In situ optical inspection of electrochemical migration during THB tests

Illés

Harsányi

2013

Per. Pol. Elec. Eng.

Self Cite

The reliability investigation of lead-free solders is still a current issue. In this paper, Electrochemical Migration (ECM) behaviour of novel lead-free micro-alloyed low Ag content solders was investigated by water drop test in IntroductionIn microelectronics industry, the applied solder materials are one of the most important factors related to the reliability of the products. According to the Restrictions of Hazardous Substances (RoHS) directive of European Union, lead bearing solders had to be replaced with lead-free ones [1]. In this context, alternative binary alloys had been examined as replacements for SnPb solders, such as near-eutectic SnAg, SnCu and SnZn alloys. However, ternaries (SnAgCu, SnZnAg, SnZnIn, etc.) and even quaternary alloys (SnZnAgAl, SnAgBiCu, SnInAgSb) had also been studied as candidates for lead-free solders [2][3][4][5][6][7].The reliability investigation of lead-free solders is still a current issue. One of the important reliability topics is the electrochemical migration (ECM) failure phenomenon. The common characteristics of the ECM phenomenon include the presence of moisture on conductor-dielectric-conductor systems under bias voltage, the electrochemical process and the metallic dendrite growth. This process is driven by the applied electric field from the anode to the cathode. Dendrite growth occurs as a result of metal ions being dissolved into a solution from the anode and deposited at the cathode, thereby growing in needle or tree-like formations. This effect causes short-circuits in electronic circuits, which may lead to a catastrophic failure.Many papers can be found about ECM investigations carried out on different lead-free solder alloys. Takemoto et al. have found that some tin based lead-free solder alloys are more resistant to ECM than Sn-Pb40 alloy and pure Indium. In-48Sn and In-50Pb alloys were found to be immune to ECM in high purity water [8]. Yu et al. have described that in Sn-37Pb and Sn-36Pb2Ag systems the main migration element is Pb, while in Sn-Ag and Sn-Ag-Cu solder alloys Sn leads the migration in high purity water [9,10].Other publication reported that SAC305 lead-free solder alloy has longer ECM lifetime in 0.001% NaCl solution than in 0.001% Na2SO4, since the passivity layer formed of SnO2 is thicker in the case of NaCl solution and Sn is the only element that contributes to ECM at room temperature [11]. The migration behaviour and the deposition process of Sn, Cu and Ag in case of SAC305 solder alloy were also observed in a thermal-

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Electrochemical Migration of Micro-alloyed Low Ag Solders in NaCl Solution

Illés

Harsányi

2013

Per. Pol. Elec. Eng.

Self Cite

“…The setup of the measuring platform/method was described elsewhere [27]. Optical inspection and the electrical measurement were carried out in the same time.…”

Section: Methodsmentioning

confidence: 99%

Electrochemical migration of Ni and ENIG surface finish during Environmental test contaminated by NaCl

J Mater Sci: Mater Electron

2017

Self Cite

The electrochemical migration (ECM) mechanism occurs at the presence of moisture in the case of operating circuits and results in shorts (dendrites) between adjacent conductor lines/traces. Dendrite growth occurs as a result of metal ions being dissolved into a solution from the anode and deposited at the cathode, thereby growing in tree-like formations. In this study the water condensation process and ECM behavior of Nickel (Ni), Electroless Nickel Immersion Gold (ENIG) and pure copper were investigated using Thermal Humidity and Bias (THB) test in NaCl environment. The THB results show that Cu has higher ECM resistance than Ni and ENIG surface finishes, which was an unexpected result. The main influencing factors of the water condensation (e.g.: surface roughness, thermal parameters) and the ECM processes (precipitates and dendrites) were investigated and discussed in details. Furthermore, a novel ECM model for Ni and NiAu surface finish was established using THB test in case NaCl contaminated samples.

“…Usually, migration tests were tested by three main methods; water drop (WD) test [11], environmental tests under different thermal-humidity conditions [12] and by various electroanalytical methods, like voltammetry or polarization tests [13]. On the one hand the electrochemical corrosion and migration investigations of Ag were usually tested in bulk solution.…”

Section: Introductionmentioning

confidence: 99%

Electrochemical migration of Sn and Ag in NaCl environment

2016 IEEE 22nd International Symposium for Design and Technology in Electronic Packaging (SIITME)

Szivos

Adam

et al. 2016

Abstract-The impact of chloride ion concentration on electrochemical migration (ECM) of tin and silver was studied by using an in-situ optical and electrical inspection system. It was found, that in both cases, dendrites grow not only in an electrolyte solution at low chloride concentration but also in an electrolyte at medium and high or even saturated chloride concentrations as well. According to the results, the migration susceptibility has decreased at low and medium concentration levels in both cases. However, the ECM susceptibility of Ag has increased, while the migration susceptibility of Sn was decreased at the saturated concentrations.