Does your silicone soldering mat bulge up when heated? - Page 1
Forum section: electronics / general

author: Microdoser
author_rank: Frequent Contributor
timestamp: October 03, 2023, 05:00:38 pm
content: Mine does, and it really doesn't help when dealing with small parts under the scope, everything gets out of focus interrupting work. The blurb when I bought it said 500C, soldering, hot air, blah blah blah, but that was plainly just rubbish. It goes flat again when cool, but that isn't the point.If yours doesn't bulge or warp, what brand/type do you use and do you have a link for it? I think it's time I got a different one.

author: ataradov
author_rank: Super Contributor
timestamp: October 03, 2023, 05:07:22 pm
content: All the ones I tried do bulge. This is why I don't like to use them.The physical thickness might be the key, but they don't make thick mats. I've seen thick sheets of silicone, which might work better, but I have not tried.I also don't see the point of those mats because they still get as hot as any other surface would and transfer the heat to the bench. So, I use a metal plate on small rubber feet. It isolates the bench from the significant heat. It does get hot itself, but then it also cools down pretty fast. I cover the surface of the plate with capton tape. I don't know if it helps with the heat, I mostly do it to prevent the glare from the shiny metal surface.

author: Microdoser
author_rank: Frequent Contributor
timestamp: October 03, 2023, 05:08:17 pm
content: Quote from: ataradov on October 03, 2023, 05:07:22 pmDamn, I was hoping it was my terrible choice rather than a general issue.

author: Veteran68
author_rank: Frequent Contributor
timestamp: October 03, 2023, 05:46:12 pm
content: I have not noticed this with mine. I have an ESD mat covering the bench with a silicone mat on top of that for soldering. I typically don't apply heat directly to the mat though. Maybe some when I'm using the hot air station, but again I've not noticed any bubbling.(and as soon as I say that, I jynx myself and will have a baseball sized bubble the next time I solder something...)

author: ataradov
author_rank: Super Contributor
timestamp: October 03, 2023, 05:54:19 pm
content: It only happens with hot air, of course. The silicone has thermal expansion, so it increases in volume, and that volume must go somewhere, so it bulges. If you don't heat it enough or it dissipates fast enough, there would not be an issue.And it is usually not an issue when working on large boards in the middle of the board. But once you have a small board and some of the hot air has to heat the mat, it becomes an issue.

author: Veteran68
author_rank: Frequent Contributor
timestamp: October 03, 2023, 06:02:16 pm
content: Make sense. The funny thing is I work on more small boards than large boards and haven't noticed it, but I tend to use smaller nozzles and higher heat to get it done quickly vs slow roasting a board. I guess I've just been lucky so far. It also just occurs to me that I have a hot plate for when I need to really put heat into a troublesome board, so wouldn't be soldering directly on top of the mat in that case.

author: Microdoser
author_rank: Frequent Contributor
timestamp: October 03, 2023, 07:26:42 pm
content: OK, so it looks like I'll have to find some alternative material.Any suggestions? I saw someone in another thread was using a large tile to solder on. Sounds like it would work quite well, and be much cheaper than most other possibilities.

author: ataradov
author_rank: Super Contributor
timestamp: October 03, 2023, 08:21:19 pm
content: Ceramic/granite tiles are a good option. We have them in the lab at work and I have no complaints. They are also easy to clean from flux mess.

author: Microdoser
author_rank: Frequent Contributor
timestamp: October 04, 2023, 12:37:48 pm
content: Quote from: Veteran68 on October 03, 2023, 06:02:16 pmI think my issue is I have a relatively thin mat, and I don't just rework, I place about 30 components onto a 100mmx100mm board, sometimes I swap all those components off another board (doing some PCB design prototyping, so I just use old salvaged chips etc). I'm going to get one of the silicone mats with magnetic component holding sections and then find a tile that fits onto the actual work zone. I reckon the mat will keep the tile stationary quite well. Might even hot glue it down.

author: Veteran68
author_rank: Frequent Contributor
timestamp: October 04, 2023, 02:30:30 pm
content: Quote from: Microdoser on October 04, 2023, 12:37:48 pmThen if you're soldering that many SMD components at once I'd look into using at least a hot plate and soldering paste. Or a reflow oven for really big jobs.I have a hot plate that's about 200mm square so is good for smaller boards. Pretty muchthis one.

author: Messtechniker
author_rank: Frequent Contributor
timestamp: October 04, 2023, 02:33:19 pm
content: Mine bulges even without being heated.Go figure.

author: thm_w
author_rank: Super Contributor
timestamp: October 04, 2023, 09:43:45 pm
content: Yes bulges. But not working on enough small boards for it to be a problem right now, all large stuff.Quote from: ataradov on October 03, 2023, 05:07:22 pmIt stops enough heat transfer for me to prevent damage to the ESD mat underneath.Metal plate with airgap or ceramic tile would work better for heat isolation, but, I prefer the grippiness and softness of the silicone.

author: Someone
author_rank: Super Contributor
timestamp: October 04, 2023, 10:05:54 pm
content: Quote from: ataradov on October 03, 2023, 08:21:19 pmChunks of lumber work too, dressed hardwood if you're feeling fancy. Not sure I'd want to locally heat a ceramic unless it was specifically a "refractory"/kiln/oven type (brittle explosion)

author: Microdoser
author_rank: Frequent Contributor
timestamp: October 05, 2023, 02:34:57 am
content: Quote from: Veteran68 on October 04, 2023, 02:30:30 pmI think for now I'll just get a decent tile for under a tenner. Once I'm past updating the PCB regularly and into production, I'll get a stencil made, get some decent paste and a hotplate. A lot of what I do is moving components from previous designs onto the new design and adding the handful of new components.

author: tooki
author_rank: Super Contributor
timestamp: October 07, 2023, 07:20:36 am
content: Regardless of what kind of mat is in use, one tip that can be helpful: if your board has mounting holes, temporarily screw some short spacers onto it to raise it off the mat. That'll reduce the heat transferred out.(Or use a board holder of some kind.)

author: Smokey
author_rank: Super Contributor
timestamp: October 07, 2023, 08:34:57 am
content: Yup. Hot air bulges the mat.Whenever I need to hot air parts under the microscope, I have a piece of wood (3in x 6in x 3/8in) that I have covered with wide kapton tape. I do all my hot air work on top of that. The kapton holds up to the hot air no problem. No more mat abuse.

author: tooki
author_rank: Super Contributor
timestamp: October 08, 2023, 01:02:11 pm
content: For hot air work, I almost always use my holding hands (the octopus-like ones made of CNC lubricant hoses, in my case from the now-defunct Hobby Creek that pioneered this style) to rigidly hold the board in the air so that I can preheat from the underside, too.Preheating the board broadly from the underside vastly reduces the amount of heat you have to apply to the component side of the board.

author: Microdoser
author_rank: Frequent Contributor
timestamp: October 09, 2023, 10:33:23 am
content: We're moving house soon, and in the new place I'll have a lower table, and also more disposable income to spend on toys. The combination of those 2 things means I'll likely get a hot plate, eliminating all of my issues (and maybe creating a couple of new ones, hehe)

author: tooki
author_rank: Super Contributor
timestamp: October 13, 2023, 12:14:48 pm
content: Hotplates become useless the moment you have to work on a board with through-hole components already soldered in, or on boards with components on both sides. (Not to mention the potential for hotspots if your board is not flawlessly flat.) IMHO hot air, infrared, or even oven preheating is a much more sensible choice.

author: Smokey
author_rank: Super Contributor
timestamp: October 13, 2023, 06:54:38 pm
content: Quote from: tooki on October 13, 2023, 12:14:48 pmKnowing you need to use the hotplate to reflow is a good motivation to keep your boards small and your loads one sided, which are both good things to keep the cost down :⁠-⁠)

author: tooki
author_rank: Super Contributor
timestamp: October 14, 2023, 10:15:28 am
content: Sure, for assembling new boards. But if you ever need to rework a board, it becomes a massive limitation. Many connectors don't exist in SMD versions (or even if they do, have plastic retaining clips that poke through), and if you ever need to rework that, you'll be in trouble. And of course, if you need to rework a board you didn't design, you have no control over the design.Upshot is, I don't know why one would choose a hotplate over an IR preheater, for example.

author: Microdoser
author_rank: Frequent Contributor
timestamp: October 14, 2023, 01:35:17 pm
content: Quote from: tooki on October 14, 2023, 10:15:28 amAt some point, I may get a hotplate for assembly of new boards. As you say, it makes no sense for rework although as I tend to reuse a lot of components to make yet another prototype version it would be handy to sit the old board on there for easy removal of many components.

author: tooki
author_rank: Super Contributor
timestamp: October 14, 2023, 01:56:30 pm
content: You can do that with IR, too.

author: temperance
author_rank: Super Contributor
timestamp: October 14, 2023, 02:05:26 pm
content: The bulging is caused by the top and bottom being made of different materials. At least my ESD mat's are made like.

author: Microdoser
author_rank: Frequent Contributor
timestamp: October 14, 2023, 10:25:56 pm
content: Quote from: tooki on October 14, 2023, 01:56:30 pmSure, but at 4x the cost from what I can see with a quick google.

author: tooki
author_rank: Super Contributor
timestamp: October 15, 2023, 10:40:18 am
content: Quote from: temperance on October 14, 2023, 02:05:26 pmNope, it’s not because of being different materials. OP’s mat is silicone, and those are made of only one material.It’s much simpler: the mat material(s) expand when hot. Because the heating is localized, it expandsin that one spot, and since it’s surrounded by cool, unexpanded material, it has to go somewhere. And because the top of the mat is hotter than the bottom, it bulges up, not down.

author: tooki
author_rank: Super Contributor
timestamp: October 15, 2023, 10:43:04 am
content: Quote from: Microdoser on October 14, 2023, 10:25:56 pmTrue, the hot plates are cheap as dirt. But whatever you spend on one of those becomes wasted money when you end up needing an IR or hot air preheater anyway, and end up buying both.I have considered building my own, since I do agree that most of these are quite overpriced. It’s not as though they’re precision devices anyway.

author: Microdoser
author_rank: Frequent Contributor
timestamp: October 15, 2023, 10:43:34 am
content: Quote from: tooki on October 15, 2023, 10:40:18 amThis is exactly what's happening. I had hoped to find a non-expanding heatproof mat of some sort, but I think I'll just go to the local Wickes and get a large white tile for £1 and see if it can handle the heat until I can get a hotplate.

author: Microdoser
author_rank: Frequent Contributor
timestamp: October 15, 2023, 10:45:42 am
content: Quote from: tooki on October 15, 2023, 10:43:04 amWhat would be a situation where you would need an IR plate because a hotplate wouldn't do the job?

author: luudee
author_rank: Frequent Contributor
timestamp: October 15, 2023, 11:11:45 am
content: You might want to try the silicon mats they make for the Kitchen, to place hot pots and such.I have a dozen or so in my lab, but have never pointed hot air on them. All of mine are fromChina ...Good Luck !rudi

author: tooki
author_rank: Super Contributor
timestamp: October 15, 2023, 11:28:58 am
content: Quote from: Microdoser on October 15, 2023, 10:45:42 amUmmm:Quote from: tooki on October 13, 2023, 12:14:48 pmNeither of those is an uncommon scenario. Nor are boards that aren’tperfectlyflat (especially in rework, where a board may have been slightly warped from being in use, e.g. if an enclosure didn’t clip on just right).

author: Microdoser
author_rank: Frequent Contributor
timestamp: October 15, 2023, 12:31:23 pm
content: Quote from: tooki on October 15, 2023, 11:28:58 amAh yes, this would have been a perfect time for me to use my memory, hehe. Do you find IR melts the plastic on connectors and so forth? That would rule it out for me, as they are the only through hole parts I use.

author: thm_w
author_rank: Super Contributor
timestamp: October 16, 2023, 08:52:42 pm
content: IR can melt the plastic of connectors, if the connector is on the bottom exposed to the IR yes, similar to hot air. On the opposite topside, usually not.But its highly dependent on the quality of the connector, and what your reflow temperature will be (low temp, leaded, or lead free). Those cheap white JST connectors are the most heat sensitive for example.If I knew I was exclusively going to be using flat single sided SMD boards then I would get a hot plate. Instead got the Gordak 853. It can be annoying to work on to reposition the support arms, but not much can be done about that.This one is not crazy expensive:https://www.aliexpress.us/item/3256804886684972.htmlgordak a few dollars more.

author: Smokey
author_rank: Super Contributor
timestamp: October 16, 2023, 09:12:41 pm
content: Quote from: thm_w on October 16, 2023, 08:52:42 pmNames are funny. Sounds like an enemy of Godzilla... "Oh no! It's the Gordak! Flee! Flee!"

author: tooki
author_rank: Super Contributor
timestamp: October 16, 2023, 09:28:55 pm
content: Quote from: Microdoser on October 15, 2023, 12:31:23 pmYeah, it can. Those are best shielded somehow (e.g. metal foil taped on with Kapton tape). For hot air, just Kapton tape is often enough.For rework of difficult boards (big ground planes, heavy coax connectors, etc), the best approach is usually to just preheat with IR or gentle hot air, and use localized hot air or a soldering iron, as the situation requires, to actually melt solder. The idea being that, assuming you want to reach 230C for lead free, from an ambient temperature of 20C, you have to realize a temperature rise of 210C. Rather than using the iron or hot air to pump all that energy into a small part of the board (almost certainly requiring the iron or hot air to be well above 300C, potentially causing damage), you use IR or (gentler) hot air to preheat the whole board to, say, 150C (a temperature too low to cause damage). Now the iron or localized hot air only has to add 80C of heat, allowing the use of a much lower iron or localized hot air.