Reliability of microelectronic packages with tin-plated copper leads under high humidity operating environment

Lead frame is the primary package metallurgical bond pad interface in microelectronic devices which provides external interconnection. The most predominant lead frame material is copper with tin plating. Over the years, galvanic corrosion and copper oxidation are two main reliability concerns for any microelectronics packages with copper lead frame, when operating under high humidity environment. In our reliability lab, we frequently encountered corrosion and oxidation on the leads backside of certain devices which had undergone autoclave stress. Often, this observation is correlated to the rise in drain-to-source on-resistance. Failure analysis result revealed that non-homogeneous tin plating is the contributing factor. In the past, our operators utilized conventional cleaning method, that is, polished leads backside with sandpaper followed by acetone rinse. Nevertheless, this could not remedy the problem effectively. We have performed research study to prove that solder dip is a better solution to eliminate corrosion and oxidation away from the leads.