Rajan Ambat

Technical University of Denmark | DTU · Department of Mechanical Engineering

The paper focuses on the analysis of initiation and propagation of CO 2 corrosion in several samples of low-alloy steel with different microstructures using scanning electrochemical microscopy (SECM) and other microscopy techniques. It is found that the corrosion rate and the mode of corrosion are highly sensitive to the microstructure. The overall...

The Zinc-air primary batteries (ZAB's) are prone to electrolyte leakage upon exposure to high temperature and humidity conditions. Potassium hydroxide is a hygroscopic and corrosive compound and it can cause various electrochemical corrosion failures for the attached electronics inside a device. In this study, the effect of temperature and humid co...

The microstructure and intergranular corrosion have been studied in an extruded and aged Al-Mg-Si alloy doped with 0.05 wt% Cu after immersing the material in an acidified salt solution. Intergranular corrosion takes place in this alloy despite the low Cu content. Electron microscopy analysis of the surface exposed to the corrosive environment does...

The effect of cooling rate-induced microstructural changes on the corrosion resistance in a CO2-saturated 3.5 wt.% NaCl solution have been explored for an API L80-1Cr steel. The corroded layer majorly contains siderite, akagenite, and undissolved cementite. The amount of FeCO3 in this layer is larger for the water-cooled sample with a martensitic s...

The vulnerability of hearing aid devices to corrosion is critical due to their exposure to various kinds of ionic contaminants from the human body, such as sweat, sebum, and so forth, and harsh climatic conditions such as high temperature, humidity, and atmospheric pollutants. The device failure rate will vary depending upon the type of geographica...

The reliability of electronic devices depends on the environmental loads at which they are exposed. Climatic conditions vary greatly from one geographical location to another (from hot and humid to cold and dry areas), and the temperature and humidity vary from season to season and from day to day. High levels of temperature and relative humidity m...

Climate factors such as humidity and temperature have a significant impact on the corrosion reliability of electronic products. Given the huge geographical variability in climate conditions globally, a climate classification is a useful tool that simplifies the problem of considering climate when designing electronics packaging. Most current guidel...

A printed circuit board (PCB) surface can fail by corrosion due to various environmental factors. This paper focuses on machine learning (ML) techniques to build predictive models to forecast PCB surface failure due to electrochemical migration (ECM) and leakage current (LC) levels under corrosive conditions containing the combination of six critic...

This paper presents the probabilistic study of time to failure (TTF), which is caused by combinations of various important controllable factors on a printed circuit board (PCB) surface under humidity. The study investigated the impact of four changeable factors including pitch distance, temperature, contamination, and voltage, each at three levels...

Dicarboxylic acid flux activators are used in no-clean wave solder flux formulation for activating the solder surfaces on Printed Board Assembly (PBA) during the soldering process. However, flux residues containing dicarboxylic acid chemistry on PBA can cause adverse corrosion issues under humid conditions due to its hygroscopic and acidic nature....

This chapter presents a collection of the case studies related to corrosion of electronics, which are a manifestation of the failure modes and mechanisms described theoretically in earlier chapters 1–5chapter 1chapter 2chapter 3chapter 4chapter 5. A variety of field returns and testing results have been described in the literature, and the exemplar...

This chapter describes the theory of corrosion from the thermodynamics and kinetics point of view. The mechanisms described are related to the scenarios relevant for the electronics applications, with the critical aspects influencing corrosion in electronic devices briefly explained and backed by the examples demonstrating their importance. The sec...

This chapter broadly describes the type of contamination found in the electronic devices today and originating from the components, materials, manufacturing, and the assembling processes. The severity of residues is discussed in terms of their interaction with moisture under varying temperature and humidity conditions and their assistance in format...

This chapter gives an overview on measures that can be adopted for improving corrosion reliability of electronic devices. The preventive measures are listed and categorized into two general categories: intrinsic and extrinsic methods for ensuring a better robustness against the detrimental climatic exposure. The former approach relates to any desig...

This introductory chapter briefly describes the complexity of the nature of electronics corrosion related to the need for an interdisciplinary approach in defining the failure mechanisms and root causes of the observed failures. The history of development of modern electronics is outlined, starting from a basic discovery of an electron to the way e...

This chapter is a collection of selected methods commonly used for corrosion reliability testing, related quality control, and failure analysis in the electronics industry. These include chemical, electrochemical, and spectroscopic methods that characterize the presence and influence of contamination on the extent of corrosion of a given electronic...

This chapter briefly describes the manufacturing process of electronic board assemblies where the structure and characteristics of the printed circuit board (PCB) are outlined together with the changes occurring to the materials and surface properties upon exposure to humidity. Further, various types of PCB surface finishes and protective coatings...

This chapter describes the concept of moisture in the air and interaction with surfaces under varying temperature and humidity conditions. The interaction of humidity with various electronic surfaces is broadly outlined in terms of water film formation where the mechanisms of interactions are explained and, wherever applicable, backed by the mathem...

In present study, nanosized iron oxides particles are synthetised by easy one step precipitation from Mohric salt (NH4)2Fe(SO4)2·6H2O reacting with sodium hydroxide solution in temperature up to 60 °C. When changing the time of reaction, the iron oxide particles of different shape are prepared and when drying wet extracted particles at elevated tem...

Experiments using the Design of Experiment (DoE) methodology were carried out to investigate the effects of pitch distance (P), temperature (T), voltage (V), and contamination (C) on the leak current measured on surface insulation resistance (SIR) test boards. A 2⁴ full factorial design with eight replications was performed, and the response was me...

Effects of alkanolamine molecules on the corrosion inhibition of L80-1Cr steel were studied in a CO2-saturated 1 wt% NaCl solution at well downhole temperatures of 20 and 80°C. The electrochemical results showed lower corrosion rates at 20°C, for which corrosion rates were more influenced by the alkanolamine injection. The experimental results and...

Humidity and Electronics: Corrosion Reliability Issues and Preventive Measures provides comprehensive information on humidity related corrosion reliability issues surrounding electronics and how to tackle potential issues from a pro-active-design-prevention perspective. The book contains a mix of academic and industrial relevance, making it suitabl...

Water in its various forms can affect the performance and reliability of today’s electronics in unique ways. This paper discusses the forms of water and the degradation effect of water on electronics, identifies the types of failure mechanisms in electronics induced by liquid and vapor phase water, presents case studies of water-related failures, a...

Ionic residues resulting from the soldering process is an important parameter in connection with humidity robustness of Printed Circuit Board Assemblies (PCBAs) due to their ability to enhance moisture absorption and surface conductivity. For reflow process, residues are trapped under the components, and the morphology of the residues can change wi...

1 Cr steel as a metallic material is widely used for many applications in various industries, especially in the oil and gas. This is mainly due toits acceptable mechanical properties, low price, and the availability. Therefore, its corrosion mechanism(s) in different corrosive media hasbeen the aim of many research works in the last few decades. In...

Corrosion of production tubing used for Oil and Gas application is a big challenge. Despite using various mitigation techniques (e.g. inhibitors), the most commonly used material in sweet condition (L80-1Cr) is susceptible to extensive corrosion, which results in increased operational expenses. It has been reported [1] that CO2 corrosion is influen...

Corrosion is an unavoidable issue in oil and gas industry, and there are several techniques to control corrosion. Corrosion inhibitors are one ofthe most widely used and economically viable technique protecting metals against corrosion. Typical corrosion inhibitors are toxic organiccompounds, therefore have an environmental impact. Considering the...

This paper investigates the effect of calcium on the CO2 corrosion behaviour of 1Cr carbon steel under the effect of flow. The experiments were performed in a flow loop system in 1 wt-% NaCl solution at 80°C, pH = 6.34 with initial SCaCO3 = 2 and pCO2 = 0.53 bar. The flow velocity was kept at 3 m s⁻¹ and the system was pressurised to 3 bar. The cor...

Corrosion reliability of hearing aid (HA) devices is a critical issue due to their exposure to harsh climatic conditions like high humidity and temperature, along with the combination of high level of salt contamination from human sweat and environmental pollutants. Statistical analysis of corrosion failure data can provide a better understanding o...

The use of reflow flux system for soldering process of SMT electronics results in the concealed residues located underneath of the components, which changes its characteristics upon exposure to humidity. In this paper, the transformation of reflow process-related solder flux residues was investigated under varied humidity and temperature conditions...

In this work, Fluoropolymer-based ultrathin coating is evaluated as a protective barrier for Printed Circuit Board (PCB) against corrosion failures. Constant humidity with temperature cycling was applied as external climatic conditions for performance assessment through electrochemical AC impedance and DC potentiostatic measurements. Morphology of...

This paper studied the effect of embossing on the microstructure and corrosion behaviour of an Al−1.1 wt%Mn sheet. The microstructure of the embossed Al−1.1 wt%Mn sheets was studied by differential interference contrast microscopy, Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Energy Dispersive x-ray Spectroscopy (EDS)...

At the “cold-end” of biomass and coal-fired plants, with decreasing temperature and increasing relative humidity (RH) of the flue gas, moisture absorption by the hygroscopic deposits may electrochemically cause corrosion of the metal parts, especially during the downtime. In this paper, 10 deposit samples were collected from different sections of b...

This paper systematically investigates the humidity robustness and solderability of five alkanolamines used as activators in flux systems, and their effect was assessed along with the influence of soldering temperature. Electrochemical impedance spectroscopy and chronoamperometry techniques were used to obtain a better understanding of water adsorp...

This study examined the composition and characteristics of scales formed at different depths in an oil production well, which had developed over years of well operation, workovers, and interventions, by the combined use of optical microscopy, scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, transmission electron microscopy, and X...

This paper presents the investigation on the effect of calcium on the corrosion behavior of 1Cr carbon steel under various levels of initial CaCO3 saturation () of the bulk solutions. All the experiments were performed at 80°C in 1 wt% aqueous NaCl solution saturated with CO2. Four initial levels were investigated, namely 0, 0.6, 2, and 10. The cor...

A common concern with electronics packaging is the reduction of moisture ingress into the devices. One option to consider is the use of water absorption desiccant. Its criteria for selection should be its water capacity property, while its regeneration temperature has to be taken into account. Electronic devices are exposed to all kind of harsh cyc...

Sn–Ag–Cu solder alloys were usually modified using trace elements to achieve various properties. This paper investigated the effect of additives of Ni, Bi, and Sb on the microstructure and corrosion behavior of SAC alloys under application condition. Investigation was carried out using both solder alloy ingots and reflow-soldered surface insulation...

Electronic devices are exposed to a variety of climatic conditions worldwide. The day/night temperature fluctuations between the device interior and external conditions can lead to the formation of transient conditions within the enclosure that enhance the possibility of water layer build-up on the surface of Printed Circuit Board Assembly (PCBA)....

This paper presents the investigation on the effect of temperature on the corrosion behavior of 1Cr carbon steel at 40 °C and 80 °C in 1 wt. % NaCl aqueous solution saturated with CO2. The evolution of the corrosion process was followed with Linear Polarization Resistance (LPR) and Electrochemical Impedance Spectroscopy (EIS). X-ray Computed Tomogr...

The reliability of printed circuit boards (PCB) is at risk due to continuous miniaturization. As a result, PCBs are more susceptible to external factors such as humidity, temperature, contamination, etc., which affect their general performance, leading to failure of electronic devices. Therefore, protection of the devices against these factors is g...

Hydrothermal treatment of sputtered Al-Zr and Al-Ti coatings was performed in an autoclave. Electron microscopy of generated conversion layers revealed dual layered boehmite films. Needle morphology at top, and thin compact oxide at interface with metal substrate was observed. X-ray Energy Dispersive, and photoelectron spectroscopy revealed enrichm...

During the past couple of decades, use of electronic systems have has increased in gigantic proportions. Use of power electronics in various sectors is a typical example as well as electrification of automotive. The device needs to be highly reliable for use in various climatic conditions. Humidity can cause reliability issues in electronics result...

This study investigates the effect of CaCO3 precipitation on the corrosion of 1Cr carbon steel covered by protective FeCO3 layer. Tests were conducted at atmospheric pressure in 1 wt.% NaCl solution saturated with CO2 at 80 °C. Three different concentrations of Ca²⁺ (100, 1,000 and 10,000 ppm by mass) were studied. Linear polarization resistance (L...

Hydrothermal treatment of sputtered Al-Zr and Al-Ti coatings was performed in an autoclave. Electron microscopy of generated conversion layers revealed dual layered boehmite films. Needle morphology at top, and thin compact oxide at interface with metal substrate was observed. X-ray Energy Dispersive, and photoelectron spectroscopy revealed enrichm...

Purpose: The purpose of this paper is to investigate the decomposition behavior of binary mixtures of organic activators commonly used in the no-clean wave flux systems upon their exposure to thermal treatments simulating wave soldering temperatures. The binary blends of activators were studied at varying ratios between the components. Design/meth...

Producing pure H2 and O2 to sustain the renewable energy sources with minimal environmental damage is a key objective of photo/electrochemical water-splitting research. Metallic Ni-based electrocatalysts are expensive and eco-hazardous. This has rendered the replacement or reduction of Ni content in Ni-based electrocatalysts a decisive criterion in...

High frequency (HF) pulse anodising of a recycled AA5006 Aluminium alloy has been investigated to understand the effect of pulse anodising on improvements in optical quality of anodised surfaces in a sulphuric acid bath. The investigation includes the effect of applied voltage and pulse frequency on the anodising kinetics and optical properties of...

Investigation of premature blistering and delamination of coated AA5006 window frames using scanning (SEM)and transmission electron microscopy (TEM), glow discharge optical emission spectroscopy, and X-ray photoelectron spectroscopy (XPS)is presented. SEM of the blisters revealed corrosion of Aluminium and accumulation of corrosion products at the...

Nickel cobaltite (NCO) attains the apex of Sabatier-type volcano plot for electrochemical reaction compared to simple oxides due to synergetic effect of mixed transition metal cations. The combination of high surface area, aspect ratio, and porosity of electrospun NCO nanofibers (NCO-NF) enhance their electrocatalytic performance by improved electr...

The reliability issues faced by modern electronic devices are inherently related to the non-optimized manufacturing process, which leaves behind a substantial amount of soldering residues of an aggressive nature. The use of flux systems for soldering purposes is vital, however, upon exposure of the device to harsh climatic conditions, it can result...

The use of no-clean flux technology for the wave soldering process of a printed circuit board assembly (PCBA) influences the humidity-related robustness of the electronic devices due to the ionic residues remaining on the PCBA surface after soldering. This paper investigates the effect of various no-clean solder flux chemistries on the formation of...

Aim of this paper is to demonstrate the use of circuit analysis to predict humidity robustness of an electronic circuit design. There is a lack of design tools which can predict failures due to humidity, especially the effect of humidity on electrical functionality of circuits. This work provides a methodology for utilising circuit simulation tools...

The current medical technology necessitates the usage of biodegradable metals like Magnesium (Mg) as the future implant material due to the numerous benefits it can provide. Therefore, new Magnesium-based rare earth alloys targeting biomedical applications were synthesized using Disintegrated Melt Deposition (DMD) technique followed by hot-extrusio...

High frequency pulsed anodising of pure aluminium was investigated with an aim to understand the effect of the anodising parameters on the growth kinetics of the anodic layer and optical appearance of the anodised surface. Anodising was performed in sulphuric acid, and the effect of the pulse duty cycle, applied potential offset, and pulse frequenc...

Nanoporous anodic aluminum oxides (AAOs) are used as templates in various technological applications, including load-bearing aircraft structures. But in spite of their popularity, the important aspects that control their (dis-)bonding to an organic coating are not fully understood. To study the mechanisms behind the negative effect of fluorides on...

The ionic residues of activator compounds used in the no-clean solder flux systems often remain on a Printed Circuit Board Assembly surface after the soldering process and may compromise the corrosion reliability of electronic device upon exposure to humid environment. The solder flux formulations contain weak organic acids (WOAs) activators of dif...

Nickel cobaltite (NCO) nanofibers were synthesized using poly(styrene-co-acrylonitrile) (SAN) as the polymeric binder through sol–gel assisted electrospinning. Defect-free precursor nanofiber mats were pyrolyzed at 773 K at three different pyrolysis soaking times t = 2, 4, and 6 h. The SAN present in the precursor nanofibers caused morphological ch...

The current medical technology necessitates the usage of biodegradable metals like Magnesium (Mg) as the future implant material due to the numerous benefits it can provide. Therefore, new Magnesium-based rare earth alloys targeting biomedical applications were synthesized using Disintegrated Melt Deposition (DMD) technique followed by hot-extrusio...

The aim of this paper is to model moisture ingress into a closed electronic enclosure under isothermal and non-isothermal conditions. As a consequence, an in-house code for moisture transport is developed using the Resistor-Capacitor (RC) method, which is efficient as regards computation time and resources. First, an in-house code is developed to m...

The presence of solder flux residues on the printed circuit board assembly surface is an important factor contributing to humidity-related reliability issues that affect device lifetime. This investigation focuses on understanding the hygroscopic nature of typical wave solder flux activators—weak organic acids—under varied temperature conditions. I...

Aluminium alloys AA3102 and AA9108 were treated with high temperature steam, which resulted in the formation of an oxide layer of average thickness of 300–400 nm. Hydrothermal steam treatment resulted in the removal or oxidation of Al (Fe) Mn and Al (Fe-Si) Mn type intermetallic particles present in the alloys. Furthermore, electron energy loss spe...

Moisture uptake of polymer materials used for electronic packaging and moisture ingress into automotive electronic sensor housings have been studied by exposure to constant and cyclic humidity and temperature conditions. The first-level housing is made of epoxy molding compound (EMC) and encapsulates the sensor silicon-chip. The second-level housin...

Electronic devices are exposed to a wide range of climatic conditions. This study shows a reliability prediction of electronic devices exposed to different climates (from arid to humid and cold to hot regions). Temperature and humidity probability distribution functions have been calculated to indicate the change of climate exposure along year. Whi...

This paper investigates the water film buildup on solder masked printed circuit board assembly (PCBA) laminates under humid conditions. The effects of solder mask surface chemistry, morphology, and roughness were investigated using different commercial laminates coated with solder mask. Chemical composition of the materials was analyzed using Fouri...

De-icing salts are commonly used on European roads during winter and are usually based on chlorides of sodium, magnesium, or calcium. The salt selection depends on the local climate and legislation. Therefore, the chemical composition of the de-icing mixture can be very different within Europe. This represents an important challenge for the automot...

The effects of hygroscopic atmospheric particles are investigated in relation with corrosion of tin. Surface insulation resistance test boards were directly contaminated both with ambient particles sampled in the field at Milan (Italy) and with pure saline particles generated in the laboratory. An innovative particle deposition device was used to u...

A combination of glow discharge optical emission spectroscopy sputtering and local electrochemical measurements was used to determine electrochemical changes upon brazing in a multi-layered Aluminium sheet (AA4343/AA3xxx/AA4343) with an additional low-Cu (AA3xxx) interlayer. Ecorr values from potentiodynamic polarization, galvanic corrosion behavio...

The presence of solder flux residue on the Printed Circuit Board Assembly (PCBA) surface compromises the corrosion reliability of electronics under humid conditions and can lead to degradation of the device's lifetime. In this work, the effect of solder mask morphology and hygroscopic residues were studied towards assessment of their influence on t...