Analysis of micro samples using the stand-alone FT-IR ... - Bruker

Application Note AN # 100Analysis of micro samples using thestand-alone FT-IR microscope LUMOSIntroductionFourier-Transform-Infrared (FT-IR) microscopy is a wellestablishedmethod for the analysis of samples that aretoo small or complex to be measured in a standard IRspectrometer.With FT-IR microscopy it is possible to obtainan IR-spectrum anywhere on the sample with a very highlocal resolution and thereby revealing the chemical compositionof an extremely defined part of the sample. Thereforethis technique is a useful tool for quality control, forensicand biomedical applications to name only a few. Since it ispossible to analyze a large variety of different samples likefibers, paint chips, contaminations or composite materials(e.g. laminates, tablets) there are numerous possible applications.For instance it is of interest to determine the chemicalcomposition of different layers in a packaging materialand to identify particles found on an electronic componentor impurities localized in a rubber material.So far most of the commercially available FT-IR microscopesare rather bulky and need an additional FT-IRspectrometer. Furthermore they are quite complex to useand require a high level of skill. With the new FT-IR microscopeLUMOS Bruker offers a fully automated stand-alonesolution that is very easy to use and requires little lab space.The OPUS software is a powerful but comfortable tool aswell for the measurement procedure as for evaluation andvisualization of the resulting data.Figure 1: LUMOS stand-alone FT-IR microscopeInstrumentationThe FT-IR microscope LUMOS is an all in one solution withan integrated spectrometer, a high degree auf motorizationand a dedicated user-interface. It is utilizing state-of-theartoptics for optimal sample visualization and infrareddata collection. Its 8x objective provides the measurement

Contaminations have a negative impact on the productquality; especially in the field of microelectronics impurimodesATR, transmission and reflection and high qualityvisual inspection capabilities. The innovative motorizedAttenuated Total Reflectance (ATR) crystal allows performingthe complete measurement procedure fully automatedincluding background and sample measurements. Toprovide perfect contact to samples ranging from soft tovery hard the ATR-device offers three pressure steps andis equipped with a precise internal pressure control. Thebuilt in PermaVac Mercury-Cadmium-Telluride Detector(MCT) ensures a maintenance free operation and lownoisespectra. A high working distance and a comfortablefield of view of 1.5 x 1.2 mm are facilitating the sampleinspection. In combination with a motorized stage, fullyautomated mappings can be performed. Additionally formaximum performance and convenience the LUMOSincludes amongst others:• A motorized ATR crystal, motorized transparent knifeedge apertures and condenser• Automatic change of numerical aperture between IRand VIS• Two LED sources for transmission and reflection• A CCD camera with 4x digital zoom• Electronic recognition of sample plates• Optionally a motorized stage with a position accuracyof 0.1 µm• Optional macro accessory that allows to use all QuickSnap sampling modules from the compact FTIRspectrometer ALPHAThe user is guided through the whole measurement procedureby the dedicated OPUS Video-wizard, a user interfacethat always provides the appropriate functions for thecurrent measurement step. Figure 2 shows the functionbar on the left side during the setup of the measurementpositions; with the Back button it is always possible toalter previous settings at will.Figure 2: Video-wizard – Setting of measurement positionsApplication example:Identification of a contamination on a SMD choke.Figure 3: Visual image of one of the contacts of the SMD-choke. Theinset shows a standard camera image.ties are an important topic. Since electronic devices aregetting smaller and smaller they are also becoming moreand more vulnerable to all kinds of contaminations: Asurface mounted device (SMD) which is contaminatedcan eventually not be soldered anymore and is a potentialsource of leak currents. In a more complex electronic elementeven a small grain of dust can have dramatic effects;most probably the element will not work at all.In order to eliminate the source of the contamination it isvital to know its chemical nature. Using FT-IR microscopycontaminations in the low micrometer range can be identified.As an example we show the analysis of a contaminationon the soldering contact of a SMD-choke (see figure 4). Thechoke has a footprint of about 3.0 x 2.5 mm and a heightof ca. 2 mm. Upon inspection with the visible objective ofthe LUMOS a series of black spots is visible on one of thecontacts.To analyze both the spots and their environment a line-mapwas measured in the reflection mode including two of theblack spots. Altogether twenty spectra were measured ina consecutive row as shown in figure 4. Due to prominentamide I and II bands in the spectra measured on the spotsit was obvious that the unknown substance is some kindof protein, a fact that was also supported by the result ofa library search. Consequently to quantify the degree ofcontamination the amide I band between ca. 1710 and1580 cm -1 was integrated and the results were graphicallyplotted over the visual image. It is evident that the highestconcentrations of the protein can be found on the blackspots. With the gathered information it is now much easierto remove the contamination source.