has a narrow gap provided within a metal foil pattern on the surface of the printed circuit board and a low melting point metal such as solder bridges this gap to connect the metal foil application_number US 18771380 A description to facilitate understanding the present invention a brief reference will be made to a conventional safety construction for a printed circuit board referring to fig1 numeral 1 denotes a board made of an insulating material such as resin numeral 2 denotes a metal foil patterned on the board 1 numeral 3 denotes a narrow part whose width is made narrower than that of other metal foils so that its resistance is made particularly large consequently when an abrupt large current flows into the narrow part 3 due to the occurrence of abnormality the narrow part 3 of the metal foil 2 is melted to serve as the overcurrent protector means however such a safety construction was ineffective for instantaneously interrupting a current somewhat larger than an ordinary current of about 1a or less using a simple reduction of cross section in the metal foil of the same material used in view of the above description reference is now made to fig2 and 4 and more specifically to fig2 wherein a preferred embodiment of the safety construction according to the present invention is illustrated fig2 illustrates an enlargement of the.