Mixture of solder (lead and leadfree) when repairing old equipment? - Page 1
Forum section: electronics / repair

author: nightfire
author_rank: Frequent Contributor
timestamp: April 30, 2022, 09:23:41 pm
content: Situation: I am in germany, where due to RoHS leaded solder (at least officially) is hard to come by.As I have currently a project of repairing (and understanding) some old lab power supply build around 1987, I would have the generic question of the best approach of solder to use.As this probably applies to lots of other old gear that uses leaded solder, I put this thread standalone, as other folks probably are in the same situation...Anyway, the gear in my case is from 1987, very probably build with leaded solder. (Fun fact: on the website of the manufacturer it says under RoHs statement: Our equipment is intended for military use, so no exempt from RoHS regulations)Questions here:a) To which extent is leaded solder needed with material characteristics for maybe vibration dampening? The Lab Power supply in my case is intended to be used in a military context, but is not ruggedized, rather a mechanical high-quality version of a standard linear lab power supply, build with all discrete parts, no SMD.b) should i use leaded solder for work like recapping?c) What would be the consequences of mixing solder types, especially with maybe soldering joints that have not been thouroughly cleaned from previous solder when desoldering a component?d) should I have separate soldering irons/tips for using leaded and unleaded solder?Apologies when a similar thread is still open where this exact question has been discussed concisely- in that case, could someone point me to that thread?

author: 2N3055
author_rank: Super Contributor
timestamp: May 01, 2022, 07:52:10 am
content: Quote from: nightfire on April 30, 2022, 09:23:41 pmMixing solder is very bad (as in adding lead free on top of existing leaded solder). It will leave you with a very brittle mix of solder. Separate solder tips are not really necessary if you clean them well and rewet with solder you are going to use. To avoid that you could have separate tips. Separate tips are also used in ROHS where there is testing that will show minutest traces of lead...In short, simplest and best is to find leaded solder and repair leaded equipment with it.. Separate tip would be nice, but not strictly necessary if you clean them really well at change back and forth. Make note it will leave trace residue of lead on tip that can be detectable with ROHS testing, although wont make practical difference (if cleaned well).This is "hobby" advice. For pro use, leaded equipment should be repaired only with proper leaded formulations (as original) and new lead free with lead free. No equipment should be shared (tips, cleaners ..)

author: jeremy
author_rank: Super Contributor
timestamp: May 01, 2022, 08:22:04 am
content: I have never had a problem mixing as long as bismuth is not involved. Bismuth/Lead alloys are very soft with low melting points and you can just pull SMD parts off PCBs with tweezers in some circumstances.I think for a hobbyist the risks are way overblown; it’s not like your equipment is going to experience large repeated shocks or heavy vibration… I’m also not convinced I have ever seen a failure due to mixing of alloys that would have not occurred with unmixed alloys (in hobbyist equipment).

author: janoc
author_rank: Super Contributor
timestamp: May 01, 2022, 09:48:54 am
content: Quote from: jeremy on May 01, 2022, 08:22:04 amThe joint brittleness described above is a real thing - but unless the device in question is going to be exposed to vibrations (e.g. in a car or as a part of a household appliance which has a motor - washing machine or something like that), it is likely to be fine.I am routinely doing the opposite to what the OP describes - repairing electronics that has been soldered using lead-free solder (99% of commercial stuff from the last 20 years or so) with leaded solder and never had a joint fail on me either.Of course, it is not acceptable to do so as soon as RoHS compliance is involved or where utmost reliability is required but DIY/personal use it is fine.

author: janoc
author_rank: Super Contributor
timestamp: May 01, 2022, 09:54:33 am
content: Quote from: RoGeorge on May 01, 2022, 09:13:08 amGiven that the OP is using lead-free solder already, then they likely have a tip with the proper plating. Leaded solder won't corrode a lead-free tip, it is the lead-free solder that is known to eat tips intended for leaded for lunch because they don't have as good plating.Having separate tips is required only if you care about RoHS compliance (not a concern for personal stuff) or must have the best possible reliability due to avoiding mixing of the alloys (probably doesn't matter for personal projects).

author: Spectrum
author_rank: Regular Contributor
timestamp: May 01, 2022, 01:55:08 pm
content: Using 60/40 (or 60/38/2Cu) alloy for limited repair (NOT board construction) is also allowed by RoHS regulation. In fact, you can still safely buy all the 60/40 alloy you want, if it were illegal, it wouldn't be possible. A repair is always visible compared to a virgin board.As I think, if I have to repair joints with lead-free alloy, first I eliminate the alloy present and then I go back up with an excellent quality 60/40 alloy (STANNOL, Felder, BW Billiton,Weller etc ..).I know repairmen who mix the two alloys to save time, but I am not.No need to keep separate tips for the two alloys, as long as quality equipment is used. The lead-free alloy uses higher temperatures and therefore is more damaging to the life of the tips, but that's another story.

author: nightfire
author_rank: Frequent Contributor
timestamp: May 01, 2022, 02:42:22 pm
content: Thanks for all the input so far!In my situation, I do this as a hobby project, so my usual trustworthy suppliers that cater to private customers do not have leaded solder available.Also I do not need big amounts of it, as the stuff I probably also will repair in the future is not very big.From what I have read so far, I conclude:- Repair with leaded solder is always allowed under RoHS conditions, additionally for hobby use- Soldering tips can be kept separate for leaded and unleaded, but with good cleaning, there is no need to do so (for hobby usage)- newer soldering tips consist of a better material to be able to keep up with unleaded solder (My soldering iron is about one year old, so no worries here)- do not mix leaded and unleaded solder->clean the pcb after desoldering parts thouroughly, better use same solder type as the manufacturer didCurrently I am going for some smaller amounts of old solder, from what I learned from some search is that for electronics use, the flux should be of the F-32 type, because that is essentially "no-clean". The older standard F-26 means some slight agressiveness, so that stuff requires some cleaning afterwards.(And for the germans: The old designation of Stannol "Bastlerlot is intended rather for metalworks and has a quite aggressive flux- therefore should not be used on electronics)

author: Ian.M
author_rank: Super Contributor
timestamp: May 01, 2022, 02:52:03 pm
content: Why wouldn't you use as close as you can to the same solder alloy as the original for any repair work? While Sn/Pb based solder alloys tolerate a moderate shift in composition (due to mixing) away from the Sn63/Pb37 eutectic without gross changes in their electrical and mechanical characteristics, the same is *NOT* true of common post-ROHS Pb-free solder alloys. As little as 0.5% Pb contamination can halve the fatigue life of the joint ().Lets suppose you repair one joint on a post-ROHS board with Sn/Pb solder - you suck off the Pb-free alloy and remake the joint properly - or the same on a pre-ROHS board with Pb-free solder, then in the future, anyone touching up joints is likely to carry lead contamination from a Pb containing joint to other Pb-free joints retouched after it, leading to premature failure.The ROHS limit is Lead (Pb): < 1000 ppm. That is a 0.1% limit on Lead concentration.You don't *NEED* different irons or tips for pre and post-ROHS soldering - Start with a tip that has been used for Sn/Pb solder, wipe your tip as clean as possible, and tin it generously with Pb-free solder, and you've just reduced the Pb concentration by at least a factor of ten by simple dilution. Repeat two more times, and as long as your Pb-free solder's trace Pb content is well under the ROHS limit, your tip is certain to be under the limit as well.Its almost always OK to simply wipe and tin twice then wipe. You don't start from 100% lead, and the reduction per wipe/tin is usually more than a factor of ten + any traces will be further diluted in the first joint so it meets the limit.Going the other way is easy, wipe off the Pb-free solder, re-tin with Sn/Pb and wipe off excess solder and it will be close enough, as long as the Pb-free solder wasn't an exotic low melting point alloy.Of course, in a commercial setting its good practice to have separate bits, and separate tools makes sense as then you can color code everything including the solder reels and avoid mix-ups, but if you have to switch from non-ROHS to ROHS compliance doing field repairs, with a limited toolkit, clean the iron properly and you will be OK as long as you have the correct solder.

author: tooki
author_rank: Super Contributor
timestamp: May 01, 2022, 08:14:28 pm
content: Will Digi-Key or Mouser ship you leaded solder from USA? (I haven’t tried doing it recently, but neither website stops me from adding it to my cart.) One large roll of leaded solder and some flux would probably get you over the minimum for free shipping.

author: Audiorepair
author_rank: Frequent Contributor
timestamp: May 01, 2022, 08:28:04 pm
content: It is not difficult to get leaded solder in Germany or most other EU countries.https://de.farnell.com/multicore-loctite/dlmp24-250g-reel/l-tdraht-lmp-0-56mm-250g/dp/419552?ost=419552

author: james_s
author_rank: Super Contributor
timestamp: May 01, 2022, 09:16:18 pm
content: I use 60/40 leaded solder for everything, it just works better and at the scale I'm working with it is no issue at all. Buy a roll, imported if you have to and you'll probably have a lifetime supply.

author: Audiorepair
author_rank: Frequent Contributor
timestamp: May 01, 2022, 10:05:32 pm
content: https://de.farnell.com/stannol/hf32-3500-1-0mm-250g/l-tdraht-60-40-183grad-250g/dp/817612

author: nightfire
author_rank: Frequent Contributor
timestamp: May 02, 2022, 01:20:38 am
content: Quote from: tooki on May 01, 2022, 08:14:28 pmWill probably give some issues at import at customs check, as I am a private user.I remember the trouble we had as we wanted to get at my last employer a replacement for a serial console server that was not RoHS compliant and the spare part would have been needed to import in the EU from the US.... Was not nice and a bit of drama...Anyway, a visit on ebay hopefully solved the issue, got some old stock from another hobbyist...

author: tooki
author_rank: Super Contributor
timestamp: May 02, 2022, 05:48:17 am
content: Quote from: nightfire on May 02, 2022, 01:20:38 amWhat customs inspection? Both of those distributors ship with customs pre-cleared.

author: janoc
author_rank: Super Contributor
timestamp: May 02, 2022, 08:52:45 pm
content: Quote from: Audiorepair on May 01, 2022, 08:28:04 pmUnless you are a business many distributors will not sell leaded solder to private persons. It is stupid.

author: janoc
author_rank: Super Contributor
timestamp: May 02, 2022, 08:55:51 pm
content: Quote from: tooki on May 02, 2022, 05:48:17 amNot true, at least for Digikey. Digikey ships from the US and there is always custom clearance involved. Depending on the country you are in, you even get charged by UPS (or who they use for shipping/doing the paperwork) for the customs declaration fee, despite no customs being due. It is a royal PITA + about 20€ fee to UPS. I am avoiding Digikey for that reason.Mouser ships from EU warehouses for most things (and indicates where the goods will come from the US/UK if that's the case) so you don't get these issues but not Digikey.

author: tooki
author_rank: Super Contributor
timestamp: May 03, 2022, 06:05:03 am
content: At work, we order from Digi-Key and Mouser regularly and never, ever run into that issue. If you’re getting charged on delivery, then you didn’t select a shipping and currency combination that produces DDP incoterms for your country.Note that if you last ordered many years ago, it changes. Both Mouser and Digi-Key have expanded their DDP availability over the years.You’re absolutely wrong about Mouser shipping from “EU warehouses” because, like Digi-Key, Mouser only maintains a single warehouse, and it’s in USA.The one that works the way you describe (with both EU and US warehouses) is Farnell.

author: 2N3055
author_rank: Super Contributor
timestamp: May 03, 2022, 07:26:22 am
content: Quote from: tooki on May 03, 2022, 06:05:03 amThat probably depends on the country. To Croatia, Digikey only offered Carriage Paid To (CPT) last time, a month or so ago.That means I did have to pay customs clearing and duties..Mouser sends DDP and it just comes to my door, but I do get EU invoice from their EU subsidiary.Maybe Switzerland has different customs regime with USA...?

author: tooki
author_rank: Super Contributor
timestamp: May 03, 2022, 07:58:07 am
content: It definitely depends on the country, absolutely.I don’t think it has anything to do with any customs treaties. Digi-Key and Mouser (and Farnell) have been expanding their DDP offerings over the years. At least with Digi-Key, it’s very easy to see which incoterms apply, since they’re shown in the country/currency/language switcher.Switzerland was already DDP from Digi-Key when Swiss authorities enacted a law requiring foreign shops that sell over CHF100K/year to consumers in Switzerland to collect Swiss VAT and hand it over to the tax authority. Since they have to calculate the applicable Swiss VAT in order to collect it, and the fact that as long as no items with special customs restrictions are involved, VAT isallthe delivery companies/post were collecting anyway (plus their fees for the “service”), this had the effect of eliminating many of the surprise bills, since it’s effectively requiring DDP incoterms for consumers.

author: strawberry
author_rank: Super Contributor
timestamp: May 03, 2022, 04:54:57 pm
content: Quote from: janoc on May 01, 2022, 09:48:54 amcase bending and thermal expansion will crack any solder on PCB

author: janoc
author_rank: Super Contributor
timestamp: May 03, 2022, 08:23:58 pm
content: Quote from: strawberry on May 03, 2022, 04:54:57 pmSure, but there is a difference in how long that will take. Those mixed alloys take significantly less stress for it to happen.

author: Spectrum
author_rank: Regular Contributor
timestamp: May 03, 2022, 08:55:02 pm
content: Quote from: 2N3055 on May 03, 2022, 07:26:22 amWonder Croatia, Supercountry... I would like to live there

author: 2N3055
author_rank: Super Contributor
timestamp: May 03, 2022, 10:34:57 pm
content: Quote from: Spectrum on May 03, 2022, 08:55:02 pmGlad you like it so much... But it is far from perfect when you live here....Nice nevertheless..

author: Haenk
author_rank: Super Contributor
timestamp: May 04, 2022, 12:18:12 pm
content: I'd really use leaded solder for this type of repair.60/40 is still available on ebay. Or (just a random search result):https://elw-elektronik.com/Or Farnell:https://de.farnell.com/c/werkzeuge-werkstattbedarf/lottechnik/lotdraht-lotzinn?lotlegierung=60-40-sn-pb

author: JohanH
author_rank: Frequent Contributor
timestamp: May 04, 2022, 12:44:37 pm
content: I've bought Cynel leaded solder on Ebay. It is Polish and good quality. Also smells good

author: T3sl4co1l
author_rank: Super Contributor
timestamp: May 04, 2022, 04:14:39 pm
content: Metallurgically speaking, the only downside is the extended mushy phase: the eutectic fraction (at Sn63) always freezes at 183°C (minus a few points from the Cu, Ag, etc. that may be present), while the Sn-rich phase freezes somewhere between there and 230°C. (Think of it as dissolving excess Sn in a solvent of SnPb: as it cools, eventually it hits saturation and crystallizes out.)The mushy phase isn't a problem in and of itself, but it has two annoying downsides:1. The long temperature span gives plenty of time for crystal growth; the deposit is rough or matte. It's hard to inspect versus cold or fractured joints.2. There's almost no strength until the eutectic phase begins to freeze. So you can easily nudge the joint, maybe not even see it (because it just looks like any other chalky/bumpy joint), but now it's weakened, or broken entirely.Which is why we prefer eutectic, whether Sn63 (or close to it i.e. 60/40), or SAC305 or whatever. The joint freezes fairly suddenly, making it more reliable in the presence of vibration (shaky hands, bumpy ovens, etc.)Note that Ag and Cu dissolve to only a few percent, lowering the MP only very slightly, to their respective eutectic points (or the combination thereof). The biggest downside to lead-free is the high working temperature. (The second biggest is tin whisker formation; or, really, since high-temp tolerant fiberglass, plastics etc. are the norm these days, the temperature isn't really such a problem, but this one still can be!)Note that tin whisker formation is suppressed for >10% Pb I think it is, so it might well be better to use a dirty joint, than a poor lead-free alloy that's prone to whiskering. (Just don't shake it as it cools..!)Which, not sure offhand what the latest science is on whisker formation, with respect to hand soldering practices. For reflow it's going to be, get the correct alloy, use the correct temp profile, and that's about it, what more can you do anyway. But for hand soldering I don't know. There's always the old NASA docs discussing it, but, well, those are old, there's a bit more we know now but I don't know that it's been summarized into best practices, or where. And also, NASA is aerospace, they can (and do) just soak everything in lead and the problem  goes away.(I.e. mainly when they can't, as for tin plating in crevices, hermetically sealed cans, etc.)Tim

author: nightfire
author_rank: Frequent Contributor
timestamp: May 04, 2022, 07:07:34 pm
content: Got my hands on some 500g of old stuff from private: "a.g. typ as" solder, Sn60PbCu2 zh, F-SW32 4,5%According to some forum entries I found, it could be Alpha Grillo as manufacturer, and that stuff is reported to mabe some people happy regarding workability.Of course, there are some signs of age and long storage, but some oxidation of the solder can be wiped, I guess ;-)

author: Ian.M
author_rank: Super Contributor
timestamp: May 04, 2022, 07:27:31 pm
content: Quote from: nightfire on May 04, 2022, 07:07:34 pmYou've got the nice copper loaded solder alloy. Its a bit harder and stronger than the regular stuff and doesn't erode fine copper wires or the copper core of soldering iron bits.If its grossly oxidized, before use, pull it through a green pan-scourer wetted with IPA then wipe with kitchen paper wetted with IPA till it no longer leaves a mark. If its only moderately oxidized, you can skip the pan-scourer. Don't clean more than you intend to use in a week or two as the abraded and degreased surface deteriorates faster.

author: magic
author_rank: Super Contributor
timestamp: May 04, 2022, 08:18:00 pm
content: RoHS applies to commercial products, the reason why big businesses don't want to sell you that stuff is some relatively recent REACH idiocy IIRC.The hint is "big": many smaller shops still didn't get the memo or pretend that they didn't. I have no problems getting 60/40 in any quantity at hobbyist friendly shops here. Look for brand name stuff and avoid no-name solder from China, some of it stinks like you wouldn't believe

author: BreakingOhmsLaw
author_rank: Frequent Contributor
timestamp: May 05, 2022, 08:19:18 pm
content: Getting leaded solder in Germany is easy. Just go on ebay and useSn60Pb40as a search term.That said, if the unit was made with leaded solder, definately use leaded solder.to repair it.Another tip from an old time T&M restorer:Buy yourself a chunk of bismuth. You can get a 100g chunk for less than €10 on ebay.It is really helpful when removing old ICs from boards. Just scrape some chips off with pocket knife. Melt the old solder joint and feed some bismuth into it. It will drop the melting point of that joint significantly and make desoldering a lot easier. You can just contaminate all joints in a DIP package with bismuth and use a hot air gun set to 170°C to melt all joints at once without melting the adjacent ones. Makes for super easy desoldering without cutting the leads from the package. For most people, 100g of bismuth is a lifetime supply.Remove the contaminated solder with wick before resoldering.I also highly recommend the japanese SS-02 solder sucker.https://www.engineertools-jp.com/ss02It has a replaceable silicon nozzle that really seals around through-holes and cleans them out perfectly on the first try.

author: magic
author_rank: Super Contributor
timestamp: May 05, 2022, 08:28:49 pm
content: There are also solder suckers with heated metal tips.I have never used one but I'm tempted to try. Very cheap, like simple unregulated irons.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: May 06, 2022, 02:05:53 am
content: The cheaper desoldering irons I think aren't very good... maybe not even worthwhile.Have used a no-name temp controlled kind, but which the tip is just a block of metal sitting on a thin metal nozzle, like, what kind of heat transfer is this? It takes forever to heat up, and doesn't have much power in use. It's alsoexcessivelyhot even at the lowest setting, so it oxidizes rapidly, exacerbating its thermal shortcomings.Have also used a top-of-the-line Hakko one, it was in a 3-in-1 unit with iron and hot air. The replaceable-cartridge kind, integrated tip and sensor, direct heated or however it is they make 'em, just happens to be hollow with a vacuum behind it. Keep that baby tinned and it'll suck out anything.Other than that, I feel I've had better luck with just a regular Soldapult(R) or similar. Sealing is overrated, you can just hold it near the joint (with the iron still held in place) and let it rip, it's surprisingly good suction.I suppose for a teeny one like that (finger sized? dang!), getting a good seal is much more important, and a silicone tip is very reasonable.(Related: in contrast to the no-name desoldering gun, the no-name hot air machines seem... okay. I wouldn't saygood, but practical, sure. Mine, the internal wiring is almost certainly of inferior gauge, and the motor is rather noisy, like, I wonder how long it'll even last. But the temp control is good enough, and it makes heat like it says.)Tim

author: tooki
author_rank: Super Contributor
timestamp: May 06, 2022, 04:50:02 am
content: Quote from: magic on May 05, 2022, 08:28:49 pmI haven’t tried those, but my hunch is that they’re not that much better than a solder sucker. The thing that makes true desoldering systems great is thecontinuousvacuum, which lets you first clear the hole of solder, then cool down the joint while keeping the pin in motion so it can’t resolder itself to the wall of a plated hole.

author: slbender
author_rank: Regular Contributor
timestamp: May 06, 2022, 06:28:37 pm
content: I currently have about nine or ten types of rosin core solder for sale in very small quantities (like 8’ or 12’) on eBay, everything from 60/40, 63/37, 60/36/4Ag., 62/36/2Ag., 96.3/3.7Ag., both leaded and unleaded, in diameters from 0.01 to 0.031 inch. The problem is…. how do you know the formula of the solder used in a particular piece that may have been wave soldered 30 years ago, so it’s often a crapshoot.Stevenel57

author: Ian.M
author_rank: Super Contributor
timestamp: May 06, 2022, 07:52:59 pm
content: You don't know. However 30 years ago is 1992, definitely pre-ROHS, so you can bet its a Sn/Pb alloy, and as I posted above, they are fairly tolerant to moderate shifts in their composition due to mixing, so the only remaining issue is to identify the presence of any silver plated ceramic parts which would require the use of a Sn/Pb/Ag alloy.The problem date range is the first decade of this millennium, when in most industries manufacturers were transitioning to Pb-free. After that, unless it falls under one of the increasingly rare exemptions, you can be reasonably confident its Pb-free and will need to be reworked with a Pb-free alloy. Due to high Sn alloys sensitivity to departures from their nominal composition, it is prudent to remove as much as possible of the old solder before resoldering the joint.If in doubt, remove a sample of solder from one or more joints, streak it on the white unglazed back of a ceramic tile and use a lead testing kit, available from any big-box hardware store to determine whether the solder on the board board is Pb-free or is Sn/Pb. Note false positives and false negatives are possible so the first time you use any brand of testing kit, test a streak of a silver loaded Pb-free solder and a streak of known Sn/Pb solder to verify the kit functions as expected. If you test the Pb-free streak first, you can usually get away with only one swab.

author: Spectrum
author_rank: Regular Contributor
timestamp: May 07, 2022, 06:51:56 pm
content: All mental masturbation, I think...The new lead-free alloy does not improve connections, the old lead-free alloy does. Whenever possible, replacing a solder with an old leaded alloy definitely improves the pcb

author: tooki
author_rank: Super Contributor
timestamp: May 08, 2022, 02:53:33 pm
content: Quote from: Spectrum on May 07, 2022, 06:51:56 pmJust quoting so I can comment that this is nonsense. A board isn’t “improved” by removing lead-free and resoldering with leaded.And what “old” lead-free alloy do you think improves connections?

author: slbender
author_rank: Regular Contributor
timestamp: May 08, 2022, 05:22:54 pm
content: Perhaps the early lead-free was basically tin/silver, while later versions had some Cu and maybe other metals in rather small percentages mixed in, while I am not really sure, maybe that was the difference “Spectrum” was referring to for “old” and “new” lead-free types?Steven

author: T3sl4co1l
author_rank: Super Contributor
timestamp: May 08, 2022, 07:56:03 pm
content: Granted the above language is all subjective, but it's my understanding at least that, properly used, lead-free is better in almost all ways. It's stronger, more conductive, environmentally friendly, and has similar production yield.The main downsides are needing stricter process controls, and almost inevitable whisker formation. Given good alloy, flux, reflow cycle, etc., the latter is only a concern for high-reliability equipment -- lifetimes beyond a decade, say. Which is largely irrelevant to commercial goods, especially the very rapid (couple year) product cycles of things like cellphones. And even for automotive and test equipment, it's not been a problem. There are mitigations, like conformal coating and BGA underfill.The main thing, as I understand it, is it's a differentiator. If your process sucks, your lead-free product will suck much more than with leaded solder. It flows less, it wets less, it's more brittle, it's prone to whisker formation, etc. I say above that it has similar production yield, but mind this is after process optimization, and if you're just running it like it's some old junk, not minding that optimization -- you're more likely to have fallout than otherwise. So you have situations like the infamous Xbox "red ring of death" that was mostly due to cracked ball joints under the CPU. A combination of thermal stress (poor cooling; dirty heatsink, poor airflow?) and poor soldering. (Or I might be badly misremembering the circumstances of this example, I don't know; I didn't read the reports in depth, nor repaired one, and this was a long time ago.) Either one of which could be improved and the problem goes away, at least until much longer time scales where whiskers probably take it out. It's a design issue, a marginal one at that, and just slightly over the edge it seems.So that's just why I wonder about hand soldering best practices, but other than that -- well tuned production line assembly should be fine.I would certainly not go around dosing joints with lead, that don't need it. Indeed that could make things worse, for joints that need the strength, or the higher operating temperature. But most of the time, sure, it won't make things worse. More just the risk of, putting heat into everything, disturbing joints and components, there's more risk of breaking leads or components or pads, shorting between pads, etc.; it's a lot of time spent, for little to no gain, and with a low to modest risk of failure.Tim

author: magic
author_rank: Super Contributor
timestamp: May 09, 2022, 05:28:32 am
content: "It's mostly better except for whisker formation after maybe 10 years but who cares, give it 5 year warranty" doesn't sound encouraging to a hobbyist

author: T3sl4co1l
author_rank: Super Contributor
timestamp: May 09, 2022, 07:02:48 am
content: It is what it is. That covers, what, 95% of production, maybe 99% even? You get 10 years out of something, that's a nice comfy amortization there. It's a bother to fix or replace, but it's a few days of downtime out of thousands, it's pretty good.And for the hobbyist, honestly I don't know that I've made that many projects, that I use on a regular basis 10 years later? Most of my computer hardware, is well, some of it is getting up there, but aside from the daily-use things that also aren't at risk of breaking (like a cellphone), really not a lot. If you're really... (prodigious? precocious?) in your projects, that are also highly practical, and have tons of fine-pitch solder joints in them -- maybe it's a concern? But yeh, not like leaded is too hard to come by, most places, and lead-free is harder to use so I wouldn't recommend it to hobbyists anyway.Tim

author: magic
author_rank: Super Contributor
timestamp: May 09, 2022, 01:12:20 pm
content: Well, if you repair equipment which is already 30 years old, then, maybe...

author: tooki
author_rank: Super Contributor
timestamp: May 09, 2022, 04:37:25 pm
content: Quote from: T3sl4co1l on May 08, 2022, 07:56:03 pmI thought that, contrary to the widespread concerns, tin whisker formation hasn’t proven to be anywhere close to the problem it was predicted to be, and that nearly all instances grow out of pure tin plating on component leads, not from the solder. (My understanding being that it takes only a small amount of something else in the alloy to prevent whisker growth.)

author: T3sl4co1l
author_rank: Super Contributor
timestamp: May 09, 2022, 06:10:37 pm
content: What I recall is, it's still a thing, just not as fast with correct alloy/treatment (there's also the difference between electroplated vs. annealed tin; thermal history matters, internal stresses, etc.). And with just a little alloy, it's enough to frustrate it so that it takes decades rather than years or even months(!) to reach dangerous levels. Along with this, I recall comparisons of micrographs contrasting sharp prisms of extruded material vs. lumpy growths. Couldn't tell you what doc that was from -- let's say I'm about 90% on this, wouldn't mind seeing a few more references (especially, like I said earlier, anything applicable to hand soldering).Tim

author: Spectrum
author_rank: Regular Contributor
timestamp: May 09, 2022, 07:31:07 pm
content: Sorry guys,I did a mistake that made confusionQuote from: Spectrum on May 07, 2022, 06:51:56 pmThe lead-free alloy does not improve connections, the old leaded alloy (60/40) does. Whenever possible, replacing a solder with an old leaded alloy definitely improves the pcb. The lead-free alloy is better for health, but not for connections. IMHO

author: tooki
author_rank: Super Contributor
timestamp: May 10, 2022, 10:53:54 am
content: Just to be clear, I wasn’t saying that just your claim about lead-free solder improving a board is nonsense, I was saying the entire post is nonsense. Leaded solder won’t “improve” a PCB or the connections on it.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: May 10, 2022, 11:08:09 am
content: Strictly speaking, in the EU leaded solder can only be sold to "professional" users due to REACH legislation.Not tried Farnell but I had to open a credit account at Rapid to get round this

author: Spectrum
author_rank: Regular Contributor
timestamp: May 10, 2022, 01:04:15 pm
content: Quote from: tooki on May 10, 2022, 10:53:54 amSwitzerland is another planet, no interactions with the rest of the world...

author: magic
author_rank: Super Contributor
timestamp: May 10, 2022, 01:46:45 pm
content: Quote from: tooki on May 10, 2022, 10:53:54 amTin whiskers won't improve it either.You just love being contrarian