We've seen before how Spectral Emission Spectroscopy (SEM) is used to determine the composition of the material comprising an Integrated Circut (IC) and how it has various uses from isolating the presence of impurities to allowing the materials to pass government mandated tests for the limiting of hazardous substances such as the "Restriction of Hazardous Substances" (ROHS) certification. There are many different types of spectroscopy. The precise test to be administered depends on the circumstances, the sensitivity required, the materials involved, the cost, the time available and of course, the expertise of the failure analysis engineers present. One of the most useful procedures makes use of a mathematical algorithm known as a Fourier transform and is thus called Fourier Transform Infrared Spectroscopy or FTIR analysis for short.

FTIR Analysis of a Substance

As the name suggests, the test makes use of the infrared spectrum which is much wider than the narrow range spectroscopy we've looked at before. Another significant advantage is that infrared rays can pass unhindered through air - Nitrogen and Oxygen allow these waves to pass through without absorbing frequencies of light which can interfere with the results. This negates the need for performing the tests in a vacuum which is far more convenient and lowers the costs of conducting the tests.

We can also use FTIR analysis testing services to analyze extremely minute samples - even a speck of the material is sufficient to determine its composition. The apparatus is actually very similar to the one used in the famous Michelson-Morley experiments decades ago to determine the variation (if any) in the speeds of light - something that was later explained by Einstein's special theory of relativity. The infrared beams are split into two and by means of a moving mirror, a time delay is introduced which produces an interference pattern. This pattern is then passed through a Fourier transform to provide us with the absorption spectrum of the sample in question.

The spectrum is compared with a known library of samples to figure out the composition. This reference allows us to quickly interpret the results of the experiment. The spectrum consists of what we call "reverse peaks" meaning that there will be sudden dips in the graph which can also be individually analyzed to glean partial information about the composition of the material in case there isn't an exact match in the reference database.

FTIR analysis is therefore convenient and speedy as well as accurate. These kinds of innovative testing services allow failure analysis engineers to obtain more and more accurate information about the chips sent their way and help make them more secure and reliable for all of us.

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