Why does copper's high thermal conductivity make it difficult to weld?

Copper’s high thermal conductivity makes it difficult to weld because the material rapidly dissipates heat away from the weld zone.12

In welding, a concentrated heat source is required to melt the base metals and create a sound joint. Because copper is an excellent conductor, the heat applied by the welding process is quickly conducted throughout the surrounding material rather than remaining localized at the joint. This rapid heat loss prevents the area from reaching the necessary temperature to achieve proper fusion, often requiring significantly higher heat input or specialized techniques to compensate for the material's thermal characteristics.12