Elucidation of Metal Etching Defects Through the Experimental Design Process Characterization at Encapsulation and Electro-deflashing Processes

Bond pad metallization is an important component in determining the quality of metallic interconnection in semiconductor packaging. Established process steps incorporating various activities in assembly line must ensure good bond pad metallization remain intact throughout the process since defects such as etched bond pad metallization due to physical and chemical interaction during these process steps will severely affect the quality and reliability of metallurgical interconnection. Detailed observation suggested that, even following strict procedure of these process steps, etched metallization have been found to occur at various degrees. Initial investigation revealed that several factors such as delamination, ingression path and corrosive elements may contribute to the etched metallization on bond pad. Therefore, this paper will systematically study on these factors focusing on the two important process steps that might be responsible to the etched bond pad metallization. These process steps are molding and deflashing steps. A small outline transistor has been used as test vehicle and design of experiment has been carried out to investigate contributing factors of the etched metallization. The result indicated that delamination plays a very important role in addressing etched metallization and many factors contribute to the delamination issue. Therefore, it is suggested that these factors must be identified and quantified in order to minimize the etched metallization. Furthermore, chemical, and physical interaction and mechanism between material and elements throughout the process steps must be clearly understood.