Types and mechanisms of brazing/soldering

Brazing/soldering is a method of joining without melting the base materials. Instead, it uses a filler material (brazing paste or soft filler material i.e. solder) that melts at a temperature lower than the base materials. Filler materials contain flux to ensure proper joining with the base material.

Applications of brazing/soldering include pipes, connectors and valves requiring leak tightness; pressure vessels requiring pressure resistance and leak tightness; and vehicle parts requiring corrosion and heat resistance. Soldering using a soft filler material (solder) is widely used for electronic circuits, electrical connectors, and precision electronic components.

Types and mechanisms of brazing/soldering
  1. Filler material or solder
  2. Joined section

Classification by melting temperature (brazing and soldering)

Brazing and soldering are classified by the melting temperature of the filler material. Brazing uses filler materials that have melting temperatures of 450°C or higher; and soldering uses solders (soft filler materials) that have melting temperatures below 450°C.

Classification by melting point Brazing/soldering method
Brazing (Melting point: 450°C or higher) A method of welding that uses filler materials while melting the base material as little as possible.
  • Open air brazing(torch brazing, induction heating brazing, etc.)
  • Controlled atmosphere brazing(furnace brazing, non-oxidizing atmosphere brazing, etc.)
  • Brazing using light energy(laser brazing)
Soldering (Melting point: Below 450°C) A method of welding that uses solders (soft filler materials) that have low melting points while melting the base material as little as possible.
  • Manual work using a soldering iron
  • Soldering by robots or automatic machines
  • Soldering (soft brazing) using light energy (light beam soldering)


Brazing is a method of welding that uses filler materials with high melting points.
Torch brazing uses a normal gas welding torch as a heat source, and induction heating brazing uses high-frequency induction heating as a heat source. Another method is controlled atmosphere brazing (furnace brazing) that is done inside a vacuum furnace without using flux by heating and cooling the base material and filler material. These welding methods are used for non-oxidizing brazing of stainless steel and for the automation of joining titanium and ceramic workpieces.

In recent years, another brazing technique known as laser brazing has attracted a lot of attention.
Laser brazing uses light energy (laser) to melt a wire-shaped filler material supplied between base materials to join them. Since this process rarely melts the base materials, thermal deformation is minimized. This allows lightweight and highly rigid joining without affecting the product design.
Resistance spot welding was generally used to join automobile roofs, side panels, and trunk lids. For example, when joining a roof and body, they had to add processes to provide a groove for resistance spot welding and then cover the part with molding to hide the groove and weld spots.
Since laser brazing does not spoil the appearance of the base material, the processes for working the groove and preparing molding or other parts can be eliminated. Laser brazing can almost double the joint strength and joining speed compared with resistance spot welding. This process is expanding in the automotive and other industries in Europe and Japan.

Example of Laser brazing applications in automobile manufacturing
Example of Laser brazing applications in automobile manufacturing


Soldering is a method of welding that uses filler materials with low melting points.
Normal soldering uses heat produced by an electric current such as a soldering iron.
Light beam soldering has been adopted for the production of electronic components in FA (factory automation). It uses a reflector to converge the light generated from a large output light source, focuses the light on the weld area and melts the solder with the energy of the light. Since the process uses solders (soft filler materials) with low melting temperatures and allows the use of robots for precise joining, it is useful for assembly automation and mass-production of heat-sensitive electronic components.