Materials/Metals and alloys/Collections
Low-melting metals and solders
low-melting-metals-and-soldersAbout low-melting metals and solders
Low-melting metals and solders (tin, lead, bismuth, indium, cadmium, antimony, SAC305, tin-lead, Wood's metal, galinstan, babbitt): melting range, density and strength with sources.
These metals and alloys melt at low temperatures. They are used to join electronics, seal vacuum and cryogenic systems, make bearings and act as fusible links.
Lead-free solders and fusible alloys differ in melting range, creep and toxicity, so each page states the composition and the hazard.
At a glance
- Highest density: Lead (Pb) reaches 11.3 g/cm³. Lowest: Tin (Sn) starts at 5.77 g/cm³. (16 of 16 grades have a sourced value.)
- Highest melting point: Pb alloys reaches 1,078 °C. Lowest: Galinstan (GaInSn) starts at -19 °C. (16 of 16 grades have a sourced value.)
- Highest electrical resistivity: Bismuth reaches 0.0000013 Ω·m. Lowest: Indium starts at 8.8e-8 Ω·m. (11 of 16 grades have a sourced value.)
Ranges run across the conditions each source reports (temper, heat treatment, form), measured at room temperature where the source says so.
How they compare
The same measurements for every material in the collection. A range means the grade has values under several conditions; "at least" means the source gives a specified minimum. "no data" means no sourced value yet. For ranked tables, open a benchmark.
| Material | Density | Melting point | Electrical resistivity | Thermal conductivity | Young's modulus | Thermal expansion |
|---|---|---|---|---|---|---|
| Tin (Sn)low-melting solder and coating metal | 5.77 to 7.31 g/cm³ | 232 °C | 1.3e-7 Ω·m | 66.6 W/(m·K) | 49.9 to 50 GPa | 22 ppm/K |
| Lead (Pb)dense soft metal (radiation shielding, solder, battery plates) | 11.3 g/cm³ | 328 °C | 2.1e-7 Ω·m | 35 W/(m·K) | no data | 28.9 ppm/K |
| Bismuthlow-melting alloy metal and lead-free substitute | 9.78 to 9.8 g/cm³ | 271 °C | 0.0000013 Ω·m | 8 W/(m·K) | 32 GPa | 13.4 ppm/K |
| Indiumsoft low-melting metal for indium tin oxide coatings, solders, seals and bump bonds | 7.3 to 7.31 g/cm³ | 157 °C | 8.8e-8 Ω·m | 82 W/(m·K) | 10.6 to 11 GPa | 32.1 ppm/K |
| Cadmium (Cd)battery electrode (nickel-cadmium cells) and corrosion-protective plating | 8.69 g/cm³ | 321 °C | no data | 97 W/(m·K) | 50 GPa | 30.8 ppm/K |
| Antimony (Sb)alloying metal for lead battery grids and bearing alloys, and semiconductor dopant | 6.68 to 6.7 g/cm³ | 631 °C | 4.0e-7 Ω·m | 24 W/(m·K) | 54.7 to 55 GPa | 11 ppm/K |
| Antimonial lead (Pb-Sb)hard lead alloy (battery grids, radiation-shielding and ammunition uses) | 6.68 g/cm³ | 630 °C | no data | no data | no data | no data |
| Tin-lead solder (SnPb)low-melting solder alloy for electronics assembly | 8.4 to 8.5 g/cm³ | 183 to 191 °C | 1.5e-7 Ω·m | 49 W/(m·K) | no data | no data |
| SAC305 solderlead-free solder alloy | 7.35 g/cm³ | 217 to 218 °C | 1.3e-7 Ω·m | 61 W/(m·K) | 6.9 GPa | 21 ppm/K |
| Wood's metal (-)low-melting fusible alloy (about 70 °C, bismuth-lead-tin-cadmium) | 10.2 g/cm³ | 69.9 to 70 °C | no data | no data | 12.7 GPa | no data |
| Rose's metal, Newton's metal, Field's metal (-)low-melting fusible alloys (about 62 to 138 °C, bismuth-based) | 8.56 to 10.4 g/cm³ | 94 to 138 °C | 4.3e-7 Ω·m | 4 W/(m·K) | no data | no data |
| Galinstan (GaInSn)liquid-metal conductor and heat-transfer fluid | 6.44 to 6.49 g/cm³ | -19 to 15.5 °C | no data | 25.4 to 26.4 W/(m·K) | no data | no data |
| Indium-tin and indium-silver solderslow-melting solder and seal alloy (In52Sn48 eutectic, In97Ag3) | 7.3 g/cm³ | 118 to 143 °C | 1.5e-7 Ω·m | 34 W/(m·K) | no data | 20 ppm/K |
| Tin-zinc and tin-bismuth (Sn42Bi58) low-temperature solderslead-free low-melting solder alloys | 7.27 to 8.72 g/cm³ | 138 °C | 1.1e-7 Ω·m | 61 W/(m·K) | no data | 15 to 21 ppm/K |
| Sn-Sb-Cusoft bearing-lining alloy | 6.68 to 7.39 g/cm³ | 232 to 630 °C | no data | no data | 52 GPa | no data |
| Pb alloyslead-bearing solders (Pb-Sn-Ag, Pb-Ag-Sn, Pb-Sn-Sb), a lead-bismuth eutectic coolant alloy, and lead selenide | 8.1 to 8.5 g/cm³ | 179 to 1,078 °C | 1.2e-7 to 1.5e-7 Ω·m | 49 to 50 W/(m·K) | no data | no data |
What these materials are made of
Composition by weight, as printed in the sources for each grade (the first constituents listed).
| Material | Main constituents |
|---|---|
| Tin (Sn) | Sn 100.0% |
| Lead (Pb) | Pb 100.0% |
| Bismuth | Bi 100.0% |
| Indium | In 100.0% |
| Cadmium (Cd) | Cd 100.0% |
| Antimony (Sb) | Sb 100.0% |
| Tin-lead solder (SnPb) | Sn 63% · Pb 37% |
| SAC305 solder | Sn 96.5% · Ag 3% · Cu 0.5% |
| Wood's metal (-) | Bi 50% · Pb 26.7% · Sn 13.3% · Cd 10% |
| Rose's metal, Newton's metal, Field's metal (-) | Bi 50% · Pb 25% · Sn 25% |
| Galinstan (GaInSn) | Ga 68.5% · In 21.5% · Sn 10% |
| Tin-zinc and tin-bismuth (Sn42Bi58) low-temperature solders | Sn 91% · Zn 9% · Sn 42% · Bi 58% |
| Sn-Sb-Cu | Sn 89% · Sb 7.5% · Cu 3.5% |
| Pb alloys | Sn 62% · Pb 36% · Ag 2% |
Where they are used
| Use | Grades |
|---|---|
| Solder | Tin (Sn), Sn-Sb-Cu |
| Bearing metals and bronze and brass alloys | Tin (Sn) |
| Printed circuit boards of mobile phones (lead in solder, measured in boards from 30 mobile phones and 30 smartphones) | Lead (Pb) |
| Tin-lead solder and tin-lead plated finishes on space electronics (NASA parts policy) | Lead (Pb) |
| Lead-acid batteries: starting-lighting-ignition (SLI), standby power for computer and telecommunications networks, and motive power | Lead (Pb) |
| Bismuth-tellurium-oxide alloy film paste for semiconductor devices | Bismuth |
| Fusible alloys: fire-sprinkler triggers and holding devices for lens grinding | Bismuth |
| Hall thruster propellant (ground development, not flown) | Bismuth |
| Indium tin oxide (ITO) transparent conductive coatings in flat-panel displays | Indium |
| Indium phosphide substrates, lasers and photodetectors for fibre-optic networks | Indium |
| Indium bump bonds that join detector arrays to silicon readout chips (far-infrared detector model) | Indium |
| Nickel-cadmium (NiCd) batteries | Cadmium (Cd) |
| Experimental negative-limited, non-gassing nickel-cadmium cells (development, not flight hardware) | Cadmium (Cd) |
| Cadmium telluride (CdTe) thin-film solar panels | Cadmium (Cd) |
| Antimonial lead grids for lead-acid storage batteries | Antimony (Sb) |
| High-purity antimony for semiconductor devices | Antimony (Sb) |
When each grade fits
| Material | Best for | Weakest at |
|---|---|---|
| Tin (Sn) | Low-melting solder and coatings: melting point 231.9 °C and 66.8 W/(m·K) thermal conductivity in high-purity pellets | Hardness and cold stability: Mohs hardness 1.5 to 1.8, and a transformation to grey tin at 13.2 °C that the sources read give no rate for |
| Lead (Pb) | Compact radiation shielding per volume, and tin-lead solder and finishes that resist tin whiskers (NASA requires at least 3% Pb in tin finishes unless a mitigation is approved) | Toxicity (reproductive toxicant, no known safe blood level per WHO), softness (Young's modulus 16 GPa) and mass; regulation has removed it from most consumer electronics |
| Bismuth | Lead-free low-melting alloys and solders: melting point 271.3 °C and density 9.78 g/cm3, with no lead content | Heat conduction and supply: 8 W/(m·K) thermal conductivity (WebElements), and China produced 88 % of world output in 2025 (USGS) |
| Indium | Soft, low-melting metal for seals, solders and bonds: melting point 156.6 degC and ductile enough to form a wire O-ring (NASA) | Strength and cost: tensile strength of 2.6 to 4.5 MPa in the supplier foil, and a 2025 U.S. price of about 370 dollars per kg (USGS) |
| Cadmium (Cd) | Corrosion-resistant electrodeposited coatings on steel, where salt-fog protection was the reason it was chosen (NASA tested it against zinc-nickel) | Health: fatal if inhaled and suspected of causing cancer, and USGS reports substitutes for it in batteries, plating and pigments. Also weak in salt fog once a coating is unsealed (corrosion after 240 hours in NASA's test) |
| Antimony (Sb) | Hardening lead for battery grids and bearing alloys, and flame-retardant antimony oxides | Brittleness and toxicity: Mohs hardness 3 to 3.3, and dust and stibine gas that are hazardous to people |
| Antimonial lead (Pb-Sb) | Lead-acid battery grids that need strength and good castability from a small antimony addition, and a recycling chain that already exists (USGS: secondary antimony comes from spent lead-acid batteries) | Antimony leaches out of the positive grid, which raises gassing, water loss and self-discharge; lead is a reproductive toxicant with no known safe blood lead level (WHO), which limits handling and disposal |
| Tin-lead solder (SnPb) | Soldering of electronic assemblies where a single, low melting point and a long track record matter more than RoHS compliance (the Sn60/Pb40 sheet says it is restricted to professional use) | Lead toxicity and regulatory limits (the Sn60/Pb40 sheet says it cannot be sold to private consumers), and low tensile strength and creep resistance compared with lead-free alloys |
| SAC305 solder | Lead-free electronics soldering that needs the most widely documented Sn-Ag-Cu composition, at a melting range of 217 to 220 °C (Indium, Henkel) | Strength and creep: tensile strength of 29.7 to 39.58 MPa across two datasheets, and creep and stress relaxation during thermal cycling (SMTA 2025) |
| Wood's metal (-) | Low-melting fusible links, plugs and holding fixtures, where the alloy must melt near 70 °C (Wikipedia lists fusible links in sprinkler heads and fusible plugs in boilers) | Toxicity: it contains cadmium and lead, and the sources read call its fumes toxic. Few physical data were found: no thermal conductivity, specific heat or corrosion value for the alloy was found in any source read |
| Rose's metal, Newton's metal, Field's metal (-) | Low-temperature fusible releases and heat-transfer baths. Rose's metal is used as a heat-transfer medium in heating baths, and Newton's metal was proposed as easily shaped radiotherapy shielding | Field's metal is costly because indium is expensive. Lead-bearing alloys carry lead toxicity, and few physical or corrosion data were found for the solid alloys |
| Galinstan (GaInSn) | Liquid-metal heat transfer and conduction at or above -19 C, such as a liquid-metal microchannel heat sink or a stretchable conductor, where the alloy has to stay liquid and metallic | Oxide film and aluminium: the oxide skin plugs narrow passages, and the introduction of one source reports corrosivity to aluminium with no rate or test |
| Indium-tin and indium-silver solders | Soft, low-melting joints and seals where the joint must melt near 118 degC (indium-tin) or 143 degC (In97Ag3) and strength matters less than a low melting point | Strength: tensile strength of about 12 MPa for the In/Sn rod, and no strength value is printed for In97Ag3 |
| Tin-zinc and tin-bismuth (Sn42Bi58) low-temperature solders | Low-temperature soldering of heat-sensitive electronics. Sn-Bi suits second-solder reflow at 138 °C, and Sn-Zn suits aluminium-to-copper joints that need a 199 °C eutectic (Kapp, AIM) | Sn-Bi is brittle under mechanical shock and drop, and Sn-Zn corrodes in chloride and leaves flux residue that is slightly corrosive (iNEMI, Brunel, Kapp) |
| Sn-Sb-Cu | Thin plain-bearing linings that must tolerate repeated loading: Wikipedia says combustion engines use tin-based babbitt because it withstands cyclic loading | Strength and temperature: a solidus of 241 degC, a Brinell hardness of 24.5 and 42.1 MPa compressive yield. Tin pest and antimony toxicity add cold and handling limits. |
| Pb alloys | Solder joints that need a single, defined melting point and a high-temperature joint (the Pb-Ag-Sn alloy melts at 309 degC), where RoHS compliance is not required | Lead toxicity and the regulatory limits that follow from it, and the lack of a sourced lead-bismuth density or melting point in this profile; pure-tin finishes that replace these solders grow tin whiskers |
Materials
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