Solder

[Excavatoree]

I'm putting this in the "beginner" section, even though I've been soldering for at least 30 years.

I've always used what my employer bought, or, picked out "good old rosin core" solder without giving it much thought.

I was looking today at an online vendor (is there one that advertises here so that I could help Dave out?) and noticed that, for electrical work, there is a great deal of variation, and the price difference is significant.  Is "gee-whiz super duper ultra flux it all dries clear as virgin tears" core solder really worth 50 percent more than "good old rosin core?"

[Bored@Work]

The thing is, if you can solder you might recognize a difference, but you will also be able to just do the job as good with the old stuff than with the new stuff.

In the professional world things have changed due to RoHS and due to increased awareness of allergies possibly caused by rosin flux. However, you can study as many material safety sheets of the new flux types as you like. In the end you'll only know that the manufacturers also don't have the slightest clue how unhealthy their new flux with god knows what kind of shit in it is.

[DJPhil]

I did some marginal research on solder a while back when looking to stock up. The rough outline of what I found follows:

Solder itself comes in dozens of alloys. There's lots out there on lead free vs. leaded solder, so I'll skip that. Suffice it to say that unless you're limited by regulation it tends to be easier to use leaded solder, though preferences vary. Some other alloys surface on occasion for specific applications, like 2% silver, which is meant to be used with components or metals with a silver content to prevent silver leaching and brittle joints over time. The need for one of these alloys is usually rare, though it doesn't hurt to at least skim the details (and the controversy) to know when it's useful. There are some threads to this effect on the forums here. The last major consideration I'll relate is eutectic blends. Eutectic alloys like 63Sn 37Pb have a very small or nonexistent plastic state, so they're less vulnerable to mechanical action while solidifying. In a perfect world this wouldn't be much of an issue, but I've found it useful as I don't have good equipment for fastening everything down when I solder. It still makes good joints when I'm working quick and dirty, so it's what I like best.

Flux is at least as complicated as solder, and differs mainly in how much oxidation it can remove and how easily it can be cleaned. I prefer using flux with strong activation (RA) and stronger solvents, and I use RMA flux for assisting in rework as it's a bit easier to clean with just alcohol.

The only real variable left is how they put the flux in the solder. I use single core 33, which means the cross section is 33% flux and it's all concentrated in a single channel in the center of the strand. You can get it with less (22 and 11), or perhaps more, and it's also sold in multicore with several channels of flux around the center. I'd probably be just as happy with 22, but it's mainly a matter of taste unless you're working with older nasty stuff that needs a lot of flux to deoxidize.

As Dave would say, "Horses for courses", but unless you have specific needs or want to tweak your style I'd say the plain old stuff is just fine. Naturally if you look about you can find passionate arguments about solder just as much as anything. Still, I don't think there's anything that would qualify as awesomely better than classic 60/40 rosin core for general use.

Hope that helps.

[Time]

Anyone ever used low temperature solder?  I have noticed it has a distinctly different odor.  Its almost a sweet smell.  I just used it for something at the time without giving much thought to its properties outside of melting temp.  Is that stuff just a certain type of alloy?  I remember it being quite expensive but I got a free reel of it to try out.  This was back when I used to work for a university based research lab.

[allanw]

I need to get some of that stuff. Desoldering IC's without killing them from heat is basically impossible without low temperature solder. I think the big brand name is ChipQuik but are there any cheaper alternatives?

[DJPhil]

There's so many types of solder out there it's difficult to know which low temperature solder you might mean. It's possible to sort the solders list I linked above by temperature (sort of, the sort's not very smart), after which you could spin through the descriptions and see if you recognize anything. The only low temp application I can think of off the top of my head is the almost pure lead stuff that was once used for BGA balls, though I'm sure that's changed. Certainly there are dozens of other needs for low temp solders, it's just my experience with it is small.

Chip quik is a different beast entirely. It's a gel that contains bismuth, which is sort of the opposite of copper on the thermal conductivity scale. Adding a bit to solder results in molten metal that's very slow to cool. The usual procedure is to lightly goo up each row of pins on a chip, then bead up some fresh solder over top of the goo. The solder at the pins will retain it's head far longer, meaning that you can swipe the iron along each row one final time and just tap the chip out of place, or use a vacuum pickup and lift it right off. It's got a much better chance of salvaging an SMD chip without heat damage than attempting to use just an iron and wick, but you can still cook a chip beyond repair. As far as I'm aware there are no low cost alternatives for chip quik, but it does last quite a while as it doesn't take much to get the job done. Many of the videos on youtube demonstrating chip quik use a lot more gel than necessary.

Hope that helps.

[andyg]

Why would one use low temp solder?

For soldering, most ICs are designed to handle soldering temperatures at the pins. Datasheets often will state a max temp and time allowed on the pins.

Keep in mind lead-free solders have a lot higher melting point than 63/37 lead-tin solder (183 degC) while lead-free can be ~220 degC. That is a considerable difference. Lead-free solders also require higher soldering iron tip temperature.

So it would be safer to use PbSn if possible.

As for re-work, there is no reason to use a lower-temp solder than what is already on pins you are desoldering anyway. As even if you use a 150 degC solder (if it even exists), you still need to heat up the whole joint up to 183 degC to melt the original solder anyway to remove your part.

[sonicj]

Anyone ever used low temperature solder?  I have noticed it has a distinctly different odor.  Its almost a sweet smell.  I just used it for something at the time without giving much thought to its properties outside of melting temp. 

i have some chip quick 63/37. smells kinda like cinnamon. not nearly as purdy as kester though 

despite not smelling nearly as delicious as the CQ eutectic, kester 63/37 44 is my favorite to date.
-sj

[Zero999]

I've heard stories of lead free solder not mixing with leaded solder very well, are they true?

I've only used lead free solder on a couple of occasions, both of them job interviews and I found it harder to work with than leaded.

[andyg]

I've heard stories of lead free solder not mixing with leaded solder very well, are they true?

I've only used lead free solder on a couple of occasions, both of them job interviews and I found it harder to work with than leaded.

That is true, lead-free alloys should not be mixed with lead-tin alloys in a solder joint. The final alloy composition becomes unpredictable and can cause:
- a final alloy with large "mushy" temperature zone which means slow solidification resulting in a possible weak and brittle joint
- undefined intermetallic compounds in the joint, also causing weak and brittle joints

Lead-free is harder to work with compared lead-tin, this is because lead-free alloys have a lot lower wetting capability (the ability to attach itself to something such as a pad or lead) than lead-tin. It is also less reliable, due to issues like tin-whiskers. But for a lot of consumer items, it is an acceptable risk. Lead-free solder is usually banned for high reliablity applications such as military, life-support, space applications for this reason etc.

[Neilm]

Why would one use low temp solder?

The only reason for low temp solder I know are a few rather specialist sensors that can be damaged by high temperatures.

I've heard stories of lead free solder not mixing with leaded solder very well, are they true?

I've only used lead free solder on a couple of occasions, both of them job interviews and I found it harder to work with than leaded.

If regulations require lead free solder then you will get contamination of the lead free items if you use a soldering iron bit that has soldered lead solder. This would mean that your company would be liable to prosecution if found out. Before I get complaints,  I believe that there has been a prosecution of a company who did this - they were a very large multinational whos supplier just changed the solder used not the bits doing the soldering. I don't remember who.

Lead free solder can be a pain to use.  If you are used to leaded solder then you have got used to waiting for a few moments before you solder. When using lead free you have to disapline yourself to wait a few extra moments to allow the pins to get a bit hotter to allow the solder to work. Once you are used to it, soldering with lead free isn't harder than with leaded. (Assuming you have a decent solder)

Neil

[nbritton]

Is Kester 44 a multi-cored flux solder? Dave said in his video to get multi-cored solder. If I bought a 1LB roll for general purpose through hole and SMD work what diameter do you recommend? I was thinking Kester #66/44 63/37 .020" (0.5 mm)?

[helius]

The Multicore solder is a brand name, like Kester or AIM. I think it is the only solder with multiple flux cores.
It's also a European product, so will be more common there than in the US (where Kester is made). Which you use is a personal preference.

#66/44 Sn63Pb37 is a good general purpose electronic solder. 0.020 or 0.031 are both good sizes, depending on whether you do more small joints or more large joints. Sizes that are smaller or larger than either, are more difficult to handle.

[KL27x]

Re low temp solder:
SN43/PB43/BI14  was at one time used by the telecom industry. The 14% bismuth isn't much, but it significantly reduces the melting point.

One reason it is no longer used is because of mechanical strength. The alloy isn't stable, and the individual constituent metals can concentrate funny along shear lines when reflowed, resulting in curiously low shear strength.

If you can find a roll somewhere, it works very well for desoldering large ICs. It not only melts at a lower temp, but the alloy is not eutectic. It takes a fairly long time to completely solidify, and in the meantime, it easily releases ICs. I can use it to desolder ~20-30 pin IC's without changing my soldering iron setting. If you nudge the IC at the right time, the semi solid beads "break" clean off the pads.

[GreyWoolfe]

I use Kester 44 63/37 with a 66 core in .031" and I use it for everything including larger AWG wire.

[JoeN]

i have some chip quick 63/37. smells kinda like cinnamon. not nearly as purdy as kester though 

despite not smelling nearly as delicious as the CQ eutectic, kester 63/37 44 is my favorite to date.  -sj

Stop sniffing the fumes! 

[zapta]

I was looking today at an online vendor (is there one that advertises here so that I could help Dave out?) and noticed that, for electrical work, there is a great deal of variation

Another variation is the quality. A name brand solder and a cheap ebay solder with similar spec can be very different in practice.  Same goes for flux and solder paste.

[nanofrog]

Is Kester 44 a multi-cored flux solder? Dave said in his video to get multi-cored solder.

Kester uses a single flux core, but it works extremely well regardless.  Anything from AIM (American Iron & Metals), Alpha Metals, Indium, MG Chemicals, and Multicore (Loctite/Henkel) are top notch performers as well. At which point the trick is to get the right alloy, flux type, amount of flux, and wire diameter that you need.  Just stay away from the cheap Asian crap on eBay, DX, and so on (genuine Goot is good, but very heavily counterfeited).

You may get more splatter from a single core vs. multiple cores due to larger voids/air bubbles (as it's not divided into multiple cores). The larger the air bubble/void, the bigger the splatter (and increased likelihood the operator ends up getting burnt). Fortunately, it's not as big a concern with smaller diameter wire IME (assuming a reasonable distance of your fingers from the iron's tip).

FWIW, I actually use a hemostat to hold the solder wire, as it help stabilize my hand for better feed control (reduces hand tremor).  And it also happens to reduce getting burnt from splatter as well, as it keeps your fingers farther from the joint.

If I bought a 1LB roll for general purpose through hole and SMD work what diameter do you recommend? I was thinking Kester #66/44 63/37 .020" (0.5 mm)?

No smaller than .020", and no larger than .032" IMHO.

Kester offers .025" as well, and is what I tend to use the most. For larger stuff, you can make a wrap or two around your fingers and twist it into however a larger wire you need (i.e. good for tinning wire, soldering lugs, tabs, and so on).

Also, keeping a small bottle of RA flux on hand is highly useful as well (cheaper than disposable flux pens w/o sacrificing quality). MG Chemicals Rosin 835 comes in small bottles (125ml & 1L), which is handy for hobbyists.  You can find vendors on eBay that repackage Kester flux (i.e. 186 RMA and 951 no-clean), but there's always a risk it's not genuine.

As per dispensing it, you can use needle bottles, brush bottles, dip a brush into a small container, refillable plastic nip pen, .... My preferred method is to use a refillable BonKote BON-102 brush pen (eBay is full of counterfeits, so get it from a distributor if you want one; genuine ones start at $15 per and go up from there <multiple tip shapes available>).

FWIW, All-Spec carries Kester 44 as well so you can put all of it on the same order and save on shipping (good pricing & reasonable shipping fees IME; no affiliation, just a customer). 

[The Magic Rabbit]

I'm still waiting for electrically conductive duct tape. Will fix anything then!

Sent from my XT1039 using Tapatalk

[FrankT]

For my hobby work, I use 0.7mm and 0.35mm.

I find I have so much more control with 0.35mm soldering small pads.  Even "large" pads on the 0802 it is hard to dispense too much.