Effect of spark gap shape on time lag

Abstract

Presented is the effect of sharp spark gap on time lag, which is a very important factor in electrostatic discharge modelling. A long time lag induces a large discharge current and a fast rise time. The large discharge current often causes soft errors in many products. Through measurement and simulation, the relation between sharp edge and time lag is quantified. The result can be used in numerical simulation of breakdown voltage. With the numerical simulation, knowing only the geometry of the spark gap can obtain the discharge current.Introduction: In many products such as cell phones and portable computers, a gap may exist and secondary discharge will occur. Secondary discharge can either upset or damage the product. Secondary discharge [1] is related to the geometry of the gap. The shape of the gap in the product can be complex, but it could be classified as homogeneous or pointed. The pointed gap is non-homogeneous, and the maximum static field strength of the pointed gap is much larger than the homogeneous static field strength. The static field strength has a strong effect on time lag [2], and the time lag is a very important factor in delaying the secondary discharge. With a short time lag, once the charge voltage reaches the threshold voltage, breakdown occurs, and the discharge current is small. With a long time lag, the breakdown is delayed, and finally the charge voltage can be high, and also the discharge current will be large; it can be larger than the IEC standard 61000-4-2 (the standard specifies 3.75 A/kV). Some researchers have investigated the effect of humidity [3] on time lag, but few have studied the effect of gap shape on time lag, which is important in products.

Effect of secondary discharge on the repeatability of contact discharge method

“…As the applied voltage increases, the mean and variance decrease, but it is not decreased linearly. The more the applied voltage exceeds the DC breakdown voltage, the more electrons will be able to initiate a breakdown, then the time lag is shorter [4, 5]. However, as the applied voltage increases to an even higher value, the time lag decreases to a constant value which is a formative time lag.…”