Truly antistatic bag? - Page 1
Forum section: electronics / beginners

author: kcs
author_rank: Regular Contributor
timestamp: May 29, 2019, 01:19:22 am
content: Is there any way to verify if a bag or a bubble wrap is truly antistatic or is it just a regular bag (bubble wrap) painted with pink color without using any specialized tools like surface voltage meter etc?As I understand, the key here is to make sure it does not build up a charge. Wiki says that a true antistatic bag should "conduct the charge to atmosphere", but it does not specify how quickly it supposed to happen.How would you test it?

author: jeremy
author_rank: Super Contributor
timestamp: May 29, 2019, 01:42:42 am
content: There are two kinds of bags: “static dissipative” ones (silver) and “anti-static” (pink/blue). Unfortunately these terms are sometimes used interchangeably. I don’t believe anti-static bags (pink/blue) are actually supposed to discharge any more than any other plastic bags, they just resist the buildup of triboelectric charge in the first place. So perhaps you could try to rub it on some wool and see if it holds a charge?

author: KL27x
author_rank: Super Contributor
timestamp: May 29, 2019, 01:54:55 am
content: I believe the silver ones have highly conductive interior that acts like a faraday cage. I dunno what's in it. Maybe some fine foil between two layers of PE or something? They are very resistant to elastic and plastic deformation, and I have heard them called "metallized bags." But it might have been myself that dubbed them with this name.I think they are all, pink or silver, coated with stuff to dissipate static charge.

author: Rick Law
author_rank: Super Contributor
timestamp: May 29, 2019, 02:04:39 am
content: How about just wrapping it with aluminum foil?

author: Monkeh
author_rank: Super Contributor
timestamp: May 29, 2019, 02:08:42 am
content: Quote from: jeremy on May 29, 2019, 01:42:42 amThe pink bags are dissipative. The 'silver' (metallised) ones are shielding.

author: Berni
author_rank: Super Contributor
timestamp: May 29, 2019, 06:25:05 am
content: The pink/blue ones are just made to not build a static charge when rubbed. They don't protect from any outside ESD. I suppose if you wanted to test one you could rub it against a woolly sweater and see if it will stick to stuff.The only bags that are actually antistatic are the ones that are silver or sometimes black. These have a conductive layer inside. You can't really measure it with a multimeter, but you can use a piezzo igniter to create a spark and see if it jumps to the bag when you hold it.

author: kcs
author_rank: Regular Contributor
timestamp: May 29, 2019, 05:44:17 pm
content: Quote from: jeremy on May 29, 2019, 01:42:42 amThat's what I did. I have tried rubbing a regular bag, a regular bubble wrap, a bubble wrap in question (it was listed as antistatic) and a genuine pink antistatic bag. Only the last one did not attract human hair after being rubbed. Is it a conclusive test?Seller has sold over 200 pieces of this antistatic material and has no negative feedback. I have contacted the seller and I was told that manufacturer confirms it is antistatic. Of course, no certificates of conformance were provided.

author: ejeffrey
author_rank: Super Contributor
timestamp: May 29, 2019, 06:38:06 pm
content: Yes, if you rub it and it attracts paper or hair it isn't static dissipative.

author: KL27x
author_rank: Super Contributor
timestamp: May 29, 2019, 07:53:42 pm
content: QuoteThe pink ones are anti-static, too. They protect from outside ESD just as much as the silver ones. The foil bags have an insulating plastic layer (ESD treated) that makes them not much different than the pink ones at ESD protection. The internal conductive foil protects the contents of a silver bag from induced current. It's additional "EMP protection." At least, I don't think the foil is needed to prevent ESD from zapping through 2-3 mils of PE insulating plastic??

author: Mr. Scram
author_rank: Super Contributor
timestamp: May 29, 2019, 07:59:03 pm
content: The problem is that there could be a significant charge without much visibly happening. The answer is using a meter like Dave has used in a number of his videos on ESD. They're fairly expensive meters but can occasionally be snagged on Ebay for a fraction of their original cost. They're comparatively rare though.

author: Mr. Scram
author_rank: Super Contributor
timestamp: May 29, 2019, 08:01:04 pm
content: Quote from: KL27x on May 29, 2019, 07:53:42 pmThat's not what Dave explained in his video. The pink ones are treated not to generate ESD, but won't stop parts inside from being zapped through the bag by an external charge.

author: KL27x
author_rank: Super Contributor
timestamp: May 29, 2019, 08:33:10 pm
content: Yeah, ok. The pink ones can't stop ESD discharge through the bag, but they dissipate surface charge. Which makes them antistatic bags, but not ESD shielded/proof bags?Not being completely ESD-proof doesn't mean they aren't giving significant protection from ESD, either. Dave has a pretty hard time to kill the chip through the bag using his piezo sparker right across the chip. I think it provides significant protection. As Dave says, the air gap and insulation is there. And dissipative coating makes the contents less likely to be the recipient of an ESD in the first place. Plus cardboard box. But10kV can spark across 1cm of air... ok. The box is several cm of air. If the chips got in there in good shape, they are gonna come out in good shape.A (maybe bigger?) problem with a regular plastic bag is an unprotected chip like a FET or a laser diode sliding around in there can die from static/triboelectric buildup.

author: kcs
author_rank: Regular Contributor
timestamp: May 29, 2019, 09:17:42 pm
content: It is not worth for me to buy specialized tools and test if material has antistatic properties or not as it is one time purchase.I found it extremely hard to purchase small quantity of wide (>1 m) antistatic bubble wrap or shielding film. I thought I was lucky when I found one listed on eBay.So, watch out for "antistatic" bags and bubble wraps sold on eBay. Just because it is pink, it does not make it antistatic.

author: ejeffrey
author_rank: Super Contributor
timestamp: May 29, 2019, 09:28:36 pm
content: Quote from: KL27x on May 29, 2019, 08:33:10 pmYes. The silver bags provide a barrier that protects the things inside the bag from static discharge outside the bag. The bag doesn't protect its contents against static buildup inside the bag. That is why everything that goes inside the silver bag needs to be static dissapative (or anti-static). Hence the pink bags, bubble wrap, foam, etc. They are safe to use as packaging inside the protected area.It is the same thing with an ESD workstation. You don't want to bring materials into the work area that can hold a static charge into the ESD safe area. So when you receive your box from digikey, you are supposed to unpack it *outside* the ESD work area, then bring the silver bags (and only the silver bags) to your workstation, then open and unpack them there. Likewise, non-ESD sensitive parts like resistors and capacitors should still be packed in static dissapative bags so that you can safely bring them into your ESD workspace without damaging other components.Of course this is all the ideal practice. It is important for production areas, or when working with high sensitivity devices like laser diodes and GHz amplifiers. What you do in your home workshop is up to you.

author: KL27x
author_rank: Super Contributor
timestamp: May 29, 2019, 09:38:55 pm
content: ^Agreed.But I am gonna challenge this one sentence.QuoteI would think the silver ones have more or less the exact same antistatic dissipative surface treatment as the pink ones. If I have a handful of IC and no proper tube, I put them naked in the silver bags.WikipediaQuoteI don't like the last sentence.... shielding the contents fromstatic chargeelectrostatic discharge via a Faraday cage. Protection from low voltage/curent by dielectric properties of PET. And protection from surface charge buildup by virtue of dissipative coating.Interesting:QuoteI would have thought the antistatic coating would be what wore off/out.

author: Illusionist
author_rank: Regular Contributor
timestamp: May 30, 2019, 08:57:51 pm
content: I always thought the metalised, silver bags (which are usually metalised Mylar® (a polyester from Dupont)) are mostly intended to be vacuum and heat sealed to protect the contents from moisture.I've received a lot of component samples packed that way, with instructions to bake before soldering if opened for too long beforehand or if the packet was compromised.The aluminium layer between the polyester sheets is a moisture and air barrier. The polyester itself is surprisingly bad at that. The be static dissipative, the bags still need a surface coating.It's also used to seal food for long term storage for the same reasons. Off topic, but yesterday I opened a 5kg bag of barley that I sealed that way myself seven years ago. It's still perfect.

author: ejeffrey
author_rank: Super Contributor
timestamp: May 30, 2019, 10:22:30 pm
content: Quote from: KL27x on May 29, 2019, 09:38:55 pmYes, my point was that _if_ you need to put other packaging materials (bags, foam, bubble wrap) inside the shielding bag, you want that to be static dissipative, otherwise it could damage your components and the outer bag can't effectively protect against that.

author: Monkeh
author_rank: Super Contributor
timestamp: May 30, 2019, 10:32:54 pm
content: Quote from: Illusionist on May 30, 2019, 08:57:51 pmThe moisture barrier bags are another type again. Standard shielding bags are transparent but silvery or grey - it's a sputtered metal layer, not a full one. It's basically a thin film resistor in bag form. The fully metallised ones are, as you say, moisture barriers.