Optimizing Reflow Profiles to Control Initial Intermetallic Compound Thickness
Optimizing reflow profiles keeps initial intermetallic compound thickness between 1.5 and 2.5 micrometers, preventing brittle joint fracture.
Wetting Energy
Meaning
Amount of work required to increase the contact area between a liquid and a solid surface determines the success of a soldering process. Wetting energy represents the thermodynamic drive that causes a drop of liquid to spread out rather than remain a bead. It is determined by the balance of surface tensions between the solid, the liquid and the surrounding atmosphere.
In industrial soldering, a high value ensures that the metal flows into every gap to create a strong bond.
Surface Interaction
Molecular forces dictate the success of the bonding process. Positive wetting energy is achieved by cleaning the surfaces to remove oxides and contaminants. Flux is used in manufacturing to lower the interfacial tension and allow the molten solder to cover the copper pads completely.
Bond Quality
Mechanical strength depends on the complex interaction of molecular forces at the angle where the liquid meets the solid surface. Measuring the wetting energy provides the data needed to predict the reliability of the finished assembly. A low value results in poor adhesion.
This degradation of the electrical path often remains undetected until the product enters the field.
Measurement Protocol
Laboratory testing quantifies the efficiency of different chemical treatments. The wetting energy is often calculated using a contact angle goniometer or a wetting balance.