What is a Cold Solder Joint and How to Fix or Prevent It

 PCB solder joints are typically small, and this is especially true as board sizes continue to shrink. Therefore, visual aids such as a magnifying glass or spotlight are often required to inspect them clearly. Checking the color of the joints is the first stage in this visual inspection.  This is significant since a well-formed solder joint usually looks dull.

Next, the shape of the solder joint is inspected. If the joint is distorted or lacks the expected concave profile, insufficient heating likely prevented the solder alloy from fully melting. Consequently, this can lead to increased electrical resistance, which heats the joint—potentially causing it to crack and eventually detach from the board. Subsequently, use a torch and magnifying glass to check for light penetration through the joints. If light passes through a joint, it indicates poor bonding, requiring rework.

Finally, tilt the board to inspect for joints that are partially loose from the board’s substrate. The board should also be checked for solder overflow, as this can lead to short circuits that may severely damage the board.