Radio Frequency Interconnect Loss Driven by Substrate Dielectric Degradation Mechanisms
Substrate moisture absorption increases dielectric loss tangent, raising RF interconnect insertion loss and reducing long-term wireless link margins.
Epoxy Resin Scission
Meaning
Chemical degradation of polymer matrices involves the irreversible breaking of covalent bonds within the cross-linked network. Epoxy resin scission reduces the molecular weight of the polymer and weakens the mechanical integrity of the circuit board. This process is often localized near heat sources or areas of high electrical stress.
The breakdown of the polymer backbone leads to the formation of smaller fragments and volatile byproducts.
Decomposition Path
Energy from thermal or oxidative sources provides the activation energy needed to sever the chemical bonds. Once epoxy resin scission begins, the physical properties of the board start to shift away from the nominal values. The reduction in cross-link density lowers the stiffness of the material.
Thermal Trigger
Continuous operation at temperatures near the rating of the resin accelerates the rate of bond breakage. Power modules with poor thermal management are particularly prone to this form of aging. The degradation often appears as a darkening of the substrate or a change in the dielectric loss.
System Fatigue
Long-term reliability of an enclosure assembly depends on the chemical stability of its internal components. Boards experiencing epoxy resin scission become brittle and may fail under mechanical shock or vibration. Qualification cycles for automotive electronics include long-duration baking to ensure the resin survives the service life of the vehicle.
Fatigue testing confirms that the structural bonds can withstand repeated thermal cycling without losing their grip on the copper foil.