Abstract: Nodule formation in a continuous electroless copper plating system is minimized by independently controlling the dissolved oxygen contents on the plating solution in the bath and in the associated external piping. The level of dissolved oxygen in the plating tank is maintained at a value such that satisfactory plating takes place. At the point where the plating solution leaves the tank, additional oxygen gas is introducted into the solution so that the level of dissolved oxygen in the plating solution in the external piping is high enough to prevent any plating from taking place in the external piping and so that in the external piping the copper is etched or dissolved back into solution. At the end of the external piping, the dissolved oxygen level is reduced so that the dissolved oxygen level of the plating solution in the tank is maintained at the level where plating will take place.

Abstract: Copper is deposited onto a substrate by plating a first layer of copper onto the substrate from an electroless plating bath and plating a second layer of copper onto the first layer of copper from a second and different electroless plating bath. The first and second plating baths differ from each other in at least the cyanide content. The process reduces plating void defects and reduces nodule formation.

Abstract: A process for preparing a substrate, e.g., an epoxy printed circuit board, for subsequent metallization. Active chemical sites are formed adhering to the substrate surface. The substrate is then exposed to a vapor of a volatile organometallic compound, which chemically reacts with the active sites and is decomposed to at least a species of the metal constituent of the compound. This species adheres to the substrate and can be transformed into the free metal which is useful as a seed for subsequent electroless deposition of a metal thereon. If selective deposition is desired, a resist masking layer is used prior to forming the seed layer. Volatile organopalladium compounds, such as (cyclopentadienyl)(allyl)palladium and bis(allyl)pallidium, are particularly effective for depositing a palladium seed which is particularly effective for electroless deposition of copper.

Abstract: Nodule formation in a continuous electroless copper plating system is minimized by independently controlling the dissolved oxygen contents on the plating solution in the bath and in the associated external piping. The level of dissolved oxygen in the plating tank is maintained at a value such that satisfactory plating takes place. At the point where the plating solution leaves the tank, additional oxygen gas is introduced into the solution so that the level of dissolved oxygen in the plating solution in the external piping is high enough to prevent any plating from taking place in the external piping and so that in the external piping the copper is etched or dissolved back into solution. At the end of the external piping, the dissolved oxygen level is reduced so that the dissolved oxygen level of the plating solution in the tank is maintained at the level where plating will take place.

Abstract: A concentrate of a palladium-tin colloidal catalyst is obtained by dissolving stannous chloride in HCl, diluting the solution with HCl and then further diluting the solution with deionized water to thereby obtain a diluted stannous chloride solution. This solution is cooled to room temperature or below. A palladium chloride solution is obtained by dissolving palladium chloride in HCl which in turn is also cooled to room temperature or below. The palladium chloride solution is gradually added to the stannous chloride solution and mixed at about room temperature in order to obtain a homogeneous solution. The temperature of the solution is then gradually increased to about 105.degree. C. to about 110.degree. C. and maintained at that temperature for sufficient time to obtain a homogeneous solution of substantially uniform colloidal particles. The solution of colloidal particles is slowly cooled to about room temperature.