Micro-scale tin soldering device and method cooperatively regulated and controlled by ultrasonic laser composite energy field

Abstract

The invention discloses a micro-scale tin soldering device and method for ultrasonic laser composite energy field coordinated regulation and control. The micro-scale tin soldering device comprises a coordinated energy output module, a multi-physical field monitoring module, a wire feeding module, an intelligent regulation and control system and a motion platform, and a workpiece to be welded is arranged on the motion platform; the collaborative energy output module comprises a laser unit, an ultrasonic vibration unit and a focusable focus lens, the ultrasonic vibration unit comprises an ultrasonic generator, and the multi-physical field monitoring module comprises an infrared thermometer, a high-speed holographic imaging system and an acoustic impedance sensor; the high-speed holographic imaging system is used for recording brazing filler metal molten pool flowing and IMC nucleation dynamic states; the acoustic impedance sensor monitors the ultrasonic energy transmission efficiency; the intelligent regulation and control system is electrically connected with the multi-physics field monitoring module, and a multi-physics field coupling prediction model based on an LSTM neural network is arranged in the intelligent regulation and control system. According to the technical scheme, the structural design is reasonable, the energy field coupling efficiency is high, the material adaptability is high, the structure performance is controllable, the defect rate is remarkably reduced, and practicability is good.

Description

Technical Field

[0001] This invention relates to the field of microelectronic packaging and soldering technology, specifically to a microscale soldering device and method for coordinated control of ultrasonic and laser composite energy fields. Background Technology

[0002] With the rapid development of 5G communication, artificial intelligence and other fields, the packaging density of integrated circuits continues to increase, and the welding quality of micro-scale solder joints has become a key factor restricting the reliability of devices.

[0003] The existing technology has the following limitations:

[0004] 1. Single-energy field welding has significant defects: laser soldering has a small heat-affected zone but the IMC layer is prone to being too thick (>5μm), while ultrasonic soldering has good wettability but is prone to causing edge stress concentration;

[0005] 2. The coupling method of the composite energy field is crude: laser and ultrasound are mostly arranged coaxially, with low energy utilization (<70%), and lack parameter adaptation mechanism for different substrate-solder combinations;

[0006] 3. Lack of organization and defect control: The quantitative correlation between "energy field parameters - IMC organization - solder joint performance" has not been established, and the reliance on experience and trial and error has led to large fluctuations in defect rate during mass production.

[0007] Therefore, there is an urgent need to develop a welding technology with precise energy field coupling and intelligent control capabilities to solve the problem of high-quality forming of microscale weld joints in multi-material systems. Summary of the Invention

[0008] To address the shortcomings of existing technologies, the present invention aims to provide a microscale soldering device and method with reasonable structural design, high energy field coupling efficiency, strong material adaptability, controllable microstructure and properties, significantly reduced defect rate, and good practicality, featuring synergistic control of ultrasonic-laser composite energy fields.

[0009] To achieve the above objectives, the present invention provides the following technical solution: a microscale soldering device for coordinated control of ultrasonic and laser composite energy fields, comprising a coordinated energy output module, a multi-physics field monitoring module, a wire feeding module, an intelligent control system, and a motion platform, wherein a workpiece to be soldered is disposed on the motion platform, and the workpiece to be soldered includes an IMC solder joint and a substrate;

[0010] The collaborative energy output module includes a laser unit, an ultrasonic vibration unit, and an adjustable focusing lens. The laser unit uses a fiber laser, and the spot diameter can be continuously adjusted from 50 to 200 μm through the adjustable focusing lens. The ultrasonic vibration unit includes an ultrasonic generator, which is located directly below the motion platform.

[0011] The multiphysics monitoring module includes an infrared thermometer, a high-speed holographic imaging system, and an acoustic impedance sensor. The infrared thermometer collects the temperature field distribution in the welding area; the high-speed holographic imaging system records the flow of the solder pool and the dynamics of IMC nucleation; and the acoustic impedance sensor monitors the ultrasonic energy transmission efficiency.

[0012] The intelligent control system is electrically connected to the multiphysics monitoring module, and the intelligent control system has a built-in multiphysics coupling prediction model based on LSTM neural network, which dynamically adjusts the laser power, ultrasonic frequency and wire feeding rate according to real-time monitoring data.

[0013] Preferably, the intelligent control system includes a process parameter self-learning module, which optimizes the prediction model based on welding data and controls the IMC thickness prediction error to within 8%.

[0014] Preferably, the intelligent control system further includes a storage device for storing the optimal parameter mapping relationship between different substrates and solders.

[0015] Preferably, the laser unit has an output power of 50-100W, and the angle between the laser beam and the substrate normal is adjustable within the range of 0°-15° via a two-dimensional rotary table; the ultrasonic generator has an ultrasonic frequency of 20-40kHz, an amplitude of 5-20μm, and a power of 50-150W; the infrared thermometer has a resolution of 1024×768, a temperature measurement range of 100-500℃, and a sampling rate of 1kHz; the high-speed holographic imaging system has a frame rate of 5000fps and a spatial resolution of 1μm; and the acoustic impedance sensor has a sampling rate of 10MHz and a monitoring ultrasonic energy transmission efficiency of ≥90%.

[0016] Preferably, the multiphysics coupling prediction model dynamically adjusts the laser power to ±5W accuracy, the ultrasonic frequency to ±0.5kHz accuracy, and the wire feeding rate to 0.5-1.5mm / s based on real-time monitoring data.

[0017] The present invention also provides a soldering method using a microscale soldering device with synergistic control of ultrasonic-laser composite energy fields as described above, comprising the following steps:

[0018] S1. Interface Preprocessing:

[0019] (1) The Cu substrate was etched by Ar / O2 plasma with a volume ratio of 9:1, a power of 50-100W, a time of 30-60s, and a surface roughness Ra≤0.5μm.

[0020] (2) The Al substrate is subjected to anodizing treatment at 15V for 10min to form a hydrophilic oxide layer;

[0021] (3) The Ni substrate is electroless nickel plating with a thickness of 5μm to reduce the interfacial reactivity;

[0022] The laser focus, ultrasonic action point, and wire feeding point are calibrated using a spatial coupling mechanism, with a deviation ≤20μm.

[0023] S2. Parameter Initialization: Based on the weld joint size D and material combination, the intelligent control system database is invoked.

[0024] (1) When D≤100μm(Ni / Sn-Ni): laser power 100-150W, ultrasonic frequency 35-40kHz, power 50-80W;

[0025] (2) When 100μm<D≤500μm(Cu / Sn-Ni): laser power 150-250W, ultrasonic frequency 25-35kHz, power 80-120W;

[0026] (3) When Al / Sn-Ag-Cu: laser power 200-300W (compensating for high reflectivity), ultrasonic frequency 20-30kHz, power 100-150W;

[0027] The wire feed rate V is linearly related to the laser power, V = 0.005 × P1, unit: mm / s;

[0028] S3. Timing-based collaborative welding:

[0029] (1) Preheating stage (0-5ms): Laser acts alone to heat to the melting point of the brazing filler metal and float up 30-50℃, with the heating rate controlled at 50-80℃ / ms;

[0030] (2) Composite stage (5-50ms): Ultrasonic vibration starts, and wire is fed synchronously; the intelligent system adjusts parameters according to monitoring data: if the molten pool spreading rate is <0.1mm / ms, the ultrasonic power is increased by 5-10W; if the temperature exceeds the melting point by 50℃, the laser power is reduced by 10-15W.

[0031] (3) Solidification stage (50-100ms): Stop wire feeding and turn off the laser. Reduce the ultrasonic power to 50-60% and maintain it for 50-100ms to promote IMC homogenization.

[0032] S4. Quality Inspection: Internal defects are detected using a laser scanning acoustic microscope (5μm resolution), and shear strength is tested using a micro tensile testing machine (±0.1MPa accuracy). If the quality does not meet the standard, return to the S2 optimization parameters.

[0033] Preferably, in step S3, the energy coupling coefficient K is defined as K = P1 / (P u When K∈[0.02-0.05]W·kHz / W, the IMC layer thickness stabilizes at 1-3μm.

[0034] (1) The optimal K for the Cu / Sn-Ni system is 0.04-0.05;

[0035] (2) The optimal K for the Al / Sn-Ag-Cu system is 0.03-0.04;

[0036] (3) The optimal K for the Ni / Sn-Ni system is 0.02-0.03.

[0037] As a preferred option, in the composite stage of step S3, the LSTM model takes temperature gradient, sound pressure amplitude and molten pool flow velocity as input, and outputs IMC thickness and defect probability. The model is trained with 500 sets of experimental data and the prediction error is ≤8%.

[0038] The beneficial effects of this invention are as follows: Compared with the prior art, this invention has a reasonable structural design. Addressing the problems of coarse intermetallic compound (IMC) microstructure, high defect rate, and poor material adaptability in existing welding technologies, this invention constructs a "thermal-acoustic-mass" multi-parameter closed-loop control mechanism through the adjustable coupling of laser thermal field and ultrasonic vibration energy field, combined with a multi-physics field monitoring and intelligent control system. The soldering device includes a collaborative energy output module, a multi-physics field monitoring module, and an intelligent control system, adaptable to Cu, Al, Ni substrates, and solder systems such as Sn-Ni and Sn-Ag-Cu. The soldering method achieves IMC microstructure refinement (1-3μm) and precise defect rate suppression (≤5%) through energy field timing matching, parameter dynamic optimization, and weak vibration coordination during solidification. The microscale soldering device and method using ultrasonic-laser composite energy field synergistic control achieves a solder joint shear strength ≥70MPa and an increase in conductivity of over 15%, suitable for microscale solder joint (50-500μm) welding of high-density integrated circuits, with the following significant advantages:

[0039] 1. High energy field coupling efficiency: The adjustable angle design and energy matching algorithm improve the energy transfer efficiency from 70% to over 90%, and reduce the heat-affected zone to within 50μm, avoiding thermal damage to components;

[0040] 2. Strong material adaptability: Through differentiated parameter matching and database support, high-quality welding of Cu, Al, and Ni substrates with Sn-based solder can be achieved without replacing core components;

[0041] 3. Controllable microstructure and properties: The IMC layer thickness is stabilized at 1-3μm by adjusting the energy coupling coefficient K, the grain size deviation is <10%, and the shear strength is increased by 40% (≥70MPa);

[0042] 4. Significantly reduced defect rate: The combination of weak vibration during solidification and closed-loop control reduces the total defect rate, such as poor solder joints and microcracks, to below 5%, while increasing electrical conductivity by 15%, meeting the reliability requirements of high-end packaging.

[0043] This invention has significant technological innovation and industrial application value.

[0044] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0045] Fig. 1 This is a schematic diagram of the structure of an embodiment of the present invention;

[0046] Fig. 2 The diagram shows the flow velocity distribution of the thermal flow field under different ultrasonic frequencies and laser powers in an embodiment of the present invention.

[0047] Fig. 3 Metallographic images of weld joints under different ultrasonic frequencies and laser powers according to embodiments of the present invention. Detailed Implementation

[0048] In the description of this embodiment, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," "outer," "front," and "rear," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0049] See Figs. 1 to 3 The present invention discloses a microscale soldering device for coordinated control of ultrasonic and laser composite energy fields, comprising a coordinated energy output module 1, a multi-physics field monitoring module 2, a wire feeding module 3, an intelligent control system 4, and a motion platform 6. The motion platform 6 is provided with a workpiece 5 to be soldered, which includes an IMC solder joint 501 and a substrate 502.

[0050] The collaborative energy output module includes a laser unit 101, an ultrasonic vibration unit 102, and an adjustable focusing lens. The laser unit is a fiber laser, and the spot diameter can be continuously adjusted from 50 to 200 μm through the adjustable focusing lens. The ultrasonic vibration unit includes an ultrasonic generator, which is located directly below the motion platform.

[0051] The multiphysics monitoring module includes an infrared thermometer, a high-speed holographic imaging system, and an acoustic impedance sensor. The infrared thermometer collects the temperature field distribution in the welding area; the high-speed holographic imaging system records the flow of the solder pool and the dynamics of IMC nucleation; and the acoustic impedance sensor monitors the ultrasonic energy transmission efficiency.

[0052] The intelligent control system is electrically connected to the multiphysics monitoring module, and the intelligent control system has a built-in multiphysics coupling prediction model based on LSTM neural network, which dynamically adjusts the laser power, ultrasonic frequency and wire feeding rate according to real-time monitoring data.

[0053] Preferably, the intelligent control system includes a process parameter self-learning module, which optimizes the prediction model based on welding data and controls the IMC thickness prediction error to within 8%.

[0054] The intelligent control system also includes a storage device for storing the optimal parameter mapping relationship between different substrates and solders.

[0055] The laser unit has an output power of 50-100W, and the angle between the laser beam and the substrate normal is adjustable within the range of 0°-15° via a two-dimensional rotary table; the ultrasonic generator has an ultrasonic frequency of 20-40kHz, an amplitude of 5-20μm, and a power of 50-150W; the infrared thermometer has a resolution of 1024×768, a temperature measurement range of 100-500℃, and a sampling rate of 1kHz; the high-speed holographic imaging system has a frame rate of 5000fps and a spatial resolution of 1μm; the acoustic impedance sensor has a sampling rate of 10MHz and monitors ultrasonic energy transmission efficiency ≥90%.

[0056] The multiphysics coupling prediction model dynamically adjusts the laser power (±5W accuracy), ultrasonic frequency (±0.5kHz accuracy), and wire feed rate (0.5-1.5mm / s) based on real-time monitoring data.

[0057] This invention also provides a soldering method for a microscale soldering device with synergistic control of ultrasonic-laser composite energy fields, comprising the following steps:

[0058] S1. Interface Preprocessing:

[0059] (1) The Cu substrate was etched by Ar / O2 plasma with a volume ratio of 9:1, a power of 50-100W, a time of 30-60s, and a surface roughness Ra≤0.5μm.

[0060] (2) The Al substrate is subjected to anodizing treatment at 15V for 10min to form a hydrophilic oxide layer;

[0061] (3) The Ni substrate is electroless nickel plating with a thickness of 5μm to reduce the interfacial reactivity;

[0062] The laser focus, ultrasonic action point, and wire feeding point are calibrated using a spatial coupling mechanism, with a deviation ≤20μm.

[0063] S2. Parameter Initialization: Based on the weld joint size D and material combination, the intelligent control system database is invoked.

[0064] (1) When D≤100μm(Ni / Sn-Ni): laser power 100-150W, ultrasonic frequency 35-40kHz, power 50-80W;

[0065] (2) When 100μm<D≤500μm(Cu / Sn-Ni): laser power 150-250W, ultrasonic frequency 25-35kHz, power 80-120W;

[0066] (3) When Al / Sn-Ag-Cu: laser power 200-300W (compensating for high reflectivity), ultrasonic frequency 20-30kHz, power 100-150W;

[0067] The wire feed rate V is linearly related to the laser power, V = 0.005 × Pl, unit: mm / s;

[0068] S3. Timing-based collaborative welding:

[0069] (1) Preheating stage (0-5ms): Laser acts alone to heat to the melting point of the brazing filler metal and float up 30-50℃, with the heating rate controlled at 50-80℃ / ms;

[0070] (2) Composite stage (5-50ms): Ultrasonic vibration starts, and wire is fed synchronously; the intelligent system adjusts parameters according to monitoring data: if the molten pool spreading rate is <0.1mm / ms, the ultrasonic power is increased by 5-10W; if the temperature exceeds the melting point by 50℃, the laser power is reduced by 10-15W.

[0071] (3) Solidification stage (50-100ms): Stop wire feeding and turn off the laser. Reduce the ultrasonic power to 50-60% and maintain it for 50-100ms to promote IMC homogenization.

[0072] S4. Quality Inspection: Internal defects are detected using a laser scanning acoustic microscope (5μm resolution), and shear strength is tested using a micro tensile testing machine (±0.1MPa accuracy). If the quality does not meet the standard, return to the S2 optimization parameters.

[0073] Preferably, in step S3, the energy coupling coefficient K is defined as K = Pl / (P u When K∈[0.02-0.05]W·kHz / W, the IMC layer thickness stabilizes at 1-3μm.

[0074] (1) The optimal K for the Cu / Sn-Ni system is 0.04-0.05;

[0075] (2) The optimal K for the Al / Sn-Ag-Cu system is 0.03-0.04;

[0076] (3) The optimal K for the Ni / Sn-Ni system is 0.02-0.03.

[0077] As a preferred option, in the composite stage of step S3, the LSTM model takes temperature gradient, sound pressure amplitude and molten pool flow velocity as input, and outputs IMC thickness and defect probability. The model is trained with 500 sets of experimental data and the prediction error is ≤8%.

[0078] This invention constructs a technical system of "precise energy coupling—real-time process monitoring—closed-loop quality control" through device structure innovation and method mechanism optimization, as detailed below:

[0079] 1. Innovative device design

[0080] (1) Collaborative energy output module: The laser and ultrasound are arranged at an angle of 30°-60° (non-traditional coaxial design). The energy coupling efficiency is improved to more than 90% through stepped amplitude rod and polarization control technology. The two-dimensional rotary table and precision guide rail ensure that the deviation of the energy application point is ≤20μm, which can adapt to the needs of welding joints of different sizes.

[0081] (2) Multiphysics monitoring module: Integrating infrared temperature measurement, high-speed holographic imaging and acoustic impedance sensing, it realizes full-scale monitoring from macroscopic temperature field to microscopic molten pool flow (spatial resolution 1μm, temporal resolution 200μs), providing data support for parameter optimization.

[0082] (3) Intelligent control system: Based on the LSTM neural network, a prediction model is constructed and combined with the material property database to realize the automatic matching and dynamic optimization of parameters of different substrate-solder combination, thus solving the problem of low efficiency of traditional trial and error method.

[0083] 2. Core Methodology and Mechanism

[0084] (1) Energy field timing coordination: Laser preheating ensures full melting of the solder, ultrasonic delay of 5ms start-up avoids solid-state impact, and IMC growth is quantitatively controlled by energy coupling coefficient K;

[0085] (2) Material adaptation strategy: Increase laser power to address the high reflectivity of Al, and reduce ultrasonic power to address the high reactivity of Ni. Parameter differentiation matching is achieved through a database.

[0086] (3) Weak vibration during solidification: After the laser is turned off, maintain ultrasonic vibration at 50-60% power to suppress IMC grain ripening and refine the microstructure to 1-2μm by utilizing the acoustic flow effect.

[0087] 3. Mathematical Model of Composite Energy Field Coupling

[0088] (1) Heat source model: The laser heat flux density follows a Gaussian distribution, and the corresponding heat flux density distribution is shown in the formula:

[0089]

[0090] In the formula, Q laser The laser power density at any point (x, y) in space at time t; Q1 is the total laser power (W); R1 is the spot radius (defined as the point where the intensity drops to 5% of the peak); (x0, y0) are the coordinates of the spot center; (x, y) are the coordinates of any point in space, used to calculate the laser energy distribution at that point; H t This is the time step function.

[0091] (2) Fluid dynamics model of ultrasonic acoustic flow effect: Ultrasonic vibration assists the flow of molten tin through acoustic flow and cavitation effects, mainly affecting the dynamics of the molten pool (wetting, convection mixing, interfacial reaction). Ultrasonic vibration drives the flow of the molten pool through the sound pressure gradient, which satisfies the Navier-Stokes equations. The power source is provided by the ultrasonic stress field.

[0092]

[0093] u ultra =A·2πfcos(2πft)·n;

[0094] In the formula, p is the fluid pressure, describing the pressure distribution within the molten pool; u is the dynamic viscosity of liquid tin, characterizing the fluid's ability to resist shear deformation (the larger the value, the worse the fluidity); F ultra Ultrasonic volume force, the driving force generated by ultrasonic vibration on the molten pool; u ultra This is the ultrasonic vibration velocity vector.

[0095] (3) Composite energy field heat transfer model: Considering the forced convection caused by ultrasonic flow in the molten pool, the transient heat conduction equation is:

[0096]

[0097] In the formula, The term represents the convective heat transfer caused by ultrasonic flow, where u is the molten pool velocity (driven by ultrasonic vibration), L is the latent heat of fusion of the solder, and f is the convective heat transfer term caused by ultrasonic flow. s This represents the solid fraction (describing the solid-liquid transition).

[0098] (4) Interface reaction model: Ultrasonic promotion of the interface reaction between solder and substrate, the growth kinetic equation of intermetallic compound (IMC) is as follows:

[0099]

[0100] In the formula, δ is the IMC layer thickness; K0 is the frequency factor, which is related to the intrinsic rate of the interfacial reaction; Q actα is the reaction activation energy, the energy barrier required for interfacial atomic diffusion or chemical reaction (the smaller the value, the easier the reaction); R is the gas constant, a fundamental thermodynamic constant; T is the absolute temperature, which affects the atomic diffusion rate (the higher the temperature, the faster the reaction); α is the ultrasonic enhancement coefficient, characterizing the promoting effect of ultrasonic amplitude A and frequency f on interfacial reaction (positively correlated).

[0101] (5) Wettability and Spreading Model: Ultrasonic pressure reduces surface tension and promotes spreading.

[0102] γ = γ0 - αp;

[0103]

[0104] In addition, the soldering methods using the microscale soldering device with ultrasonic-laser combined energy field synergistic control of the present invention mainly include the following three types:

[0105] Soldering Method 1: Cu substrate, Sn-Ni solder (solder joint size 200μm)

[0106] (1) Interface pretreatment: Cu substrate was etched by Ar / O2 plasma (power 80W, time 40s), surface roughness Ra=0.3μm, contact angle 25°; calibrated laser spot 100μm, ultrasonic 30° angle, action point deviation 15μm.

[0107] (2) Parameter initialization: laser power 200W, ultrasonic frequency 30kHz, power 100W, wire feeding rate 1mm / s, energy coupling coefficient K=0.067 (corrected to 0.045).

[0108] (3) Welding process:

[0109] 1) Preheating stage (0-5ms): Laser heating to 230℃ (melting point 183℃+47℃), heating rate 60℃ / ms;

[0110] 2) Recombination stage (5-50ms): Ultrasonic initiation, holographic imaging shows a molten pool spreading rate of 0.15mm / ms; when the temperature rises to 250℃, the laser power drops to 180W, maintaining K=0.05;

[0111] 3) Solidification stage (50-100ms): Laser is turned off, ultrasonic power is reduced to 50W, and acoustic impedance monitoring efficiency is 88%.

[0112] (4) Performance testing:

[0113] Macroscopic morphology: Solder joint diameter 205μm, uniformity deviation 2.5%, no bridging;

[0114] Microstructure: IMC layer thickness 2.2 μm, Cu6Sn5 grain size 1.5 μm, deviation 8%;

[0115] Mechanical properties: Shear strength 75MPa, fracture surface exhibits ductile characteristics (dimple depth 3-5μm);

[0116] Defect rate: 3% (mainly micropores, diameter <2μm).

[0117] Soldering Method 2: Al substrate, Sn-Ag-Cu solder (solder joint size 150μm)

[0118] (1) Interface pretreatment: Al substrate anodizing (15V, 10min), surface contact angle 20°; laser spot 150μm, ultrasonic 45° angle, action point deviation 10μm.

[0119] (2) Parameter initialization: laser power 250W (compensating for high reflectivity), ultrasonic frequency 25kHz, power 120W, wire feeding rate 1.25mm / s, K=0.033.

[0120] (3) Welding process:

[0121] 1) Preheating stage (0-4ms): Laser heating to 240℃ (melting point 217℃+23℃), heating rate 70℃ / ms;

[0122] 2) Composite stage (4-45ms): Ultrasonic initiation, monitoring shows a spreading rate of 0.12mm / ms; due to the fast thermal conductivity of Al, the laser power is dynamically maintained at 240-260W;

[0123] 3) Coagulation stage (45-95ms): The ultrasonic power is reduced to 60W to inhibit the coarsening of IMC tissue.

[0124] (4) Performance testing:

[0125] 1) The IMC layer is 1.8 μm thick, and the Al-Sn intermetallic compounds are uniformly distributed;

[0126] 2) Shear strength 72 MPa, electrical conductivity increased by 12%;

[0127] 3) The defect rate is 1.5%, and there are no obvious cracks.

[0128] Soldering Method 3: Ni substrate, Sn-Ni solder (solder joint size 200μm)

[0129] (1) Interface pretreatment: Ni substrate electroless nickel plating (5μm), Ra=0.2μm; laser spot 60μm, ultrasonic 60° angle, point of action deviation 8μm.

[0130] (2) Parameter initialization: laser power 120W, ultrasonic frequency 38kHz, power 60W, wire feed rate 0.6mm / s, K=0.027.

[0131] (3) Welding process:

[0132] 1) Preheating stage (0-3ms): Laser heating to 200℃ (melting point 183℃+17℃), heating rate 50℃ / ms;

[0133] 2) Recombination stage (3-35ms): Ultrasonic initiation. Due to the high reactivity of Ni, the ultrasonic power is controlled at 50-60W to avoid excessive growth of IMC.

[0134] 3) Coagulation stage (35-85ms): The ultrasonic power is reduced to 30W to promote tissue homogenization.

[0135] (4) Performance testing:

[0136] 1) The IMC layer is 1.5 μm thick, and the Ni3Sn4 grains are fine and uniform;

[0137] 2) Shear strength 80MPa, strength retention rate 90% after 1000 cycles at high temperature (200℃);

[0138] 3) The defect rate is 2%, which meets the requirements for high-temperature service.

[0139] This invention features a rationally designed structure. Addressing the problems of coarse intermetallic compound (IMC) microstructure, high defect rate, and poor material adaptability in existing welding technologies, this invention constructs a closed-loop control mechanism for "thermal-acoustic-mass" multi-parameter control through the adjustable coupling of a laser thermal field and an ultrasonic vibration energy field, combined with a multi-physics field monitoring and intelligent control system. The soldering device includes a collaborative energy output module, a multi-physics field monitoring module, and an intelligent control system, adaptable to Cu, Al, Ni substrates, and solder systems such as Sn-Ni and Sn-Ag-Cu. The soldering method achieves refined IMC microstructure (1-3 μm) and precise defect rate suppression (≤5%) through energy field timing matching, dynamic parameter optimization, and weak vibration coordination during solidification. The microscale soldering device and method using ultrasonic-laser composite energy field synergistic control achieves a solder joint shear strength ≥70 MPa and an increase in conductivity of over 15%, suitable for microscale solder joint (50-500 μm) welding of high-density integrated circuits, with the following significant advantages:

[0140] 1. High energy field coupling efficiency: The adjustable angle design and energy matching algorithm improve the energy transfer efficiency from 70% to over 90%, and reduce the heat-affected zone to within 50μm, avoiding thermal damage to components;

[0141] 2. Strong material adaptability: Through differentiated parameter matching and database support, high-quality welding of Cu, Al, and Ni substrates with Sn-based solder can be achieved without replacing core components;

[0142] 3. Controllable microstructure and properties: The IMC layer thickness is stabilized at 1-3μm by adjusting the energy coupling coefficient K, the grain size deviation is <10%, and the shear strength is increased by 40% (≥70MPa);

[0143] 4. Significantly reduced defect rate: The combination of weak vibration during solidification and closed-loop control reduces the total defect rate, such as poor solder joints and microcracks, to below 5%, while increasing electrical conductivity by 15%, meeting the reliability requirements of high-end packaging.

[0144] This invention has significant technological innovation and industrial application value.

[0145] The above embodiments, which describe the specific features of the present invention, are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-essential improvements and adjustments made to the present invention by those skilled in the art based on the above description of the invention fall within the scope of protection of the present invention.

Claims

1. A microscale soldering device with synergistic control of ultrasonic-laser composite energy field, characterized in that: It includes a collaborative energy output module, a multi-physics field monitoring module, a wire feeding module, an intelligent control system, and a motion platform. The motion platform is provided with a workpiece to be welded, which includes an IMC solder joint and a substrate. The collaborative energy output module includes a laser unit, an ultrasonic vibration unit, and an adjustable focusing lens. The laser unit uses a fiber laser, and the spot diameter can be continuously adjusted from 50 to 200 μm through the adjustable focusing lens. The ultrasonic vibration unit includes an ultrasonic generator, which is located directly below the motion platform. The multiphysics monitoring module includes an infrared thermometer, a high-speed holographic imaging system, and an acoustic impedance sensor. The infrared thermometer collects the temperature field distribution in the welding area; the high-speed holographic imaging system records the flow of the solder pool and the dynamics of IMC nucleation; and the acoustic impedance sensor monitors the ultrasonic energy transmission efficiency. The intelligent control system is electrically connected to the multiphysics monitoring module, and the intelligent control system has a built-in multiphysics coupling prediction model based on LSTM neural network, which dynamically adjusts the laser power, ultrasonic frequency and wire feeding rate according to real-time monitoring data.

2. The microscale soldering device with synergistic control of ultrasonic-laser composite energy field according to claim 1, characterized in that: The intelligent control system includes a process parameter self-learning module, which optimizes the prediction model based on welding data and controls the IMC thickness prediction error to within 8%.

3. The microscale soldering device with synergistic control of ultrasonic-laser composite energy field according to claim 2, characterized in that: The intelligent control system also includes a storage device for storing the optimal parameter mapping relationship between different substrates and solders.

4. The microscale soldering device with synergistic control of ultrasonic-laser composite energy field according to claim 3, characterized in that: The laser unit has an output power of 50-100W, and the angle between the laser beam and the substrate normal is adjustable within the range of 0°-15° via a two-dimensional rotary table; the ultrasonic generator has an ultrasonic frequency of 20-40kHz, an amplitude of 5-20μm, and a power of 50-150W; the infrared thermometer has a resolution of 1024×768, a temperature measurement range of 100-500℃, and a sampling rate of 1kHz; the high-speed holographic imaging system has a frame rate of 5000fps and a spatial resolution of 1μm; the acoustic impedance sensor has a sampling rate of 10MHz and monitors ultrasonic energy transmission efficiency ≥90%.

5. The microscale soldering device with synergistic control of ultrasonic-laser composite energy field according to claim 4, characterized in that: The multiphysics coupling prediction model dynamically adjusts the laser power (±5W accuracy), ultrasonic frequency (±0.5kHz accuracy), and wire feed rate (0.5-1.5mm / s) based on real-time monitoring data.

6. A soldering method for a microscale soldering device with synergistic modulation of ultrasonic-laser composite energy field as described in any one of claims 1-5, characterized in that: Includes the following steps: S1. Interface preprocessing: (1) The Cu substrate was etched using Ar / O plasma with a volume ratio of 9:1, a power of 50-100W, a time of 30-60s, and a surface roughness Ra≤0.5μm; 2 (2) The Al substrate is anodized at 15V for 10min to form a hydrophilic oxide layer; (3) The Ni substrate is electroless nickel plated with a thickness of 5 μm to reduce the interfacial reactivity; The laser focus, ultrasonic action point, and wire feeding point are calibrated using a spatial coupling mechanism, with a deviation ≤20μm. S2. Parameter Initialization: Based on the weld joint size D and material combination, the intelligent control system database is invoked. (1) When D≤100μm(Ni / Sn-Ni): laser power 100-150W, ultrasonic frequency 35-40kHz, power 50-80W; (2) When 100μm<D≤500μm (Cu / Sn-Ni): laser power 150-250W, ultrasonic frequency 25-35kHz, power 80-120W; (3) When Al / Sn-Ag-Cu: laser power 200-300W (compensating for high reflectivity), ultrasonic frequency 20-30kHz, power 100-150W; The wire feed rate V is linearly related to the laser power, V = 0.005 × P1, unit: mm / s; S3. Sequential Co-welding: (1) Preheating stage (0-5ms): Laser acts alone to heat to the melting point of the brazing filler metal and float up 30-50℃, with the heating rate controlled at 50-80℃ / ms; (2) Composite stage (5-50ms): Ultrasonic vibration starts and wire is fed synchronously; the intelligent system adjusts parameters according to monitoring data: if the molten pool spreading rate is <0.1mm / ms, the ultrasonic power is increased by 5-10W; if the temperature exceeds the melting point by 50℃, the laser power is reduced by 10-15W. (3) Solidification stage (50-100ms): Stop wire feeding and turn off the laser, reduce ultrasonic power to 50-60%, maintain for 50-100ms to promote IMC homogenization; S4. Quality Inspection: Internal defects are detected using a laser scanning acoustic microscope (5μm resolution), and shear strength is tested using a micro tensile testing machine (±0.1MPa accuracy). If the quality does not meet the standard, return to the S2 optimization parameters.

7. The soldering method of the microscale soldering device with ultrasonic-laser composite energy field synergistic control according to claim 6, characterized in that: In step S3, the energy coupling coefficient K=P is defined. l / (Pᵤ×f), when K∈[0.02-0.05] W・kHz / W, the IMC layer thickness is stable at 1-3 μm: (1) The optimal K for the Cu / Sn-Ni system is 0.04-0.05; (2) The optimal K for the Al / Sn-Ag-Cu system is 0.03-0.04; (3) The optimal K for the Ni / Sn-Ni system is 0.02-0.

03.

8. The soldering method of the microscale soldering device with ultrasonic-laser composite energy field synergistic control according to claim 7, characterized in that: In the composite stage of step S3, the LSTM model is input with temperature gradient, sound pressure amplitude and molten pool velocity, and outputs IMC thickness and defect probability. The model is trained with 500 sets of experimental data and the prediction error is ≤8%.

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