Humidity effects on electronics causing reliability issues are serious today for automotive electronics, power electronics, and consumer electronics due to the miniaturization and high-level integration in devices, and wide spread use exposing them to harsh climatic conditions. The formation of water layer on the PCBA surface can be looked as the process determining the risk of failure occurrence and the failure mode itself i.e. increase of leakage currents between conduction points on PCBA surface, electrochemical migration, and corrosion. The parameters like solder mask, residues after assembly process, and the type of surface mount components have an influence on the water layer formation on PCBA surface. It makes fundamentally important to understand the influence of the mentioned factors and their relation to the sequential failure development under humid conditions. In this investigation formation of water film on PCBA surface under condensing and hygroscopic conditions are investigated using a special gravimetric set up by weight measurement. Set up allow condensation to occur only on one surface of a test PCB with a known area, therefore the measured weight can be converted to equivalent average thickness. The interdigitated electrode pattern on the test PCB surface allows electrochemical measurements in correlation with water film thickness. This method was able to measure water build up under condensing conditions with an accuracy of about 0.01mg. In this study Water layer thickness has been determined under isothermal and dynamic conditions, with and without the presence of weak organic acid (mimicking solder flux residues from soldering process) as hygroscopic residue on the test PCB surface made of polymer laminate and alumina ceramic substrate. Ceramic substrate was used to compare with polymer substrate in order to understand the water absorption by the polymer laminate. The interdigitated electrode pattern on the PCB surface made of Sn-Cu-Ag alloy was used for electrochemical measurement, while the water film gradually built on the surface. For isothermal testing, temperature of cooling was just above and under dew point to form different levels of water film. For dynamic testing, temperature was varied at a particular rate, which gradually increased the water film thickness. During measurement actual temperature of the PCB surface was recorded. Electrochemical measurements as a function of water film thickness was conducted using both DC and impedance measurements. For DC measurements, a 5 V DC was applied (mimicking an electronic device), while the resulting leak current between interdigitated electrode was measured. Impedance measurements were carried out using 10 mV amplitude over a frequency range of 10^-1 to 10⁵ Hz. Experiment allowed clear correlation between the dew point and/or critical deliquescence/condensation and water layer thickness to the electrical (electrochemical) properties of the water film (leak current and impedance level) causing corrosion failures. A critical level of water film thickness and impedance level was found at which under DC condition cause failure due to electrochemical migration. The data can be correlated to failure prediction during condensation regime for electronic devices. Further the data obtained from these experiments are used for developing electrochemical model using Comsol.