This paper will discuss static protection provided by various materials that are anti-static, static dissipative, and conductive in nature. Electrostatic charges are induced by three methods: electronically manafactured charges, (HBM) human body model charge generation, and triboelectric charging by contact with non-conductive materials.

Non-conductive materials (restivity above 10**13 ohms per square) will ALWAYS charge (and hold said charges) when induced by any of the three methods named above. These static charges will slowly bleed off to the ambient atmosphere at a rate directly proportional to the relative humidity. Due to the ease of charge generation of these materials, presence in clean rooms or in the area of ESDS (Electrostatic Discharge Sensitive) devices is contra indicated. (Increased static decay rates of these materials may be accomplished by using air ionization devices.).

Anti-static materials (restivity between 10**9 and 10**13 ohms per square) by definition will not charge by triboelectric contact with any other materials. A static charge induced by either a static gun or HBM will be dissipated at an extremely slow rate and will not protect ESDS devices contained within the material (an anti-static bag or tote for example) because the high surface restivity does not provide a Faraday Cage. Anti-static materials are contra indicated in ESDS device areas and indeed have very limited usage today.

As one example, in the past, some companies on limited budgets had continued to use regular non-conductive totes treated with topical anti-static solutions which would "wear off" (actually bloom to the atmosphere and have to be audited and retreated on a regular basis). When budgets would allow, these totes would be replaced with new conductive totes which no longer required either auditing or treating with the topical anti-static solution.

Static dissipative materials (restivity between 10**6 and 10**9 ohms per square) by definition will bleed off static charges induced by any of the three methods named above quite rapidly and provide some measure of protection for ESDS devices, as long as the devices are above Class II in sensitivity. Containers made of these materials are normally permanent in nature and do not require either auditing or treating with topical A/S solutions. Quality Assurance inspection at the time of purchase is adequate to certify these materials meet manufacturer's specifications.

Conductive materials (restivity between 10**0 and 10**6 ohms per square) will ALL provide permanent Faraday Cage protection. Obviously, a metal tote will provide an excellent Faraday Cage but has a serious flaw. Since the restivity can be measured as less than 1 ohm, the static decay rate is much too rapid. The best material for Faraday Cage protection is carbon loaded plastic which has an inherent permanent surface restivity of 10**2 ohms to 10**6 ohms per square, providing a static decay rate of 1 to 10 mSec. As with static dissipative materials, Quality Assurance inspection at the time of purchase is adequate to certify these materials meet specifications. (As a caveat; during one audit I performed at an electronics manufacturing facility I actually checked some black conductive containers I was told were conductive-BUT WERE NOT!!)