Solder Opinions?

[MyHeadHz]

To adipic acid, or not to Adipic acid?  Does it even matter?  Backstory below.

I need some new solder, and in one of Dave's videos, he recommended...

1. 63/37 tin lead solder (for the one melting temp), and added silver if you want
2. diameter .5mm or smaller- the thin stuff, for the ability to do SMD and have more control
3. multicore brand (now loctite/henkel- should be same stuff).  A quality brand with more than 1 core of flux (most are 3-core)

I spent a while surfing on amazon, ebay, google, etc.  There was a lot of mismatched product info and models.  :/  I eventually found that digikey's search saved me a hell of a lot of time, and was very easy to use.  It also lists all versions of the products.  My search so far had narrowed it down to these products based on that.

I narrowed it down a bit more on personal preferences to part numbers 386851]https://www.digikey.com/product-detail/en/multicore/386851/82-129-ND/2498927]386851 and 450314.  The descriptions on digikey didn't explain the difference, though.  Only the MSDS sheet linked showed a difference: 450314 has .1-1% Adipic acid.  Apparently it helps break up the oxides, presumably allowing for improved overall soldering performance, while still being a no-clean solution-- though I still plan to clean after soldering.  The model with the acid (450314/MM01054) was not available on the bigger retailers like amazon, though it was available on digikey (the best total cost I found was at prempro).

[KL27x]

If you plan to clean it, anyway, you may want to consider a rosin based flux. Many of the no-clean solders require uncommon solvents to adequately remove. Trying to remove the residue with common household solvents/cleaners can just make things much worse. In a way, you ought to think of no-clean fluxes as "do not clean" fluxes. For most home users, there is very little benefit to using no-clean fluxes. (Not all no-cleans are the same. Some are very similar to rosin, just with synthetic resin in place of rosin. But if you buy rosin/R/RMA/RA, it's a narrowly-defined known commodity. This is partly because of military-instituted standards going back to the 60's or so. No clean is a free-for-all designation where proprietary formulas and profit are chased to the max; some of these fluxes are designed for more specific processes/applications. If you do not want to read the datasheet/MSDS* or chat with a manufacturer rep, it is perhaps wise to stay away from them).

As for gauge? Everyone has an opinion. Guys I work with love micro thin solder and pointy tips. I only design with SSOP/QFN for IC, and 0603 favored but down to 0201 when necessary (usually for rework/repair). I hand solder a lot of these small SMD components. I mostly use 0.063" thick solderwire. The most common size sold by volume/weight per year is probably 0.032"

*To even understand what you're reading, you will need some familiarity with industry (arbitrary, non-scientific, perhaps intentionally-obfuscating) lingo.

[GreyWoolfe]

I use Kester 44 63/37, .031".  I've done some basic smd soldering with it. After years of using 60/40, I like using eutectic solder.  If I need extra flux, MG Chemicals 835 RMA flux in either a squeeze bottle with a needle or a nail polish type bottle with brush.

[drussell]

The long and the short of it is that if you're doing more than one specific task, you probably could really use more than one kind (chemical make-up) and diameter size in your arsenal. In general, some of the physically smaller, thinner stuff will likely be more versatile in random, general use because it is easier to feed in a bit extra on a large joint than try to put a tiny, tiny blob on from a large diameter spool.

Eventually, however, you will find that you will really need multiple sizes of multiple different compositions to do "everything" optimally.  A good suggestion is probably to just start collecting what you really need and is most useful to you at a given time for a given type of project and then plan on continuing to add to your selection over time as needed.

If there was one, true, perfect solder it would be the only one sold. 

Unfortunately, it isn't nearly that simple. 

[EddyK59]

Rosin flux requires no cleaning. Its mild acidity is not corrosive.

You might want to clean a board, say, of slighty sticky residue with Isopropyl Alcohol, but with rosin flux it's not necessary to in order to preserve the integrity of the joint.

Flux described as "water clean" *must* be cleaned because the more aggressive acids are corrosive and will slowly degrade the joints.

[musicamex]

Hi, I just discovered this forum and thought I'd contribute some soldering tips.

I have been building and repairing tube amps for many years.  Since the 60's.  For several years I have used Kester#44  63-37 .025dia.  I twist it with a drill and vise in bundles of 2 and 3 strands at about 10 feet at a time. Then i coil the 3 different sizes around a magic marker or other appropriate sized cylinder and put them into small prescription bottles with a hole drilled in the cap.  This allows me to have an easy to hold dispenser for 3 sizes at each of my 3 soldering stations from the same bulk solder source.  For pcb stuff, [I don't do SMT or hot air repairs] the single strand works best.  For bigger terminals and chassis or pot ground connections i like the 2 and 3 strand twists. They also hold paste flux better. I push them through a drilled hole in the lid of the common 2 oz flat flux containers to pick up flux. Many paste fluxes work well for clean or new joints.

For tough to solder joints, vintage stranded wire or old pots [some of the guitars and amps that I work on are 50 or more yrs old] i use Clophane liquid in a needle dispenser bottle or Oatey 95 tinning flux in a syringe with a large dia dispenser tip. Both allow precise application of just enough flux.  Less is more.  Despite the label saying "Not for electrical use", I find that joints primed with Oatey 95 and soldered with kester 44 look good and test perfectly sound with an ohm meter after 10 or more years.  I bet many of you have seen humongous globs of solder on the backs of pots, usually because of lack of skill or often not getting the solder/flux to flow onto the pot surface when tinning it, pre solder.  With just a tiny prep of both the wire and back of the pot with #95, the subsequent #44 flows like water.  Cleaning with undiluted ethyl or isopropyl alcohol afterward might be useful to remove flux residue, but the flux in the Kester 44 seems to displace the # 95 flux from the actual electrical interface. ALSO  I feel the # 95 prevents overheating components by allowing the rapid low temp tinning and subsequent soldering of a joint.  And I always apply the first tiny dab of solder TO THE INTERFACE OF THE IRON AND JOINT BEING SOLDERED.  This initiates heat transfer.  Then apply the solder to the joint so it flows toward the iron. I have watched Youtube videos where "experts" overheat components being soldered while waiting WAY TOO LONG for a small tip to heat the point being soldered and the solder to "flow" from the extreme other side of a joint. This isn't Voodoo or charming a snake out of a basket.  Heat the joint and wet solder it as quickly as possible and use some solder to speed up the heat transfer.  Otherwise You wind up with melted wire insulation, cooked capacitors, and even pots that dont work right.  If it's a pot in a vintage guitar or amp, you DON'T want to damage it.

IMHO, lawyers write caveats and warnings and some self proclaimed "experts" teach improperly, so that if we all heeded without common sense, they would have us idly  worrying instead of working or applying our skills or hobby motivated interests.  Work smart with an open mind.  A little pinch of something forbidden by lawyers/"experts" can produce scientific magic. So take what i just wrote with a proverbial grain of salt too.

Riffin