Definition
A dry joint is a soldered connection that never properly bonded to the metal surfaces it joins, usually because too little solder was used or the solder failed to wet and flow over the pad and lead. The result is a mechanically weak, high-resistance contact that may work at first but is prone to intermittent operation, noise, or an outright open circuit. Visually a dry joint looks dull, grainy, or cracked rather than the smooth, shiny concave fillet of a good joint.
Dry joint versus cold joint
The terms are often used loosely, but a useful distinction is by cause. A dry joint generally stems from insufficient solder or poor wetting, leaving a starved, incomplete connection. A cold joint stems from the solder not reaching full melt and flow, often because the iron or the work was too cold or moved before the solder solidified. Both are present from the moment of assembly, and both tend to degrade further under thermal and mechanical cycling, developing micro-cracks over time.
Finding and fixing them
Dry joints are a classic cause of faults that come and go when a board is tapped, flexed, or warmed. Under magnification look for joints that are dull, cracked, or show a visible gap between solder and pad. The fix is to reflow the joint with the iron at proper temperature, add a small amount of fresh flux-cored solder so it wets fully, and let it cool undisturbed. Clean, well-wetted joints are essential on high-current hashboard and power connections.
For age-related joint failures, see our entry on solder joint fatigue.
In Simple Terms
A dry joint is a soldered connection that never properly bonded to the metal surfaces it joins, usually because too little solder was used or…