ElectroStatic Damage

[Be-Kind-Rewind]

I ordered some diodes from Mouser Electronics and apparently they are electrostatic sensitive devices. I got an antistatic wriststrap but not so sure how I'm supposed to use it.
Should I worry about damaging my components with electrostatic charge if electricity has never ran through the circuit? How am I supposed to handle ESD sensitive devices while populating a board, cutting leads, and soldering?

Thanks for your time

[PRR]

What part-number diode?

I can't think of any diode you are likely to use in audio which is really static sensitive.

Some vendors throw everything in anti-staic bags just because it is simpler.

[Taylor]

Yeah, I don't think it's something you need to worry about. I have only ever maybe killed CMOS chips by recklessly handling them, never a diode or transistor, even though Mouser ships them all in ESD bags.

I say maybe because I'm not even sure I've ever killed a CMOS chip with reckless handling - I seem to remember a 4066 not working until I replaced it, but I might have had it in backwards or something else dumb in my complete noob days. I sometimes even pick up my EEPROMS with my fingers and have never killed one - though I wouldn't recommend that and try not to do it.

[R.G.]

Yes, again for what Paul and Taylor said.

All semiconductor devices are eletrostatically sensitive to some varying degree. This was ignored until MOS transistors in the 1960s were found to be permanently damaged by the amount of static caused by your clothes and walking around in dry rooms. These were expensive curiosities for the most part, until N-MMOS and PMOS, then CMOS logic was developed. These were widely used, and also expensive, so methods were developed to use them without killing them by touching them. It was only later, in the mid-70s, when it began to be realized that the ever-smaller, ever-tinier bipolar transistors could be damaged, albeit in less obvious ways than MOS devices. The gain and noise characteristics of a really, really good NPN, like maybe a 2N5088  could be permanently degraded by being reverse broken even once, although the amount of damage was more proportional to the applied energy than the sudden death of a MOS device. So gradually, device manufacturers and part buyers started doing "electrostatic sensitive" for everything that semiconducts.

Tubes are actually static sensitive and can be permanently damaged by electrostatic discharge if it's intense enough. So are houses and stone chimneys. Think lightning here. 

I ordered some diodes from Mouser Electronics and apparently they are electrostatic sensitive devices.

Mouser sends every semiconductor in an antistatic bag, marked with a "static sensitive" sticker.

I got an antistatic wriststrap but not so sure how I'm supposed to use it.

You put it on your wrist, and connect the free end to a place that's grounded, really grounded. Like the safety ground of your AC lines, or - since you very seldom test your AC safety ground and didn't usually know the electrician who did the work - better yet, a cold water pipe - if they're copper, which many today are not - or a wire to a ground rod.

Should I worry about damaging my components with electrostatic charge if electricity has never ran through the circuit?

Yes; it's the electricity generated by your body's motion rubbing insulating shoes, clothes, etc. together that causes it. So you can damage a part that you personally have never run electricity through. The parts HAVE had electricity through them when they're tested at the factory, FWIW.

How am I supposed to handle ESD sensitive devices while populating a board, cutting leads, and soldering?
You use a tests of reason.

You recognize that some devices are not terribly sensitive, like bipolar device (NPN, PNP, diodes, etc.) and ignore it. This will get you into trouble maybe once every 10,000 devices, so you may be dead first at the rate most of us use electronic devices, even me. So you acknowledge that it's simpler to replace one occasionally than to worry about it.

You recognize that most of the sensitive devices, like CMOS logic, has built-in immunity to static up to the level where an easy-to-hear "snap!" happens, and that CMOS jellybean logic and low-end microcontrollers are cheap. You'll sometimes have to replace one you killed. I ignore static electricity for the most part (exceptions below) and have never to my knowledge killed one.

You recognize that some devices have no built in immunity (MOSFETs, mostly) and that some are too expensive to risk it even if they are immune ( that new intel i7, which cost you $400 for instance) and take precautions.

The precautions vary by where  you live. Electrostatic discharge is by and large caused by low humidity. Humid air is a conductor, and static electricity cannot form at high humidities. In a rain forest jungle, it's substantially impossible to get static electricity by any means. In the Sahara, Arabian, Gobi, and Mexican deserts, it's almost impossible not to. In cold climates, that being  places where the air is heated and not by an open fire, the humidity can be very low indeed, so working on electronics in the winter time is cautionary, and this is where static is worst for us all.

The simple and direct way to prevent this can be (1) if you're worried about it and you have masonry floors, take your shoes off. Your bare feet conduct, and stone/concrete/tile/etc. floors conduct. You'll be discharged. Synthetic or wool socks left on will make it worse. If you are in a bad static place/time, raise the humidity. Go into your bathroom to work and turn on the shower so it's hot and steamy. Steamy air = no static.  Or you can put down a conductive floor mat, which must be grounded, wear an antistatic wrist band, which must be grounded, work at a workbench with a grounded metal frame and conductive work surface, which must be grounded, with tools that are either all metal, or have grounded tips for the soldering iron and three wire grounding plugs for the instruments.

[Be-Kind-Rewind]

PRR: Here are the parts numbers: 1N4148TR and 1N456A.

Thanks for the help R.G. and thanks for the info Taylor an PRR.

P.S. I'm building an Ampeg Scrampler clone.

[R.G.]

For those, I would give no consideration to electrostatic damage at all. They're relatively immune from anything you generate by simply touching them in normal circumstances. They might possibly, maybe, could happen, get damaged if you're wearing woolen clothes and plastic soled shoes on nylon carpet sitting in a synthetic cloth chair in a bone-dry atmosphere. But I doubt it. And they're cheap, relatively speaking.

[Be-Kind-Rewind]

Thats what I figured. Once again I am overly cautious.

Thanks R.G.

[phector2004]

well that's good to know!

it gets disgustingly humid here some days

a bit off topic, but how can you test the AC ground to see if its actually connected to anything? I've thought of using one of those wraps as a "fry my hand, not the rest of me" safeguard when working with higher voltages 

[PRR]

I can think of a "work place" where you "could" kill a '4148. Archive library, kept very dry to deter mildew, nylon carpets, and my friend was required to dress-up: leather shoes, nylon stockings, slip, and poly dress/pants-suit. Violent shocks when she walked across the carpet and touched metal cabinets. I made her a "shock ring", a 470K resistor which she would touch to the metal to slowly drain herself before touching with bare finger.

If instead it was a reversed small diode, she might have been able to kill a few.

As shown above, you don't really need to drain to "ground". That's done in large shops to keep everybody on the same level. But what you want is for all parts involved (including your body) to be at the SAME potential.

> while populating a board

As a general plan (not for a mere 1N4148), you stuff the tough stuff first. Resistors and caps. Then when the too-delicate MOS device goes in, the other parts will tend to absorb any static.

For all builds:

Grab the board first. If your "delicate" part is in an anti-stat bag, touch the INside of the bag while touching the board. Now you, the board, and the part are all the same potential. Take it out, stuff and solder. If you get called away for more than a minute, do the touch-everything again.

Further tips:

Try not to work when VERY dry. When I did old PC RAM in winter, I often boiled a pot of pasta to damp-up the air.

Wood is good. Unless you live in a desert, wood usually retains enough moisture so it won't hold charge. It may be good enough to just keep you and all your stuff on a wood (maybe not wood-grain plastic-surface) desk.

Don't wear silk. Nylon and poly are dubious too. My wardrobe is mostly cotton blend. Unless I OVER-dry the clothes in an electric dryer, cottons won't make or hold much of a charge. I do have to be aware of my chair, which is usually static-y... when I notice little zaps, I spray it with anti-stat. (The PC keyboard will often go brain-dead in winter when air is very dry, I walk up, sit down, and touch it.)

Anti-stat spray is a spoon of liquid Downey laundry softener in a quart of water in a spray bottle. (Shop-Rite generic works the same.... I think it's all the same barrel with different color and smell.) "Softener" really just holds moisture so fabric won't get dry and scratchy. This moisture also bleeds static. Works on chairs and carpets. It was my magic potion at work in winter when "PCs locked up".

But I often did none of this. Bakelite (ex-chem-lab) or Formica bench, negligible winter humidity, careless touching.... TL072 1N4148 PN3904 etc just don't die that easy. PC RAM can, and I always touched the case before the bag before the chip/stick.

I don't remember being "careful" around CMOS. Even way back when, CMOS had a resistor and three diodes protecting the glass Gate. TTL, bah, can't hurt the stuff. I must admit I loved RTL: awful slow, small fanout, few functions, but mighty tough.

Don't wear silk nor shuffle across carpet and grab parts. If you are in the desert, use your swamp cooler. Otherwise, for nearly all audio parts, static is the least of your worries.

[PRR]

> using one of those wraps as a "fry my hand, not the rest of me" safeguard when working with higher voltages

No.

They have a ~~1Meg resistor so that users WON'T get electrocuted. This will still dissipate the few-pFd of static charge involved in static-damage.

If both the strap and your body are grounded: the strap is 1Meg. Your body is (say) 100K. The current splits about 10%/90%.... you still get 90% of the shock-current you feared.