62Sn36Pb2Ag组装焊点长期贮存界面化合物生长动力学及寿命预测

Long-term storage life prediction and growth kinetics of intermetallic compounds in 62Sn36Pb2Ag solder joints

Sn基合金焊接接头是电子产品不可或缺的关键部位,是实现电子元器件功能化的基础,电子整机失效往往由于焊点的损伤所导致,焊点的寿命预测对电子产品的可靠性研究具有重要意义.金属间化合物(IMC)厚度是衡量焊点质量的重要参数,以IMC层厚度为关键性能退化参数,以62Sn36Pb2Ag组装的小型方块平面封装(QFP)器件焊点为研究对象,采用扫描电子显微镜对在94、120和150℃三种温度贮存不同时间后的焊点微观形貌进行表征,测量了IMC层的厚度,基于阿伦尼乌斯方程建立了双侧界面金属间化合物生长动力学模型.并以其作为关键性能退化函数,通过对初始IMC厚度进行正态分布拟合获得失效密度函数,进而获得可靠度函数对焊点的长期贮存失效寿命进行了预测.研究结果有望对长期贮存焊点的寿命预测方式提供新的思路,为62Sn36Pb2Ag钎料的可靠应用提供试验和数据支撑.

Tin-based alloy solder joints are an indispensable key part of electronic products and the basis of realizing the functionalization of electronic components.The failure of an electronic product is often caused by solder joint damage.Life prediction of the solder joint is of great significance for the reliability research of electronic products.The intermetallic compound(IMC)thickness is an important parameter to evaluate the quality of solder joints.This study takes the thickness of the IMC layer and the assembly solder joints of the 62Sn36Pb2Ag QFP device as the key performance degradation parameter and the research object,respectively.After the reflowing process,Cu_(6)Sn_(5) and Cu_(3)Sn IMC phases were observed at the copper lead side,and the(Cu_(x)Ni_(1-x))_(6)Sn_(5) phase was observed at the PCB side.The evolution of interfacial microstructures was observed by a scanning electron microscope(SEM).The thickness of the IMC layer after storage at 94,120,and 150℃for different periods(1,4,9,16,25,36,49 days)was monitored.The growth process of the IMC is controlled by diffusion.As the storage time increases,the thickness of the IMC layer gradually increases.The growth rate of the IMC layer increases with the increase of the storage temperature because of the higher diffusion coefficient.Based on the Arrhenius equation,the growth kinetics model of the IMC with a bilateral interface is established.The failure density function is obtained by fitting the initial IMC thickness with a normal distribution,and the reliability function is then obtained to predict the long-term storage failure life of QFP assembly solder joints.Finally,this work calculates the median life and characteristic life of QFP assembly solder joints to be 16092 years and 17471 years,respectively.These results are expected to provide a new way to predict the life of solder joints stored for a long time and provide experimental and data support for the reliable application of the 62Sn36Pb2Ag solder.