Nonlinear vibration of contact interface in ultrasonic bond system

In order to increase the bonding strength, decrease the nonlinear vibration of ultrasonic transducer system and enhance the stability of chip bonding, this paper described the ultrasonic propagation at the contact interface in a thermosonic bonding system and presented a micromechanical model of ultrasonic propagation. When the static stress is small, the total stress is smaller than zero. The contact interface of two materials will detach, which makes the waveform of output ultrasonic imperfect, and the displacement of material particle vibration is small. When the static stress increases, the materials enter elastic deformation phase and the output ultrasonic waveform is identical to the input ultrasonic waveform with the maximum displacement of the material particle vibration. When the static stress is large enough, the materials enter plastic phase. Residual stress and residual displacement exist in interior material because of loading and unloading of dynamic stress, and hardening of material comes into being, which leads to the distortion of output ultrasonic waveform and the decrease of material particle vibration displacement. An experiment is conducted and the results are testified by the model.