AVS 59th Annual International Symposium and Exhibition
    MEMS and NEMS Tuesday Sessions
       Session MN-TuP

Paper MN-TuP9
Electrostatic Deposition of a Micro Solder Particle Using a Single Probe by Applying a Single Rectangular Pulse

Tuesday, October 30, 2012, 6:00 pm, Room Central Hall

Session: MEMS and NEMS Poster Session
Presenter: D. Nakabayashi, Tokyo Institute of Technology, Japan
Authors: D. Nakabayashi, Tokyo Institute of Technology, Japan
K. Sawai, Tokyo Institute of Technology, Japan
P. Hemthavy, Tokyo Institute of Technology, Japan
K. Takahashi, Tokyo Institute of Technology, Japan
S. Saito, Tokyo Institute of Technology, Japan
Correspondent: Click to Email
Recently, demands for micromanipulation techniques have increased in order to realize highly functional microdevices such as MEMS. A technique to deposit a conductive microparticle onto a conductive substrate by using a single conductive probe as a manipulator has been proposed as one of the techniques. The technique can be used to increase the yield of a ball-grid-array (BGA), which is used for IC packaging, by fixing the individual soldering defect. Adhesional force between the probe and the microparticle is dominantly greater than gravitational force on the microparticle due to scaling law. Thus, repulsive force must be generated to detach the microparticle from the probe. In the technique, a solder particle with a diameter of 20–30μm, initially adhering to the probe tip, is detached and deposited onto a substrate by applying a voltage between the probe and the substrate to exert an electrostatic force on the particle. However, when a constant voltage was applied, the detached particle mostly went out of the microscopic view due to the excessive impact of the collision between the particle and the substrate. In the previous research, a voltage sequence was optimized in order to reduce the excessive impact. The success rate of the particle deposition in the previous research was 44%, and is not sufficient for industrial applications. In this study, a technique to deposit the particle on the substrate by applying a single rectangular pulse is proposed, and the mechanism of the deposition by the proposed technique is described. In the mechanism, an electric discharge between the probe and the particle when the particle reaches the substrate plays a dominant role in the particle deposition. The current of the electric discharge generates the Joule heat due to the contact resistance between the particle and the substrate. The small part of the particle which contacts the substrate is melted by the Joule heat, and the melted part absorbs the impact of the collision between the particle and the substrate. Consequently, the particle is successfully deposited onto the substrate. Moreover, the mechanism of the proposed technique is verified by experiments of particle deposition, which are observed by using a high-speed camera (645,000 frames per second), a scanning electron microscope (SEM) and an oscilloscope. The success rate of the particle deposition has improved to 93% by the proposed technique. Furthermore, the Joule heat and the volume of the melted region are evaluated as indicators of the damage to the particle caused by the electric discharge using an RC circuit model, and the applicability of the proposed technique is discussed.