Modeling Slip Velocity and Pressure Gradients across Smooth Copper Foils
Modelling slip velocity and pressure gradients across smooth copper foils prevents resin starvation and locks dielectric thickness tolerances during lamination.
Resin Flow Dynamics
Fluid Movement
Viscous liquids behave according to specific physical laws when subjected to heat and pressure during the assembly of multilayer substrates. Resin flow dynamics describes the physical behavior of thermosetting polymers as they move through the glass reinforcement and around copper circuitry. The study of these dynamics involves calculating how the prepreg liquifies and migrates to fill the spaces between features.
This behavior is non-linear because the viscosity changes constantly as the temperature rises and the chemical reaction proceeds.
Encapsulation Efficiency
Temperature profiles in the lamination press dictate the duration of the fluid state. Rapid heating reduces the minimum viscosity, which alters the resin flow dynamics and can lead to excessive squeeze-out at the edges. A slower ramp allows for more controlled movement and better air evacuation.
Process Optimization
Copper density across the circuit board influences the local resistance to the moving liquid. In areas of high trace density, the resin flow dynamics are restricted, requiring a lower viscosity or higher pressure to achieve full coverage. If the resin moves too quickly, it might wash away delicate features or cause internal layers to shift.
Measuring the flow distance in test coupons validates that the material properties and the press settings are correctly matched.