Quantifying Hydrophobic Organosilane Surface Treatment Efficacy in Low Loss Microwave Substrates
Hydrophobic organosilane surface treatments on low-loss microwave substrates suppress moisture-induced Df drift and enable ultra-smooth copper foils.
ATR-FTIR Spectroscopy
Analytical Technique
Infrared light interaction with a surface provides a molecular signature of organic contaminants and polymer structures. Practitioners utilize atr-ftir spectroscopy to identify unknown residues on bond pads after aqueous cleaning or to verify the degree of resin cure in b-stage prepreg materials. The method relies on an internal reflection element (usually a diamond or germanium crystal) that contacts the sample to create an evanescent wave that penetrates only a few microns into the material.
Because the depth of penetration is so shallow, the resulting spectra are highly specific to the surface chemistry rather than the bulk board composition.
Internal Reflection
Light enters the crystal at a specific angle to induce total internal reflection. This physical mechanism allows atr-ftir spectroscopy to capture data from irregular or opaque surfaces that would otherwise block transmission-based infrared analysis. The resulting energy loss at specific wavelengths corresponds to the vibrational modes of chemical bonds such as carbon to oxygen or nitrogen to hydrogen.
Contamination Control
Surface analysis identifies silicone oils or unreacted epoxy components that inhibit solderability or adhesion. When a failure occurs during conformal coating, atr-ftir spectroscopy detects the presence of mold release agents or stray hydrocarbons that cause dewetting. It provides a non-destructive way to verify that a surface treatment has successfully altered the molecular profile of a laminate before subsequent assembly steps.