Electrochemicals, Inc.

Charles Edwin Thorn

Frank Polakovic

Charles A Mosolf

Michael Val Carano

Beth Ann LaFayette

William Yang

A printed wiring board comprising conductive layers separated by nonconductive material and having through holes or other nonconductive surfaces on which an electrically conductive carbon coating is formed. The conductive carbon coating includes electrically conductive carbon having a mean particle size not greater than about 1 micron and a water-dispersible organic binding agent. The conductive carbon coating formed on the nonconductive surfaces has a low electrical resistance and is tenacious enough to be plated and exposed to molten solder without creating voids or losing adhesion.

Printed wiring boards and methods for making them

A method of applying a conductive carbon coating to a non-conductive surface and a printed wiring board having through holes or other nonconductive surfaces treated with such carbon coatings are disclosed. A conditioning agent is applied to the non-conductive surface to form a conditioned surface. A liquid dispersion of electrically conductive carbon (for example, graphite) having a mean particle size no greater than about 50 microns, combined with an organic binding agent, is coated on the conditioned surface to form an electrically conductive carbon coating. The conductive carbon coating is then optionally fixed on the (formerly) nonconductive surface and dried. The resulting coating has a low electrical resistance and is tenacious enough to be plated and exposed to molten solder without creating voids or losing adhesion, yet is easily removable from copper surfaces of the substrate by microetching.

A desmear process for removing resin smeared on an interior wall of a through hole drilled in a resinous substrate, especially resinous substrates made from epoxy, polyimide, cyanate ester resins or bis-maleimide triazine epoxy resins. The process involves contacting the resin smear with a mixture of gamma-butyrolactone and water to soften the resin smear, followed by treatment with an alkaline permanganate solution to remove the softened resin, and treatment with an aqueous acidic neutralizer to neutralize and remove the permanganate residues. The gamma-butyrolactone is effective as a single solvent for softening and swelling resin smears from substrates made from epoxy, polyimide, cyanate ester resins, bis-maleimide triazine epoxy resins, and polyimide resins.

Permanganate desmear process for printed wiring boards

A method of applying a conductive carbon coating to a nonconductive surface, conductive carbon compositions for that purpose, and a printed wiring board having through holes or other nonconductive surfaces treated with such carbon compositions are disclosed. A conditioning agent, made (for example) by condensing a polyamide and epichlorohydrin, is applied to the nonconductive surface to form a conditioned surface. A liquid dispersion of electrically conductive carbon (for example, graphite) having a mean particle size no greater than about 50 microns is coated on the conditioned surface to form an electrically conductive carbon coating. The conductive carbon coating is then optionally fixed on the (formerly) nonconductive surface. Fixing may be accomplished, for example, by applying a fixing liquid such as a dilute aqueous acid to the carbon-coated surface. The coating is then dried.

Direct metallization process employing a cationic conditioner and a binder

A method of applying a conductive carbon coating to a non-conductive surface, conductive carbon compositions for that purpose, and a printed wiring board having through holes or other nonconductive surfaces treated with such carbon compositions are disclosed. A liquid dispersion of electrically conductive carbon (for example, graphite) having a mean particle size no greater than about 50 microns is coated on the non-conductive surface to form an electrically conductive carbon coating. The conductive carbon coating is then fixed on the (formerly) nonconductive surface. Fixing may be accomplished in a variety of different ways. For example, the fixing step can be carried out by applying a fixing liquid to the carbon-coated surface. One example of a suitable fixing liquid is a dilute aqueous acid. Fixing may also be carried out by removing the excess carbon dispersion with an air knife or other source of compressed air. The fixing process removes excessive carbon composition deposits, and thus smooths the carbon coating on the recess surfaces by eliminating lumps and by making the coating more uniform. Fixing can also crosslink the first monolayer of carbon which is directly attached to the substrate or an aqueous organic binding agent associated with the coating. The resulting coating has a low electrical resistance and is tenacious enough to be plated and exposed to molten solder without creating voids or losing adhesion.

Direct metallization process

A method of applying a conductive carbon coating to a non-conductive layer, conductive carbon compositions, and a printed wiring board having through holes or other surfaces treated with such carbon compositions are disclosed. A board or other substrate including at least first and second electrically conductive metal layers separated by a non-conductive layer is provided. The board has a recess extending through at least one of the metal layers into the non-conductive layer. The recess has a non-conductive surface which is desired to be made electrically conductive. The carbon in the dispersion has a mean particle size no greater than about 50 microns. The method is carried out by applying the carbon dispersion to a non-conductive surface of the recess to form a substantially continuous, electrically conductive carbon coating. Optionally, the coating is then fixed, leaving the carbon deposit as a substantially continuous, electrically conductive layer. Chemical and physical fixing steps are disclosed. The resulting coating has a low electrical resistance and is tenacious enough to be plated and exposed to molten solder without creating voids or losing adhesion.

Carbon containing composition for electroplating

A composition and process for preparing a non-conductive substrate for electroplating. The composition comprises 0.1 to 20% by weight carbon (e.g. graphite or carbon black) having a mean particle size within the range of 0.05 to 50 microns; optionally, 0.01 to 10% by weight of a water soluble or dispersible binding agent for binding to the carbon particles; optionally, an effective amount of an anionic dispersing agent for dispersing the bound carbon particles; optionally, an amount of a surfactant that is effective for wetting the through hole; a pH within the range of 4-14; and an aqueous dispersing medium. Improved methods of applying the composition to a through hole, a printed wiring board having a through hole treated with the composition, and a method of fixing a carbon coating deposited on a through hole using an acid solution are also disclosed.

Processes for preparing a non-conductive substrate for electroplating

The present invention is directed to an improved composition and process for preparing a non-conductive substrate for electroplating. The composition comprises 0.1 to 20% by weight graphite having a mean particle size within the range of 0.05 to 50 microns; 0.01 to 10% by weight of a water soluble or dispersible binding agent for binding to the graphite particles; an effective amount of an anionic dispersing agent for dispersing the bound graphite particles; a pH within the range of 4-14; and an aqueous dispersing medium. Optionally, the composition may contain an amount of a surfactant that is effective for wetting the through hole. The resulting graphite dispersion is capable of uniformly coating the through holes in either a double-sided or multi-layer circuit board prior to electroplating. Through holes that were treated with the disclosed graphite dispersion prior to electroplating were free of visible voids after electroplating.

Growing community of inventors

Newport, KY, United States of America

Charles Edwin Thorn