During PCBA processing, there are many production processes and many quality problems are prone to occur. At this time, it is necessary to continuously improve the PCBA welding method and improve the process to effectively improve product quality.
1. Improve welding temperature and time
The intermetallic bond between copper and tin forms crystal grains. The shape and size of the crystal grains depend on the duration and strength of the temperature during the welding process. Less heat in the welding process can form a fine crystal structure, thereby forming an excellent solder joint with the best strength. PCBA patch processing reaction time is too long, whether it is due to long soldering time or high temperature or both, it will cause the crystal structure to be rough, hard and fragile, and have high shear strength.
2. Reduce surface tension
The cohesion of tin-lead solder is even greater than the cohesion of water, so the solder is spherical to minimize its surface area (under the same volume, compared with other geometric shapes, the spherical has the smallest surface area to meet the requirements of the lowest energy state ). The effect of flux is similar to that of cleaner on greased metal plates. In addition, the surface tension is highly dependent on the cleanliness and temperature of the surface. Only when the adhesion is much greater than the surface energy (cohesion), the ideal adhesion can be produced. tin.
3. PCBA board dip tin corner
When the eutectic point temperature of the solder is about 35°C higher, when a drop of the solder is placed on the hot-melt-coated surface, a meniscus is formed. To a certain extent, the ability of the metal surface to immerse tin can be evaluated by the shape of the meniscus. If the solder meniscus has obvious undercut edges, shaped like water droplets on a lubricated metal plate or even tends to be spherical, the metal cannot be soldered. Only the meniscus can be stretched to a size less than 30. It has good weldability at small angles.