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.
Lamination Pressure Cycle
Consolidation Profile
Multilayer board fabrication steps dictate the programmed application of force over time to compress prepreg sheets and copper foils into a solid laminate. A lamination pressure cycle must balance the thermal reduction in resin viscosity with the mechanical squeeze force. This profile ensures that the liquefied resin flows into the spaces between copper traces before it cures.
It begins with a low contact pressure during the heat-up phase and transitions to a high consolidation pressure as the resin approaches its lowest viscosity.
Mechanical Process
Thermomechanical analysis of the resin behavior dictates the timing and magnitude of the pressure change during the pressing cycle. During the initial temperature ramp, the resin softens and starts to flow, which requires a moderate force to distribute the material evenly without squeezing too much resin out of the board. As the cure progresses and cross-linking occurs, the pressure is elevated to its maximum level to force out trapped air and compress any remaining moisture.
This elevated force is maintained throughout the high-temperature cure window and during the subsequent controlled cooling phase to prevent warp or internal stress build-up.
Defect Prevention
Excessive pressure during the low-viscosity stage causes resin starvation, leaving glass fibers dry and susceptible to subsequent chemical delamination. Too little force leads to thick dielectric spacing and micro-voids between copper lines. Consequently, the pressure profile must be tuned to the specific resin chemistry and copper distribution of each board design.