Mechanical and electrical characterisation of Au wire interconnects in electronic packages under the combined vibration and thermal testing conditions

This paper concerns the reliability of thermosonically bonded 25μm Au wires in the combined high temperature with vibration conditions, under which the tests have been carried out on wire bonded 40-pin Dual-in-Line (DIL) High Temperature Co-fired Ceramic (HTCC) electronic packages. Mechanical, optical and electrical analysis has been undertaken in order to identify the failure mechanisms of bonded wires due to the combined testing. The results indicated a decrease in the electrical resistance after a few hours of testing as a result of the annealing process of the Au wire during testing. Shear and pull strength levels remained high in general after testing, showing no significant deterioration due to the test under the combined high temperature and vibration conditions. However, a trend of the variation in the strength values is identified with respect to the combined conditions for all wire bonded packages, which may be summarised as: i) increase of the testing temperature has led to a decrease of both the shear and pull strength of the wire bonds; ii) the mechanical behaviour of the wires is affected due to crystallization that leads to material softening and consequently the deformation of wire.