Impact of thin silicone film contamination and laser treatment on adhesive bonds

Almost all industries depend on reliable adhesive bonds. Adhesive bonding is a "special process", where non-destructive in-line inspections of the sample are not practicable. To ensure reliability, profound knowledge of the mechanisms of the adhesion and a proper understanding of the adhesive process is crucial. In this paper the impact of different thin silicone films and laser cleaning processes on the bond quality is assessed. Therefore, aluminum samples are contaminated with various thin silicone films and the laser cleaning process is applied. Afterwards the adhesive is dispensed, cured and the shear strength is measured. The results are interpreted based on five hypotheses that set the laser effect on the morphology change in relation to the laser cleaning effect. The transition zone between adhesive and samples is investigated using cross sections and the non-destructive imaging technique 3D-X-ray microscopy (XRM) scans. Furthermore, the surface free energy (SFE) and the surface roughness of the samples are measured and correlated with the shear strength. Our data show that the quality of adhesive bonding can be significantly improved through the interplay between various surface parameters and treatments.