Direct Bond Dual Ultrasonic Frequencies and Megasonic Frequencies on Removal of Sub-micron and Nano-Dimensional Particles: An Experimental Study
R. Vetrimurugan *
Advanced Ceramics Technology, Penang, Malaysia.
Terry Lim
Advanced Ceramics Technology, Penang, Malaysia.
M. J. Goodson
Crest Ultrasonics, Trenton, NJ, USA.
*Author to whom correspondence should be addressed.
Abstract
Aims: The purpose of this experimental study was mainly to investigate the effect of various frequencies in the range from ultrasonic to Megasonic on cleanability and erodability parameters using multiple extraction method.
Study Design: Experimental study.
Place and Duration of Study: Advanced Ceramics Technology Lab, Dept of Ultrasonic Cleaning Research and Development, Malaysia between April 2013 and Jan 2014.
Methodology: The parts are cleaned with various ultrasonic and megasonic frequencies using DI water as a cleaning medium. Various direct bond dual frequencies such as 58/132 kHz and 58/192 kHz, single ultrasonic frequencies such as 58 kHz, 68 kHz, 132 kHz, 192 kHz and megasonic frequencies such as 360 kHz and 470 kHz on particle removal from disk drive component was studied. Multiple Extraction Method (MEM) was used as a tool to measure the cleanliness and Liquid Particle Counter (LPC) was used to measure the particle concentration in the extracted solution. The Maximum Cleaning Potential (MCP) and First Stage Cleaning (FSC) was also calculated for various ultrasonic and megasonic frequencies.
Results: The result indicates that the first stage cleaning is high for patented direct bond dual frequency i.e 58/132 kHz compared to other frequencies. A combination of high cavitation intensity at 58 kHz to maximize removal of contamination plus significant acoustic streaming at 132 kHz to minimize re-deposition is considered to be responsible for this result. The result also indicates that the maximum cleaning potential is high for 58/132 kHz followed by megasonic frequencies such as 360 kHz or 470 kHz. The maximum cleaning potential and first stage cleaning is almost same for 68 kHz, 132 kHz and 192 kHz. The asymptote value is low for 192 kHz, 360 kHz and 470 kHz compared to other frequencies tested. The asymptote value decreases with increase of frequency. The multiple frequencies such as 58/132 kHz followed by 360 kHz or 470 kHz bring down the particle counts further and lead to higher particle removal. This is due to lower thickness of boundary layer for higher frequencies. Emphasis will be placed upon cleaning of metal spacers, but the concepts can be applied to cleaning of other parts as well.
Conclusion: The use of multiple frequencies ranging from lower ultrasonic to higher megasonic frequency will help removing populations of particles that vary widely in sizes. Crest ultrasonic patented direct bond dual frequencies and state-of-the art megasonic sweep frequencies 360 kHz and 470 kHz can help to remove wide ranges of particle sizes (both sub-micron and nano-dimensional particles) from various disk drive components and other related components.
Keywords: Ultrasonics, cavitation, acoustic streaming, dual frequency, first stage cleaning, maximum cleaning potential