June 2008

If you are reading this, you probably have an idea of what ESD is. But do you know the common sources for ESD? There are three: human body ESD, machine ESD and charge device ESD.

I would imagine that human body ESD is thought of the most when the term ESD is mentioned, and rightfully so because humans probably cause the most ESD damage. Human body ESD is when a human transfers the electrostatic discharge to a part that is static sensitive. Some of the most damaging human errors include ungrounded employees walking around with static sensitive items such as PCBs, employees not wearing appropriate gloves or finger cots and employees walking around with ESD sensitive parts in open bags, bins, totes, etc… Human body ESD can be avoided with the use of a heel/sole ground or wrist strap; both are relatively inexpensive.

Machine ESD is the second cause of ESD damage. This source of damage is caused when an ungrounded part (conductive or dissipative) such as a machine or tool comes in contact with an ESD sensitive part. The solution to this problem is to simply ground the machine part, tools, etc…

The final source is charged device ESD. This type of ESD takes place when a part or device develops a charge and then comes in contact with a conductive item. Once the two parts touch there is a fast discharge which ultimately damages the ESD sensitive part. Ionizers are useful in this situation as they neutralize new charges and prevent build up of charges. Reducing movement of a part within the facility and having one common ground also helps combat charged device ESD.

Other things to keep in mind when protecting your ESD sensitive parts:

• Make sure your ESD bags and containers are not too old. Many materials lose their ESD protection over time.
• Have an ionizer? Make sure both emitters are working and make sure there is an equal balance of positive and negative ions.
• Store ESD sensitive parts in the appropriate containers. I know it seems like common sense but it’s important.

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