ToF-SIMS Analysis of Fiberglass Cloths for PCB Manufacturing

Woven fiberglass cloths are by far the most common reinforcement material used in PCBs. The glass yarns are coated with silane-based coupling agents designed to improve the bond between the glass filaments and the resin matrix. Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) was utilized in order to garner a better understanding of the observed poor glass surface wetting and weak adhesion of the resin to the yarn. These are the major root causes for a number of PCB failure mechanisms such as delamination cracks, IR (insulation resistance) and CAF (conductive anodic filament) growth. ToF-SIMS revealed that the silane surface is far from being ideal. The results are used to derive recommendations for the glass cloth suppliers in order to improve the efficiency of their silanation process.