Best Rosin Core Solder for hand soldering thru-hole components

Thread Starter


Joined Mar 28, 2019
These days... what is the best rosin core solder for hand soldering thru-hole components ?

And what diameter?

Thanks for bringing me up to date.


Joined Mar 30, 2015
Are you sure you want rosin core?

I use SN63/PB37 0.031" or 0.032" mostly. Kester uses 331 flux and Alphametals is noclean (P2).

I have a bottle of mildly activated rosin flux for cases where I want more.


Joined Mar 19, 2019
And for grins and giggles to give a bit of diversity I use this one...

They are all good and Kester is a very well-respected old brand with many options in their product line. Find one that you like that works well for you. But I would choose a Kester lead product.


Joined Mar 19, 2019
0.031 is the largest I regularly use but I also keep some smaller diameters on hand in the tubes for when wanted. They don't get much use...


Joined Jan 27, 2019
I certainly concur with the recommendation of Kester products, and for that matter Alpha as well.

My general advice is:

  • 63Sn/37Pb alloy
  • .031“ diameter for general PCB use
  • No clean flux core
  • Kester or Alpha brand

  • Absolutely avoid RoHS lead-free solder unless you are forced to use it​
  • Avoid activated flux core because you will have to clean the PCB to avoid corrosion​
  • Don’t buy “cheap” solder, it isn‘t even worth what you pay for it​

Additionally, I would suggest you get a solder dispenser stand. Even a very good one from someone like Hakko is not very expensive but it will make life much easier.

Get a flux pen, the Kester 951 no-clean pen would be my choice. It can go a very long way to making reluctant connections, and it won’t get burned off the way the core’s flux will if the solder is left on the tip too long. While “carrying” solder on the iron is not ideal, sometimes if you apply flux to the parts first, putting some solder on the tip and letting it get fully hot before applying it to the joint can wet things that are otherwise very reluctant to take the solder.

I also think the suggestion of having some activated flux on hand is a good one. If you need it, it can be a project saver. I would get the Kester 186 pen which they suggest is equivalent in fluxing action to RA fluxes without corrosive residue.

These pens don’t look cheap but in fact they last a very long time because they apply a thin film of flux which is very effective and efficient.

One more thing is temperature. The manufacturers‘ data sheet will have process information including recommended temperature. I would stick to that. If the solder doesn’t seem to work well at that temperature, it means your iron isn’t maintaining (or reaching) it. Proper calibration with a tip thermometer (knock-offs of the Hakko 191 are cheap and cheerful) and empirical testing to keep the temperature down to the minimum working number taking into account the heater’s capacity and tip’s thermal mass.


Joined Jan 23, 2018
The best solder in my assorted stock, as far as for quickly wetting and sticking, came from Radio Shack many years ago. It has a core of more active flux than other flux core solders I have used.
Certainly the Kester brand catalog will have an equivalent.


Joined Sep 9, 2010
I'm wondering now how I decided on 60/40 instead of 63/37. I know I researched it at the time and convinced myself it was the way to go. Maybe it was cheaper that day? But 63/37 is the eutectic blend and has the lowest (and sharpest) melting point. It makes good sense to use it as the default solder.


Joined Mar 19, 2019
Maybe they were calculating it with a slide-rule back then and rounding it off? It was Richard Feynman who suggested teaching introductory physics using 10m/s^2 instead of 9.8 to help students understand the concepts without tripping over the math.
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Joined Feb 20, 2016
Absolutely avoid RoHS lead-free solder unless you are forced to use it
I recently purchase some rolls of 60/40 solder on Ebay (so probably deserve it).
It turns out they sent me Lead Free!!!
Not happy and they only refunded a small part of the purchase price. Anyone want some Lead free solder???


Joined Jun 30, 2021
I had some 'old' solder lying around that I once used for a PCB board I was building up. Big mistake! Even after trying to clean the board multiple times with Isopropyl alcohol, the board would not work properly. It had stray resistances between parts causing all kinds of problems. I now us no clean, 63/37. The board cleans up very nice and pretty and no issues.
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