THT Manufacturing (Through Hole Technology)

The conventional THT placement is now largely replaced by SMD assembly. However, some components such as flat cables (strands), connectors, coils or large capacitors still have to be wire-assembled. In contrast to SMD assembly, the components are inserted through the contact holes into the printed circuit board and then combined by wave soldering, selective soldering, hot bar soldering or manual soldering, depending on the technical design.

THT Manufacturing Process Flow

At a.p. microelectronic, THT assembly is carried out manually by trained specialist staff on state-of-the-art production lines. Both pure THT and mixed assembly are possible here. Needless to say, all equipment is up to date and regularly serviced. This ensures reliable and high-quality assembly.

Wave Soldering

During wave soldering, mainly THT components are placed on the printed circuit board and then soldered. To this end, the assembly is initially wetted with soldering fluxes and is then preheated. The assembly is then guided over the solder wave and coated with solder. The solder wave is produced by pumping liquid solder through an opening. After the soldering process has been completed, the assembly is cooled to reduce the thermal stress.

Selective Soldering

Selective soldering is a variant of wave soldering. The soldering is not performed for the complete assembly, but only for certain areas. In this process, the effectively soldered area can be as small as a few square millimetres, depending on the shape of the solder nozzle. To achieve this, the assembly is placed precisely over the wave with a positioning device. Each component to be soldered must be programmed with the exact values of the x and y axis. During this process, soldering fluxes are applied onto the assembly by a small spray nozzle and then the assembly is preheated. Now the assembly is precisely guided over the solder nozzle and the components are soldered. Selective soldering is used when many SMD components have already been soldered on a printed circuit board in a reflow process and only a few THT components have to be soldered.

Hot Bar Soldering

Hot bar soldering is a process where a heated thermode, also called hot bar, exerts pressure onto the individual components (e.g. a flat conductor) to be soldered. The thermode transmits the required thermal energy to the soldering joint. The thermode can be customised to your specific product requirements.


Bei der ältesten Art des Lötens, führt man der Lötstelle Wärme und Lot manuell per Hand zu. Handlötkolben gibt es mit und ohne Regelstation, mit unterschiedlicher Leistung und unterschiedlichen Arten von Lötspitzen. Seit über 30 Jahren wird bei a.p. microelectronic, das Verfahren der Handlötung praktiziert, daher bieten unsere Mitarbeiter Geschick und Erfahrung um eine saubere Lötstelle herzustellen.