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Additive Processes of PCB

  Time:2012-06-01 11:13

Additive processes add desired copper traces to an insulating substrate. The most common is the "semi-additive" process:the unpatterned board has a thin layer of copper already on it. A reverse mask is then applied.(Unlike a substractive process mask,this mask exposes those parts of the substrate that will eventually become the traces.) Additional copper is then plated onto the board in the unmasked areas;copper may be plated tp any desired weight.Tin-lead or other surface plating are then applied.The mask is stripped away and a brief etching step removes the now-exposed bare original copper laminate from the board,isolating the individual traces.Some single-sided boards which have plated-through holes are made in this way. General Electric made consumer radio sets in the late 1960s using additive boards.
The additive process is commonly used for multi-layer boards as it facilitates the plating-through of the holes to produce conductive vias in the circuit board.