ARRL Technician Practice Exam

What is the characteristic appearance of a cold solder joint?

1. Shiny and smooth surface

2. A grainy or dull surface

3. Bright and glossy appearance

4. A rough and frosted texture

The correct answer is: A grainy or dull surface

A cold solder joint is characterized by a grainy or dull surface, which indicates that the solder did not adequately melt and bond properly to the metal surfaces being joined. This lack of proper solder flow results in a weak, unreliable connection that can easily separate or fail when subjected to stress or temperature changes. In contrast, other appearances such as shiny and smooth surfaces typically indicate a good solder joint where the solder has flowed appropriately, making a solid electrical connection. The bright and glossy appearance often suggests that the solder has formed a strong bond, while a rough and frosted texture could imply other issues but is not characteristic of cold solder joints. The key takeaway is that a grainy or dull surface serves as a clear indicator of poor soldering techniques and the need for rework to ensure reliability in electronic connections.