Materials Performance

MAY 2017

Materials Performance is the world's most widely circulated magazine dedicated to corrosion prevention and control. MP provides information about the latest corrosion control technologies and practical applications for every industry and environment.

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49 NACE INTERNATIONAL: VOL. 56, NO. 5 MATERIALS PERFORMANCE MAY 2017 electrical properties of electronic systems used in automobiles, such as the microde- vice that activates the airbag. Variations in air moisture—dry in the summer months of July and August and wet in the winter m o n t h s o f D e c e m b e r a n d Ja n u a r y — strongly increases deterioration. Climate is comprised of several parameters, with RH and temperature being the most important factors that can contribute to corrosion damage of electronic components. Some scientists who analyze deterioration of materials in connection with climatic and environmental conditions consider that operational problems with electronic sys- tems in cars is related to drastic seasonal changes in RH and temperature inside industrial plants, as mentioned in the eval- uation of the automotive industry in Mexi- cali 1 and expressed in ISO 9223. 2 Atmospheric Pollution Gaseous and solid airborne pollutants, including H 2 S and SO 2 , generate aggressive environments in combination with levels of humidity and temperature that are higher than 75% and 30 °C, respectively. This initi- ates the corrosion phenomena that dam- ages metallic components of electronic equipment in motor vehicles. Arid zones, as in Mexicali , present RH that typical ly ranges from 30 to 90% in summer with tem- peratures higher than 40 °C. Winter tem- peratures are lower than 5 °C and RH ranges from 45 to 85% inside the automo- tive plants. The efficiency of the electrical behavior of materials used in the electronic devices is a function of the amount of humidity and pollutants present in the indoor assembly environment. The most active gases are H 2 S and SO 2 . Auger Electron Spectroscopy Technique The Auger electron spectroscopy (AES) technique was used to analyze, at the nanoscale, the corrosion deterioration of the electronic microdevice that controls the motor vehicle's airbag activation. With this technique, it was possible to detect the particles that reacted with the electrical connections of the microdevice and caused † Trade name. FIGURE 1 Correlation analysis of climatic and pollution factors to determine the CR (winter 2014). the electrical failures. Modern microelec- tronic devices and equipment in automo- biles have very complex designs, with mul- tiple operations combined with small size. These devices use specialized materials with corrosion-resistant characteristics. The AES technique was used to evaluate the wide range of materials, layers, sizes, and geometries of the corroded microde- vices. It is necessary to understand the use of this technique so parameters such as applied voltage and current can be con- trolled so layers that are critical to the anal- ysis are not destroyed. The AES technique was also utilized to evaluate new materials, standardize new methods of manufactur- ing, and improve their corrosion resistance and operability of the electronics. Experimental Procedure A mathematical correlation was made using MatLab † software to determine the corrosivity levels in the automotive indus- try's indoor facilities. 3 This analysis, which w a s c o r re l a t e d w i t h c l i m a t e f a c t o r s (humidity and temperature) and air pollut- ants (H 2 S and SO 2 ), determined the deterio- ration grade and corrosion rate (CR) of the corroded connectors in the microdevice used in the airbag system. These climate factors entered the indoor environment from outdoors through inlets or air condi- tioning systems. The Auger spectra of the corroded microdevice were analyzed using the 5-keV electron beam and 10 µA of elec- trical current. 4 The AES spectra show the surface analysis of three points evaluated in different zones of a corroded microde- vice. The spatial resolution of this tech- nique was ~100 nm with a resolution depth of 1 nm. Results Corrosion products between connec- tion points caused failures in electronic systems of the motor vehicles. Specific electronic devices operate at macro- and microscales and are fabricated in dedi- cated, but not isolated, rooms with particu- lar materials and methods selected to resist corrosion. Nevertheless, the absence of environmental controls allowed intru- sion of the corrosive atmospheric factors. In winter, uniform corrosion was promoted by the wetting film formed on the metallic surfaces of some microdevices. In summer, minor tarnishing appeared on components as a result of air pollutants and droplets that adhered to metal surfaces, w hich resulted in pitting corrosion. Corrosivity Level Analysis The corrosivity levels in the Mexicali automotive industr y indicated the pres-

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