THE SOLVENT-INDUCED CRACKING IN GLASSY POLYMER-COATINGS BY ATOMIC-FORCE MICROSCOPY

Polymer coatings for microelectronics packaging frequently undergo ductile-brittle transition when in contact with the specific solvents, which can cause the local deformation zones to grow from the stress concentrations and lead to cracking and debonding. Owing to the adhesion to the substrate, the surface opening of the deformation zones is very narrow, investigation of the microstructure cannot be made by optical microscopy or scanning electron microscopy. However, using the atomic force microscope, it was found that the depth of the zones increased with immersion time, indicating that they grew from the surface into the interior. The stress release induced by the deformation zones could be measured as a function of position. Furthermore, the zone depth increased linearly with the zone width. The zone growth and film-thickness effect, together with the cracking of the free-standing films in different solvents, were investigated.