RA vs No-Clean Flux?

[yami759]

Hello there. Now that I'm almost done with this awful Radio Shack roll of solder, I've been looking to buy a good, quality roll. I found these two. One uses Rosin Activated flux (RA) and one uses a "No-Clean" flux. The No-clean one, however, uses the 63/37 ratio rather than 60/40 as the RA one does. Is it right to assume that the rosin flux will be better at cleaning oxidation off of components? If not, which should I buy? I had found this old post from the forums, but I did not see it as leaning towards one side or the other (other than saying not to use water-soluble flux). Also, while I am here, does anyone know of anywhere better to buy solder other than Digikey? Thank you in advance!

[Fsck]

correct. the RA flux will remove oxidation far more easily.

for brand spanking new components, the type of flux doesn't really matter in terms of efficacy and it tends to be relegated to personal preference.

if you're reworking crusty components then RA will storm past the weaker no-clean flux.

60/40 has a plastic range while 63/37 is eutectic, personally I'm a fan of the eutectic 63/37

I personally just stick with kester 44 (RA) solder but I use kester 951 no-clean flux additionally.

[kingofkya]

Yeah RA for old or/and large wires.

No-Clean for most pcb work.


It is handy to have both types in flux pen form though, for occasional use.

Also the 63/37 is mutch more forgiving

[nanofrog]

From least to most active in rosin; R (rosin), RMA (rosin, mildly active), and RA (rosin, active).

If you decide on a no-clean, read the data sheet for the particulars. Multicore's Crystal 502 for example, is a mildly active no-clean. So equivalent to an RMA product in regard to flux activity (ability to remove oxidation). There are more active formulations (more likely to find with lead-free alloys IIRC).

For hobbyist use (parts & PCB's sit around for years), RMA would be the minimum I'd recommend, and on occasion, RA would be more appropriate to have on hand (or equivalent NC). Best to keep a little of both types of flux on hand if at all possible (pens, small bottles, ...).

Do note, that you need to be careful if mixing flux types. Some no-clean formulations will mix with rosin based, but not all (read the datasheet). Personally, I find the safest solution is to stick with rosin based products. Water soluble should never be mixed with anything else.

What I tend to prefer for general purpose work:

• Alloy = 63/37
• Diameter = 0.020" - 0.025"
• Flux core = RA
• Core size/flux amount in solder wire = 3.3% (sometimes called 66 core or P3)

Liquid Flux: I prefer RMA for most applications, RA if it's really oxidized.

RA core = Kester 44 (worth consideration IMHO if you don't want to keep multiple flux types of solder on hand).
RMA core = Kester 285.

IIRC, Multicore cut down on their lead alloy SKU's, so you may not find an equivalent rosin core product, but rather an NC flux core instead.

Hobbyist friendly size of RA flux = MG Chemicals Rosin 835P (they also make a 1L size). Buying this way is cheaper than the disposable pens. I put it in a Bonkote BON-102 brush pen, and also in a needle bottle.

RMA is harder to find this way, and what you do find, is riskier (repackaged into smaller containers by eBay sellers). Kester 186-18 is my favorite (example; not tried this seller). But it's possible to do this successfully, and worst case, isn't that expensive if it's not genuine. SRA solder sells flux in hobbyist sizes too for their refillable pens (refill bottle is $9.00 for 50ml). CML supply also repackages Kester into their own Tekline brand of pens (CML is worth bookmarking, as they do this with Kester's solder paste as well & it's genuine).

[marshallh]

Stick with the RA solder.
If you do ever use anything no-clean or water soluble, download the datasheets and carefully inspect them to see how you are expected to use it. Some types are quite corrosive if not fully activated.