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.
Non-Newtonian Flow Behavior
Paste Viscosity Dynamics
Solder pastes exhibit variable shear stress resistance under applied mechanical forces during surface mount stencil printing. Solder paste demonstrates non-Newtonian flow behavior by decreasing in viscosity when squeegee blades apply continuous shear forces. Dynamic fluid movement allows dense paste formulations to roll smoothly across stencil surfaces and fill tiny aperture openings.
Stopping squeegee movement allows the paste to recover its high static viscosity quickly.
Shearing Motion Mechanics
Mechanical shear forces generated by moving squeegee blades break down internal particle networks within the paste matrix. Shear thinning allows solder paste to flow through narrow apertures without clogging small openings. Post-printing viscosity recovery prevents paste bridges from forming between adjacent pads after stencil removal.
Paste formulations balance metal powder loading against flux vehicle rheology to maintain predictable flow characteristics under variable print speeds.
Stencil Release Limits
Insufficient shear rates prevent complete aperture filling during high-speed printing cycles on dense component layouts. Excessive shear rates break down flux vehicles permanently, causing paste slump and solder ball formation during reflow heating. Environmental temperature variations alter baseline viscosity, shifting fluid response curves during long production runs.
Rheological testing verifies flow behavior before approving solder paste lots for high-density assembly lines.