Solder is the metal alloy that forms a bond between other metal pieces, while flux is a cleaning agent used before or during soldering to prepare the metal surface for a strong solder joint.
Here's a more detailed breakdown:
Solder
- Definition: Solder is a fusible metal alloy with a relatively low melting point. It's used to join metallic surfaces together. When heated, solder melts and flows between the surfaces, creating a metallic bond upon cooling.
- Function: To physically and electrically connect two or more metal items. It forms the conductive pathway for electrical signals and provides structural integrity to the joint.
- Composition: Commonly composed of tin and lead (although lead-free solders are increasingly prevalent), as well as other metals such as silver, copper, or indium. The exact composition dictates the melting temperature and other properties.
- Forms: Available in various forms like wire, bars, paste, and preforms.
Flux
- Definition: Flux is a chemical cleaning agent applied to the metal surfaces before or during the soldering process.
- Function:
- Removes Oxidation: Cleans away oxides and other contaminants from the surfaces to be soldered. Oxidation prevents the solder from properly bonding.
- Improves Wetting: Helps the molten solder flow and spread evenly across the metal surfaces, improving the "wetting" action. This creates a stronger and more reliable joint.
- Protects Surfaces: Prevents further oxidation during the heating process.
- Composition: Typically composed of rosin, resin, or acid-based chemicals, depending on the application. Rosin-based fluxes are common for electronics, while acid-based fluxes are used for plumbing and other applications.
- Forms: Available in paste, liquid, and solid forms, and is sometimes incorporated into the core of solder wire (cored solder).
Table Summarizing the Differences
| Feature | Solder | Flux |
|---|---|---|
| Primary Role | Bonding metal pieces together | Cleaning metal surfaces and promoting solder flow |
| Composition | Metal alloy (e.g., tin-lead, tin-silver-copper) | Chemical compound (e.g., rosin, resin, acid) |
| Function | Provides electrical and mechanical connection | Removes oxides, improves wetting, and protects surfaces from oxidation during soldering |
| State | Solid (until melted) | Solid, liquid, or paste |
In simpler terms: Imagine you are gluing two pieces of wood together. Solder is the glue, and flux is like sanding the wood beforehand to ensure the glue sticks properly.
