ESD Sensitivity of Diodes and BJTs - Page 1
Forum section: electronics / beginners

author: rstor22
author_rank: Regular Contributor
timestamp: September 07, 2016, 07:10:59 pm
content: Regarding the following components:- Diodes (1N400x, 1N540x, 1N58xx, and various signal diodes such as 1N4148, BAT46/41 etc)- BJTs (Signal and Power)- Voltage RegulatorsIs it ok for the hobbyist to store the above components in small zip lock (resealable) plastic bags (placed within older acrylic drawers)?Or would something such as pink anti static bags be recommended? I would think that shielded bags for the general hobbyist may not be warranted for such components (please correct me if I am wrong)(I understand for FETs/ICs you would want to keep them in shielded bags or at least in conductive foam)In one of Dave's video (#247) @ 8:25 he shows how a plastic drawer of resistors in plastic bags generates about a couple hundred volts. Is this enough to cause serious damage to the above components?

author: tatus1969
author_rank: Super Contributor
timestamp: September 07, 2016, 07:18:10 pm
content: diodes / BJTs are less sensitive to ESD because of their avalanche behavior at overvoltage, which will just dump the energy into the die and heat it up. The only problem with MOSFETs is the isolated gate, and ESD pulse will permanently damage the isolation barrier. The source-drain path is robust again (avalanche).

author: helius
author_rank: Super Contributor
timestamp: September 07, 2016, 07:25:04 pm
content: Using pink antistatic bags is always a good idea around an electronics workbench, not to protect the components but simply to avoid static buildup while working.ESD damage is possible on any component (say hello to my little Van de Graaff generator...), but FETs, IGBTs, and tunnel diodes are the parts that are really vulnerable to accidental events, because of their thin gate structures.

author: Tandy
author_rank: Frequent Contributor
timestamp: September 07, 2016, 07:27:41 pm
content: The reason MOS type semiconductors are susceptible to damage by static it that the gate is made from a very fine oxide layer that can literally have holes blown in it by the charge. It may not completely destroy the device but would cause damage changing the characteristics of the device.Silicon diodes and BJTs are fine in ordinary plastic bags. The anti-static coating on the pink bags evaporates over a few months and becomes ineffective anyway. It is always advisable to use conductive (silver or black carbon) bags for MOS components.

author: jitter
author_rank: Frequent Contributor
timestamp: September 07, 2016, 07:31:37 pm
content: And for voltage regulators... TI specify an ESD rating for (e.g.) anLM317a max of 2500 V for the human body model. That's not a lot, ESD kan run far into the kV range.

author: rstor22
author_rank: Regular Contributor
timestamp: September 07, 2016, 07:49:38 pm
content: Reading the responses it looks like it'll be okay storing diodes/BJTs in regular plastic zip lock bags...Quote from: jitter on September 07, 2016, 07:31:37 pmIf one is grounded, then the ESD concern would be from the charge of the plastic bags themselves, correct? In the aforementioned video the plastic bags in Dave's test was a couple hundred volts. Do you think this charge would be a concern to voltage regulators if we assume the individual is grounded?(I ordered a bunch of components from Tayda which included voltage regulators, everything was shipped in what appears to be regular mini resealable plastic bags)

author: Tandy
author_rank: Frequent Contributor
timestamp: September 07, 2016, 08:06:51 pm
content: There is a huge amount of misunderstanding about static precautions, and grounding yourself  is not necessarily the answer.Every object has a charge potential and when one object comes into contact with another the charge will equalise by the object with the higher potential for want of a better word dumping its excess charge on the object that has the lower potential. If you have the regulator pushed into some conductive foam than all 3 pins will be at the same potential minimising the risk of damage.

author: setq
author_rank: Frequent Contributor
timestamp: September 07, 2016, 08:10:55 pm
content: I've manhandled lots of static sensitive components I.e. dropped them on synthetic clothes, pinged them across the carpet, never used a wrist strap, store them in normal bags, whack them in polystyrene. I have to this day killed only a single 4011 through static and I'm not sure it wasn't done by the monkey at maplin who packed it.I have killed many through human error though. Just 5 minutes ago I smoked two nice TO18 Motorola 2n2907a transistors by blindly shorting their cases together with a heatsink when experimenting with thermal coupling in current mirrors. I'd worry more about this.I think even Bob Pease didn't bother much about this from his writings.I only really store CMOS ICs and MOSFETs in anti static storage. Everything else, not so much of a problem.

author: tatus1969
author_rank: Super Contributor
timestamp: September 07, 2016, 08:12:28 pm
content: what you should keep in mind, and what I also only recently stumbled on is, that one does only recognize/feel esd above ~2kV, which is already more than enough for many electronic components to die. This has put the importance of esd protection into a different light for me.

author: JS
author_rank: Frequent Contributor
timestamp: September 07, 2016, 09:23:42 pm
content: As mentioned PN junctions is what we use to protect the MiS/MOS sensitive devices, so BJT and normal silicon diodes are find by themselves. Some small LEDs are sensitive to reverse bias, usually in the order of the polarization voltage, so something to be careful when designing but rarely a worry for ESD burning them.CMOS are delicate pieces, handle your i7 with care, really tiny gates with almost no capacitance to dampen the spike and no losses to dump them in, the only way is the parasitic diode with the surrounding Si, which could handle a small charge, fail to short which sometimes only ruins the pin, sometimes with enough energy blows you entire device.Now, on human ESD interfaces... We do dump few tens of kV when you shout to the car and hear a loud cracking. A long strip of scotch tape strips a lot of tiny electrons from the roll, building maybe 10kV which you can fill if you get your hand close and if you take 2 long strips they will repel each other as crazy, and try to get close to the roll.JS

author: Zero999
author_rank: Super Contributor
timestamp: September 07, 2016, 10:18:28 pm
content: It's only MOSFETs and IGBTs which are really sensitive to ESD. Most CMOS ICs have some level of ESD protection, which makes them as robust as BJTs and diodes. ICs with very small features may be more sensitive though because it doesn't take so much current to damage the tiny connections.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: September 08, 2016, 01:44:54 am
content: "Antistatic" bags aredissipative, notconductive.This suggests the very reason for the materials, and why some components are used with them.Diodes, BJTs, SCRs and so on, have relatively high leakage currents. Thus, they dissipate any static charge by themselves.A very small diode might not need static-dissipative packaging, but might still be susceptible to quite low ESD (under 1kV).ESD is an extremely destructive event. An 8kV (IEC 61000-4-2) discharge releases a peak of almost 30A, ramping up in under five nanoseconds! The discharge lingers on for over 50ns, delivering 5 millijoules of energy. That's a peak power of ~100kW!A very small semiconductor junction requires very little energy to completely vaporize. Even a (1um)^2 diode is unimaginably small. (Go on, try imagining it. Hair? Nope, human hairs are like gain silos! Pollen grains? Closer, but those are still like basketballs, compared to an about softball sized diode junction.)So why static-dissipative materials? Some semiconductors are such good insulators, that they can accumulate static charge just from ambient fields. It doesn't leak away. MOS gates are this way. (But hey, small PN diodes are nearly as good!)As for conductive materials (like antistatic foam, from the days of DIP ICs), it is conductive enough to short out any accumulated charge, plus short out ambient electric fields (thus avoiding electric induction as well). But it's not so conductive that the surge current would be destructively high: if the foam is exposed to a spark, the relatively high resistance limits current flow (effectively exposing any components, plugged in nearby, to a greatly attenuated ESD pulse, though still with a high voltage capability behind it), and the planar or voluminous nature of the foam causes the voltage to spread out and dissipate quickly with distance (as 1/r to 1/r^2).You could use something like metal foil, to short out ICs and whatnot -- but the peak voltage isn't eliminated (the foil has equivalent inductance!), and the available current is still huge.What about components that are *really* sensitive? Foam isn't good enough; they're stored with a metal spring wrapped around the leads (e.g., the classic 3N106 or whatever it was), or inside a cocoon of heavy foam.The vast majority of components sold today are rated for 2kV or more, which is enough to cover most nuisance cases while handling, and suffices to protect against the spike that's leftover (usually 10s of V) from using external ESD protection on the outside connections where it's necessary.Tim

author: rstor22
author_rank: Regular Contributor
timestamp: September 08, 2016, 02:57:32 am
content: Quote from: T3sl4co1l on September 08, 2016, 01:44:54 amThank you Tim for putting things into perspective. From this I would understand that it would be safe to store diodes and BJTs in regular ziplock plastic bags, ICs (e.g. 4000 series) in conductive foam, and MOSFETs in shielded bags, correct?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: September 08, 2016, 03:09:43 am
content: Right!RF MOSFETs (or really, most RF stuff, bipolar or otherwise) should be in shielded bags; your average power MOSFETs/IGBTs are big enough that they're less of a danger to themselves, and are fine in antistatic foam or bags, along with the ICs.Tim

author: jitter
author_rank: Frequent Contributor
timestamp: September 08, 2016, 04:36:41 am
content: Quote from: setq on September 07, 2016, 08:10:55 pmThe problem with this approach is that a lot of ESD damage may not have completely killed a component, but left it weak and susceptible to early failure, somewhere out in the field.The company I work for actually won an order from a new customer, not on price but because we take ESD precautions seriously.My advice: treat all semiconductors like they're ESD sensitive. You will see that component suppliers that take ESD seriously do the same.

author: dmills
author_rank: Super Contributor
timestamp: September 08, 2016, 09:42:24 am
content: Oh GaN, gates that blow out at 10V..... Such wonderful properties in some ways, such a pain others.Laser diodes are another good one, even a discharge that forward biases the diode can deliver enough of an over current that the resulting laser pulse can cause optical damage to the reflective crystal faces, and they really do not cope well with reverse bias.Small geometry RF components are fun here as well.I would second the comments about latent failures, there is a reason the production guys care about this stuff more then the prototype lab does.Regards, Dan.

author: tggzzz
author_rank: Super Contributor
timestamp: September 08, 2016, 11:24:23 am
content: Quote from: dmills on September 08, 2016, 09:42:24 amVery true.I'll also add tunnel diodes that are sufficiently beefy put 400mV into a 100ohm load. They are sufficiently susceptible to static in cables that Tektronix (invented and?) supplied some TDRs with averyunusual BNC connector. The connector has an internal short-circuit that, as a cable is being attached, shorts the core to the shield thereby discharging static. When the cable is fully attached, the short circuit is automatically disconnected.

author: dmills
author_rank: Super Contributor
timestamp: September 08, 2016, 12:24:50 pm
content: Thats fun, but for unfortunate damage due to stored charge I will see TDR and raise you the sonar industry.The big piezo composite transducers can have whole tens of nanofarads of effective capacitance and taking them from a heated lab and chucking them into water at a few degrees can produce sufficient stress change to produce several thousand volts, you learn this the hard way on your first day in the office (It don't half sting).What happens when you get a connectorised one and plug it into the VNA without thinking is **Expensive**.We always kept the cables shorted just to reduce the surprises, and we still sometimes got caught.Regards, Dan.

author: tggzzz
author_rank: Super Contributor
timestamp: September 08, 2016, 12:38:06 pm
content: Quote from: dmills on September 08, 2016, 12:24:50 pmAnd you haven't even mentioned any "soakage" or "dielectric storage" effects!QuoteOuch. permanently attached 3dB (or even 1dB) attenuators have a certain attraction, pun not intended.

author: dmills
author_rank: Super Contributor
timestamp: September 08, 2016, 12:51:44 pm
content: You would think that potting a megaohm or so resistor chain in with the thing would be a no brainer, but then customers complain because there is leakage so there must be a fault....Difficult to do a G/B plot thru an attenuator.Agilent service used to love us, and I am pretty sure they just replaced the first mixer on anything we sent them without even testing it.Regards, Dan.

author: rstor22
author_rank: Regular Contributor
timestamp: September 08, 2016, 08:07:47 pm
content: Quote from: T3sl4co1l on September 08, 2016, 03:09:43 amI was reading a bit more into this and it appears there are anti-static bags and static-dissipative bags:http://uppi.com/faq/what-is-the-difference-between-static-dissipative-and-anti-static-materials/Based on reading the explination at the above link and what you have mentioned about MOS gates being good insulators and accumulating static charge from ambient fields I would conclude that:1. If a MOSFET is placed in a shielded bag, it would not be able to accumulate any static charge while inside the shielded bag (regardless of where the shielded bag is)2. If a MOSFET is placed in a static dissipative bag (which is on a grounded surface), any static charge accumulated by the MOSFET from ambient fields would be dissipated to ground3. If the MOSFET was placed in an anti-static (non dissipative bag) it would accumulate (an undesired) static charge from ambient fields (even if the bag is on a grounded surface).Is my understanding correct?

author: helius
author_rank: Super Contributor
timestamp: September 08, 2016, 08:53:17 pm
content: All anti-static bags do is prevent triboelectric charging during handling. Ideally, all plastic bags used for any purpose within the ESD area should be anti-static to eliminate triboelectricity. This still doesn'tprotectanything.When sensitive parts are transported away from the ESD area, they need to be in ESD shielded containers or bags. Within the ESD area (or workstation with a grounded mat, grounded operator, and other safeguards), the parts can be removed from the shielded container.The reason for static-dissipating materials is to reduce the dV/dt spike from contact between different potential surfaces. If you put your chip in a static-dissipating bag, and then inside an ESD shielded bag, then it would be properly protected for the following scenario:You receive the package containing ESD shielded bags. These bags are then sent to the ESD workstation area for use.The operator in the ESD area is grounded, with a grounded mat, etc. She can then open the ESD shielded bag.Inside is a static-dissipative bag containing the part. If there is a static charge on the part, it is slowly dissipated through the bag to the operator when she touches the bag. On the other hand, if the operator is wearing nitrile gloves, they act as static-dissipative when she touches the part. The key is that the parts may still be charged at the time they are removed from ESD shielding: even though there is no electric field within the ESD shield, it is not guaranteed that devices will have zero charge.

author: rstor22
author_rank: Regular Contributor
timestamp: September 08, 2016, 10:02:04 pm
content: Quote from: helius on September 08, 2016, 08:53:17 pmIn the example you provided, since the operator is grounded, wouldn't the dV/dt spike already be reduced via the 1 Meg ohm resistor in the wrist strap? Or is the static dissipative bag yet another level of protection for further reduction?Quote from: helius on September 08, 2016, 08:53:17 pmWhat about the following situation:A component is already sitting on a grounded mat and is placed directly into a shielded bag. It is then transported to another location which is at exactly the same ground potential. Can it be said that in this specific example the component inside the shielded bag will have zero charge relative to the original packing and unpacking locations?

author: helius
author_rank: Super Contributor
timestamp: September 09, 2016, 01:34:53 am
content: Quote from: rstor22 on September 08, 2016, 10:02:04 pmNot necessarily. The human body has a capacitance that can supply a high current for a short period of time, even if the body is grounded through a resistor.QuoteNot necessarily as the ground may be charged differently in different places, by storm activity for example.

author: jitter
author_rank: Frequent Contributor
timestamp: September 09, 2016, 04:13:22 am
content: In a practical ESD protected area (EPA), everything is grounded. We're not just talking about operators and work surfaces, but also floors, chairs, operator's clothing and shoes, transport and storage crates, etc. etc.Chances are that even before unpacking, charge has been equilibrated. If not, opening a shielded bag and reaching for the stick or black foam the ICs have been pushed into will do that.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: September 09, 2016, 06:22:23 am
content: Note that there's no such thing as ground, and ground doesn't matter.Ground is only used as a simplifying convenience.A sufficiently conductive bag shorts out ambient E fields, shielding the contents (i.e., as a Faraday cage) and allowing the bag to be passed between any potential environment.But what about sparks?Induction. If the bag is fully enclosed by the local potential, at each end point, then it has the same charge it always did: zero relative to those surroundings.In practice, handling isn't going to deliver all the charge from induction, and sparks will happen. Which is why extra layers, and extra conductivity, and grounding precautions, are helpful.Tim