Dynamic modeling for resin self-alignment mechanism

A new self-alignment process using surface tension of resin material was developed to realize a low-temperature, fluxless, and cost-effective alternative alignment process for the future assembly of electronic and optoelectronic systems. In this new self-alignment process, we achieved self-alignment capability by using 3-dimensional pads to form the positioning boundary, and by mounting chips in the opposite direction. This process releases the force acted on liquid bumps, even when using resin material, which has been known not to possess self-alignment capability because of its low surface tension. As the viscosity of the resin material is considerably higher than that of the solders, the restoring force resulting from its low surface tension must be larger than the resistance force resulting from its high viscosity.In this paper, we propose a new passive alignment mechanism using the surface tension of a resin material and a comprehensive mathematical model in order to enhance understanding of the self-alignment behavior of resin. Moreover, we conducted a scaled-up experiment to calibrate and verify the model's accuracy. It has been proved that resin self-alignment behavior is totally different from the oscillatory motion of solder alignment. This shows that the motion is aperiodic, regardless of the initial conditions of the system, such as an overdamped system due to the low surface tension and high viscosity characteristics of resin material.