Semi-additive is the most common process: The unpatterned board has a thin layer of copper already on it. A reverse mask is then applied. (Unlike a subtractive 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 to any desired weight. Tin-lead or other surface platings 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. COUNT 5
QSN1 In the semi-additive process, what do the areas exposed by the mask become at the end? ANS1 traces QSN2 What metal is used to plate the unmasked parts of the board in the semi-additive method? ANS2 copper QSN3 After the mask comes off of the board, what step takes off the original plating? ANS3 etching QSN4 What company used to make radios with additive boards in the mid-20th century? ANS4 General Electric QSN5 What weight of plating is possible with copper? ANS5 any