Exploring water and ion transport process at silicone/copper interfaces using in-situ electrochemical and Kelvin probe approaches

Abstract

In general, packaging materials which encapsulate light emitting diodes (LEDs) and microelectronic devices offer barrier protection against several environmental hazards such as water and ionic contaminants. However, these encapsulants may provide pathways for water and ionic contaminants to reach the metal/polymer interfaces and provoke local corrosion of electronics, which is a major reliability concern for polymer encapsulated LEDs and microelectronics. As the water and corrosive constituents play a crucial role in their reliability, water uptake kinetics, interfacial ion transport and delamination behaviour of silicone coated copper model system, mimicking a typical microelectronics packaging system, is explored in the present work. Electrochemical impedance spectroscopy (EIS) integrated with attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy studies revealed that water diffusion inside the silicone network is Fickian in nature and the evolution of the observed time constants are related to the diffusion and interfacial reactions. A decrease of impedance magnitude with time was observed in EIS measurements concurrently with water absorption bands shifting towards lower wavenumber in ATR-FTIR measurements, implying the growth of strong hydrogen bonding between water molecules and the silicone network. The estimated diffusion constant of water using the capacitance method was in the order of 7 × 10 -12 m 2 s −1 and the water absorption volume fraction was in the range of 0% to 0.30%. Scanning Kelvin probe studies elucidated the ion transport process occurring at the silicone/copper interface in a humid atmosphere. The interfacial ion transport process is controlled by the interfacial electrochemical reactions at the cathodic delamination front and the estimated average delamination rate is 0.43 mm h -1/2 . This work demonstrates that exploring ion and water transport in the silicone coating and along the silicone/copper interface is of pivotal importance as part of a detailed reliability assessment of the polymer encapsulated LEDs and microelectronics.

Corrosion Protection in Chloride Environments of Nanosilica Containing Epoxy Powder Coatings with Defects

“…45 On the other hand, the regions located at a certain distance from the defect always have a high potential value, slightly positive, which corresponds to the intact metal under the still adherent coating. 42,48 For steel with defective epoxy coatings, other authors have identified the cathodic behavior with potential values of about −200 mV vs SHE. 45 Between these regions, an intermediate one appears, corresponding to the cathodic activity under detached coatings.…”

“…In the present study, the location of the delamination front is determined by the first derivative of the potential, following the method explained in other works. 47,48,50 From graphics such as those in Fig. 5, the location of the delamination fronts has been calculated and its average advance for the different types of coatings under study is plotted in Fig.…”

“…The position of the delamination front is quantified considering the criterion established in previous studies. 47,48 Corrosion immersion tests.-Steel samples with defective and non-defective coatings -of the 3 types under study-were immersed in 3.5 wt.% NaCl solutions at room temperature. To prepare the defective coatings, artificial defects were made, using a sharp tool with a 1 mm wide blade (as that proposed for making scribes in ASTM D1654 standard).…”

Detection and quantification of defect evolution at buried metal-oxide-polymer interface on rough substrate by local electrochemical impedance mapping

“…Moreover, they could irreversibly modify these mechanisms. For these reasons, the development of in situ methods able to understand the evolution of metal-oxide-polymer interfaces during degradation attracts more and more attention [11,16,17,18,19,20].…”