Electrostatic discharge comes from a variety of sources. The most common sources are synthetic materials such as Styrofoam and human skin. Electronic devices quite often build up static electricity through contact with a different material (triboelectric charging) or by the influence of other objects that have different positive or negative charges (electrostatic induction). Humidity and temperature changes often contribute to the buildup and sudden release of static electricity. Sensitive electronic equipment can be irreparably harmed when exposed to ESD.
PROPERTIES OF TRANSPORT BOXES
So what do you need to know in order for you to transport your sensitive equipment safely? The first thing for you to understand is the properties of the boxes you will be transporting your equipment in. You should check;
• Grounding-Isolative materials hold static electricity longer than non isolative materials, and are very difficult to ground. Remember ESD sensitive equipment needs to be grounded properly to avoid static electricity. Simple human touch can trigger static electricity.
• Anti-static-Material that prohibits triboelectric charging to occur due to rubbing or contact with other material. Synthetics like rubber or Styrofoam induce static electricity more than polyethylene.
• Dissipative-Material that slowly releases electrical charge. Most objects have some dissipative qualities in them. The object is to find polymers that hold up under stress and lose their anti-static properties slowly.
• Conductivity-Material that allows electrical charges to flow freely through materials to the ground or to another conduit. Material that is conductive is very easy to ground.
All ESD compliant packing material, including tote boxes should have at least three of these properties to comply with international standards for shipping sensitive electronic equipment. The second thing you need to understand is the resistivity of the transport box you will be shipping your sensitive equipment in. Resistivity is simply how the transport box reacts to electric current in a positive or negative way. For example; materials with low resistance to electrical current are less likely to create an electrical spark or ESD event.
RULES FOR AVOIDING ELECTROSTATIC DISCHARGE
There are three rules to remember if you want to avoid electrostatic discharge with your sensitive electronic equipment.
1.Eliminate static generating materials-wool, synthetics are major static producers
2.Shield static sensitive parts and assemblies by utilizing ESD compliant packing materials
3.Ensure a safe path to ground to prevent accumulation of electrical charge.
ESD boxes and containers should have certain electrical, chemical, mechanical and value added characteristics according to Raymond P. Becker, President of Conductive Containers Inc. The electrical qualities are probably the most important with chemical composition coming in a close second. When selecting the correct ESD box, you must make sure the chemical composition of the container material doesn’t interact unfavorably with the material you are shipping. Mechanical considerations do need to be addressed such as durability, size and style. How the container will be handled and whether or not it will be in a controlled environment is a factor in the style and type of ESD container you’ll need. If you adhere to the three rules for avoiding electrostatic discharge, you’ll have a better chance of saving your sensitive equipment. For more information for beginners, please see this article http://www.esdjournal.com/techpapr/eosesd/container/contain.htm.