Meaning
Analytical procedures for measuring the mechanical durability of thin-film coatings rely on a diamond stylus drawn across a surface under increasing vertical loads. Precise measurement through microscratch testing identifies the point at which a protective layer separates from its substrate. This method provides the data needed to qualify coatings for mobile device screens and enclosures.
Stylus Displacement
Force gradients applied to a moving tip reveal the elastic and plastic deformation of a material. Lateral sensors in microscratch testing detect the friction changes that occur when a coating begins to fail. These sensors provide a high-resolution map of surface resistance.
Critical Load
Specific weights at which the first sign of cracking appears define the strength of a bond. Determining the critical load during microscratch testing allows engineers to compare different supplier batches for consistency. Higher loads indicate better adhesion and scratch resistance in the final product.
Surface failure typically occurs through chipping or delamination.
Adhesive Failure
Coating detachment indicates a mismatch between the film and the underlying material. Microscratch testing reveals whether the failure is cohesive within the film or adhesive at the interface. Manufacturers use this information to adjust plasma cleaning or primer application steps.
A successful test confirms that the protective layer can withstand daily handling.
