Melting range is one of the first filters in solder selection, but it is not the only one. Wetting, mechanical behavior, flux compatibility and compliance must also be reviewed. The chart below summarizes common directions from the current Vibgyor solder range.
| Alloy | Approx. melting | Typical format | Common direction |
|---|---|---|---|
| Sn42Bi58 | 138°C | Paste | Low-temperature SMT where component limits require it |
| Sn63Pb37 | 183°C | Wire, bar, paste | Permitted precision electronics and repair |
| Sn60Pb40 | 183–190°C | Wire, bar | Permitted general electronics and service work |
| Sn96.5Ag3.0Cu0.5 | 217°C | Wire, bar, paste | High-reliability lead-free electronics |
| Sn99Ag0.3Cu0.7 | 221°C | Wire, bar, paste | Balanced lead-free process direction |
| Sn99.3Cu0.7 | 227°C | Wire, bar | General lead-free electronics |
| Sn99.95 | 232°C | Bar | Plating, tinning and solder-bath adjustment |
What the numbers mean in practice
A higher melting range usually requires more thermal energy in reflow, wave soldering or hand soldering. That can affect component stress, cycle time and equipment settings. A lower melting point can reduce thermal demand, but the alloy still needs to meet mechanical and compliance requirements.
Eutectic and near-eutectic meaning
Sn63Pb37 is commonly described as eutectic at approximately 183°C. Eutectic behavior can support a narrow melting transition, but it does not automatically make the alloy suitable for every product. Lead restrictions and customer requirements still apply.
Low-temperature paste
Sn42Bi58 is commonly used around 138°C for low-temperature SMT. It can help with temperature-sensitive assemblies, but brittleness, thermal performance and process compatibility should be checked. Use the paste supplier’s approved profile and data sheet.
Confirm the approved data
The temperatures above are approximate planning values. Always request the current product data sheet and validate the alloy with a sample, because composition tolerances, flux and measurement methods can affect the approved specification.
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