Macdermid, Incorporated

Ann S Williams

Raymond A Letize

Gary B Larson

Peter E Kukanskis

Donald R Ferrier

Wolf Bach

Mary J Senechal

Non-conductive surfaces, particularly through-hole surfaces in double-sided or multi-layer printed circuit board, are treated (conditioned) to receive void-free, adherent electroless metal coatings by contact of the surfaces with an organosilane preparatory to catalyzation and metallization.

Process for metallizing non-conductive substrates

A method of preparing printed circuit boards is described in which the solder mask is applied over a thin layer of copper oxide covering the copper circuit traces, the copper oxide layer being that which remains after stripping the tin or tin-lead alloy etch resist.

Method for manufacture of printed circuit boards

A method of preparing printed circuit boards is described in which the solder mask is applied over a thin layer of copper oxide covering the copper circuit traces, the copper oxide layer being that which remains after stripping the tin or tin-lead allow etch resist.

A two step process is described for selectively stripping tin or tin-lead alloys from a copper substrate without significant loss of copper from the substrate. In a first step the substrate coated with tin or tin-lead alloy is subjected to the action of a first stripping composition which can be any of those known in the art containing a mixture of an oxidant for the metal or metals of said layer and an acceptor for the cation or cations so oxidized. When the stripping has reached the stage at which a thin film of tin remains on the copper substrate the latter is subjected to the action of a second stripping composition which comprises a mixture of an alkali metal hydroxide and an alkali metal chlorite until the film of tin has been removed and replaced by a film of copper oxide. If desired, the latter can be removed by known means such as treatment with aqueous acid. The process represents an improvement over known processes in which, in order to remove the last traces of tin from the copper substrate or to remove the film of tin which in some cases is re-deposited from the stripper composition itself, it is necessary to employ stripping conditions so rigorous that significant loss of copper from the substrate takes place. While the process of the invention is applicable to stripping of tin or tin-lead alloys from copper substrates in a wide variety of contexts, it is of particular application to stripping etch resists from copper substrates after completion of the etching step in formation of a printed circuit board.

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Southbury, CT, United States of America

Ann S Williams