THR soldering

Through-hole reflow (THR) soldering mounting technology combines the solder connections of through-hole technology, which are particularly stable in mechanical terms, with the production processes of surface mounting, which can be automated efficiently.

Your advantages

  • Reproducible high process quality, thanks to the high degree of automation
  • Through-hole technology ensures the high mechanical stability of the connection component
  • High process efficiency, thanks to processing THR and SMD components using one method


In the case of THR mounting, solder paste consisting of flux and solder balls is deposited in the drill holes of the PCB to be assembled by means of screen printing. In rare cases, additional solder deposits are made available in the form of molded parts or by means of dispensers.

The components that are to be assembled are pressed into the holes filled with solder paste (pin in paste). Since the solder paste contains a rosin that only starts flowing at temperatures above +100°C, the viscous solder paste remains on the pin surface until the actual soldering process, without dripping.

The four steps of THR soldering

The pin in paste principle

In order to avoid material damage caused by the different expansion coefficients of the individual components, the entire module is gradually heated to around +150°C. The module is then rapidly heated to a temperature above the specific solder melting temperature. Only then is the actual soldering process carried out at temperatures of up to +260°C over a period of up to 40 seconds.

The solder melts, it passes through the bore hole along the pin flank by means of capillary action and fills the drill holes completely. On subsequent cooling of the module, reliable and permanent connections are established between the pin surfaces that are to be soldered and the metal-plated drill holes of the PCB.

The key requirements of THR components and their preparation are described in the following standard:

  • IEC 61760-3: Surface mounting technology – Part 3: Standard method for the specification of components for Through Hole Reflow (THR) soldering

Find the right solution for you in no time at all

All PCB connections for THR soldering can be found via the link below.


C6 The Exchange
Calmount Park
Dublin 12
D12 XE18