Evaluation of cleanroom/ESD garment fabrics: test methods and results

It was observed that Class 100 cleanroom garments, reported to be ESD safe, could easily be tribocharged to relatively high voltage potentials while in use. They also showed very slow and incomplete dissipation of these voltage potentials. With the introduction and widespread use of magneto-resistive (MR) technology in the disk drive industry, it was felt necessary to determine whether there are cleanroom/ESD safe fabrics which provide better ESD performance than others. This is especially important due to the close proximity of a garment's sleeve to the MR product, and the risk of the failure mechanism known as field induced breakdown (FIB). The testing reported within this paper was performed to accomplish two main goals. The first goal was to identify a material that would provide the best overall ESD performance, by performing comparative testing of numerous fabrics. The second goal was to make the test methods both simple and repeatable, while using moderately priced, commercially available equipment. It was found through this work that there are in fact substantial differences in the performance of cleanroom/ESD fabrics, and two materials were identified as clearly outperforming the others tested. Additionally, methods of testing with common instruments were developed that proved to be useful for the comparative testing of fabrics.