基于COB技术的SiP模块可靠性分析

Reliability Analysis of the SiP Module Based on COB Technology

针对COB形式的SiP模块,应用有限元分析方法模拟了该模块在湿热环境下的湿气扩散和湿应力分布,以及回流焊过程中的热应力分布,并通过吸湿实验和回流焊实验分析了该模块失效模式。结果表明,在湿热环境下,粘接材料夹在芯片和焊盘中间不易吸湿,造成粘接材料的相对湿度比塑封材料的相对湿度低得多。塑封材料相对湿度较高,产生较大的湿膨胀,使湿应力主要分布在塑封材料与芯片相接触的界面上。由于材料参数失配,回流焊过程产生的热应力主要分布在粘接材料和铜焊盘的界面,以及塑封料和铜焊盘的界面,在经过吸湿和回流焊实验后观察到界面分层沿着这些界面扩展。

Finite element analysis（FEA） method was used to simulate the moisture diffusion and hygroscopic stress distribution of SiP module using COB form under the hygro-thermal environment,and the analysis of the thermal stress distribution was made in the process of reflow.Moisture absorption and reflow soldering experiments were analyzed to investigate the failure mode of this module.Results show that the die-attach（DA） material sandwiched between die and pad has much lower moisture absorption rate in absorbing moisture under the hygro-thermal environment,so the relative humidity of the DA material is much lower than that of epoxy molding compound（EMC）.EMC with higher relative humidity generates larger moisture expansion and makes hygroscopic stress mainly appearing at the interface between EMC and die.The thermal stress in the process of reflow mainly distributes at the interfaces of DA/pad and EMC/pad due to the mismatch of parameters of different materials,and it is observed that the interface delamination appears and spreads at these interfaces after moisture absorption and reflow soldering.