Fracture behaviour of adhesive bonds by different shear speed

Electrically conductive adhesives are an interesting alternative for environmentally friendly electronic packaging. Polymers are insufficient examinated regarding their mechanical behaviour in comparison with solder materials. The chemical constitution of polymers is more complicated than metals and ceramics. Based on structural constitution the visco-elastic and the visco-plastic deformation behaviour of polymers show an intense dependence on temperature and speed of strain. The glass transition temperature T_g is a significant parameter for polymers [1], [2]. For destructive testing with a mechanical load it is important on which working temperature the stress occurs: below, above or near glass transition temperature T_g [1]. All kinds of polymers (thermoplastic, elastomer, duromer) are based on linear molecular chains. Dipole, hydrogen or van-der-Waals-bonds can appear depending on the molecular structure. Additional the linear molecular chains are bonded more or less with covalent bonds getting a molecular network. Epoxide resins are amorphous duromer and have a high cross linking density (10^-2...10^-1)[1]. A high cross linking density has an important effect on the properties of the adhesive, for example high strength and chemical stability. In comparison with metals and ceramics the elastic modules of polymers are much lower and the kind of bonds between molecular chains determines the mechanical stiffness.