低银无铅焊料球栅阵列焊点的热可靠性研究

发布时间：2018-02-16 03:44

  本文关键词： 无铅焊料 低银SAC 球栅阵列 金属间化合物 热可靠性　出处：《重庆理工大学》2016年硕士论文　论文类型：学位论文

【摘要】：随着便携式电子产品的普及,焊点尺寸逐渐减小。同时由于含Pb焊料被限制使用,无铅焊点中高Sn含量和高互连温度引起界面金属间化合物的生长,主导着电子产品封装的可靠性。在无铅焊料中,低银SAC无铅焊料具有韧性好、抗跌落和抗热冲击性好、原材料成本低等优点,受到国内外学者的关注,因此其可靠性的系统研究对低银无铅焊料的研制及其应用具有重要的科学意义。本文通过添加微量元素来改善低银Sn-0.45Ag-0.68Cu无铅焊料的性能,研究了低银Sn-0.45Ag-0.68Cu/Cu焊点在热循环、冷热冲击和热时效下界面IMC的生长演变规律,综合分析焊点可靠性和失效模式,结果表明:(1)低银SAC/CuBGA焊点在热冲击和热循环后,界面(Cu,Ni)_6Sn_5 IMC层不断增厚,其形貌由细长扇贝状逐渐变得平滑,且疏松的IMC组织变得更加致密;同时,焊点的剪切强度和拉伸强度均呈不断下降的趋势,剪切和拉伸断口都为韧性断裂模式。与SAC305/Cu焊点相比,低银Sn-0.45Ag-0.68Cu/Cu焊点在热冲击条件下具有与其相媲美的可靠性。(2)热时效后低银SAC/CuBGA焊点界面(Cu,Ni)_6Sn_5 IMC层不断增厚,其形貌逐渐由波浪状向锯齿状转变,并趋于平滑。在100℃、125℃和150℃下时效后BGA焊点界面IMC层的生长系数分别为5.88×10-19m~2/s、10.68×10-19m~2/s和39.34×10-19m~2/s,其生长激活能为49.41kJ/mol。随着时效时间的增加,剪切强度和拉伸强度整体呈下降趋势,且在高温下焊点的力学性能下降的较快。(3)综合分析三种热可靠性,热冲击对低银SAC/Cu焊点剪切强度、抗拉强度以及界面(Cu,Ni)_6Sn_5 IMC层生长速率的影响最大,其后依次为热循环和热时效。对比分析了Co-P镀层焊盘与Cu焊盘对BGA焊点界面IMC生长的影响,评价了在100℃和150℃热时效后低银Sn-0.45Ag-0.68Cu/Co-P BGA焊点的可靠性,并综合分析了焊点的失效模式,结果表明,250℃下Co-15%P镀层对低银Sn-0.45Ag-0.68Cu焊料具有良好的润湿性能。热时效后低银SAC/Co-P BGA焊点界面CoSn_3 IMC层的厚度总体呈增加的趋势,且焊料内(Cu,Co,Ni)6Sn5 IMC不断向界面聚集长大引起焊点组织粗化。长时间时效后剪切和拉伸断口的失效模式均为韧性+脆性混合模式,与低银SAC/Cu焊点相比,低银SAC/Co-P焊点在长期使用可靠性方面仍具有较大的优势。
[Abstract]:With the popularization of portable electronic products, the size of solder joint decreases gradually. At the same time, the high Sn content and high interconnect temperature in lead-free solder lead to the growth of intermetallic compounds in the interface due to the limited use of lead-containing solders. In the lead-free solder, low silver SAC lead-free solder has the advantages of good toughness, good drop resistance and thermal impact resistance, low cost of raw materials and so on, which has attracted the attention of scholars at home and abroad. Therefore, the systematic study of its reliability is of great scientific significance for the development and application of low silver lead-free solders. In this paper, the properties of low silver Sn-0.45Ag-0.68Cu lead-free solders are improved by adding trace elements, and the thermal cycling of low silver Sn-0.45Ag-0.68Cu solder joints is studied. The growth and evolution law of interface IMC under cold and thermal shock and thermal aging, and the reliability and failure mode of solder joint are analyzed. The results show that the interface of low silver SAC/CuBGA solder joint increases continuously after thermal shock and thermal cycling. The morphology of the alloy gradually became smooth from the thin scallop shape, and the loose IMC microstructure became denser, and the shear and tensile strength of the solder joint decreased continuously. The shear and tensile fracture are ductile fracture modes. Compared with SAC305/Cu solder joints, low silver Sn-0.45Ag-0.68Cu/Cu solder joints have comparable reliability under thermal shock. After aging at 100 鈩，

本文编号：1514581