Molecular Identification
Infrared radiation absorption allows for the identification of organic compounds and contaminants by measuring energy levels across a range of wavelengths. In board fabrication, fourier transform infrared spectroscopy detects residual oils or mold release agents that interfere with wire bonding. The resulting spectrum acts as a unique fingerprint for functional groups such as carbonyls or hydroxyls.
This capability allows for the rapid identification of unknown substances on the copper surface.
Spectral Processing
Interferometers split the light beam into two paths to create a pattern that contains information about all frequencies simultaneously. The implementation of fourier transform infrared spectroscopy uses a mathematical algorithm to convert raw data from the time domain into the frequency domain. This transformation produces high-resolution spectra with a high signal-to-noise ratio.
Modern systems use attenuated total reflectance to sample the board surface without destructive preparation. This non-destructive approach preserves the assembly for further electrical testing or cross-sectioning. Carbon dioxide and water vapor are digitally subtracted to ensure the accuracy of the organic profile.
Contamination Control
Cleanliness standards for medical or military electronics require the absence of specific chemical residues. Use of fourier transform infrared spectroscopy during failure analysis pinpoints the presence of silicone or flux activators in areas showing poor adhesion. Once the contaminant is identified, the production team modifies the cleaning cycle to eliminate the source.
