 
 <prompt> Wetin dey inside di planks? Based on di question wey dey above, write one context wey contain di answer. E fit be 1 - 20 sentences. Context: <response>: Semi-additive na di most common process: Di unpatterned board don get small layer of copper already on top. A reverse mask dey applied. (Unlike subtractive process mask, dis mask dey expose those parts of di substrate wey go eventually become di traces.) Extra copper dey plated onto di board for di unmasked areas; copper fit dey plated to any desired weight. Tin-lead or other surface platings dey applied. Di mask dey stripped away and a brief etching step dey remove di now-exposed bare original copper laminate from di board, isolating di individual traces. Some single-sided boards wey get plated-through holes dey make for dis way. General Electric make consumer radio sets for di late 1960s using additive boards. 