All the specifications and guide lines tell you what to do. But where are they when you want to know what not to do?

Electrostatic Discharge (ESD) testing is one of those hurtful tests. Watch this video and we will talk some more:

Yes, the damn 25KV stings, and when they come in a series of pulses, well it feels like you have your finger under the needle of a sewing machine! Here I used a Schaffner ESD simulator.

Of course ESD testing is an important part of design and without that everything you hold in your hands will fail miserably. Imagine picking up your phone and see it restarting just because of that, or even crossing over to the next world.

There are two ways to discharge to a unit: air discharge and contact discharge.

The air discharge is when the tip of the ESD simulator won’t touch the target, but gets close enough for the charge to arc across air to it. The air discharge is set to a higher voltage usually from 8KV to 15KV depending on the specifications.

The contact discharge on the other hand is done with the gun setup in the contact discharge configuration (the tip is a sharp cone and the discharges are stronger). The tip must touch the target and then the gun sends a discharge when triggered. The voltage is usually set to a lower level between 4KV and 8KV depending on the specifications.

Obviously the contact discharge can only be to any exposed metal on a finished product. But the air discharge can find its way through seams and gaps into the device and jump to any unwanted spot in the device.

The mechanical design of the device becomes very important in providing enough air gap to the internal electronics to avoid air discharge. After all, 16KV can jump across a one centimeter gap.

It is not always the direct discharge to the circuit that causes failures, but sometimes a discharge to a metal piece that is not even connected to the circuit can cause failure. The reason is that such a discharge can create electromagnetic waves that can disrupt the circuit.

the funny thing is that after all the provisions and improvements you add to fix the ESD issue, it might still fail, and only one strange change might fix all problems.

I remember one of my friends told me once that all he did couldn’t fix one issue, and at the end scratching the surface of the printed circuit board (PCB) fixed the problem!

Don’t forget what I told you in the video. These happened to me many times and I am sure will happen to me again. Well, I guess that’s part of the job.