Propagation of adhesives in joints during capillary adhesive bonding of microcomponents

Capillary adhesive bonding is used successfully to integrate microsystems. To ensure high reliability and quality of the interconnection technique, it is imperative that the propagation of adhesives in the joints be controlle d. Two adhesives frequently used in capillary adhesive bonding were examine d: a one-component, UV-curing methacrylate adhesive (Dymax 191-M), and a tw o-component epoxy resin bonding adhesive curing at room temperature (Epo-te k 302-3M). The propagation of these adhesives in joints with different gap heights of 2-20 mu m between two PMMA surfaces and between one PMMA and one PI surface was measured and compared with the theoretical adhesive propaga tion in accordance with the Hagen-Poiseuille equation for a gap flow, with the capillary pressure taken into account. Once the dynamic viscosity, the wetting angle and the surface tension of th e adhesive have been determined as a function of the measuring time, the me asured propagation of the Epo-tek 302-3M and Dymax 191-M adhesives can be d escribed in good agreement with the theory for all the gap heights under st udy.