Abstract: A plasma generator assembly for treatment of an item to be soldered in a vacuum chamber. The generator includes a chamber having a first opening for placement of a microwave source, formed so that plasma generated from a gas is spread out over a wide area; a second chamber for containing generated plasma effluent; and a partial barrier such as a perforated plate and/or an optical baffle attached to the second chamber. On the opposite side of the partial barrier from the second chamber is the area of the vacuum chamber for treatment of the item.