Types of ESD/ESC Relevant Materials
There are three known types of materials which are considered to be relevant to ESD events, where they have a direct influence on the way charges are dissipated off bodies, and on ESC, where the materials have relevance
regarding the way charges are allowed to accumulate on bodies.
These are materials showing a very low electrical resistance where electrons will move fairly freely in any given direction over the surface or across its bulk. Because of this freedom of movement of electrons once a conductive material is charged their distribution is fairly uniform and charges are themselves reallocated more-or-less equidistant from each other. Should this conductive material become in touch with another conductive body there will be a quick transfer of electrons in between the bodies as aiming to achieve neutrality, however should a charge polarity still remain on both touching bodies and an earth is attached to any part of the two bodies, then there will be a quick movement of the excess or lack of electrons in between the bodies and earth as to achieve natural equilibrium.
|Static Dissipating Materials
These materials have an electrical resistance in between an insulative and a conductive material there still will be a flow of electrons from one body to another but the speed of the flow of electrons will depend of the resistance of the material, on the surface or across its bulk. The transfer of electrons in between two bodies will be slower than the conductive but it will be less damaging.
This material inhibits the passing of current due to their high electrical resistance on the surface and their bulk. Charges can easily accumulate on insulators as electrons cannot move around and find dissipating paths, they may stay there for a long time as the only way to dissipate them is naturally through the ambient air or by applying some technique to allow this to happen eg painting the body with dissipative metallic paint and then grounding it. Is not unusual for an insulative bodies to exhibit both positive and negative charges co-existing in some proximity.