Updated: December 27th, 2019

The quality of the joining processes undergone by some connectors can be a key factor in component performance. The latest article in our “Connector Basics” series by APEX Electrical Interconnection Consultants covers the basics of connector soldering.

Connector Soldering BasicsMany connectors and related components are subject to joining processes, which primarily involve soldering. Less commonly used joining processes include welding, brazing, and use of organic compounds, both conductive and non-conductive (epoxies, “organic solders,” etc.).

The distinction between soldering and brazing is somewhat arbitrary. Both processes use a filler alloy to join two surfaces without melting the substrates themselves. The basic distinction between brazing and soldering is based on the melting point of the solder (or more generally, on the temperature of the liquidus – the point when the solder is completely liquid). This boundary is commonly set at 840ºF (450ºC); below this temperature the process is considered soldering and above it is considered brazing.

Wetting and Spreading

At the initial stages of soldering, flux is applied to the substrate to be soldered; the purpose of the flux is to remove any oxide, which enables the molten solder to wet the clean substrate metal. This creates an interface between the liquid solder and the solid substrate that has lower interface energy than the clean metal/flux interface tha