BGA封装含气孔焊点随机振动可靠性的有限元分析

Finite element analysis of random vibration reliability of welding joints with porosity in BGA package

BGA封装器件焊接过程中由于温差、助焊剂等原因不可避免地会产生气孔,对机械冲击和随机振动条件下的可靠性产生影响。然而,物理试验难以获取随机振动中实时应力关系,也难以控制气孔分布及位置。本文基于有限元仿真技术,对不同位置的集中、离散式气孔的影响规律进行了分析。结果证明,相对于无气孔器件,含气孔器件的固有频率变化较小,且中部气孔可以降低最大应力,提高焊球抗冲击能力。但是顶端离散式或底端气孔会大幅提高应力水平,加大冲击失效的可能性。此外,气孔的引入会提高应变值,降低循环疲劳寿命,其中底端气孔、顶端弥散式气孔和中部集中式气孔所致隐患最大,最易失效。

During the welding process of BGA package devices,porosity will inevitably occur due to temperature difference,flux and other reasons,which will affect the reliability under mechanical shock and random vibration conditions.However,it is difficult to obtain the real time stress relationship in random vibration,and it is difficult to control the porosity distribution and location.Based on the finite element simulation technique,the influence laws of concentrated and discrete pores at different positions are analyzed.The results show that compared with the non-porous devices,the natural frequency of the devices with porosity is less changed,and the central porosity can reduce the maximum stress and improve the impact resistance of the welding ball.However,the discrete top or bottom porosity will greatly increase the stress level and increase the possibility of impact failure.In addition,the introduction of porosity will increase the strain value and reduce the cycle fatigue life,among which the bottom porosity,the top dispersed porosity and the central concentrated porosity are the most dangerous and easy to fail.