60% leaded solder - Page 1
Forum section: electronics / general

author: MarkoGVA
author_rank: Contributor
timestamp: May 24, 2023, 09:27:47 pm
content: Hi guys,Has anyone had experience with 60% leaded solder?How is the joint conductivity, strength, flexibility and longevity?Thanks!

author: thm_w
author_rank: Super Contributor
timestamp: May 24, 2023, 10:16:08 pm
content: https://www.eevblog.com/forum/beginners/the-best-solder-for-electronics/https://www.eevblog.com/forum/reviews/characteristics-of-modern-solder-mixtures-(leadfree)/https://www.raypcb.com/60_40-vs-63_37-solder/

author: jpanhalt
author_rank: Super Contributor
timestamp: May 24, 2023, 10:49:56 pm
content: The OP is asking about 60% lead. "60/40" and "63/37 solders are tin rich (i.e., 60% tin and 63% tin, respectively).

author: thm_w
author_rank: Super Contributor
timestamp: May 24, 2023, 11:51:29 pm
content: Quote from: jpanhalt on May 24, 2023, 10:49:56 pmSo 40/60, which is not for electrical use.MarkoGVA: why do you want to use it? Is it to save money buying normal solder?"The 40/60 solder is a general purpose solder used for non electrical applications. It is used for applications in the sheet metal, stained glass, galvanized gutters, and radiator repair industries."https://www.practicalmachinist.com/forum/threads/any-solder-experts-out-there-uses-of-40-60-tin-lead-solder.343770/

author: T3sl4co1l
author_rank: Super Contributor
timestamp: May 25, 2023, 09:41:02 am
content: About that much:https://www.matweb.com/search/DataSheet.aspx?MatGUID=c5c8586626b9403b968f05a752b88a7b&ckck=1Compare with Sn63:https://www.matweb.com/search/DataSheet.aspx?MatGUID=9e382af924de44ffb4eb42027ca1436dOr SAC305:https://www.matweb.com/search/DataSheet.aspx?MatGUID=b1d03850d9854c24b25226694c6beed2These sheets aren't particularly detailed, so you might want to find more properties elsewhere (I'm a bit shocked honestly that it took some minutes of searching to find these on Matweb).The critical problem for soldering is the mushy range, between solidus (fully solid, eutectic freezes) and liquidus (fully dissolved). The joint can move as it solidifies, displacing the still-forming matrix and making a weak or failed joint much more likely (akin to a "cold solder joint", but while it's still hot). The slow crytallization of the lead phase also gives large (visible) crystals on the surface -- a dull finish.The big difference between leaded and lead-free is the insane ductility of leaded, given enough time and/or elevated temperature. It tends to be stretchy over time. Whereas lead-free joints are known to crack under enough / repeated stress; and give or take alloy and process, may produce tin whisker growth as well; but conversely, it tends to stay in place rather than creep around. And the silver and copper make it a bit stronger. (You can get silver, copper or antimony bearing leaded solder too, it's just more expensive, and rare that you need the added strength.)Tim

author: MarkoGVA
author_rank: Contributor
timestamp: May 25, 2023, 11:51:46 am
content: Thanks guys for this comprehensive answer!So, what I can conclude is that 60% leaded solder:1. Takes generally higher temperature to melt (wider range) which electronic components do not like,2. Takes longer to solidify which can create "bubbles" and cold-solder joints, and3. Fumes are more toxic.This is enough for me! I will return it to the store (which was the construction materials store anyway).I bought it because it seemed cheaper and I though that since some lead seems to be good, more lead will be betterThanks!

author: Circlotron
author_rank: Super Contributor
timestamp: May 25, 2023, 12:10:02 pm
content: What I find amazing is that an alloy of lead and tin melts at a lower temperature than either of it's constituents. 63/37 being the lowest AFAIK.

author: nimish
author_rank: Regular Contributor
timestamp: May 25, 2023, 12:54:05 pm
content: Quote from: MarkoGVA on May 25, 2023, 11:51:46 amBuy 63/37 or a eutectic lead free solder (Sn100C?). That means it has a single melting point vs a range of semi molten ones which makes bad joints much harder to do. You will thank yourself later and the cost difference is negligible.

author: jpanhalt
author_rank: Super Contributor
timestamp: May 25, 2023, 01:43:27 pm
content: Quote from: Circlotron on May 25, 2023, 12:10:02 pmThat effect is quite common in chemistry. An "alloy" of salt and water melts at a lower temperature than either component alone. Of course, that is not an exact analogy, but a higher (and sharper) melting point is often used as a sign of purity for crystalline compounds.

author: 2N3055
author_rank: Super Contributor
timestamp: May 25, 2023, 01:46:02 pm
content: Quote from: MarkoGVA on May 25, 2023, 11:51:46 amThere are no fumes..1749 °C is boiling point of lead..

author: mariush
author_rank: Super Contributor
timestamp: May 25, 2023, 03:07:37 pm
content: Fumes are burnt flux ... lead free solders often have much stronger fluxes because due to the higher melting temperature of solder (237c) people use higher tip temperature which can burn away the flux before it gets a chance to workSO yeah, lead free solders can have more harmful fluxes for your lungs compared to lead based solders.I also vote with 63/37 or with 62/36/2 (2% silver) but this silver one is often 50%-100% more expensive at same quantity.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: May 25, 2023, 04:13:29 pm
content: Generally speaking, mixtures either have a higher or lower melting point; you can imagine the reduction as an entropic effect (more atoms/molecules to choose from = more possible disorder = encourages disordered states i.e. liquid/gas), though it's more complex than that of course. Or higher melting points, when a compound is formed (pieces fit together, bonding occurs, higher energy levels are required to break the crystal). Sometimes the effects compete and a compound might be formed anyway, with a lower melting point, or which indeed decomposes into another mixture above some temperature (peritectic).Since atoms are so diverse, there are relatively few examples of the middle case: solid solutions, where any amount of the two (or more) components can mix while giving the same crystal structure. (Or liquids that are miscible, but that happens more often than for solids. Gas mixtures are always miscible.) Cu-Ni is an example, at least at higher temperatures. It's no accident that Cu and Ni atoms are very similar, being neighbors on the periodic table, having similar atomic and metallic properties (lots of 2+ compounds, similar reduction potential), and often substitute for each other in compounds. (Not all metals are miscible: indeed Pb and Al hardly mix, until considerably above their melting points. (Solid) Fe is minutely soluble in liquid Pb, and needless to say, not in solid form either, hence its excellence for plating solder iron tips.)A solid solution may still have a nonuniform melting point, and may also have a eutectic I think, but the difference in temperature (or the change in composition between solid/liquid phases) tends to be minor.So, it's quite common that mixtures have a lower melting point, forming a eutectic (lowest melting) mixture at some percentage. A mix of salts is more effective (faster melting and to lower temperatures) than pure salt at melting water ice, for example. (There's also some chemistry in play, as molecules/ions count per unit: sugar has about half the melting power of sodium chloride (which dissociates into separate Na+ and Cl- ions), and calcium or magnesium chloride do even better (making three ions: one Ca or Mg(2+) and two Cl-). There's of course other effects in play, say if we consider light molecules that resemble water, like alcohols; hence ethanol or glycol mixtures have quite low melting points.)Quote from: 2N3055 on May 25, 2023, 01:46:02 pm"Fumes" could be understood as dusts, I suppose -- which is the main way lead becomes ingested. Inhale dust, it sticks to your respiratory lining, mucus flows into your mouth, you involuntarily swallow it, boom digestion happens.AFAIK, very little lead dust is produced when rosin is heated, but handling alone can be an issue (the alloy is so soft, it rubs off on your fingers), and cleaning say with a brush can liberate metal, oxide, and contaminated rosin dusts.It's an extremely minor difference to have 60 vs. 37% lead in such an environment -- the difference from just washing your hands before lunch every other day. To justify avoiding wearing a mask, and gloves or washing regularly, and a handful of other simple hygiene steps -- you'd have to go to much lower lead concentrations, like <1%. Which lead-free solder is quite effective at, in that respect.(For those curious, and IIRC -- always double check with a reference to be sure, don't take my word for it -- lead absorption is highest in childhood, mainly while laying down bone growth. Something like ~50% dietary absorption for ages under 18. It drops to ~10% in adulthood, so either takes five times the concentration, or five times the exposure duration, to have the same effect. But that'seasilywithin the time scale of a working career, so the same exposure is no less of a health risk overall!)Tim

author: Infraviolet
author_rank: Super Contributor
timestamp: May 25, 2023, 06:53:16 pm
content: On the topic of 60/40 vs 63/37, the difference between the behaviour of the almost eutectic one and the truly eutectic one is small enough that exactly what sort of flux is used and how high quality a brand of solder is used will vastly outweigh any difference that 60/40 vs 63/37 might give.