How to fill up excess space in a solder pot? - Page 1
Forum section: electronics / general

author: t1d
author_rank: Super Contributor
timestamp: November 22, 2021, 03:00:16 pm
content: I have never used a solder pot. I have purchased a small one. It occurs to me that I am not going to need but a portion of the depth of the pot. Meaning...- I have to buy more solder than is needed. At about $30USD/pound, that is significant, given my monthly budget.- The excess solder is going to waste power to keep it hot.- The excess solder increases the severity of any spill.The only use that I can imagine for the extra depth is to create a thermal mass that keeps the molten solder fluid. But, the device regulates the heat. And, if I can use some other type of melt object to fill the unused space, it can serve as the "heat swamp."If I can add some type of object, what do you suggest, as to the device, itself, and what it is made out of?

author: David Hess
author_rank: Super Contributor
timestamp: November 22, 2021, 03:36:05 pm
content: The solder pots I have seen are cast iron, so putting some pieces of cast iron in the bottom is one option. I think unplated steel, or stainless steel would also work fine.

author: t1d
author_rank: Super Contributor
timestamp: November 22, 2021, 04:20:29 pm
content: Quote from: David Hess on November 22, 2021, 03:36:05 pmThanks, David. I can always count on you for good information.

author: langwadt
author_rank: Super Contributor
timestamp: November 22, 2021, 04:41:14 pm
content: Quote from: David Hess on November 22, 2021, 03:36:05 pmwhat's the density of steel vs. solder? will it float?

author: pqass
author_rank: Super Contributor
timestamp: November 22, 2021, 04:43:29 pm
content: Or round aluminium disks?Just leave a gap with the side wall and make sure there is solder below. Stack as many as you need.But will it float? Hmm....Nevermind,just buy a stack of washers with the appropriate outer diameter. I would avoid anything galvanized/zinc.https://www.homedepot.com/p/Hillman-Stainless-Steel-Flat-Washer-1-2-Screw-Size-2232/204786026#specifications

author: Gregg
author_rank: Super Contributor
timestamp: November 22, 2021, 06:12:54 pm
content: You will need something that has a higher specific gravity than the solder you are using. I believe steel or iron will just float to the surface. Copper may work.

author: wraper
author_rank: Unknown
timestamp: November 22, 2021, 06:15:41 pm
content: Quote from: Gregg on November 22, 2021, 06:12:54 pmCopper will dissolve and ruin the solder.

author: Gregg
author_rank: Super Contributor
timestamp: November 22, 2021, 07:10:40 pm
content: Quote from: wraper on November 22, 2021, 06:15:41 pmI seriously doubt a hobbyist would notice the difference. The solder will alloy with the copper a couple of molecules deep and will tend to stop further alloying unless the copper is scraped clean or gets close to the melting point of copper. Dipping copper wires int the solder pot probably has more effect than a slug of copper resting on the bottom.

author: chickenHeadKnob
author_rank: Super Contributor
timestamp: November 23, 2021, 01:29:16 am
content: The original ask here is based on 2 misapprehensions: First that solder at the bottom of the pot is somehow an extra expense. It isn't if you intend to make use over a long period of time. Eventually you will be replacing it as it is used up so... it more like a shop keeper who puts cash in register (a "float") at the start of the day so that he can make change. He is not going to lose anything. Second the added mass of solder does take longer to melt, but so what solder pots are meant for production runs not 5 minute jobs.Finally if you haven't used one before you are going to be surprised at how much dross is generated on the surface and you will need to keep skimming it. Solder pots are messy and don't conserve solder in any aspect.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: November 23, 2021, 04:22:00 am
content: It doesn't really need to be filled up, does it?Mind, I haven't used many, so, honest question actually.Heat dissipation is likely same or maybe even higher, because heat is dissipated from surfaces. Volume has nothing to do with it, just takes longer to heat up. One difference would be, if heat isn't applied evenly to the crucible, maybe the above-level region gets overheated, and that's bad.I'd be tempted to think a shallow (controlled) level might even be helpful, like, when you're tinning a bunch of stranded ends you just dip to the bottom and there you are, no worry about messing up the insulation. Well, doesn't exactly work with fine strands that you'll mush up doing that, and you probably shouldn't be tinning coarse strands that are better used in a crimp joint anyway -- but in the event that you do, maybe that's helpful? And anyway, just not having enough to cover, it just shouldn't be a big deal?I don't find solder to be a big deal, for sure you don't want to melt down good rosin-core, what a mess besides. Recycled should be fine, it'll be only a little dirtier and cleans up well with a little fresh rosin.And I seem to remove or waste enough solder, to have grown a sizable collection over the years -- in fact I melted it all down last year and made a usably thin bar of it. The alloy is rather mixed, probably too much on the tin side, from lead-free waste? That, and the increased copper or other metal content, probably tends to just strengthen it (with the downside of having a wider slushy melt range).FYI:- Iron dissolves negligibly in solder (especially lead, but a little bit tin)- Copper, silver and antimony dissolve at least a few percent at typical soldering temperatures. The metals do take some time to get there, so reused solder won't be elevated by all that much, for the most part. They are regularly used to strengthen the alloy, in various combinations.- If you're doing lead-free, mind that possible formation of tin whiskers is a spooky matter and may depend on alloy constituents (or lack thereof), as well as heating profile, finish, etc. (I don't know all the research with respect to alloys, other than lead just slam-dunk fixing the problem. Plain old SAC305 in standard processes seems to do awfully well, so it doesn't seem to require much, at least to slow the growth, if not fully avoiding it.)- Do avoid zinc and platings (galvanized steel), as zinc dissolves in tin (and moderately in leaded solder; lead and zinc are immiscible, but tin makes them reluctant partners), and makes the pot much scummier (zinc oxidizes so much faster than the rest, and doesn't respond well to rosin).I don't know that zinc has much effect beyond the usual alloying effect (trading ductility for strength), or if there are other knock-on effects like corrosion or cracking. Probably best to avoid overall? (I do know lead is supposed to have a marked effect on zinc alloy (pot metal), apparently even in small amounts (~0.05%) causing it to eventually crumble, though it may take decades, centuries even, to happen. I don't know if that's true the other way around, i.e. for lead- or tin-based alloys. Maybe not?)Quote from: chickenHeadKnob on November 23, 2021, 01:29:16 amYeah, you'll always get it back, of course; give or take any trash that's sunk to the bottom, mind; it pays to decant the liquid off the top, and try to strain/scoop the crud off the bottom. (A bigger problem with recycled/reclaimed solder than for normal use of a solder pot, though I imagine you'll lose the occasional nicked/broken strand in there so eh, just keep an eye out and be careful.)And yup, flux generously. If you're dry-skimming a lot, consider reclaiming it once in a while -- it'll still be like 90% good metal, just drop it in, let it melt, and stir it around with some fresh rosin. Scoop out the nasty smoking crusty rosin and oxides, and you're good to go again. Use lots of ventilation of course; not so much for lead fumes per se (lead doesn't evaporate appreciably at this temperature), but you just don't want to be breathing all that partially-burned organic vapor, plus any lead dust it might be carrying along. Probably trying to maintain a cover flux of rosin or etc. isn't practical, but flux the wire, and give the bath a nice cleaning once in a while, it'll be fine.Quote from: Gregg on November 22, 2021, 07:10:40 pmIf it makes (metal-on-metal) contact, it will eventually dissolve. Saturation point depends on base alloy and temp: Pb holds about 0.2%wt Cu at 427°C, and Sn holds about 1.7%wt at 277°C. (I don't have data on alloys; there may be higher solubility in the mix, or it might be lower simply because the working temp is lower.)If you want to slow it down, you might heat it red hot first. The copper oxide layer will take some time to dissolve. It's easily nicked by abrasion, and is slowly dissolved by rosin, so expect it dissolve eventually (think of the potholes in the last unplated (pure copper) soldering iron tip you had? (if ever)).The next most common, insoluble and dense metal I can think of... molybdenum maybe? It's... certainly available, but uncommon, you'll have to go out of your way to get some, it's not the cheapest thing. Unless you happen to find a nugget just the perfect size or something. Or uh, rocks, or ceramics, probably not much, unless it's a compound of a dense element like this -- and even then, like, molybdenite is much lighter than solder so it'll need to be much denser than that. Tungsten carbide maybe? Or plain old tungsten itself of course, but good luck machining it if it doesn't perfectly fit in your pot...Tim

author: David Hess
author_rank: Super Contributor
timestamp: November 23, 2021, 04:52:02 am
content: Quote from: langwadt on November 22, 2021, 04:41:14 pmThat is a good point. Whatever is put at the bottom of the pot will need to be screwed down.

author: t1d
author_rank: Super Contributor
timestamp: November 23, 2021, 06:07:01 am
content: Wow, you folks are v-e-r-y impressive. Bottom line, y'all (Southern, for you) know stuff. Cool!. Thanks for all of the information and input.Using rock, ceramic, concrete, etc. for the fill, might be dangerous. IIRC, rock plus heat = explosion, doesn't it? Probably due to the expansion of trapped water.I wonder if JB Weld might work, to attach the fill to the bottom, to prevent it from floating.Isn't molybdenum light in weight, like aluminum?The pot is filled to the brim to allow the user to dip the bottom of a PCB into the solder pool, which makes all the solder joints in just one swipe.

author: David Hess
author_rank: Super Contributor
timestamp: November 23, 2021, 06:10:53 am
content: Quote from: t1d on November 23, 2021, 06:07:01 amThat is right, and you will still need to fasten it down.Tungsten and tungsten carbide are denser than lead so could be used without fastening them down.

author: t1d
author_rank: Super Contributor
timestamp: November 23, 2021, 06:13:13 am
content: Quote from: David Hess on November 23, 2021, 06:10:53 amI'm sorry, David, but I was editing, while you were writing. See my prior post.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: November 23, 2021, 12:11:23 pm
content: Yes, you'd want to be very careful indeed using rocks -- some trap moisture which can explode suddenly. Heat treating beforehand (say, very slow heating, to a higher final temperature) would be a wise precaution.I wouldn't think JB Weld would survive the heat. It's rated quite generously, but solder pots can run quite hot indeed.A cement (basically, bonded-in-place ceramic) might do. Not sure offhand what. But this would be a more difficult modification to roll back, and would increase thermal resistance between crucible and melt.Tim

author: jonpaul
author_rank: Super Contributor
timestamp: November 24, 2021, 08:17:49 am
content: Bonjour just see this odd note now and the other from same OP, re pot safety. We use the Plato posts for decades never had these issues.We size the pot to be appropriate to the parts being soldered.Exactly what type solder and brand/model solder pot? Use for occasional/hobby, protos or manufacture? What are you soldering?1. Any filler may contaminate the solder alloy, changing the melting and plastic temps and properties. RoHS lead free demands a special crucible and only use of the same RoHS alloy.2. RE cost we find bars at very reasonable cost $15...22 /lb, most pots hold 1-5 #3. The power consumed to idle a pot is not much affected by the contents filler/solder, it is the specific heat and losses radiation/conduction/convection.4. JB weld and other suggestions can create oxides and gasses, and are not a solution.5. Use a good flux and skim dross frequently.Bon chance,Jon

author: mfro
author_rank: Regular Contributor
timestamp: November 24, 2021, 08:25:25 am
content: Gold would be a good replacement for steel as it has a higher specific weight... and the pot would keep your treasures perfectly safe at the same time

author: MarkF
author_rank: Super Contributor
timestamp: November 24, 2021, 08:27:03 am
content: A piece of 'fire' brick would probably be safe enough.But, it would probably float.You know; the special brick they use in a fireplaces.I missed the part where you think it needs to be full???

author: Ian.M
author_rank: Super Contributor
timestamp: November 24, 2021, 09:31:25 am
content: Unless you are using an exotic solder alloy, filling the pot with solder is likely to be significantly cheaper than anything that can safely reduce its volume. Anything dense enough to stay at the bottom with a high enough melting point and not soluable in solder so it doesn't contaminate it, is going to be more expensive than bar solder, and unless you've got a well equipped machine shop and a rack of large steel offcuts, a machined steel slug to fit your pot and some sort of heat and solder resistant expanding clamp to hold it at the bottom wont be cheap.

author: jonpaul
author_rank: Super Contributor
timestamp: November 24, 2021, 09:48:19 am
content: Rebonjour from Paris,Cher Ian, very fine pointsSuggestions of filler seem costly or potential contamination problems.Since my experience 50 yrs in electronic mfg and magnetics, I have NEVER heard of this idea.We always fill to the lip of the crucible.I am unsure the meaning of "Exotic alloys"We have only seen bar solder :63/37 Eutectic Tin/lead60/40 Tin/leadRoHS eg SAC305, SA100C etc.Finally, the very best crucibles are not the iron but ceramic coated or céramique, long life and great for RoHS solder but costly and hard to get.Bon Chance,Jon

author: Ian.M
author_rank: Super Contributor
timestamp: November 24, 2021, 09:54:01 am
content: Exotic alloys: I was thinking of low temperature solder alloys containing Indium, which can cost as much as several dollars per gram!

author: jonpaul
author_rank: Super Contributor
timestamp: November 24, 2021, 11:58:57 am
content: Never in a solder pot, danger due to vapor of low ment point and lowest solder pot temps normally 100C or moreJon

author: wraper
author_rank: Unknown
timestamp: November 24, 2021, 01:40:46 pm
content: Quote from: Gregg on November 22, 2021, 07:10:40 pmNo, it will keep dissolving. There will be no protective layer forming.

author: langwadt
author_rank: Super Contributor
timestamp: November 24, 2021, 02:16:06 pm
content: Quote from: mfro on November 24, 2021, 08:25:25 amgold mixes with the solder and makes it brittlethrown in some old carbide milling bits?

author: mfro
author_rank: Regular Contributor
timestamp: November 24, 2021, 03:56:27 pm
content: Quote from: langwadt on November 24, 2021, 02:16:06 pmAt solder pot temperatures? I must admit I never tried myself, but I would seriously doubt that. It's purely academic anyway, isn't it?

author: Ian.M
author_rank: Super Contributor
timestamp: November 24, 2021, 04:18:57 pm
content: Yes, at regular soldering temperatures.See:https://www.solder.net/gold-embrittlement-mitigation/

author: jonpaul
author_rank: Super Contributor
timestamp: November 24, 2021, 04:53:46 pm
content: Value Au ~ 1850$/ozIf 22 or 24 caret is melted or combined the value is virtually nothing

author: Ian.M
author_rank: Super Contributor
timestamp: November 24, 2021, 05:13:28 pm
content: Quote from: jonpaul on November 24, 2021, 04:53:46 pmNot exactly true. If there's enough of it to cover the cost of assaying it then alloying it to a known marketable composition, or refining it to fine gold, its worth the value of its gold content less the cost of recovery, which is more or less fixed for quantities small enough to refine or alloy as a single batch. If not, well gold scrap goes for silly prices on Ebay ...

author: langwadt
author_rank: Super Contributor
timestamp: November 24, 2021, 05:36:56 pm
content: Quote from: Ian.M on November 24, 2021, 05:13:28 pmremember reading the about 40 cellphones contain as much gold as 1 ton of ore from an average goldmine(~1gr)

author: T3sl4co1l
author_rank: Super Contributor
timestamp: November 25, 2021, 02:17:06 am
content: Also for reference, tinning is used in high-reliability processes specifically to wash the surface of gold, to prevent formation of Au-Sn intermetallic layers which are especially weak. So you'll see certain NASA documents for example, instructing connector pins to be tinned, cleaned, tinned again, etc., then finally assembled with the wire or board. (You'll also see ones tinning pure-tin surfaces with leaded solder, to help prevent whisker formation. Over the time scales in which satellites and avionics must operate, this is key; however for commercial, industrial and automotive purposes, it seems tighter process control is sufficient to offer 10yr+ product lifetimes in lead-free.)Tim

author: tooki
author_rank: Super Contributor
timestamp: December 12, 2021, 12:09:22 pm
content: Quote from: mfro on November 24, 2021, 03:56:27 pmIt doesn’t have to reach the gold’s melting point.Table salt melts at about 800°C. Ice melts at 0°C. Yet molten ice (i.e. water) can dissolve salt at temperatureswellbelow 800°C. Same concept with metals: a molten metal can dissolve another metal long before reaching the second metal’s melting point.Similar effects apply in glassmaking, where certain mixtures of ingredients will melt at temperatures lower than the individual melting points of the individual ingredients.

author: David Hess
author_rank: Super Contributor
timestamp: December 12, 2021, 08:13:51 pm
content: Quote from: mfro on November 24, 2021, 03:56:27 pmAbsolutely the gold will dissolve into the solder, specifically the tin part. Copper or silver dissolve into tin as well which is why copper soldering iron tips are plated in iron. A pure copper soldering iron tip, or brass or bronze, gets eaten away quickly.Flash gold plating is intended to completely dissolve into the solder without causing enough concentration for embrittlement, but heavy gold plating will cause problems and must be removed before soldering. Often the method of removal is to just apply solder and heat for long enough to dissolve all of the gold plating into the solder, then remove the contaminated older and apply new solder for the joint.

author: Hydron
author_rank: Super Contributor
timestamp: December 27, 2021, 07:02:31 pm
content: Throw a few scrap (worn) tungsten carbide cutting inserts in the bottom? Will be way denser than the solder.I actually have a 7kg chunk lying around (part of a roller from a hot-rolling mill that exploded in use) - it's an unexpectedly heavy and satisfying object, I just wish I had a similarly sized piece of pure tungsten, which would be even more impressive. Sadly I missed out on getting an entire (~25kg) roller

author: coppercone2
author_rank: Super Contributor
timestamp: December 28, 2021, 01:54:14 am
content: cut that up into blocks for glue or welding alignment, if its possible, those would be highly useful objects.