Lead frame cleaning is necessary prior to the Die attach process. Leadframes are usually cut from thin copper sheets, stamped and refined via galvanic processes.  In case of very thin and homogenous contamination layers, plasma is often used for these cleaning applications.

However, cleaning with plasma alone is not sufficient to remove heavier contamination caused by stamping and cutting oils from the lead frames.

A wet cleaning process is highly recommended prior to the die attach process as well as other subsequent production steps, i.e. wire bonding and moulding.