Sampling and analysis of particles generated in contact start/stop-mode of a hard disk drive by using a particle sampler

Abstract

Particle contamination must be controlled to increase the storage capacity of a hard disk drive (HDD) as the flying height of the slider decreases. In the primary steps of particle contamination control, particles are precisely detected and analyzed. To carry out these steps, many researchers have used sampling methods. In this paper, we newly designed a particle sampler and evaluated the performance of the sampler. This sampler can collect particles by the applied electric field, by the impaction of particles, and by Brownian diffusion onto the sampling plate. We tested the performance of our sampler in terms of the parameters that affect the sampling efficiency of the particle sampler; sampling airflow rate, particle size, and externally applied electric field. The maximum sampling efficiency of unipolarly charged particles whose sizes ranged from 50 to 400 nm was about 90%. Also, we sampled particles generated during 20 contact start/stop cycles (CSS) of the HDD by using the particle sampler and analyzed the sampled particles by scanning electron microscopy (SEM) and Auger electron spectroscopy (AES). The SEM images showed that the sizes of the particles decreased and the number of sampled particles increased as the disk rotational speed increased. The AES spectrum showed that the sampled particles were composed of P, C, Ni and Al, which are the components of the disk materials. Therefore, we believed that the generated particles originated from the disk surface. To determine the overall sampling efficiency of the particle sampler, particles generated in the HDD were counted at the inlet and outlet of the sampler. The overall sampling efficiency increased with increasing applied voltage and disk rotational speed. The maximum overall sampling efficiency of the particles generated in the HDD was about 70% when the applied voltage and disk rotational speed were 0.5 kV and 9,600 rpm, respectively.