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I like the aesthetic of clear acrylic mounting of PCBs and I want to use it for a project I'm working on. For example as seen in the Mighty Ohm Geiger Counter,

mighty ohm case

Is esd something I should worry about? The project like the Geiger counter above will be handheld for use.

Also somewhat related, is it safe to use plain old rubber foam as padding with regards to esd (where the rubber foam would be in direct contact with traces and maybe some components on the PCB)? And what about as a substitute for rubber bumpers?

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ESD should always be a concern with sensitive devices. I've seen plenty of uControllers act seemingly normal but have peculiar behavior, in the end to find it was ESD damage.

Typically transient suppression devices (aka tranzorbs) are put on signals that come in from a connector (especially communication signals, not power).

It's good that you're thinking about static from the foam and the acrylic.

Typically you will receive PCBs in a esd static free foam like this. Or more commonly within an esd bag.

I don't think the acrylic will be much of a problem. Although I do believe it retains a charge sort of like a balloon, so as long as the potential isn't enough to bridge the air gap to a trace/pin, it should be okay. Similar deal with plastic.. And we've all seen plenty of devices in plastic. (You would have to try really hard to do this, more likely you will absorb the charge on your person and discharge it elsewhere).

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  • \$\begingroup\$ Now that you mention I do see an awful lot of electronics in plastic cases! So the purpose of cases is mainly to prevent things like moisture, mechanical stress, unintentional shorts, look/feel pretty etc. But not esd protection... That is, esd is a non-issue for most projects? What then counts as a sensitive device? RaspberryPis and Arduinos are often used out in the open... so they don't count as sensitive? \$\endgroup\$ – Jet Blue Sep 14 '16 at 23:48
  • \$\begingroup\$ The case provides a physical barrier between different potentials that may cause damage to the device. But the case will not protect against ALL unintentional shorts (FOD or tin whiskers). Its not that it's a non-issue, It probably doesn't get the attention that it should. Probably rightfully so, things like toys probably slack at esd protection because who cares, they can buy another one? Whereas cars and industrial equipment will have it because it may provide a safety risk. \$\endgroup\$ – klamb Sep 15 '16 at 13:35
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    \$\begingroup\$ I believe IEC 61000-4-2 is the standard most commonly used for ICs. The device is considered more susceptible to esd damage if it's esd class i and less susceptible to esd damage if it is class iv. I consider uControllers extremely susceptible from personal experience. If you contact one of the signals that doesn't have esd protection, it can potentially damage the device. The raspberry pi schematic I looked at uses BAV99 and rctamp0524p as it's protection devices. So it is safe from some handling. But depending on where and how much esd is applied, the device can be damaged. \$\endgroup\$ – klamb Sep 15 '16 at 13:35

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