1,000 opinions on ESD!!!! - Page 1
Forum section: electronics / beginners

author: bsahdy
author_rank: Contributor
timestamp: May 18, 2016, 04:19:52 am
content: helloi have been into DIY and electronics for sometime. i have gotten to the point where i am working on more advanced electronics consisting of MOSFETS and other (supposedly) ESD sensitive components.Untill now i have stored my parts in a regular plastic parts bin and i also made a small parts bin out of cardboard. I started to wonder was my parts ESD safe? i have the ESD strap and a small ESD mat but no ESD compartments.For the past day and a half i have looked up so much information on ESD that my brain will explode. However it seems like no one can actually make up there mind about how to actually protect your electronics from them or if you even need to!!!I think its safe to say that 50% say you dont need to worry about it just where a wrist strap when handeling them and you will be fine, and dont worry about the container you put them in there. The other 50% say that ESD is a big factor and it can damage your components really fast. Only use anti-static mats, wrist straps, and store them only in anti-static containers.this info i have got from both people that say they have worked in companies, regular engineers and hobbyist.i cant do anymore research im going crazy!i just have one question.if i was to make my own compartments what material should i use?a)cardboard (not conductive, and doesnt pick up much charge. right?)b)metal (very conductive but i will ground it with 1M resisitor so it will drain everything)c)regular plastic compartments are good.these are 3 materials that i have and can work with easily and cheaply.im sorry if this is annoying to ask . i honestly want to understand this stuff as i really do enjoy electronics. i think its time we get this finally straight.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: May 18, 2016, 04:34:33 am
content: Metal is worse than nothing at all, or bare plastic.ESD is all about the "D" i.e. you need a low impedance discharge path.Loose components are hard to damage - assembled boards are much more at risk as they have enough capacitance, and potential low-impedance discharge paths to cause significant discharge current.In a hobbyist environment - forget about it, just not an issue as long as you don't have stupid carpet materials - if you never notice static, it's not going to be a problem.In a prototyping environment it's also rarely an issue as the people involved will be smart enough to know what is & isn't a problem, and also factor risk vs.consequnces- $1000 FPGA -take care. $1 MOSFET - meh.The only exception being particularly sensitive parts like laser diodesIn a produciton environment it makes a lot more sense to take more precautions, due to a combination of lower skilled staff, and worse potential consequences.

author: helius
author_rank: Super Contributor
timestamp: May 18, 2016, 04:37:07 am
content: You seem to be under some misapprehensions about ESD. The overwhelming source of the high voltages that cause ESD are insulators. Insulators interact with other materials when they are rubbed or rolled, through the triboelectric effect, to create static charge. Only conductive materials like metals or graphite can protect against ESD, and they are the materials used to produce ESD safe boxes and bags. So, to correct your understanding, you must simply invert everything you believe about ESD: it should be very easy, since negation is such a trivial logical operation.

author: rs20
author_rank: Super Contributor
timestamp: May 18, 2016, 04:49:09 am
content: Quote from: helius on May 18, 2016, 04:37:07 amAre you replying to the OP, or Mike? It's genuinely unclear to me.

author: zapta
author_rank: Super Contributor
timestamp: May 18, 2016, 04:50:21 am
content: Quote from: mikeselectricstuff on May 18, 2016, 04:34:33 amLike this?At my hobby lab I use a metal container for the components of each project and make sure to touch the metal container to equalize potentials before touching the component. Also a ESD mat and a wrist strap, that's it. So far I didn't have unexplained component failures.

author: bsahdy
author_rank: Contributor
timestamp: May 18, 2016, 05:14:17 am
content: like zapta said that he uses metal containers to store the parts. check this post as he says that the ESD compartts he got had a metal bottom plate that was connected to gound.https://www.eevblog.com/forum/beginners/yet-another-esd-storage-question/msg932981/#msg932981Quote from: mikeselectricstuff on May 18, 2016, 04:34:33 amif i ground the metal with a 1Mohm resistor wound that work like you suggested?Quote from: mikeselectricstuff on May 18, 2016, 04:34:33 ami have carpet floor but under my desk where i sit i put some shower pan liner. some type of rubber. i also always use a wrist strap as well.Quote from: helius on May 18, 2016, 04:37:07 amso your saying not like mike and saying that i should use metal containers?i dont mean any disrespect to anyone but as we can see there is different opinions on this matter and there has to be a way to prove one way or the other.

author: helius
author_rank: Super Contributor
timestamp: May 18, 2016, 05:21:09 am
content: Quote from: rs20 on May 18, 2016, 04:49:09 amThe OP. I'm not so sanguine about ESD safety in a hobbyist environment, though.

author: KL27x
author_rank: Super Contributor
timestamp: May 18, 2016, 06:14:43 am
content: I don't see what's so bad about metal. Unless it's shaped like a capacitor, it can't hold charge. The potential will be w/e it is touching. So as long as you store the container on a reasonably grounded bench/shelf, I don't foresee a huge concern.The only parts I take care to store in ESD safe way are FETs. I store them in brass containers. For larger through hole FETs, I have stored them wrapped in tin foil.I suppose it's possible that one pin is touching the metal and the other is floating, and when you pick up the container in your fuzzy robe and sandals, you can kill the part? I have never had that happen, storing smd fets in a brass tube.Non ESD safe plastics can build a surface charge. This can potentially cause damage to the FET. Much more of a concern, IMO, than a metal container. Bonus, a metal container is a faraday cage.IOW, I do not care about my hand damaging the part. I will touch my bench/ground/container before handling the part. The only worry that is big enough (in my mind) for me to care about is surface charge of the container. I.e. don't store fets in plastic container with a synthetic fur lining. Don't wear your fuzzy synthetic robe while handling parts. And you will usually be ok.OP, I would think cardboard is fine. Someone else will say it's a terrible idea.

author: sleemanj
author_rank: Super Contributor
timestamp: May 18, 2016, 06:33:21 am
content: ESD bags are1. Cheap2. Easily available3. Heat sealable if you need to cut them down for space or economykeep your static sensitive things in an ESD bag, and put that bag and it's contents wherever you like, if it's in the (closed, folded over top is fine) bag, you can regard it as protected from ESD.

author: KL27x
author_rank: Super Contributor
timestamp: May 18, 2016, 06:38:31 am
content: Yes, but ESD safe is a misnomer.Paper and carboard and metal and wood is ESD safe.ESD safe plastic is so labeled because some plastics/synthetics are the opposite of ESD safe."ESD safe" is therefore almost always associated with plastics/synthetics. This is like "low fat" bacon.FWIW, I have been storing microcontrollers and any other ic's but FETs in regular polyethylene bags for years without the first problem. FETs are one of the only really sensitive components. And most IC's that include FETs have clamping diodes for ESD protection. If you're going to etch dozens or thousands of components on a wafer, might as well include a few clamping diodes.Also, FWIW, whenever you buy stuff from Digi/Mouser/Newark, you can hang onto the larger ESD safe bags. For w/e reason, they always ship stuff in these bags. Even switches or header pins. I'm sure its just cheaper for them to use one standardized roll of bag for everything, but it's still curious. These are the real deal, with faraday cage built inside the plastic as well as a surface coating to prevent surface charge. AND they are super tough. Add a heat sealer, and you will have bags for days. At some point in time, I bought a huge box of the pink bags. Ended up throwing them out. I never run out of Mouser bags.

author: wraper
author_rank: Unknown
timestamp: May 18, 2016, 07:02:08 am
content: Metal is completelynot ESD safeif surroundings get charged, or something can charge it. Example from the life, where you usually get worst ESD discharges which you can feel the most: car, door knob, kitchen sink, all metal. Metal itself don't need to get charged too, you can be charged yourself (by walking on the carpet, wearing sweater) but metal will provide the capacitance needed or low resistance path, so ESD discharge becomes "successful". Don't forget, in ESD discharge, capacitance is one of the most important things, because it provides the discharge with energy. Therefore the worst ESD discharge is between 2 metal objects, capacitance is high (provides energy) but resistance is low, therefore cannot limit the discharge current. If you check datasheets, there you can find ESD ratings for Human body model and Machine model, ESD voltage for latter is order of magnitude lower. The difference between them is capacitance.Example: you are walking on the carpet and get charged. You take plastic tweezers, touch the parts on the PCB which have high enough capacitance to the earth or is connected to it in some way - nothing happens. You take metal tweezers, move it towards to the part and spark happens - part is destroyed. ESD safe tweezers are covered with dissipative material BTW, not just bare metal, so there is no low resistance path from the hand to the metal part.If you have proper ESD safe area, where things cannot get charged, metal is fine and insulators should be removed, so no charge can occur in the area. But if the area is not ESD controlled, metal can be worse than insulators.EDIT: This is not to say you cannot use metal containers at all. This is mainly addressed for those who argued with what Mike said about metal.

author: KL27x
author_rank: Super Contributor
timestamp: May 18, 2016, 07:32:10 am
content: But where/how are you normally storing and handling your metal container?Would you go out of your way to store your metal container on a shelf that is completely ungrounded and lined with fuzzy synthetic fibers? Or to set it on a BARE and freshly sanded steel shelf with a zero ohm connection to ground? (If the latter, and you touched the container to make a spark, would not the spark travel through the container like a faraday cage, and the container itself remain at ground? And contents touching the container still be at ground? In this case the metal will do you a favor of grounding you, since you forget to discharge yourself before handling your components.)Sitting on a wood shelf, it will be fine. I find it hard to imagine a scenario where it would not be fine, unless you go out of your way to create one. I'm only going to open the container and handle the contents when the box is on my bench.... ?And most common metals that one would use for a container, would be fine anyway, because they either naturally form a nonconductive oxide layer (that doesn't build surface charge), or they will be painted to prevent oxidation. The component leads themselves will form an oxide layer. A component resting on the surface will not form a good contact without a significant pressure.I store many of my components in painted steel boxes. Albeit sealed in bags, for more space/organization. Never had any issues, personally. I don't need an ESD safe label to know they're ESD safe.

author: wraper
author_rank: Unknown
timestamp: May 18, 2016, 08:19:52 am
content: Quote from: KL27x on May 18, 2016, 07:32:10 amThe problem is when you take or put he part. Spark goes through the part, not directly from you to the container. And why do you think that someone will always touch the container first? It's not rare that you open the drawer, take the parts, drawer stays open. You do the job, place remaining parts in the drawer. But you did not ground yourself to the container first. Or do youalwayskeep your parts far away from the container before touching it with a hand first?

author: VK5RC
author_rank: Unknown
timestamp: May 18, 2016, 08:24:29 am
content: +1 re mikeselectricstuff, if in production you need to be obsessive; unless the part is crazy money or buried in a complex-to-trace device AND really ESD sensitive, an ESD mat and strap covers most hobbyists.

author: Rascal
author_rank: Contributor
timestamp: May 18, 2016, 10:23:15 am
content: I think you will find 1000's of opinions on most subjects here. I guess that's the point to a certain extentMy opinion as a hobbyist - It does seem to me that many people spend so much time deliberating on various fairly petty issues, rather than 'getting on with it', and enjoying the hobby. Over the years I have stored sensitive and non sensitive components in whatever is available, plastic, cardboard, metal. Ive had very few problems.Does my hobby take place in a completely ESD safe environment? I very much doubt it.Paul

author: sync
author_rank: Frequent Contributor
timestamp: May 18, 2016, 11:56:30 am
content: I'm a hobbyist. I usually store the ESD sensitive components in the ESD safe bags in which they are delivered. I also use that black conductive foam. I not using an ESD mat (my bench is made from real wood) and I use my ESD strap only when I handling very sensitive stuff.In one case I suspect ESD damage. A bunch of TLC272 which where stored and moved for 20 years complete non ESD safe. They working fine except their input bias current is much higher than it should be.Maybe there are others small ESD damages which I didn't noticed. But I have destroyed much, much more components by mistakes which aren't related to ESD.

author: Marco
author_rank: Super Contributor
timestamp: May 18, 2016, 12:05:22 pm
content: If we just stopped using old unprotected MOSFETs we could mostly stop worrying about ESD.Almost any modern IC is harder to destroy than a 2n700x.PS. TLC272 seems to have unprotected MOSFET inputs, showing its age.

author: Jay112
author_rank: Regular Contributor
timestamp: May 18, 2016, 01:34:27 pm
content: Is there any possibility of having such a noisy ground that keeping the metal box (with the components inside) connected to ground might cause some damage?

author: CatalinaWOW
author_rank: Super Contributor
timestamp: May 18, 2016, 02:34:14 pm
content: ESD is really simple in concept, but attempts to further simplify it with rules has caused endless confusion.Statements like "can't hold a charge if not shaped like a capacitor" indicate fundamental misunderstanding of a simple concept. I am in no way shaped like a capacitor, but if I walk across a rug in winter I can easily generate a spark when touching a grounded object.The simplest way (for me) to think about ESD is to look at the data sheets. All good ones have absolute max voltage ratings. Usually some number from a few volts for most signal processing parts up to a few hundred volts for power handling parts. Varies from terminal to terminal. Any time you expose a part to higher voltages the part is at risk. It may survive if the exposure is short enough (if the energy content is low enough). Now on to how those exposures occur. Any time different materials move relative to each other there is a possibility of electron transport. Those charges remain in place until they have a way to return home. How much charge is moved depends on so many factors that mere mortals can't calculate it, but can only observe situations that tend to favor it. All of the ESD rules are attempts to either reduce those charges, or reduce the rate that they can be applied to a part.So: Conductive surfaces, ESD sprays, ionizers, heel straps, and the like reduce the charge buildup. Resistors in the esd strap and between the esd mat and ground reduce the rate of discharge. Or thought of another way, create a voltage divider that uses a large resistor and the relatively low resistance of the part to create a voltage divider that brings the voltage within the parts capability.You can use these ideas to look at your practices. Cardboard parts bins for example. Conductivity will vary with humidity. In very dry environments there could be very low conductance and therefore hold a charge for a long time. Now, if you pick up a part by one lead, and another lead touches the charged region, and if you have a charge greatly different than the charge region some charge will flow. But the high resistance of the cardboard means that only a tiny region of charge will flow easily, and thus a tiny amount of energy. Not really much chance for damage, since many different things have to go wrong in just the right way.

author: zapta
author_rank: Super Contributor
timestamp: May 18, 2016, 02:45:12 pm
content: Quote from: KL27x on May 18, 2016, 07:32:10 amI am using covered metal containers and naively assume that they block any bad influence from the outside.

author: KL27x
author_rank: Super Contributor
timestamp: May 18, 2016, 10:44:14 pm
content: QuoteBut how do you touch the part without touching the container, first? You have to open it?Let's examine this part, closer:QuoteHow is this any different than if the box where made of plastic. (Or ESD SAFE plastic). The difference is a non-ESD safe plastic that can build a surface charge might have charged the pin of a part to hundreds or thousands of volts. The metal cannot do that.And if the metal is grounded directly to ground (and why would it?) and you are charged (because you did not touch the container), and it is denuded so that it makes good contact with one of the pins... why is the spark going to travel through the part instead of sparking directly to the metal? The path of least resistance is through the metal, not the part.QuoteHow do you open the drawer without touching the drawer?QuoteYour body can hold a surface charge primarily for these basic reasons:You are wearing shoesYou are wearing clothesYou have hairThe shoes insulate you from ground. The hair and clothing increases your surface area by many fold, and the molecular structure of the surface of this hair and/or clothes is such that it can be ionized through friction against other objects. The charge isn't built/stored inside you. It's on you. This static charge is 100% due to the surface characteristics of your body and what you are wearing.A metal container does not normally have these features.The proof that metal does not hold/accept/give a charge is that to make the spark you have to touch a GROUNDED metal object.* The metal is just a conduit to ground, which is for practical purposes an infinite electron donor/acceptor.*Or a metal object in contact with something else that can act as a large enough donor/acceptor to allow ESD damage. In either case, the spark will travel through the metal, not the part.

author: Marco
author_rank: Super Contributor
timestamp: May 18, 2016, 11:15:31 pm
content: So the bastards at the last air conditioned lab I worked in had grounded doors?I flinched every time I had to touch a door handle for a while.

author: KL27x
author_rank: Super Contributor
timestamp: May 18, 2016, 11:19:23 pm
content: Hang a doorknob on a string. Rub your feet across the carpet and touch it. Let us know what happens!

author: wraper
author_rank: Unknown
timestamp: May 18, 2016, 11:21:48 pm
content: Quote from: KL27x on May 18, 2016, 10:44:14 pm2 AM here, so won't answer to all of that nonsense but will write about this particular BS. Why are you so sure? I already mentioned the car and the door knob. They both are insulated from the ground and they both get large static charge on them. How do I know? Because I felt the static discharge many times just before touching them. And no, that wasn't I who was holding the charge. Because that freaking door knob was on the door to/from ESD safe area. So when I walked out of that ESD safe area, obviously not holding the charge on myself (dissipative floor, ESD boots, yada, yada), I often got a shock from that metal door knob. Usually that happened at the Spring, because of the air humidity change during the year.

author: sync
author_rank: Frequent Contributor
timestamp: May 18, 2016, 11:25:53 pm
content: Of course a metal object can hold a charge. Electrostatics basics. In this video it is demonstrated (at 25s). The metal ball is used to transfer charge. That isn't possible when the metal ball can not hold the charge.

author: KL27x
author_rank: Super Contributor
timestamp: May 18, 2016, 11:47:23 pm
content: Notice the metal ball is attached to something else. A glass rod. A glass rod can hold a significant surface charge.Even if it was a pure metal rod, he is holding it in his hand, and we have already determined the human body can carry a significant surface charge.This is also not showing any degree of significance. We do not know how much charge there is, other than not enough to make a spark.I have just a basic bog standard education. I'm not a professional scientist. All I have is a BA. I am frequently wrong. But I store FETs in bare brass containers. I put them in bare aluminum dishes. I have not had any problems, yet? (And I do take precautions with FETs because I do know how to kill them with inappropriate measures).

author: zapta
author_rank: Super Contributor
timestamp: May 19, 2016, 02:38:26 am
content: If a metal container is a poor choice, ESD wise, this can be the subject of an interesting EEVBLOG myth busting episode.

author: KL27x
author_rank: Super Contributor
timestamp: May 19, 2016, 04:24:34 am
content: https://en.wikipedia.org/wiki/Triboelectric_effectHere's what Wikipedia says. There's a list of some common materials, showing their propensity to develop surface charge. Along the right hand side.Maybe I'm not saying or understanding that correctly, so see for yourself.Steel is at zero. Wood very close second. Aluminum around same as paper. Brass goes the other way, but several materials closer to zero than polyethylene.Polystyrene is relatively non chargeable. Surprising, but I think Styrofoam is a special case because of the increased surface area.There's no scale for reference, but it gives some idea. Near the top of the positively chargeable materials is "hair and oily skin."

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: May 19, 2016, 07:17:15 am
content: Quote from: bsahdy on May 18, 2016, 05:14:17 ampossibly not as the metal may have enough capacitance to ground to shunt the 1M to a muck lower impedance for fast discharges

author: KL27x
author_rank: Super Contributor
timestamp: May 19, 2016, 07:43:19 am
content: Totally off base, I'm sure. But it seems to me that the surface of some metals can hold some amount of surface charge. Not quite sure how much, but not as much as a human being's skin, according to Wikipedia. Again, I'm totally wrong, I'm sure, but I was under the impression that it's not the interior of the metal that acts as a donor/acceptor, just the surface.I'm curious, how big is the surface area of the metal before this becomes a problem?If you took some copper clad and made a box out of it, you can no longer safely put a FET on it?Does a ground plane for a 12" x 9" pcb create a significant ESD hazard? Your PCB itself is a significant ESD hazard? And even if you ground it with a 1Mohm resistor, you can not assume to safely solder a FET to it?Does thick copper wire act as a capacitor? Say 20 feet of 6 AWG wire? Enough to create an ESD hazard?I would presume litz wire would have a lot more capacitance? How much litz wire of the same gauge before it can store a dangerous amount of charge (to a FET)?I must be totally off base. I can't figure out why this metal box is an ESD hazard.Thin metal foil can be made into a capacitor. Take two pieces of metal foil with a thin dielectric separating them. Roll them up tight. The close proximity of the metal plates is what allows one to store charge. If the plates were far apart, it would not work. The electrons would not want to be removed from their spot. The capacitance would be close to zero. It's only when you put them very close together that the one plate "allows" the other to borrow these surface electrons... as long as they are still within "arm's reach." Try to charge it too high, like the 1KV of ESD range sparkies, and the electrons will want to return home so bad they will fry the dielectric.The metal box is not very much like a capacitor. A piece of copper clad is a lot more like a capacitor. A PCB with a top power and bottom ground plane is a lot more like a capacitor.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: May 19, 2016, 02:28:18 pm
content: The problem with metal boxes is that they are good conductors. They can provide a path for charge to go through a sensitive device. As you have pointed out, and observed in your experience, good practices make this a non-issue.It is kind of like belts and suspenders (or braces or galluses or whatever you want to call them). Either can keep pants up. And pants often stay up without either. But if you wear both belts and suspenders, pants are even more unlikely to fall. Some people will swear you need neither, and testify that their pants have never fallen. And if they have a large waistline and small pants they will be absolutely right. Others may have different experiences.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: May 19, 2016, 04:54:30 pm
content: QuoteIt's not the box that's the hazard per se,it's the fact that it provides a low impedance discharge pathAgain, it's all about discharge impedance.Assuming you are not grounded and your body has a charge on it :You pick a part up off an insulated surface. The part now has the same charge as you do, and the part's capacitance to ground is low enough that the current flow transferring some of your charge to it to doesn't harm it.If you then bring the part near a grounded metal surface, the charge can discharge at a high current due to the low impedance of the discharge path. Even if the metal is not grounded, or grounded via 1M, if the metal is big enough, its capacitance to ground will provide a low impedance ground path.if you are wearing a ground strap it's not an issue, but who wants to dick about with those.Although using a raw plastic container has potential to produce some charge in the first place, and allow a board to sit there holding charge that can discharge when someone touches it, that risk is fairly minimal compared to the charge that a person can develop and hold due to size and the charging mechanisms available.

author: Raj
author_rank: Frequent Contributor
timestamp: May 19, 2016, 04:59:06 pm
content: My dad collected lots of iron munition boxes while he was in the army, I use those to store components.while keeping them on a grounded aluminium plate.funny how the contents of those boxed, when burnt causes only red smoke to emerge while they are painted red and have "danger, explosives" written all over them

author: Marco
author_rank: Super Contributor
timestamp: May 19, 2016, 05:28:25 pm
content: The capacitance of a 100 mm sphere to ground at infinity is around 10 pF ... a 2n7002 has 30 pF gate-source capacitance.Do the math of what an ESD pulse will do across a capacitive divider with those two values.

author: KL27x
author_rank: Super Contributor
timestamp: May 19, 2016, 05:36:11 pm
content: CatalinaWOW, it sounds like you are agreeing with me. Maybe I'm not a complete idiot.But as for the danger thru being conductive thing, I may be stupid. I will wear just the belt until my pants fall down. I see not too many men wearing suspenders, and yet I have to go to Youtube too see someone's pants spontaneously falling down.Also, I disagree with you.QuoteYou need suspenders when your waist is large. When larger than your hips, the belt don't work, anymore.

author: KL27x
author_rank: Super Contributor
timestamp: May 19, 2016, 05:42:00 pm
content: QuoteWhat does infinity mean?

author: Marco
author_rank: Super Contributor
timestamp: May 19, 2016, 05:51:40 pm
content: Quote from: KL27x on May 19, 2016, 05:42:00 pmTo infinity and beyond ... as far away as possible and then some. Using infinity as the distance allows you to determine the minimum capacitance a sphere will have to ground, in practice it will always be higher.This free space capacitance of objects is part of why you spark to isolated metal objects when you are charged. The other part being the fact that both you and the metal object are relatively highly conductive, allowing the charge to distribute between you in a short time frame. Sometimes through the gate isolation of an unprotected MOSFET.

author: KL27x
author_rank: Super Contributor
timestamp: May 19, 2016, 06:23:54 pm
content: Ahh, interesting. Yeah, it doesn't take much capacitance. I see.So let's see if I can piece this all together.A large enough piece of metal can be a donor/acceptor for an ESD. Because of it's surface area and its high conductivity.Let's say I'm positively charged. Because if you believe Wikipedia, I have positive triboelectric property.So now as long as I do not ground myself, by touching anything of significant size which has path to ground. And as long as I don't touch the container while picking up the part. And as long as I am picking the part directly out of the container with tweezers and I don't accidentally touch the tweezers to the container before touching the part. I can kill the FET? Is this correct? Is there some other way the metal container can aid in killing the FET?When I then take the FET to the PCB, same thing applies? This piece of metal in the PCB with enough surface area and conductivity is possibly large enough electron donor to zap the FET?So when handling FET, if I use an ESD safe (plastic) box. I will not have to take any precautions while handling the FET until I get to my bench? Or did I get it wrong? I will walk across the rug and pick up the part, and then ground myself when I get to the bench? (And why do I not take the whole box to my bench, I do not know...Instead, I must retain the capability of walking to another room in my bathrobe and slippers and pick up a single FET with tweezers in a fashion of playing a game of Operation, and walk back to my bench with it, and THEN take ESD precautions.)Or can I kill a FET by doing this even despite the fact it is labeled "ESD safe?" In which case the practical difference between the ESD safe box and the metal box is even less significant? What IS the remaining significance, in practical terms? What can I do with the ESD safe box that is going to affect the way I can work?What about non ESD safe plastics (nonconductive). In my experience FETs can be killed without even sparks occurring. Perhaps with small enough gate capacitance of tiny signal FET, they can die without a spark, due to triboelectric effect. Simply putting them in the box and shaking them around, generating surface charge between itself and the surface of a pin? Simply the triboelectric effect pushing gate beyond +-8V voltage limit? It is for this thing I am more concerned. I have only ever had FETs dead. And without spark. I suspect sparks are not needed to kill them. I am more concerned with non-conductor surface charge generator than high conductor tiny capacitance donor.

author: Gyro
author_rank: Super Contributor
timestamp: May 19, 2016, 06:26:46 pm
content: I don't understand why there should be 1000, or even 10 opinions on ESD, it's really not a complicated enough subject to justify them!I'm not sure why there are so many spurious diversions of knobs, metal or otherwise.The fundamental requirements:1.You need to transfer the part from storage to the operator/workstation under equipotential conditions.2.You need to avoid damaging current discharges through the device terminals resulting from any remaining or accidental relative potentials.Meeting these requires:1.The operator needs to be grounded to (Edit: at) the same potential as the workstation, the most common solution would be antistatic mat and wrist strap.2.The antistatic mat should have a static dissipative surface to avoid any possibility of current spikes due to any accidental temporary potential differences between the operator and the workstation mat.3.A conductive storage container for the parts, could be metal, it could be something like a conductive plastic storage box, or it could be its original antistatic packaging / bag.4.This container needs to be either held at the same potential as the workstation or brought to the same potential while transferring the parts (this could be achieved by the operator holding it).5.The container should be lined with a static dissipative material to prevent any possibility of current spike due to temporary or accidental remaining potential differences (not bare metal!). This lining could be antistatic foam or even cardboard at a push (no one ever managed to significantly charge up a piece of cardboard by rubbing it with a cat!). You need something in the container anyway to prevent physical damage, bent pins etc.I realize that it's not as much fun, but that's all there is to it. You just need to ensure that your setup meets these requirements.

author: Marco
author_rank: Super Contributor
timestamp: May 19, 2016, 06:45:30 pm
content: Procedures aren't always followed ... you can still reduce failures by reducing the impact of that.So semi-conductive materials instead of conductive materials, air ionizers etc.

author: KL27x
author_rank: Super Contributor
timestamp: May 19, 2016, 07:05:35 pm
content: Human skin is a high impedance conductor, too.This why you can touch ground and discharge yourself. Or wear a doofy wrist strap if you somehow manage to work without touching your bench.

author: KL27x
author_rank: Super Contributor
timestamp: May 19, 2016, 07:08:57 pm
content: If "ESD safe" is so simple and straightforward and well understood and I should always look for "ESD safe" label, and "semi-conductor" (by which I assume you mean high impedance conductor, not doped silicon, and with which I generally agree) is the best ESD safe material, maybe someone can explain why when I buy an "ESD safe" soldering iron and it has a 0.0R connection to earth?

author: Gyro
author_rank: Super Contributor
timestamp: May 19, 2016, 07:25:12 pm
content: I've wondered about that one, I'd prefer a resistively connected iron tip. I suspect the reasoning is that the danger of capacitively coupled spikes from the element supply switching etc. is higher than that of it being directly grounded. If everything else is resistively coupled then the risk is minimised as much as possible.QuoteThat's until you shuffle your feet or your a**! Stick with the doofy wrist strap. It's the temporary potential disturbances caused by these actions that are the main need for static dissipative (high resistance) linings / mats. A 1M resistor can't equalize your potential instantly when you shuffle about.P.S. Human skin isn't really a high impedance in ESD terms, hence the Human body model - 50pF1k5R(not significant at 2-8kV)

author: CatalinaWOW
author_rank: Super Contributor
timestamp: May 19, 2016, 08:03:05 pm
content: It really is fundamentally simple. You can go down many rat holes chasing details or formalizing a methodology that works for people with a wide variation in training, background and resources. The link at the bottom of this post from Maxim is a (to me) a clear, concise description of the problem, the impacts, and some strategies for resolution. There is no fixed answer on how to control ESD, just lots of things that help (or hurt). Doing a science based strategy for ESD control requires knowing things like acceptable failure rates, minimum life requirements, failure rates on ESD control devices, and things which are typically hand waved like degree of compliance with the ESD procedures at a given worksite.Keep in mind that the active pieces of our electronics goodies are really, really small so it doesn't take much energy to disrupt them. Also, when you are saying that you have never had ESD damage remember that many parts operate after ESD damage. They may meet all performance specs, as occurs when the first ESD contact vaporizes the ESD protection diodes which many ICs now incorporate. Of course the second ESD contact is likely to hurt something more important. The part may merely be degraded in some way, such as worse offsets, worse supply isolation or some other parameter which may not matter in the specific application. Or maybe just lost the top oxide layer so the chip is more susceptible to the environment.https://www.maximintegrated.com/en/app-notes/index.mvp/id/639

author: Gyro
author_rank: Super Contributor
timestamp: May 19, 2016, 08:10:53 pm
content: ... and tracking down problems due to degraded parts is a hell of a lot more difficult that outright failed parts!

author: tautech
author_rank: Super Contributor
timestamp: May 19, 2016, 10:58:47 pm
content: Quote from: bsahdy on May 18, 2016, 04:19:52 amMaybe but this is better and CHEAP:http://www.newark.com/multicomp/039-0050/low-density-conductive-foam-305x305x6mm/dp/87P0222Lines all my ESD sensitive parts boxes and drawers. ^^^

author: KL27x
author_rank: Super Contributor
timestamp: May 20, 2016, 08:42:21 am
content: You really can't be too safe.http://www.newark.com/ck-tools/z1123/esd-ball-pen/dp/64T4680

author: CatalinaWOW
author_rank: Super Contributor
timestamp: May 20, 2016, 01:42:25 pm
content: When you are taking notes on assembly of a Jupiter orbiter that pen doesn't seem silly at all.When you are making something to make a toys eyes blink back and forth, meh!Before I retired, I worked with high value product where the consequence of failures was enormous. Just about every ESD precaution you can think of was employed. Because the product was high value and the consequence of failure was enormous full root cause diagnosis was done on failures and occasionally on random samples. And in spite of the precautions ESD damage was found in photomicrographs of the silicon die from time to time.But at home, working on my hobby projects I don't even bother with an ESD mat. I do the things I find appropriate to avoid pulsing a device with a static charge. I don't remember having a failure.Why the "differences" in results? At home I am doing far less volume of work than the team involved when I was working. That work is more varied and so I am more thoughtful and intentional than a person can usually be when working a more standardized job. I am in total control of everything that happens to everything from the time it is unpacked from the supplier until it is put into service. I am seldom under time pressure. And at home much of what I do is insensitive to minor ESD damage. So while damage may have occurred I am blissfully unaware.I am quite comfortable with the choices in both circumstances. These differences in circumstances and widely varying understanding of the mechanisms of ESD and the susceptibility of various devices to ESD are the reasons you find 1000s of opinions on ESD. Many of them are not wrong given their circumstances.

author: Ian.M
author_rank: Super Contributor
timestamp: May 20, 2016, 02:12:36 pm
content: Any all-metal body, all-metal refill ballpoint will be ESD safe, if the user is properly grounded in an ESD safe environment, but is likely to be pricier than the CK tools ESD safe pen KL27x linked to. An all metal pen is riskier if the user is NOT properly grounded as if the object being labelled is a thin dissipative bag on a low impedance grounded surface, the pen could concentrate the discharge resulting in punchthrough and possible ESD damage to the bag contents.Me? well I wouldn't worry too much. I'm not building avionics or medical devices, and its ****ing awkward to write on a bag with parts in it under the label anyway so I tend to avoid that, either with a sticky label or simply shaking the parts to the end of the bag, + my preferred types of pen, (an ordinary 0.5mm fine line marker for paper labels or a Sharpie for direct writing on plastic bags), have insulating bodies so wont concentrate a discharge, and cant hold a lot of charge even if the workshop cat has been rolling on them!

author: Gyro
author_rank: Super Contributor
timestamp: May 20, 2016, 03:15:08 pm
content: Of course the traditional wooden pencil could have beendesignedfor ESD safe environments - a resistive core and static dissipative outer.Just don't break the lead.

author: Ian.M
author_rank: Super Contributor
timestamp: May 20, 2016, 03:34:10 pm
content: I fixed that for you:Quote from: Gyro on May 20, 2016, 03:15:08 pmOnce its coated with a manufacturer's lacquer or varnish finish you risk undesirable triboelectric effects.

author: KL27x
author_rank: Super Contributor
timestamp: May 20, 2016, 07:18:06 pm
content: Correction. After you paint it with the most tribolectric material possible, you spray it with conductive ESD-spray and sell it as ESD-pencil. Bare wood is natural, which you cannot call ESD-safe; that would just be a marketing ploy.QuoteYes, there is a time and place. I do not question all ESD safety practices. But I suspect some [products/practices/wisdom] are borderline questionable benefit, even where it does matter. General understanding maybe not 100% as straightforward to the general population or even to me. I just see some ideas out there and my own puny brain does not connect all the dots to know what the hell is the purpose. I suspect some of the generally accepted knowledge just might be misapplied or taken too far and/or used out of context. Since I don't have the tools to investigate, directly, I just speculate. When I find a dead FET taken from a metal container, I will be sure to make a post on this awesome forum.ESD mat to protect from a wood bench and metal containers are two of the things I am not particularly impressed about. Maybe I'm dumb and won't know the sky is falling until I can either understand why it is falling or when it hits me on the head.

author: Ian.M
author_rank: Super Contributor
timestamp: May 20, 2016, 08:07:13 pm
content: Freshly oven dried wood is an insulator. Wood at a typical equilibrium moisture content to the air of 10% - 12% typically has a bulk resistivity of 10^10 Ohms/cm or less, which would put it at the upper end of the dissipative materials range. If your building is air conditioned or you are in a desert climate, you'd better soak your pencils in calcium chloride solution for a week then rinse and air dry to decrease their bulk resistivity.

author: KL27x
author_rank: Super Contributor
timestamp: May 20, 2016, 08:17:19 pm
content: Hehe.I just had a thought. Yeah, that is rare for me.Metal box has capacitance, and that is bad, right? If I solder a small value (smaller than gate capacitance) capacitor to one or other leg of a FET, is it more prone to ESD damage, now? The capacitance is in series with the gate. So the capacitance goes down, not up. And the voltage goes up? I mean, treating the FET gate as a capacitor.Now I'm just confusing myself more, lol. And now I wonder if I can increase the max voltage and/or reduce the total capacitance of a FET gate by adding a series capacitor.*Now I'm also wondering about what mike said. Grounded through 1megaohm resistor, the box can be dangerous through capacitance. The significant aside, I am now wondering if it deosn't makes a difference what metal. For instance, if human body has positive triboelectric effect, and aluminum has positive triboelectric effect, than aluminum cannot cause damage when it is so grounded. Or steel, which is close to zero. But maybe brass, going the other way (copper? who knows... it's a main alloying element in brass) can have some possible effect? Does any of this bare metal problem start sounding sorta trivial, to anyone else but me? (Of course when I saw trivial, this is assuming your bench is not made of bare metal, itself).

author: Ian.M
author_rank: Super Contributor
timestamp: May 20, 2016, 08:41:44 pm
content: Sounds like a good way of FUBARing it. Without a DC leakage path to the drain, any stray charge (e.g. from moving air) on the gate and your added cap will build up and shift the bias point. Whichever way it shifts, the result is likely to be silicon shrapnel as not turning fully on is just as bad as not turning fully off.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: May 20, 2016, 08:46:07 pm
content: Quote from: KL27x on May 20, 2016, 07:18:06 pmI agree. The various practices don't all have equal value. And often the value lies more in the area of psychology than in physics. The ritual of daily checking continuity of wrist-straps (or checking the continuity indicator on a continuous monitoring wrist strap each time you touch hardware) is a continual reminder of what can go wrong. Even though in many cases years passed between an observed failure other than forgetting to put the wrist strap on. Same applies to other things like the anti-static ball point pen.The problems are real though. I used to plot product yield vs outdoor absolute humidity and see substantial correlation before appropriate indoor humidity control was installed. There are many other examples that I and others here could provide.

author: KL27x
author_rank: Super Contributor
timestamp: May 21, 2016, 04:13:29 am
content: ^ no doubt, they are real. When you consider the number of active semiconductors in a modern computer, it makes me wonder how many failed boards go in the trash heap to produce 100 working units.QuoteThis reminds me of something I read about eastern pottery. Korean potters were at one time reknowned for a form of pottery that had a distinct greenish color. To produce this, the pottery had to be held to +- something like 15 degrees Celcius for a period of over 20 hours. Mind you this is somewhere in the 12th century AD, so this was something of a difficult feat. It was believed that this pottery could only be produced in times of peace and economic stability and spiritual harmony of the workers.The culture of ESD is undoubtedly important to manufacturers of complex devices. W/e it takes to improve the yield and bottom line. I think some hobbyists cross that bridge just for the sake of crossing it, without having a destination on the other side.