Original Date: 01/23/1995
Revision Date: 01/18/2007
Information : Shielded Plasma Cleaning for Package Assembly
In response to the elimination of ozone depleting solvent use and in an effort to improve the quality and reliability of their microcircuits manufactured on site, Sandia National Laboratories (SNL) has instituted a change in the cleaning process for microcircuits. Manufacture of microcircuits requires cleaning prior to die attach, before wire bonding, before hermetic sealing, and after soldering. This cleaning process removes contamination caused by outgassing and bleedout of epoxy used in bonding processes, contamination from photoresist, humans, and air from poor storage conditions. Traditionally, these cleaning processes have been accomplished using freon vapor degreasing.
A traditional replacement for the freon degreasing process is one using plasma barrel chambers. The unique plasma process at SNL employs a downstream process rather than the traditional barrel chambers. Downstream or shielded processing generates plasma in one part of the chamber, then flows the excited but neutral component of the plasma down to the part to accomplish the atomic cleaning. Hence, the circuits and packages are not immersed in the plasma with its high frequency oscillating electromagnetic fields of positive and negative charged particles.
This process has provided for increased wire bondability of difficult to bond surfaces, improved wire bond quality and reliability, elimination of plasma induced circuit damage, elimination of one more ozone-depleting solvent (Freon), and pollution prevention and waste minimization.
Additional research into the benefits of using a downstream plasma cleaner is being conducted by SNL. Sandia maintains that this research will lead to even higher reliability of microcircuits and drive down some of the associated manufacturing cost.
For more information see the
Point of Contact for this survey.