Potential equalisation is possible
Many components are sensitive to low voltages and currents. A voltage flashover inside a component can cause early damage which ultimately leads to failure.
To prevent this, attention must be paid to proper grounding, e.g. by observing the necessary safety precautions for employees such as the wearing of wristbands or by regularly checking the voltage dissipation and earthing resistance between the soldering tip and the power plug.
In the power supply, however, there is often a bigger problem known as SEMP – Switching Electro Magnetic Plus. Transient voltage spikes in the PE conductor up to within the KV range caused by switching large inductors, transformers or motors on and off. In long installation lines, for example, these voltage spikes are not dissipated to ground through the PE conductor. They find the shortest route: socket - connector plug - soldering tip – Common Point Ground (CPG) – to building ground. This means that there is a danger of damaging ESD-sensitive components even if the soldering station is properly connected.
Measurements have shown that a voltage of 29.6 ssV can still be present in the PE conductor after switching the neon lighting on/off. These voltage spikes are sufficient to damage ESD-sensitive components.
Before a decision is made on the determination of ESD protective earth, therefore, the PE conductor must be checked for voltage spikes. If there is the slightest doubt, then Common Point Ground (CPG) on the workstation is used for ESD protection instead of the PE conductor of the mains cable.
This, however, is not possible with all soldering or rework tools. In this case, the Weller soldering and rework stations offer an elegant and simple solution - a 3.5 mm jack plug. If this plug is inserted into the designated socket, the external PE conductor is interrupted. In this case, the tool would be potential free – which is the worst ESD protection. A flexible line at the centre of the connector solves this problem. The end of the line is connected to Common Point Ground (CPG) and the soldering tip is connected to workstation potential – a spike-free workstation grounding point. The end line is mated to the workstation surface – the classic method of potential equalisation. The best solution is that the soldering tip has the same surface potential as the workstation.