Quantifying Resin Flow Shear Dynamics in Multilayer Laminate Buildup Operations
Modelling resin squeeze flow shear kinetics during multilayer pressing prevents inner-layer trace swim and guarantees reliable dielectric clearance.
Resin Viscosity Kinetics
Fluid Behavior
The time-dependent change in the flow resistance of epoxy systems during the heating cycle determines how well a laminate encapsulates copper circuitry. Resin viscosity kinetics describes the relationship between temperature, time, pressure and the resulting state of the liquid resin before it reaches a fully cured solid form. This process involves a sharp decrease in viscosity as the material melts, followed by a rapid increase as the chemical cross-linking reactions take hold.
Fabricators monitor these changes to ensure that the resin remains fluid enough to fill every gap between traces.
Lamination Control
Managing the heat rise rate in the lamination press allows for the optimization of the window where the resin is at its lowest viscosity. If the temperature increases too slowly, the resin may begin to cure before it has effectively wetted the copper surfaces. Conversely, a temperature rise that is too rapid can cause the resin to become too thin and squeeze out from the edges of the board.
Resin viscosity kinetics dictates the pressure application timing to prevent the formation of voids or the excessive thinning of the dielectric layers. Successful bonding requires the resin to flow into the microscopic topography of the copper foil to create a strong mechanical bond. The duration of this flow stage is a critical parameter for achieving uniform thickness across the entire panel.
Thermal Profiling
Differential scanning calorimetry and rheological testing provide the data needed to construct the ideal press cycle for a specific material. These measurements define the gel point and the minimum viscosity reached during the lamination process.