The surface mount type package has many advantages, but popcorn cracking by the expension of absorbed moisture frequently occurs during the mounting process. One solution to the popcorn cracking can be found in the improvement of adhesion strength between EMC and leadframe. In this present analysis, various metal films such as Cr, Ti, Ni, Mo, and Al were deposited on the leadframe surface by dc magnetron sputtering before encapsulation with epoxy molding compound. Film thickness was 1000Å on each metal deposit process constantly. Adhesion strengths were measured by the simple pull-out test initially. Reliability of the epoxy/leadframe system was tested under the 85℃/85% R.H.condition. Later, fracture surface were analyzed by SEM, AES and XRD.
After post mold curing(PMC),in the case of Al or Ti deposited specimen their had high pull strength. But pull strength was decreasing in the reliability test on time dependently. The formation of oxide or carbide at EMC/film interface can be induced high adhesion strength and high reliability as compared with others, such as Mo, Ni deposited on leadframes and untreated copper based leadframe.
