How to protect electronic components and machines from electrostatic discharge

January 31, 2019 | 09:00
Author: Tom Westcott, Head of Quality and Legislation at Distrelec

Electrostatic discharge (ESD) may seem an unnecessary overhead when building electronic equipment. If neglected, however, it can lead to serious quality issues that can arise days, weeks or even months after the product has reached the customer. Here, Tom Westcott, Head of Quality and Legislation at Distrelec, explains how considering the risks and challenges associated with ESD in advance can both prevent failures out in the field and enhance the overall quality of the assembly process.

Causes and consequences of ESD
ESD can have many different causes, which can be quite unexpected. For example, charges can build up on rolls of tape or tape dispensers and be up to a few thousand V. The main reason for this is that such objects are usually insulating, which can allow a charge to build up. Even plastic bags containing electronic components can lead to a static charge that can range from a few hundreds to over 1,000 V. If discharged through semiconductor components, this can cause a number of problems.
A high enough induced current, for example, can cause a breakdown in the semiconductor junction, and this risk is ever greater for the latest high-performance parts built on 10nm and 7nm processes. These have gate oxides that are a few nm thick and, while they operate at low voltages, they are even more susceptible to damage from high voltage ESD pulses.
Even if there is no immediate failure, the junction can be weakened, as the current pulse breaks down the oxide layer. This is likely to shorten the lifetime of the part and lead to a failure in the field or shifts in key parameters, from switching speed to the power consumption.
A high discharge can also burn through insulation and create shorts in the metallisation of all kinds of parts, not just the semiconductors. This reduces the real mean time between failure (MTBF) of the module or sub-system, in comparison with the calculated value, and, again, can cause early failures in the field.
Machine ESD is also a cause of ESD damage. This happens when an ungrounded part of a machine or tool comes in contact with an ESD-sensitive part during assembly and is sometimes overlooked.
A third source to keep in mind is charged-device ESD. This happens when a part or device itself develops a charge and then comes in contact with a conductive surface. The fast discharge that follows can then damage the ESD-sensitive part.
Next page 1/3
Loading comments...
related items