yet another solder recommendation thread

[hirada]

Hello,

So far I have been a lucky camper. I've had some 40+ years old solder and was happy as could be. Then I've started to look for new one, and things got complicated. Probably, as with varnishes, because the good stuff has long been forbidden.
So I've tried to get an overview, and failed and hence thought, I might as well simply ask for recommendations. Sorry for that, I know, there are already quite a few threads dealing with this, but that did not make is easier. Rather the opposite, as things came up, I never thought about.
Therefore, instead of a general question, my idea has been to specify, what I would use it for. Maybe that makes awnsers less confusing to me.

My profile is rather simple:

- It's for hobby use, so I really dot not care for 63/37 or 60/40.
- Decent solder is probably fine, I do not need the best of the best. No Mundorf or Cardas Voodoo
- Mostly new parts. I do have some early 90ies stuff I want to look into, but that has low priority.
- Through hole and SMD, usually not smaller than 0805 or SOT23. And a little drag soldering. So around 0,02" or 0,50mm2 in size.

- I do not mind leaving some residue, as long at it is purely optical and does not affect quality or reliability [in the long run]. So I would like to able not to having to clean
- I would still like to reserve the option to cleaning using IPA.

In short, I would like to maintain my status quo. Given above rather basic requirements, what would you recommend?

Thanks for your experience

[S. Petrukhin]

https://lcsc.com/product-detail/Soldering-Wires_MECHANIC-C116800_C116800.html
https://lcsc.com/product-detail/Soldering-Wires_MECHANIC-C116802_C116802.html

[helius]

Your requirements—possibility of cleaning with IPA, mostly new parts, and hobby use—mean that you should be using an RMA flux type. This may also be categorized as ROL0. Examples would be Kester 285 and Multicore Crystal 400.

It's for hobby use, so I really dot not care for 63/37 or 60/40.

Does this mean you don't have a preference between Sn60Pb40 or Sn63Pb37, or that you are opposed to working with lead? As for lead-free, SN100C is now off-patent and makes much brighter joints than Sn96.

[bdunham7]

I see no point in skimping just because it is a hobby--just the opposite actually.  If you were burning through 10 rolls a week, it would pay to shop around.  For me, a 1lb roll will last years, so why save $10 if it causes frustration just one time?

For most repairs and some assembly of one-off stuff, I use Kester 44 in .040 (1mm) and .020 (0.5mm).  If I want it clean, it takes a bit of work with 70% IPA and a nylon bristle brush. 

For strong joints in point-to-point wiring and the like (old tube radios, non-PCB connections to plugs/jacks/transformers/etc) I have Kester 44 Silver Sn62Pb36Ag02.  You could probably skip that.

For lead-free repair and all-new very clean fresh-from-Mouser parts assembly I have AIM SN100C Glow Core.  I don't have any Kester 285, which is the recommended Pb solder for new assembly only.

For certain SMT repairs I have some off-brand 63/37 solder paste and some Kester 186 flux in a bottle.  This stuff also works for some difficult non-SMT repairs.

I'm generally pretty happy with that.  I'm no pro, but my work usually looks pretty good and if it doesn't, usually it is because the board was dirty.  I've invested over $100 in just solder and flux and I certainly don't regret it ever. 

[hirada]

Thanks very much for your replies. Sorry for not being able to express myself clearly: I do not care wether it is 60/40 or 63/37, but I do want leaded solder. I just have read discussions about that 3% issue and those differences seem way above my skills.
 
I do not want to be skimpy, that is why I have asked for decent solder. Kester I do have on my screen, especially since it is rather esoteric on this side of the pond, but the type discussions I have come across this far (44 vs. 245 vs. 285) make me a little insecure in this regard. So far,  the 285 seems to be the most appropiate, but digikey lists (at least) two versions of it with roughly a 60% price difference for the  24-6337-9700 and the 24-6337-9702. Both 285 series, both 0,5mm2.

I suppose it is the flux, but those things are what makes choice so difficult and hence this thread.

Multicore 370 in 0,6mm2 seems also be available at digikey for slightly less and is also well regarded here (not sure about the 370series, though). I am however also not opposed to the more traditional Stannol or Felder either. But whatever brand, one drowns in options. Hence this enquiry.

@bdunham7: your are using Kester 44 without cleaning? What I have come across this far suggestes, the 44 is more on the agressive side and could cause issues? Or has this been a blantant misinterpretation on my side?

@Petrukhin: Thanks, but that website does not even list the composition and the datasheet is chinese. I should add, I would like not to buy solder made in china.

[hirada]

Some other issues of confusion, taken from a MG Chemicals datasheet:

https://www.mgchemicals.com/downloads/catalogs/Solder%20products%20catalog%20Web.pdf

MG Chemicals Sn60/Pb40 Leaded Solder uses a classical tin-
to-lead alloy ratio, complemented with an RA flux core, which
results in robust and reliable joints that are highly resistant to
whisker formation. The RA Flux residue is non-corrosive and
non-conductive, and can be left on the board or cleaned with
one of MG’s flux removers. (see page 14)

MG Chemicals No Clean formula uses a synthetically refined,
splatter-proof, resin flux core. It leaves a small amount of post-
soldering residue that is non-conductive and non-corrosive, and
won’t cause electrical shorts.
The No Clean name refers to the fact that the board will             
not be adversely affected if it isn’t cleaned. It does not     
mean there will be no residue

Well, if both fluxes leave residue, that do no harm and can be left on the board, why the two products in first place? And secondly, if the RA refers to special brand style flux removers, does this  imply, no IPA? Or is is just marketing to sell own stuff at premium price?

[bdunham7]

I do not care wether it is 60/40 or 63/37, but I do want leaded solder. I just have read discussions about that 3% issue and those differences seem way above my skills.

Then just always get 63/37 and thank us later.  It is easier to use in some situations, so lack of skill and experience is actually a good reason to insist on it.

@bdunham7: your are using Kester 44 without cleaning? What I have come across this far suggestes, the 44 is more on the agressive side and could cause issues? Or has this been a blantant misinterpretation on my side?

Kester says:

“44″ Flux Residues The question is frequently asked are “44″ flux residues harmful to an assembly.
The “44” flux residues are non-conductive and non-corrosive to temperatures up to 85°C (185°F) and 85%RH as determined by IPC Surface Insulation Resistance (SIR) test method 2.6.3.3. Residue removal would normally be for cosmetic reasons. If the end application of the assembly will be in a heated environment and seeing temperatures of over 185°F, then product specific testing should be performed by the designer/assembler.

I often do clean it, especially since I repair test equipment--so on an oscilloscope front end or DMM input, I will clean everything up to perfection.  On a PSU or a stereo receiver or such, no I wouldn't generally bother.  On those things I do clean, I would clean them regardless of what flux I might use, even Glow Core or other no-clean fluxes.

[helius]

Kester 44 is a RA (rosin, activated) flux, which means it contains activators called "halides" in a significant amount (the amount is in the name: 0.44% halides). These chemicals are generally in the family of alkylamine chloride or bromide. The function of activators is to dissolve oxides on metal surfaces, as would be found on old used parts or assemblies. This is most helpful in rework situations, where the joints may be dirty or oxidized. They are not as conductive or corrosive as zinc chloride (which cannot be used for electronics), but they do present an increased risk of corrosion in some environments if the devices become damp. The rosin in the flux becomes hard and helps to surround the activators, keeping them from leeching out, but if it is not fully heated it may not harden completely.

For these reasons flux with little or no halides is preferred when working new parts. This is called RMA (rosin, mildly activated) or ROL0 (Rosin, low activators, no detectable halides). It is simply less active against oxides but has the same appearance and cleanability. Sometimes this may be labeled as "no clean", but "no clean" is not a flux type. It is a marketing term that refers to barely visible, clear, flux residues. Kester 44 does not generally require cleaning, but since its residues are brownish yellow and obvious it is not "no clean".

In general fluxes labeled "no clean" are clear in color and rather thin (low solids content). This is what makes their residues mostly invisible. This is balanced against their oxide cleaning ability which is usually lower as a result.

One way to compare how different fluxes perform is to read their data on the IPC-TM-650 Copper Wetting test. The greater the spread, the better the flux was able to wet the solder to the surface.

Flux	Area of Spread (mm2)
Crystal 400	210
Crystal 500	290
Kester 44	280
Kester 285	335

From this we see that Kester 285 is very effective on clean copper.

[hirada]

Thanks, those posts were super helpful in helping me finding an appropiate solder. Not just for Kester, but for general understanding.
In case it'll be kester, I'd go for the 44. Yellow/brown residue is fine, that's the way it has to be. As at least I do see I oughta clean. And my flux is selfmade colophony dissolved in white spirit anyway, so thats a perfect fit.

Great help, thanks again everyone!