The Bond Between Layers
After inner-layer cores are etched and AOI-inspected, the copper surface is smooth and chemically passive. Laminate prepreg directly onto this surface and bond strength falls below IPC-6012 minimums. Oxide treatment transforms it: a controlled chemical reaction grows a microscopically rough oxide layer that dramatically increases surface area and creates chemical bonding sites for prepreg resin. Brown oxide produces fine uniform crystals - standard for most designs. Black oxide grows longer needle-like crystals for maximum bond strength.
Our continuous conveyorized lines - ChuangKe and DengTai - process cores through clean, micro-etch, oxide grow, rinse, and dry stages. Bond strength exceeds IPC-6012 requirements with comfortable margin.
