1. It is said that it is due to the solvent in the formula of the flux in the lead-free solder paste. It is true. If the flux used to produce solder paste is volatile

Of course, the solder paste will dry out slowly during use. However, there are too many factors for the dryness of solder paste, and the dryness of solder paste is due to the instability of the flux system.

Of course, to find the reason, we should start with the flux itself. The reasons are as follows:

1. Solvents, such as alcohols as solvents, the flux may become viscous and then dry before it is made into lead-free solder paste. To take an extreme example: with ethanol (experiment it), it can be said that the solvent is the main reason.

2. Rosin, the proportion of rosin in the flux is the second largest. If it is unstable, it will directly affect the stability of the flux.

3. Thixotropic agent, the amount of thixotropic agent added is not small. It plays the role of emulsifying flux in it, and generates thixotropy through emulsification, so as to ensure that the solder paste can always restore thixotropy during reuse. If the viscosity becomes larger, it will feel

Feel the solder paste is dry, it is hard.

4. Organic acids, antioxidants, active agents, etc. These things are added in small amounts but can be said to have the greatest effect. If they continue to react with each other, the natural solder paste is unstable and becomes unstable. Dry is possible.

2. There are many reasons for the dryness of lead-free solder paste, such as poor formula, inappropriate ambient temperature and humidity (the temperature is too high, and the solvent evaporates quickly. If the humidity is too high, the solder paste will absorb water, which will interact with the rosin in the solder paste to make it dry. Dry) If you think about it from the perspective of the formula, it is generally not because of the use of alcohols. Indeed, there are many solder pastes that use alcohols, but it seems that I have never seen ethanol, and more ethers are used. up. The wettability of leaded solder paste is better than that of lead-free solder paste. This is determined by the metal. There is no way. To achieve the same soldering effect, the only way to achieve the same soldering effect is to work hard on the solder paste, that is, to enhance the activity of the lead-free solder paste. This will increase the corrosion of the solder paste on the surface of the tin powder, increase the surface area of the tin powder, increase the viscosity, and in serious cases, it will dry out. But in general, this problem has been solved now, especially the solder paste with halogen, basically it will not be like this!