Purpose

The purpose of this study is to investigate the effect of electrical and thermal stresses on the void formation of the Sn3.0Ag0.5Cu (SAC305) lead-free ball grid array (BGA) solder joints and to propose a modified mean-time-to-failure (MTTF) equation when joints are subjected to coupling stress.

Design/methodology/approach

The samples of the BGA package were subjected to a migration test at different currents and temperatures. Voltage variation was recorded for analysis. Scanning electron microscope and electron back-scattered diffraction were applied to achieve the micromorphological observations. Additionally, the experimental and simulation results were combined to fit the modified model parameters.

Findings

Voids appeared at the corner of the cathode. The resistance of the daisy chain increased. Two stages of resistance variation were confirmed. The crystal lattice orientation rotated and became consistent and ordered. Electrical and thermal stresses had an impact on the void formation. As the current density and temperature increased, the void increased. The lifetime of the solder joint decreased as the electrical and thermal stresses increased. A modified MTTF model was proposed and its parameters were confirmed by theoretical derivation and test data fitting.

Originality/value

This study focuses on the effects of coupling stress on the void formation of the SAC305 BGA solder joint. The microstructure and macroscopic performance were studied to identify the effects of different stresses with the use of a variety of analytical methods. The modified MTTF model was constructed for application to SAC305 BGA solder joints. It was found suitable for larger current densities and larger influences of Joule heating and for the welding ball structure with current crowding.

中文翻译：

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电应力和热应力对Sn3.0Ag0.5Cu焊点空洞形成和迁移寿命影响的研究

目的

本研究的目的是研究电应力和热应力对 Sn3.0Ag0.5Cu (SAC305) 无铅球栅阵列 (BGA) 焊点的空洞形成的影响，并提出改进的平均时间到-当关节受到耦合应力时的失效 (MTTF) 方程。

设计/方法/方法

BGA封装的样品在不同的电流和温度下进行了迁移测试。记录电压变化用于分析。应用扫描电子显微镜和电子背散射衍射实现微观形态观察。此外，将实验和模拟结果相结合，以拟合修改后的模型参数。

发现

空洞出现在阴极的角落。菊花链的阻力增加。确认了两个阶段的电阻变化。晶格取向旋转，变得一致有序。电应力和热应力对空隙的形成有影响。随着电流密度和温度的增加，空隙增加。焊点的寿命随着电应力和热应力的增加而降低。提出了一种改进的MTTF模型，并通过理论推导和测试数据拟合确认了其参数。

原创性/价值

本研究重点关注耦合应力对 SAC305 BGA 焊点空洞形成的影响。研究了微观结构和宏观性能，以使用各种分析方法确定不同应力的影响。修改后的 MTTF 模型适用于 SAC305 BGA 焊点。发现它适用于较大的电流密度和较大的焦耳热影响以及具有电流拥挤的焊球结构。