A couple of questions on ESD and ESD Safety

General Electronics
1

Hi,

Ideally, I’d like to use my computer desk for electronics work and have complete ESD safety when working with electronics, without necessarily having to dedicate a separate part of the room for just electronics work/ESD safety and without having everything be ESD safe. Also, I am trying to understand more about ESD so I can hopefully reach a point where I can answer my own questions and know what would happen in various scenarios without having to ask someone about every single thing.

So, here are the questions I currently have, or at least those that I can currently remember:

  1. Obviously, constant monitors are the best way to monitor the grounding, but most articles and products recommend grounding everything and your mother. I mean even my solder reel stand has a post. So, if you do ground everything, are you supposed to use constant monitors for everything, or should you just do constant monitoring on your strap and mat?

  2. I’ve heard that the equipment (like the strap and the mat) are supposed to be grounded using star grounding. Why is that?

  3. Let’s say you have a large unpainted pipe in the building that goes straight into the earth and you are going to use it for grounding. In star grounding - is everything that’s being grounded supposed to go to the pipe on its own, so everything meets in a star there or can they all meet together before that pipe and then go as a single wire to ground? Like where is the star part in star grounding supposed to be?

  4. I will be buying myself a constant resistive monitor with a double wire grounding strap and a mat. The strap plugs into the monitor and is both monitored and grounded by it, however, the mat is only being monitored by it and it’s recommended you ground it on its own via one of its other corners. I’d be doing that by one of those grounding plugs, that you plug into the outlet. Isn’t this different from star grounding? I mean you are grounding the monitor and it grouns the strap - that sounds like a connection in series? Also, I’d be plugging the monitor and the ground plug for the mat into a power outlet strip. Again, isn’t this different from star grounding? I mean they both meet into the ground of the power strip then that goes to wall outlet’s ground

  5. Are all fully metal tools inherently ESD safe if you are grounded while using them and when putting them down while still working with electronics, you put them down on a grounded ESD safety mat?

  6. If the tools are all metal but don’t explicitly say ESD/ESD safe, should I replace them with ones that say so?

  7. If you are grounded, why replace things like coffee mugs with ESD safety ones? Won’t the static electricity get removed from the mug when you touch it while you are grounded (and even if you aren’t)?

  8. If you and your mat are both grounded and being constantly monitored and all your tools are ESD safe and you are not touching other stuff while working, but you have things on your desk that are not ESD safe and are plastic, but are like half a meter or more away from you. Is that ok?
    I am trying to achieve absolute ESD safety, but without going for things that aren’t actually needed.

My problems I guess is not understanding where is the line between things that are needed and things that are made ESD safe, just because of marketing.

  1. Not that I’m trying to certify my home, but I guess I am using it as a control, since certification seems to be the ultimate criteria - can you get an ESD certification without everything within reach being ESD safe (with only things you won’t be touching during work, that won’t be touching the electronics not being ESD safe)?

  2. Is there a gap between complete ESD Safety and passing ESD Safety certification? I mean like, do certifications require more than what’s actually needed for maximum ESD Safety?

  3. Why use things like ESD chairs, ESD lamp, ESD floor even? Are those just to cover various scenarios and to fit all people as opposed to making sure non ESD safe things in close proximity won’t touch the electronics?

  4. If nothing touches the electronics, is it even a problem if you touch non ESD safe things while grounded? (I think I may have asked this one already)

  5. When using ESD safe storage shelving or trays for components and the storage is grounded, should you store the components in insulating bags? I mean since the storage is conductive, if the component leads are touching the storage and the storage gets zapped with ESD, won’t this still fry the component even if the storage has lowest resistance to ground?

  6. How far is too far when it comes to ESD safety? Like if you are designing a PCB that connects with a cable to a USB daughter board and the cable is on the underside and you have a plastic housing - Do you/should you worry about ESD safety then? Are there even ESD safe cables? Should you make the housing ESD safe? Like generally, where is the point between where/when you have to actually worry about ESD and protect against it, and where/when you don’t have to worry about it?

  7. I guess, if you have the ability, just making the whole room ESD safe is easier than figuring out how much is enough. Is that really why at certain places everything is ESD safe?

2

A lot of questions :blush:

First, what are you actually doing?

Hobby stuff, prototyping, industrial production or space rated builds?

If it is the first two, forget about ESD except maybe a ground strap for your arm

I have been doing electronics for 25 years and very seldom use a strap, - - and have never had an ESD issue

If your design cannot handle a small ESD event, then in my opinion the design is not robust

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As for the grounding. Your pipe into the earth is probably good, if it is only used for ESD (a pipe is not allowed if this is a professional setup)

Add 1M ohm resistor in series with each ESD protected unit. That’s for safety so not to electrocute you in case of a fault. The resistor needs to be approved safely device, so a standard leaded is not ok (protective impedance as defined in some standard I cannot remember the name of)

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4

What Klaus said. I’ve been doing this professionally for over 40 years and never use a strap, mats, monitors, etc.

What is important is your personal habits. It must become second nature to always touch a large metal or dissipative object when you sit down at the bench before touching any boards or components (note the discharge object does not necessarily need to be grounded, it just needs to be large and at least somewhat conductive, to absorb any charge). If you have to carry a board somewhere, carry it so your hand is touching as much PCB copper as possible, or carry it on a piece of pink foam, and touch something dissipative when you get to the destination. If you hand a board to someone else, make skin-to-skin contact with them before passing the board. Always handle an ESD-sensitive component’s packaging before touching the part. When plugging boards into each other, make bodily contact with ground on both boards before mating. And so on - this all becomes automatic and subconscious.

The straps and mats and monitors are needed only when semi-skilled labor is involved that cannot be relied on to always keep ESD in mind.

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5

What Klaus and Julia have said is good.

Climate can make a difference here. When I lived in Tennessee, ESD was mostly a non-issue due to the high humidity. I moved to dry Colorado, killed a chip (I felt it and knew exactly what happened) within the first week and picked up better habits. A humidifier can help if humidity is too low.

An ESD mat is the most important thing in my opinion, giving you a convenient place to discharge yourself and objects. The wall outlet or power strip ground is fine assuming your building is properly wired. I plug mine into the ground banana jack on the back of my solder station.

I routinely handle highly ESD sensitive microwave parts including discrete GaAs FETs with only a mat, but am conscious to make contact with the mat before touching sensitive items. I’m tend to rest my wrist on the mat when poking at circuits.

You are probably not going to be able to have everything on your bench be ESD safe. I checked a handful of things on mine with a high range ohm meter. My mat measures 6 Gohm at two points about 20 cm apart. Static dissapative plastic tools were similar. The plastics on my fairly new R&S, Keithley, Keysight gear are not ESD dissapative, measuring > 1 T ohm. That includes things like scope probes and their cables. The only dissapative plastic housing I found was my JBC solder station.

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6

Personal habits are the best target. A test of how ingrained your habits are is to watch someone else do something, e.g. when visiting a client, or handing a PCBA to a relative, … and you get this strong visceral sense of disgust and realise it is because they didn’t take care to earth themselves properly.

For workspaces that aren’t always important but sometimes are, I mount an aluminium bar just under the edge of the desk, and earth that through a 1M resistor. The habit then becomes touching the bar as I drag my wheeled chair into position.

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