Lead-Free Solder Wire 0.25mm 100gr Sn99.3Cu0.7 Cynel

Lead-Free Solder Wire 0.25mm 100gr Sn99.3Cu0.7 Cynel

The Lead-Free Solder Wire 0.25mm 100gr Sn99.3Cu0.7 Cynel is a soft solder wire built on the Sn99.3Cu0.7 alloy (99.3% tin, 0.7% copper) with an integrated SW26 flux core. It melts at 227 °C and contains no lead, so it meets the requirements of the RoHS directive. In Cyprus this material is commonly called kalai and the soldering iron itself chafkia.

The 0.25 mm diameter makes it an ultra-fine solder wire, well suited to precision work on SMD components, fine-pitch ICs and mobile-phone repairs. The 100 g reel covers occasional use, education and small projects.

Key features

• Sn99.3Cu0.7 alloy: 99.3% Tin (Sn) / 0.7% Copper (Cu) — lead-free, to ISO 9453.
• 227 °C melting point: predictable behaviour and steady flow at a tip temperature of 320–360 °C (up to 400 °C on nickel-plated parts).
• Integrated SW26 flux: strips oxides as you solder — no separate paste or liquid flux needed for everyday work.
• 0.25 mm diameter: at 0.25 mm the wire deposits a minimal amount of alloy per pass, so you avoid bridging between densely spaced pads.
• 100 g (0.1 kg) reel: smooth, snag-free feed for occasional use, education and small projects.
• RoHS compliant: lead content max. 0.07% under Directive 2011/65/EU — suitable for products placed on the EU market.
• Cynel quality: Polish-made solder wire with consistent flux content along the whole reel.

Where it is used

• SMD soldering and rework
• Phone, laptop and small-device repair
• Fine-pitch ICs and small-pitch connectors
• Precision bench work under magnification

Which diameter to choose

The rule of thumb is simple: match the wire diameter to the width of the pad or conductor you are soldering. Wire that is too thin forces repeated passes on heavy work; wire that is too thick bridges pads on fine work.

Technical specifications

What's in the box

• 1 × reel of Cynel Sn99.3Cu0.7 solder wire
• Wire diameter: 0.25 mm
• Net alloy weight: 100 g (0.1 kg)
• Flux is inside the wire core — no separate flux container is included

Usage tips

Frequently asked questions

Will it work with the soldering iron I already own?
Yes. Solder wire is a consumable and works with any iron that reaches 320–360 °C (up to 400 °C on nickel-plated parts). For lead-free alloys a temperature-controlled iron of at least 60 W is recommended, especially on large metal masses.

Do I need separate flux (paste or liquid)?
For everyday work, no: the SW26 flux is built into the core of the wire and is released the moment the alloy melts. Extra flux only helps on oxidised surfaces, during desoldering or for SMD rework.

Do the joints need cleaning afterwards?
SW26 flux residue is classified ROL1 to J-STD-004 and is not corrosive under normal conditions, so it can usually be left in place. If you want a clean look or plan to apply conformal coating, remove it with isopropyl alcohol and a brush.

Why do the joints look dull rather than shiny?
That is normal. Sn99.3Cu0.7 lead-free alloys naturally produce a matte or slightly grainy surface. It is not a cold joint — what matters is the shape: a smooth fillet that wets both the pad and the lead.

Is it RoHS compliant?
Yes. The Sn99.3Cu0.7 alloy has a maximum lead content of 0.07% and meets Directive 2011/65/EU, so it is suitable for products placed on the EU market.

Can I use it over existing leaded solder?
Mechanically yes, but mixing the two alloys creates an intermediate melting point and a less reliable joint. When repairing an older board, remove the old solder first with desoldering braid or a pump.

How much solder do I need?
A 100 g reel comfortably covers a hobby project or occasional repairs, 250 g is the regular bench size, while 500 g and 1 kg reels suit service departments and production runs where changing reels costs time.

Supplied by Antoniadis Electronics-Educational Ltd, a supplier of electronic components, tools and STEM educational products. Manufacturer: Cynel Unipress, Poland.