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Static discharge from silicone soldering mat?
Rooster Cogburn:
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-Loetunterlage
Seems 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!
Simmed:
have you measured the surface resistance ?
Rooster Cogburn:
--- Quote from: Simmed on January 24, 2025, 11:19:07 am ---have you measured the surface resistance ?
--- End quote ---
I 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?
tooki:
--- Quote from: Rooster Cogburn on January 24, 2025, 11:09:45 am ---…how could a silicone mat generate static electricity like a balloon while in contact with a grounded ESD mat?
--- End quote ---
Because 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 am ---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?
--- End quote ---
I 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
Rooster Cogburn:
Looks like I really messed up and bought a very wrong product here. Ironically the priciest work mat I've bought so far :palm: I 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!
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