A Process For Treating Woven Glass Cloth

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 interfacial adhesion between the glass filaments and the resin matrix. Poor glass surface wetting and weak adhesion of the resin to the yarn are the major root causes for a number of PCB failure mechanisms. 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 following standard thermolysis processes during preparation of the glass cloth. A solvent-based process was demonstrated to yield excellent retention of the glass cloth physical properties while simultaneously providing a clean glass surface for bonding of the coupling agent. ToF-SIMS verified the presence of silane at the cloth surface. The results were used to derive recommendations for the glass cloth suppliers in order to improve the efficiency of their silanation process.