Static discharge from silicone soldering mat? - Page 1
Forum section: electronics / general

author: Rooster Cogburn
author_rank: Regular Contributor
timestamp: January 24, 2025, 11:09:45 am
content: For years my work surface has consisted of a grounded ESD safe mat......with a silicone soldering mat on top. Here:I bought this soldering mat IIRC on AliExpress years ago, has a 'BTSHOW' logo in the bottom corner:The green ESD mat is not quite as heat resistant and sturdy as the blue silicone soldering mat, so if I'm doing something that doesn't strike me as particularly ESD safety critical I keep the silicone mat on top to safe the more fragile and expensive grounded mat from wear.I really like this setup and it has saved me well for years, but the blue soldering mat is pretty beat up after loads of cuts and some accidents with glue and other substances, so I thought I'd get a new one. To me the form factor and the parts bins at the top are absolutely perfect so I tried to get another one like it. I ended up buying this 'WELDINGER' soldering mat from an eBay seller:https://weldinger.de/WELDINGER-Loetmatte-Silikon-30x40-cm-hitzebestaendig-bis-550C-LoetunterlageSeems pretty much identical. Really like the mustard color, contrast very well with whatever I put on it.Pretty much immediately I noticed a strange issue, though. When picking up the mat I hear a strange 'crackle', like starting discharge. This only happens after the mat stays put for a while, not every time I pick it up. I was very confused by this, how could a silicone mat generate static electricity like a balloon while in contact with a grounded ESD mat? I searched a bit with the old Google and found some comments on reddit:https://www.reddit.com/r/AskElectronics/comments/wq1u4a/are_these_anti_static_mats_anti_static/Huh. Is this indeed normal? This has never happened with the old blue mat. I'm a bit worried that my new soldering mat will fry my work pieces with static electricity when I pick it up. Should I be worried? Should I buy something else instead?Thanks!

author: Simmed
author_rank: Frequent Contributor
timestamp: January 24, 2025, 11:19:07 am
content: have you measured the surface resistance ?

author: Rooster Cogburn
author_rank: Regular Contributor
timestamp: January 24, 2025, 02:51:49 pm
content: Quote from: Simmed on January 24, 2025, 11:19:07 amI don't have such equipment and this is not an antistatic mat so it shouldn't be conductive anyway. My question is, why do these mats produce 'sparks' or crackling sounds when lifted and why does my old one not do that? Do I need to be worried about this? How do I identify mats which do and do not do this?

author: tooki
author_rank: Super Contributor
timestamp: January 24, 2025, 02:54:29 pm
content: Quote from: Rooster Cogburn on January 24, 2025, 11:09:45 amBecause silicone is a really, really good insulator. The ESD mat can only discharge charge that can flow to it. But the silicone is such a good insulator that whatever charge accumulates on one side cannot flow to the other, so the charge isn’t in contact with the mat. You basically have a physically enormous capacitor with charge accumulated on each side of the dielectric.Your blue silicone mat must have some antistatic additive which makes it ever so slightly conductive.Also, different materials create and hold different charges. It’s possible the silicone itself has a different composition that causes it to generate more static to begin with.Quote from: Rooster Cogburn on January 24, 2025, 11:09:45 amI definitely would not use it for electronics.Bear in mind that it really shouldn’t be necessary to have the silicone mat over the ESD mat. ESD mats are tough, and last for decades under normal use. Silicone is generally much, much more delicate, which is why your blue mat got cuts that would not have bothered the ESD mat. For using glue and stuff, just lay out paper or cardboard* on top: it’s conductive enough to be ESD-safe.*not laminated with plastic

author: Rooster Cogburn
author_rank: Regular Contributor
timestamp: January 24, 2025, 03:12:34 pm
content: Looks like I really messed up and bought a very wrong product here. Ironically the priciest work mat I've bought so farI unfortunately can't buy the original blue one anymore, it was years ago and is no longer available.I have a couple of conductive ESD mats, but they are all rather fragile. The blue ones are not heat resistant at all. I currently use a green one that is kinda, sorta heat resistant. Maybe up to 300C and then it slowly takes damage. I don't like to use hot air on it. All of them have a rather fragile finish.It was all cheap AliExpress crap. I'm just an amateur hobbyist, nothing I own is fancy or particularly good. Guess I need to find a real supplier of proper ESD mats.Thanks everybody!

author: tooki
author_rank: Super Contributor
timestamp: January 24, 2025, 03:28:21 pm
content: Quote from: Rooster Cogburn on January 24, 2025, 03:12:34 pmESD mats are made of rubber and vinyl (PVC), so they are not infinitely heatproof. But that isn’t their job, either.For hot air, it’s better to raise the board off the bench anyway, so the bench (with mat) isn’t sucking away all your heat! Best case scenario you’ve actually got a board preheater underneath (infrared or hot air). But even without that, you’re better off having the board held off the bench, since air itself is a fairly good thermal insulator. Depending on the board, I simply use my good “helping hands”, or I will screw on some standoffs.A great thing to use if you just need to thermally protect your bench while soldering is a completely bare PCB (that is, a sheet of FR-4 with no copper at all). I also have a frosted glass tile I use for some things. Both of these things aren’t conductive, but they also don’t really generate static charge, either.I really wish someone would make one of those silicone mats out of properly conductive silicone rubber. The little pockets for screws and stuff are great.

author: Rooster Cogburn
author_rank: Regular Contributor
timestamp: January 24, 2025, 03:44:56 pm
content: Quote from: tooki on January 24, 2025, 03:28:21 pmAh Ok, that's good to know. So there's nothing wrong with mine in general and buying a more expensive one won't fix that.What I like about the silicone mats is that they are completely heat resistant, I never damaged it with hot air or the iron. Just years of wear from tools, glue, paint etc. finally got it to a state where I wanted to replace it. Held up well.Quote from: tooki on January 24, 2025, 03:28:21 pmYes! I'd really really miss that. I was thinking maybe I should just cut the top part off and keep using that for organizing stuff when I take things apart.Also, I really like that orange color of the new mat. I thought at first it would've been too obnoxious, but it actually looks very nice as it's such a contrast to everything else. If I could get this mat with some conductive bits sprinkled in I'd be very happy.

author: timeandfrequency
author_rank: Frequent Contributor
timestamp: January 24, 2025, 03:53:33 pm
content: Hello Rooster Cogburn,As other members underscored, the cheap silicon mats are not ESD safe.Some videos :Noel's Retro Lab :https://www.youtube.com/watch?v=dR8nqJzrnSg (start watching at 13:23) (edit URL to remove space characters)Kerry Wong :https://www.youtube.com/watch?v=TOpS90tCHSc (edit URL to remove space characters).I bought this light blueESD mat.It withstands heat. I deliberately dropped some solder on it : no marks or holes. Resistance to chemicals is good : the mat can be cleaned with alcohol or acetone if very dirty.There are 2 male snaps at two of the four corners which makes it easy to connect to ground. The rubber is neither too soft nor too hard (shore A: 75).From an electrical point of view, I tested its surface resistivity and I was able to confirm the value given by theproduct datasheet, namely '< 1 x 109Ohms', which corresponds to the definition of a so-called 'static dissipative' surface (dissipates static charges). And that's exactly what we want.The verification of the surface resistivity was carried out by using this dedicatedyellow device from Vermason, with the following test conditions:• Test voltage: 100 VDC (device auto selects this voltage)• Relative humidity: 32 %• Ambient temperature: 29.5°CAs mentioned above, silicone soldering mats (often blue) which are universally used by dozens of DIYers/YouTubers are not antistatic. Measuring theirsurface resistivity, by using the same device as above, gives a result '> 1 x 1012Ohms', which corresponds to the definition of an 'insulative' (insulating) surface.This is NOT suitable for handling active electronic components. But you can still use your mustard silicon mat while soldering connectors or switches...

author: tooki
author_rank: Super Contributor
timestamp: January 24, 2025, 04:12:26 pm
content: Quote from: Rooster Cogburn on January 24, 2025, 03:44:56 pmYep, silicone is wonderful in that regard. (It does not melt, period: at some point it catches fire and leaves behind white, incredibly fine ashes. But you have to heat it FAR, FAR beyond soldering temperatures to do that. Holding silicone insulated wire in a flame is a way to get an idea of this.) The fact that silicone neither melts in heat nor gets stiff when cold is why silicone wire is so beloved for test leads.It’s also resistant to many chemicals, and most things won’t stick to it either. So it’s also great in that regard.Hence why I wish someone would make a properly ESD-safe silicone mat. It’s certainly possible — desoldering stations use ESD-safe silicone hose for the vacuum. So the material exists. Someone just needs to do it. :/Unfortunately what we get instead is crapclaimingto be ESD-safe without actually being it. :'(Rather than cutting off the top, why not just make little containers out of metal or wood? (Or ESD-safe plastic, using a 3D printer.) I’ve actually been meaning to do exactly that: I want to take a little block of perhaps 8mm thick aluminum and mill little pockets into it.But what I use at home for now is actually a watercolor paint mixing palette I picked up at the local art supply shop. It’s made of porcelain. As such, it’s antistatic, insulating, and also heavy enough to not slide around by accident. I don’t remember what it cost but it wasn’t a lot. Google “ceramic watercolor palette” to see the huge array of such things that exist.

author: tooki
author_rank: Super Contributor
timestamp: January 24, 2025, 04:13:58 pm
content: Also, one other huge problem with staticky silicone mats: they attract dust horribly, making them almost impossible to keep clean. You can wash them with soap and water and they’ll be super clean — for about 10 minutes.

author: Rooster Cogburn
author_rank: Regular Contributor
timestamp: January 24, 2025, 06:14:18 pm
content: Quote from: tooki on January 24, 2025, 04:13:58 pmOh yeah, the little parts tray always has dust in the corners. I occasionally clean the mat in the sink, but it's dusty again immediately.Quote from: timeandfrequency on January 24, 2025, 03:53:33 pmThis looks good, need to find a smaller one, though. My current mat is 50x40cm, I can increase the depth from 40 to 60cm, but more won't fit in my workspace. Welectron also sells reasonably priced ones, still too large:https://www.welectron.com/SafeGuard-Premium-ESD-Table-MatNot sure how easy those are to cut to size, if they have any special edge finish I don't want to ruin by cutting them up.Quote from: timeandfrequency on January 24, 2025, 03:53:33 pmI got to be honest, I don't have really have a good understanding when something requires an ESD safe setup. I have a grounded mat and strap and all my tools are grounded as well. I generally only remove my silicone mat when I do something presumably sensitive, like swap a chip between two boards and such. I recently desoldered a broken switch from a CD player and bridged the connection, figured that would be fine without special grounding. I always assume components on a PCB are not that susceptible to zaps, maybe this is wrong?Quote from: tooki on January 24, 2025, 04:12:26 pmI think it would be really neat if I could buy a cheap & disposable ESD-safe silicone mat that I can keep putting on top of my regular one whenever I do something that might be damaging :/Quote from: tooki on January 24, 2025, 04:12:26 pmI like those watercolor palettes, plenty of options to chose from!

author: timeandfrequency
author_rank: Frequent Contributor
timestamp: January 24, 2025, 08:10:55 pm
content: Quote from: Rooster Cogburn on January 24, 2025, 06:14:18 pmNot a problem at all : the mentionned mat can be resized with a vanilla X'Acto knife. No special edge finish either.Shore A 75 is just mild rubber.

author: thm_w
author_rank: Super Contributor
timestamp: January 24, 2025, 11:10:55 pm
content: https://www.eevblog.com/forum/reviews/silicon-heat-resistant-mats-vs-esd-safety/Quote from: Rooster Cogburn on January 24, 2025, 06:14:18 pmThats something you figure out for yourself, assuming you are working at home and not somewhere with a company policy. Based on risk tolerance, and also clothing and humidity.Components on a PCB are still susceptible to ESD, just usually less so, as there are other places the energy can go (power rails, planes, whatever), build in ESD diodes can do what they are intended to do.I have an ESD mat and a normal silicone mat on top for temperature resistance, no wrist strap. But I'm working on consumer level gear, and parts that can be cheaply replaced if they fail. These devices get far far worse treatment in the field (lightning strikes, etc.).

author: Rooster Cogburn
author_rank: Regular Contributor
timestamp: January 25, 2025, 01:54:14 pm
content: Quote from: timeandfrequency on January 24, 2025, 08:10:55 pmGreat, thanks! The mats I have so far are cheap stuff and clearly just cut from a big roll.Quote from: thm_w on January 24, 2025, 11:10:55 pmOk, interesting data point! I'd say the biggest threat to devices on my bench is my own incompetence and that'll likely remain for the foreseeable future. I mostly repair consumer electronics from the 80s, 90s and 2000s, stuff like game consoles, CRT TVs, HiFi/Stereo stuff like amps and discman, etc. Humidity is generally high in Germany, can't even remember the last time I had static build up to a level where I felt a zap.