the corrosion of electronic resistors

666 IEEE TRANSACTIONS ON COMPONENTS AND PACKAGING TECHNOLOGIES, VOL. 30, NO. 4, DECEMBER 2007

The Corrosion of Electronic ResistorsMichael Reid, Jeff Punch, Claire Ryan, John Franey, Gustav E. Derkits, Jr., William D. Reents, Jr., and

Luis F. Garfias

Abstract—Precision thick chip resistors are used in a variety ofdifferent industries, from telecommunications to automotive elec-tronics, and as such can be exposed to mild and aggressive cor-rosive environments. This paper investigates the corrosion perfor-mance of two generic precision thick chip resistors in a controlledcorrosive atmosphere consisting of 60 C, 4 ppm H2S and watervapor in purified air. The resistors were exposed in an environ-mental chamber for periods of 5, 10, 15, 30, and 60 days. Followingexposure, the samples were cross sectioned and subjected to sur-face analysis using microscopy and microanalysis. After the ini-tial stages of exposure, corrosion was observed on only one of thetwo types of resistors. The corrosion developed because H2S gasand water vapor diffuses through the thin protective organic layeron the resistor, and subsequently reacts with the silver conductorlayer. Corrosion was facilitated by poor overlapping of the solderand nickel layer and, in particular the glass binder over the glassovercoat, which allowed silver and sulphur to diffuse along theinterface. In addition, this poor overlapping allowed contact be-tween the nickel layer and the silver layer resulting in the devel-opment of an electrochemical corrosion cell. The main corrosionproducts that developed were silver sulfide (Ag2S) and nickel sul-phur residue.

Index Terms—Atmospheric corrosion, precision thick chip resis-tors, printed circuit board (PCB), silver sulphide (Ag2S).

I. INTRODUCTION

I N order for electronic components to function to specifica-tion, reliability of device packaging is crucial. Failures of

electronic components and packages not only cause the mal-function of the devices themselves but also sometimes lead tocatastrophic failure of whole systems [1]. Of all microelectronicdevice failures, corrosion related mechanisms are estimated tobe responsible for more than 20% of them [2].

Surface mount thick chip resistors are often considered to bethe simplest and most inexpensive amongst all of the compo-nents used in electronic circuits and systems [3]. However, re-sistor failures in some systems are often responsible for com-plete functional breakdown. Typically, resistor failure modes in-clude open circuits, resistive shorts or variations in resistance

Manuscript received June 28, 2006; revised January 10, 2007. This work wassupported by the Science Foundation of Ireland under Grant 03/CE3/I405. Thiswork was recommended for publication by Associate Edior L. Nguyen uponevaluation of the reviewers comments.

M. Reid, J. Punch, and C. Ryan are with the CTVR, Stokes Institute,University of Limerick, Limerick, Ireland (e-mail: [email protected];[email protected]; [email protected]).

J. Franey, G. E. Derkits, Jr., and W. D. Reents, Jr. are with Alcatel-Lucent,Bell Laboratories, Murray Hill, NJ 07974 USA (e-mail: [email protected]; [email protected]; [email protected]).

L. F. Garfias is with S.C. Johnson & Son, Inc., Racine WI 53403 USA (e-mail:[email protected]).

Color versions of one or more of the figures in this paper are available onlineat http://ieeexplore.ieee.org.

Digital Object Identifier 10.1109/TCAPT.2007.901749

Fig. 1. Anatomy of a standard mount chip resistor [3].

indicating intermittent failure. The physical condition and elec-trical characteristics of a resistor may provide significant infor-mation about the root cause of a failure. This study focuses onthe corrosion-related failure of precision thick chip resistors,Fig. 1 demonstrates a view of the main elements of a chip re-sistor [3]. Typically, the basic elements of the resistor are: a ce-ramic substrate; wraparound terminations; a resistor element be-tween the terminations (typically made of Ag); a glass overcoatover the resistor element and a polymer coating over the glassovercoat. As illustrated in Fig. 1, the wraparound terminationsgenerally comprise three layers: a conductor layer on the inside;a solder layer on the outside; and a protective barrier [typicallynickel (Ni)] between the conductor and the solder layer. Thewraparound (termination) acts as a low resistance interconnectbetween traces on a printed circuit board (PCB) and the resistorelement. In addition a thin conformal organic epoxy layer is typ-ically applied to the resistor in order to impede the corrosion ofthe resistor by limiting the diffusion time taken for the watervapor and pollutant gases to reach the resistor surface. Due tothe high demand of surface mount thick chip resistor compo-nents, numerous different resistors are commercially availablewith a variety of designs. The scope of this work is to examinethe failure mechanism of two precision thick chip resistors withdistinctly different designs, which are, representative of currentresistor designs in printed circuit board assembly and subjectthe resistors to a well-defined corrosive condition over a 60 dayperiod.

Corrosion can lead to failure in a resistor device by reactingwith or removing the conductive material of the resistive el-ement or device terminations, thereby leading to an increasein resistance. The literature reports that mainly, silver (Ag) re-acts with sulphur (S) to form a non-conductive silver sulphide(Ag S) thick film which can then lead to open-circuit some orall of the resistive elements in a resistor [4]. Hydrogen sulphide(H S) and high levels of relative humidity (RH) have been iden-tified as the primary atmospheric constituents responsible for

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REID et al.: CORROSION OF ELECTRONIC RESISTORS 667

Fig. 2. Dimensions and boundary conditions of planar layer.

the degradation of Ag and some alloys commonly used in elec-tronic industry [5], [6]. As such, in this study, the combinationof 90% RH and 4 ppm H S was used to represent a highly accel-erated condition for the corrosion of the resistors [7]–[12]. Thehigh concentration of H S is more suitable to give data for elec-tronic components deployed in the Central and Latin America,Asia, and Pacific regions. In order to accelerate the diffusion ofthe gas and water vapor, the samples were exposed for a 60 dayperiod at 90% RH, 60 C and 4 ppm H S. Samples of each typeof resistors were extracted from the gas chamber at pre-definedintervals, and a range of materials characterization techniqueswere applied to investigate the progression to failure of the re-sistor components.

II. DIFFUSION MODEL

The corrosion of the resistor is limited by the diffusion timetaken for the water vapor and H S gas to penetrate the thin con-formal organic layer. A closed-form analytical expression forthe transient diffusion of species such as water vapor and H Sthrough a planar layer is presented here. The expression is usedto determine the time-varying concentration of H O and H S atthe interface between a polymeric coating and a metallic sub-strate.

Fig. 2 shows the dimensions and boundary conditions of tran-sient 1-D diffusion through a planar layer. The following as-sumptions apply.

• The thickness of the layer is negligible in comparison withany planar dimension. This imposes 1-D mass diffusion inthe -direction.

• At the plane of interest, 0, the layer is in contact witha metallic layer, so mass transfer is negligible.

• The surface of the layer, , is exposed to a well-stirred fluid, so the boundary layer contributes negligibleresistance to mass transfer.

• There is initially a uniform concentration, , within thelayer at time zero, and the layer is then exposed to an am-bient with concentration , at time zero, 0.

• No chemical interaction occurs between the H O and H Sspecies, or between these species and the polymer layer.

• The temperature of the layer is uniform.The transient mass transfer within the layer is governed by

(1)

wheremass concentration in consistent units (kg/m , ppm);coefficient of diffusion (m /s).

TABLE IDIFFUSION COEFFICIENTS FOR H O AND H S IN THIN

CONFORMAL ORGANIC EPOXY LAYER [14], [15]

Fig. 3. Normalized concentration of H S versus time for different temperaturevalues.

The following boundary and initial conditions apply:

(2)

(3)

(4)

From Incropera and De Witt (1990), the mass concentration atthe plane of interest is given by [13]

(5)

To incorporate the influence of temperature, the coefficient ofdiffusion, , can be assumed to display the following form:

(6)

where is the absolute temperature (K); is the activation en-ergy (eV); is the Boltzmann’s constant, 8.617 10 (eV/K);

is the reference temperature (K); and is the dif-fusion coefficient (m /s) at reference temperature. Table I liststhe physical properties for the diffusion of H O and H S in thinconformal organic epoxy layer.

As an illustration of the behavior of (6), Fig. 3 shows thenormalized concentration of H S as function of time for 40 and60 C. The difference in the time taken for H S to reach thesurface of the resistor is significantly affected by temperature,



such that at 20 C it would take approximately three years toreach 4 ppm H S, while at 60 C it would take approximatelyeight days. H O reaches equilibrium rapidly, taking no longerthan four days at 60 C. The practicality of testing the resistors ateither room temperature or 40 C is unacceptable with regard totest time for such components, therefore samples were exposedat 60 C.

III. EXPERIMENTAL METHOD

A. Sample Preparation

Two different types of commercially available 100 1608precision thick chip resistors were used for this study (typeA and type B). Prior to corrosion testing, the specimens wererinsed with isopropyl alcohol followed by distilled water anddried with nitrogen.

B. Generation of Corrosive Atmosphere

The tests were performed over a 60 day period with removalof 10 samples of each type of resistors (A and B) after 5, 10,15, 30, and 60 days exposure. The chamber had a volume ex-change of four times/h—a volumetric flow rate of 6 l/h, yieldinga mean local velocity within the chamber of order 0.6 mm/s. Al-though this velocity is low, it is evident from an assessment ofthe convective mass transfer rate that transport within the gasphase is fast relative to the consumption rate at the surface. Inorder to achieve 90% RH, a small liquid flow of water was fed toa mixing chamber in which the flow was directly controlled andmixed with the injected carrier gas (directly provided by a gascylinder H S 4 ppm mixed with purified air). Subsequently, thisgas-vapor-liquid mixture was lead to a temperature controlledheat exchange to achieve complete evaporation mixing. TheH S data was measured periodically with grab-sample measure-ments made with a Jerome 631X series meter (Arizona Instru-ments, Tempe, AZ). The gas and liquid flows were metered byBronkhorst High-Tech EL-FLOW LIQUI-FLOW controllers,respectively. The water was mixed with the gas, which was sub-sequently evaporated and supplied to an exposure chamber heldat desired temperature. Pure copper coupons where also placestrategically in the chamber and used to confirm exposure con-ditions.

C. Analytical Techniques

Samples were examined visually using a Leica Zoom 2000stereozoom microscope, and then mounted and mechanicallypolished to a 1 m diamond paste finish. After metallographicpreparation, the microstructures were examined under a ZEISSAxioskop optical microscope (OM). A JEOL JSM-840 scanningelectron microscope (SEM) equipped with a Princeton Gamma-Tech (PGT) energy analysis dispersive x-ray (EDS) system wasemployed to obtain high magnification electron images and toconduct chemical analysis, respectively. The resistor surfaceswere studied using the secondary electron mode. This modedoes not offer atomic contrast, but enables imaging at a higherresolution and is more sensitive to the morphology of the spec-imen surfaces.

Fig. 4. (a) Stereo-micrograph image of as-received type A resistor, (b) leftside, and (c) right side cross sectioned backscattered electron images of resistorcoating termination boundary interface at L–L and R–R in (a).

IV. RESULTS AND DISCUSSION

A. As-Received Resistor

The image depicted in Fig. 4(a) shows stereo-microscopeimage of resistor type A obtained in the as-received condition,with, Fig. 4(b) and (c) showing cross sections of the left andright side of the coating termination boundary interface, re-spectively. Fig. 4(b) and (c) shows that both sides exhibitedsimilar structure, comprising an outer bright layer of SnPbsolder approximately 10 m thick, above a darker Ni layerapproximately 14 m thick, with both layers over-lapping theovercoat between 50 to 80 m. The SnPb solder and Ni layersurrounds a Ag layer which, by over-lapping the overcoat actsas a seal with existing glass overcoat.

Fig. 5(a) depicts a stereo-microscope image of resistor typeB obtained in the as-received condition, with, Fig. 5(b) and (c)showing cross sections of areas labelled in Fig. 5(a) as –and – of the left and right side of the coating terminationboundary interface, espectively. Fig. 5(b) and (c) shows thatboth sides exhibited similar structure comprising an outer brightlayer of SnPb solder approximately 7 m thick, above a darkerNi layer approximately 5 m thick, with both layers over-lap-ping the overcoat between 5 to 20 m. The SnPb solder andNi layer also surrounds a Ag frit glass binder layer over a Aglayer, of which the glass binder layer extends over to the glassovercoat. The glass binder layer, by extending to over-lap theovercoat, should act as a more hermetic seal with existing glassovercoat, than just the Ni layer in type A. However, in most crosssectioned resistors of type B in the as-received condition, littleor no over-lap was observed.

B. After Exposure to Humid H S Conditions

The image depicted in Fig. 6 shows a typical type A resistorafter 60 days exposure at 90% RH, 60 C and 4 ppm H S. The



Fig. 5. (a) Stereo-micrograph image of as-received type B resistor (b) leftside and (c) right side cross sectioned backscattered electron images of resistorcoating termination boundary interface at L–L and R–R in (a).

Fig. 6. Stereo-micrograph of type A resistors after 60 days exposure to 90%RH, 60 C and 4 ppm H S.

resistor showed no visible signs of corrosion following optical,SEM and EDS detailed external examination. In direct con-trast, the type B resistor demonstrated clear evidence of corro-sion. The images depicted in the series of Fig. 7(a)–(e) showsstereo-microscope images of type B resistors which were ob-tained after five, ten, 15, 30, and 60 days exposure to 90% RH,60 C and 4 ppm H S, respectively. After initial exposure of 5and 10 days [Fig. 7(a) and (b)], a number of the resistors showedcorrosion product development at the interface between the darkovercoat and the bright solder. Fig. 7(c) shows the develop-ment of dark grey and green coloring of residue at the interfaceafter 15 days exposure. Following more prolonged exposure,the green residue became more pronounced, particularly after60 days exposure [see Fig. 7(e)] and appears to be mainly lo-cated at the edges of the resistor. The dark grey residue observedafter 15 days exposure continued to develop at the interface after30 and 60 days exposure, however, not to the same extent asthe green residue. The grey corrosion product is consistent witha grey Ag S which typically forms on Ag after exposure to ahumid S containing environment [7]–[10], [12]. The green cor-rosion product would indicate a Ni sulphate, which forms on Niafter exposure to similar conditions [12], [16].

Fig. 7. Stereo-micrographs of type B resistors after (a) 5, (b) 10, (c) 15, (d) 30,and (e) 60 days exposure to 90% RH, 60 C and 4 ppm H S.

To characterize the corrosion residue that developed on typeB resistors after exposure, more detailed analysis of the resistorswas conducted using SEM and EDS. Fig. 8 shows a secondaryelectron image of the interface between the glass overcoat andthe solder termination after 10 days exposure. The corrosionproducts that were observed at the interface between the over-coat and the termination [Fig. 7(a)–(e)] are shown in Fig. 8(a) toextend above the normal surface of the resistor. The corrosionproduct at the interface demonstrated two distinct morpholo-gies, first a smooth shaped residue corresponding to the greencorrosion product observed optically [Fig. 8(b)]; and secondly,a residue with distinctly faceted features corresponding to thegrey corrosion product [Fig. 8(c)]. Quantitative EDS analysiscarried out on the smooth shaped corrosion products highlightedthe presence of Ni and S [Fig. 8(b)], while the faceted areascomprised mainly Ag and S with traces of silicon (Si) and Ni[Fig. 8(c)].

In order to determine the cause of the corrosion productswhich developed on the surface of the resistors after exposure,the resistors were cross sectioned and analysed using SEM andEDS. As indicated by the clear absence of corrosion productson the external surface of type A resistor in Fig. 6 after 60 daysexposure, cross section analysis showed no evidence of corro-sion of the Ag layer. This would indicate that the SnPb solderand Ni layer by over-lapping the overcoat did indeed perform asbarrier for S diffusion and protected the Ag layer.

Fig. 9 shows a backscattered electron image of the right handside of a type B resistor after 15 days exposure. Table II showsthe results of quantitative EDS spot analysis carried out on spotstaken from selected areas labelled in Fig. 9. It can be clearly



Fig. 8. SEM and EDS spectrum of type B device after 10 days exposure to90% RH, 60 C and 4 ppm H S: (a) secondary electron image of the interfacebetween the glass overcoat and the solder termination, (b) EDS spectrum of thesmooth shaped residue (green corrosion products), and (c) EDS spectrum of thefaceted residues (grey corrosion products).

seen in Fig. 9 that corrosion products developed on the surfaceof the resistor, most noticeably on the overcoat, where corrosionproducts built up at the interface between the overcoat and thesolder termination (spots 2–4 in Fig. 9). The thin layer of Agin the region underneath where the solder termination “curls”would also appear to be corroded (spot 1 in Fig. 9).

Fig. 10 shows a backscattered electron image of the right handside of a type B resistor after 30 days exposure to 90% RH,60 C and 4 ppm H S. Similar to previous results [Fig. 7(a)–(e)]it can be clearly seen that corrosion products developed on thesurface of the resistor. The formation of Ag S on the surface ofthe resistor and underneath the overcoat in the Ag base wouldindicate that both Ag and S both migrated along the interface.Additionally, the Ag in the glass binder layer appears to be cor-roded. However, it is worth noting that when EDS analysis was

Fig. 9. Cross sectioned backscattered electron cross section image of the typeB resistor after 15 days exposure to 90% RH, 60 C and 4 ppm H S. (Note:EDS spot annotations show in Table II).

TABLE IICOMPOSITION OF SPOTS LABELLED IN FIG. 9 OF TYPE B RESISTOR AFTER

15 DAYS EXPOSURE TO 90% RH, 60 C AND 4 PPM H S

conducted on the dark regions in the glass binder layer there wasno Ag S. The latter could be a result of Ag which diffused fromthe glass binder along the interface boundary between the glassovercoat and the SnPb/Ni layers to the surface of the resistor.It is possible. When the Ag becomes exposed to a fresh H Senvironment and water available in the surface it oxidized theH S to S [12]. At high relative humidities ( 75%RH), severalmonolayers of water form on the surface and the H S dissolveseasily and dissociates to HS ion species, with the S attackingthe Ag [12], [19]. On dry surfaces where there is less than onemonolayer of water ( 40%RH), on the surface, dissociative ab-sorption of H S onto the metal lattice, occurs preferentially atany surface defect. Where normal bonding of the Ag structure isunstable, Ag S corrosion products nucleate at the unstable sites.As mentioed earlier, humidity plays a very important role in thecorrosion of Ag. Literature data shows that by increasing the rel-ative humidity the corrosion rate of Ag is accelerated [12]. Thiscould explain why more extensive Ag S develops on the surfaceof the resistor. In contrast, corrosion of the Ag conducting layeris not as aggressive.

As mentioned above, the Ag S films have been recognized asthe major corrosion products on Ag [7]–[12]. Previously, it hasbeen shown that Ni is quite resistant to corrosion [12], [16]–[18],[20]–[23]. However, the role of Ni during the corrosion of theresistor is not clear. The results here indicate that significant Nicorrosion occurs, such that Ni would appear to be the domi-nant corrosion product after prolonged exposure. The imagesdepicted in Fig. 11(a) and (b) demonstrated backscattered elec-tron images of the left and right hand side of a type B resistorafter 30 days exposure, respectively.



Fig. 10. Backscattered electron cross section image of the type B resistor after30 days exposure to 90% RH, 60 C and 440ppm H S.

Both images in Fig. 11(a) and (b) show that the corrosionproducts that developed under the solder termination have re-sulted in fracture of the solder layer. The latter would be due tothe increased volume of the corrosion products. Further analysisusing elemental mapping [Figs. 11(c)] revealed that the corro-sion product to be mainly Ni and S rich, with islands of Ag and Senrichment encapsulated in the Ni and S rich corrosion product.

Previous data has suggested that Ni is unlikely to be corrodedby H S [12]. As such, it is possible that the coupling of theAg and the Ni layer may act as a site for an electrochemicalcorrosion cell. As a result of the high humidity and dissociationof the H S to HS ion results in a concentrated solution, therebyproviding a conductivity path between the Ag and the Ni. Theresult is an accelerated attack of the Ni layer resulting in theformation of Ni and S corrosion products [observed in Fig. 6(a)and (b)]. The coupling of the Ni and Ag layers are facilitatedby the gap between the glass binder (not overlapping) with theovercoat, allowing the Ni layer to come in contact with the Aglayer. This creates the diffusion of moisture along the interfaceand enables the conducting electrolytic path between the twolayers.

Precision chip resistors are generally robust components and,despite the level of corrosion which was observed on the Type Bresistor, no significant increase in resistance was observed afterexposure. As a consequence, it may be necessary to combineelectrical stresses with the exposure in order to discern perfor-mance differences between the Type A and B resistors. Further-more, it is clear that environmental stress tests, such as Battellemixed flowing gas (MFG), are more suitable for North Americaand Western Europe but unsuitable to give life data for electroniccomponents deployed in Central and Latin America, Asia andPacific region or parts of the Middle East where pollutant levelsare considerably higher [24]–[26]. In addition, these tests are notsufficiently severe to screen out marginal electronic parts sus-ceptible to corrosion-related failures. The Battelle MFG classessystem was originally designed to equate equivalent field ser-vice time to chamber exposure times for components deployedin North American and Europe regions [27]–[29]. There is a

Fig. 11. SEM and EDS of type B resistor after 30 days exposure to 90% RH,60 C and 4 ppm H S: (a) backscattered electron cross sectioned images of theleft side and (b) right side; and (c) elemental mapping of (a).

clear need to revise the Battelle MFG classes system in order toequate equivalent field life in regions of the world where consid-erably more demanding environmental conditions are observed.

V. CONCLUSION

Corrosion of the type B resistors occurred after five day ex-posure and continued to develop up to 60 days exposure to 90%RH, 60 C and 4 ppm H S, while type A resistor showed nosigns of corrosion. It can be deducted that the corrosion of thetype B resistor was due to reactions between the S environmentand the Ag layer creating an electrochemical corrosion cell be-tween the Ag and Ni layer. The main corrosion products thatdeveloped were Ag S and Ni sulphur residue. The root causeof corrosion can be attributed to poor overlapping of the solderand Ni layer and, in particular, the glass binder over the glass



overcoat, which allowed Ag and S to diffuse along the inter-face. Furthermore, poor overlapping permitted contact betweenthe Ni layer and the Ag layer resulting in electrochemical cor-rosion cell.

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Michael Reid is currently a Senior Research Fellow at the Stokes Institute,University of Limerick, Limerick, Ireland, where he specializes in reliabilityphysics. He is in active collaboration with Bell Laboratories, Lucent Technolo-gies, Nokia Corporation, Molex Ireland, and SC Johnson in reliability research,specifically related to materials science, metallurgy, microscopy, and corrosion.He is currently supervising three postgraduate students and mentoring two post-doctoral researchers.

Jeff Punch is the Director of Micro-Mechanical Engineering Group, StokesInstitute, University of Limerick, Limerick, Ireland, collaborating with the In-stitute’s partners and clients on a range of research programmes. He is cur-rently leading the Test and Reliability Strand, Center for TelecommunicationsValue-Chain Research (CTVR), an SFI-funded multi-university research pro-gramme in collaboration with Bell Laboratories. He has a strong track-record ingovernmental and industrial research programs, and he is currently supervisingfive postgraduate students and mentoring two postdoctoral researchers.

Claire Ryan is currently a Research Fellow at the Stokes Institute, University ofLimerick, Limerick, Ireland, working on a number of solder reliability projects.Claire has a number of years experience working in consultancy and researchin the area of electronics manufacturing, reliability and failure analysis. She isChairperson of the Steering and Technical Committees of SMART Group Ire-land and is also a Member of the Reliability Technical Expert Group, EuropeanLead Free Network (ELFNET) Consortium.

John Franey is a Distinguished Member of Technical Staff, Lucent Technolo-gies Reliability Physics Group, Murray Hill, NJ. He joined Bell Laboratories in1970. His work has been focused on failure analysis and the interactions of ma-terials with people and atmospheric environments. John has 36 U.S. and ForeignPatents in the areas of corrosion and ESD protection, and has authored over 100papers in those areas of expertise. Currently, he has the responsibility of deter-mining the root cause of failures for Lucent product along with determining thepath for current and future mitigation of those issues.

Gustav E. Derkits is a Member of Technical Staff, Lucent Technologies Relia-bility Physics Group, Murray Hill, NJ. He joined Bell Laboratories in 1982 andhas worked in a variety of technical areas including design and fabrication ofIII–V electronic and optoelectronic devices, and physics and chemistry issuesaffecting yield, quality, and reliability of telecommunications products. He hasover 30 U.S. patents and has authored over 20 papers in reviewed journals.

William D. Reents, Jr. is a Consulting Member of Technical Staff and ActingManager of the Reliability Physics Group, Murray Hill, NJ. He joined Bell Lab-oratories in 1980, working in several areas of research and root cause analysis.His areas of specialty include package hermeticity, organic contamination andgas and particle contamination issues. Since 2001, he has been a member of theReliability Department, focusing on forwarding looking reliability activities, in-cluding device-level assessments and corrosion-related issues.

Luis F. Garfias is currently employed at SC Johnson, Racine, WI, working inthe areas of materials science, microscopy, and environmental and corrosion sci-ences. He previously worked for eight years in the Reliability Research Depart-ment, Bell Laboratories, Lucent Technologies, working in the areas of materialsscience, corrosion, environmental, and biomaterials. His work at Bell Laborato-ries was primarily related to the reliability of electronic hardware in aggressiveenvironments.


the corrosion of electronic resistors

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