Polymeric Potting Relaxation Dynamics in Precision Transducer Packaging
Polymeric potting stress relaxation causes time-dependent zero drift in precision transducers, requiring thermal seasoning to stabilize output baseline.
Moisture Sorption
Absorption Mechanism
Physical process through which a solid substance takes up and retains water from the surrounding air through both adsorption and absorption. Calculating the rate of moisture sorption helps engineers predict the dielectric degradation of electronic potting compounds. This process depends on the vapor pressure of water in the environment and the porosity of the material.
Over time, the accumulated water can change the physical and electrical properties of the substance.
Material Degradation
Presence of water inside an electronic package often leads to corrosion of the metal traces and loss of insulation resistance. High moisture sorption can cause a polymer to swell, leading to mechanical stress on the internal components. This effect is particularly dangerous in high-voltage applications where water can trigger an electrical breakdown.
Monitoring the weight gain of a material is the standard method for quantifying its sorption characteristics.
Environmental Interaction
Diffusion of water molecules into a solid is a temperature-dependent process that follows Fick’s laws. Rapid moisture sorption occurs in tropical environments, while the process is much slower in arid conditions. Protective coatings are often applied to components to reduce the rate of ingress.
However, no polymer is completely impermeable, so the long-term impact of moisture must always be considered in the design.
Measurement Method
Laboratory testing involves exposing samples to controlled humidity levels and measuring the equilibrium moisture content. Understanding moisture sorption is essential for selecting the correct moisture sensitivity level for semiconductor devices. This data allows for the calculation of the shelf life of components before they require baking.
Final verification of the material performance occurs through long-term environmental aging tests.