Abstract:
Multilayer printed circuit boards are fabricated by preparing a first layer in conventional manner by forming a resist image on a copper clad substrate, etching away unwanted copper, removing the resist from the circuit pattern and optionally applying a dielectric mask such as conventional solder mask to selected portions of the circuit pattern. A second layer, and optionally one or more subsequent layers, are fabricated by providing an image of a second circuit pattern in a predetermined location on said first layer, the image being formed using a suspension of cuprous oxide in a curable resin material. The image is cured at least partially and subjected to chemical reduction to convert at least a portion of the cuprous oxide to metallic copper such that the unreduced cuprous oxide in resin serves as a dielectric layer. The image is then electrolessly plated with copper to build up the circuit pattern and the latter is selectively coated with a dielectric mask before repeating the cycle to build up one or more additional layers. Solder can be applied to selected areas of any of said printed circuit layers at any appropriate time during fabrication. The above method of fabrication has advantages of economy of time, materials and labor as compared with methods hitherto employed to prepare multilayer boards in which a plurality of single boards are fabricated individually and then assembled as a sandwich or laminate by application of heat and pressure.
Abstract:
The present invention is directed to a process for increasing the adhesion of a polymeric material to a metal surface, especially during the manufacture of printed circuit boards. The metal surface is contacted with an adhesion promoting composition to form a micro-roughened surface and is then contacted with an aqueous amine-formaldehyde post-dip polymer composition. The amine is preferably melamine. Thereafter polymeric material may be bonded to the treated metal surface. The amine formaldehyde polymer post-dip composition comprises an acid, a pH adjuster, and an effective amount of an amine-formaldehyde reaction product polymer. The amine-formaldehyde reaction product polymer is formed by dissolving amine in an aqueous formaldehyde solution, adding an additive selected from the group consisting of triethanolamine, ethylene glycol, and methanol, adding an acid selected from the group consisting of acetic acid and sulfuric acid, diluting the solution with water, and adjusting the pH of the solution with a pH adjuster.
Abstract:
An additive process for making printed circuit boards utilizing aqueous alkaline strippable resists, in which a suitable insulating substrate is patterned with the resist, the resist-patterned substrate catalyzed to electroless metal deposition, the resist then stripped completely from the substrate, utilizing an aqueous alkaline solution, preferably containing a reducing agent, and the electroless metal then deposited over the areas of the substrate catalyzed in the desired pattern.
Abstract:
Electroless copper deposition solutions, and method of electrolessly depositing copper onto a suitably catalysed and generally non-conductive workpiece surface using these solutions, are disclosed. The solutions contain, in addition to water as the usual solvent, a soluble source of copper ions, a complexing agent or mixture of agents to maintain the copper in solution, and a copper reducing agent effective to reduce the copper ions to metallic copper as a deposit or plating on a prepared surface of a workpiece brought into contact with solution. The reducing agent is a soluble source of hypophosphite ions and the complexing agent is selected to be effective at pH level between 5 and 13 for complexing cupric ions and the solution pH is coordinated within the pH range for the complexer selected to give a deposited conductive copper film.
Abstract:
Immersion tin-lead baths are provided, preferably free of hypophosphite ion, comprising a strongly acidic aqueous solution comprised of thiourea, water-soluble sources of divalent tin and lead, a weak acid, and a weak base.
Abstract:
Metallic surfaces to be provided with a tin-lead coating from an immersion tin-lead bath, and particularly copper surfaces (e.g., through-holes, pads) of a printed circuit board having other metallic surfaces thereon covered by a hydrophobic solder mask, are prepared for receipt of immersion tin-lead coating by, e.g., contact thereof with a strongly acidic aqueous pre-dip solution containing at least one surface active agent functional to reduce the surface tension of the pre-dip solution and/or to provide the solution with improved affinity for the metallic surface.
Abstract:
PROCESS FOR PREPARING MULTILAYER PRINTED CIRCUIT BOARDS Multilayer printed circuit boards are fabricated by preparing a first layer in conventional manner by forming a resist image on a copper clad substrate, etching away unwanted copper, removing the resist from the circuit pattern and optionally applying a dielectric mask such as conventional solder mask to selected portions of the circuit pattern. A second layer, and optionally one or more subsequent layers, are fabricated by providing an image of a second circuit pattern in a predetermined location on said first layer, the image being formed using a suspension of cuprous oxide in a curable resin material. The image is cured at least partially and subjected to chemical reduction to convert at least a portion of the cuprous oxide to metallic copper. The image is then electrolessly plated with copper to build up the circuit pattern and the latter is selectively coated with a dielectric mask before repeating the cycle to build up one or more additional layers. Solder can be applied to selected areas of any of said printed circuit layers at any appropriate time during fabrication. The above method of fabrication has advantages of economy of time, materials and labor as compared with methods hitherto employed to prepare multilayer boards in which a plurality of single boards are fabricated individually and then assembled as a sandwich or laminate by application of heat and pressure.