Component for secondary battery and manufacturing method thereof, and secondary battery and multi-battery system manufactured by using the component

A component for a secondary battery comprising:

• a lead-free soldering bridge having a melting point of 150° C. to 300° C. and containing tin (Sn), copper (Cu), and an additional metal;
• and
• a first metal plate and a second metal plate spaced from each other with a minute gap between side edges of the first metal plate and the second metal plate and coupled with the lead-free soldering bridge,
• wherein the content of copper is in the range of 4 to 8 wt%,
• wherein the content of the additional metal is 0.01 to 10 wt%,
• wherein the lead-free soldering bridge is coupled with the first and second metal plates at an area formed by an encounter of grooves formed at edges of top surfaces of the first and second metal plates,
• wherein a top surface of the lead-free soldering bridge is coplanar with the top surfaces of the first and second metal plates.