Low temperature atmospheric pressure plasma for cleaning and activating metals

A method for producing an atmospheric pressure plasma, comprising:

• providing a housing having an inlet for gas flow comprising argon or helium and one or more molecular gases, a flow path within the housing for directing the gas flow to become laminar, and an outlet for plasma produced from the gas flow comprising reactive neutral species in the laminar gas flow to exit from the housing and contact a substrate placed a distance downstream;
• providing a powered electrode disposed within the housing having a powered electrode surface proximate to the laminar gas flow;
• providing a grounded electrode disposed adjacent to the powered electrode such that a grounded electrode surface is closely spaced from the powered electrode surface and the laminar gas flow is directed therebetween;
• providing a power supply for delivering radio frequency power coupled to the powered electrode and the grounded electrode to ionize the laminar gas flow and produce the plasma comprising the reactive neutral species;
• and
• circulating a fluid through a hollow space in at least one of the powered electrode and the grounded electrode, thereby maintaining a uniform temperature across the housing.