Wave soldering is a soldering process where, depending on the assembly method, through-hole electronic components or connection elements are soldered onto the PCB manually or using pick-and-place machines.
First, the entire module is wetted with flux on the solder side, then pre-heated, and finally run through a single or double solder wave where it is wetted with the solder. In the case of lead-free solder, the soldering temperature is around 260°C. After soldering, the entire module is cooled in order to reduce the thermal load on the PCB again.
Wave soldering is primarily used to solder through-hole components (through-hole technology – THT), however it is also used to mount surface mounting components (surface mounting technology – SMT) on the bottom of the PCB.
If only THT components are soldered, which by virtue of their design must withstand greater mechanical strain, wave soldering is always the standard method.
Two solder waves (chip and Lambda or Wörthmann wave) are used one after the other in order to reliably solder THT components onto the top of the PCB and SMT components onto the bottom of the PCB in a single step. Unlike selective soldering where only a part of the module is soldered, wave soldering is usually a faster and more cost-effective method for processing a larger number of components for soldering.
In addition to the soldering temperature, other important process parameters for wave soldering include the immersion depth of the PCB, the angle at which it passes through the wave soldering machine, the soldering time, and the type of solder wave.
The following standards, which apply to surface mounting components as well as through-hole components, define whether components are suitable for the wave soldering process:
These standards describe the temperature profiles for SMT and THT components. The limit values specified here are usually higher than the actual temperature loads encountered in practice. The permissible temperature profile for the relevant components depends on the design of all components, the thickness and size of the PCB, and the solder used.
This example profile for a laminar wave shows the temperature limit values of > +250°C for three seconds.
For this limit value profile, the total maximum temperature loads for both waves are > +250°C for five seconds.
All PCB connections for wave soldering can be found via the link below.