Pb solder wire :  Sn60/Pb40 or Sn63/Pb37 ? - Page 1
Forum section: electronics / projects

author: JacquesBBB
author_rank: Frequent Contributor
timestamp: January 31, 2023, 03:22:06 pm
content: Hello All,I see the end of my 500g 1mm main solder wire roll which is a Sn60/Pb40. I am wondering if I should switch to a Sn63/Pb37 mix, which is the eutectic mix.What is your best choice ?

author: coromonadalix
author_rank: Super Contributor
timestamp: January 31, 2023, 03:35:39 pm
content: i would not care 60/40 or 63/37BUT i would check for the core rosin type if it's acid based etc ....You have "no clean" types, rohs (for me the worst of them) sometimes you have to add liquid flux

author: TimFox
author_rank: Super Contributor
timestamp: January 31, 2023, 03:50:48 pm
content: Personally, I prefer Sn62 Pb36 Ag2 ternary eutectic alloy.Be sure to get rosin-core flux (RA or RMA) for normal THT and wire soldering, not "no-clean".No-clean is good for PCB assembly when the metal is clean.

author: JacquesBBB
author_rank: Frequent Contributor
timestamp: January 31, 2023, 03:58:45 pm
content: Thanks all for the advise on rosin core.@TimFox,what advantages do you see in Sn62/Pb36/Ag2 ? is it the lower melting point ?

author: JacquesBBB
author_rank: Frequent Contributor
timestamp: January 31, 2023, 04:12:30 pm
content: As this may be the last solder spool I buy, I better choose wisely . At Mouser, I seehttps://www.mouser.fr/ProductDetail/AIM/13772?qs=M7ZD%2F0QMIQxPWSj3dL3bjA%3D%3Dandhttps://www.mouser.fr/ProductDetail/Kester/24-7150-0018?qs=m5JL4TdtMhxY2BNlvHJMxg%3D%3Dfor Sn62/Pb36/Ag2Both in 0.025 in, rosin coreAny preference ?

author: mwb1100
author_rank: Frequent Contributor
timestamp: January 31, 2023, 04:52:30 pm
content: At least in the US for Kester solder you can find it repackaged in small tubes (often with the branch "NTE") on Amazon or eBay. I'd imagine something similar would be available in the EU as well. The tubes are generally in the $5-10 USD range, so it might be inexpensive enough to try out 2 or 3 to see what you like before spending 60+ EUR on a full spool.

author: mariush
author_rank: Super Contributor
timestamp: January 31, 2023, 06:19:39 pm
content: 63/37 and 62/36/2 are euctetic ... a bit better than 60/40 ... usually the ones with 2% silver are more expensive and often not worth it.go for RA, RMA and no-clean fluxes, they're fine. Avoid solders with water soluble fluxes or "organic fluxes" - the water soluble fluxes usually must be removed from pcb and must clean well (not with water as you may think) and the organic fluxes are usually quite strong and the fumes will hurt your lungs so you'd need to use a fume extractor.RA (rosin activated) , RMA (rosin mildly activated) , no-clean are more lung friendly - ventilation or some fan to blow the fumes is still recommended but if you solder just once in a while it won't do much damage to your lungs.I don't put that much focus on how much % flux the wire has inside, because for soldering new components, it's usually good enough.I also buy flux separately, you can buy liquid or gel flux for like 5$ for a 50-100ml bottle, and maybe 10-20$ for half liter bottle that would last you a long time.My favorite and the one I use now is multicore 63/37 0.56mm diameter with around 2.2% no-clean flux but there's Kester which is good and a few others.

author: TimFox
author_rank: Super Contributor
timestamp: January 31, 2023, 06:49:12 pm
content: Quote from: JacquesBBB on January 31, 2023, 03:58:45 pmSn63/Pb37 and Sn62/Pb36/Ag2 are both eutectic alloys, with a well-defined melting point.Sn60/Pb40 is almost eutectic, but there is a "slushy" narrow temperature range between "solidus" and "liquidus" temperatures.With a non-eutectic alloy such as Sn40/Pb60 (sometimes used for its higher melting point), when the temperature rises above the melting point for the eutectic alloy Sn63/Pb37, it is something like solid lead suspended in liquid eutectic until you get to the higher "liquidus" temperature.I like the silver-bearing ternary eutectic because it's shinier, but 63/37 solders approximately as well.Some of the lead-free alloys are also eutectic.Rosin fluxes may leave a noticeable residue, but it is generally non-conductive, non-corrosive, and harmless. I have had problems in critical high-impedance applications with no-clean flux residues reacting with humidity to leave ionic conductance on circuit boards.

author: TomWinTejas
author_rank: Regular Contributor
timestamp: January 31, 2023, 07:19:47 pm
content: Quote from: mwb1100 on January 31, 2023, 04:52:30 pmWith all the counterfeit products on Amazon and eBay I am not sure I'd trust those sources for a point of comparison.It looks like Allied and Newark have smaller packages and I think they both have warehouses in Europe that might make shipping cheaper?https://www.alliedelec.com/product/kester-solder/83-7145-0415/70230223/https://www.newark.com/kester-solder/83-7145-0415/leaded-lead-free-leaded/dp/84R8809

author: Siwastaja
author_rank: Super Contributor
timestamp: January 31, 2023, 07:27:30 pm
content: Quality, amount and application of flux (proper multicore vs. some crappy here-and-there core) is far more important than if it's perfectly eutectic or just close, IMHO.Solder quality only affects the ease of soldering, and if the results are bad, you totally see it with your eyes. In other words, if you are not having any troubles with it, there is no need to switch. On the other hand, if you struggle to get good results, it's always a good idea to test another brand.

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: January 31, 2023, 08:53:27 pm
content: Eutectic is probably preferable but either will work fine. RMA flux (rosin, mildly activated) is the best all-around choice. No-clean doesn't seem as effective and might cause hi-Z problems. Water-washable is great, but only if it can be thoroughly washed. I use it on new boards, but never repairs. If you work on old Tektronix scopes or very fine copper wires, get the 2% silver.

author: TimFox
author_rank: Super Contributor
timestamp: January 31, 2023, 11:01:09 pm
content: Quote from: Conrad Hoffman on January 31, 2023, 08:53:27 pmThe silver-bearing solder is mandatory for old Tektronix scopes, which used silver-metallized ceramic terminal strips. Without silver in the solder alloy, the silver would leach from the ceramic surface into the molten solder and damage the terminals.

author: JacquesBBB
author_rank: Frequent Contributor
timestamp: January 31, 2023, 11:14:42 pm
content: Quote from: TimFox on January 31, 2023, 11:01:09 pmI think I will take your advices into account. I do a lot of repair on old lab instruments. Maybe not much old Tektronix scopes, but I will not have several spools of solder either. So I need some that I can use in all circumstances. I already have some very thin SN63/Pb37 solder wire which I use for SMD soldering. So from what you say, getting a main spool with Ag2 will be a good option. I will take care that it is with rosin core.I am surprise that many brand say that it cannot be cleaned with IPA, but I suspect this is because they want to sell their own specialized flux cleaner.

author: Benta
author_rank: Super Contributor
timestamp: January 31, 2023, 11:24:53 pm
content: Quote from: TimFox on January 31, 2023, 11:01:09 pmThis is from ancient memory, but I remember intercrystalline problems with eutectic solder on gold-plated PCBs and component pins. The fix was the 2% Ag additive to the solder. But i may remember wrongly.

author: TimFox
author_rank: Super Contributor
timestamp: January 31, 2023, 11:40:59 pm
content: Quote from: JacquesBBB on January 31, 2023, 11:14:42 pmIf I remember correctly, IPA will not remove rosin flux residue well, but there are special flux cleaners for when you need to remove it.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: February 01, 2023, 01:02:02 am
content: Any will do, preferably leaded, preferably the more rosin-bearing not-no-clean kinds. 60/40 is cheaper, and the case can probably be made that it dilutes slightly with pin/lead plating (usually tin) or when working with mixed (lead-free) joints as in repair, getting closer to eutectic in the process. Well, that probably doesn't actually happen to a meaningful degree, with how thin most platings are, and how much solder you'll use by hand, but it's fun to think about I guess?63/37 is just a little nicer to use, but does cost a premium. Silver bearing is stronger, but costs more still. As mentioned, there are places where it may be required.Thinner wire is also recommended, but it depends on what you're doing. If you're doing mostly chassis repair (vintage terminal strips and stuff), thicker is good. Thinner is easier to use on PCBs, especially with fine SMTs around.You can always get multiple kinds, too! You'll most likely lose the opportunity for a bulk discount that way, but it won't be as expensive as, say, straight doubling your order.Or maybe you find a good deal on something anyway and just go with it. I picked up something like 3 lbs (~1.36kg) 63/37 no-clean a bunch of years ago, for like half retail price, and I'm just now finishing up the last roll of it.The only thing to absolutely avoid is acid-core, or some strongly-activated rosins (but I think none are as bad as acid-core per se?). Everything else is some permutation of technique, temperature (get a reasonable temperature-controlled iron, like WESD51 or similar; use it at different temperatures, see how soldering performance is versus how quickly the tip fouls / flux chars, find a balance; also turn it down when not in use, greatly saves tip life!), or just using paste/gel flux on top of everything!True for lead-free as well: leaded is easier to work with, lower melting, smoother deposit generally; but lead-free is not much of a challenge to use, just get suitable fluxes for it -- the higher working temp tends to char, evaporate and use up rosin-based types pretty quickly. Both are fine with practice, lead-free just takes a bit more practice.Tim

author: David Hess
author_rank: Super Contributor
timestamp: February 01, 2023, 02:22:29 am
content: You will be hard pressed to distinguish Sn60/Pb40 from Sn63/Pb37 in use. Either will work fine.Quote from: Benta on January 31, 2023, 11:24:53 pmGold is a problem with tin bearing solders because the gold-tin intermetallic is brittle, and if the gold is not completely dissolved into the joint, then the interface between the gold and tin will diffuse making the joint very weak until it fails.To avoid this, the gold plating is made thin enough so that it completely dissolves into the solder without reaching the concentration where the solder becomes brittle, or the gold is removed before soldering the final joint.

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: February 01, 2023, 03:58:53 am
content: Quote from: TimFox on January 31, 2023, 11:01:09 pmIIRC the real Tektronix solder is 3% silver. Probably the 2% is good enough; at least I hope so because that's all you can find easily. Radio Shack even used to sell 2%.

author: tooki
author_rank: Super Contributor
timestamp: February 01, 2023, 07:50:12 am
content: The quality of the solder (purity of the alloy, quality of the flux) matters more than whether it’s 63/37, 60/40, or 62/36/2.That’s also my order of preference if shopping: 62/36/2 flows slightly worse than 63/37, and it’s a lot more expensive, so I wouldn’t buy it unless explicitly needed (e.g. for soldering pure silver terminations on old Tek).Quote from: Siwastaja on January 31, 2023, 07:27:30 pmThe consistency of the core, and the quality of the flux within it, is vastly more important than whether it’s a single or multiple core. I have found no solder I like better than Kester 44 63/37, and Kester is single core.Quote from: JacquesBBB on January 31, 2023, 11:14:42 pmMany fluxes contain activators that aren’t fully soluble in IPA, or that react with the tin to create metal salts that aren’t soluble in IPA. The result is the white residue that is sometimes seen. Commercial flux cleaners do a better job at this.Additionally, the solvent blends in commercial flux cleaners work with much less effort than pure IPA, and you need less of it. For that reason alone, I just use flux cleaner and don’t bother with IPA.Quote from: T3sl4co1l on February 01, 2023, 01:02:02 amThat hasn’t really been the case for a while. Now that mass production has all gone lead-free, leaving lead solder as a niche product, 63/37 costs the same as,and often lessthan 60/40!Not that the difference in price was ever large, just a few dollars per pound. Sure, in mass production that means lots of savings, but for hobby use, an absolutely negligible difference that I consider more than worthwhile.

author: coromonadalix
author_rank: Super Contributor
timestamp: February 01, 2023, 11:23:15 am
content: when you pay 250$ cad for 1 pound of 63/37 rozin core 0.010 size you'll understand lollpricing as gone bezerkand yes IPA in some case is not able to clean some residues, i wont tell you what i use in theses cases loll oh well ace "cough" toneor very specialized stuff like atron sc200 or vigon etc .....

author: mariush
author_rank: Super Contributor
timestamp: February 01, 2023, 12:40:28 pm
content: Quote from: coromonadalix on February 01, 2023, 11:23:15 amGoogle says $107 (rosin rma) :https://www.testequity.com/product/488SO756-24-6337-9756Digikey has it for $115 :https://www.digikey.com/en/products/detail/kester-solder/24-6337-9756/7565078New old stock but with no-clean flux is available on ebay for 35$ each (made in 2019, with "expiry date" in 2022) :https://www.ebay.com/itm/234588780062

author: Gyro
author_rank: Super Contributor
timestamp: February 01, 2023, 01:50:37 pm
content: Quote from: TimFox on January 31, 2023, 11:01:09 pmA quick snap as I'm right in the middle of repairing my 475A (it only has ceramic strips in the HT section)...

author: Haenk
author_rank: Super Contributor
timestamp: February 01, 2023, 02:11:35 pm
content: That ebay offer seems good.That exp date is just for the books (and for industrial/commercial use). It will likely be fine for another couple of decades.

author: tooki
author_rank: Super Contributor
timestamp: February 01, 2023, 06:37:16 pm
content: Quote from: coromonadalix on February 01, 2023, 11:23:15 amSuper thin solder has always been expensive. The cost there is the labor, not the materials, so there will be practically no difference between 63/37 and 60/40.Solder that thin is also something almost no hobbyist needs.Normal thicknesses are around $50/lb, which I think is just fine. You can find it for $35 by shipping around.

author: exe
author_rank: Unknown
timestamp: February 03, 2023, 09:04:53 am
content: Quote from: tooki on February 01, 2023, 07:50:12 am+1 to that, onhttps://www.youtube.com/@RusFluxInfo(in Russian) a lot of solders were tested for their content and many had a lot of impurity, or tin content was lower than advertised (because it's more expensive than Pb). So, I'd say buying a quality solder is more important than chasing that 63/37 vs 60/40.