Plasma cleaning of plastic ball grid array package

An investigation of O-2, Ar and Ar/H-2 plasma cleaning was carried out on p lastic ball grid array (PBGA) substrates to study its effects on surface cl eanliness, wire bondability and molding compound/solder mask adhesion. Opti mization of the plasma cleaning process parameters was achieved using the c ontact angle method and verified by auger electron spectroscopy (AES), X-ra y photoelectron spectroscopy (XPS) and wedge pull tests. It was found that both the wedge bond quality and moisture sensitivity of a 225 I/O PBGA pack age were improved after plasma cleaning. Furthermore, atomic force microsco py (AFM) characterization and XPS analysis revealed that the solder mask ha s undergone plasma-induced surface modification. Cross-contamination of Au and F traces on the solder mask that has occurred during plasma cleaning wa s identified by XPS. This study has demonstrated the benefits and consequen ces of plasma cleaning for a PBGA package. (C) 1999 Elsevier Science Ltd. A ll rights reserved.