Soft Solder Alloy Properties Chart

When comparing soft solder alloys, the composition and melting interval are a useful first screen. This chart lists selected alloy designations from one manufacturer and shows the reported solidus and liquidus temperatures. It is not a soldering-temperature schedule or a regulatory-compliance list. Confirm the exact product, flux, process, and application before selecting an alloy.

Soft solder alloy composition and melting range

Solidus, liquidus, and eutectic alloys

The solidus is the temperature at which melting begins; the liquidus is the temperature at which the alloy is fully liquid. Between the two, a non-eutectic alloy is in a mixed solid-and-liquid state. A eutectic alloy has one stated melting point, so the table shows the same value for both fields.

These temperatures describe the alloy itself. They are not a recommended iron-tip temperature, solder-pot setting, preheat target, or reflow profile. Actual process temperatures depend on the joint, component, heat transfer, flux, and the manufacturer’s application guidance.

Read the composition carefully

The composition column uses the manufacturer’s alloy designation format. It identifies the listed elements and their nominal proportions; it does not certify a particular production lot. The “lead shown” column reports only whether lead appears in that published composition. It does not establish that an alloy meets a particular definition of lead-free or complies with RoHS, REACH, or other market rules.

For example, the listed Sn63/Pb37 alloy has an equal solidus and liquidus at 183 °C in the manufacturer’s table. SAC305 is listed with a solidus of 217 °C and a liquidus of 220 °C. Those two examples have different melting behavior and must not be treated as interchangeable simply because both are used as solder alloys.

Choosing an alloy for a real joint

Start with the maximum process temperature the parts can tolerate, then check the service temperature and mechanical requirements of the finished joint. Confirm whether the alloy is compatible with the base metals and flux, and whether its ductility, creep behavior, electrical properties, and corrosion resistance suit the application.

Lead content is only one selection factor. A composition without lead listed may still require a compliance review for other restricted elements or product rules. For electronics, plumbing, food-contact equipment, medical devices, or regulated products, use the applicable standards and product declarations rather than inferring compliance from an alloy name.

Common mistakes

Do not confuse melting range with working temperature. The process must account for joint geometry and heating conditions. Do not assume that a single listed temperature means a broad safe operating range; for a eutectic alloy it means the manufacturer reports a single melting point.

Do not substitute an alloy from this chart for a qualified joining procedure. Check the current product datasheet, safety data sheet, and application-specific instructions. If the assembly is safety-critical or regulated, obtain review from the responsible materials or joining engineer.

Source and method

Alloy names, listed compositions, and melting temperatures are from Indium Corporation’s public solder-alloy reference. This article includes selected soft solder entries and excludes the page’s liquid-metal, gold, and brazing products. Product names and composition values should be checked against the current manufacturer’s datasheet before use.