An analysis on oxidation, contamination, adhesion, mechanical stress and electro- etching effect toward DIP package delamination

Abstract

Package delamination forms a separation layer in between mold compound to chip, die paddle and leads, which subsequent affects ground bond quality and degrades package electrical performance. This paper focuses on the interaction relationship of each assembly process towards lead delamination in Dual in Line (DIP) package. No ground bond delamination is allowable to ensure the package robustness. An experiment was conducted to characterize and understand the effect of assembly-induced lead delamination. The identified critical processes include the staging time control from die placement to curing after die bond, contamination of volatile outgassing from epoxy A in poor air oven circulation during epoxy curing, thermal oxidation, mold compound wettability on leadframe during molding, electro-etching effect from deflashing as well as mechanical force from singulation were investigated. Electrolytic deflashing has identified as the primary root cuase of lead delamination due to electro etching effecct. Secondary factor to further increase the lead delamination is poor mold compound to leadframe adhesion due to imbalance mold flow, mechanical force from singulation and severe copper oxidation. Improved mold tooling concept will be beneficial to further minimize the imbalance mold flow between the top mold and bottom mold. Chemical dipping without electric current is recommended as promising lead delamination results and is reflected in C-SAM (Scanning Acoustic Miscoscope).