Plasma cleaning of plastic ball grid array package

An investigation of O2, Ar and Ar/H2 plasma cleaning was carried out on plastic ball grid array (PBGA) substrates to study its effects on surface cleanliness, wire bondability and molding compound/solder mask adhesion. Optimization of the plasma cleaning process parameters was achieved using the contact angle method and verified by auger electron spectroscopy (AES), X-ray 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 package were improved after plasma cleaning. Furthermore, atomic force microscopy (AFM) characterization and XPS analysis revealed that the solder mask has undergone plasma-induced surface modification. Cross-contamination of Au and F traces on the solder mask that has occurred during plasma cleaning was identified by XPS. This study has demonstrated the benefits and consequences of plasma cleaning for a PBGA package.