1：Experimental Design and Method Selection:

The methodology is based on AFM technique, utilizing contact mode for local electrical measurements including impedance imaging, impedance spectroscopy, and dc current mapping to assess protective properties of conformal coatings.

2：Sample Selection and Data Sources:

Two commercially available epoxy-coated electronic printed boards were used—one in as-received state and one after six-year service in industrial conditions. Samples were selected based on their state to compare intact and degraded coatings.

3：List of Experimental Equipment and Materials:

AFM system (SPM Ntegra Aura by NT-MDT Co.), diamond-coated AFM tip (DCP20 by NT-MDT), Parstat 2,236 workstation for impedance spectroscopy, and software (Nova by NT-MDT Co.) for data processing.

4：Experimental Procedures and Operational Workflow:

AFM scans were performed in dry conditions without electrolyte, with a maximum scan area of 8100 μm2, scanning frequency of 1 Hz, and contact force of 6 μN. Impedance imaging used a 3 kHz sinusoidal voltage at 2 V amplitude; impedance spectroscopy used frequencies from 0.1 MHz to 1 Hz with 100 mV RMS perturbation; dc current mapping used a 20 mV bias voltage. Measurements were taken at multiple spots on copper conductor tracks.

5：1 MHz to 1 Hz with 100 mV RMS perturbation; dc current mapping used a 20 mV bias voltage. Measurements were taken at multiple spots on copper conductor tracks. Data Analysis Methods:

5. Data Analysis Methods: Data were analyzed using Nova software to correlate topographical images with electrical measurements (ac current amplitude, impedance spectra, dc current maps) for identifying and localizing defects.