Lead-free solder (SAC305)

96.5% tin, 3% silver, 0.5% copper, and the industry default since the RoHS directive took lead out of consumer electronics in 2006. It melts at 217-220 °C, which means hotter irons, more thermal stress on components, and a matt grey finish that is normal rather than a sign of a cold joint. It is also stiffer and less forgiving than leaded solder, which is one reason reflowed BGA joints on early lead-free boards failed under thermal cycling.

Properties

Density

7,380 kg/m³ — 7.38 g/cm³

Melting range

217–220 °C

Tensile strength

40–50 MPa

Young's modulus

50 GPa

Thermal conductivity

58 W/(m·K)

Thermal expansion

21 µm/(m·K)

Floats in water

No

Magnetic

No

What it is used for

• All RoHS-compliant electronics manufacturing
• Reflow and wave soldering
• Consumer product assembly
• Potable water plumbing (as tin-copper or tin-silver)

How it compares

Does it rust?

Lead-free solder (SAC305) does not rust — rust is iron oxide specifically — but it does corrode, forming its own oxide or salts over time.

Is it magnetic?

Lead-free solder (SAC305) is not ferromagnetic. It is often assumed to be because it is a metal, but most metals are not — only iron, nickel, cobalt and a few alloys are attracted to an ordinary magnet.