Solder balls are small, melted beads that can form on a printed circuit board after surface mount device (SMD) soldering. Typically, solder balls are found on SMD components and lightly adhere to the solder mask of the boards.

Solder balls are undesirable as they can detach quickly, leading to short circuits and other malfunctions.

 

Considering temperature fluctuations and vibrations during use, solder balls can also detach later, posing a potential cause for unforeseen failures after the commissioning of an assembly.

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Solder balls usually form when too much solder paste is applied to the SMD pads, or when solder paste is applied to the solder mask of the printed circuit boards. Possible causes include:

- Defective paste stencil: Stencil too thick or pad openings too large in the stencil.
- Offset during printing: Offset can cause solder paste to be pressed onto the solder mask.
- Incorrect settings during jetting: Too much solder paste can be applied during jetting. Also, during jetting, solder paste may reach the board's solder mask if the dosage is not precisely aligned or if the dosed amount for the pad is excessive or the diameter is too wide.