THT assembly with selective soldering: when, how and why to use it

What is THT assembly and what is selective welding? These are the two main questions addressed in this technical article, written in a clear and easy-to-understand way. After reading it, and thanks to Electrolomas, it will be easier to determine when, how, and why to use them.

Selective welding in THT: advantages over wave welding

Selective soldering refers to automated processes that allow the soldering of through-hole technology (THT) components onto a printed circuit board (PCB). This is done with absolute precision and on an individual basis.

To achieve this, the technique uses a small, movable soldering nozzle, known as a soldering station or mini-wave. This technique differs significantly from previous methods because it eliminates the need to immerse the entire board.

Ideal uses and recommendations for selective THT mounting

The next question is when to use this selective mounting method. The answer is clear: it’s ideal for mixed-technology boards: THT and SMT. This is especially true when THT components are located near heat-sensitive components (SMD) or plastic connectors. It’s important to consider that these latter components could be damaged by the more common wave soldering process.

Therefore, to establish a guide for ideal uses, consider the following:

• Assemblies with THT components that have high thermal mass, as they require more heat.
• High-reliability applications. For example, automotive, aerospace, industrial control, etc.
• Complex designs with high component density on the underside of the PCB.
• Prototypes and low- to medium-volume production.

 Ventajas THT frente a la soldadura por ola tradicional

Selective soldering offers significant advantages over THT when it comes to achieving precision and protecting components.

In summary, its most positive aspects are:

• Precision and less thermal damage.
• Reduction of defects and rework.
• Flexibility.
• Resource savings.

Without a doubt, we recommend contacting Electrolomas for THT assembly. They know the best practices for this technique better than anyone! Among other things, they optimize parameters, perform gradual preheating, and use a specific flux.