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题名	温度冲击条件下PCB无铅焊点可靠性研究
作者	毛书勤
学位类别	博士
答辩日期	2015-05
授予单位	中国科学院大学
导师	郭立红
关键词	无铅焊点 剪切力 疲劳状态 锡晶须 可靠性
其他题名	Research on reliability of PCB lead-free solder joints in the condition of thermal shock
学位专业	机械电子工程
中文摘要	伴随着ROHS指令的生效，电子电气产品的无铅化组装技术被迅速推开。时至今日，无铅化的推广已经有很长一段时间，不可避免的在应用过程中出现了很多问题。主要包括：高温带来的问题、立碑问题、铅污染问题、晶须生长问题以及无铅焊点的可靠性问题等等。这些问题对于可靠性要求甚高的军品研制单位是必须面对并加以解决的。本文以PCB无铅焊点可靠性研究为切入点，借助焊点剪切力测试等手段，以多周期温度冲击试验为加速条件，开展了如下创新性研究工作： （1）针对传统的退化试验理论与试验方法在评估诸如PCB焊点等产品可靠性过程中遇到的困难，提出了基于比较的加速退化试验数据建模及分析方法。该方法不以估计产品在正常使用条件下的工作寿命为目的，而是通过比较两种产品的伪失效寿命，进而评估产品的可靠性。该方法特别适用于那些有长时间成熟的使用经验，性能退化量难以重复测量，同时难以模拟其实际工作状态的产品。经试验证明该方法可用于评价无铅焊点的可靠性，为无铅焊点可靠性评价开辟了一条新的路径。 （2）针对无铅焊点焊接条件可选范围大，焊接条件对于焊点性能影响不甚明晰的现状，开展了焊接条件对焊点性能影响评价研究工作。针对不同焊端镀层、不同焊接钎料、不同PCB焊盘镀层以及不同焊接方法条件下焊点的剪切力学性能进行测试，为无铅钎料力学性能评价、无铅钎料对于特定PCB焊盘的润湿性能评价、焊接方式对于焊点性能影响评价提供了数据参考。 （3）针对焊点的疲劳状态监测缺乏有效手段，现有监测手段如阻值法存在阻值波动大、监视记录系统复杂等缺点，提出基于剪切力水平评估的温度冲击条件下焊点疲劳状态监测方法。通过进行1500个周期的温度冲击试验，设置6个剪切力数据采样点，得到了有铅焊点和无铅焊点疲劳状态的数据拟合曲线。采用比较研究方法，以有铅焊点为参照，对比无铅焊点的疲劳状态变化情况，研究表明：在有限周期内，无铅焊点的伪失效寿命大于有铅焊点。无铅焊点的力学可靠性优于有铅焊点。 （4）针对无铅焊点的晶须生长问题，提出利用DBSF6101三防保护剂采用敷形涂覆的办法对锡晶须生长进行抑制的方法。以1500周期温度冲击试验做为加速条件，参照观察有铅焊点表面的变化情况，观察无铅焊点的晶须生长情况。将敷形涂敷做为晶须生长的抑制手段，观察其对于晶须生长的抑制作用。试验结果显示：在文中的加速试验应力作用下，无铅焊点表面确实存在锡晶须生长现象，采用敷形涂覆DBSF6101材料的方法能有效抑制锡晶须生长。
英文摘要	Along with the ROHS directive, the lead-free assembly technology to electronic and electrical products is quickly extended. Today, the promotion of lead-free for a long time, inevitably, there are a lot of problems in the application process. Mainly including: problems caused by high temperature, problems of tomb, problems of lead pollution, problems of tin whisker growth and problems of lead-free solder joint reliability etc.. These problems must be faced and solved to military equipment enterprises. Based on the research of the reliability of PCB lead-free solder joints, by means of the shear force test, in the condition of multi-thermal shock, mainly research innovative work is listed: (1) Traditionally, it is difficult to estimate reliability of products, as solder points of PCB. One method based on comparison of accelerated degradation test data modeling and analysis is presented. This method is not to estimate the work life of the product under normal use conditions, but to compare pseudo failure life in the same degradation mechanism of action. The method is particularly suitable for those who have the experience of long time use mature, and it’s difficult to measure repeatedly, to simulate actual working status. The experiments prove that the method can be used to evaluate the reliability of lead-free solder joints. And it’s a new path to evaluate the reliability of lead-free solder joints. (2) There are many options for lead-free solder joint welding condition. And welding conditions for solder joint performance is not clear. The research on welding condition to impact the performance of solder joints is carried out. Shearing force statistical data of welding solder joints is gotten, through measuring resistance at different welding end coatings, different welding solder, different PCB pad coatings and different method. Through comparative study, influence of welding condition on solder joints is intuitively reflected. It provides data for reference on evaluation for lead-free solder of mechanical performance. (3) There is no effective method to monitor the fatigue state of solder joints. The existing monitoring methods have shortcomings. Such as resistance method its value fluctuates and its recording system is complex, etc.. Research on PCB lead-free solder joints fatigue properties in the condition of thermal shock is carried out. Through the thermal shock of 1500 cycles test, setting 6 shear stress data sampling points, data fitting curves with lead solder and lead-free solder joint fatigue state are obtained. By the comparative study, comparing lead solder joints to lead-free solder joints, the research shows that: in a limited period, the acceleration pseudo failure lifetime of lead-free solder joints are longer than that of lead solder joints. The mechanical reliability of lead-free solder joints is better than lead solder joints. (4) For the problem of tin whisker to lead-free solder joints, DBSF6101 protective agent is used to suppress growth of tin whisker. In the 1500 cycles of temperature shock test for accelerated condition, there are not any tin whiskers observed on the surface of lead solder joints. But growth of whiskers is observed on lead-free solder joints. The conclusion: In the condition above, the method of conformal coating material of DBSF6101 can inhibit the growth of tin whisker effectively.
公开日期	2015-12-24
内容类型	学位论文
源URL	[http://ir.ciomp.ac.cn/handle/181722/48882]
专题	长春光学精密机械与物理研究所_中科院长春光机所知识产出
推荐引用方式 GB/T 7714	毛书勤. 温度冲击条件下PCB无铅焊点可靠性研究[D]. 中国科学院大学. 2015.

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