What are the reasons for the unsmoothness after lead-free solder paste soldering?

Many people find that the circuit boards after soldering have a granular appearance and are not very smooth when using lead-free solder paste for surface mount. Why is that? Today, the solder paste manufacturer will explain this reason to everyone:

The main reasons for the roughness after lead-free solder paste soldering are as follows:

1, If the solder paste is preheated for too long, some of its components will evaporate, and the solder paste will oxidize during this process. Using such solder paste will result in the phenomenon of particles after soldering. This situation can generally be solved by shortening the preheating time. Reducing the preheating time usually does not exceed2Minutes.  

2If the components are not clean or there are residues on the surface of the circuit board, the solder paste cannot directly contact the circuit board and protrudes. After soldering, it will also produce an uneven phenomenon. In this case, at the very beginning, it is necessary to inspect the components and circuit boards to ensure that the surfaces are clear and clean before starting to use them.

3If the solder paste dries, the soldering effect will also be poor and it will be granular. Therefore, the wettability of the solder paste must be guaranteed.

4The issue of flux.

5Lead-free solder paste should have good wettability. Under normal circumstances, the time that solder stays above the liquid phase line during reflow soldering is30~90The time during wave soldering when the pins to be soldered and the substrate surface of the circuit board come into contact with the wave peak of the solder solution is seconds4After using lead-free solder for about a second, it is necessary to ensure that the solder can exhibit good wetting performance within the above time range to guarantee a high-quality welding effect.

6The electrical conductivity and thermal conductivity of the solder paste after soldering should both be consistent63/37Tin-lead alloy solder is close to each other.  

7.The tensile strength, toughness, ductility and creep resistance of lead-free solder paste solder joints should all be comparable to those of tin-lead alloys.

The above is all aboutLead-free solder pasteThe sharing of the reasons for the roughness after welding, hoping it can be helpful to you. Shenzhen JJY Industrial Technology Co., LTD.15We have been dedicated to the research and development, production and sales of solder for many years, providing customers with a complete set of electronic soldering solutions. For more knowledge about soldering, please keep following JJY Solder Paste Manufacturer and leave a message online to interact with us.