Electrostatic force acting on conductive ball between electrodes

To advance electrostatic applications such as novel printing technologies and solder ball control for LSI bumping, the electrostatic force acting on a conductive ball between two electrodes is calculated. The electrostatic force increases as the ratio of the ball diameter to the electrode separation increases. The electrostatic force is also calculated for the case when a charge pattern is formed on the insulating layer on the upper electrode. In this case, the electrostatic force initially varies as the square of the charge pattern area but eventually plateaus to a constant value as the area increases. Experiments investigating the force acting on the ball are performed. The force estimated from these experiments agrees with the value obtained by electric field analysis.