the rubber one thats real tough and fire proof. not the soft ones. The good ones are expensive and like tire rubber.
The thing is if you use anything other then the no-clean really clear clean flux from kester meant for brand new PCBs it will like cosmetically wreck a ESD mat. I had to sand mine down with a oscillating sander to get it kinda clean. Also if you do something like over heat a heatsink laying on it for a long period of time it will discolor and they can char but its pretty robust. But I had like 6 years of epoxy, other glue, oil, flux, etc on it (it got cleaned with rubbing alcohol sometimes)...
What you need to do is like a marble counter top, but its hard because electronics is super frustrating, especially if some complicated dead bug fucks up, is to clean it immediately after it gets soiled. If you develop the habit of amputating flux covered fried or misbehaving or other parts and kinda brushing them aside on your ESD mat trying to work fast its gonna get ugly quick.
When I was newer I would be more careful and handle everything with tweezers and stuff but most of my problems came about because I got pressed for time or attempted hard projects that frustrated me (by time I mean stuff like deadlines for professors, or trying to figure shit out for work (on my own time), etc).
My suggestions:
1) Buy rubber
2) buy a bit more then you need then keep a sacrificial bit (like a 14x14 square) that you can also ground for doing soldering on, particularly if you dead-bug stuff. Even if its in a protoboard it will absorb the splatter you get sometimes from boiling lead.
3) get proper flux bottles. That means don't handle your big bottle of flux over your mat, even if its an ounce. And don't use syringes that get crusty. Get a small properly sealing container, like 5mL or less, with a solid needle (the needle came out of my shitty flux bottle before). Make sure it delicately dispenses flux. If its volitile flux make sure you don't open it up with flux at the tip with vapor behind it that it squirts on your mat. I am curious if those radio-shack dispenser syringes for oil work well in this case but I never tried it. *i hate flux pens and don't use them*
4) get a good brand high quality alcohol dispenser (look it up)
5) Use your sacrificial mat for applying glues if you need to apply glue to a PCB in a setting. Same shit goes for glue tubes and glues don't be messing with pressurized containers that can splatter all over the place near your expensive ESD protection system.
6) check the grounds with a outlet tester.
7) get a proper fastener, the ones that penetrate with four teeth like a directional/navigational mark on a map suck for the rubber ones. It should be fastened with bolts otherwise they get loose. They might work for the soft mats.
don't leave stuff out on it for a long period of time, they are sensitive to light or pressure or something and if you leave something pressing on it for 6 months then move it you get a discoloration spot. It looks better when it ages evenly.
9) Don't rely on a plug. Inspect the outlet, test it with a ground tester (don't trust your parents or land lord I got fucked by this. Also, get a good connection with a crown washer that screws into the baseplate for the ground connection
10) test the resistors in the wrist strap and the ground mat, give it a bit of a jiggle and stuff to make sure its good
11) immediately clean any drippings, glue, solder splatter, etc. Having a proper lab alcohol bottle and wipes and q-tips and other shit to use with it on hand is important.
12) the good ESD mats have a grooved texture. It's kinda difficult to clean with brushes or towels from physical debris like trimmed wires, trimmed solder joints *don't do this*, bits of insulation, fine wire strands from cutting wires etc. I recommend some kind of hand held vacuum cleaner for keeping it clean. I don't have a good one I like yet (the milwakee offerings are large and very loud). I have seen on youtube in those '10 amazing gadget' videos there is some small vacuum cleaner that has a similar form factor to something like a battery powered wood sander, very nice and shmick if it works well.. can't wait
Implementation tips:
1) cleaning supplies and shit take up valuable bench space (tissues, shop towel, q-tip, sponge), if you have a typical made it yourself bench out of 2x4's and plywood that you did some light work on, don't forget about the underside of the table. You can take like a thin cookie tin that has a removable lid, screw the lid on to bottom of your work bench, deform it a bit and slap some hard drive magnets in there and then the actual storage portion of the box will actually hold tightly under the table by itself but still be removable so long its not loaded with heavy crap. It's great for storing cleaning items you don't need often but need to have on hand when you work in case of a faux 'emergency' that would other wise go ignored (oh its just a little spot I am not getting up to go to the medicine cabinet).
2) get into the habit of wearing gloves when you use glues so you don't spread stuff with dirty hands
Also very important tangential:
make appropriate waste containers:
1) metal for parts you want to reuse but are dirty with flux, like if you solder in the wrong resistor into a circuit and you need to change it out, or you find with experimentation its the wrong value etc. During a experiment put all your dirty stuff here, then later you can clean it (preferably ultrasonic, also maybe get excess solder off with a wick or something), dry it, store it properly
2) non dirty parts temporary storage, like if you get a op-amp out from your kit and you decide its the wrong part, you don;'t want it loose on your bench so you put it in a clean container. Or if you cut the wrong size wire, pull a screw, etc.
3) garbage you don't care about. You can sort this into two bins too, clean and dirty, because what you end up with is like (clean) : insulation, pieces of zip ties, burned things from a bread board, etc.. and dirty shit that for some reason usually ends up being jagged. The only reason is that if you have flux-clean trash you can empty it into a trash can or something in your lab that you don't use bags with. Dump the flux trash in there and it will stick to the walls and piss you off when you go to clean the trash and there is some flux covered dusty turd stuck firmly to the side of a trash can. The fluxed trash you can dump into a receptacle that uses a bag liner
4) glue trash. This is kind of irritating, usually what I mean is mixing sticks covered with glue and whatever stuff you mixed your epoxy on, you want a liner for this can since you can't easily clean it out with a brillo pad like the flux covered trash one. I don't have one of these (usually I just treat it like hot stuff and go into a different room to throw it out, but I think a good solution would be to get a open container that can hold zip-lock bags (like the low grade cheap zip-locks that are meant for putting pretzels or carrots or something into for giving your kid a school snack, I think they are called 'snack bags'. If the bag can deploy over the container, you can break any glue sticks in half and throw mixing cups and stuff in there and then seal it so your lab does not smell like epoxy, it will still cure in the bag and will be rendered inert as an allergen.
5) temporary glue storage. Not sure, I usually use something I can throw out, but I wonder if a silicone mat would work here (like a piece of baking mat), which you can lay your glue spreader on while you are not holding it... what you don't wanna do is get creative with leaving a glue stick delicately propped up against some power resistors and hope its viscous enough not to drip
6) now here is the irritating mother fucker: solvents disposal. Now you will accumulate high concentration alcohol and acetone cleaning wipes often impregnated with other flammable things like oils. You can let this crap air dry and stink the joint up or put it into a sealed container where it remains a hazard till you soak it with water to dilute it to a point where it won't burn and will evaporate off in a nonflammable manner. This is not directly related to ESD mats but I described these procedures that will lead to an accumulation of this crap, and its irritating because it smells bad so you might lead to improper cleaning. You can throw it into a container of water but its irritating to dispose of because you end up with this water logged decomposing pile of soaked crap floating in a container of water. You forget and it can mold off on you. You need a soak bottle to dilute the solvents to non-flammable levels, then what I recommend is throwing it out the window. I have a gravel bed outside of my lab window so its fairly safe there, but what I would recommend is to get a wire basket, pen organizer (wire mesh type) or other container with a lid thats hanged outside of your lab window or near a extraction vent, so you can throw the stuff out there to dry and be safe from being abducted by the wind, and then later you can throw it out as dry waste. Obviously don't throw a towel dripping with pure acetone out the window or directly into a drying rack, soak it with a squirt bottle first to dilute it where its not a super hazard. I recommend lab solvent bottles for storing water. Don't store alcohol or solvents in them because its dangerous because of their vapor pressure, use a metered alcohol dispenser. Put a small roof over it to protect against light rain etc. If its storming outside you might need to go to your kitchen sink and rinse it out properly, as much of a pain as it is. Always transport solvent dirty stuff on trays so you don't end up dropping it or getting drips on the floor which will make short work out of varnish and other coatings on fine furniture, wood, stairs, etc.
I do not recommend you do this unless you have a masonry wall around your house incase you forget to dilute. Keep in mind if its just a vernier you can still heat the wood under the masonry if there is a strong fire on the side of it. It's very unlikely but still you don't wanna burn your house down in the most stupid ass way possible. Some kind of heat shield like a larger bucket (think metal fire pale/fire bucket with sand) could work as a enclosure and heat shield for your house if the contents of the towels some how ignite. Keep in mind you can get drops of burning solvent going down so make sure there is nothing flammable like leaves on the ground under it, but if you soak it it should evaporate in a non-flammable but still smelly concentration.
****weigh all these containers down so you don't knock em over. Tempting to use dixie cups but they are too tall and light and will knock over easily and contaminate your bench. Also fasten your disposable/degradeable ESD mat piece to something heavy so you can pick it up and it wont sag and touch the other one. Same for the silicone glue mat if you use it.
Another "protector" that I made is I got a fire brick, scrubbed, washed and sanded one surface nice and smoother to get rid of any crap, then baked it then coated 5 sides with a healthy dose of liquid rubber, then put rubber feet on the bottom. This way I have a ceramic surface if I want to heat something with a gas torch. I used to just use a bathroom tile but it cracked on me. Also good for getting parts real hot on top of or destructively testing smaller parts.. (don't do explosive tantalums inside your lab though, I mean like burning a resistor with a watt). I might make an adapter for it of some kind that can have some kind of alligator clip arms or something on it that interface well with it for high temperature fastening. A good idea might be 'constant force tape'. Get the dense fire brick for this job, since you won't be applying alot of heat, not the really crumbly one that will dirty your lab (called concrete fire brick, can get at lowes, This would make a good fastener for high temps
https://www.kern-liebers.com/en/product-groups/strip-springs/constant-force-springs/ It comes like electrical tape you can cut carefully.. be sure to debur so you don;'t cut yourself with it later ;p
This all applies to commercial use too. You can actually give the rubber ones a fair beating but the plastic ones are pretty weak and you don't wanna do things like disassemble jagged equipment on them. I noticed they have to get replaced fairly often at work for some people for cosmetic reasons and mechanical damage, this can mostly be avoided to the benefit of everyone.
You can also leave your soldering iron on the regular ones for a bit and they won't be hurt but you get the burning flux migrating to the rubber and messing it up if you don't clean it quick.
Biggest offender I had was this flux bottle (1oz) , that was like a printer refill kit nozzle (non sharp high gauge needle), when you finished using it and tacky flux got stuck in the shaft the pressure from the alcohol over temp would cause the bottle to push out whatever was in the nozzle, then it would drip to the bottom of the bottle, and then I would place the bottle on the ESD mat and it would dirty it. Solution would be to keep your flux on a little tray like a olive oil bottle holder in the kitchen, with a small tray structure to contain drippings, and to make it a habit to never place it anywhere but the tray /holder it belongs in
also wear gloves for thermal paste its a complete bitch and will get all over the place. i think its worse then glue because you don't notice that you are contaminated unlike with tacky glue. get some on your wrist and its gonna be a complete bitch. always another tray for thermal paste contaminated items and silpads. probobly better you seal all the paste contaminated items in cheap zip locks before disposal.. ugh I had this stuff get into my wooden floor before.
good hygine comes into play here. If you disassemble something and you know for sure your gonna need to reapply thermal paste the first opportunity you get you should clean it off before you reach into something, start wrangling with some heat sink enclosure fit problem (yea fuck you meanwell, need the jaws of life to get the PCB of of your chassis!!!) or other funny business thats get you dirty. thats when always having cleaning supplies on hands comes in.. besides its bad practice to reuse old thermal paste so clean it immediately!
The problems start when you are really into experimenting and you get some jim-williams sized pile of shit on your bench on top of equipment probes and other stuff.
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