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.
Wall Velocity Modeling
Computational Simulation
Numerical techniques simulate the interaction between a moving liquid and the stationary or moving boundaries of a container or channel. In the context of solder paste printing, wall velocity modeling helps to predict how the paste detaches from the stencil apertures. This simulation accounts for the friction at the metal interface and the internal shear within the material.
It allows designers to optimize the stencil coatings and the aperture shapes for better deposit consistency.
Flux Behavior
Fluid dynamics at the boundary determine the success of the transfer process. Wall velocity modeling shows that the paste near the center of the aperture moves faster than the material in contact with the walls. This velocity gradient is a primary cause of paste residues left in the stencil.
Process Prediction
Refining the model involves incorporating the specific rheological properties of the solder alloy and the flux. By using wall velocity modeling, engineers can test the effects of different squeegee speeds and pressures without running expensive physical trials. This approach identifies the limits where the paste will no longer flow correctly or where the stencil will fail to release.
The final output provides a set of optimized parameters that maximize the yield on the production line. Accurate simulations reduce the time spent on manual tuning and minimize the occurrence of common printing defects.