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.
Squeeze Flow Rheology
Fluid Evaluation
Polymer melt characterization methods analyze the behavior of viscous materials compressed between two parallel plates under controlled loads. This squeeze flow rheology explains how uncured prepreg resin flows around copper traces during the circuit board lamination process. It governs the rate of thickness reduction and the lateral spreading of the fluid resin as the lamination temperature rises.
This analysis provides the mathematical foundation needed to model and prevent voids or uneven laminate thicknesses.
Deformation Mechanism
Experimental test fixtures apply a constant axial force or displacement rate to a cylindrical sample of the resin while measuring the resulting gap height. As the plates compress the sample, the material is subjected to both shear and extensional deformation forces, which are highly dependent on the shear rate and the temperature of the plates. The resulting pressure distribution within the fluid layer can be mapped to extract the shear viscosity and the yield stress of the polymer.
By plotting the change in sample thickness against elapsed time, engineers can calculate the viscoelastic response of the resin under typical lamination conditions.
Material Boundary
The mathematical model loses accuracy when the gap height becomes comparable to the size of the glass fibers embedded in the prepreg resin. In these thin-gap scenarios, the suspension can no longer be treated as a homogenous fluid, and the fiber-to-fiber contact forces begin to dominate the mechanical response. This restriction defines the limits of using the analysis for thin dielectric laminates.