Sessile Drop Goniometry

Measurement Execution

A precision syringe deposits a specific volume of liquid, such as deionized water or diiodomethane, onto the substrate. The software used in sessile drop goniometry then fits a curve to the droplet shape to find the tangent at the contact point. This procedure must be performed in a controlled environment to prevent dust or air currents from affecting the results.

Consistent droplet size and placement are necessary for obtaining repeatable data across different samples. Fabricators use this information to decide if a board needs additional plasma treatment or chemical cleaning.

Surface Characterization

High angles indicate poor wetting while low angles show that the liquid is spreading effectively over the surface. Sessile drop goniometry provides the empirical data needed to qualify new solder masks or conformal coatings. This testing ensures that the selected fluids will form a continuous and protective layer.