金属材料激光微焊接研究进展(特邀)

Research Progress in Laser Micro⁃welding of Metal Materials(Invited)

设备器件精密化、微型化是工业发展的重要趋势。在航空航天、动力电池、消费电子、生物医疗等应用领域中,零部件的日益微型化对微加工工艺提出了更高的要求。金属材料微焊接是微加工领域的重要需求之一,而激光具有能量密度高、热输入精确可控、焊接变形小等特点,是金属材料微焊接的重要技术手段。对金属材料激光微焊接技术展开了探讨,明确了其内涵,阐明了微尺度效应的影响,并总结了激光微焊接常见的缺陷及其质量控制方法,介绍了同种金属材料和异种金属材料激光微焊接的重要应用前景。最后,指出了金属材料激光微焊接技术存在的问题,并展望了未来的发展方向。

Significance In recent years,notable progress has been made in the development of equipment components aimed at precision and miniaturization.These miniature components typically exhibit complex geometries.They are composed of diverse materials.Further miniaturization of these components has led to an increased demand for precision welding.Consequently,the assembly of small parts and the packaging of devices require increasingly high levels of connection accuracy and quality control.High-quality micro-welding technologies for metallic materials have important applications in aerospace,power batteries,biomedicine,and other fields.For instance,micro electro mechanical systems(MEMS),characterized by feature sizes ranging from 1μm to 1 mm,are commonly packaged using micro-welding technology.Moreover,power battery electrode foils,with thicknesses as low as 6‒12μm,require precise connections for current export.Furthermore,the assembly of components and metal shell sealing in implantable biomedical devices rely heavily on micro-welding technology.Common micro-welding techniques include resistance micro spot welding,ultrasonic micro-welding,micro tungsten inert gas(TIG)welding,and laser micro-welding.Compared with conventional micro-welding methods,laser micro-welding offers several advantages,including a small focusing spot size,precise heat input control capability,high welding speed,and compatibility with various weldable materials.Progress This study investigates the laser micro-welding technology of metal materials,providing a comprehensive analysis of its significance,microscale effects,welding modes,laser selection,and defect and quality control measures.It is difficult to reach a consensus on a precise definition of laser micro-welding.The connotations of laser micro-welding are comprehensively summarized based on previously reported studies.Strictly speaking,laser micro-welding pertains to a laser welding process where at least one feature size of the connected material or weld is less than 100μm.Laser micro-welding involves two welding modes:conduction and penetration welding.In laser micro-welding,oxidation promotes fluctuations in the penetration-welding process,resulting in a transient phase.Subsequently,the influence of microscale effects is introduced.When workpiece dimensions are reduced to the micron scale,typical microscale effects occur.The physical characteristics observed during laser micro-welding,such as heat transfer and molten pool flow,differ from those observed during macro-welding(Fig.2).Based on microscale effects,the defects and quality control measures in laser micro-welding are summarized according to the process parameters.Welding defects such as lack of penetration,burn-through,spatter,humping,porosity,and cracking can occur during the laser micro-welding process,and optimization of the welding process parameters is an important means of controlling weld formation and welding defects.These parameters include the laser wavelength,laser power,spot diameter of the laser,pulse laser parameters,welding speed,and scanning path.Furthermore,the applications of laser micro-welding to both similar and dissimilar metal materials are reviewed.Laser microwelding is used to join precision components in the electronics,automotive,aerospace,and medical industries(Fig.12).Notable applications include pressure sensors,bipolar plates for fuel cells,aerospace engine blades,electronic component pins,copper-printed circuit boards,satellite collimator components,cardiac pacemakers,and lithium-ion battery tabs.Finally,the challenges and future development directions of laser micro-welding technology for metallic materials are summarized,including the welding mechanism of metal and non-metallic materials,new process technology,and laser micro-welding systems.Conclusions and Prospects The characteristics of laser micro-welding are complex owing to microscale effects.Although laser micro-welding has been widely used for connecting metal materials,some challenges remain.First,there is a burgeoning demand for the joining of dissimilar materials,including the micro-welding of dissimilar metals and metal/non-metallic materials.Dissimilar materials with different physical properties pose significant challenges in welding.Second,increasing the welding speed is important for improving the production rate.However,humping occurs at high welding speeds.To address this,process innovation and the recombination of multiple energy fields are required to further increase the critical speed of humping by controlling the flow characteristics of the molten pool and the solidification process during micro-welding.This is essential for improving the production rates and ensuring the product yield in high-speed welding.Finally,the development of intelligent laser micro-welding systems is a key future trend.The use of an intelligent laser micro-welding system has the potential to improve weld quality and welding efficiency.