Last updated: October 2026

For most hobby electronics, the best solder is a 63/37 tin-lead wire with a rosin flux core, such as Kester 44 or MG Chemicals 4880 series: it melts at a single point (183 °C) and is the easiest alloy to learn with. If you need or prefer lead-free, SAC305 (such as MG Chemicals 4900) is the mainstream choice, but it melts at 217 to 220 °C, so your iron needs more heat. Add a flux pen for rework, and ventilate whichever you choose.

How we picked: compiled from manufacturer specifications, published prices and owner feedback patterns. We have not tested these tools ourselves. Our method.

Quick picks

  • Best all-round leaded solder: Kester 44, Sn63Pb37, rosin-activated core.
  • Best alternative leaded solder: MG Chemicals 4880 series, Sn63Pb37, RA-like core, five published diameters.
  • Best no-clean leaded solder: MG Chemicals 4860 series, Sn63Pb37, no-clean resin core.
  • Best lead-free solder: MG Chemicals 4900, SAC305 with a no-clean core.
  • Best flux pen for rework: MG Chemicals 835-P rosin flux pen, rated for leaded and lead-free solder.

Alloys: 63/37 vs 60/40 vs lead-free

Melting points below come from Kester’s solder alloy temperature chart.

AlloyCommon nameMelting point or range (Kester)What the maker says
Sn63Pb3763/37183 °C (361 °F)MG Chemicals: eutectic, so liquidus equals solidus, which gives a sharp melting and solidification point and makes it “one of the easiest solders to work with”
Sn60Pb4060/40183 to 190 °C (361 to 374 °F)MG Chemicals: melts at slightly higher temperatures and over a wider range than 63/37
Sn62Pb36Ag262/36/2179 °C (354 °F)Silver-bearing leaded alloy; Kester lists it alongside 63/37 for tip temperatures
Sn96.5Ag3Cu0.5SAC305217 to 220 °C (423 to 428 °F)MG Chemicals: “the predominant lead-free alloy composition”
Sn99.3Cu0.7Sn99 / SnCu227 °C (441 °F)MG Chemicals 4901 uses this eutectic tin-copper alloy

63/37: the easiest to learn

A eutectic alloy goes straight from solid to liquid at one temperature. MG Chemicals points to that sharp transition as the reason 63/37 is easy to work with.

60/40: common, slightly harder

60/40 melts over a 183 to 190 °C range rather than at a single point, so it passes through a partly solid stage as it cools. It is widely used, but if both are available at a similar price, 63/37’s sharp melting point is the reason makers like MG Chemicals describe it as the easier alloy.

Lead-free SAC305: hotter, and required in some settings

SAC305 melts roughly 35 °C higher than 63/37 per Kester’s chart, so expect to need a hotter tip. MG Chemicals also notes its SAC305 wire is about 14% longer by weight than leaded solder wire. Choose lead-free if your workplace, school or product requires it, or if you prefer to keep lead off your bench.

Wire diameter

Thinner wire gives finer control on small pads; thicker wire feeds more solder into large joints and wires.

  • Kester lists 0.031 in as its standard diameter for most applications on the 44 datasheet (printed there as 1.00 mm), with wire made from 0.25 to 6.00 mm (0.010 to 0.250 in).
  • MG Chemicals lists its 63/37 RA wire in 0.63 mm (0.025 in), 0.81 mm (0.032 in), 1.01 mm (0.040 in), 1.27 mm (0.050 in) and 1.57 mm (0.062 in).

A diameter around 0.8 mm (0.031 to 0.032 in) is a common middle ground for through-hole kits. Go thinner for fine-pitch SMD work and thicker for heavy wires and connectors.

Flux: rosin, RA and no-clean

Flux cleans oxide from the metal so solder can wet it. Cored wire carries flux inside; flux pens and paste add more when you rework a joint.

Rosin and rosin-activated (RA)

Kester 44 is an activated rosin core classified ROM1 under J-STD-004. Kester says the residue is non-corrosive and non-conductive under normal conditions of use, so many applications leave it on the board. The standard core is “66”, which is 3.3% flux by weight, with 1.1% and 2.2% cores also available.

No-clean

No-clean fluxes leave low or benign residue. MG Chemicals says the residues from its no-clean wire are non-conductive and non-corrosive, so cleaning is not necessary, but it recommends cleaning if the board will be conformal coated, because residue can cause coating problems. Its 4900 SAC305 wire uses a no-clean core classified REL0.

Extra flux for rework

  • MG Chemicals 835-P Rosin Flux Pen: ROM1 rosin flux in a 10 mL pen, for leaded and lead-free solder; MG says residues are non-conductive, non-corrosive and fungus resistant.
  • MG Chemicals no-clean pens: the original 836-P is marked discontinued; MG lists the 836LFNC-P lead-free, no-clean flux pen on the same page.
  • Kester 186: the Kester 44 datasheet names 186 mildly activated rosin flux as a compatible liquid flux for rework, also sold in flux pens.
  • Tacky flux paste: useful for SMD parts and rework, where you need flux to stay in place. Check the product’s J-STD-004 classification and cleaning instructions.

Comparison table

ProductAlloyFlux coreClassificationDiameters (maker)Clean after?
Kester 44Sn63Pb37 (most common), other alloys availableActivated rosin, 3.3% standardROM10.25 to 6.00 mm range; 0.031 in standardOptional in many applications per Kester
MG Chemicals 4880 seriesSn63Pb37RA-likeFlux meets J-STD-004B0.63, 0.81, 1.01, 1.27, 1.57 mmNot stated on the product page
MG Chemicals 4860 seriesSn63Pb37No-clean resinFlux meets J-STD-004B0.81 mm listedNot necessary; clean before conformal coating
MG Chemicals 4890 seriesSn60Pb40RA-likeFlux meets J-STD-004B0.63, 0.81, 1.01, 1.27, 1.57 mmNot stated on the product page
MG Chemicals 4900SAC305 (lead-free)No-clean resinREL00.81 mm listedNot necessary; clean before conformal coating

Prices change often by spool size and diameter, so we have not listed them. Check the current retailer page.

Tip temperature starting points

Kester’s 44 datasheet says tip temperatures for Sn63Pb37 and Sn62Pb36Ag2 are most commonly between 315 and 371 °C (600 to 700 °F). Kester also says to heat both the pad and the component lead first, then apply the wire to the joint, not directly to the iron tip. For lead-free alloys, follow the solder maker’s datasheet, since the melting point is higher.

For irons with enough headroom for lead-free, see best soldering iron. For technique, see how to solder through-hole parts.

Safety notes

These come from Rensselaer Polytechnic Institute’s soldering safety guidelines:

  • Fumes: heating rosin flux releases fumes that irritate the eyes and respiratory system. RPI calls for fume extraction (a fume hood, a filtered extractor, or a snorkel system).
  • Lead: RPI describes lead as a neurotoxin. Wash your hands thoroughly with soap and water after soldering, and do not eat or drink where you solder.
  • Burns: irons run at 600 to 800 °F. Keep the iron in its stand when not in use.

MG Chemicals’ leaded wire pages also carry a California Proposition 65 warning for lead. Kester’s datasheet also says to store cored wire in a dry, non-corrosive environment.

FAQ

Is 63/37 better than 60/40? For learning, yes. 63/37 melts at one temperature (183 °C), while 60/40 melts over 183 to 190 °C, according to Kester’s chart. MG Chemicals calls 63/37 one of the easiest solders to work with.

What is the best solder diameter for electronics? Around 0.8 mm (0.031 to 0.032 in) suits most through-hole work. Kester lists 0.031 in as its standard, and MG Chemicals sells 0.81 mm alongside thinner and thicker sizes.

Do I need to clean flux off? Kester says 44 residue is non-corrosive and non-conductive under normal use. MG Chemicals says no-clean residue does not need cleaning, except before conformal coating.

Why does lead-free solder feel harder to use? SAC305 melts at 217 to 220 °C versus 183 °C for 63/37, according to Kester’s chart, so it needs more heat from the iron.

Does solder go bad? Kester’s datasheet gives cored wire a limited shelf life: two years for alloys over 70% lead and three years for other alloys, stored dry. A dull grey surface is cosmetic, per Kester.

Sources