PCB assembly usually requires more than one solder format. Solder paste may be used for SMT reflow, solder bars for wave soldering and wire for rework, selective soldering or repair. The right mix depends on the board, components, equipment and quality requirements.
Match the format to the process
| Process | Typical material | Key selection points |
|---|---|---|
| SMT reflow | Solder paste | Powder size, flux chemistry, melting range, stencil life |
| Wave soldering | Solder bar | Alloy, pot volume, copper level, dross behavior |
| Hand soldering / rework | Solder wire | Diameter, flux core, melting range, operator process |
| Plating / tinning | Pure tin or selected bar alloy | Purity, bath chemistry and contamination control |
Keep the alloy direction consistent
Review paste, wire and bar alloys as one material system. Mixed alloy directions can affect melting behavior and process control, especially during rework or selective touch-up. Confirm the approved alloy for each process step and document the permitted substitutions.
Review quality from the joint backward
Wetting, solder-ball formation, residue, bridging, spatter, joint brightness and thermal fatigue all provide useful feedback. A material sample should be evaluated with the actual board finish, component mix and equipment settings rather than judged from appearance alone.
Plan the production package
For repeat orders, define spool or bar packing, label data, batch identification, shelf-life requirements and required documents. This reduces receiving errors and makes it easier to trace material through the production process.
Review the full PCB assembly material set.
Send the board process, alloy direction, equipment and estimated volume.