Electrolysis: processes – compositions used therein – and methods – Electrolytic coating – Coating selected area
Patent
1993-06-16
1994-10-25
Niebling, John
Electrolysis: processes, compositions used therein, and methods
Electrolytic coating
Coating selected area
205123, C25D 502
Patent
active
053586220
ABSTRACT:
A procedure for producing printed circuit boards with pads for insertion of SMDs. A copper lined base plate is provided with a positive photoprotective layer with a coating thickness lesser or equal to the depth of the pads to be built up for the connection of SMD components. The positive photoprotective layer is exposed using a primary film with a window mask corresponding to the desired pad arrangement, and the exposed base plate is developed in a developing bath such that the photoprotective layer is removed in the area of the exposed windows, exposing open copper areas there. The base plate developed in this way is exposed with a secondary film with a mask for the strip conductors, whereby the strip conductors are modeled as opaque areas. The twice-exposed base plate is electroplated in a tin or tin-lead bath, whereby a tin or tin-lead coating is built up in the region of the open copper area until the pads have been formed by this means with a depth greater or equal to the thickness of the photoprotective layer. The electroplated base plate is developed in a developing bath, whereby the tinplated pad areas and the protective layer regions covered by the opaque strip conductor areas of the secondary film remain. The base plate developed in this way is etched, whereby the laid-open copper areas are removed and the protective lacquer existing in the strip conductor areas is removed, laying bare the copper strip conductor areas.
REFERENCES:
patent: 4525246 (1985-06-01), Needham
Firma Korsten & Goossens
Mayekar Kishor
Niebling John
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