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In last month’s column, I presented an overview of conventional oxide chemistry and the critical success factors of the process. In this column, we begin our review of the oxide alternative process that is often referred to as an organo-metallic coating process. The reason for this alternative name will be explained in this column.
With continued emphasis on long-term reliability and vastly improved electrical performance, manufacturers of high layer-count multilayer printed wiring boards are beginning to abandon the reduced oxide bonding process in favor of alternative methods. One such method, presented here as an organo-metallic adhesion promotion system, increases the bond strength of the resin to the copper by modifying the topography of the copper surface and simultaneously depositing an organic layer that acts as an adhesion promoter. The surface area or topography of the copper is enhanced by the selective micro-etching along the grain boundaries of the copper. (This mechanism will be discussed further below.) This is in contrast to the oxide-based chemical processes in that the oxide processes are designed to “grow a crystal structure” on the copper surface. The concern with oxide processes (even the formulations designed to give a denser shorter crystal structure) is that the higher pressures and temperatures of lamination required for higher performance laminate materials will fracture the oxide crystal structure reducing the bond strength. With that said, let’s discuss oxide alternative or organo-metallic chemistry and how it all works.
Read the full column here.
Editor's Note: This column originally appeared in the March 2014 issue of The PCB Magazine.