Comparing Antistats versus Inherently Conductive Polymer Coated Type I Moisture Barrier Bags for Humidity Dependence & Charge Generation at Low RH

This is a continuation, from the September 2010 Issue, of the examination of ESD packaging regarding Electrostatic Decay, Static Shielding, and Charge Generation. (Note: Figures and tables are noted as continuing numbers from Part 1. Full Part 2 version can be referenced at www.cemag.us)

INHERENTLY CONDUCTIVE POLYMERS
There are two different types of electrically active polymers from conductivity in an inherent point of view regardless of humidity. The first category is Inherently Conductive Polymers (ICP) which are thermoset in structure and can provide surface resistance readings from <10² – 10¹⁰ ohms depending upon the application thickness of the polymer. A second category is the Inherently Dissipative Polymers (IDP) which are thermoplastic in structure, can provide surface resistance readings in the 10⁷ – 10¹¹ ohm range, and are also dependent upon the thickness of the polymer sample.

ELECTROSTATIC DECAY EIA-541, APPENDIX F (MODIFIED) AND MIL-STD-3010A-2005
Six 4" x 6" Type 1 bag rectangles (Table 5) were subjected to a static decay test phase at +/-1000 volts to +/-100 volts in accordance with Mil-STD-3010A-2005 (Figure 8). As seen in MIL-PRF-81705D w/Amendment 1, July 14, 2004, an acceptable decay limit is 2.0 seconds, however, some organizations require +/-1000 volts to +/-100 volts in <2.0 seconds.

According to Mil-Handbook 263B, “…Decay time measurements, for an induced voltage on a given sample, may not correlate with surface or volume resistivity measurements for materials of complex construction. Additionally, decay time measurements can become complex from the viewpoint of understanding exactly how materials of complex construction, that is, laminates/multilayer materials, are performing. Each of the three test methods does not, and was not designed to meet the testing requirements of the entire range of potential ESD protective materials available…”