【作者】 周浩；

【导师】 吴丰顺；

【作者基本信息】 华中科技大学 ， 电子封装， 2024， 硕士

【摘要】 作为激光雷达和飞行时间传感器(ToF)的核心,大功率垂直腔表面发射激光器(VCSEL)的应用前景广阔,传统的固晶材料及工艺无法满足车用电子元器件的服役要求。使用预镀金锡焊料,开发单颗焊接及整板焊接工艺并研究其可靠性,可以为车用VCSEL器件的大规模生产提供理论基础。本文使用预镀金锡焊料氮化铝基板连接VCSEL芯片;重点优化单颗焊接及整板焊接工艺;考察其高温老化和温度冲击可靠性;从显微组织、空洞和裂纹等缺陷、应力应变和能量等载荷的变化中综合分析失效机理。本文的研究内容和结果如下:单因素试验研究了焊接温度、压力、时间对剪切强度的影响,发现剪切强度随焊接温度、压力、时间的增加先增加后降低。正交试验得到优化的单颗焊接工艺参数为310℃、0.30 MPa、4 s,获得剪切强度为124.6 MPa的焊接接头。整板焊接试验与仿真研究得到整板焊接工艺参数为270～350℃、0.30 MPa、4 s,避免了“提前熔化”和“氧化”,获得了一致性好、剪切强度为101.7 MPa的焊接接头。研究了VCSEL器件及焊接接头在高温老化时性能退化、显微组织演变及其与力学性能的联系。100/200℃老化处理后VCSEL器件各项性能符合AEC-Q102标准。力学性能退化机理与金锡焊料显微组织演变有关,金锡焊料显微组织在200℃老化处理时经历层片状AuSn粗化和等轴状AuSn转变两个连续的演变过程,演变过程均符合抛物线型生长规律,由界面扩散机理控制。层片状AuSn粗化时剪切强度先增加后降低,等轴状AuSn转变时剪切强度先缓慢降低后急剧降低。研究了VCSEL器件及焊接接头在温度冲击时性能退化、空洞和显微组织演变,仿真分析了空洞率对接头温度冲击可靠性的影响。-45～125℃温度冲击后VCSEL器件各项性能符合AEC-Q102标准。热性能和力学性能退化机理与焊料层显微组织和空洞及裂纹有关,本文焊接接头无明显空洞,温度冲击时无明显应力集中现象,等效应力、等效塑性应变和塑性应变能都很低,裂纹萌生和扩展的驱动力不足,1000次温度冲击后空洞率不变,且显微组织无明显变化,热性能和力学性能退化程度极低。仿真结果表明:空洞在温度冲击时作为裂纹萌生的起点降低接头疲劳寿命。更多还原

【Abstract】 As the core of LiDAR and time-of-flight sensor(ToF),high-power Vertical Cavity Surface Emitting Laser(VCSEL)devices have broad application prospects.Traditional die bonding material and soldering process cannot meet the growing service requirements of electronic components for vehicles.This thesis used aluminum nitride substrates coated with electroplated Au80Sn20 eutectic solder to develop single-device and full-board soldering process,then studied its reliability,which can provide a theoretical basis for mass production.The investigation focused on advancing single-device and full-board soldering process and examining its reliability under high temperature aging and thermal shocks.The failure mechanism was elucidated through the analysis of the microstructural and the defects such as voids and cracks,as well as the changes in stress,strain,and energy.The research content and results are as follows:The influence of soldering temperature,pressure and time on shear strength was studied by single factor experiment.It was found that shear strength first increases and then decreases with the increase of soldering temperature,pressure and time.The orthogonal experiment showed that the optimal single-device soldering process parameters are 310 °C,0.30 MPa,and 4s,leading to a solder joint with a shear strength of 124.6 MPa.The fullboard soldering experiments and simulation revealed that the soldering process parameters are 270～350 ℃,0.30 MPa,and 4 s,which not only avoids the issues of "pre-melting" and "oxidation",but also results in a consistently solder joint with a shear strength of 101.7 MPa.During high temperature aging,the performance degradation,microstructure evolution as well as its relationship with mechanical performance of VCSEL devices and solder joints were studied.After aging treatment at 100/200 ℃,the performance of VCSEL devices met the AEC-Q102 standard.The degradation of mechanical properties is related to the microstructure evolution of Au80Sn20 solder.The microstructure of Au80Sn20 solder undergoes two continuous evolution processes,which are coarsening of lamellar AuSn and transforming to equiaxed AuSn,during aging treatment.Both of these processes follow the parabolic kinetic behavior and interfacial diffusion control mechanism.When the lamellar microstructure of AuSn is coarsening,the shear strength first increases and then decreases.However,the shear strength first slowly decreases and then sharply decreases when the equiaxed microstructure of AuSn is transforming.The performance degradation and the cavity as well as the microstructure evolution of VCSEL devices and solder joints after thermal shock were studied while the influence of void ratio on the reliability of solder joints after thermal shock was simulated.After thermal shocks at-45～125 ℃,the performance of VCSEL devices met the AEC-Q102 standard.The degradation of mechanical and thermal properties is related to the microstructure evolution and void as well as crack of Au80Sn20 solder layer.Due to the solder joints without Obvious voids and stress concentration during thermal shocks,equivalent stress,equivalent plastic strain as well as plastic strain energy are at low level.The driving force for crack initiation and propagation is insufficient.After 1000 cycles of thermal shocks,the void ratio unchanged,and the degree of thermal and mechanical performance degradation is extremely small.The simulation showed that the voids,which acts as the starting point of crack initiation,reduces the fatigue life of the solder joint.更多还原