Employing the HF welding process, the fin is wound on edge around the tube and a continuous weld is obtained. A high-frequency current of approx. 450 kHz is applied by contacts on the fin and tube and the resistance in this circuit produces the heat necessary for welding.

This resistance welding process produces an equally strong metallurgical bond between the fin and the tube as the NOH finning method (GMAW) with a 90% average welding width assuring an optimal heat transfer.