Wave Soldering Defects
Poor Penetration on a Printed Circuit Board
For a solder joint to form on the topside of a board, flux needs to be present in the plated through holes. The temperature of the topside of the board needs to have reached a minimum of 100-110°C. The most common process problem today with no clean is limited flux application. It is generally uncommon to have problems with through hole plating provided a board manufacturer's products are evaluated prior to use. It is also firmly uncommon to have contamination in the through hole causing this sort of problem. If flux penetration is present and correct pre-heat obtained then have the printed board tested.
Figure 1: Poor penetration is caused by either inadequate flux application or inadequate pre-heating.
In Figure 2, the solder has failed to fill the plated through hole on one side of the component. The solder has wetted the PCB, but failed to fully wet the component lead, which is more likely to be flux related. If the fault is with the process conditions, there should be other positions on the board that have a similar problem. Simple solderability testing of the board and component termination should indicate if the fault is process or material related.
Figure 2: Poor penetration here is likely to be flux related.