The Design of Experiment to Determine the Optimum Parameters for Air Particles Control in the Head Gimbals Assembly (HGA) Washing Process

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Prajit Peamoon
Pichit Sukcharoenpong
Suwitchaporn Witchakul


The aim of this research is to increase the quality of the Head Gimbals Assembly (HGA) by reducing the particle contamination of the washing process in the Cleanroom. Six factors have been identified and the experiments have been conducted. The six factors are 1) the air velocity of the fan filter, 2) the width of the air return, 3) the holes’ diameter of the washing machine table, 4) the height of the air ionizer, and 6) the suction force of the exhaust. The Box-Behnken Experimental Design has been used to identify the significant effect of each factor. A Response Surface Methodology (RSM) technique was then applied to determine the proper configuration of each factor. The optimal setting obtained from the experiments are as follows: 1) the air velocity of the fan filter unit (FFU) should be 105 feet per minute (fpm), 2) the width of the Air Return should be 1 centimetre (cm), 3) the Holes’ diameter of the washing machine table should be 3 millimetres (mm), 4) the effect of the height of the air ionizer is not significant, and 5) the suction force of the Exhaust should be 300 fpm. The mathematical analysis showed that the amounts of size 0.3 microns (µm) particle are reduced from 4,392 to 57 Counts per cubic foot (Counts/ft3) and the amounts of size 0.5 µm particle are reduced from 1,323 to 1 Counts/ft3, respectively, which are conformed to the operating standard required by the US Federal Standard 209E. The confirmation production run then conducted and it’s shown that the actual amounts of size 0.3 and 0.5 µm particles obtained are 68 and 17 Counts/ft3, respectively. This is expected to help reducing defect and increase quality in the production of components in the hard disk drive.


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