共晶烧结贴片氮气保护改进研究

军用陶瓷或金属封装中的共晶烧结芯片贴装工序存在的主要问题是,Sn基焊料极易氧化形成Sn₂O、SnO₂等氧化物,在共晶过程中不断堆积在焊料表面,形成焊料表面悬浮颗粒,造成PIND失效。文章基于氧化膜破裂理论,通过对当前使用的共晶烧结氮气保护的结构进行改进,采用小型半密闭腔体的方式实现了局部高纯度氮气保护环境。在共晶烧结贴片过程中,氧化膜破裂融入焊料体内,同时因氧化膜破裂而流出的熔融焊料在良好的氮气保护环境下形成新的光亮圆润的焊料表面,有效减少了焊料表面悬浮氧化物颗粒。统计数据表明,该改进研究有效降低了PIND失效率和成品筛选电路的成本损失；该改进实现了共晶烧结贴片焊料表面极少产生悬浮氧化物颗粒,极大地降低了可动颗粒导致的电路短路、断路等误动作的危害性和可靠性风险。

Study on Nitrogen Protection Improvement of Chip Eutectic Die Attach

The main problem of eutectic die attach in military ceramics or metal packaging is that Sn based solder is easily oxidized to form Sn₂O, SnO₂ and other oxides, which will be constantly accumulated on the solder surface in the chip eutectic die attach process, forming the surface suspended particles of the solder, resulting in PIND failure. Based on the oxide film rupture theory, this paper realizes the high-purity nitrogen protection environment by improving the structure of eutectic sintered nitrogen protection currently used, and adopting a small semi-closed cavity. In the eutectic die attach process, the oxide film rupture was integrated into the solder body, and the molten solder that flowed out due to the oxide film rupture formed a new bright and rounded solder surface in good nitrogen protection environment, effectively reducing the suspended oxide particles on the solder surface. A large number of statistical data show that the improved study effectively reduces the PIND failure rate and the cost loss of the finished circuit. On the other hand, it was realized that very few suspended oxide particles were generated on the surface of the eutectic solder, which greatly reduced the hazard and reliability risk of short and open circuit and other malfunctions caused by movable particles.