Why can't copper wire and aluminum wire be directly connected?

Copper and aluminum wires are commonly used conductive materials in electrical engineering. Although they are both conductive materials, they are not completely interchangeable with each other. In fact, copper wire and aluminum wire cannot be directly connected because of their different properties, which may lead to adverse consequences. Let's take a look at the reasons together.
1. Issues with chemical reactions
Chemical reactions occur between copper and aluminum due to their significant differences in chemical properties. Aluminum is a reactive metal that accelerates oxidation when in contact with copper, causing the device to become unstable.
2. Issues of thermal expansion and contraction
Due to their different coefficients of thermal expansion and contraction, copper and aluminum can experience varying degrees of expansion when subjected to temperature changes. Therefore, if copper wire and aluminum wire are directly connected, it will cause stress in the circuit, which will have a significant impact on the working state of electronic components because the components operate at a certain voltage.
3. Connection failure issue
If copper and aluminum wires are directly connected together, this connection method is prone to connection failure. This is because when aluminum and copper wires are connected, the quality between the metals is not sufficient, so if appropriate measures are not taken, they will become loose, thereby affecting the performance of electrical equipment.
To address these issues, we typically use conversion terminals to connect copper and aluminum wires. Conversion terminal is a specialized conductor used for switching, which can overcome the chemical reaction between copper and aluminum and alleviate the stress caused by thermal expansion and contraction, thereby ensuring the safety and performance of electrical equipment.
In summary, copper and aluminum wires cannot be directly connected due to differences in their chemical properties, thermal expansion and contraction coefficients, and other factors. Therefore, it is recommended that for the safety and performance of electrical equipment, we should choose suitable conversion terminals to connect copper and aluminum wires.