Residual Gas Analysis & Out Gassing

Out Gassing	Mass Spectrometry
Infrared Spectrometry	FTIR Analysis
Surface Analysis	Electron Microscopy (SEM/EDS & TEM analysis)
Contaminant Identification	Electrochemical Analysis
Sensor Development

Residual gas analysis (RGA) is a high vacuum, or ultra high vacuum technique, in which a mass spectrometer is used to detect leaks and out-gassing. These devices can do the same job as a helium leak detector, and much more. Mass spectrometers use the difference in mass-to-charge ratio (m/e) of ionized atoms or molecules to separate them from each other. Mass spectrometry is therefore useful for quantitation of atoms or molecules and also for determining chemical and structural information about molecules. Molecules have distinctive fragmentation patterns that provide structural information to identify structural components. The general operation of a mass spectrometer is:

• Create gas-phase ions,
• Separate the ions in space or time based on their mass-to-charge ratio,
• Measure the quantity of ions of each mass-to-charge ratio.

Matco Associates' RGA system is a computer software controlled quadrupole mass spectrometer, capable to 200 atomic mass units, with automatic start-up and shut-down, and with a built-in Pirani gauge and ion gauge. The Pirani gauge and ion gauge constantly monitor from atmospheric pressure to ultra high vacuum and regulate and protect the RGA. It is interfaced to a vacuum system consisting of a mechanical pump for roughing and a diffusion pump for high vacuum. The operating range of the vacuum system is 10-5 to 10-6 torr. The gas content can be analyzed from a metered input port. Alternatively, a specially designed internal mechanical attachment allows for the breaking or cutting of the material to be analyzed for out-gassing products in-vacuuo.

The RGA system can also be interfaced to a Fourier transform infrared (FTIR) spectrometer. FTIR spectrometers record the interaction of infrared radiation (light) with experimental samples, measuring the frequencies at which the sample absorbs the radiation and the intensities of the absorptions. Determining these frequencies allows identification of the sample's chemical makeup, since chemical functional groups are known to absorb infrared radiation at specific frequencies. This is particularly useful for the identification of organic chemical vapors, which may be entrained from the RGA system into the FTIR spectrometer by use of a nitrogen carrier gas stream.

This RGA problem-solving technology has been successfully applied at Matco Associates as described in the following case study. One of Matco Associates' clients manufactures a light-weight rigid insulation material which is composed of microscopic sized sealed glass cells. Previously, the client had analyses of the gases contained in the individual cells conducted by gas chromatography. The gases included hydrogen, carbon monoxide, carbon dioxide, hydrogen sulfide and carbonyl sulfide. Matco Associates was requested by the client to develop an improved and more sensitive analysis procedure. Matco's RGA system was employed and the capability of the RGA system was shown to measure gas concentrations down to the level of 10 parts per million (PPM).

Other applications of the RGA system are under development, including an application where a client has been experiencing the manifestation of a hazy appearance, due to microscopic bubble formation, in an epoxy clear coat. The objective will be to perform an analysis of the gases found in the bubbles to determine the nature of the bubbling phenomenon.

Several other applications of RGA are available. In order to eliminate failures in microelectronic components caused by chemical reaction (corrosion), the internal gas composition of the component must be known. MIL-STD-883, Method 1018.3 is generally the accepted specification for internal water vapor content. This method defines procedures for RGA equipment calibration and device testing, as well as the maximum acceptable limits for water vapor content. Also, samples of process atmospheres and unusual sealing and packaging environments can be analyzed to detect the evolution or re-sorption of gases. In addition to providing routine RGA analyses, Matco Associates has the technical expertise to identify the origin of the problem gases and provide solutions.