Electroless plating process for the manufacture of printed circuit boards

A process for preparing a printed circuit board comprising the steps of:

• a) drilling a least one through-hole through a board comprising a non-conductive substrate, deburring and desmearing said through-hole and cleaning and conditioning said through-hole and at least one surface of said substrate;
• b) contacting the cleaned and conditioned board resulting from step a) with a stabilized sensitizing solution comprising (i) ions of a metal selected from the group consisting of Group VIII and IB transition metals, (ii) stannous ions present in the solution in a molar concentration in excess of the concentration of said metal ions, (iii) an acid and (iv) a buffering salt;
• c) contacting the sensitized board resulting from step b) with a solution containing a noble metal to thereby catalyze the board for subsequent electroless metal plating;
• d) contacting the board resulting from step c) with a dry film photoresist, imaging the resulting board with a pattern corresponding to a desired circuit pattern and developing the imaged board;
• e) contacting the developed, imaged board resulting from step d) with an acidic cleaning solution;
• and
• f) immersing the board resulting from step e) in an aqueous acidic electroless nickel metal depositing solution, for a time, at a concentration and at a temperature sufficient to prepare the board for subsequent pattern electroplating, said aqueous acidic electroless nickel metal depositing solution comprising (i) nickel ions, (ii) a complexing agent (iii) a reducing agent capable of reducing the nickel ions to nickel metal in an acidic state, provided said reducing agent does not contain any formaldehyde or formaldehyde-generating composition and (iv) one or more stabilizers.

An electroless plating process comprising the steps of:

• a) contacting a surface of a non-conductive substrate with a cleaning and conditioning composition comprising at least one glycol ether;
• b) treating the cleaned and conditioned surface resulting from step a) with an alkaline permanganate solution for a time, at a concentration, and at an elevated temperature sufficient to prepare such surface for a metal lay to be subsequently applied by electroplating;
• c) contacting the surface resulting from step b) with an aqueous neutralizing and conditioning solution comprising water, hydrogen peroxide, at least one acid sulfate compound and at least one cationic surfactant;
• d) contacting the surface resulting from step c) with a stabilized sensitizing solution comprising (i) ions of a metal selected from the group consisting of Group VIII and IB transition metals, (ii) stannous ions present in the solution in a molar concentration in excess of the concentration of said metal ions, (iii) an acid and (iv) a buffering salt;
• e) contacting the sensitized surface resulting from step d) with a solution containing a noble metal salt to thereby catalyze the surface for subsequent electroless metal plating;
• f) contacting the board resulting from step e) with a dry film photoresist, imaging the resulting board with a pattern corresponding to a desired circuit pattern and developing the imaged board;
• g) contacting the developed, imaged board resulting from step f) with an acidic cleaning solution;
• and
• h) immersing the board resulting from step g) in an aqueous acidic electroless nickel metal depositing solution, for a time, at a concentration and at a temperature sufficient to prepare the board for subsequent pattern electroplating, said aqueous acidic electroless nickel metal depositing solution comprising (i) nickel ions, (ii) a complexing agent (iii) a reducing agent capable of reducing the nickel ions to nickel metal in an acidic state, provided said reducing agent does not contain any formaldehyde or formaldehyde-generating composition and (iv) one or more stabilizers.

An electroless plating process comprising the steps of:

• a) preparing a surface of a non-conductive substrate by subjecting such surface to plasma desmearing;
• b) contacting the prepared surface resulting from step a) with a glass etching solution comprising hydrofluoric acid;
• c) contacting the surface resulting from step b) with an aqueous conditioning solution comprising hydrogen peroxide and at least one cationic surfactant;
• d) contacting the surface resulting from step c) with a microetching solution consisting essentially of sulfuric acid, hydrofluoric acid and acetone;
• e) contacting the surface resulting from step d) with a stabilized sensitizing solution comprising (i) ions of a metal selected from the group consisting of Group VIII and IB transition metals, (ii) stannous ions present in the solution in a molar concentration in excess of the concentration of said metal ions and (iii) hydrochloric acid;
• f) contacting the sensitized surface resulting from step e) with a solution containing a noble metal salt to thereby catalyze the surface for subsequent electroless metal plating;
• g) contacting the surface resulting from step f) with a dry film photoresist, imaging the resulting surface with a pattern corresponding to a desired circuit pattern and developing the imaged surface;
• h) contacting the developed, imaged surface resulting from step g) with an acidic cleaning solution;
• and
• i) immersing the surface resulting from step h) in an aqueous acidic electroless nickel metal depositing solution, for a time, at a concentration and at a temperature sufficient to prepare the surface for subsequent pattern electroplating, said aqueous acidic electroless nickel metal depositing solution comprising (i) nickel ions, (ii) a complexing agent (iii) a reducing agent capable of reducing the nickel ions to nickel metal in an acidic state, provided said reducing agent does not contain any formaldehyde or formaldehyde-generating composition and (iv) one or more stabilizers.