CSP器件无铅焊点可靠性的有限元分析
Finite element analysis on reliability of lead-free soldered joints for CSP device
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摘要: 采用有限元方法对芯片尺寸封装(CSP)器件焊点可靠性进行模拟分析.运用Anand本构模型描述Sn3.0Ag0.5Cu无铅焊点材料的粘塑性特性,研究了焊点的力学行为.结果表明,CSP焊点最大应力区为拐角芯片所下压的焊点上表面处,对焊点应力最大节点的时间历程后处理结果显示,温度循环载荷下,焊点应力呈周期性变化,并有明显的应力松弛和积累迭加效应.对三种常用不同焊点高度尺寸下的焊点应力进行对比分析,发现三种尺寸中,0.35 mm×0.18 mm焊点的可靠性最好.还模拟对比了芯片厚度不同对焊点可靠性的影响,结果显示芯片厚度对焊点可靠性影响较小.Abstract: Finite element method was employed to analyze the reliability of soldered joint in a CSP device.Anand model was used to establish the constitutive equation of Sn3.0Ag0.5Cu solder, the stress behavior of soldered joint was studied.The results indicate that the maximal stress is located at the upper surface of the soldered joint which is under the outermost of chip.The phenomenon of stress relaxation and accumulated enhancement could be observed obviously from the curves of stress and temperature with time cycle.Reliability of soldered joints with three usually-used heights are compared, and the results shows that the 0.35 mm×0.18 mm one has the best reliability.Moreover, the influence of chip thickness on the reliability of soldered joints are investigated in the last part, the simulation result indicates that the influence is little.
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Keywords:
- chip scale package /
- lead-free soldered joint /
- reliability /
- finite element analysis
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