Soldering terminology

If two metallic conductors (A and B) are connected to each other, as shown in the figure, with different temperatures prevailing at the m and n contact points, a potential difference arises and a direct current flows within the circuit. This phenomenon is known as the Seebeck effect. If room temperature prevails at point m and a higher temperature is set for point n, the temperature can be calculated by measuring the current in the circuit. Similarly, a temperature difference arises between points m and n when applying a current to the circuit, which is known as Peltier effect. The metal pair involved here is called a thermocouple. Depending on the measured temperature, one of the pairs listed in the table below can be used :

It is sufficient to use the Ni-Cu (constantan) / copper or constantan/iron pairs to measure the temperature during soldering, but alumel/chromel is used to avoid corrosion at high temperatures. This pair is widely used for temperature measurements in SMT reflow ovens or during the process of melting solder alloys as well.