DIY Anti Static Mat

Intro: DIY Anti Static Mat

An inexpensive solution to a reasonably expensive, albeit necessary, electronic soldering accessory.


This is my first Instructable! Please give advice, constructive criticism, AND PRAISE! (I can't believe I forgot to list the last one. Jeez!!! :)


[EDIT: As one commenter suggested, (and I failed to realize) your mat should have a conductive top layer and a non-conductive bottom layer, NOT the three layer /resistive-conductive-resistive/ version I have made here. I haven't yet found a proper substitute for the aluminum (it is not durable enough to use as a top layer). I will edit this -Ible to reflect the correct 'two-layer' assembly once I have the proper material for an acceptable price! (Free.... Obviously...) Thanks for reading on!]

STEP 1: Explanations

All Anti Static mats, aka ESD mats, have one purpose - to dissipate the static charge that can, and usually does, build up on the human body during a typical day in a controlled manner. This condition can cause a short in your components from a rapid discharge of electrostatic energy. Really creative name for the mat, huh?

To be more accurate, an Anti Static mat drastically slows the rate of static energy discharge or maintain at zero, the difference in the common electrical potential of the operator relative to the many components he, or she, may come in contact with. This eliminates the possibility of discharging the static into a sensitive electronic component possibly causing it irreparably damage.

The mats are typically constructed of an electrically resistive rubber or plastic derived material combined with a conductive layer that leads to a ground plane such as a three pronged outlet (here in the US) or a grounding rod in the ground outside of your hobby shop. See the two images above for an example.
Some mats implement a direct connection with the operator through a wrist strap or floor mat. The bench top mat that I am constructing will use a wrist strap to provide a complete circuit from the skin, through the mat, and into the chosen grounding plane. As I understand things, this setup can provide a more stable and consistent rate of discharge over a day's work period.
ESD mats will usually have at the least a 1 mega ohm resistor inline with the circuit somewhere to slow the rate of ElectroStatic Discharge and prevent shock from the grounding plane reaching the operator.

STEP 2: Our Ultimate Goal

Our ultimate goal is simply a mat that provides a resistive surface that will still provide a complete line to the grounded prong in my bench power outlet. Hopefully we will produce something that will accomplish this without allowing voltage to reach the operator from the outlet and still discharge the static buildup. Having about ten feet of yoga mat on hand and a roll of foil made the layout and construction easy. Just fold and cut, match and cut, assemble various components, and glue like crazy! See? Easy... 

Above is a quickly assembled prototype of what we are after. I omitted the glue on half of this replica to be able to clearly show the different parts, construction order, and finished product.

STEP 3: Tools!!!

Tools (pictured):

  1. Hobby knife
  2. Wire strippers/Cutters
  3. Multimeter
  4. Straight Edge or Metal Ruler
  5. Hammer
  6. 7/16 long socket (for my build at least)
  7. 3/16 drill bit or punch
  8. Awl or hole punch
(not pictured)
  9. Soldering Iron
10. Heat gun or lighter
11. solder
12. heat shrink tubing

Note: The socket and drill bit are for the snap insert. I snap tool would be MUCH better.

STEP 4: Materials

Material:
1. One electrically resistive layer. (The old yoga mat)
2. One electrically conductive layer. (The aluminum foil)
3. ALOT of glue or other adhesive. When it is dry, it should adhere the parts well and still be very flexible. ( I grabbed something out of an old work cabinet I found from previous tenants I guess. It wasn't nearly enough.)
4. One length of wire approximately a foot longer than the distance from the location you will be using your mat to your chosen outlet. Choose the smallest wire that is bigger that 22 gauge but not larger than 10 gauge and is multi stranded. Remember that the smaller diameter of wire will provide the largest gain in resistance. It may also provide feedback in the form of heat. But I HIGHLY doubt it. (Actually doing the math on this one might help you pinpoint the exact wire gauge if you are worried. I guessed.)
5. One anti-static wrist strap (you can purchase one of these online or opt for the cheaper, disposable versions at your local hardware box store. Just make sure it has a one (1) mega-ohm resistor)
6. One clothing snap and mate assembly OR a steel nut and screw/bolt. (make sure that whatever you choose has conductive properties)
7. One male end of old extension cord

STEP 5: Prep

Step 1
Cut your resistive material into two equal parts and matching shape.

Step 2
cut your conductive material to match your resistive material. Be sure to cut a small piece of the foil about 2" x 4" (See the second picture). This will be used for reinforcement at the snap location. Just set it aside for now.

Note:
Overlap is okay in either material. We're going to trim everything to size later. Just be sure to save as much material of each layer as possible so that your ESD mat can be as large as possible. Or layer your foil for bigger mats. (the primary picture as an example)


Step 3
Remove the plastic sheath from a short length of your grounding wire, say about 1" (inch) and spread out the strands into a fan. (See the third picture)

Step 4
Thoroughly clean the resistive material on both sides of both parts. 

Step 5
Bond your male plug to your grounding wire with a crimp fastener or solder. Be sure to remove any part of the positive and negative wires that are or could be exposed to you, the air, or metal. If your chosen plug can be disassembled. Be certain to take advantage of this and remove any wire connected to the +/- prongs only connecting the wire from your ESD mat to the ground/neutral prong.

Step 6
Locate the placement of your snap or bolt. Make a hole in the top resistive layer and conductive layer. Include the small piece of foil we cut earlier. Fold the small piece of foil over and under your conductive layer where you are making your hole. DO NOT MAKE A HOLE IN YOUR BOTTOM RESISTIVE LAYER.

STEP 6: Construction

With proper preparation. This becomes the easy part.

For parts reference:

Identifier / Name
   A / Bottom resistive layer
   B1 / Conductive layer
   B2 / reinforcement layer of conductive material
   C / Upper resistive layer
   D / Grounding wire prong assembly
   E1 / Male Snap assembly base
   E2 / Male Snap assembly top

This reference chart may be overkill but it also represents the construction order. Let me know!

Construction Order

Step 1
Lay part C on your clean work surface upside down. The side to be glued should be facing up.

Step 2
Flood the surface of part C with the adhesive. Using a paint brush or squeegee spread the adhesive to the edges evening it out as you spread it. Be sure to follow the instructions on the bottle for proper adhesion.

Step 3
With part B2 still correctly located on part B1, carefully lay your conductive layer on part C. Check that your pre-made holes line up and allow the adhesive to dry enough to handle.

Step 4
Once the adhesive has had time to cure, place the fan side of your ground wire on or in your pre-made hole. Place part E1 in the hole and use it to hold the grounding wire in place. Flip the partial assembly over and place part E2 over the stud of part E1.

Step 5
Take a moment and make an Ohm check from your conductive layer to the ground prong in your plug. If you get a positive reading: install the snap making sure there is a strong connection between the wire and your snap assembly.
If not: time to trouble shoot... booooo.

Step 6
Lay part A on your clean work surface with the side to be glued facing up.

Step 7
Flood part A with adhesive, repeating the actions of Step 2.

Step 8
Carefully place your assembled upper layers onto part A and press out the air bubbles. Make an Ohm check to be certain the circuit is intact.

Step 9
If all is well, place weight onto the assembly, evenly applying pressure across the entire part. Allow the glue to cure completely.

Step 10
Use your straight edge to measure and cut the assembly to the sized mat you want.

Step 11
Attach your wrist strap. Make another Ohm check from the ground prong to your strap. Assuming everything checks out. Record the R measurement and place somewhere for safe keeping. We want to be able to accurately test the performance of our mats over time for safety.

Step 12
Place the mat on your work station and plug in your ground cord. THAT'S IT! YOUR DONE! 

STEP 7: Conclusion

Well, like I just said, we're ALL DONE! Do one more Ohm check to make sure you are getting the kind of resistance you were looking for. Obviously the more resistance the better. 

I hope this is helpful. Again, please leave a comment! Tips, tricks, how your's went, anything you need to know from me, and any advice on how to write a better instructable!

-Maker T Elam

Comments

[JodyF1]

For ESD mats in general, why should the top layer be insulating? I don't get it. If it insulates, then surely there's no point in the conductive layer? With such two layers, nothing can reach the bottom (conductive) layer through the top (insulating) layer?

[RonaldJ33]

Hi, so good question. I have an answer for you. First Remember the fact that by their nature Electrostatic Discharges are always High Voltage Discharges. Amperage is typically negligible but can be as high as 35,000 Volts! ESD mats have to do two things: they must absorb those high voltage, low amperage burst of energy. 2) they must dissipate that energy in a controlled way ( ie, resist rapid current flow). For this ESD Mats are made of PVC Plastic and Polyurethane. It seems counter intuitive because we think of plastic an rubber as insulators. they are, but only relative to metals. Also, when dealing with high voltage, insulation must be much thicker to be effective. The ESD mats are typically very thin; 0.03 inches thick more or less. So long story short we should try a much thinner "insulator" to conduct the high voltage and resist the rapid current flow all at once. Thanks Jody for this great question (it made me think). and Thanks Matt for this DIY experiment, don't give up, you're onto something! check out the dimensional specs and materials used for the ESD mat in this link, maybe compare to others and think about what I said. Good Luck folks.

http://www.microcenter.com/product/209946/ESD_Stat...

[PeterR153]

how about glass as a ESD safe surface? i do have a wooden esd setup similar to yours but im looking for larger. Will glass work or does that still conduct heavily.

[ecode]

Turns out that dissipative mats are non-conductive. I was going to delete my comment but couldn't find it until now.

Glass is not a good choice because while it's usually non-conductive, it can be given a charge.

I'm going to switch to using dissipative a mat(s).

[ekarges3rd]

I am a PC Onsite Technician and even though they can't see me when I am working, Dell, HP and Lenovo expect me to use an Anti-Static Mat and Wrist Strap when I am servicing computers. If something would happen and I wasn't using one, I could be liable for any unsuccessful repairs. I purchased one at Radio Shack for about $30 with the wrist strap, but you can find them for about half of that nowadays, and I don't consider that too much to spend to have peace of mind knowing that your equipment is safe. This seems like a good project, but quite a bit of work.

[modifyman]

I suppose if you want to go the ultimate poor mans way, even if your not poor but just frugal, go barefoot. You know your grounded better than your panel when standing on concrete in bare feet and touch the metal casing of an aging electrical device with your elbow and feel that slight bite.

[modifyman]

Put on cotton socks if you want some resistance. Not wool or nylon

[Thadw]

Get a humidifier, it's an anti static mat for everything, lol. That's all I use. Great project though, and your conductive layer should be on the bottom not the top. It's job is to provide ground potential base for your insulating layer, which is not a perfect insulator as nitrile rubber is 625M ohms per 1/4" length (better conductor than wood). you don't want a highly conductive top layer to short out your work on. And an esd mat does nothing if you don't ground yourself first, or just get a Humidifier if it's at home or a small lab. Cheers

[stinkyoldguy]

I do much the same as keanja and have not had any problems. I have a "huge" anti static bag I scrounged from a server motherboard that I use as an assembly surface (on top of Formica bench top) and a couple of smaller bags that I can use for protected storage.

And if you need to use a wrist strap is easiest to clip it to the computer chassis you are working on.

[Robert4211]

I found your instruct-able while searching for anti-static foam to line a drawer for hard drive storage. I now know what to do with those 1 meg ohm resistors too. Now I just need a 16 foot long piece of foam to cover my workbench :). Thanks for all the info!
Best, Rob

[keanja]

I have been working on electronics for 30 + years and I have never used pads. I have always observed some common sense rules. 1. Have a truly grounded outlet (not something someone has hacked to have 3 prong outlets with 2 wire systems with no ground wire as most computers have 3 prong connectors). 2. plug the computer into the outlet when servicing with the computer OFF. 3. Touch yourself to the metal chasis as you work, often. 3. Before opening a computer touch the metal near where the plug plugs into the computer. 4. If working on a notebook computer have a old desktop to do the above with. 5. Use the anti-static plastics bags that components come to set them on when you need to put them down. 6. Always handle components by the edges.

[Lectric Wizard]

This is a good idea, but your top layer should be conductive with some resistance such as the black foam that components are shipped in. You don't want " the more resistance the better", you want to disipate the static to ground as quickly as possible & yet not cause a short circuit or shock hazard , should the circuit be powered up while touching the pad.I have used the pads that are sold for use under computer keyboards, they are a small anit-static pad & usually much cheaper that the regular ones. Cheers!

[Maker T Elam]

I haven't seen ESD pads for your keyboard. I'll look around!!!! Thanks!

[Maker T Elam]

I see c181155. I should change the top layer. I figured the connection from me, through the wrist strap, and into the aluminum/copper wire, and into the ground plug was enough of a conduit.
Speaking of which, does anyone know of a forumla that will give you a general target to shoot for as far as resistance. Everywhere I read up on the subject, I read numbers in 1*10 to the 6th and 7th power Ohms. But I had no idea why.

[david339]

Why is threre a need of a conductive top layer?

[Maker T Elam]

The conductive layer completes the circuit between you, the device, and the ground plane (if you aren'e wearing a grounded and conductive wrist strap). My understanding is that your body builds up the charge. Then you grab the VERY sensitive electronic part without a conductive mat (that slows the rate of discharge to ground) sending the spark to your part but it has no where else to go. ZAP! Or... I could really have misunderstood everything I read.
Honestly, what ever you do when working with electricity. DON'T, I REPEAT DON'T, let the smoke out or everything stops working. Its horrible. Just horrible...

[mdog93]

"Material:
1. One electrically resistive layer. (The old yoga mat)
2. One electrically resistive layer. (The aluminum foil)"

Did you not mean '2. One electrically conductive layer. (The aluminium foil)'

[Maker T Elam]

AH! Right you are! Thank you! Will edit that tonight!

[Lectric Wizard]

The top must allow the static electricity to drain away to ground,the insulator would prevent this. The overall resistance is chosen in the million ohm range because static can carry thousands of volts. That lets the higher voltage drain but maintains current at lower voltages to a safe level. As pfred2says it not that big of a problem most of the time but when you are handling chips worth hundreds or thousands of dollars each it is a good idea !

[pfred2]

I'd rather take my chances with static than shorting out. I don't have issues with static discharge damaging modern electronic components today. Fabrication processes and designs have improved considerably from the bad old days when you just looked at a CMOS IC wrong and it blew out.

Wearing wrist straps drives me nuts too. So thanks, but no thanks.

One board fabrication house I worked at we used plain white foam to stuff PCBs on because the boss hated using anti static foam, "it costs too much". The white foam beads would cling to stuff it was so charged up, no problem!

Static damage to electronics is mostly hysteria as far as I'm concerned. But hey whatever makes you feel better.