The Effect of Oxygen on the Surface of Solder * Available to Purchase

The effects of oxygen on solder surface tension, wetting time and surface damping are presented. Oxygen levels greater than 10 ppm lower surface tension, increase wetting time and increase surface damping. Decreased surface tension leads to higher misalignment defects in reflow soldering, but can lower the incidence of dewetting. Increased wetting times can increase non‐wetting defects in both wave and reflow soldering, especially when using no‐clean fluxes. Increased surface damping can lead to lower bridging rates in wave soldering, provided that the oxygen level and flux levels are properly balanced. Choosing the optimum oxygen level for production soldering is trade ‐ off between the stability and the versatility of the process. The most stable soldering processes will be those performed in an inert atmosphere with less than 10 ppm oxygen.These processes are insensitive to variations in soldering machine operating parameters (i,e. a larger process window).This is most desirable for manufacturers soldering large volumes of a given circuit board. The soldering process can be optimised by optimising the circuit board design. The most versatile soldering processes will be those performed in an inert atmosphere with controlled addition of oxygen in the range of 100 ppm to 10,000 ppm (1%). This will be most desirable to manufacturers soldering short runs of a large variety of circuit boards. The soldering process is best optimised by controlling the soldering machine operating parameters (oxygen, flux, preheat, conveyor speed, etc.).