What are the Causes of Short Soldering?
Some Engineers, Technicians and Operators of Wave Soldering machines ask me:
What are the reasons that generate many welding shorts in the process of Wave Soldering, and I imagine, maybe this is one of the problems of several other people working in this area in other companies, so I will share some points that I think are important to be observed, as these can contribute to the occurrence of these defects.
- Type of Flow Used (It is essential to read the manufacturer’s recommendations);
- Conveyor angle (In accordance with the type of the solder bath alloy);
- Solder Pot Contamination (Chemical Composition of the Solder Bath);
- Welding Pot Temperature (In accordance with the type of the weld bath alloy);
- Mechanical Adjustment of the Cascade Fall;
- Pump Speed Adjustment;
- Thermal Profile (Profile);
It is important that the Flow is performing its function, that is, we must preheat correctly, as determined by its manufacturer so that it is “activated”, in case it is burning all its activators during the preheating phase when arriving at the weld, the points to be covered by welding, should already be in the “re-oxidation” phase, contributing to generate the weld shorts.
The angle of the conveyor is directly related to the welding alloy, ie Sn / Pb (6th nominal), or Lead-free (4th nominal).
The analysis of the Weld Bath must be carried out periodically, according to the frequency of the use of the equipment, in order to ensure that the chemical composition of the weld alloy does not have contamination above the allowed; the manufacturer of the welding rod can perform this analysis and provide a technical report.
The temperature of the Solder Pot is one of the first factors that call our attention.
If the temperature is too low, it means that the weld viscosity at the end of the wave cascade will also be high.
During the contact of the PCB with the Solder, 100% of the terminals and tracks are short, which means that we depend on some factors, such as the law of gravity, for the shorts to be undone.
The mechanical adjustment of the Wave Nozzle (Nozzle Wave) cannot generate a cascade with little drop at the exit, just as it cannot be with too much drop.
Adjusting the Pump speed should provide a smooth drop of the wave cascade. Each piece of equipment has a value of this parameter and depends on the maintenance of the turbine.
The thermal profile of the pre-heating must be distributing the temperature in the PCB in such a way that the Flow can be activated effectively.
Remember, the items listed above are not exhaustive, but they are largely the first ones that, if not observed, maybe the cause of many shorts. Therefore, having control of these items can mean zero defects in the DPKU indicator.