球栅阵列无铅焊点随机振动失效研究

摘要

通过非接触式激光全息激振方法对试件(电路板组件)进行试验模态分析,了解其动态特性;以其第一阶固有频率作为中心频率,分别进行了三种不同加速度功率谱密度幅值的窄带随机振动疲劳试验,并对失效焊点进行金相剖面分析,探究球栅阵列(BGA)无铅焊点在随机振动载荷下的失效机理.结果表明,三种加速度功率谱密度幅值的随机振动试验中BGA无铅焊点的失效机理不尽相同,随着功率谱密度幅值增加,焊点失效位置由靠近电路板(PCB)一侧向靠近封装一侧转变,分别是靠近PCB一侧的焊球体,焊点颈部以及靠近封装一侧的Ni/金属间化合物(IMC)界面处,相应的失效模式由疲劳断裂转为脆性断裂.%Non-contact laser holography exciting approach was adopted to conduct experimental modal analysis of a printed circuit board (PCB) assembly and find its dynamic characteristics.Then, its first-order natural frequency was used as the central frequency, and three different acceleration power spectral density (PSD) amplitudes of narrow-band random vibration fatigue tests were respectively carried out.Subsequently, failed BGA solder joints were cross-sectioned and metallurgical analysis was done to investigate failure mechanisms of BGA lead-free solder joints under random vibration loading.The results showed that failure mechanisms of BGA lead-free solder joint vary as the PSD amplitude increases; solder joint failure locations changes from the solder bump body of the PCB side to the solder ball neck, finally to the Ni / intermetallic compound ( IMC ) interface of the package side; the corresponding failure modes change from fatigue fracture to brittle fracture.