Wave Soldering - Process Monitoring

Process Monitoring

Due to the precise requirements needed for wave soldering, the soldering equipment must be closely monitored. Common tests include visually inspecting boards for signs of problems such as:

Bridging — if the wave is too high or too low then the board will not make proper contact with the wave and it can lead to undesirable bridging, causing short circuits. Ventilation does not affect the boards' quality, but if the ventilation in the machine is poor, the fumes from the flux as it goes through the pre-heat can lead to a fire, in which case a foam or powder extinguisher should be used. Due to the extreme temperatures of the wave when it comes into contact with the water, the water flashes off so rapidly it can cause splashes or solder jumping into the air with heights up to 1 meter or even more.

Smearing — another flux related problem, is caused by not enough flux being applied during the fluxing stage. Solder sticks to the board and causes streaking. Quality assurance often includes a resistance test, to make sure no flux or other deposits cause conduction between traces, halide content tests to check for proper flux activation, and others. In modern equipment, virtually all control of the process is computerized, with little human interaction needed to monitor and adjust the equipment.

Some defects may occur during the soldering process. Cracks occur due to mechanical stress and can cause loss of conductivity. Cavities, the presence of which is also known as porosity, is caused from either contaminated surfaces, lack of flux, or insufficient heating. Decrease in strength and conductivity is the result. If the wrong solder thickness is produced, the product may be susceptible to stress, or too thin for the load placed upon it. This can be caused by the wrong temperature being used or wrong conveyor speed.