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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50 MAY 2017 MATERIALS PERFORMANCE NACE INTERNATIONAL: VOL. 56, NO. 5 industry has been increasing during the last five years. Thi s corrosion process involves the formation of galvanic electro- chemical corrosion cells, which have been found to cause electrical failures during testing. Cu is the most common material used in th e electronic control devices because of its good electrical and thermal conductivity ; however, the copper micro- circuits, electrical connectors, and connec- tions are very susceptible to atmospheric corrosion under the conditions found in Mexicali. The formation of corrosion prod- ucts on the surfaces of copper connectors is a particular concern because it can result in poor electrical contacts that fail to prop- erly conduct the necessary current/signal to a component. In most cases, companies are not famil- i a r w ith th e p h e n o m e n o n (o r c o n s e - quences) of corrosion, until it causes a fail- ure in electronic devices or equipment and interrupts the manufacturing process. This case history is one such example, which helps to demonstrate the value of environ- mental control for indoor facilities. Acknowledgments The authors thank the companies of the Mexicali automotive industry for the sup- port received for research and the informa- tion supplied to the study. References 1 G. Lopez Badilla, "The Characterization of Corrosion in the Electronics Industr y of Me xi cali ," D o ctoral th e si s, Univ ersi d a d Autónoma de Baja California, 2008. 2 ISO 9223:1992, "Corrosion of metals and alloys—Corrosivity of atmospheres—Classi- fication" (Geneva, Switzerland: ISO, 1992). 3 E.B. Magrab, et. al, An Engineer's Guide to MatLab, 2nd ed. (Upper Saddle River, NJ: Prentice Hall, 2005). 4 A.E. Clark, C.G. Pantan, L. Hench, "Auger Spectroscopic Analysis of Bioglass Corrosion Films," J. Am. Ceram. Soc. 59, 1 (2006): pp. 37- 39. Bibliography 1999 ASHR AE Handbook: HVAC Applications. Atlanta, GA: ASHRAE, 1999. Asami, K. and K. Hashimoto. "AES Study of the Corrosion Behavior of Metallic Surfaces." Corros. Sci. J. 39, 1 (2007): pp. 95-106. TABLE 1. ATOMIC CONCENTRATIONS (%) AT THE TEST POINTS Elements Point 1 Point 2 Point 3 C 10 12 8 Cu 19 18 16 N 6 8 8 O 22 20 17 S 13 13 21 Si 11 10 11 Sn 4 5 7 FIGURE 2 Corrosion products analysis of a corroded microdevice with: (a) Auger map and (b) AES spectra (winter 2014). ence of an aggressive environment. The CR calculated from the atmospheric pollution in the indoor facilities indicated that the air pollutants caused damage to the metal- lic surface within the microdevices and prevented effective airbag deployment. The macro- and microelectronic systems of the automobiles corroded rapidly in the high- humidity environment. Figure 1 shows the ranges of RH and temperature correlated with the concentration levels of SO 2 , the dominant air pollutant. The RH and tem- perature in the winter months ranged from 30 to 75% and 20 to 35 °C, and the annual CR ranged from 30 to 100 µg/m 2 . These were the largest seasonal CRs. Auger Electron Spectroscopy Examination The AES analyses determined the cor- rosion products formed on the metallic surfaces of the damaged micro devices. Fig- ure 2(a) shows the map of the AES image of the deteriorated zones of the microdevice. Three principal points were selected for evaluation with the AES technique. Figure 2(b) presents the spectra of the AES analy- sis. The plots in Figure 2(b) were drawn using Sigma † software. The AES map indi- cat es th e ch emical c omp ound s in th e selected points are composed of the main corrosive ions present on the metallic sur- faces. 4 The principal metals identified on the surfaces are Cu attached to Sn. The atomic concentration (%) of the chemical elements in each spectrum is listed in Table 1. The concentration percentages in Table 1 represent the chemical elements that comprise the corrosion products, which are primarily derived from the H 2 S and SO 2 pollutants. Summary This study was initiated to determine why a system failed to deploy an airbag during testing. Modern advances in elec- tronic components have resulted in the d e v e l o p m e n t o f m u c h s m a l l e r u n i t s ; h o w e v e r, t h a t a l s o m e a n s t h e m u c h - smaller conductors and connectors are less tolerant of corrosion. Factors contrib- uting to c orrosion include th e unc on- trolled climates that intrude on indoor environments. As a result, corrosion in microelec- tronic devices used in the automotive † Trade name. MATERIALS SELECTION & DESIGN

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