Pink bags - don't rely on them!

[Ed Oscuro]

A bit long-ish video by Dave Jones on the EEVblog, but well worth watching.

The short take-away:

Pink antistatic bags will not directly build up charges through handling - however if you hold onto one of these bags while handing a device and charged up, you could possibly kill your board or individual components on it.

Obvious caveats: Fully populated boards take shocks better than do individual components, and boards / devices from years back should also generally be more resistant to shocks as well. Also, if you have always treated the pink bags as just a prophylactic, but still made sure not to get charged up with electricity yourself, and tried not to touch the board through the plastic any more than necessary, the risk should be reduced still further.

But the take-away here is that you absolutely should invest in a proper metalized static shielding bag with capacitive properties.

[Xan]

Never came across those ones. I use these, don't know if they are ideal though: http://www.hiwtc.com/photo/products/29/00/00/96.jpg

[Ed Oscuro]

I'm not familiar with all the material types that could go into making the anti-charge materials (pink and green), and the manufacturer's site is very vague - but it certainly looks like it's supposed to stand in as the real thing. So probably that is okay.

[cfx]

.

[Ed Oscuro]

Yes, I mean more the possibility that some dodgy manufacturer claims something is what it isn't.

Generally speaking, the more rigid-feeling, slightly gray / silvery bags which are semi-transparent and marked for anti-static properties are precisely what we want.

Finding them in large enough sizes for some big multi-layer PCBs will be a challenge though! There are anti-static pads which could also be sufficient for this use. Also, I bet the pink foam should normally be good if it is thick enough that static charges don't get into it.

[ChuChu Flamingo]

Those pink bags suck anyhow, no cushion at all. Pink bubble wrap or those ESD boxes seem to be the best bet for storing pcbs.

[Ed Oscuro]

Pink bubble wrap or those ESD boxes seem to be the best bet for storing pcbs.

Pink bubble wrap is going to improve protection on average by increasing the distance a charge would have to travel to zap a component...but otherwise exactly the same, and on top of that it's a pain to unwind that stuff (unless you have it taped into a kind of sleeve beforehand. ESD boxes can't be too cheap but I would like to get some more of those; thanks for the reminder.

[eightbitminiboss]

I work in the hard drive industry and I'm always surrounded by ESD safe material. I haven't seen any of the pink bags here, just the pink bubble wrap for stuff that's already in the standard silver ESD bags. Even have smocks and ESD self testing stations and ionizers. The whole shebang.

[ChuChu Flamingo]

Pink bubble wrap or those ESD boxes seem to be the best bet for storing pcbs.

Pink bubble wrap is going to improve protection on average by increasing the distance a charge would have to travel to zap a component...but otherwise exactly the same, and on top of that it's a pain to unwind that stuff (unless you have it taped into a kind of sleeve beforehand. ESD boxes can't be too cheap but I would like to get some more of those; thanks for the reminder.

The real danger with static charges is letting them build up to 10k+ volts. Most static electricity around us is below 1500. If it is above that, you will usually feel the zap/do cool raiden thunder zap thingy.

Pcb components can usually take 2000-2500 volts iirc (although it might reduce the lifespan). Also more humidity means less static electricity. It can get as high as 10k if the place you live in is really dry.

Finding a ESD box is easy, but one that fits all is not. Good look with CPS1 boards or any dual layered ones without modifications. These are the ones I see recommended.

http://www.uline.com/BL_2355/ESD-Protective-Shippers

S-7580 is probably the one you want.

Also keep in mind we aren't shocking our pcbs with a volt shocker. Just be smart and touch a grounded metal object before touching your pcbs. And by grounded, I mean something plugged in that is grounded to your electrical wiring.

[Ed Oscuro]

Pcb components can usually take 2000-2500 volts iirc (although it might reduce the lifespan).

No, I am going to say this is completely misleading.

First, 2000-2500 volts is below "the human threshold for feeling an electrostatic discharge," which is 3000 (source). Some devices can withstand such events, but anything that you feel as a zap is almost certainly doing damage to any but the largest devices, whether in a populated board or not.

TI refers to "walking wounded" devices. When you say "reduce the lifespan," what that actually translates to is alteration of the device's function (as mentioned in the Vishay document above), and even if not that, as hidden damage to the device. Think of this as being analogous to thermal cycling - eventually we know that joints can crack from this. In fact, with ESD events, the punch of the charge through a layer, or temporarily melting some material in the device, is pulling the device closer and closer to failing - perhaps some internal pathways inside the trace are going to short out or fail to make contact.

There is a lot more that could be said - such as where the discharge happens and how. For example, if you get a board with a charge built up on it from bouncing around in the middle of a bunch of packing peanuts through shipping, and then you touch the board - you were not the source of the charge, the board was. And even years ago it was found that strips of devices were having higher than normal failure rates during manufacturing because the entire strip of devices was becoming charged, and that entire charge zapped out through one pin of one of the devices - rendering it quite dead.

This happens without the person handling the device having apparently done anything wrong at all, and it is why the pink bags / pink bubble wrap are still of some use in shipping and handling, or even just storage.

Finally, the age of most PCBs works both for and against them. As far as I know, many arcade PCBs (and retrogaming devices in general) were probably not designed with much in the way of ESD protection. But there are some positive aspects too: There is the mandatory distance from the edge of the PCB (well, aside from connectors) to the first traces and components, which users should always be careful to make use of. The older devices were generally just larger and have more capacity to dissipate charge and heat. For people working with modern devices (especially SMD ones...well, that covers about all of them really), there is definitely less leeway to be careless now. I have at least a pretty good record assembling new PCs in January (I've only ever had one board fail, and that was only a strange partial failure - no power to the GPU, but working otherwise), but I don't have to handle them repeatedly either, and they're also made with the understanding that there needs to be some ESD protection built in (resistors and fuses on lines that look tasty to ESD pulses, basically).

Also keep in mind we aren't shocking our pcbs with a volt shocker.

Yes, but keep in mind the intention of the demo, which was to quickly prove that some kinds of "anti-static" (in this case, non-generating) materials don't shield from ESD at all. The actual amount of volts and repeated shocks required to kill the timer chip was naturally lower than what was shown. We don't really know how much voltage or attempts actually were needed to overcome that timer chip, and we also don't know what would have happened if he just zapped it repeatedly with something at a much lower but still dangerously overspec voltage, like 500V.

Just be smart and touch a grounded metal object before touching your pcbs.

As mentioned before, this may not be good enough (so take care when pulling something out of a box, or packing it). I already have the habit of trying only to hold the board edges - which in any good design will have some distance from the copper traces and components to help prevent just this kind of thing. I also think that not wearing clothes that could generate a lot of static (i.e., shortsleeves) could help too.

There are a lot of people who say "it died in storage" or "it was working when I sent it out." They don't make (or choose not to make) the connection between their shitty bubble wrap packaging and the fact that the next use, or the recipient, never got it to go at all!

And by grounded, I mean something plugged in that is grounded to your electrical wiring.

Ground can mean just that. Some of the most effective grounds in my house are actually architectural - thin strips of metal just below the plaster at the corner of a wall, or metal supports underneath the main floor. Of course, if you don't actually have a proper ground in the wiring, then it's no good at all.