Rheological Testing
Dynamic measurements of fluid resistance to flow provide important quality control data for solder paste formulation. Using a spiral pump viscometer allows testing labs to measure paste viscosity under different shear rates. This instrument draws solder paste into a chamber and pumps it through a narrow thread.
The resulting torque measurement indicates how the paste will behave during stencil printing.
Shear Profiling
Varying the pump speed simulates the different shear forces that the paste experiences during the print cycle. A high pump speed mimics the action of the squeegee as it forces paste through stencil apertures. Slower pump speeds simulate the post-print period when the paste must stand on the pad without slumping.
These tests help manufacturers adjust the chemical composition of the paste for optimal performance.
Process Validation
Daily calibration of print room materials prevents production failures on the assembly line. Viscosity values that fall outside the standard limits lead to stencil clogging or print slumping, which directly degrades solder joint quality. Testing each new lot of paste with this viscometer ensures that only materials with the correct flow properties enter the printing machine, reducing stencil wipe frequency and maintaining high throughput across multi-shift assembly operations.
