1 Wetting

When the hot and liquid soldering tin dissolve and penetrate onto the surface of metal, it can be defined as metal wetting. Molecule of mixture of soldering tin and copper can form a new alloy which contains part of copper and part of soldering tin. Molecule bond is the core of welding, it can decide the hardness and quality of soldering point, wetting can take place only on the copper surface which has not yet being contaminated, no oxide film due to exposure under air, at the same time, temperature should reach certain level.

2 Surface tension

Everyone knows the surface tension on the water, this tension can keep the cold water drop remain the same shape on the metal plate with grease, this is because adhesion which tend to make upper liquid expansion on the surface is smaller than its cohesion. Use warm water and cleanser can reduce the surface tension, water can soak the metal plate with grease and flow out to form a thin film, if the adhesion is bigger than cohesion will occur this situation.

Cohesion of TIN-LEAD soldering tin is even bigger than water, which can make the soldering tin as ball shape which can help to minimize the surface size, to satisfy minimum energy state requirement. Flux play the role as cleanser to metal plate with grease, additional, surface tension is highly depends on the cleaning level and temperature, only adhesion power is much greater than cohesion power, reasonable wetting can occur.

3 Alloy metal

Metallic bond among copper and tin can form grain, the shape and size of grain are determined by soldering temperature and lasting time length, hardness. Less heat during soldering can form more deliberate poikilitic texture, to form the best soldering point with hardest strength. Too much reaction time, either extremely time length of soldering or overheat or both will cause crude poikilitic texture.

Comments are closed.