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Solder Alloy Melting Point Reference (Lead-Free and Leaded)

Solder alloy decides your reflow peak, which components you can use, and which RoHS or exemption rules apply. This reference lists common alloys with composition, solidus and liquidus so buyers and process engineers can compare them quickly.

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Alloy	Composition (by weight)	Solidus (deg C)	Liquidus (deg C)	Lead content	Typical use
Sn63Pb37	63% tin, 37% lead	183	183	Leaded (eutectic)	Hand soldering and exempt leaded assembly
Sn60Pb40	60% tin, 40% lead	183	190	Leaded	General hand and wave soldering in legacy lines
Sn62Pb36Ag2	62% tin, 36% lead, 2% silver	179	179	Leaded (eutectic)	Silver bearing finishes and hybrid parts
SAC305	96.5% tin, 3.0% silver, 0.5% copper	217	220	Lead-free	Most common lead-free reflow and wave alloy
SAC405	95.5% tin, 4.0% silver, 0.5% copper	217	220	Lead-free	Higher silver, used where customers specify it
SAC0307	99.0% tin, 0.3% silver, 0.7% copper	217	228	Lead-free	Lower cost, low silver option
SN100C	99.3% tin, 0.7% copper plus trace nickel	227	227	Lead-free	Wave soldering and selective soldering
Sn99.3Cu0.7	99.3% tin, 0.7% copper	227	227	Lead-free	Wave soldering baths
Sn96.5Ag3.5	96.5% tin, 3.5% silver	221	221	Lead-free	Eutectic tin silver, thermal fatigue sensitive joints
Sn95Sb5	95% tin, 5% antimony	235	240	Lead-free	Higher temperature joints, step soldering
Sn42Bi58	42% tin, 58% bismuth	138	138	Lead-free	Low temperature reflow for heat sensitive parts
Sn91Zn9	91% tin, 9% zinc	198	198	Lead-free	Niche; zinc oxidizes readily in air
In52Sn48	52% indium, 48% tin	118	118	Lead-free	Very low temperature, cryogenic and optical assembly
Pb92.5Sn5Ag2.5	92.5% lead, 5% tin, 2.5% silver	287	296	High lead	High temperature die attach in exempt applications
Au80Sn20	80% gold, 20% tin	280	280	Lead-free	Hermetic packages and laser diode attach

Values are nominal and vary slightly by source and impurity content. Peak reflow temperature is normally set 20 to 40 deg C above liquidus, within the component's maximum body temperature rating. Use the solder paste supplier's profile guidance for production settings.

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How to use the alloy reference

Search an alloy name such as SAC305 and read its melting range. Solidus is where melting begins and liquidus is where the alloy is fully liquid. Use the numbers to sanity check a paste or wire order, to compare lead-free against leaded processes, or to understand why a low temperature alloy was chosen for a heat sensitive part.

Search by alloy name or by temperature use
Compare solidus and liquidus, not just one number
Export the table for supplier specification files

How the numbers relate to your profile

Eutectic alloys such as Sn63Pb37 and Sn99.3Cu0.7 melt at a single temperature, so they flow and solidify cleanly. Non-eutectic alloys have a pasty range between solidus and liquidus. Reflow peak temperature is typically set well above liquidus so that all joints wet, while staying under the lowest maximum body temperature of any component on the board. Lead-free assemblies have a narrower window than leaded ones.

Sourcing and compliance notes

The alloy on a paste, bar or wire label should match the process document and the customer's lead-free requirement. Mixing leaded component finishes with lead-free solder, or the reverse, causes reliability concerns, and some defense and aerospace programs require leaded processes under specific controls. Record the alloy in your ERP item master as an attribute, and keep certificates of analysis with the lot for traceability.

Common mistakes

People often assume SAC305 and SAC405 have very different melting points when both start melting near 217 deg C. Another mistake is using the liquidus as the reflow peak, which leaves no margin for wetting. A third is ordering a low temperature SnBi paste for a board that later sees high service temperatures, where bismuth alloys may creep or embrittle.

Frequently Asked Questions

What is the melting point of SAC305?

SAC305 begins to melt near 217 deg C and is fully liquid around 220 deg C. Reflow peak temperatures are normally set 20 to 40 deg C above that, within the limits of the components.

What is the difference between solidus and liquidus?

Solidus is the temperature at which melting begins and liquidus is the temperature at which the alloy is fully liquid. Between them the alloy is partly solid, and joints should not move in that range.

Why is Sn63Pb37 popular for hand soldering?

It is eutectic, so it melts and freezes at one temperature, and it wets well at a lower temperature than lead-free alloys. Its use is restricted under RoHS except where an exemption applies.

Can I mix lead-free paste with leaded components?

It can be done but creates reliability and process risks, because the joint ends up with mixed metallurgy. Follow your customer's requirements and get process engineering approval.

If solder paste lots and expiry are tracked in spreadsheets, we can connect your ERP and shop floor data to a private agent that answers where each lot was used.

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