Continuous Monitoring in ESD ControlSophie Hunt
It is well known that wrist straps are considered the first line of ESD control. However they need to be visually inspected and checked periodically, while being worn, before handling any ESD sensitive items to warn the operator of any fault which would lead to no longer being grounded.
Periodic testing versus continuous monitoring
The downside of periodic testing is that there is no way of knowing when any fault occurred between testing. For example, a wrist strap can pass a test at the start of a shift, work is carried out on ESD sensitive items. Two hours later, after a break, the same wrist strap is tested again but fails. Has it just failed? How many devices could be damaged that were worked on before the operator’s break was discovered? Latent defects are not visible and failures may only occur at any time. A good alternative, therefore, is to use a continuous monitor.
As specified in the ESD Handbook TR 20.20 paragraph 188.8.131.52.4 Test Frequency, “Because wrist straps have a finite life, it is important to develop a test frequency that will guarantee integrity of the system. Typical test programs recommend that wrist straps that are used daily should be tested daily. However, if the products that are being produced are of such value that knowledge of a continuous, reliable ground is needed, then continuous monitoring should be considered or even required.”
What are the benefits?
Our continuous monitoring devices are designed to sit below your work station and are used to ensure that the user’s wrist straps and a single ESD work surface are functioning correctly. In contrast to periodic testing, these devices provide instant feedback on status and functionality of the wrist strap. This avoids the risk of damage to ESD sensitive items which would otherwise only be detected once products have been manufactured, potentially leaving companies with unhappy customers.
If a malfunction is found, the unit will signal the fault giving both visual and audible alarms identifying the users(s) and/or the failing work surface instantaneously. Not only does this help to reduce or eliminate ESD damage but other benefits include removing the need to maintain daily test logs and reduced time spent on testing wrist straps. This, in turn, reduces production costs at the same time.