in a semiconductor module with a substrate having a plurality of semiconductor devices mounted on the top surface , an internal metallurgy system interconnecting the devices , an auxiliary set of conductive lines with periodically occurring surface connecting terminals , engineering change terminals with electrical connections to the device terminals and to the internal metallurgy system , the improvement being engineering change devices , terminals on the engineering change devices to establish electrical contact with the engineering change terminals and the surface connecting terminals , a tailorable metallurgy system which permits establishing selective electrical connections between individual terminals of the engineering change devices , and deletable surface lines on the substrate to selectively electrically isolate selected engineering change terminals from the internal metallurgy .