Static Electricity in Lab - Page 1
Forum section: electronics / beginners

author: eev_carl
author_rank: Regular Contributor
timestamp: April 13, 2018, 06:52:25 pm
content: Hi,I have a carpet in my setup and every once and a while I get a static shock when I touch a part like an LED lead on the breadboard. I have some CMOS ICs that I don't want to damage. Should I use a wrist strap or special mat to eliminate this?If you suggest the wrist strap, what should I hook the wire part to? I have a scope, power supply, and a function generator in front of me.Thanks,Carl

author: nanofrog
author_rank: Super Contributor
timestamp: April 13, 2018, 08:06:09 pm
content: A 2 layer rubber ESD mat and a wrist strap would do (both tied to ground; cords contain a 1M resistor). As to where to actually connect the cord, it's usually attached to the screw that holds on a receptacle cover on a grounded outlet (make sure the paint is removed from the underside of the screw). This way you're ESD mat is grounded whether or not any equipment is plugged in (wrist strap too when it's plugged in).For mats, I'd suggest looking at a particular eBay store,canvu0_0(I'd suggest a kit as it comes with a wrist strap and appropriate cable;example). He's the least expensive source I'm aware of. If you don't see the size you need, he'll do custom sizes. Different colors as well as either smooth or textured surfaces.

author: Eka
author_rank: Regular Contributor
timestamp: April 15, 2018, 02:25:47 pm
content: OK, so i wrote a book.TLDR- choose a location without carpet, and wear 100% cotton clothing.- Wrist straps and a 2 layer ESD rubber mat is best. Vinyl ESD mats are not solder safe. Silicone mats are not ESD safe at all.- A conductive surface like metal can be used instead of a proper mat, but has it's own issues and needed precautions.- large cookie sheets make good easily setup portable work surface if a dedicated work space isn't possible.What the material is used in the carpet, upholstery, and the clothing you wear is important. Synthetics, wool, and silk easily build up charges so you constantly end up zapping your chips as you are working on them unless you are grounded with your wrist strap. Changing the upholstery and carpet can be hard or impossible, but choosing a different location or different clothing is often possible. If I have a chance I will change into 100% cotton clothing before doing electronics work and I still use my wrist straps. Cotton builds up much less charge as one moves about.Yes, use a wrist strap, but it does little good if the work surface isn't also tied to the same ground as the wrist strap. So tie all the earth grounds on everything to a common ground point which is then connected to earth ground. Keep the lengths of ground wires as short as reasonable. For years I used 0.25" quick connect terminals on the ends of all my earth grounding wires. They are much cheaper than banana plugs, but are much harder to plug in and unplug. For portability I have a three prong plug with only the ground wire connected. If you use the same method, test the outlet you plug it into first with an outlet tester to make sure the ground is really ground, and not floating or have live AC on it.As already mentioned by nanofrog, 2 layer rubber ESD mats are the way to go for a work surface. There is some variance in how high of heat they can handle, and how durable the surface is, but I couldn't tell you which brand is best. The vinyl mats are cheaper, but only good for assembly and disassembly. They don't have the heat handling to handle dropped solder balls or soldering iron tips. The silicone soldering mats are insulating and NOT ESD safe, and will build up static charges if rubbed. Even the ones that say they are ESD safe are way to high of resistance to be ESD safe. Silicone is just too good of an insulator. They do have their uses when working with high heat like a hot air rework station, but bear in mind they are not ESD safe. Don't slide your components or boards across them. That will build up a static charge on their surface. I also would not disassemble a phone or laptop on one like many sellers say they are good for.Not have enough money for a proper ESD mat? For many years I soldered on a large cookie sheet I dedicated to that use. My ESD wrist strap was wired to a bolt through the hanging hole. I'd put all my parts onto the cookie sheet while sill in their ESD protective bags, and let them equalize for a few minutes before unwrapping. That is very important. The problem with a metal surface like a cookie sheet is it will drain static at electric shock speed, and that can blow a chip if set down on it without allowing equalizing to happen. This is why the top layer of a 2 layer rubber mat is static disipative, not conductive. Through being careful to always do the equalizing, I never killed a CMOS chip, and this was in the bad old days of the late '70s and early '80s when CMOS chips were much more sensitive to ESD than they are now.I have since gotten proper two layer rubber ESD mats to cover my cookie sheets. I bought a 2' x 10' roll and cut pieces for them. I think DigiKey has the snap terminals for around $4 each in a screw attachment version. I don't use them. To form a post to attach the ground wire to the mats I use machine screws with nuts clamping fender washers on both top and bottom of the mat. I then use a thumb nut to hold a wire with ring terminal end onto the resulting post. I get as good of electrical contact with them that the snap terminals have, plus they are not likely to accidentally come undone. Also, excluding the thumb nuts, I had all the parts on hand.The cookie sheets with ESD mats on top are great because I can pick them up and set them onto a shelf relatively quickly without disrupting the laid out parts, tools, instruments, etc on them. My work area is then clear to work on a different project.My electronics cookie sheets are now all Vollrath #68085 heavy gauge aluminum with mildly turned up ends, and flat along the long edges. It would be better to use stainless steel, but it costs much more. I've thought of making some 24" wide by 18" deep ones (60cm by 45cm) so I have a bit more working room. I'd have to borrow use of a metal break so I can turn up the side and back edges, or have a metal fabricator make them. For the machine screws I used hex socket head machine screws because they are smoother and less likely to damage surfaces they are in contact with. Next time I'd use bevel headed machine screws, and countersink them into the aluminum sheet so they are flush. I also glued 4" wide strips of thick heavy felt to the bottom along the ends to help prevent damage to my tables, and keep fingers from contacting the aluminum which oxidizes over time.

author: jpb
author_rank: Super Contributor
timestamp: April 15, 2018, 02:45:01 pm
content: Quote from: Eka on April 15, 2018, 02:25:47 pmFor doing things at home this is a little tricky.My new study/electronics lab already has a carpet which is fairly new.I have wondered about replacing it but this is not a commercial lab so what ever I replace it with has to be domestic flooring of some sort - the options seem limited.1.) Wooden flooring - nice but expensive and worst still requires regular maintenance which would involve shifting furniture once or twice a year at least. For my < 3m x < 2m room the first quote I got was something like £700 ($1000)!2.) laminate flooring - ok, though not as nice as wood, but this has a plastic surface so is probably not particularly ESD safe anyway.3.) tiles - I quite like these but not really for a study and we don't have under floor heating so they would be pretty cold in winter.4.)ESD vinyl flooring - expensive and ugly for a home (in my view) at least in a living area (ok-ish if it was a kitchen maybe).5.) There are ESD carpet tiles but these have to be glued down and I don't want to fit flooring that will be difficult to replace in a few years time.My current thoughts are to spray the carpet, perhaps get an ESD floor mat to go on top of where I sit, use a bench mat and wrist-straps and perhaps get an ESD safe chair to go on the floor mat.But if anyone has an idea of a good flooring material that is both ESD friendly but also would look good in a home study I would be interested to know.

author: nanofrog
author_rank: Super Contributor
timestamp: April 15, 2018, 07:12:25 pm
content: FWIW, I've carpet in my lab (replacement ATM is not an option). Although I've not done it, one trick that helps prevent ESD buildup is to spray it with fabric softener.My basic ESD setup consists of what I mentioned above (2 layer rubber ESD mat + aDesco 09187metal wrist strap).I took it a bit further later on with awrist strap touch tester, followed by amini workstation monitor(both NOS I got cheap on eBay).

author: SeanB
author_rank: Super Contributor
timestamp: April 15, 2018, 07:35:14 pm
content: Quick and cheap fix for the carpet is to first give it a thorough vacuum, then get a spray bottle, and use a diluted mix of liquid fabric softener to mist the entire carpet, giving it enough to be damp to the touch. Then use a clean soft broom to spread the liquid all through the pile, and leave to dry. Will reduce the static build up for a while, till it wears off, then simply redo the spray, or do it weekly after you vacuum the carpet.

author: JTY
author_rank: Newbie
timestamp: April 15, 2018, 09:11:24 pm
content: As others said, wrist strap and ESD mat. Connect both to a ground block, or grounding adapter that is connected to your home's electrical ground. Ideally, your mat, strap, and equipment will be grounded at the same outlet to ensure they all have the same potential. Personally, I use an old rackmount PDU (power strip) as it has a ground lug on it, so I can connect my strap + mat to the lug, and then plug my equipment into the PDU.

author: Eka
author_rank: Regular Contributor
timestamp: April 17, 2018, 02:30:26 am
content: Quote from: jpb on April 15, 2018, 02:45:01 pmSo your kitchen floor is carpeted?* In the past I often worked at the kitchen table. I just made my setup easily portable using the large cookie sheet trays so I could quickly put it away at meal time or at the end of the day.Even though I now have a dedicated studio space in my home, there isn't a bench or table in it dedicated to electronics work because I sometimes do dusty/messy stuff in there and the studio isn't large. All my electronics gear would be covered in dust if I left them out. So I still use the portable trays on the benches in the studio. I just store them away before I do messy stuff.* I actually grew up in a house with a carpeted kitchen. I wouldn't recommend it, unless it is an industrial carpet made for high traffic areas.

author: GreyWoolfe
author_rank: Unknown
timestamp: April 17, 2018, 01:10:26 pm
content: Quote from: Eka on April 17, 2018, 02:30:26 amGood Lord, that ranks up there with carpet in the bathroom--nasty, especially with messy cooks and grandchildren who drop food and drink on the floor in the kitchen regularly. My office is an add-on at the back of the house that was formerly a patio so I have bare a concrete floor. Workbench has full length 2 layer rubber ESD mat connected to the ground terminal at an outlet. Easy, peasy, lemon squeezey as Dave would say.

author: sairfan1
author_rank: Frequent Contributor
timestamp: April 17, 2018, 06:33:53 pm
content: Just wanted to know, does wireless wrist straps also works good for static discharge? thanks.

author: Eka
author_rank: Regular Contributor
timestamp: April 17, 2018, 06:52:43 pm
content: Quote from: sairfan1 on April 17, 2018, 06:33:53 pmI don't see how they could work. How do they know the voltage potential at your bench? How do they get rid of static buildup?

author: nanofrog
author_rank: Super Contributor
timestamp: April 18, 2018, 12:22:10 am
content: Quote from: sairfan1 on April 17, 2018, 06:33:53 pmNot in the slightest. You need a resistive ground path to discharge the static electricity at a rate it won't destroy sensitive electronics (aka a wire + 1M resistor). Air doesn't do that.

author: Unity
author_rank: Newbie
timestamp: September 01, 2024, 03:27:01 pm
content: Quote from: nanofrog on April 13, 2018, 08:06:09 pmI recently purchased a 30 X 72 ESD Desk Mat from seller canvu0_0Shipping was great, the mat feels great, very happy! Total cost was $98.72Item ID: 284301224543Thanks nanofrog!