Electrochemical Migration Behavior Research Articles

Effect of Conformal Coating on Electrochemical Migration Behavior of Multi-Layer Ceramic Capacitor for Automotives Based on Water Drop Test

A large amount of multi-layer ceramic capacitor (MLCC) is mounted inside a printed circuit board (PCB) constituting electronic components. The use of MLCC in electric vehicles and the latest mobile phones is rapidly increasing with the latest technology. Environments in which electronic components are used are becoming more diverse and conformal coatings are being applied to protect mounted components from these environments. In particular, MLCCs in electronic components mainly have voltage applied. They might be used in environments where humidity exists for various reasons. In a humid environment, electrochemical migration (ECM) will occur, with the cathode and anode on the surface of the MLCC encountering each other. This can result in product damage due to a short circuit. In this study, the effects of voltage, NaCl concentration, and distance between electrodes on a non-mount MLCC, surface mount MLCC, and solder pad pattern were evaluated using a water drop test (WDT). Based on the analysis of the effects of the presence of conformal coating, applied voltage, concentration of NaCl, and the distance between electrodes, a mechanism model for ECM behavior in MLCCs was proposed.

Electrochemical migration behavior between Cu and Ag under a thin electrolyte layer containing chloride

PurposeThe purpose of this paper is to investigate the effects of chloride ion concentration and applied bias voltage on the electrochemical migration (ECM) behavior between Cu and Ag under an NaCl thin electrolyte layer (TEL).Design/methodology/approachA self-made experimental setup for the ECM behavior between Cu and Ag was designed. An HD video measurement microscopy was used to observe the typical dendrite/corrosion morphology and pH distribution. Short-circuit time (SCT), short-circuit current density and the influence of the galvanic effect between Cu and Ag on their ECM behavior were studied by electrochemical tests. The surface morphology and composition of dendrite were characterized by FESEM/EDS.FindingsThe SCT increased with increasing NaCl concentration but decreased with increasing applied bias voltage, and the SCT between Cu and Ag was less than that between Cu and Cu because their galvanic effect accelerated the dissolution and migration of Cu. When NaCl concentration was less than or equal to 6 mmol/L, cedar-like dendrite was formed, whereas no dendrite formed and only precipitation occurred at high chloride ion concentration (100 mmol/L). The composition of the dendrite between Cu and Ag was copper.Research limitations/implicationsThe significance of this study is to clarify the ECM failure mechanism of printed circuit board (PCB) with an immersion silver surface finish (PCB-ImAg).Practical implicationsThis study provides a basic theoretical basis for the selection of protective measures and metal coatings for PCB.Social implicationsThe social implication of this study is to predict the service life of PCB.Originality/valueThe ECM behavior of dissimilar metals under a TEL was investigated, the influence of the galvanic effect between them on their ECM was discussed, and the SCT increased with increasing NaCl concentration.

In situ study the effects of bias and electric field intensity on electrochemical migration behavior of Sn96.5Ag3.0Cu0.5 solder alloy

In this work, the influence of bias and electric field intensity on the electrochemical migration of SAC305 solder alloy is investigated using a self-designed in-situ thin electrolyte film device. The results indicate that when the bias is 0.5 V, a compact passivation film forms on the sample surface, effectively inhibiting dendrite growth. When the applied bias reaches 0.75 V, it is observed that specific corrosion products are generated between the two plates, and the occurrence of dendritic growth phenomena is still absent. Dendrite development is observed when a bias voltage of 1 V is applied. Regarding the electrode reactions, when the applied bias falls below 1.5 V, a notable polarization resistance is encountered in the anode reaction. In this case, the cathode reaction primarily entails the process of oxygen reduction. As the applied voltage climbs to 1.5 V, the anodic potential shows an increase, leading to a reduction in the polarization resistance of the anodic process that determines the rate of the electrochemical reaction. At this time, the cathode potential exhibits a comparatively negative value, leading to the progressive occurrence of the hydrogen evolution process. Additionally, the influence mechanism of bias on ECM is also proposed.

Evaluating electrochemical migration behavior of sintered nano-Ag: factors of bias voltage, electrode spacing, sinter process parameters, and NaCl concentration

Evaluating electrochemical migration behavior of sintered nano-Ag: factors of bias voltage, electrode spacing, sinter process parameters, and NaCl concentration

Electrochemical migration behavior of copper under a thin distilled water layer

Electrochemical migration behavior of copper under a thin distilled water layer (TDWL) was explored by electrochemical and surface characterization. It demonstrates that electrochemical migration of copper can occur under a TDWL. The short-circuit time caused by copper dendrites increases with TDWL thickness. It is attributed to the acceleration of hydroxyl ion migration caused by the increasing TDWL thickness, which inhibits migration of copper ions due to the formation of Cu(OH)2. The short-circuit time decreases with applied bias voltage, which originates from the acceleration of copper dissolution.

Electrochemical Migration Behavior on FR-4 Printed Circuit Board with Different Surface Finishes

Electrochemical Migration Behavior on FR-4 Printed Circuit Board with Different Surface Finishes

Electrochemical migration behavior of moldy printed circuit boards in a 10 mT magnetic field

In the electrochemical migration behavior (ECM) of printed circuit boards containing mold under a static magnetic field (SMF), the role of the field perpendicular to the electrodes is discussed; the B field inhibits the growth and metabolism of mold, while controlling electrochemical diffusion and nucleation. The field indirectly affects the function of mold as a transmission bridge between two electrodes. In this work, the water drop test was used to simulate the adhesion and growth of mold on the circuit board in a humid and hot environment; confocal laser scanning microscopy, scanning electron microscopy, energy dispersive spectroscopy, Raman spectra, and a scanning Kelvin probe were used to analyze the mechanism of static magnetic field and mold on the electrochemical migration.

Correlations between Electrochemical Ion Migration and Anomalous Device Behaviors in Perovskite Solar Cells

Ion migration is a solid-state electrochemical phenomenon widely observed in the family of halide perovskite materials, which is attributed to their intrinsically soft ionic crystal structures and mixed electronic–ionic conduction properties. Numerous studies in the literature have indicated that ion migration is the major cause of various anomalous device behaviors, including light-soaking effect, photocurrent–voltage hysteresis, and slow open-circuit voltage decay, which are commonly observed in perovskite solar cells. Herein we present a comprehensive review on these studies. We also provide a mechanistic understanding, featuring the built-in electrical field as a key factor for the elucidation of ion migration and associated device behaviors in a consistent manner. Finally, we discuss future research directions toward a better understanding of these phenomena.

Electrochemical migration behavior of low-temperature-sintered Ag nanoparticle paste using water-drop method

The electrochemical migration (ECM) behavior of low-temperature-sintered Ag nanoparticle paste electrode was investigated using water-drop method. The effects of applied direct current bias voltage and NaCl concentration on ECM behavior were discussed. Results show that: at low NaCl concentration levels, mean time to failure caused by ECM decreased with increasing NaCl concentration due to the increase of solution conductivity; at medium NaCl concentration levels, dendrite growth was retarded due to the formation of AgOH or other insoluble products, while at high NaCl concentration levels, due to the turbulent hydrogen evolution, the second spreading of water drop resulted in the circuit broken and thus inhibited ECM behavior. Moreover, mean time to failure decreased with the rising applied bias voltage. More importantly, hexadecyltrimethylammonium chloride (CTAC) was proved to act as an effective inhibitor to migrate dendrite growth by selected adsorption. And the ECM inhibition efficiency increased with the concentration of CTAC. Relevant mechanisms of ECM behavior and ECM inhibition effect of CTAC for low-temperature-sintered Ag nanoparticle paste were proposed.

Fabrication of an IPL-sintered Cu circuit and its electrochemical migration behavior

Problems associated with the oxidation of Cu nanopaste have been widely studied in efforts to develop a replacement for Ag nanopaste. The intensive pulsed light (IPL) sintering process has been suggested to solve the oxidation problem because it is a method with a short processing time and is conducted at room temperature. Cu nanopaste was fabricated with Cu nanoparticles and a functional organic matrix. Cu nanopaste screen-printed onto a polyethylene terephthalate substrate was subjected to various IPL sintering conditions, and the effects of pulse power and pulse width on the microstructure, electrical resistivity, and electrochemical migration behavior of the printed Cu patterns were investigated. The electrical properties of the Cu patterns improved with increasing pulse power and pulse width because organic residues were removed by the IPL energy. The electrical properties of the Cu patterns improved with increasing pulse power and pulse width because organic residues were removed by the IPL energy. The electrochemical migration behavior was varied because of leaked ethylene glycol from organic matrix. The dendrites from lower pulse condition has finer microstructure and increased nucleation.

Electrochemical migration and corrosion behaviours of SAC305 reinforced by NiO, Fe2O3, TiO2 nanoparticles in NaCl solution

Pb-free solders incorporated with nano-sized particles have been identified, as potential Pb-free nanocomposite solders that could provide higher microstructure stability and better mechanical properties than the conventional solders. Nowadays, the miniaturizations of electronic devices increase in their usage have increased the risk of failure due to ion migration and corrosion phenomena. This research investigates the effects the electrochemical migration (ECM) and corrosion behaviour of Sn- 3.0Ag-0.5Cu (SAC305) reinforced by NiO, Fe2O3 and TiO2 nanoparticles in 0.1M NaCl solution. The SAC305 solder alloys were doped with different percentages of NiO, Fe2O3 and TiO2 at nominal percentages of 0.01, 0.05 and 0.15 wt% in producing nanocomposite solder paste. Then, the solder paste has flowed in the reflow oven at the temperature of 240°C. After that, the Water Drop Test (WDT) was performed using 0.1 M NaCl solution to investigate the ion migration behaviour and Potentiodyamic Tafel Polarization technique to determine the corrosion behaviour on the solder alloys. In general, the results showed the mean-time-to-failure (MTTF) of SAC305 solder alloy increased when added of the nanoparticles of NiO, Fe2O3 and TiO2. Besides, SAC305-TiO2 has the longest MTTF in 0.1 M NaCl solution followed by SAC305-Fe2O3 and SAC305-NiO nanoparticles. This results is believed due to the presence of nanoparticles as the alloying element in the solder that hinder the process of ECM to suppress the growth of the dendrites accelerating for the short circuit occurs and causes the failure of the IPC-24 test board. The potentiodynamic polarization curve results exhibit the SAC305 with nanoparticles decreased the corrosion rate compared with SAC305 solder alloy only. SAC305 with NiO and TiO2 have slightly lower corrosion rates compared with Fe2O3 nanoparticles. Therefore, SAC305 reinforced by TiO2, Fe2O3 and NiO nanoparticles exhibited excellent ECM and corrosion resistance behaviours in the 0.1 M NaCl solution.

Electrochemical migration behavior of Sn-based lead-free solder

In this paper, the water droplet experimental method was used to in situ study the electrochemical migration and related behaviors of Sn-based lead-free solder. Results showed that the electrochemical migration short-circuit time decreased with voltage increasing. Electrochemical migration was difficult to occur when the voltage was less than 1.5 V. However, when the voltage was above 5 V, metal deposits were generated in a short time and caused a bridge between two electrodes, which led to short circuit. As spacing increased, the short-circuit time prolonged. The three-dimensional pattern between voltage, spacing and short-circuit time had been constructed, which is beneficial to estimate the short-circuit time value under a combination of any voltage and spacing within a certain range. When changed the concentration of NaCl solution, it was founded that dendrites which surface covered much precipitates were formed at a low concentration. At medium concentration, there was no dendrites but only formed a large amount of precipitates. At a high concentration, the dendrites which surface with less precipitates were showed again. The formation mechanisms of dendrites under different NaCl solution concentrations were analyzed. In addition, the effects of different materials on electrochemical migration behavior were also studied, founding that electrochemical migration products of Sn, Sn0.7Cu and Sn3Ag were mainly Sn and Sn oxides. The electrochemical migration products of Sn9Zn contain much Zn element apart from Sn and Sn oxides. At a lower voltage, Sn9Zn solder had better electrochemical migration resistance than Sn, Sn0.7Cu and Sn3Ag, but this phenomenon was not obvious at a higher voltage.

ELECTROCHEMICAL MIGRATION BEHAVIOR OF Sn-3.0Ag-0.5Cu SOLDER ALLOY UNDER THIN ELECTROLYTE LAYERS

The electrochemical migration (ECM) behavior of Sn-3.0Ag-0.5Cu solder alloy under thin electrolyte layers was investigated using a technique based on the coupling of in situ electrochemical measurements and optical observation. Results showed that the mean time to failure first increased and then decreased as thickness of the electrolyte layer increased, the maximum value was present at 200[Formula: see text][Formula: see text]m. The higher the bias voltage applied, the faster was the rate of dendrite growth. And, Sn leaded the ECM of SAC305 solder alloy. Mechanisms relevant have been proposed to explain the ECM behavior of Sn-3.0Ag-0.5Cu solder alloy.

Electrochemical migration behavior of Sn–3.0Ag–0.5Cu solder alloy under SO2 polluted thin electrolyte layers

The effect of HSO3− on the electrochemical migration (ECM) of Sn–3.0Ag–0.5Cu lead-free solder alloy under thin electrolyte layers was investigated using the thin electrolyte layer method. The results showed that the migration element of Sn–3.0Ag–0.5Cu alloy was Sn and the faster-growing branch of the dendrite resulted in a sharper tip during the dendrite growth process. Increasing the amount of HSO3− decreased the probability of ECM. Due to the hydrolysis of HSO3, the pH value of electrolyte in thin electrolyte layer shifted toward a strongly acidic environment and a lower pH condition was favorable for dendrite formation. However, HSO3− reacted with tin ions to form some insoluble compounds during the ECM process, resulting in a decrease of tin ion concentration under thin electrolyte layers. A protective film formed on the anode surface, thus blocking the anodic dissolution process. Possible reactions were proposed to explain the inhibitory effect of HSO3− on the ECM of Sn–3.0Ag–0.5Cu alloy.

A comparison of the Cu electrochemical migration behavior between Cu lines with 5 um L/S realized by conventional Semi Additive Process (SAP) and an innovative Excimer Laser Damascene Process

Abstract The technological evolution regarding multi-chip integrated Fan-Out packages and chip scale packages (CSPs) with high amounts of I/O demands for even higher routing densities. Conventional used technologies and materials like mask aligner and photosensitive polymers used for semi additive process (SAP) in the BEOL have reached its limits to push the resolution down to two um. New materials and technologies are necessary to overcome these limits. As the routing density increases, so does the reliability requirements. The electrochemical migration between Cu lines cannot be neglected and need to be analyzed as the distance between the Cu lines is decreasing. A new approach for fine-line multi redistribution layers (RDL) realized by an excimer laser dual damascene process was presented in the past, using laser ablation and Cu chemical mechanical planarization (CMP) to realize embedded Cu lines. This approach has several advantages regarding the processing but one of the most important characteristics of the damascene approach is the improved electrochemical migration behavior. The Cu lines are partially cladded by the Ti part of the seed layer due to the way of processing. The Ti acts as a barrier layer and inhibits the Cu migration into the surrounding polymer. RDL structures realized by conventional SAP have Ti only under and not between the Cu lines. In this study different test samples with interdigital structures (resp. interdigital capacitor IDC) with five um line and space width (L/S) were realized to analyze the electrochemical migration behavior between the fingers of the IDC. The samples were realized by SAP and by the excimer laser damascene process and were subsequently tested by the temperature humidity bias (THB) test resp. biased High Accelerated Stress Test (bHAST). With the help of this work, we were able to compare the reliability of both process variants and to demonstrate and prove the reliability of embedded copper lines realized by the excimer laser damascene process.

Effect of Phosphorus and Nickel on Electrochemical Migration of Sn-3Ag-0.7Cu Solder Paste in Simulated Body Fluid

Electrochemical migration (ECM) behaviour of Sn-3Ag-0.7Cu and Sn-3Ag-0.7Cu-0.03P-0.005Ni solder alloys were investigated using simulated body fluid (SBF) solution. In electronic devices, ECM phenomenon potentially leads to incompetence or failure of the whole devices. According to water drop test (WDT), mean-time-to-failure (MTTF) of commercially used Sn-3Ag-0.7Cu solder alloy was prolonged with addition of phosphorus (P) and nickel (Ni) as alloying elements. According to microstructure of each solder paste alloy which was observed using field emission scanning electron microscope (FESEM), dendrite structure in Sn-3Ag-0.7Cu-0.03P-0.005 Ni solder was lesser than in plain the Sn-3Ag-0.7Cu. This phenomenon suggested that presence of P and Ni retarded the growth of dendritic thus improved its corrosion resistance. Therefore, Sn-3Ag-0.7Cu-0.03P-0.005Ni possessed a good corrosion resistance in SBF medium.

Effects of mould on electrochemical migration behaviour of immersion silver finished printed circuit board

The role played by mould in the electrochemical migration (ECM) behaviour of an immersion silver finished printed circuit board (PCB-ImAg) under a direct current (DC) bias was investigated. An interesting phenomenon is found whereby mould, especially Aspergillus niger, can preferentially grow well on PCB-ImAg under electrical bias and then bridge integrated circuits and form a migration path. The cooperation of the mould and DC bias aggravates the ECM process occurring on PCB-ImAg. When the bias voltage is below 15V, ECM almost does not occur for Ag coating. Mechanisms that explain the ECM processes of PCB-ImAg in the presence of mould and DC bias are proposed.

Electrochemical corrosion and electrochemical migration of 64Sn-35Bi-1Ag solder doping with xGe on printed circuit boards

Ge-doped effects on electrochemical corrosion (ECC) and electrochemical migration (ECM) behaviors of 64Sn-35Bi-1Ag (SBA) solder on printed circuit boards (PCBs) in 3wt% NaCl solutions were discussed. ECC was conducted by potentiodynamic polarization and electrochemical impedance (EIS) tests. Dendrites growth is a result of electrochemical migration (ECM) process, which is another factor affecting soldering reliability for electronic packagings, it was carried out as a designed schematic diagram coupled with a direct current power supply. Microstructures of products were investigated by SEM coupled with EDAX, XRD techniques. ECC results showed that anti-corrosive capacity increased as an increase of Ge addition in SBA solder which was expressed as the percent corrosion prevention (IE%), there was a maximal IE% value (83.74) when Ge addition was 0.5wt%, this obtainment was consistent to EIS results. The probable reason was that Ge had a “skin collection” effect, that was, it highly enriched and segregated at edge of SBA solder, which protected Sn in SBA solder from being corroded. Microstructure of corrosive products was distinctly different for SBA solder with and without Ge addition. ECM results showed that the dendritic grown rate of pure SBA solder was slower than those of its candidates with Ge dopings. Dendrites of SBA solder with 0.5wt% Ge addition grew to about 100–150nm in length and 20–50nm in width after ECM test for 8h, they were nanorods arranged trimly into arborization. While dendrites was shorter under the same condition for pure SBA solder without Ge doping. The dendritic growth mechanism was tentatively discussed. It showed the loaded electronic field intensity during ECM process played an important role for dendritic formation owing to its controlling the dendritical crystal anisotropic growth rate. Medium concentrations had an another key effect, which affected by controlling the ion diffusion from anode to cathode. From the point of microelectronic packagings, Ge addition was advantage to improve anti-corrosion capacity of SBA solder, but it also reduced soldering reliability if ECM process took place in surrounding of wet and thermal weather.

Electrochemical Migration Behavior of Copper-Clad Laminate and Electroless Nickel/Immersion Gold Printed Circuit Boards under Thin Electrolyte Layers.

The electrochemical migration (ECM) behavior of copper-clad laminate (PCB-Cu) and electroless nickel/immersion gold printed circuit boards (PCB-ENIG) under thin electrolyte layers of different thicknesses containing 0.1 M Na2SO4 was studied. Results showed that, under the bias voltage of 12 V, the reverse migration of ions occurred. For PCB-Cu, both copper dendrites and sulfate precipitates were found on the surface of FR-4 (board material) between two plates. Moreover, the Cu dendrite was produced between the two plates and migrated toward cathode. Compared to PCB-Cu, PCB-ENIG exhibited a higher tendency of ECM failure and suffered from seriously short circuit failure under high relative humidity (RH) environment. SKP results demonstrated that surface potentials of the anode plates were greater than those of the cathode plates, and those potentials of the two plates exhibited a descending trend as the RH increased. At the end of the paper, an electrochemical migration corrosion failure model of PCB was proposed.

Fabrication of Cu–MWNT nanocomposite and its electrochemical migration behaviors

Metal matrix composites with multiwalled carbon nanotubes (MWNTs) are promising alternatives for stretchable and highly reliable integrated circuits in stretchable electronic systems. We investigated the electrochemical migration (ECM) characteristics of copper (Cu)–MWNT nanocomposite paste electrodes on polydimethylsiloxane. The electrodes were fabricated by screen printing using nanocomposite paste with various MWNT ratios. The ECM characteristics were assessed by water drop testing with distilled water. The results revealed that the Cu–MWNT nanocomposite electrodes containing higher MWNT ratios required longer ECM times to bridge the adjacent electrodes with ECM dendrites. The increase of the addition of MWNTs induced a slower electrochemical electrode response, thereby suppressing the ECM dendrite formation and growth. When the electrodes were stretched parallel and perpendicular to their arrangement with a tensile strain of 2 %, the ECM times decreased by around 35 % and 26 %, respectively. Different dendrite behaviors were observed with respect to the tensile direction.