ESD work surfaces aid in the prevention of damage to ESD sensitive items (ESDS) and assemblies from electrostatic discharge.
ESD working surfaces, such as mats, are typically an integral part of the ESD workstation, particularly in areas where hand assembly occurs. The purpose of the ESD working surface is two-fold.
Generally speaking, ESD matting offers a lower initial investment, and it is easier to replace. It is a flexible option that can be used to cover standard surfaces that aren’t conductive/dissipative. Another application is to place on top of high-pressure ESD laminates for a less humidity dependent surface.
There are two different materials for ESD matting, the first and most widely used is rubber. Rubber should be used when heat and chemical resistance is a requirement. Vinyl mats tend to be easier to cut and there are cushioned varieties available providing better physical protection to the product.
These mats come in different constructions or compositions; these can be found below. The multi-layer constructions should be used when constant or continuous monitors are in place, as they monitor the conductive layer. Typically, multi-layer work surfaces are preferable, as the top dissipative layer prevents damage from CDM ESD events. Per IEC 61340-5-1, table 3 “In situations where charged device model (CDM) damage is a concern, a minimum point to point resistance limit of 1 × 104 Ω is recommended.” Plus, the inclusion of a conductive layer provides a more consistent resistance across the surface of the mat, and it allows an charge to be taken below the surface, through the more conductive layer to ground. Per IEC TR 61340-5-2, section 184.108.40.206.1.9.3: “Electrical resistance from point-to-point and resistance to ground are generally consistent, regardless of the distance between electrodes or between a single electrode and the worksurface’s groundable point. The controling factor is the vertical resistance through the top surface to the conductive layer.”The Different Constructions of Static Control Matting Infographic
When choosing an ESD work surface you should consider various factors as well as electrical resistance: