It is very important that all people in working in an ESD protected area do not cause static to be generated and transferred to the electronic components and assemblies.
The use of ESD or antistatic clothing is key to this. It is able to dissipate the static and prevent it being transferred to the electronic components and assemblies.
Items of antistatic clothing that are available include:
- Antistatic overalls & coats: Many people wear clothing that easily generates and retains static electricity. An ESD coat covering all clothing will tend to dissipate any static that might otherwise reach any electronics equipment. It may also provide a form of shield against any induced static. With many clothes made from man-made fibres, high levels of static can build up. Ties worn by men are a very good example. These are often made from synthetic fibres and very high levels of static can be carried by them. A further danger is that they can easily reach sensitive electronics equipment when being worked upon at a bench. Typically a resistance of between 1 x 105 to 1.0 x 1011Ω should be seen when tested according to ESD STM 2.1
- Antistatic shoes & shoe straps: People themselves easily build up charge as they move around, walking from one place to another. There are several solutions available for users:
- ESD shoes: It is important to ensure that shoes do not build up static and cause the operator to become charged with respect to ground, and hence the overall EPA. Shoes providing a leakage path to earth should be used. A resistance of <1.0 x 109Ω should be exhibited when tested to ESD S9.1.
- ESD shoe covers Another alternative is to use an ESD shoe cover that fits over the operator's own shoe and provides a leakage path to earth. However care must be taken when wearing these ESD shoe covers as they may form a trip hazard.
- ESD shoe straps: Many people will want to use their own shoes and therefore an alternative to this is to use a shoe strap that fits over the operator or users shoe and provides a leakage path to earth.
Note: values for resistance and test methods are defined in ANSI/ESD S20.20.
It is worth noting that it may be necessary to re-spray the antistatic cots and overalls so that their static dissipative properties are retained. This antistatic spray for clothes can be obtained from suppliers as required.
Using antistatic clothing is an important element of any ESD protected area. The ESD clothing helps prevent the build up of static and also enables any static that can occur to be dissipated and kept away from any electronics items.