Fuel processor / fuel cell systems for mobile applications are expected to be future mass products. Therefore, fabrication techniques are required, which can cope with high volume production at competitive pricing. Finally, the stainless steel or aluminium reactors and heat‐exchangers will be sealed by automated procedures such as laser welding, limiting the heat impact onto the catalysts applied in the reformers. Laser welding with dynamic beam forming is capable to weld the plate stacks of the heat‐exchanger reliably and mechanically stable to meet the demands of daily operation of such reactors.