Electrostatic Discharge and Workbench Safety

PCBs are strong, but the devices that we place on them can be fragile. Learn about basic workbench safety when working with your first PCBs.

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Audience:

What is ESD and How Do I Protect Against it?

What is ESD?

Electrostatic Discharge (ESD) is miniaturized lightning and it can permanently damage an integrated circuit without leaving a trace of evidence about what went wrong.  

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When your circuit and body are at different electrical potentials, charges can jump from one object to the other, creating  microscopic damage that can lead to shortened life-span, or immediate product failure.

ESD is the result of static charge accumulation on one insulated object suddenly moving to a new object, usually by ionizing nearby air molecules.  The charge usually accumulates due to the triboelectric effect – the exchange of electrons between two dissimilar insulators (air, cotton, wool, polyester, etc…) as they rub against one another.  Any relative movement (sliding, lifting, rotating, peeling) between the two insulators can cause charge accumulation.

Triboelectric charging can occur when any relative movement occurs between two insulators (translational movement, increased separation, rotation, peeling, etc...)

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As excess electrons accumulate on an object, the amount of overall energy increases – and if those charges find a way to move through your sensitive electric circuit, they can and will destroy it.  It is possible (under certain circumstances) for insulators to accumulate charge deposited by air currents.


If you have ever received a shock when touching a doorknob, you were likely exposed to tens or perhaps hundreds of thousands of volts (The energy needed to jump a 1 mm gap is well over 30,000 V!)

How do I protect my projects from human-caused ESD?

The secret to dissipating static electricity on objects is to make them conductive – charge will not accumulate on a surface if it is given an electrical path to an earth-ground.  At home, you might run a copper wire or strap from your workbench to a cold-water pipe that passes through the concrete slab into the ground. Alternatively, you might run a wire outside and connect it to a “ground-rod” that you’ve driven at least a meter into the soil.


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Make your work-area conductive to dissipate electro-static charge, but not so conductive that it could allow electrocution.

Use an “ESD-mat” on your workbench and an “ESD wrist-strap” around your wrist. Connect both the mat and your wrist to earth ground before you begin to work with your new PCB.

 
 

This image of a technician working with a wrist-strap on an ESD-safe workmat is from mul-t-mat.ca


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The mat and wrist-strap devices are made from a high-resistance conductor, so if you do happen to encounter a high-voltage source, you won’t be electrocuted.  You can take things a step further and invest in an “ESD coat” and “ESD tools.”  But you’ll likely be just fine with the wrist-strap and mat unless you are working with extremely sensitive components – which you likely won’t be doing at home.

The next article in our series will teach you how to use diodes to protect your circuits.

If you missed the last article on Reverse Polarity Protection Diode, click here!

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