Soldering Problem Repair & Prevention (Part Two)
In our previous post we looked at some common issues that arise when soldering. Let’s take a look at some additional solder joint problems and options for prevention and repair.
Insufficient wetting of the solder pad, which can be caused by a dirty circuit board or failing to apply heat to both the pad and pin, leads to weak and unreliable bonds. Repair a solder joint with insufficient pad wetting by placing the soldering iron tip at the base of the joint until the the solder flows and fully covers the pad. You can prevent insufficient wetting by thoroughly cleaning the board and evenly heating the pad as well as the pin.
Insufficient wetting of the pin results from failing to apply heat to the pin; the solder is not given enough time to flow, either. Use the same technique as above to repair poorly heated pins, ensuring that the tip of the soldering iron touches both the pin and the pad. Again, even heating will prevent insufficient wetting. Use these repairs and preventative measures on insufficiently wetted surface-mounted components as well.
As the name implies, a solder-starved joint doesn’t have enough solder for a solid connection. Although it may make good electrical contact, it’s difficult to verify by eye. Regardless, a solder-starved joint will be weak and can eventually develop cracks, which may lead to failure. Repairing a solder-starved joint is a straightforward affair: reheat the joint and add additional solder.
Excessively long leads can bend and touch each other which in turn can cause a short circuit. Simply trim all your leads to the top of the solder joint to correct this problem.
Sometimes two solder joint melt together and form an accidental connection. In some instances you can repair a solder bridge by drawing off excess solder with the soldering iron tip. Alternatively, you can use a solder sucker or desoldering wick if there is far too much solder. You can prevent solder bridges by avoiding using just enough solder for a good electrical connection especially when two joints are in close proximity.