There is a set of PCB Assembly process that must be strictly followed in order to produce good output. These processes should not be interchanged and must be monitored. But even if the processes are followed, there are still select problems encountered when an assembled PCB is inspected. Below are some of the PCB Assembly anomalies encountered on an assembled PCBA and its corresponding solutions / occurrence prevention:

Side overhang is a PCB Assembly anomaly that shows one side of a component pad mounted away from the PCB pad. It is considered a defect if >50% of the component pad is mounted away from the intended PCB pad. This phenomenon is possibly due to incorrect placement by automatic placement machine, excess volume of solder paste printed on the PCBA or physical interference of the component prior reflow process. To solve this problem, revisit the program of the automatic placement machine.

There could be manual intervention on the component. Check whether the pad has presence of solder paste disturbance. If there is and is only concentrated on the area where there is a missing component, check the pick and place program. If not, there is an outside interference (either human or other machine/tool)

3. PCB Assembly anomalies – BGA voids

Voids are a PCB Assembly anomaly wherein hollow areas within solder pad are present forming non-contact between pad of the BGA component and the PCB. Voids > 25% of the pad diameter is considered a defect. There may be cases that a void is inevitable (due to various reasons), but to lessen the diameter of the voids, one must optimize the reflow profile in accordance to heating requirements of the BGA component.