Safety device of electric circuit and process for producing the same

A safety device of an electric circuit comprising:

• first protective means in an overcurrent protector for protecting the electric circuit from an overcurrent, which generates heat to increase its electrical resistance when an overcurrent flows in the electric circuit, whereby reducing or cutting off the overcurrent;
• and
• second protective means including a thermal fuse situated in the vicinity of the overcurrent protector comprising:
• a first electrode having a first conductor pattern connected to the overcurrent protector;
• a second electrode having a second conductor pattern insulated from the first electrode by a gap;
• and
• solder connecting the first and second electrodes and melting by heat from the overcurrent protector so as to split into two parts toward the first and second electrodes,
• wherein the second conductor pattern for forming the thermal fuse is formed on one side of the circuit board and connected to the second electrode having an island shape formed on an opposite side of the circuit board through a through-hole, the first electrode continuously surrounds the second electrode with a gap between the first and second electrodes on the opposite side of the circuit board, and solder connects the first and second electrodes.