60°C higher than the highest melting point to ensure solder melting; preferably, a small amount of solder can be printed for testing to observe the melting state. For example, if the solder extrusion is difficult and wire drawing occurs, it indicates that the temperature is low and the temperature needs to be gradually increased (5°C - 10°C each time); if the solder flows too fast and the forming is poor, it indicates that the temperature is high and the temperature should be appropriately decreased, and the temperature needs to be gradually decreased (5°C - 10°C each time). Example: When testing at 250°C for the first time, the solder extrusion was not smooth. After increasing the temperature to 260°C, the state was good, and 260°C was determined as the initial setting temperature of the printing nozzle temperature.

[0060] S23: Set the solder extrusion amount: Estimate the amount of solder required for each solder joint (solder extrusion amount) according to the size and shape of the solder joints needed. For example, when welding chip pins, the diameter of the solder joint for small pins is 0.5 mm. Assuming the solder joint is hemispherical, according to the sphere volume formula: , the calculated solder joint volume is approximately 0.033 mm 3 , considering that slightly more solder is required for actual welding, the initial setting of the solder extrusion amount per time is 0.05 mm 3 ; preferably, a series of solder joints can be printed to observe the solder coverage and filling situation. If the solder joints are too small and not filled, increase the extrusion amount; if there is too much solder and overflow occurs, reduce the extrusion amount. For example, after the first printing, it was found that the solder joint did not completely cover the connection part between the pin and the substrate. After appropriately increasing the extrusion amount and testing again, until the solder joint is full and the forming is good.

[0061] S24: Set the moving speed of the printing nozzle: Combine the solder extrusion amount and the printing nozzle temperature to set the initial moving speed of the printing nozzle. Taking the tin-silver-copper (SAC) alloy solder and a microchip as an example, if the extrusion amount is small (less than 0.01 mm 3 ), and the temperature is appropriate, the moving speed of the printing nozzle can be slightly faster; if the extrusion amount is large (greater than 0.05 mm 3), when the temperature is appropriate, the moving speed of the printing nozzle should be slowed down to ensure uniform distribution of the solder; for the standard of appropriate temperature, it is set according to specific circumstances. Taking the common tin-silver-copper (SAC) alloy solder as an example, the appropriate temperature is between 250°C and 280°C. However, due to different component ratios, the melting points of tin-silver-copper (SAC) alloy solders vary, and corresponding adjustments are required. For example, the tin-silver-copper (SAC) alloy solder with a higher silver content has a slightly higher melting point, and the appropriate temperature is between 260°C and 290°C. For other types of solders, such as tin-lead solder, with a lower melting point, the appropriate temperature range is around 183°C - 230°C, and technicians set it accurately according to the solder characteristics.

[0062] When the temperature meets the solder characteristics, the calculation formula for the moving speed of the printing nozzle is: ,

[0063] Among them, represents the moving speed of the printing nozzle, is the initial solder extrusion amount set above, is the cross-sectional area of the solder joint, is an empirical coefficient, with a value between 0.5 and 2. The empirical coefficient is affected by the viscosity of the solder and the temperature of the printing nozzle (the viscosity of the solder affects fluidity, and high-viscosity solder requires a slow speed, so the Y value decreases accordingly; the temperature of the printing nozzle affects the state of the solder, and when the temperature is high, the fluidity is good, and the Y value can be appropriately increased); for example, when welding micro solder joints, takes a value of 1, solder joint A = 0.2mm 2 , = 0.05mm 3 , and the calculated is 0.25mm / s. During the printing test, it is found that the solder accumulates, indicating that the speed is slow. Increase the Y value to 1.5 and recalculate to get 0.375mm / s, and observe the forming effect again; the above calculation method is to emit ultrasonic waves to a standard solder joint, and calculate the geometric parameters of the solder joint according to the reflection echo time and signal intensity of the ultrasonic waves at different interfaces of the solder joint. By measuring the propagation speed and reflection echo time delay of the ultrasonic waves in the solder joint, combined with the shape model of the solder joint, parameters such as the thickness of the solder joint can be deduced, and then combined with other measurement methods (such as using an industrial camera to measure the planar size of the solder joint), the cross-sectional area A can be indirectly calculated; for example, if the size of the solder joint in the horizontal direction is known and the thickness of the solder joint is obtained through ultrasonic measurement, the two are multiplied to obtain the cross-sectional area. This method does not require direct contact with the solder joint.

[0064] Preferably, after the above parameters are initially set, an overall test of chip soldering is carried out to observe the quality of multiple solder joints and the firmness of the connection between the chip and the substrate. According to the overall test results, the parameters can be fine-tuned. For example, if it is found that some solder joints are still poorly soldered, the extrusion amount can be appropriately increased, the soldering time can be increased, or the moving speed of the nozzle can be decreased, etc.; if there are signs of overheating after chip soldering, the temperature of the printing nozzle can be fine-tuned downwards, the soldering temperature can be decreased, etc.; after multiple tests and fine-tuning, a set of optimal parameters suitable for specific chip soldering can be determined.

[0065] S3: Calibrate the ultrasonic detection module; it can ensure the accuracy, stability, and reliability of the ultrasonic detection module and the soldering process during subsequent chip soldering; the ultrasonic detection module in this embodiment includes an ultrasonic generator, an ultrasonic transducer, and a signal receiving and processing unit.

[0066] Calibrate the ultrasonic generator, including frequency calibration, amplitude calibration, power calibration, and pulse parameter calibration. Specifically: Frequency calibration: Connect a frequency meter to the output end of the ultrasonic generator to measure its actual output frequency, compare the measured value with the set frequency of the ultrasonic generator, and if there is a deviation, adjust it through the frequency adjustment knob or software settings of the ultrasonic generator to make its output frequency reach the set value; Amplitude calibration: Connect the output end of the ultrasonic generator to the input end of the oscilloscope through a suitable probe, ensure that the attenuation coefficient of the probe is set correctly to accurately measure the signal amplitude; Set a known frequency and an initial value of the expected output amplitude on the ultrasonic generator, for example, set the frequency to 20 kHz and the amplitude to 10 Vpp (peak-to-peak value), observe the waveform displayed on the oscilloscope, read the actually measured signal amplitude, if the actual amplitude does not match the set value, it means adjustment is needed. For example, if the measured value is 8 Vpp, it means adjustment is needed. Find the amplitude adjustment knob on the ultrasonic generator or through the amplitude setting option in the software interface, gradually adjust the amplitude, and at the same time observe the change of the waveform amplitude on the oscilloscope until the amplitude displayed on the oscilloscope reaches the expected 10 Vpp; Power calibration: Connect a power meter to the output end of the ultrasonic generator to measure its output power, and according to the specifications of the device, adjust the power adjustment knob or relevant parameters of the ultrasonic generator to make the output power reach the specified range or set value; Pulse parameter calibration: For an ultrasonic generator with a pulse output function, parameters such as pulse width and pulse repetition frequency need to be calibrated; Use an oscilloscope to observe the pulse signal output by the generator, compare it with the set parameters, and if there is a deviation, adjust it through the corresponding settings.

[0067] Calibrate the ultrasonic transducer, including sensitivity calibration, frequency response calibration, and directivity calibration. Specifically:

[0068] Sensitivity calibration: Place the ultrasonic transducer in a standard environment with a known sound pressure field, such as in a calibration water tank or on a standard test block. Use a standard hydrophone or other receiving device with known sensitivity to receive the ultrasonic signal emitted by the transducer, measure the sound pressure magnitude, and calculate the sensitivity of the transducer based on the measurement results and the known sound pressure field intensity. If there is a deviation between the sensitivity and the nominal value, calibration can be performed by adjusting the installation position and angle of the transducer or by making necessary parameter compensations. Frequency response calibration: Use a signal generator to generate electrical signals of different frequencies and input them into the ultrasonic transducer to make it emit ultrasonic waves. At the same time, use a receiving device to measure the output response of the ultrasonic transducer at different frequencies, such as the sound pressure amplitude or the intensity of the received signal, plot the frequency response curve, and observe the response of the transducer at different frequencies. If there are abnormalities in the frequency response or it does not meet the specification requirements, calibration can be performed by adjusting parameters such as the matching circuit and resonant frequency of the transducer. Directivity calibration: Fix the ultrasonic transducer on a rotating bracket so that it can emit ultrasonic waves at different angles. Place a receiving device at a certain distance and measure the emitted sound pressure or the intensity of the received signal of the ultrasonic transducer at different angles, plot the directivity pattern, and check whether the directivity of the ultrasonic transducer meets the design requirements. If there is a deviation in the directivity, calibration can be performed by adjusting the structure, reflector, or damping material of the transducer, etc.

[0069] Calibration of the signal receiving and processing unit includes gain calibration, filter calibration, and time delay calibration. Specifically:

[0070] Gain calibration: Input a standard signal with a known amplitude into the signal receiving and processing unit, adjust the gain knob or parameters of the unit to make the amplitude of the output signal reach the expected value. Calculate the gain value by comparing the amplitudes of the input and output signals and compare it with the set gain. If there is a deviation, make adjustments until the gain is accurate. Filter calibration: Input signals of different frequencies into the unit and check whether parameters such as the cut-off frequency and bandwidth of the filter are accurate by observing the spectrum or filtering effect of the output signal. If the filtering effect is not ideal or the parameters do not match the design values, calibration can be performed by adjusting the circuit parameters or software settings of the filter. Time delay calibration: For units involving time measurement or signal processing, the time delay parameters need to be calibrated. Input a standard time signal or a signal with a known delay into the unit and measure the time delay of the output signal. Compare it with the set delay value. If there is a deviation, calibration can be performed by adjusting the relevant time parameters or circuit delay elements.

[0071] S4: The printing nozzle of the 3D printing device prints solder, and chip soldering is performed by a soldering machine. The soldering machine uses a soldering machine that does not require solder conveyance in existing technologies such as laser soldering. In this embodiment, laser soldering is taken as an example;

[0072] S5: During the welding process, the ultrasonic detection module detects the solder joints in real time to determine whether there are defects in the solder joints. If there are no defects, the welding continues; if there are defects, it enters S6;

[0073] The methods for determining whether there are defects in the solder joints mainly include the following:

[0074] 1. Based on signal amplitude analysis: Setting the normal amplitude range: Before the formal welding, ultrasonic detection is carried out on solder joints of the same type, same specification and determined to be defect-free to obtain a series of ultrasonic reflection signal amplitude data. By statistically analyzing these data, the fluctuation range of the signal amplitude of normal solder joints is determined; for example, after multiple detections of solder joints of a certain model, it is found that the normal signal amplitude fluctuates between 80 - 120 mV; the methods for determining the defect-free solder joints mentioned above include but are not limited to: electrical performance testing, X-ray detection, metallographic analysis, etc. The above are conventional solder joint detection methods, and this application will not elaborate specifically here; for example, X-ray detection is to use an X-ray detection device to perform perspective imaging on the solder joints. X-rays can penetrate the solder joints and the circuit board, showing the internal structure and shape of the solder joints. By observing the X-ray image, internal voids, inclusions, and the connection between the pins and the pads can be found; Real-time detection and comparison: During the welding process, the solder joints are detected in real time. If the amplitude of the ultrasonic reflection signal is significantly lower than the lower limit of the normal range, it may indicate that there are defects such as voids in the solder joints, because these defects will cause the energy attenuation during the propagation of ultrasonic waves to increase, resulting in a weaker reflection signal; on the contrary, if the amplitude is higher than the upper limit of the normal range, it may mean that the internal structure density of the solder joint is abnormal, such as the existence of inclusions and other defects, which affect the reflection characteristics of ultrasonic waves; for example, if the signal amplitude of a certain solder joint is detected to be 50 mV, which is much lower than the normal range of 80 - 120 mV, it can be preliminarily determined that this solder joint may have a void defect.

[0075] 2. Based on signal reflection time analysis: Calculating the normal propagation time: According to the material properties of the solder joint (the propagation speed of ultrasonic waves in this material is known) and the geometric dimensions of the solder joint, calculate the theoretical time for ultrasonic waves to propagate to different positions in the normal solder joint and reflect back; for example, given that the thickness d of the solder joint is 5 mm, and the propagation speed v of ultrasonic waves in this welding material is 5000 m / s, then the theoretical time for ultrasonic waves to be emitted and reflected back from the bottom of the solder joint is ,d = 5 mm = 5 10 -3 m, v = 5000 m / s, and the calculated result is ; Comparing the actual reflection time: During real-time detection, if there is a large deviation between the actual arrival time of the ultrasonic reflection signal and the theoretical time, it indicates that the internal structure of the solder joint may have changed and there are defects. If the reflection time is advanced, there may be defects such as voids and lack of fusion inside the solder joint, shortening the ultrasonic propagation path; if the reflection time is delayed, it may be that there are inclusions locally in the solder joint, making the propagation path longer; for example, if the actually detected reflection time is , which is significantly less than the theoretical time, suggesting that there may be void-like defects in the solder joint; the large deviation standard in the above-mentioned large deviation between the actual arrival time of the ultrasonic reflection signal and the theoretical time is not a fixed value. It is affected by various factors and needs to be determined comprehensively according to the specific welding scenario, material characteristics and detection accuracy requirements. For example, small solder joints (solder joints of electronic chip pins, with dimensions below the millimeter level) are sensitive to time deviation, and the deviation standard is generally set at 5% - 10%. Because of their small size and short ultrasonic propagation path, minor defects may significantly change the propagation time. Assuming the theoretical time of a small solder joint is 2 μs, and the actual time exceeds 2.1 - 2.2 μs, it may indicate the existence of defects.

[0076] 3. Analysis based on the signal waveform morphology: Determining the normal waveform characteristics: By detecting normal solder joints, the typical waveform characteristics of their ultrasonic reflection signals are summarized, including the shape of the waveform, the number and position of wave peaks and wave valleys, the smoothness of the waveform, etc.: For example, the waveform of a normal solder joint usually has a regular shape, the wave peaks and wave valleys are evenly distributed, and the waveform is relatively smooth; Identifying abnormal waveforms: During real-time detection, if the waveform is distorted, such as the wave peak becomes wider, the wave valley becomes shallower, additional small wave peaks or wave valleys appear, etc., it may indicate that there are defects in the solder joint. Irregular waveform changes are often related to the uneven ultrasonic scattering and reflection caused by defects inside the solder joint; for example, if the normal waveform is single-peak and smooth, and the detected waveform has a double-peak and an irregular peak shape, it may mean that there are defects such as cracks in the solder joint, resulting in complex reflection and scattering of ultrasonic waves at the crack.

[0077] 4. Comprehensive analysis based on multiple parameters: Establish a defect determination model: Consider multiple parameters such as signal amplitude, reflection time, and waveform morphology comprehensively, and use methods such as machine learning and statistical analysis to establish a defect determination model; collect a large amount of solder joint data with known defect types and no defects as training samples, and train the model so that it can accurately identify the multi-parameter feature combinations corresponding to different defect types; Real-time determination application: Detect solder joints in real time during the welding process, input the obtained multi-parameter data into the established model, and the model judges whether there are defects in the solder joints and the types of defects according to the rules and experience obtained from training; For example, through model analysis, when the signal amplitude is lower than the lower limit of the normal range, the reflection time is advanced and the waveform is distorted, it is determined that the solder joint has a defect of a mixture of voids and cracks. This multi-parameter comprehensive analysis method can improve the accuracy and reliability of defect determination, especially for complex welding structures and situations where multiple defects coexist.

[0078] More specifically: The defects include void defects, crack defects, inclusion defects, and lack of fusion defects. Based on the above detection methods, various defects are illustrated through specific examples:

[0079] Void defect: In a certain chip production workshop, an ultrasonic detection module with a frequency of 5 MHz is used to detect the solder joints of a chip; the solder joint size is 0.8 mm in length, 0.6 mm in width, and 0.4 mm in height. Under normal circumstances, the propagation speed of ultrasonic waves in the solder joint material is about 3200 m / s; (1) Change in the amplitude of the reflection signal of void defects: By measuring normal solder joints multiple times, the average value of the reflection signal amplitude is obtained as 100 mV. When a solder joint with a void defect is detected, the reflection signal amplitude instantly rises to 180 mV; this is because the acoustic impedance difference between the void and the solder is relatively large, and ultrasonic waves are strongly reflected at the void interface, resulting in a significant increase in the reflection signal amplitude; (2) Shortening of the propagation time: The round-trip propagation distance of ultrasonic waves in a normal solder joint is about 2×0.4 mm = 0.8×10 -3 m, and the calculated normal propagation time is 0.8×10 -3 ÷3200 = 2.5×10 -7 s; when the void solder joint is detected, the actual measured propagation time is shortened to 2×10 -7 s, which indicates that the ultrasonic propagation path is shortened due to the presence of voids, further confirming the existence of voids; (3) Waveform distortion: The ultrasonic reflection waveform of a normal solder joint shows a regular single peak with a smooth peak shape, while the waveform of a solder joint with voids has an obvious small peak after the main reflection peak. This is because ultrasonic waves are reflected multiple times in the void, forming additional reflection signals that are superimposed on the original waveform; For the detection changes corresponding to the above void defects, they can be combined and used, as long as it can be determined that it is a void defect, and there is no specific limitation in this application.

[0080] Crack defect: Also in this chip production workshop, an ultrasonic detection module with a frequency of 5 MHz is used to detect the solder joints of another type of chip; the solder joint size is 0.8 mm in length, 0.6 mm in width, and 0.4 mm in height. Under normal circumstances, the propagation speed of ultrasonic waves in this solder joint material is about 3200 m / s; (1) Variation in the amplitude of the reflected signal of the crack defect: By measuring normal solder joints multiple times, the average amplitude of the reflected signal of normal solder joints is 105 mV. When a solder joint with a crack is detected, the amplitude of the reflected signal rises to 125 mV. Although the width of the crack is narrow, it can still cause ultrasonic waves to reflect. However, due to its geometric shape and distribution characteristics, the increase in the amplitude of the reflected signal is not as obvious as that of the void; (2) Uncertain variation in the propagation time of the crack defect: Assume that the crack is a crack vertically penetrating the thickness direction of the solder joint. Originally, the propagation distance of ultrasonic waves is 2 x 0.4 mm = 0.8 x 10 -3 m. After the crack appears, the propagation distance is shortened to 2 x 0.3 mm = 0.6 x 10 -3 m (assuming the crack depth is 0.1 mm); According to the propagation speed of 3200 m / s, the normal propagation time is 0.8 x 10 -3 ÷ 3200 = 2.5 x 10 -7 s. When there is a crack, the propagation time is 0.6 x 10 -3 ÷ 3200 = 1.875 x 10 -7 s, and the propagation time is significantly shortened; but if the crack is horizontal inside the solder joint, the propagation time may remain basically unchanged because the ultrasonic propagation path is not significantly changed. (3) Waveform characteristics of the crack defect: The waveform of a normal solder joint is a single and smooth wave peak. For the waveform of a solder joint with a crack, multiple small reflected wave peaks appear near the main reflected wave peak. This is because ultrasonic waves are reflected multiple times on the crack surface, and the wave signals of different reflection paths are superimposed, making the waveform complex; For the detection changes corresponding to the above crack defects, they can be combined for use as long as it can be determined that it is a crack defect. The present application does not make specific limitations.

[0081] Inclusion defect: Continuing in this chip production workshop, the solder joint material is tin-silver-copper alloy, and an ultrasonic detection module with a frequency of 4 MHz is used to detect the chip solder joints; the solder joint size is 0.8 mm in length, 0.6 mm in width, and 0.4 mm in height. Under normal circumstances, the propagation speed of ultrasonic waves in this solder joint material is about 3200 m / s; (1) Variation in the amplitude and propagation time of the inclusion defect: By measuring normal solder joints multiple times, the average amplitude of the reflected signal of normal solder joints is 95 mV, and the propagation time is 2.6 x 10 -7 s. When a solder joint containing metal oxide inclusions is detected, the amplitude of the reflected signal decreases to 70 mV. This is because the acoustic impedance of the metal oxide inclusions is different from that of the solder, resulting in weakened ultrasonic reflection. At the same time, due to the presence of the inclusions, the ultrasonic propagation path changes, and the propagation time is extended to 3 x 10-7 s. (2) Waveform change of inclusion defect: The waveform of a normal solder joint presents a regular sine wave shape. For the waveform of a solder joint containing inclusions, an obvious trough appears before the main reflection peak, and a smaller peak appears after the main reflection peak. This is because ultrasonic waves are repeatedly reflected and refracted at the interface between the inclusion and the solder, changing the original shape of the waveform. For the detection changes corresponding to the above inclusion defects, they can be used in combination as long as it can be determined that it is an inclusion defect. The present application does not make specific limitations.

[0082] Incomplete fusion defect: Use an ultrasonic detection module with a frequency of 6 MHz to detect the chip solder joints; the solder joint size is 0.7 mm in length, 0.5 mm in width, and 0.35 mm in height. Under normal circumstances, the propagation speed of ultrasonic waves in this solder joint material is about 3200 m / s. (1) Changes in amplitude and propagation time of incomplete fusion defect: After measuring a large number of normal solder joints, the average value of the reflected signal amplitude is 110 mV, and the propagation time is 2.2x10 -7 s. When detecting a solder joint with an incomplete fusion defect, the amplitude of the reflected signal rises significantly to 150 mV. This is because the acoustic characteristics of the materials on both sides of the incomplete fusion interface are quite different, resulting in strong ultrasonic reflection. At the same time, due to the incomplete fusion area hindering the normal propagation of ultrasonic waves, the propagation time is shortened to 1.8x10 -7 s, indicating that the ultrasonic wave fails to propagate to the expected depth along the normal path. (2) Waveform characteristics of incomplete fusion defect: The waveform of a normal solder joint is continuous and smooth. For the waveform of a solder joint with an incomplete fusion defect, an obvious interruption appears at the expected reflection wave position, and then an irregular reflection peak appears. This is because the ultrasonic wave is reflected at the incomplete fusion interface and cannot continue to propagate along the normal path. The subsequent reflected wave signal is superimposed on the original signal, resulting in a discontinuous and irregular waveform. For the detection changes corresponding to the above incomplete fusion defects, they can be used in combination as long as it can be determined that it is an incomplete fusion defect. The present application does not make specific limitations.

[0083] S6: The printing nozzle pauses printing the solder, and the printing parameters of the 3D printing device and the welding parameters of the welding machine are reset. Or after resetting the printing parameters of the 3D printing device and the welding parameters of the welding machine, the control system controls the printing nozzle and the welding machine to print and repair the solder joints at the defective positions.

[0084] The specific criteria for resetting the printing parameters and / or welding parameters of the 3D printing device are:

[0085] 1. The signal amplitude deviation is small and regular: When the amplitude of the ultrasonic reflection signal deviates by ±10% - ±20% compared with the amplitude of a normal solder joint, consider resetting the parameters. For example, if the average amplitude of the signal of a normal solder joint is 100 mV, and the amplitude of the solder joint fluctuates between 80 - 120 mV, it may be that small changes in the welding parameters have caused changes in the internal structure of the solder joint, but have not seriously affected its quality. This situation may be caused by small fluctuations in the solder extrusion amount, the temperature of the printing nozzle, or the moving speed of the printing nozzle. For example, a slightly less solder extrusion amount may result in a slightly lower internal density of the solder joint, causing the amplitude of the ultrasonic reflection signal to decrease. At this time, these parameters can be appropriately fine-tuned, such as increasing the solder extrusion amount by 5% - 10%, and / or raising the temperature of the printing nozzle by 10 - 20°C, and observing whether the ultrasonic detection signal of subsequent solder joints returns to normal.

[0086] 2. The reflection time deviation is small and consistent: If the actual arrival time of the ultrasonic reflection signal deviates from the theoretical time by within ±10%, preferably, when welding multiple solder joints, the deviation directions and degrees of multiple solder joints are relatively consistent, and it can be solved by resetting the parameters. For example, if the theoretical reflection time is 10 μs and the actual time is between 9 - 11 μs, it indicates that although there are changes in the internal structure of the solder joint, the overall situation is still within the acceptable range. This may be due to small changes in material properties during the welding process, such as the influence of the welding temperature on the solidification speed of the solder, resulting in a slight change in the ultrasonic propagation speed. It is possible to try to adjust the welding environment parameters, such as controlling the welding temperature in the welding area, or slightly adjusting the moving speed of the printing nozzle, to compensate for the change in the propagation time.

[0087] 3. The waveform shape is slightly abnormal but similar: When the ultrasonic detection waveform of the solder joint shows slight deformation, such as the shape of the wave peak or wave valley changes slightly, but the overall waveform is still similar to the normal waveform. Preferably, when welding multiple solder joints and multiple solder joints show the same slight abnormality, consider resetting the parameters. For example, the wave peak of the normal waveform is relatively sharp, while the detected wave peak becomes slightly wider, but there are no additional wave peaks or wave valleys. This slight waveform abnormality may be caused by slightly uneven distribution of the welding energy. It is possible to appropriately adjust the welding power or welding time to make the welding energy more evenly distributed, improve the internal structure of the solder joint, and thus make the waveform return to normal.

[0088] After resetting the printing parameters of the 3D printing device and the welding parameters of the welding machine, the specific criteria for the control system to control the printing nozzle and the welding machine to print and repair the solder joints at the defective positions are as follows:

[0089] 1. Excessive signal amplitude deviation: If the amplitude of the ultrasonic reflection signal is reduced by more than 30% or increased by more than 50% compared to the amplitude of a normal solder joint, it indicates that there are serious defects in the solder joint and printing repair is required. For example, if the normal amplitude is 100 mV and the detected amplitude is lower than 70 mV or higher than 150 mV, it means that there may be a large number of voids, porosity, inclusion removal, etc. inside the solder joint, which affects the propagation and reflection of ultrasonic waves. Such defects will seriously affect the electrical and mechanical properties of the solder joint. It is necessary to fill the voids and remove the inclusions through printing repair to restore the normal structure and performance of the solder joint. In this embodiment, the treatment method for inclusion removal can be as follows: Use a high-energy density laser beam to melt the filling material provided by the 3D printing device and cladding it on the inclusion part of the solder joint. During the laser cladding process, the high temperature can fully melt the inclusion impurities and cause physical and chemical reactions with the filling material. Some impurities may be evaporated or float to the surface and be removed. At the same time, laser cladding can precisely control the repair area to ensure the dimensional accuracy and performance of the solder joint after repair.

[0090] 2. Excessive reflection time deviation: When the actual arrival time of the ultrasonic reflection signal deviates from the theoretical time by more than ±20%, it means that there has been a large change in the internal structure of the solder joint, and there may be serious defects that require printing repair. For example, if the theoretical reflection time is 10 μs and the actual time is less than 8 μs or greater than 12 μs, it may be that there are large voids, cracks or unfused areas inside the solder joint, resulting in abnormal ultrasonic propagation paths. These defects will seriously weaken the connection strength and stability of the solder joint. It is necessary to print repair the defect location and reconstruct the solder joint structure to ensure its performance meets the requirements.

[0091] 3. Severe waveform distortion: If the ultrasonic detection waveform shows severe distortion, such as the appearance of multiple additional peaks and valleys, or the waveform as a whole becomes chaotic and is very different from the normal waveform, it indicates that there are complex and serious defects in the solder joint and printing repair should be carried out. For example, the normal waveform is a regular single peak, while the detected waveform has more than three peaks, and the spacing and amplitude between the peaks are irregular. This severe waveform distortion reflects the existence of complex defects inside the solder joint, such as multiple cracks intersecting and large-area unfusion. It is necessary to precisely control the filling and distribution of the solder through printing repair to repair the defects and restore the solder joint to normal.

[0092] The following are the specific repair methods for each defect:

[0093] Repair of void defects: The position and size information of the voids are obtained through ultrasonic detection. If it is detected that the voids cause a shortening of the propagation time, the size of the voids can be deduced. Based on this, the control system of the 3D printing device calculates the volume of solder required for filling. After the printing nozzle restarts, the corresponding volume of solder is precisely extruded to fill the voids. For example, if the deduced void volume is 0.03 m³, the printing nozzle extrudes an equal amount of solder with extremely high precision to ensure complete filling of the voids.

[0094] Repair of crack defects: According to the direction and length of the cracks, the printing nozzle plans the path and extrudes solder along the cracks to completely cover them. For cracks with a narrow width, the printing nozzle extrudes solder in a fine line to ensure that the cracks are filled. For example, for a crack with a width of 0.02 mm, the printing nozzle extrudes a solder line with a width of 0.03 mm for covering. At the same time, the extrusion amount of solder can be appropriately increased to improve the strength of the repaired part.

[0095] Repair of inclusion defects: A high-energy density laser beam is used to melt the filling material provided by the 3D printing device and cladding it on the inclusion part of the solder joint. During the laser cladding process, the high temperature can fully melt the inclusion impurities and cause physical and chemical reactions with the filling material. Some impurities may be evaporated or float to the surface and be removed. At the same time, laser cladding can precisely control the repair area to ensure the dimensional accuracy and performance of the solder joint after repair; alternatively, the inclusions can be sucked out through a tiny nozzle device or the like to form voids, and the printing nozzle precisely extrudes solder for filling. For example, if the void volume formed after sucking out the inclusions is 0.05 m³, the printing nozzle accurately extrudes the corresponding volume of solder to ensure the accuracy of filling.

[0096] Repair of lack of fusion defects: The position and size information of the lack of fusion are obtained through detection, and the size of the unfused part can be deduced. Based on this, the control system calculates the volume of solder required for filling. After the printing nozzle restarts, the corresponding volume of solder is precisely extruded for filling the lack of fusion, and the welding machine performs secondary welding on the unfused part.

[0097] S7: During the printing and repair process, the ultrasonic detection module continuously detects the solder joints to determine whether there are defects. Otherwise, continue welding; if yes, enter S6. The solder joint detection refers to S5 and will not be specifically described here.

[0098] Preferably, to further ensure the quality of chip welding, this embodiment further includes S8: For the welded chips, the ultrasonic transducer is used to comprehensively detect the quality of the solder joints, saving the detection equipment specifically for chip detection. In this step, since the solder joints have solidified, when problems are detected in the solder joints, they are regarded as defective chips for subsequent processing. Embodiment 2

[0099] This embodiment specifically defines S5:

[0100] In S5, the ultrasonic detection module completes the detection and feedback of whether there are defects in the solder joints before the solder joints solidify, which can detect defects in time, immediately adjust the printing parameters or take repair measures, avoid the difficulty of dealing with defects after the solder joints solidify, save time and cost, and improve production efficiency and product quality. For example, in the production of electronic products, timely detection and treatment of defects in non-solidified solder joints can reduce subsequent detection and rework processes; that is, it is necessary to control the ultrasonic detection time and the printing speed of the 3D printing device to ensure that the detection and feedback are completed before the solder joints solidify and gain time for defect repair; it should be noted that during the use of this embodiment, due to real-time detection, factors such as high temperature, strong electromagnetic field, and spatter will interfere with the ultrasonic signal, and metal spatter may impact the ultrasonic transducer of the ultrasonic detection module, affecting the detection. Shielding measures can be taken, such as wrapping the ultrasonic transducer with a metal shielding cover to reduce electromagnetic field interference; select the appropriate position and angle of the ultrasonic transducer to avoid direct impact of metal spatter on the ultrasonic transducer, and a protective device can also be set up to block spatter, etc.; in addition, the ultrasonic detection module needs to meet the requirements of high temperature resistance and harsh environment resistance. A special high-temperature-resistant ultrasonic detection module needs to be used, and its internal structure and materials can withstand the high temperature of the solder joints to prevent the ultrasonic transducer from being damaged or its performance from decreasing due to high temperature. At the same time, the circuit and electronic components also need to adapt to harsh environments such as high temperature and humidity to ensure stable operation. The specific structure is not specifically defined in this application, and those skilled in the art can make corresponding settings according to specific situations.

[0101] In S5, during the welding process, the ultrasonic detection module's real-time detection of the solder joints specifically includes the following steps:

[0102] S51: In the system of the 3D printing device, add an information module that can real-time feedback the position of the printing nozzle, the speed of the printing nozzle, and the estimated forming time of the solder joints; for example, by installing a high-precision displacement sensor on the 3D printing nozzle to accurately obtain the real-time position of the printing nozzle; use a speed sensor to monitor the printing speed of the printing nozzle, and combine the size of the estimated solder joints, the set printing path, and the current speed to calculate the estimated forming time of each solder joint; select an ultrasonic detection module that can respond quickly and has high-precision detection capabilities, and its detection frequency and sensitivity should be optimized according to the solder joint material, size, and possible defect types. Integrate the probe of the ultrasonic detection module near the printing area of the 3D printing device to ensure that the probe can detect immediately after the solder joint is formed; for example, for 3D printed solder joints of microchips, a high-frequency (such as 5 - 10 MHz) ultrasonic detection probe can be selected to improve the detection resolution of micro defects.

[0103] S52: Establish a communication link between the 3D printing device and the ultrasonic transducer to ensure real-time data transmission between the two. The communication link adopts a high-speed and reliable communication link, such as high-speed Ethernet or fiber optic communication technology, to achieve rapid data exchange between the two. At the same time, the control system can receive and analyze the data transmitted from the 3D printing device and the ultrasonic detection module in real time, and make decisions according to the preset algorithm.

[0104] S53: Set a unified time reference in the 3D printing device and the ultrasonic transducer. For example, use a high-precision clock module (atomic clock or high-precision crystal oscillator) to provide accurate time signals for the 3D printing device and the ultrasonic transducer to ensure their time consistency.

[0105] S54: Predict the forming time of each solder joint in advance according to the speed and path planning of the 3D printing device.

[0106] S55: Trigger the ultrasonic transducer to perform preheating and preparation work in advance before the solder joint is expected to be formed. For example, when the 3D printing device calculates that there is still 1 - 2 seconds until the next solder joint is formed, send a pre-trigger signal to the ultrasonic detection module to let the ultrasonic detection module adjust the parameters in advance and prepare for detection.

[0107] S56: The ultrasonic transducer emits ultrasonic waves to the solder joint before the solder joint solidifies and sends a signal to the signal receiving and processing unit before solidification.

[0108] Preferably, it further includes S57: Dynamically adjust the detection time point of the ultrasonic transducer in real time according to the fluctuation of the actual speed of the 3D printing device. For example, if the printing speed of the print head changes due to certain reasons (such as material supply changes, equipment vibration, etc.), the 3D printing device timely sends the new speed information and the expected solder joint forming time to the control system, and the control system recalculates and adjusts the detection time of the ultrasonic detection module to ensure detection is completed before the solder joint solidifies.

[0109] Optimize the data processing and feedback process of the control system for the ultrasonic detection module, and shorten the time from detection to feedback as much as possible. Adopt a high-speed data acquisition card and an efficient signal processing algorithm to quickly analyze and process the detected ultrasonic signals. For example, use a real-time signal processing module based on FPGA (Field Programmable Gate Array) to complete the feature extraction and defect judgment of the ultrasonic signals within a few milliseconds and feedback the results to the 3D printing device. Embodiment Three

[0110] This embodiment specifically describes S6:

[0111] In S6, before the control system controls the print head and the welder to perform print repair on the solder joints at the defective positions, the position of the defect in the solder joint is accurately determined by fusing the signal processing algorithm and the data of the ultrasonic detection module to provide accurate coordinates for 3D printing repair. The specific steps are as follows:

[0112] S61: Reasonably arrange multiple ultrasonic transducers around each solder joint to ensure that ultrasonic signals can be obtained from different angles. For example, 3 - 4 ultrasonic transducers can be evenly distributed above, on the side, etc. of the solder joint to fully cover the solder joint area;

[0113] S62: The ultrasonic transducers emit ultrasonic waves to the solder joint and receive the reflected signals, and record information such as the time and amplitude of the signals received by each ultrasonic transducer;

[0114] S63: The signal receiving and processing unit pre - processes the received electrical signals. The signal receiving and processing unit removes the noise in the ultrasonic signals, amplifies the filtered signals, enhances the amplitude of the signals for subsequent analysis, and amplifies the signal amplitude to an appropriate range, while paying attention to avoiding signal distortion;

[0115] S64: Extract time - related features from the pre - processed signals, such as the propagation time and reflection time of the signals. By measuring the time difference between the transmitted signal and the reflected signal, and combining the propagation speed of ultrasonic waves in the solder joint material, calculate the distance that the ultrasonic wave travels from the sensor to the defect position and then returns. For example, given that the propagation speed of ultrasonic waves in the solder joint material is , and the measured time difference is , then the propagation distance (divide by 2 because the distance is round - trip);

[0116] Analyze the amplitude change, signal reflection time change, and signal waveform change of the signals from the pre - processed signals. Different positions and types of defects will cause differences in the amplitude, reflection time, and signal waveform of the ultrasonic reflection signals. For example, a larger defect may cause the amplitude of the reflected signal to decrease significantly. By establishing a relationship model between the amplitude and the defect position and size, assist in determining the defect position;

[0117] S65: Calculate the coordinates of the defect position based on the data fusion of triangulation. For the data collected by the ultrasonic transducers, use the triangulation principle for fusion. Assume that the coordinates of three ultrasonic transducers , , are respectively ([[]] , ), ([[]] , ), ([[]] , ), from , , to the distances from the defect are respectively , , , respectively taking the ultrasonic transducers as , , the centers, and taking , , as the radii to draw circles. The intersection points of the three circles are the positions of the defects. The coordinates of the defects ( , ) can be obtained by solving the following equations (1), (2), and (3);

[0118] (1)

[0119] (2)

[0120] (3)

[0121] Preferably, in addition to triangulation, data fusion algorithms such as the weighted average method and the Kalman filtering method can also be used; the weighted average method assigns different weights according to the reliability of the data of each ultrasonic actuator, and then calculates the weighted average value to determine the defect position; the Kalman filtering method uses the state equation and the observation equation of the system to perform an optimal estimation of the defect position, and can effectively process the noise and uncertainty in the data, which belongs to the conventional prior art. The applicant will not elaborate specifically here, and those skilled in the art can make corresponding selections according to the specific situation.

[0122] S66: Convert the defect position coordinates calculated by the above method into the coordinates in the coordinate system recognizable by the 3D printing device; the conversion relationship between the coordinate system of the ultrasonic detection module and the coordinate system of the 3D printing device is to convert the coordinates through transformation matrices such as translation and rotation; preferably, in order to improve the accuracy of the converted coordinates, it is necessary to calibrate the entire detection and calculation process. Standard defect samples with known positions can be used for multiple detections and calculations, and the calculated defect positions are compared with the actual positions, and the calculation methods and parameters are adjusted and optimized according to the deviations to ensure that the defect position coordinates finally provided to the 3D printing device are accurate and reliable.

[0123] In the above S6, when the printing nozzle pauses printing the solder and re-sets the welding parameters of the 3D printing device, it includes:

[0124] When the defect is a cavity, adjust at least one of the solder extrusion amount, the moving speed of the printing nozzle, the welding temperature, the welding time, the welding power, the welding pressure, and the welding frequency of the 3D printing device; reduce the moving speed of the printing nozzle, and the reduction range is 20%-50% of the moving speed of the printing nozzle set in S2, ensuring that the solder fully fills the cavity. A lower speed allows the solder to have enough time to spread and solidify, reducing the problem of insufficient filling caused by rapid filling, avoiding the generation of cavity defects, and when a cavity defect needs to be repaired, it also allows the solder to have enough time to spread and solidify at the cavity; increase the welding temperature, increasing it by 20°C - 30°C based on the welding temperature set in S2, enhancing the fluidity of the solder, avoiding the generation of cavity defects, and when a cavity defect needs to be repaired, it enables better filling of the cavity; extend the welding time, extending it by 0.3 - 0.5 seconds based on the welding time set in S2, ensuring that the solder fully fuses with the surrounding solder joints, avoiding the generation of cavity defects, and when a cavity defect needs to be repaired, it can fill the cavity and fuse with the surrounding solder joints; increase the welding power, increasing it by 20% - 30% based on the original power in S2, rapidly increasing the temperature, accelerating the flow of the solder, avoiding the generation of cavity defects, and when a cavity defect needs to be repaired, it can fill the cavity; adjust the welding pressure, and the welding pressure for the cavity is preferably a pressure of 0.5N - 1N, which is higher than the normally set welding pressure, ensuring that the solder tightly combines with the surrounding of the cavity, avoiding the generation of cavity defects, and when a cavity defect needs to be repaired, it helps the solder fill the cavity. An appropriate pressure can make the solder better enter all corners of the cavity, improving the filling effect; increase the welding frequency, increasing it by 20% - 30% based on the welding frequency set in S2, avoiding the generation of cavity defects, and when a cavity defect needs to be repaired, the increase in frequency helps fill the cavity.

[0125] The calculation formula for the adjusted solder extrusion amount is: , where M represents the adjusted solder extrusion amount; represents the solder extrusion amount set in S2; represents the increased solder amount, , represents the density of the solder, represents the spreading and loss coefficient of the solder when filling the cavity. The value range of S is 1.2 - 1.5, V represents the volume of the cavity, , r is the radius of the cavity. It is necessary to analyze the approximate volume of the cavity through the ultrasonic detection signal. Assuming the cavity is approximately regarded as a sphere, based on information such as the intensity and time difference of the ultrasonic reflection signal, the cavity radius can be estimated.

[0126] Based on the above description, in a 3D printing device, the extrusion amount of solder is usually adjusted by the rotational speed of the motor that conveys the solder. The relationship between the set motor rotational speed and the extrusion amount of solder is set to be linear. Given that the extrusion amount of solder corresponding to the motor rotational speed n per unit time is hl (calibrated through experiments), then in order to extrude an additional , the increase in the motor rotational speed .

[0127] In another scheme, the calculation formula for the solder extrusion amount is: , where M represents the adjusted solder extrusion amount; represents the solder extrusion amount set in S2; d represents the distance from the void position to the center of the solder joint, , the midline coordinates of the solder joint are ( , , ), and the coordinates of the void position are (X, Y, Z); j represents the solder extrusion amount coefficient, and d has a linear relationship with j. For every 1 mm increase in d, j increases by 0.05.

[0128] When the defect is a crack, adjust at least one of the printing nozzle temperature, printing nozzle moving speed, welding temperature, welding time, welding power, welding pressure, and welding frequency; increase the welding temperature, increasing it by 10°C - 20°C based on the welding temperature set in S2, which helps enhance the fluidity of the solder, avoid the generation of crack defects, and when the crack defect needs to be repaired, it can make the solder flow into the crack better; extend the welding time, extending it by 0.2 - 0.4 seconds based on the welding time set in S2, avoid the generation of crack defects, and when the crack defect needs to be repaired, it can ensure that the solder is fully fused with the material at the crack; increase the welding power, increasing it by 10% - 20% based on the original power in S2, avoid the generation of crack defects, and when the crack defect needs to be repaired, increasing the power can promote the infiltration and fusion of the solder at the crack; adjust the welding pressure, and the welding pressure for cracks is preferably 0.3 - 0.8 N, avoid the generation of crack defects, and when the crack defect needs to be repaired, it helps promote the solder to flow into the crack and enhance the bonding strength between the solder and the materials on both sides of the crack; increase the welding frequency, increasing it by 10% - 20% based on the welding frequency set in S2, avoid the generation of crack defects, and when the crack defect needs to be repaired, the increase in frequency helps fill the crack.

[0129] More specifically, adjust the printing nozzle moving speed according to the length and direction of the crack, and adjust the printing nozzle temperature according to the crack depth.

[0130] The calculation formula for the moving speed of the printing nozzle is: ; where represents the adjusted moving speed of the printing nozzle; Represents the moving speed of the print head set in S2; Represents the crack length; D represents the speed change amount corresponding to the unit crack length. For every 1 mm of crack length, the change amount of D is ; Represents the included angle correction coefficient, , is the included angle between the crack direction and the moving direction of the print head. When the crack direction is perpendicular to the moving direction of the print head, , , the speed is not adjusted; when the directions are inconsistent, , ; The adjusted moving speed of the print head is .

[0131] The calculation formula for the temperature of the print head is: ; where, Represents the adjusted temperature of the print head; Represents the temperature of the print head set in S2; h represents the crack depth; Represents the temperature change amount corresponding to the unit crack depth. Through experiments, it is determined that for every 1 μm of crack depth, the change amount of is 1.5.

[0132] When the defect is an inclusion defect, at least one of the printing nozzle moving speed, welding temperature, welding time, welding pressure, and welding frequency is adjusted; the moving speed of the printing nozzle is reduced, and the printing speed is reduced by 10%-20% of the printing nozzle temperature set in S2, so that the solder has more sufficient time to fill the solder joint area, reducing the problem of uneven solder distribution caused by inclusions, avoiding the generation of inclusion defects, and facilitating the repair of inclusion defects when they occur; the welding temperature is increased by 10-20°C on the basis of the setting in S2, which helps the solder to melt and flow better, enabling the inclusions to better fuse with the solder or be extruded, avoiding the generation of inclusion defects, and facilitating the repair of inclusion defects when they occur; the welding time is extended, usually by increasing 0.5-1 second on the basis of the welding time set in S2, allowing the solder to have more time to interact with the inclusions, improving the welding quality, avoiding the generation of inclusion defects, and facilitating the repair of inclusion defects when they occur; the welding pressure is increased by 0.1-0.2N on the basis of the welding pressure set in S2, avoiding the generation of inclusion defects, and helping to extrude the inclusions from the solder joint or make them better combine with the solder when inclusion defects occur; the adjustment of the frequency is specifically set according to the situation of the inclusions. For example, when encountering small and easily dispersed inclusions, the welding frequency can be appropriately increased. For example, when the frequency is in the range of 200Hz - 500Hz, the higher value in this range, 400Hz - 500Hz, is selected; when the inclusions are large or hard, a lower frequency (laser welding) should be used, and the frequency can be adjusted to the range of 10Hz - 30Hz.

[0133] When the defect is an unfused defect, at least one of the printing nozzle moving speed, welding temperature, welding time, welding pressure, welding power, and welding frequency is adjusted; the moving speed of the printing nozzle is reduced, and the printing nozzle speed is reduced to 30% - 50% of the printing nozzle temperature in S2. This can allow the solder to have more sufficient time to spread on the solder joint, reduce the generation rate of unfused defects, and when repairing unfused defects, enable the newly extruded solder to better contact and fill the gap with the original material; the welding temperature is increased by 30°C - 40°C based on the welding temperature set in S2, providing sufficient heat to fully melt the solder, avoiding the occurrence of unfused defects, and promoting the fusion of the solder in the unfused area when repairing unfused defects; the welding time is extended by 0.4 - 0.6 seconds based on the welding time set in S2. The extended time is to ensure that the solder has sufficient time to melt and fuse under sufficient heat, avoiding the occurrence of unfused defects, and promoting the fusion of the solder in the unfused area when repairing unfused defects; the welding power is increased by 30% - 40% based on the welding power set in S2, which can accelerate the heat transfer and make the solder reach the melting state faster, avoiding the occurrence of unfused defects; the welding pressure is adjusted. When unfused defects occur, the welding pressure is preferably 0.6N - 1.2N, which can make the unfused interface in close contact, help the solder better fill the gap and fuse, avoid the occurrence of unfused defects, and ensure that the solder can better fill the unfused area under the action of pressure when repairing unfused defects, enhancing the bonding strength of the solder joint; the welding frequency is increased by 10 - 30% relative to the welding frequency set in the original S2. The frequency can accelerate the fusion speed of the unfused interface, avoid the occurrence of unfused defects, and flow and fuse more quickly when repairing unfused defects, improving the quality of the solder joint. Example 4

[0134] This embodiment provides a chip welding device, including:

[0135] 3D printing device: precisely print the solder onto the connection part between the chip and the substrate according to a preset path; specifically, the 3D printing device includes a 3D printing nozzle, a solder delivery system, and a motion control platform: Solder delivery system: connected to the 3D printing nozzle, used to provide solder for the 3D printing nozzle; 3D printing nozzle: used to precisely print the solder delivered by the solder delivery system onto the connection part between the chip and the substrate; Motion control platform: connected to the 3D printing nozzle, used to control the movement of the 3D printing nozzle.

[0136] Welding device: weld the chip and the substrate together;

[0137] Ultrasonic detection module: Detect the quality of solder joints; the ultrasonic detection module includes an ultrasonic generator and an ultrasonic transducer; Ultrasonic generator: Generate high-frequency electrical signals; Ultrasonic transducer: Connected to the ultrasonic generator, convert the high-frequency electrical signals of the ultrasonic generator into ultrasonic waves, transmit them to the solder joints to be detected, receive the ultrasonic signals reflected and scattered by the solder joints, and convert them into electrical signals;

[0138] Signal reception and processing unit: Connected to the ultrasonic detection module, the signal reception and processing unit analyzes the signals fed back by the ultrasonic detection module to judge the quality of the solder joints; More specifically, connected to the ultrasonic transducer, the ultrasonic transducer transmits the electrical signal to the signal reception and processing unit, and the signal reception and processing unit judges the quality of the solder joints according to the received electrical signal.

[0139] Control system: Reset the printing parameters of the 3D printing device and / or the welding parameters of the welding machine, or after resetting the printing parameters of the 3D printing device and / or the welding parameters of the welding machine, the control system controls the printing nozzle and the welding machine to perform printing repair on the solder joints at the defective positions; and can calculate data such as the volume of the cavity, the depth and length of the crack, etc.

[0140] This application welds the photovoltaic panel through the cooperation of the 3D printing device and the ultrasonic detection device, and has the following advantages:

[0141] (1) Utilize ultrasonic waves to monitor the internal quality of solder joints in real time, without contacting the solder joints, and can ensure the accuracy of defect detection;

[0142] (2) Adopt the precise control advantages of the 3D printing device for the moving speed of the printing nozzle, the solder extrusion amount, and the temperature of the printing nozzle to realize the timely response and repair of welding defects and ensure the welding quality;

[0143] (3) Adjust the printing parameters of the 3D printing device and the welding parameters of the welding machine in real time according to the defects, or after adjusting the parameters, control the printing nozzle and the welding machine of the 3D printing device to perform secondary printing repair on the solder joints at the defective positions; avoid welding problems in the whole batch due to problems with welding parameters, etc., resulting in low work efficiency.

[0144] The connection relationships in the present invention are all connection methods well-known in the prior art, such as electrical connection and other connection methods. Those skilled in the art can make selections according to specific circumstances. Any changes in simple connection methods fall within the protection scope of the present invention. However, this application is not limited to the specific details in the above embodiments. Within the technical concept scope of this application, various simple modifications can be made to the technical solutions of this application, and these simple modifications all fall within the protection scope of this application. Additionally, it should be noted that for the various specific technical features described in the above specific embodiments, they can be combined in any appropriate manner without conflict. To avoid unnecessary repetition, various possible combination methods of this application will not be described separately.

[0145] In addition, any combination can be made among various different embodiments of this application as long as it does not violate the idea of this application, and it should also be regarded as the content disclosed in this application.

Claims

1. A chip soldering method, characterized in that, It includes the following steps: S1: Pretreat the chip and the substrate; S2: Set the printing parameters of the 3D printing device and the welding parameters of the welding machine. The printing parameters include the moving speed of the printing nozzle, the solder extrusion amount, and the temperature of the printing nozzle; the welding parameters include the welding temperature, the welding time, the welding power, the welding pressure, and the welding frequency; S3: Calibrate the ultrasonic detection module; S4: The printing nozzle of the 3D printing device prints solder, and the chip is welded by the welding machine; S5: During the welding process, the ultrasonic detection module detects the solder joints in real time to determine whether there are defects in the solder joints. If not, continue welding; if so, enter S6. Solder joint defects include void defects, crack defects, inclusion defects, and lack of fusion defects. Among them, when the solder joint defect is a void defect, the calculation formula for the solder extrusion volume is: , where M represents the adjusted solder extrusion volume; represents the solder extrusion volume set in S2; represents the increased solder volume, = represents the density of the solder, represents the spreading and loss coefficient of the solder when filling the voids. The value range of S is 1.2 - 1.5, and V represents the volume of the void; or the calculation formula for the solder extrusion volume is: , where M represents the adjusted solder extrusion volume; represents the solder extrusion volume set in S2; d represents the distance from the void position to the center of the solder joint, , and the midline coordinates of the solder joint are ( , , ), and the coordinates of the void position are (X, Y, Z); j represents the solder extrusion volume coefficient, and d and j are linearly related. For every 1 mm increase in d, j increases by 0.05; S6: The control system controls the printing nozzle to pause printing solder, reset the printing parameters of the 3D printing device and / or the welding parameters of the welding machine, or after resetting the printing parameters of the 3D printing device and / or the welding parameters of the welding machine, the control system controls the printing nozzle and the welding machine to print and repair the solder joints at the defective positions; S7: During the printing repair process, the ultrasonic detection module detects the solder joints in real time to determine whether there are defects in the solder joints. Otherwise, continue welding. If yes, enter S6.

2. The chip soldering method according to claim 1, wherein In S5, the ultrasonic detection module completes the detection and feedback of whether there are defects in the solder joints before the solder joints solidify.

3. A chip soldering method according to claim 1, characterized in that, In S5, during the welding process, the ultrasonic detection module detects the solder joints in real time, including the following steps: S51: In the 3D printing device system, add an information module that can feedback the position of the printing nozzle, the printing speed, and the expected solder joint forming time in real time; S52: Establish a communication link between the 3D printing device and the ultrasonic transducer of the ultrasonic detection module to ensure that the data between the two can be transmitted in real time; S53: Set a unified time reference in the 3D printing device and the ultrasonic transducer; S54: According to the speed and path planning of the 3D printing device, predict the forming time of each solder joint in advance; S55: Before the expected forming of the solder joint, trigger the ultrasonic transducer in advance for preheating and preparation work; S56: The ultrasonic transducer emits ultrasonic waves to the solder joint before the solder joint solidifies and sends a signal to the signal receiving and processing unit before solidification.

4. A chip soldering method according to claim 1, characterized in that, When the solder joint defect is a crack defect, the calculation formula for the moving speed of the printing nozzle is: ; where represents the adjusted moving speed of the printing nozzle; represents the moving speed of the printing nozzle set in S2; represents the crack length; D represents the speed change amount corresponding to the unit crack length. For every 1 mm of crack length, the change amount of D is ; represents the angle correction coefficient, , is the angle between the crack direction and the moving direction of the printing nozzle.

5. A chip soldering method according to claim 1, characterized in that, When the solder joint defect is a crack defect, the calculation formula for the temperature of the printing nozzle is: ; where represents the temperature of the adjusted printing nozzle; represents the temperature of the printing nozzle set in S2; h represents the crack depth; represents the temperature change amount corresponding to the unit crack depth. For every 1μm crack depth, the change amount is 1.5°C.

6. A chip soldering device, characterized in that, It includes: 3D printing device: Precisely print the solder along a preset path to the connection part between the chip and the substrate; Welding device: Weld the chip and the substrate; Ultrasonic detection module: Detect the quality of the solder joints; Signal receiving and processing unit: Connect to the ultrasonic detection module. The signal receiving and processing unit analyzes the signals feedback by the ultrasonic detection module to judge the quality of the solder joints; Control system: Adjust the welding parameters of the 3D printing device in real time according to the ultrasonic detection results and / or repair the problematic solder joints.

7. A chip soldering device according to claim 6, wherein The ultrasonic detection module includes an ultrasonic generator and an ultrasonic transducer: Ultrasonic generator: Generate high-frequency electrical signals; Ultrasonic transducer: Connect to the ultrasonic generator, convert the high-frequency electrical signals of the ultrasonic generator into ultrasonic waves, transmit them to the solder joints to be detected, receive the ultrasonic signals reflected and scattered by the solder joints, convert them into electrical signals, and transmit the electrical signals to the signal receiving and processing unit.

Images