Statistical Characterization of Human-Induced ESD

Abstract

Knowledge of the electrostatic discharges (ESD) environment of electronic products is essential in order to perform product risk assessment and select ESD test levels that ensure a level of field reliability. However, there is very little statistical data on ESD occurrence rate and severity in the real world, and most of it is limited to data from single rooms or objects. In particular, portable and wearable devices experience much more complex environments than a product limited to a single room. To address this gap in data on ESD occurrence and voltage levels, an exemplary participant study has been conducted using a portable in-situ ESD detector. Discharge events are detected based on the drop in electric field on the body and a magnetic field sensor makes it possible to estimate discharge current and also to distinguish between human skin (HS) and human metal (HM) discharges. The study for the first time captures ESD data in combination with background information on the activity performed right before the ESD and also the object that was touched. This background information is obtained by a mobile phone application prompting participants right after an ESD, providing information on the charging mechanism and more. The exemplary study with 14 participants demonstrates how complex ESD environments can be characterized using in-situ ESD event detection. An average of 0.26 ESD events per hour were recorded, of which one sixth were HM discharges. Data of another study on ESD charge voltage levels with more than 46,000 measurements is additionally presented for the first time. While a comparison of the results with this large reference data set showed reasonable agreement for voltage level distribution, it indicates that the broader range of scenarios captured by in-situ measurement leads to higher voltage levels.