Copper and copper alloys are widely used for leadframe material
nowadays because of their excellent electrical properties, high
thermal conductivity, lower cost and high reliability of solder joint.
However, the copper surface is susceptible to oxidation during the
packaging process due to its high affinity to oxygen. Delamination is the main form of failure in plastic package. Currently,
there are two reasons explain for it: the thermal expansion
coefficient between leadframe and molding compound is mismatch
and the moisture absorbed within the plastic encapsulant
will vapor in elevated temperature [2]. The delamination often
leads to popcorn during the reflow process or awful using conditions,
which is detrimental the reliability of IC package, and limit
its applications especially in some extreme conditions, such as
the condition around the motors of automobile. Studies have revealed
that the delamination usually occurs at the interface between
copper leadframe and its oxide, which means the adhesive
strength at this interface relatively weak [3]. Therefore many scientists
focus on the field concerning the mechanism of copper’s
oxidation, factors to influence interfacial adhesion in plastic packages
and how to improve its performance [2,4]. Yoshioka and Lebbai
had studied silver coating and found Ag had great effects on
adhesion between leadframe an