Soldering vs. Brazing - What is the Difference?

Often welding comes to mind when you think about joining metal components. However, two other methods are often preferred in certain circumstances: soldering and brazing. Instances where these methods may be selected over welding:

• when joining different thicknesses of metal
• when joining two different types of metals
• when joining thin metals
• when melting the base metals is disadvantageous
• when appearance matters

Temperature Differences for Soldering and Brazing

Soldering and brazing are both done at a lower temperature than welding. Unlike welding, the base metal doesn’t melt, so the temperature must be lower than the base metal melting point. Since the base metal doesn’t melt, it retains its physical properties and is not at risk for warping or distortion, as can happen with welding.

Both methods require using a filler material (metal alloy) to bond the materials. Brazing and soldering work by creating a metallurgical bond between the filler material and the metals being joined. The melted filler pulls itself across the closely fitting adjacent surfaces through capillary action. Both temperature and joint clearance distance are critical for the capillary process to work.

Soldering is done at the lowest temperature of the two, where the filler’s melting point is below 842°F (450°C), according to the American Welding Society (AWS). In between the temperatures of soldering and welding is brazing, using a filler material that melts at a temperature above 842°F (450°C) but is lower than the base materials being joined.

Of course, to melt the filler, heat is required. The heat can be applied in many manners, including induction, flame, resistive heating, and lasers.

Use of Flux

Often fluxes are used to aid in brazing and soldering. Fluxes, which are available in many forms (e.g., solids, powders, pastes, liquids), remove surface oxides, promote wetting, and aid in the capillary action required to form the bond. Although both processes use flux, the chemical make-up of the flux differs for each. Flux residue is unwanted on some applications, so no clean flux that leaves minimal residue may be used.

Types of Joints

Brazing creates a stronger joint than soldering. Braze joints can withstand shock and vibration, are unaffected by typical temperature changes, provide electrical conductivity, and are easily plated using conventional processes. However, solder joints not being as strong can be unsoldered to repair defects if needed.

The most common joints are lap joints (two pieces overlap with filler between) and butt joints (two ends butting against each other). Variations on these joints can create different joint types, such as a corner or tee joint, which are butt joints with metal turned to form a tee or corner.

Applications

Soldering is used in applications, such as electronic circuit boards and light-duty products, where the bond is not subjected to load or stresses. Since brazing creates a stronger bond than soldering, products that may experience stress or vibrations do well with brazing. Both processes are used in products in various industries, including automotive, medical, HVAC, aerospace, and more.  

Brazing and Soldering at Aztalan

We provide full-service metal manufacturing, including soldering and brazing. We have a variety of materials and fluxes and work with a variety of metals, including brass, stainless steel, and others. Contact us to learn more about our brazing and soldering services.