Capillary Force Propagation Behavior
The capillary spread behavior describes how liquid solder spreads in narrow gaps despite gravity, due to adhesion and cohesion forces. This results in a complete filling of the brazing zone without voids.
Physical-Chemical Mechanism of Action
The solder flows in narrow gaps against gravity because the adhesion force (attraction to the metal) and the cohesion force (attraction to its own material) are stronger than the weight force. This allows continuous spreading of the solder.
Metallurgical Relevance & Welding Risks
Insufficient capillary spread behavior can lead to voids, lack of fill, and poorer mechanical properties of the weld. This increases the risk of cracks and reduces strength.
Workshop Practice & Action Instructions
To ensure good capillary spread behavior, it is important to:
• Keep the braze surface clean and dry
• Use the solder at the correct temperature
• Choose a suitable solder paste or preform
• Allow enough time for the solder to flow