This phrase, “ball soldering”, has been used to describe physical arrangements other than the one about to be described, but that's the phrase I'm going to use. However!! If the wires under discussion ...

Electronic devices continue to shrink in size with advancement in chip fabrication technology. Packaging technology has responded with improved formats to present these chips for assembly to PCBs.

The physical characteristics of lead-free solder impose new defect types that test and inspection techniques must address. For example, lead-free solder's higher melting point and reduced wetting, ...