Dynamic Squeeze Flow Hydrodynamics across Ultra Smooth Circuit Foil Interfaces
Dynamic resin squeeze flow across ultra smooth copper foils demands precise thermal press ramping to prevent micro-voiding and hold tightly controlled plane spacing.
Profile Height Sa
Surface Roughness
Arithmetic mean values of the absolute height deviations measured across a defined three dimensional area characterize the texture of a surface. Calculation of the profile height sa provides a more comprehensive view of surface texture than traditional linear measurements. It captures the overall topography of a copper foil or an etched laminate surface.
Bond Strength
Mechanical interlocking between the resin and the metal depends on the density and height of the surface peaks. Calculation of the profile height sa assists in evaluating the effectiveness of chemical micro-etching processes.
Measuring
Assessment usually requires non contact methods such as confocal microscopy or white light interferometry. Unlike two dimensional measurements, profile height sa accounts for the spatial distribution of features across the entire sampling area. This helps in predicting the adhesion of dry film resists and solder masks during the fabrication process.
A surface that is too smooth may lead to delamination, while a surface that is too rough can increase signal loss at high frequencies. Standards for high speed digital circuits often specify a maximum value for this parameter to balance electrical performance with structural integrity. Modern laser direct imaging systems rely on a consistent surface profile to ensure accurate registration and resolution of fine features.
They demand accuracy.