Experimental Investigation of Contamination Removal from Slider Bar Surface by Using Various Cleaning Methods

Abstract

The rapid advancements in various current technologies and the constant trend in miniaturizing of components have created a need for higher cleanliness levels. Contamination in the level of monolayers can drastically alter surface properties such as wettability, adhesion, optical or electrical characteristics. To select an effective cleaning method the three essential factors to be considered such as cleaning chemistry, the scrubbing method and other process parameters. This study investigates the effectiveness of brush cleaning, ultrasonic cleaning and combination of brush and ultrasonic cleaning on removal of contamination, surface defects and brush life time. In this study, the cleaning efficiency was compared for the parts cleaned with ultrasonics, nylon brush, Poly Vinyl Alcohol (PVA) brush and combination of ultrasonics and nylon brush. The life time of brush was studied for both nylon and PVA brush. The techniques used to identify the contamination are SEM, EDX and optical microscope. The microscopic result indicates that the removal efficiency was high for the parts cleaned with ultrasonics (90.5%) and PVA brush (90.2%) as compared to Nylon brush (77.4%). This is due to the fact that for PVA brush the fluid was being pumped in and out of brush pores (during compression and elastic recovery of the brush), carries the contamination away from the surface and also the contact area between the contamination surface and brush was more. From Liquid Particle Count (LPC) analysis, the >0.3 mic particle counts is almost two times lower for parts cleaned with ultrasonics as compared to parts cleaned with brushes. This indicates that 58/132 kHz washing followed by 470 kHz DI rinsing effectively removes sub- micron particles from the surface compared to brush cleaning. The defects caused by brushes on the surface of the slider bar is almost 1% for nylon brush cleaning, 0.4% for PVA brush cleaning and 0% for ultrasonic cleaning. From experimental study, it can be seen that the life time of PVA brush was shorter than Nylon brush by 75 times. The contamination increased after 50th run for PVA brush and after 700th run for nylon brush. This is due to the fact that after brush damage (after 50th run for PVA and 700th run for nylon) the brush can not effectively remove the contamination and also re-deposition of contamination from brush.