Solder Diameter Question

[bostonman]

I plan to buy 1lb rolls of 63/37 solder and actually never bought solder before. The rolls I have were given to me years ago and the diameter size is okay. Sometimes I feel the diameter may be too large for 0402 components because one quick jab of solder and I have a bubble of solder that makes a mound on the component end.

Anyway, after using the filters on DigiKey for 63/37 and selecting a 'roll', I narrowed down the 'diameter' sizes for 63/37 and 'flux type'. I found the following sizes (see below) along with the flux type (no clean, no-clean water soluble, rosin activated, rosin mildly activated, and water soluble).

I've always assumed all solder was the same, so I'll use the term 'standard' and believe my 'standard' roll is rosin activated. Should I go with rosin activated or use another type of flux?

As for solder diameter sizes, most likely I just two (or maybe three) sizes to cover most of my soldering jobs. Usually I solder anything from 0402 to through-hole.

My question: which solder diameter sizes are best for covering all the jobs I work on?

Solder diameter sizes I found on DigiKey (in mm):

0.38
0.51
0.61
0.64
0.79
0.81
1.02
1.27
1.57
1.63
3.18

[mariush]

i use no-clean 0.56mm with 2% flux - but i don't solder 0402

stay away from any "water soluble" fluxes.
Rosin Activated (RA) will probably have the strongest flux so would work best with slightly old components, oxidized pads etc the flux will attack surfaces better,  but downside is SOME solders will require you clean the board after soldering (with isopropyl alcohol or flux removers) otherwise the flux may continue to corrode the pads and leads over time. You'll have to read the datasheets, they say if cleaning is required or recommended
 
RMA is rosin, mildy active, it's less strong flux.
No-clean is usually weaker flux but still perfectly fine if the components are relatively new - some no-clean fluxes may be a bit worse for your health, if you inhale the fumes .. but with all soldering it's recommended to have some fan or something move the smoke away from you as it's not good for your lungs.

Note lead free solders usually have quite stronger fluxes due to the higher melting temperature, so no-clean fluxes in them can be particularly hard on your lungs.

In your situation, I'd probably order a smaller spool (250g/500g) of 0.38 for small smd work (with 1-2% flux, and  0.51-0.61 with 2-3% flux for the bigger stuff - you can always cut a piece of solder wire and bend it in two to feed more solder if you have bigger soldering jobs.
I wouldn't get anything bigger than 0.7mm - that's already quite thick.

[jonpaul]

0.032" regular 0.062" think, we use USA made Kester 63/37 with 44 type flux.

Unsure EU/mm equiv

j

[james_s]

When soldering SMT parts I often put the solder on the iron tip and flux on the part rather than feeding solder in the way I do with through hole.

Water soluble flux is great but only for applications where you can easily wash the assembly when you're done assembling. I keep both water soluble and rosin flux as well as solder with each on my bench and choose based on what I'm doing.

[jpanhalt]

For electronics, I use only two sizes: 0.81mm(0.032") and 0.38mm (0.015").  Both Kester 63/37 with #44 flux.  I have heavier gauges for other stuff.   The 0.38mm is used primarily for SMD.

[WattsThat]

For electronics, I use only two sizes: 0.81mm(0.032") and 0.38mm (0.015").  Both Kester 63/37 with #44 flux.  I have heavier gauges for other stuff.   The 0.38mm is used primarily for SMD.

+1 duplication here. That’s been my standard for thirty plus years. Mostly proto builds, some repair.

[loki42]

I only use lead free obviously but 99c / 100c is really nice to solder. For little stuff I just get the thinnest I can and I use no clean only.  I also recommend a flux pen or two as I'm pretty generous with the flux when doing smaller stuff. 

[bostonman]

When soldering SMT parts I often put the solder on the iron tip and flux on the part rather than feeding solder in the way I do with through hole.

I do that too, but (especially when looking a microscope), I'll see way too much get melted onto the tip.

Probably like most of you, my solder jobs vary. It's rare I come across 0402 or find pitch components, but I do come across them and would like to have adequate size solder on hand.

I'll plan to order 0.38mm and 0.81mm since those sizes seem to be the most recommended. I'll also measure the stuff I have since that has been find for most typical jobs such as wire, through-hole, etc...

As for flux types, water soluable, etc... it's always confused me. I think not seeing a comparison chart including the pros and cons has hindered me from retaining them, but mariush did a good job breaking them down in a reply above. The solder I currently have leaves a ton of flux behind and seems nothing I do removes all of it. I've considered buying flux remover spray, but wonder if it's too strong and may damage components.

Unfortunately my solder jobs can be decades old equipment, or brand new components, through-hole, SMT, etc... Then again, I'm not stating anything nobody else deals with.

Am I better off with solder that has less flux and keep a bottle on hand?

[james_s]

Water soluble flux is very easy to clean off which is nice, but it's conductive so you HAVE to clean it off. Rosin fluxes make a sticky mess but generally it's ok to leave them there.

[Nusa]

Am I better off with solder that has less flux and keep a bottle on hand?

Too much flux is not a problem! Too little makes life difficult. Better too much than too little.

You should always have the option to add more flux, so get some. For desoldering stuff where the flux is gone, it's an essential tool. (Or you'll find yourself adding new solder just for the flux that's in it!)

[T3sl4co1l]

I've been working through a couple rolls of Kester #30/245 0.020", which is 63/37 no-clean.  I didn't get that for any particular reason, rather it was cheap on eBay.  (And by "working through", I mean I got three rolls like 10 years ago, and I'm finally on the last one.)  It's a bit less reactive flux than generic types (RMA usually?) but that was easy enough to adjust to.  I do use a little bit more (external) flux than otherwise, I think, which is fine, probably better to be in the habit of doing anyway.

Alloy isn't too important, 60/40 is very common, 63/37 is just a little nicer to use, and add Cu, Ag, Sb, etc. if you need a stronger alloy.

The diameter is a bit small for bulk purposes, but, also easy enough to use some scrap solder blobs and paste flux to handle those cases.  It's plenty fine for SMT.

Actually SMT isn't that big a deal for diameter anyway, as you don't often apply solder wire to the joints, you're often tinning the tip, then the pad or part.  You have three chances to meter the solder: quickly dabbing the wire, knocking/wiping off the excess, and what actually gets into the joint.

Especially with a hot air machine to help out (a crummy one is like $50, why miss out?), all you need is tinning the pads first, extra flux, and hot-air the parts in place.  Solder paste is somewhat a luxury, but also quite affordable and usable.

For stuff like 0402s, personally I prefer hot air, and smaller pads.  Small pads (around IPC-7351B high density) are less prone to tombstoning, and the part centers more strongly.  Even with large pads, I find it's hard to get a soldering iron against both pads at the same time, and it's almost always going to involve too much solder.  A wedge tip does help.  Instead, I've been using hot air, and a fine bent cone tip for touching up pads as needed.

Hot air can be pretty slow (particularly with inner planes), but I find the patience is worth the consistent results, versus the potentially frustrating struggle: whether I've got enough solder on the tip, or held at the right angle against something I can't see, or endlessly fumbling with a tiny chip that wants to float on the solder blob instead of stick to the pads, etc...

Tim

[NorthGuy]

I use 0.5mm for everything. Long time ago I used thicker solders, but I don't use them any more, even for real big stuff. Thinner solder is much easier to work with. 0.38 mm must be similar. I don't think I would feel the difference.

[bostonman]

Attached is a picture of the two rolls I use; both the same diameter. Until now, I didn't realize one was 60/40, and I don't have any reason to keep two rolls at hand since they are both the same. For whatever reason I didn't store one of them with my other stuff.

Anyway, it's 0.031" and the recommended sizes are 0.015" and 0.32" (maybe 0.032" was rounded up or the company rounded down - doesn't matter), so I'll go with those two sizes.

I'm uncertain of what the other numbers on the label mean, but this solder has worked well for years. As I mentioned though, it does seem to leave an abundance of flux behind.

[jpanhalt]

Anyway, it's 0.031" and the recommended sizes are 0.015" and 0.32" (maybe 0.032" was rounded up or the company rounded down - doesn't matter), so I'll go with those two sizes.

0.032 is what you get when converting 0.81mm to inches.  I suspect Kester and others using imperial units properly rounded down.

[mariush]

So if the solder on the left is Kester  then it's this one : https://www.digikey.com/en/products/detail/kester-solder/24-6337-9713/6029

63/37 with RMA flux , 0.031" or 0.79mm ,  flux is 1.1 / 2.2 / 3.3% depending on diameter I guess ... yours probably has 2.2% flux core.

More details about the flux here : https://www.kester.com/DesktopModules/Bring2mind/DMX/API/Entries/Download?Command=Core_Download&EntryId=1018&language=en-US&PortalId=0&TabId=96

The other one is 60/40 with RA (a bit stronger flux than the previous flux) , same 0.031" or 0.79mm ..this one says CORE66 so it's 3.3% flux which is a good amount if you use this solder to repair older stuff, possibly solder quite oxidized pads/leads etc

As this flux is more active, it has a bit lower resistance than the previous one, but still quite high ... in most cases it shouldn't be a problem to leave the flux on the board

More details about flux here : https://www.kester.com/DesktopModules/Bring2mind/DMX/API/Entries/Download?Command=Core_Download&EntryId=1072&language=en-US&PortalId=0&TabId=96

Both solders seem solid to me, no reason why you shouldn't keep using them even though their old. If you feel like it, slide the solder wire through a paper towel you got wet with isopropyl alcohol, to clean the surface of the wire from impurities.... but I don't think it's needed.

You're already used to 0.8mm so what I would suggest is to go for the a lower diameter solder wire, to make it easier with SMD work. Go with 0.38mm or 0.50mm

If you feel like splurging, I'd suggest going with a 62/36/2 (Lead Pb /Tin Sn /Silver Ag) - the extra silver can help with the terminals of some surface mounted components that have silver in them and the solder also looks great, nice and shiny.

$110 62/36/2  RMA flux 0.38mm (0.015" /0.38mm) Kester : https://www.digikey.com/en/products/detail/kester-solder/24-7150-9703/7565173

The version without silver in it is cheaper, at around 80$:

$80 63/37 RMA flux Kester (0.015" / 0.38mm) : https://www.digikey.com/en/products/detail/kester-solder/24-6337-9703/365518

Mouser has a bunch of 100g spools of Chipquick  62/36/2 0.015"/0.38mm with 2.2% no-clean flux if you want to experiment but don't feel like paying $100, the 100g spool is 26$ : https://www2.mouser.com/ProductDetail/Chip-Quik/SMD3SW.015-100g?qs=byeeYqUIh0NIfL1a3TjBHw%3D%3D

They also have 63/37 Kester solder with two different no-clean fluxes and a bit cheaper at around $76

76$ 63/37 0.38mm with 245 no-clean flux 1.1% flux (CORE50) : https://www2.mouser.com/ProductDetail/Kester/24-6337-8806?qs=m5JL4TdtMhzX%2Fa11ySI3lw%3D%3D
94$ 63/37 0.38mm with 275 no-clean flux 1.1% (CORE50) : https://www2.mouser.com/ProductDetail/Kester/24-6337-7604?qs=w3%252Bcv6Flocq%2F0kQMWmm1wA%3D%3D



I like Multicore solder, that's what I use, but Digikey only has 0.81mm or higher it seems...

[MarkL]

If you're looking to do a lot of SMD, and especially 0402, I would look at getting the thinnest solder possible.  Thin solder allows much better control of how much you want to flow into a joint.  Thicker solders tend to pull too much into the joint from surface tension and creates blobs instead of nice fillets.

I use Kester 24-6337-0001, which is Sn63Pb37 with high RA, and is 0.25mm dia.

It can be hard to find in single rolls, but here's one possibility who says they have it in stock (USD $96.05):

  https://www.techni-tool.com/product/488SO837-24-6337-0001

You don't want to use this for thru-hole and other larger surfaces; you'd be feeding it into the joint forever.  Use the other diameters already recommended.

[tooki]

So if the solder on the left is Kester  then it's this one : https://www.digikey.com/en/products/detail/kester-solder/24-6337-9713/6029

63/37 with RMA flux , 0.031" or 0.79mm ,  flux is 1.1 / 2.2 / 3.3% depending on diameter I guess ... yours probably has 2.2% flux core.

No, it’s not dependent on diameter, it’s dependent on the flux percentage code. The one in the photo on the left says “58/285”, which means type 285 flux, and the 58 means 2.2%. (66 means 3.3%, and 50 means 1.1%.) The one on the right, on modern Kester labels, is labeled “#66/44”.

I like Multicore solder, that's what I use, but Digikey only has 0.81mm or higher it seems...

Have you tried Kester before? I’ve used Multicore before, and honestly, the Kester 44 is nicer to work with. (They’re both good. But the Kester is better.) I have yet to find any solder that performs quite as nicely as 63/37 Kester 44.

(Most Multicore products have a Stannol equivalent, thanks to the companies having merged briefly years ago. Here in Europe Stannol is super common, and honestly I just don’t like it. It burns up faster and it spits more.)

[tooki]

Attached is a picture of the two rolls I use; both the same diameter. Until now, I didn't realize one was 60/40, and I don't have any reason to keep two rolls at hand since they are both the same. For whatever reason I didn't store one of them with my other stuff.

They’re the same diameter, but they’re not the same otherwise.

I'm uncertain of what the other numbers on the label mean, but this solder has worked well for years. As I mentioned though, it does seem to leave an abundance of flux behind.

I won’t describe the roll on the right since it’s very old and isn’t formatted like modern ones.

The one on the left:
LOT#: the production batch number
D.O.M.: date of manufacture
SN63PB37: alloy
58/285: 2.2% of type 285 flux
.031: diameter
24-6337-9713: part number (= order code for that combination of alloy, diameter, flux type, flux percentage, and package size)
ANSI-J-STD-006 A: the industry standard to which it is manufactured

The flux codes (which are specific to Kester) are the thing that requires going to the data sheets: the flux percentage codes are “50” for 1.1%, “58” for 2.2%, and “66” for 3.3%. Similarly, the “285” is simply their arbitrary name for that particular flux formulation.

[KG7AMV]

This is what I use .015 mostly. Some times .020 and .031 depends on what Ii am working on.
.010 price went stupid and never returned to normal.

https://gokimco.com/products/kester-24-6337-0007-sn63-pb37-wire-solder-44-activated-rosin-015dia-66-core-1-lb

https://gokimco.com/products/kester-wire-solder-sn63-pb37-44-activated-rosin-020-diameter-66-core-24-6337-0010?

https://gokimco.com/products/kester-24-6337-0027-sn63-pb37-solder-wire-44-rosin-031-diameter-66-core-1-lb

[bostonman]

0.032 is what you get when converting 0.81mm to inches.  I suspect Kester and others using imperial units properly rounded down.

Sorry, I wasn't implying 0.031 and 0.032 was much different. I was just being literal and keeping dimensions the same per the thread.

Also, as someone mentioned, I'm not looking to replace these because they are old. In fact, I have enough left to last for quite some time. I need to buy solder to do work from home and allowed to use it for personal projects too.

From my experience, the size I have seems good. As mentioned (and someone explained), it does leave a large amount of flux behind. Also mentioned, and from personal experience, when doing 0402 components, I tap the solder to the iron and suddenly I have solder the size of a pea; so smaller dimensions would be better.

I'll read the stuff in the links provided and plan to order some soon.

[bostonman]

I've read through the links and stuff in this thread and ready to place an order for solder.

Unfortunately I'm limited to Amazon and DigiKey because it's a work related project that goes through approved venders.

To confirm what I'm buying and clarification, it looks like the four basic types of flux: RA, RMA, No Clean, and water soluble.

Comparing my current rolls and prediction of future needs, RMA seems to be the best choice. Although I may solder new components and no clean is optional for this, using RMA won't harm anything if I use it on new components.

What if I buy a roll of no clean because I plan to solder new components, but I'm doing a repair which means the PCB is old, then RMA would be ideal, correct?

As mentioned, 285 is arbitrary to Kester, but, reading the link provided, it comes in various percentage flux cores. The pictures I provided were said to be 2.2% and I'm finding the amount of flux left behind is quite a bit. Should I go with 50 (1.1%) or will I discover I don't have enough flux for old jobs?

As previously discussed, I plan to buy 60/40 (or 63/37) 0.031" for through-hole and 0.015" for surface mount. I'd like to keep the price per roll under $100, so should I go with Kester 285 1lb roll, 50 (or 58 if I want to stick with 2.2%)? Any other specs I should consider?

Since I already have 0.031" (2.2%), am I better of going with one that has three alloys to get a better bang for the buck, or a no clean for "new" components?

[NorthGuy]

... or a no clean for "new" components?

Unless you're doing production and ease of cleaning is of great concern, go entirely with "no clean". You don't have to clean it. If you want to clean, this can be done with IPA rather easily (and with some fluxes even with water). But even if you don't clean in, or clean it poorly, it may look ugly, but the circuit will still work.

Also, go with higher flux content. You will get better results and easier soldering. It will be flux residue anyway, even if you use sloder with very low flux content. So, if you want it clean you cannot avoid cleaning. Then why would you care how much residue do you have?

If you're doing some sort of re-work, repairs, or prototyping, you'll need external flux anyway and most of the dirt will come from this external flux. Compared to that, whatever comes from the solder is literally nothing.

[bostonman]

Excluding my desire to not wanting the job to look ugly, I was told years ago that flux residue can cause issues in high frequency circuits due to it being resistive. It's rare I work on anything high RF, but I try making the job look good regardless.

Also, until now, I thought flux will corrode over time causing issues which is why I try cleaning as best as I can.

So a 2.2% RMA flux core will be fine?

I never realized solder can involve so much knowledge.

[tooki]

... or a no clean for "new" components?

Unless you're doing production and ease of cleaning is of great concern, go entirely with "no clean". You don't have to clean it. If you want to clean, this can be done with IPA rather easily (and with some fluxes even with water).

It is well documented that no-clean flux residues are often very significantly more difficult to remove than RA/RMA residues. So if you’re planning to clean anyway, get the RA/RMA. Use no-clean if you don’t intend to clean.

Also, until now, I thought flux will corrode over time causing issues which is why I try cleaning as best as I can.

So a 2.2% RMA flux core will be fine?

I never realized solder can involve so much knowledge.

This is but a tiny, tiny glimpse into the world of solder and flux.


Anyhow: You need to distinguish between flux and flux residue, and what form the flux came in, and what soldering process was used…

With few exceptions (expressly sold as no-clean), water soluble fluxes, and their residues, are very corrosive and must be cleaned flawlessly.

Most rosin and no-clean paste/gel/liquid fluxes are corrosive if left on and not heated thoroughly. (Many unheated liquid fluxes are neutral once dry, but applying excessive amounts that can’t dry quickly can result in corrosion.) While wet/pasty, they’re already somewhat active. Then as it heats during soldering, it fully activates. Rosin fluxes then deactivate once cooled. No-clean fluxes deactivate by being neutralized by heating even more. This means it must be heated thoroughly. Thorough heating means reflowing in an oven; hand soldering will not guarantee that all of the flux gets heated enough to neutralize it. (Especially with paste/gel, it’ll melt and flow away to cooler parts of the board, some of it never reaching neutralization temperature.)

Upshot is, when hand soldering using paste/gel fluxes, cleaning is a must. When reflowing, cleaning is optional except with water-soluble. But in no case do you want to apply paste/gel flux and then leave the board unheated for more than a few hours.

The flux cores in solder wire are designed for hand soldering, so no-clean doesn’t need cleaning, nor do most rosin fluxes. (The datasheets tell you whether cleaning is needed.)

I prefer 3+% flux core if possible.

[bostonman]

$80 63/37 RMA flux Kester (0.015" / 0.38mm) : https://www.digikey.com/en/products/detail/kester-solder/24-6337-9703/365518

Am I missing the core size (flux amount) in the description? I see it's RMA, 63/37, 0.38mm, but don't see anything about the core.

The datasheet lists 50,58, and 66 for 1.1%, 2.2%, and 3.3%, but I don't see any associated numbers.