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利用SMT全自动回流焊机和高温恒温试验箱,制备出经2次回流焊且不同时效处理时间的Sn-Ag3.0-Cu0.5/Cu焊点试件,对其金属间化合物(IMC)的厚度进行测量,发现其厚度的增长与时效时间的平方根近似成线性关系。采用统一粘塑性Anand本构模型来描述焊点的力学性能,运用有限元计算软件ANSYS对PBGA构件进行热循环模拟,对其在不同IMC厚度下的应力和应变响应进行分析。结果表明,芯片右下方焊点右上角热循环结束后累积的等效塑性应变最大,是整个PBGA构件的关键焊点;随着IMC厚度的增加,关键焊点热循环过程中的等效应力水平不断降低,相应剪切塑性应变范围Δγ不断增大,热疲劳寿命Nf则不断降低;升温和高温保温过程中剪切塑性应变的增加量构成了剪切塑性应变范围Δγ,且不同IMC厚度下升温段剪切塑性应变增加量占Δγ的比例基本维持在95%左右。
The Sn-Ag3.0-Cu0.5 / Cu solder joint specimens with two reflow cycles and different aging treatments were prepared by using SMT automatic reflow soldering machine and high temperature constant temperature chamber. The intermetallic compound (IMC) The thickness was measured and found that the thickness of the growth and the aging time of the square root of a linear approximation. The uniform viscoplastic Anand constitutive model is used to describe the mechanical properties of the solder joints. The thermal cycling simulation of the PBGA components is performed by the finite element software ANSYS. The stress and strain responses of the PBGA under different thickness of IMC are analyzed. The results show that the equivalent equivalent plastic strain accumulated in the upper right corner of the chip at the upper right corner after the end of the thermal cycle is the largest, which is the key solder joint of the whole PBGA. With the increase of IMC thickness, the equivalent stress level , The corresponding plastic shear strain range Δγ increased continuously and the thermal fatigue life Nf decreased continuously. The increase of shear plastic strain in the process of temperature rise and heat preservation constituted the shear plastic strain range Δγ, and the temperature rise at different IMC thickness The percentage of increase in plastic shear strain in segment Δγ is about 95%.