Material Science
Matter flows and deforms in complex ways when subjected to external forces like shear or compression. The discipline of rheology provides the tools to measure how solder pastes and adhesives change from a solid-like state to a liquid-like state. This transition is essential for screen printing where the material must pass through a stencil and then hold its shape on the pad.
Understanding these properties ensures that the assembly remains stable throughout the production line.
Solder Paste
Viscosity and elasticity define the behavior of the chemicals used in board assembly. In the context of rheology, the recovery time of a paste after the squeegee passes is a critical metric for print definition. If the material does not regain its stiffness quickly, the printed deposits will slump and cause shorts.
Dispensing Performance
Automated dispensing systems rely on the predictable thinning of fluids under high pressure. Advanced rheology studies help in formulating underfills that flow into tight spaces while carrying heavy loads of ceramic fillers. These fillers improve the thermal properties but also complicate the flow behavior.
Testing the material at different temperatures reveals the process window for reliable application. Proper storage and handling prevent the separation of the components and maintain the consistency required for high-speed placement.
