What is De-wetting
De-wetting is a phenomenon where molten solder paste initially coats a surface but then recedes, resulting in irregularly shaped globules of solder separated by areas covered with a thin solder film. This occurrence is considered undesirable as it can lead to issues with solder quality and solder joint reliability.
Several factors can contribute to de-wetting. These include pollution of the basic metallization, separation of the basic metallization, and unsuitable soldering parameters such as temperature. Additionally, changes in the surface of the pin, such as bending, can also affect the wetting properties and contribute to de-wetting.
De-wetting can manifest in various scenarios, such as on the contact areas of components after a wetting test, at the pins of components for through-hole mounting, or on the upper contact area of a ceramic multi-chip (CMC) after wave soldering. In all cases, the presence of de-wetting indicates a weak or no bond at the interface, compromising the integrity of the solder joint.
To identify and address de-wetting issues, thorough analysis and investigation are necessary. Techniques such as surface and cross-sectional observation using optical and scanning electron microscopes, energy dispersive X-ray (EDX) analysis, X-ray observation, and Fourier Transform Infra-Red (FT-IR) analysis can be employed.