Wednesday, April 02, 2008

Is a foot strap adequate?

When my floor is dissipative do I need to utilize a foot strap and a wrist strap, or is a foot strap adequate?

If you are handling ESD sensitive electronic components within an ESD Protected Area , then you body needs to be grounded with a resistance to ground less than 35 M ohms. If seated, this must be achieved using a wrist strap because you may take your feet off the floor, and grounding contact would then be broken.

If handling ESD sensitive components while standing, grounding can be achieved through footwear and flooring if the floor and footwear resistance is low enough. To achieve this, you may need a floor which has resistance-to-ground less than 35 Mohm as well as footwear which is less than 35 M ohm. You should wear two foot straps - one on each foot. If the resistance from body to ground when grounded by footwear/flooring is not < 35 Mohm, it may be advisable to wear a wrist strap to achieve < 35 Mohm.

ESD packaging

We are receiving Diodes, Resistors, etc. from our warehouse in non-ESD bags. I was taught that these should be in ESD packaging. Can you send me information on this?

Diodes are semiconductor devices and are normally packaged in ESD protective packaging. Some diodes are quite robust and others may be very ESD sensitive, and so the ESD risk depends on the type of diode.

Usually the main problem with putting resistors and other non-ESD sensitive components in non-ESD packaging is that the non-ESD packaging is then taken into an ESD Protected Area. The non-ESD packaging is an ESD generator and can become an ESD risk to any ESD sensitive components that are present. So, if packaging is required for any components taken into the EPA, it should normally be ESD packaging.