When everyone uses lead-free solder paste
for homework, there are always a lot of bubbles. Air bubbles in solder joints not only jeopardize the stability of the solder joints, but also increase the probability of component failure. When applying lead-free solder paste, the air bubbles in the solder joints are the heat storage places for electronic devices when they work, and the heat energy generated when the electronic devices work will accumulate in the air bubbles, resulting in the ambient temperature of the solder joints not being able to be output smoothly according to the solder joints. The longer the run time, the more thermal energy is accumulated and the greater the damage to the stability of the solder joint.
In order to better achieve predicted wetting and final interconnects when applying SAC aluminum alloys, the flux in SAC solder paste must operate at higher ambient temperatures compared to flux, and the interfacial tension of SAC aluminum alloys more than tin aluminum alloy. Increased potential to collect volatile organic compounds in molten solder. This volatile organic compound is not easily expelled from the molten solder, so it is difficult to prevent bubbles, but we can remove them depending on the way! Because the general gas reflow welding equipment cannot create a vacuum inside, it cannot reasonably remove CO2 in the furnace and air bubbles inside the solder joint. In order to better avoid the protection of the reflow oven by nitrogen oxides in the solder joints, since the working pressure of N2 is higher than atmospheric pressure, there are many bubbles in the solder joints. How to solve the problem of air bubbles after applying lead-free solder paste?
1. After electric welding, vacuum encapsulation in the gradient direction is carried out in this link before cooling, that is, the vacuum value rises slowly, because the solder is still in liquid state after electric welding. At this time, air bubbles are dispersed in various parts of the solder joint. Vacuum packaging can suck up the surface air bubbles first, and the bottom air bubbles will move up. As the working pressure decreases, the air bubbles will overflow symmetrically. If the gas is vented immediately, there is an explosion in the solder joint.
2. Pre-vacuum. Before heating to lead-free solder paste, the CO2 in the work area should be exhausted to prevent the formation of air oxide film during the whole process of solder heating. Vacuum can also increase the total wetted area.