/How to choose the flux for different welding equipment
The condition of the equipment at the Pcba factory determines the condition of the welding process, and the process condition is the key to selecting the flux. For a simple example, if the peak of the spray is rosin-type flux, it may not be suitable because Higher solids may block the nozzle of the sprayer in a shorter period of time; if the wave soldering of the foam selects a flux that is only suitable for the spray, the foaming effect may not be as good. According to the pcb assembly equipment and process conditions, the flux is selected in the following aspects:
(1), manual tin furnace.
When the manual tin furnace is welded, the flux has both foaming and non-foaming conditions, and manual spraying is rarely seen in mass production. When not foaming, the range of flux that can be selected is wider; when there is foaming process, we should choose the flux with better foaming effect. Whether manual or automatic welding, our standard for better foaming is The same, first: the bubble should be as small as possible, not too large; second: the foam should be evenly sized; third: foam should be as long as possible.
Because the manual tin furnace does not have a preheating process, some rosin-free, no-clean, no-resistance fluxes are generally not recommended to customers. The use of such fluxes may cause tin beads and other undesirableities; if the customer must insist on using it Such fluxes, we recommend to try again after the trial.
(2) Foam wave soldering furnace.
Foaming wave furnace must choose foaming flux. At present, the foaming effect of rosin-type flux is better. The problem of foaming without residue and no-cleaning low-residue flux has been solved. As for the standard of foaming. It has been discussed above.
(3), spray wave soldering furnace.
Spray wave furnace In addition to the flux with high rosin content, there are many types of flux to choose from. It is better to choose a no-clean flux that does not contain rosin. At present, some no-clean fluxes can be foamed or sprayed, and the choice of flux for such a process will not be too much of a problem.
(4) Double wave soldering furnace.
The double wave soldering furnace is mainly used to produce the circuit board with the patch and the plug-in mixed. At this time, the welding surface of the circuit board needs to pass two peaks before and after; the first peak is high (also called high wave or turbulent wave), the main function It is welded to make the component initially fixed; the second peak is relatively flat (also called flat wave or rectified wave), mainly for shaping the solder joint. In this process, the problem often encountered is that when the flux passes through the first peak, the activator or wetting agent is fully decomposed, so when the second peak is passed, the flux has actually started. When it comes to the effect, it is very easy to have problems such as welding and pulling. In order to solve this situation, we recommend that customers use a flux with a slightly higher solid content, activators and wetting agents to withstand high temperatures. At the same time, flux manufacturers often add a compound activator to the flux to solve such problems. And a wetting agent to enable the flux to withstand different temperature segments and still perform its fluxing after the first wave of soldering.
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