Process for fabricating multilayer circuit boards
AssigneeMacDermid, Incorporated
InventorJohn L. Cordani
Life of this patent
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Abstract
Printed circuit boards having copper circuit patterns coated with an adhesion promoter (e.g., copper oxide, tin) are subjected to the action of an aqueous chromic acid solution prior to incorporation in a multi-layer board by interposing layers of semi-cured polymeric non-conductive material between the individual boards and laminating the assembly using heat and pressure. The chromic acid treatment serves to improve adhesion between the layers and, in particular, to overcome or minimize the "pink ring" effect which is frequently observed around holes drilled through multilayer boards.
Claims14
In a process for the preparation of a multilayer printed circuit board which comprises the steps of:
- providing a non-conductive substrate clad on each side with a copper circuit pattern layer;
- applying a coating of adhesion promoter to the copper circuit pattern layers;
- and
- incorporating the resulting board and one or more additional boards prepared in the same manner into a multilayer board by interposing layers of semi-cured polymeric non-conductive material between said boards and laminating the assembly using heat and pressure;
- the improvement which comprises exposing the copper circuit patterns coated with adhesion promoter to the action of an aqueous chromic acid solution prior to incorporation of said boards into the multilayer board.
In a process for the preparation of a multilayer printed circuit board the steps comprising:
- providing a plurality of non-conductive substrates clad on each side with a layer of copper;
- applying a relief resist image of a circuit pattern to each copper layer and etching away the exposed copper;
- removing the resist and applying a coating of copper oxide to the exposed copper circuit pattern;
- exposing the copper oxide-coated copper circuit pattern to the action of an aqueous chromic acid solution;
- and
- thereafter incorporating said plurality of boards so prepared into multilayer board by interposing layers of semi-cured polymeric nonconductive material between said boards and laminating the assembly using heat and pressure.
Dependencies are inferred from the claim text.