Looking for Soldering Mat - Page 1
Forum section: electronics / beginners

author: Electro Fan
author_rank: Super Contributor
timestamp: October 08, 2020, 08:03:49 pm
content: Anyone know a good model / source for a bench mat that would be good for soldering (silicone?), good for dealing with ESD?, have ruled lines, in green or blue?Thx

author: radiolistener
author_rank: Super Contributor
timestamp: October 08, 2020, 09:30:51 pm
content: I bought Cinese blue silicone S130, works good. Tested it to replace LNA chips and soldering some PCB.The only issue that I found is that it is sensitive for sharp elements

author: janoc
author_rank: Super Contributor
timestamp: October 08, 2020, 10:04:03 pm
content: Just keep in mind that those silicone mats are not ESD safe (they are not conductive/static dissipative).You could also get a proper ESD mat - costs more but worth it.

author: helius
author_rank: Super Contributor
timestamp: October 08, 2020, 11:28:18 pm
content: Try searching for "2-layer ESD mat", those are the best ones. The top (blue or green) layer is dissipative and the black rubber back layer is conductive.There are also "3-layer ESD mats", which are made from a vinyl-mylar sandwich. Those are not as nice but are cheaper.

author: Electro Fan
author_rank: Super Contributor
timestamp: October 09, 2020, 12:18:33 am
content: Quote from: helius on October 08, 2020, 11:28:18 pmThanks. Found this:https://transforming-technologies.com/esd-fyi/how-to-choose-an-esd-mat/Now just need to find some such products. Always helps to know what I'm looking forEdit:How about this?https://www.amazon.com/dp/B074PWQ9P6/ref=sspa_dk_detail_1?psc=1&pd_rd_i=B074PWQ9P6&pd_rd_w=v9Csc&pf_rd_p=7d37a48b-2b1a-4373-8c1a-bdcc5da66be9&pd_rd_wg=bWfOQ&pf_rd_r=DM6TH983GZ17M05508DV&pd_rd_r=9e4ecef4-4290-47f6-9c3b-6e73cb23a05d&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUFBR1ZBSU5WWjNGSEMmZW5jcnlwdGVkSWQ9QTA1OTgwNjQyM0U1WVNKQjhFWDEyJmVuY3J5cHRlZEFkSWQ9QTA0Njk1MjQzSVFYSEM4SkE5REZYJndpZGdldE5hbWU9c3BfZGV0YWlsJmFjdGlvbj1jbGlja1JlZGlyZWN0JmRvTm90TG9nQ2xpY2s9dHJ1ZQ==Seems to meet the specs (except for the desired ruler lines but maybe I can relax the spec on that).

author: Electro Fan
author_rank: Super Contributor
timestamp: October 10, 2020, 06:08:23 pm
content: Something very nice about the ruler markings on a mat....Anyone know if this might be ESD and/or solder worthy (heat/burn resistant)?

author: janoc
author_rank: Super Contributor
timestamp: October 10, 2020, 09:48:55 pm
content: That's a common cutting mat.https://monroe-systems.com/vantage-12-x-18-self-healing-cutting-mat-blue/Not ESD safe and not heat safe neither.

author: Ctrlocti
author_rank: Regular Contributor
timestamp: October 10, 2020, 10:12:07 pm
content: Quote from: helius on October 08, 2020, 11:28:18 pmhey I didn't know those 2layer esd mats were also heat resistant. I have a cheapy chinese silicone one on top of a 2layer esd mat for soldering work

author: Electro Fan
author_rank: Super Contributor
timestamp: October 11, 2020, 07:14:51 pm
content: Need some help with the Theory of Operations for an ESD mat.Got thisESD mat.Also got thisoutlet ground banana jack(to avoid having to attach the wire to the cover plate screw).I measured the resistance from one end of the attachment cords to the other (for both the grounding cord and the wrist strap) and each measured about 973k ohms. From snap to snap across/through the mat I measured about 60k ohms (it seemed to start at about 70k ohms and dropped down to about 50k ohms).According to the instructions for the mat the wrist strap should connect to with an alligator clip to a DUT sitting on the mat, and the other grounding cord should attach from a snap on on the mat to the an alligator clip on the DUT.With the banana plug adapter (to avoid using a the screw that holds an AC outlet cover plate) the instructions indicate a ground wire should run from (a snap on) the mat to the adapter (which just makes it convenient to plug in a banana plug rather than wrapping a bare wire around the small screw that holds an AC outlet cover in place). This grounding cord goes from the mat snap on one end to an alligator clip on the other; the alligator clip nicely pulls off to leave a banana plug ready to plug into the adapter. The adapter has a metal prong that goes into the ground hole in a three receptacle AC outlet with plastic pieces shaped like the prongs of an AC plug to hold the adapter firmly in place. The adapter is not necessary but convenient.So, the questions are:1. Which of the two instructions (for the mat and banana plug adapter) make more sense, or is there a combination that would be best?- Maybe the answer is to ground one mat snap to the AC outlet ground and attach the other snap to the wrist strap, and then just set a DUT on the ESD mat? Or should I find a way to attach three cords to the two mat snaps? (one from the wrist strap, one from the DUT, and one from the AC outlet ground?)2. What is inside the two cords that produces the 973k ohms? (A resistor or capacitor?)3. Given all of the above and whatever is the best combination of connections, what is the Theory of Operation?FWIW, the mat size looks like it will fit on the soldering/work bench nicely and provide good working space, it's a very pretty green (kind of subjective), and the top surface will supposedly be resistant to solder splashes and solder burns (these attributes are yet TBD).Thanks for help with how to best connect things for ESD protection, operator safety (always #1), and for any insights on how these things should work together in theory and practice.PS, Thanks to helius for pointing me toward 2-layer ESD mats

author: MarkF
author_rank: Super Contributor
timestamp: October 11, 2020, 08:15:43 pm
content: I bought the Sierra FT Series mat and it's setup is different.The grounding cable for the mat has 0Ω resistance and the arm strap has 1MΩ resistance.You plug the arm strap into the connector that snaps onto the mat.

author: Electro Fan
author_rank: Super Contributor
timestamp: October 12, 2020, 03:53:39 pm
content: bump- still looking to see if anyone can post an explanation of the Theory of Operation for ESD mats, or any good links on the subjectThanks

author: helius
author_rank: Super Contributor
timestamp: October 12, 2020, 05:21:26 pm
content: I have read a theory page before, but can't find it right now.The general idea is that ESD safety is about minimizing currents from static discharges. ESD events involve high instantaneous currents and this is what damages electronics. The two physical models used to measure ESD safety are the Human Body Model (HBM) and the Charged Device Model (CDM). The scenarios are roughly that of a charged human operator touching a workpiece for HBM, and of a charged workpiece touching a ground plane for CDM. The ESD workstation must protect from both types of events.To protect from CDM, we would like to prevent the workpiece from becoming charged, so we would like some type of path to ground to be constantly maintained. The conductive back layer of the ESD mat distributes this ground path. However, to minimize ESD currents we don't want to ever touch the work with a low impedance to ground. The dissipative top layer provides a safe impedance.Protection from HBM mainly involves the operator wearing ground straps around the wrist or the feet. It's best if the wrist strap and ESD mat are star grounded at the same point because that is the safest in case of a faulty connection. You can also use an ESD monitor device to alarm on faults.I'll add that in my experience, banana plugs do not fit securely in AC outlets; they are not designed for this. I would attach instead to the grounding point on the back of your soldering station.

author: Electro Fan
author_rank: Super Contributor
timestamp: October 12, 2020, 07:34:20 pm
content: Quote from: helius on October 12, 2020, 05:21:26 pmWow, nice summary helius! Thanks - that's very much what I was looking for - it's a very nice Theory overview!A few more questions, plz/Thx:So, two snaps a couple feet apart from one another aren't as good as one snap point as the center of a star topology? (How much/what are we giving up with distributed snaps vs a central star snap connection point?)Also, does the nature of the mat enable a DUT to be protected (if the DUT circuitry has a path from the PCB through the chassis of the DUT) to the mat? Or does the DUT need an alligator clip type connection to a chord to a snap on the mat?- if the answer is it needs a chord even if a conductive contact is made from the DUT to the mat (directly without the chord), does that mean I need 3 chords: 1 from wrist to a central star snap, 1 from the DUT to the central star snap, and 1 from the central star snap to the ground connection on the AC outlet?"However, to minimize ESD currents we don't want to ever touch the work with a low impedance to ground."Is this why the chords have the ~973k ohm values? (Is there a resistor or a capacitor in the chord assemblies?) Is ~1 Mohm a suitable value?Thanks

author: helius
author_rank: Super Contributor
timestamp: October 12, 2020, 07:48:20 pm
content: The mat itself is sufficient if the PCB sits directly in contact with the mat. Most chassis (for an assembled DUT) have passivation on the outside of the metal, or plastic feet, and the ground clip is a good idea.The wrist strap should have ~1 megaohm in series, both to minimize current and also to protect the operator in case of contact with live circuits. As you can imagine, bonding a hard ground to your body makes accidental contact with a live terminal more deadly. This resistor is sometimes under the button and sometimes inside the cable, you need to be aware of which it is.The ESD mat already provides a high enough impedance that a 1M resistor is not needed in its connecting cable. It won't hurt, however. 2M ohm is low enough to keep static charge from accumulating.

author: Electro Fan
author_rank: Super Contributor
timestamp: October 12, 2020, 08:01:21 pm
content: Thanks again helius."As you can imagine, bonding a hard ground to your body makes accidental contact with a live terminal more deadly."I'm thinking that the certainty of the path to ground using the adapter to the AC outlet (or even to an AC outlet cover plate screw) might present more downside than upside; maybe it would be better to find some other sure path (water pipe, etc?) to ground that has no possibility of an AC outlet wiring glitch?"This resistor is sometimes under the button and sometimes inside the cable, you need to be aware of which it is".- by button do you mean a snap on the mat, a snap on the cable, or something else? (My cables from end to end measure 973k ohms, per cable without any connection to the mat).

author: helius
author_rank: Super Contributor
timestamp: October 12, 2020, 09:32:32 pm
content: An AC wiring glitch should* trip the breaker or blow the fuse protecting the branch circuit, and the 1M series resistor protects you from shock in any case.The button is part of the wrist strap. If the 1M resistor isn't in the cable, it must be in the plastic box that connects the silver threads to the button.*there are possible scenarios where the breaker wouldn't activate, but electrical wiring practices minimize those. For example, if both the PE and live wires inside a panel box become disconnected, it's possible for only the live to touch the metal box. This is why the PE always needs more slack than the current carrying wires. An ESD monitor would also alert you to the ground circuit fault.

author: Electro Fan
author_rank: Super Contributor
timestamp: October 12, 2020, 10:13:49 pm
content: Quote from: helius on October 12, 2020, 09:32:32 pmOk, a little off topic but please say more about the extra slack for the PE wire vs. the current carrying wires... (why is the extra slack in the panel box likely to provide added protection)?Back on topic, if for some reason the mat is not connected to a PE ground in some form or fashion is the remaining combination of the mat with the wires to the wrist and the DUT likely to provide sufficient ESD protection, but less protection than if the mat is grounded to PE? Or is the whole thing a bust without a connection from the ESD mat to PE?

author: helius
author_rank: Super Contributor
timestamp: October 13, 2020, 02:10:24 am
content: It's for protection in case the cable gets pulled and the wires come loose from their contacts. The PE is bonded to all metal parts like panel boxes or outlets. It has extra slack so that it will stay put if the other wires get pulled out and exposed. This protects the users from shock and provides a fault path so the fuse/breaker can shut off that branch circuit. A similar reason is why the PE wire in a plug should have more slack: if the cable gets pulled out of the plug, you want it to be the last contact to be broken. You need to be mindful of this when wiring your own plugs (which few do today, but it was common in the past, especially in the UK).Without any connection to ground, the ability of the ESD wrist strap to bleed off static charge is limited. One thing you will see in older computer manuals is a direction to clip the ESD strap onto the metal chassis of the DUT. The reasoning is that as you bring your arm inside the case, you have entered a kind of Faraday cage where charges will be sucked out of your body and into the chassis (as the charge inside a metal shell always goes towards zero). It's better than nothing. The same effect can't really apply to an ESD mat as it does not surround your hands, but I guess you would bring the mat and body to the same voltage. You would still not be able to safely use grounded tools like soldering irons.

author: Electro Fan
author_rank: Super Contributor
timestamp: October 13, 2020, 06:39:58 am
content: Quote from: helius on October 13, 2020, 02:10:24 amUnderstand. Thanks!QuoteI think I got most of that but not sure that I understood this:“You would still not be able to safely use grounded tools like soldering irons.“Please say more on this. Is this comment a reference to part safety or operator safety (or both)? And is this comment in reference to my question about using the ESD matwithoutthe wired connection to PE (or is the added risk with a soldering iron intended to meanwiththe mat wired to PE)?The last thing I want to do is add an ESD mat to the bench and decrease operator safety. I’ve gone decades (forever) with zero static glitches, so I’d hate to create a real safety hazard by pushing for better part protection if it comes with more operator risk. I’d rather not be a poster for perfection is the enemy of good enoughThx again.

author: tooki
author_rank: Super Contributor
timestamp: October 13, 2020, 02:41:38 pm
content: Quote from: Electro Fan on October 13, 2020, 06:39:58 amI think he's referring to ESD safety, i.e. part safety, in that the point of a grounded ESD mat is to reduce to zero the potential difference (voltage) between the part and ground. A mat which isn't connected to ground (floating) has no way to equalize the potential. What I think helius meant is that while the mat may succeed in bringing your hands to the same potential as the part (because of incidental contact with it, or via a wrist strap), once you bring in your iron, which is at ground potential and not mat-and-electrofan potential, there's the risk that current will flow through the part, i.e. an ESD event.The resistor(s) in ESD grounding serve to limit current, so that a) charges dissipate slowly rather than as energetic bursts, reducing risk of component damage, and b) to protect the operator, since the operator isn't floating any more. For example, if you were not grounded in any way (no ESD, on an insulating floor and insulated work area), and you accidentally touched a 230V live wire, nothing would happen to because there's no circuit. Conversely, suppose you were connected to groundwithoutan inline resistor, and then you touched the 230V live wire: you'd get a shock as the 230V flowed through your body from live to ground. Putting the 1+ megohms of resistance in series means no more than 230µA of current would flow, far too little to perceive, and far too little to harm you.In essence, the resistor allows your ESD workspace to be ade-factoinsulator from an operator safety standpoint, while being a conductor from an electrostatic charge standpoint.Quote from: Electro Fan on October 13, 2020, 06:39:58 am…that you know of.The insidious thing about ESD damage is that it's often subtle, leaving the component working, but weakened, such that it might misbehave in a subtle way, or simply fail sooner than it would have without ESD damage. (But long enough in the future that you don't make the connection with the ESD event, if you even had a way to detect the ESD event when it happened.)So between the damage often being invisible, and the fact that ESD events nearly always go completely undetected since they're practically always invisible, theonlyway to deal with ESD is comprehensive prevention.Helius, if I've gotten any of this wrong, please correct me ruthlessly!

author: Electro Fan
author_rank: Super Contributor
timestamp: October 13, 2020, 08:11:02 pm
content: Quote from: tooki on October 13, 2020, 02:41:38 pmOk, roger on the"that I know of"part. I almost added that to my prior post so I do get it - it's that I know of, and some/many times it might be hard to know that an ESD event occurred to a part. Thanks for this reminder/clarification/confirmation.On the human safety factor, this has become my primary/remaining focus for this discussion.If I understand correctly the mat will offer some level of human safety with just the wrist strap given the resistor inside of the wrist strap (~973k ohms), and I think to a lesser extent but to some extent given the pad itself (~50k-70k ohms), but the safer/safest approach would be to also have the mat properly grounded to PE - correct?If the above paragraph is correct, then the only question is in return for the added safety of grounding the mat to PE, what is the tradeoff in possibly being exposed to some Murphy event when the wrist strap is connected (through the mat) to the PE in the form of a screw on the cover of an AC outlet? Seems unlikely to be a problem but that's usually where Murphy visits.What's your thinking on the wisdom of grounding the mat to an AC outlet cover screw, or the banana plug adapter?I'm guessing the answer is that if the AC outlet is in proper order, it's close to zero risk - but grounding the mat to some PE that has no direct connection or very near proximity to AC circuity (such as a water pipe or a dedicated ground rod, etc) would be preferred. If that happens to be the answer, then the only question left is does it matter to any material degree if the distance from the mat to the chosen PE is on the order of several to a dozen meters? My guess is that several to a dozen meters of say 18 gauge wire is not material, but I thought I'd ask as long as we're running this to discussion to ground (ha ha).Thx again for all the educational support with this.

author: tooki
author_rank: Super Contributor
timestamp: October 13, 2020, 10:35:13 pm
content: Your mat needs to have an resistor to ground only if its own resistance is not high enough. Mine measures about 1.7M from the underside to ground, and too high for my multimeter to measure between the top side and ground, so it’s safe as-is. Measure yours not snap to snap, but snap to the other end of the ground wire it came with.If the mat is properly grounded via a resistor, you can connect your wrist strap to the mat, or directly to a ground since the wrist strap has its own resistor. I don’t understand the question you are trying to ask in the “Murphy’s law” paragraph.DO NOT use anything but the ground pin/screw of a properly functioning, properly grounded electrical socket as your PE contact, be it a direct connection or via the ground potential bonding jack of a piece of equipment (like many soldering stations). Using a pipe or radiator is an unreliable ground (especially nowadays with so much plastic pipe), but above all, if it isn’t a good ground and something goes horribly wrong in your lab, you run the risk of electrifying all the plumbing in the building, exposing others to risk of electrocution!You wouldn’t want your PE connection to be far from your equipment grounds — if they are, there’s the potential for a potential difference to develop, negating the entire effort. I, for example, have mind bonded to the grounded case of a power supply. It all ends up going into one power strip under the desk, so all the grounds are at the same potential, just as we want it.

author: Shock
author_rank: Super Contributor
timestamp: October 14, 2020, 07:46:26 am
content: The reply in the link below provides some good information including standards. If you are concerned about safety connecting the mat to the grounded/earthed household mains the best idea is get it checked. But essentially it would be no riskier than touching the BNC connector on your oscilloscope while plugged into the wall. I'd be using a current limiting resistor as mentioned in the reply and an rcd protected outlet. Obviously you do not tether your wrist while working on energized and live circuits where you can be easily exposed to dangerous voltages.https://esdsystems.descoindustries.com/QuestionsAndAnswers/ShowQuestion.aspx?i=1306