Oxide Preparation
Chemical conditioning forms a micro-rough copper topography on inner layer cores during multilayer printed circuit board fabrication. Inner layer surface treatment establishes the mechanical interlock required for reliable resin adhesion during subsequent lamination cycles. Micro-etching agents and alternative oxide baths generate specific peak and valley distributions measured in micrometers across the foil face.
Insufficient topography depth leaves the interface vulnerable to delamination when thermal stresses from sequential drilling and plating expand the dielectric layers.
Lamination Bonding
Elevated temperature and hydraulic pressure force liquid prepreg resin into the prepared copper profile to construct a solid laminate stack. Inner layer surface treatment dictates how completely the flowing epoxy wets the metallic peaks without creating localized voids. Trapped air pockets or incomplete resin penetration inside the treated zone reduce dielectric breakdown voltage during high frequency signal transmission.
Post-press peel strength testing quantifies this adhesion performance by pulling bonded copper foils from the cured core at a constant velocity.
Thermal Stress
Subsequent assembly heating steps test the chemical stability of the copper resin boundary created during core fabrication. Inner layer surface treatment prevents moisture ingress from hydrolyzing the oxide bond during lead-free solder reflow profiles that exceed two hundred sixty degrees Celsius. Delamination defects appear as internal blistering during automated optical inspection or cross-sectional micro-sectioning after thermal shock exposure.
Preventing these structural failures requires strict bath chemistry control to maintain uniform coating thickness across every internal power and signal plane.
