Air mesh plasma for PCB de-smear process

Abstract

We modified an atmospheric pressure glow discharge proposed by Okazaki et al. (J. Phys. D: Appl. Phys. 26 (1993) 889) into an atmospheric air mesh plasma system and successfully verified a possibility to ignite and maintain an atmospheric pressure discharge in ambient air. Atmospheric pressure glow plasma was used for generating ozone with higher efficiency (J. Phys. D: Appl. Phys. 26 (1993) 889). We applied reactive oxygen radicals to cleaning process during the ozone generation process. In this study, the use of atmospheric air mesh plasma as a method of cleaning blind vias of printed circuit boards and ball grid array is being investigated as an alternative to a conventional wet process prior to electro-plating process and soldering. This is a first attempt to use atmospheric pressure plasma for electro-packaging in our knowledge. After atmospheric air mesh plasma treatment, scanning electron microscope images show clear blind vias compared with those of untreated samples. The contact angle measurement also shows a significant decrease in the contact angle. In conclusion, we can effectively remove the organic impurity and improve the surface cleanliness. Also these results may bring about the enhanced wire bondability and molding compound/solder mask adhesion.