【作者】 黎俊；

【导师】 吴丰顺；

【作者基本信息】 华中科技大学 ， 材料加工工程， 2009， 硕士

【摘要】 随着电子产品微型化进程的加快,焊点互连间距也随之减小。而由于焊点界面金属间化合物(IMC: Intermetallic Compound)的本征脆性,随着焊点互连高度的降低,焊点的可靠性会受到直接影响。因此,探讨互连高度对于焊点可靠性的影响十分必要。本课题基于此目的,根据国家自然科学基金面上项目《微小互连高度下焊点的界面反应及可靠性研究》,探讨互连间距在100μm、50μm、20μm和10μm的微互连焊点的界面反应及可靠性。本文采用精密控制焊点互连高度(SOH: stand-off height)的装置获得100μm、50μm、20μm和10μm四种不同互连高度的焊点,同时对焊点进行老化试验及拉伸试验,并采用环境扫描电镜研究互连高度变化对焊点中界面IMC的组织、形貌、焊料的比例等的影响,分析其对焊点抗拉强度及可靠性的影响。研究结果表明,随着焊点互连高度的降低,界面IMC的厚度呈减小趋势,IMC占焊料的比例随之增加;随着老化时间的增加,界面IMC的厚度及其占焊料的比例增加,老化500小时后,互连间距为10μm的焊点中IMC占焊料的比例更是达到100%。随着焊点互连间距的减小,焊点所受的最大拉力随之减小,抗拉强度也随之减小。在焊点互连间距为100μm、50μm和20μm时,随着老化时间的增加,焊点所受的最大拉力基本不变,抗拉强度变化也不大,当焊点互连间距为10μm时,焊点的抗拉强度随着老化时间的增长呈递减趋势。随着老化时间的增加,互连高度的减小,焊点的断裂也从一侧IMC与焊料的接触面断裂逐渐转为从两侧的IMC与焊料的接触面断裂,最终转为从一侧的Cu6Sn5与Cu3Sn的接触面处断裂。更多还原

【Abstract】 Miniaturization of electronic products accelerates the process of the stand-off height (SOH) of solder joints decreasing. But due to IMCs (Intermetallic compound) intrinsic brittleness, thicker interfacial IMCs will degrade the reliability of the solder joint. So studying the interfacial reaction and the reliability of the solder joint is very important. This project comes from the National Natural Science Foundation of China, mainly investigate the effect of different SOH (100μm, 50μm, 20μm and 10μm) on the interfacial reaction and reliability.In the paper, Sn-4.8Bi-2Ag alloy was used as the lead-free solder. A high-precision device was used to control the SOH of the solder joint between two copper needles. The copper needles were connected by the reflow process. Then the specimens were aged at 150℃for different time. The effect of SOH on the reliability, which reflects by the changes of the intermetallic compound (IMC), such as the organization, morphology and the proportion of interfacial IMC layer were investigated. And the effect of the aging time (100h, 300h, 500h) on the reliability under a fixed SOH was studied too. Tensile test was also used to study the tensile strength of the solder joints.It is found that with the decreasing of the SOH, the thickness of interfacial IMC shows a slight decrease trend, and the proportion of interfacial IMC layer increases. When the SOH is 10μm, the proportion of interfacial IMC layer is 100%. With the aging time increasing, the thickness of interfacial IMC gradually increases.It is also found that with the stand-off height of the solder joint decreases, the maximum tensile strength of the solder joints decreases. When the SOH of the solder joints are 100μm, 50μm and 20μm, the tensile strength changes a little as the aging time increases. When the SOH is 10μm, tensile strength decreases with the aging time increases. In additional, with the aging time increasing and the SOH reducing, the fracture of the solder joints is firstly observed at one side of the interface between IMC and solder body, then it tends to appear at two sides of the interface between IMC and solder body, and ultimately it occur at the interface between Cu6Sn5 phase and Cu3Sn phase.更多还原