Fluid Deformation
Mechanical deformation models describe the lateral displacement of a viscous substance confined between two approaching solid surfaces. Incorporating stefan squeeze flow principles allows laminate designers to optimize the thickness and resin distribution of multilayer circuit boards. This behavior dictates how the liquid prepreg moves from high-pressure areas over copper traces into the empty spaces between the tracks.
This action prevents the formation of air pockets and ensures a uniform board thickness after curing.
Compression Dynamics
The physical process is characterized by a high pressure gradient that develops at the center of the plates, forcing the liquid to accelerate outward towards the boundaries. This flow creates a strong shear field that can orient any reinforcement fibers or ceramic filler particles present in the resin along the direction of the flow. In a typical lamination process, this shear behavior determines how quickly the liquid resin fills the fine gaps between adjacent copper lines.
Because the velocity profile across the gap is parabolic, the highest flow rates occur in the middle of the prepreg layer, while the resin near the copper surface remains stationary.
Physical Limitation
Frictional resistance at the plate interfaces and the presence of woven glass fabric can restrict the lateral movement of the resin. When the fluid cannot slip along the copper surfaces, the flow becomes highly restricted, and the shear rates rise. If the resin contains high concentrations of mineral filler particles, the particles may segregate from the liquid, leading to uneven mechanical properties.
