Static Safe Procedures and Such - Page 1
Forum section: electronics / general

author: beaker353
author_rank: Unknown
timestamp: April 25, 2011, 03:17:02 am
content: After zapping my second Arduino in all of three months (grrrrrrr), I think a blog entry on the basics of proper static control procedures, techniques, and products would be a great thing to cover. I live in a particular area of the US were it is quite common to find inside humidity in the teens and even the outside humidity in the single digits. I find it painfully easy, literately, to build of enough a static charge just walking up my carpeted stairs to create a quite decent spark to a light switch. There are a plethora of anti-static mats, straps, ionizers, and a host of other expensive equipment with mostly slick sounding marketing jargon that just reeks of BS? What rules and procedures with a typical home lab/bench should I follow to minimize ESD damage, and what equipment is actually needed and what should I actually look for when selecting equipment? Please help us cut though the BS and tell us what works! Thanks!- Eric

author: Psi
author_rank: Super Contributor
timestamp: April 25, 2011, 04:08:39 am
content: A wrist static strap and a floor + bench static mat is probably going to give the best results.But something as simple as always touching a grounded object before touching any IC's can help quite a bit.Also storing your IC's in antistatic foam is a good idea. That way you can go to your component cabinet/draw with no static protection and pick up any IC without worrying about static. (Since all pins of the IC are shorted together you cant induce a voltage difference between pins, even if you're charged up to 10kV) Once you return to your desk, with the chair on a static mat, and wrist strap on you can safely remove the IC.You can even make your own antistatic ic foam by gluing alu foil to a thin sheet of dense foam or polystyrene.

author: beaker353
author_rank: Unknown
timestamp: April 25, 2011, 05:35:35 am
content: I was hoping to catch Dave's eye for an idea for a future video blog. That is the idea of this particular part of the forum, correct?- Eric

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: April 25, 2011, 08:40:09 am
content: Quote from: Psi on April 25, 2011, 04:08:39 amFoil on polystyrene is worse than bare polystyrene, as it creates a capacitor which can build up a charge. It's the D in ESD that can cause damage. Think about what can cause a discharge current. This is why ESD protection products are resistive and not conductive.

author: Psi
author_rank: Super Contributor
timestamp: April 25, 2011, 10:21:26 am
content: I quite often get chips from jaycar that come pushed into the stuffMaybe its not actually polystyrene then, it does looks like it though.Scratch the idea of making it yourself then.

author: EEVblog
author_rank: Unknown
timestamp: April 25, 2011, 10:22:38 am
content: Quote from: beaker353 on April 25, 2011, 05:35:35 amI have already done a blog on anti-static myths. #3 or something?Dave.

author: beaker353
author_rank: Unknown
timestamp: April 25, 2011, 03:29:51 pm
content: You did talk briefly in #3 about the difference between anti-dissipative and anti-static bags. Just believe that I'm not the only one that could benefit from a more in-depth analysis and show-and-tell of the elements and procedures of an ESD safe workstation.- Eric

author: JohnS_AZ
author_rank: Frequent Contributor
timestamp: April 26, 2011, 04:31:07 pm
content: With those humidity readings, sounds like you're a neighbor here in Arizona. :-)I'm planning on doing an in-depth ESD blog post eventually, but in the mean time here's a trick...Get yourself a mist spray bottle. Fill it with 1-part Downy fabric softener and 4-parts water then lightly mist the carpets in your work area as well as your seating (if it's fabric covered). The Downey is slightly conductive (that's how they eliminate "Static Cling" in your laundry) and will eliminate the triboelectric charging that happens when you walk across the carpet.John

author: Neilm
author_rank: Super Contributor
timestamp: April 26, 2011, 05:47:11 pm
content: One thing I have had to be wary of is the packaging of ICs. The company I work for had a problem with a reel of devices that were bought "cheap". Very many of these didn't work, or exibited problems. To cut a long story short, the investigation suspected ESD damage so we sent some off to be tested. It turned out that the packaging the chips were in was not the manufacturers original. It had been re-reeled. The new reel produced significant charges when the plastic strip was pulled of the reel and this damaged some of the chips.i had heard of fake chis before - but not fake packaging.Neil

author: Mechatrommer
author_rank: Super Contributor
timestamp: April 27, 2011, 12:22:09 am
content: i never have experience with zapping silicon. even if i accidentally forgot to de-static myself. i read about women can easily zap silicon since they usually wear fancy aesthetic material (fur, syntethic plastic leather etc i forgot the name), so as general rule imo, avoid those material when you are outside the lab. though this thing (esd protection) is necessary, here's my "to do list" about this matter... a solid metal/copper connected to earth ground at:1) foot pad on every door step into my lab (since we dont wear shoes into house/lab)2) in front of workstation in the lab (i can periodically intimately touch that pad)i kind of dislike the wrist band esd idea. i think i dont want it strapping me the whole time while i'm working, and make difficult to go around. my 2cnts.ps: my favourite?... cotton!

author: JohnS_AZ
author_rank: Frequent Contributor
timestamp: April 27, 2011, 04:26:54 am
content: People have to remember that ESD risk isn't the same everywhere.Today, here in Arizona, the temperature is 80F, the relative humidity is 4%, and the dew point is 3 degrees F.You can practically generate a charge by just thinking about it.

author: Mechatrommer
author_rank: Super Contributor
timestamp: April 27, 2011, 06:10:17 am
content: i guess we are blessed to have as high as 95% RH here, temp about the same.

author: beaker353
author_rank: Unknown
timestamp: April 27, 2011, 06:20:50 pm
content: John, try a bit to the north and west, where the bars never close, Las Vegas. Due to the unique environment of my day-job, the humidity stays pretty high year round so I don't have a problem with charges staying built up. However, my home bench is another matter which is where the unintentional equipment murders have occurred. My initial guess that a static dissipative mat with connected wrist strap tried to building ground is a simple and relatively cheap place to start. However, this doesn’t take care up charges building up on non-conductive materials, like the insulation on breadboards or such. They make ionization fans that put out a stream of negative and positive ions to help balance out non-conductors in their air path. However these boys are pretty pricy at $400 compared that even a top quality mat and wrist strap sets me back less than $100. Are these really necessary in super dry and static prone environments and are there other options that cost less?

author: JohnS_AZ
author_rank: Frequent Contributor
timestamp: April 27, 2011, 06:50:17 pm
content: Ionizers work, and work very well, but they are a bad idea for a hobbiest space. Not only because they are quite expensive, but because they have to be maintained. On a regular basis an ionizer needs to be measured to ensure its output is balanced. This requires a "charged plate analyzer" and a decay timer, a couple pieces of gear that almost no hobbiest owns. When an ionizer goes out of balance it actually CHARGES the work surface and everything on it.The absolute #1 weapon in fighting ESD is the wrist strap. It actually performs two functions; First, it prevents the operator from accumulating any charge through moving around and/or working on the bench. Second, it provides a safe path to ground (through a 1meg series resistor) to dissipate any charges that the person may encounter while picking up parts and tools, using equipment, whatever.A benchtop mat is also a great prevention device, but not nearly as important as a properly grounded wrist strap.I feel pretty confident in saying that the failures you are experiencing are due to not wearing a wrist strap. I wouldn't worry much about the breadboard insulation and such.One other thing you CAN do, where possible, is to make sure the circuitry you are working on is also grounded. Even if it's battery run, a little clip lead tying the neg rail to a real earth ground will prevent your circuit from floating up into the dangerous (ESD wise) voltage range.

author: beaker353
author_rank: Unknown
timestamp: April 28, 2011, 02:10:51 am
content: Thanks for the information John. Glad to hear that ionizers aren't a necessity, especially at the price points I've been finding. I assume the 1M R in series to ground allows for a safer gradual charge balancing. Would you recommend the same 1M R in series for the circuit ground you speak of, or a direct low R connection. From my work with audio equipment, minimizing the resistance from circuit ground to building/safety ground is an industry standard. Does that translate to this situation as well?- Eric

author: JohnS_AZ
author_rank: Frequent Contributor
timestamp: April 28, 2011, 03:24:48 am
content: In a wrist strap the 1meg resistor should be molded into the snap end of the cord. Any decent wrist strap will have it but if you're unsure by all means test it. The resistor is there for two reasons. First and most importantly is limits any current through your body to ground in the event you touch a live circuit. It is a life saving safety feature. Secondly, if you do come into a contact with a static charge the resistor limits the current at which the charge dissipates.Remember, voltage can NOT harm an electrical device. It's the current when a charge moves into, out of, or through an electrical device that does the damage. The resistor limits that current to safe levels for most all devices.An interesting aside: In -insanely- dangerous environments sometimes zero-ohm wrist straps are used. An example would be a plant I used to audit that manufactured the initiators for automotive airbags. Essentially, a small electrically detonated bomb. At those work stations almost all of the equipment was air drivin, and nothing was allowed that ran on more than 12VDC.

author: Mechatrommer
author_rank: Super Contributor
timestamp: April 28, 2011, 04:34:22 am
content: thanx for the info John on 1Meg Ohm. an addition to my plan.

author: JohnS_AZ
author_rank: Frequent Contributor
timestamp: April 28, 2011, 04:36:14 am
content: Oh, should have mentioned, do -NOT- use the 1meg resistor in the line grounding your benchtop mat. That material is already internally resistive, and doesn't need it.

author: beaker353
author_rank: Unknown
timestamp: April 28, 2011, 04:58:46 am
content: Should the equipment/circuit grounding tie also incorporate the 1M R, or just a direct connection?- Eric

author: Mechatrommer
author_rank: Super Contributor
timestamp: April 28, 2011, 05:16:49 am
content: i think the idea is to limit the current. i guess benchtop mat is sometype of rubber with Meg Ohm of self resistance, hence no need another R at wire connection. but if its a pure copper line just as you describe, then it should beput with the 1MOhm(shortedEdit: see John's post below) before ground connection.

author: JohnS_AZ
author_rank: Frequent Contributor
timestamp: April 28, 2011, 05:15:44 pm
content: Nope, equipment should have hard grounds. That is, zero-ohm connections to ground. The only thing that get's the 1meg resistor is the human operator.