Balázs Illés

• Doctor of Engineering
• Budapest University of Technology and Economics

Soldering with Sn alloys has always been the essential assembly step of microelectronics. The conductive Sn whiskers, which can spontaneously grow from soldering surfaces, mean a considerable reliability risk for microelectronics due to possible short circuit formation between the leads of the components. Since their discovery in 1951, thousands of...

This study investigates the mechanism and effects of incorporating different ZrO2 nano-particles into SAC0307 solder alloys. ZrO2 nano-powder and nano-fibers in 0.25–0.5 wt% were added to the SAC0307 alloy to prepare composite solder joints by surface mount technology. The solder joints were shear tested before and after a 4000 h long 85 °C/85% RH...

In this paper, the design and research of a sensor-based personal air-quality monitoring device are presented, which is retrofitted into different personal protective face masks. Due to its small size and low power consumption, the device can be integrated into and applied in practical urban usage. We present our research and the development of the...

In the present study, the effect of four oxide ceramics (TiO2, ZnO, ZrO2, and CuO) as reinforcements were investigated on the soldering parameters of the SAC 0307 solder alloy. The oxide ceramics were used in nano-powder format. Composite solder pastes were composed by the standard ball milling process of the nano-particles into the SAC 0307 solder...

This paper gives a review of different applications in the numerical modelling of reflow soldering technology from recent years. The focus was on detailing the different process types, the physical background, and related mathematical models. Reflow soldering is the main connection technology of surface mounting. Firstly, the solder in paste form i...

In this paper, we investigated the applicability of ChatGPT AI in electronics research and development via a case study of applied sensors in embedded electronic systems, a topic that is rarely mentioned in the recent literature, thus providing new insight for professionals and academics. The initial electronics-development tasks of a smart home pr...

The COVID-19 outbreak increased demand for personal protective respirator masks. Textile masks based on cloth materials appeared to be a sustainable, comfortable, and cost-effective alternative available in global communities. In this study, we used laser-based particle counting for mask material qualification to determine the concentration filteri...

The effect of SiC nano-phases (nano-particles and nano-fibers) addition into SAC0307 solder paste was investigated on the thermal and microstructural properties of the composite solder joints. The nano-phases were used between 0.125 – 1 wt%, and they were mixed into the solder paste by ball milling process. For the study power MOSFET (metal oxide s...

The main joining process of the electronic industry is still soldering with different alloys of Sn. This work studied the relationship between Sn whisker growth and corrosion resistance of 99Sn0.3Ag0.7Cu-TiO2/ZnO (0.25wt%) composite solder alloys in a corrosive environment via scanning electron microscopy and focused ion beam techniques. The corros...

This review covers recent applications of wet etching on solder alloys. Detailed characterization cases are presented and discussed accordingly to highlight the process flow and applicability of conventional, deep etching, and selective etching techniques. A brief introduction of solder alloys and the concepts of each etching methods are described...

Stencil printing is the most crucial process in reflow soldering for the mass assembly of electronic circuits. This paper investigates different machine learning-based methods to predict the essential process characteristics of stencil printing: the area, thickness, and volume of deposited solder paste. The training dataset was obtained experimenta...

In this paper transient condensation and heat transfer been investigated on a printed circuit board (PCB) and a surface mounted (SMD) capacitor during a vapour phase reflow soldering (VPS) process. Classic VPS processes provide rapid heating with high heat transfer coefficient rates due to condensation that forms a continuous liquid film on the sur...

In this paper, the effect of different thermocouple constructions on the hot spot temperature are investigated with a modelling approach to achieve more precise soldering profile acquisition and failure analysis at different reflow soldering heat transfer methods. The paper focuses on convection-based reflow and condensation based vapour phase sold...

Purpose This paper aims to present the results of investigations that show the influence of ZnO composite soldering paste on the optical and thermal parameters of power light-emitting diodes (LEDs). Design/methodology/approach ZnO nanocomposite solder alloys were produced via the ball milling process from the solder paste Sn99Ag0.3Cu0.7 (SACX0307)...

Flux contained in solder paste significantly affects the process of solder joint creation during reflow soldering, including the creation of an intermetallic layer (IML). This work investigates the dependence of intermetallic layer thickness on ROL0/ROL1 flux classification, glossy or matt solder mask, and OSP/HASL/ENIG soldering pad surface finish...

Electrochemical Migration (ECM) is getting more attention in the microelectronics industry due to the continuing miniaturization, which increases the possibility of short circuit formation caused by the ECM-induced dendrites. This work presents a 2D numerical model of the ECM based on the Nernst-Plank equation. The model contains the deterministic...

Respiratory parameters, such as respiratory rate (RR), inhalation time (tin), exhalation time (tex), and their ratio (IER=tin/tex), are of great importance to indicate clinical differences between healthy people and those with respiratory diseases. Herein, we report a respiration monitoring triboelectric nanogenerator (RM-TENG) with nanofibrous mem...

The effect of solder joint fabrication on the thermal properties of IGBTs soldered onto glass-epoxy substrate (FR4) was investigated. Glass-epoxy substrates with a thickness of 1.50 mm, covered with a 35 μm thick Cu layer, were used. A surface finish was prepared from a hot air leveling (HAL) Sn99Cu0.7Ag0.3 layer with a thickness of 1 ÷ 40 μm. IGBT...

The properties of Sn99Ag0.3Cu0.7 (SACX0307) solder alloy reinforced with ZnO nanoparticles were investigated. The primary ZnO particle sizes were 50, 100, and 200 nm. They were added to a solder paste at a ratio of 1.0 wt %. The wettability, the void formation, the mechanical strength, and the thermoelectric parameters of the composite solder alloy...

Featured Application Enhancing design rules of complex printed circuit boards—electronic assembly process optimization in the early design phase. Abstract The pin-in-paste technology is an advancing soldering technology for assembling complex electronic products, which include both surface-mounted and through-hole components. A computational fluid...

Featured Application The paper presents the application of pressure sensors and the obtained pressure/height profiles next to the generally used soldering temperature profiles for precise control of heat-level type vapour phase reflow soldering ovens in electronics manufacturing. Abstract Electronic manufacturing principles are continuously develo...

In the past years, the use of low silver content SAC0307 (99Sn0.3Ag0.7Cu wt%) solder alloy grew considerably due to its good soldering quality. In the latest version of this alloy, manganese, and bismuth are used to improve further its soldering parameters. In this study, a reliability issue, the whisker growth from SAC0307-Mn07 and SAC0307-Bi1-Mn0...

Respirators are one of the most useful personal protective equipment which can effectively limit the spreading of coronavirus (COVID-19). There are a worldwide shortage of respirators, melt-blown non-woven fabrics, and respirator testing possibilities. An easy and fast filtering efficiency measurement method was developed for testing the filtering...

Manganese can be an optimal alloying addition in lead-free SAC (SnAgCu) solder alloys because of its low price and harmless nature. In this research, the mechanical properties of the novel SAC0307 (Sn/Ag0.3/Cu0.7) alloyed with 0.7 wt.% Mn (designated as SAC0307-Mn07) and those of the traditionally used SAC305 (Sn96.5/Ag3/Cu0.5) solder alloys were i...

The kinetics of Sn whisker growth was investigated on vacuum-evaporated Sn thin-films. Sn film layers were deposited on a Cu substrate with 0.5 and 1 µm thicknesses. The samples were stored in room conditions (22 ± 1 °C/50 ± 5RH%) for 60 days. The Sn whiskers and the Cu–Sn layer structure underneath them were investigated with both scanning electro...

Tin–silver–copper (SAC) solder alloys are the most promising candidates to replace Sn–Pb solder alloys. However, their application is still facing several challenges; one example is the electrochemical corrosion behaviour, which imposes a risk to electronics reliability. Numerous investigations have been carried out to evaluate the corrosion perfor...

Face masks are becoming one of the most useful personal protective equipment with the outbreak of the coronavirus (CoV) pandemic. The entire world is experiencing shortage of disposable masks and melt-blown non-woven fabrics, which is the raw material of the mask filter. Recyclability of the discarded mask is also becoming a big challenge for the e...

Purpose The purpose of this paper is to investigate the effect of different viscosity models (Cross and Al-Ma’aiteh) and different printing speeds on the numerical results (e.g. pressure over stencil) of a numerical model regarding stencil printing. Design/methodology/approach A finite volume model was established for describing the printing proce...

Purpose The purpose of this paper is to investigate the morphology of intermetallic (IMC) compounds and the mechanical properties of SAC305 solder alloy under different cooling conditions. Design/methodology/approach SAC305 solder joints were prepared under different cooling conditions/rates. The performance of three different etching methods was...

Purpose The paper aims to present an investigation on heat transfer in a vapour phase soldering (VPS) oven, focusing on the differences of horizontally and vertically aligned Printed Circuit Board (PCB) surfaces. The investigation can help develop a better understanding of the process and provide information for future modelling of the process. De...

The effect of the microstructure of solder joints on the thermal properties of power LEDs is investigated. Solder joints were prepared with different solder pastes, namely 99Sn0.3Ag0.7Cu (as reference solder) and reinforced 99Sn0.3Ag0.7Cu–TiO2 (composite solder). TiO2 ceramic was used at 1 wt.% and with two different primary particle sizes, which w...

The effect of recrystallization of 99.3Sn–0.7Cu wt. % solder alloy on the allotropic transition of β to α-Sn (so-called tin pest phenomenon) was investigated. Bulk samples were prepared, and an InSb inoculator was mechanically applied to their surfaces to enhance the transition. Half of the samples were used as the reference material and the other...

This work aims to provide deep morphological observation on the incorporated TiO2 nanoparticles within the SAC305 by selective electrochemical etching. Cyclic voltammetry and chronoamperometry were used to investigate the selective etching performances. The removal of β-Sn matrix was conducted at a fixed potential of −350 mV. Average performances o...

In this chapter, the die-attach technologies and the relating techniques and evaluation methods are overviewed. A brief introduction is presented into the type of first-level interconnections, like wire-bonding, tape-automated bonding, and flip-chip technologies. From the substrates’ point of view, direct copper bonding is illustrated. Besides, the...

Global demand for better quality in electronics assembly drives a section of the industry to rethink and reinvent conventional technologies. While lead-free and mass manufacturing pointed toward convection-based reflow soldering, the higher component, and function density, the constantly widening spectrum of component, carrier substrate and alloy t...

In this chapter, selected examples of numerical simulation methods in the field of reflow soldering technologies are presented. Recently, the numerical simulation is getting more and more important, not only in the scientific researches but in the industrial applications as well. Generally, the numerical models offer fast, easy, and flexible soluti...

In this chapter, the infrared reflow soldering is presented starting from the basics, to the most recent application. The chapter starts with presenting the physical basics of the infrared heating, also highlighting the difference between equilibrium and nonequilibrium reflow cases. The basic configurations of IR ovens are sorted by the wavelength...

In this chapter, the surface-mount technology and reflow soldering technology are overviewed. A brief introduction is presented into the type of electronic components, including through-hole and surface-mounted ones. Steps of reflow soldering technology are outlined, and details are given regarding the properties of solder material in this technolo...

This chapter presents the general operating principle and usual applications of convection reflow ovens. Conveyor-type convection reflow ovens are still the most frequently used soldering devices by electronics manufacturers. Their advantages are precise thermal management and high productivity. However, from the other side, their flexibility is lo...

Purpose In this paper, analytical modelling of heat distribution along the thickness of different printed circuit board (PCB) substrates is presented according to the 1 D heat transient conduction problem. This paper aims to reveal differences between the substrates and the geometry configurations and elaborate on further application of explicit mo...

The effect of copper substrate roughness and tin layer thickness were investigated on whisker development in the case of Sn thin-films. Sn was vacuum-evaporated onto both unpolished and mechanically polished Cu substrates with 1 µm and 2 μm average layer thicknesses. The samples were stored in room conditions for 60 days. The considerable stress—de...

Purpose The purpose of the paper is to improve the control of vapour phase soldering (VPS). To enable better productivity and assembling quality, the industry needs to provide precise control and measurements during assembling. In the paper, a special monitoring method is presented for VPS to enable improved process control and oven state identific...

Purpose This paper aims to investigate the self-alignment of 0603 size (1.5 × 0.75 mm) chip resistors, which were soldered by infrared or vapour phase soldering. The results were used for establishing an artificial neural network for predicting the component movement during the soldering. Design/methodology/approach The components were soldered...

In this paper, the relationship between the crystallographic structure of Cu-Sn intermetallic grains and Sn whisker growth was investigated. In order to prevent the influence of the elements in the alloy composition and the effect of the soldering process on the formation of the intermetallic layer, 99.99% pure Sn was vacuum evaporated onto Cu subs...

The authors’ institutions are Partners in the VINMES network (Visegrad Network for Microelectronics Engineering Scientists), and they are conducting a Visegrad Fund project about “V4 Seminars for young scientists on publishing techniques in the field of engineering science”. The aims of the project are the enhancement and support the scientific pub...

In this paper, the complex heat transfer process of the vapour phase soldering has been investigated on the level of electronic components. VPS is gaining increased attention lately, and the process needs alternative approaches in modelling, compared to conventional soldering processes in electronics mass manufacturing. Component level modelling wa...

Purpose This paper aims to present a review of the recent developments in vapour phase soldering (VPS) technology. This study focuses on the following topics: recent developments of the technology, i.e. soft and vacuum VPS; measurement and characterization methods of vapour space, i.e. temperature and pressure; numerical simulation of the VPS solde...

The reflow soldering process of large size components was always problematic in microelectronics manufacturing due to the possibility of component displacement failures after soldering; like tombstone formation or skewing, which can be traced back to the different heating of the opposite component sides. During vapour phase soldering, the efficienc...

The thixotropic behaviour of different type lead-free solder pastes (Type 3: particle size: 20–45 μm; Type 4: 20–38 μm; Type 5: 10–25 μm) was investigated and compared. The viscosity decrease during the first stencil printing cycles is also described. The measurements were carried out with a rheometer using serrated parallel plates by sweeping the...

Purpose This paper aims to investigate the quality and reliability of solder joints prepared from Pb-free alloys on direct bounded Cu (DBC) substrates. Two types of solder alloys were studied: Sn90.95Ag3.8Cu0.7Sb1.4Ni0.15Bi3.0, with a high melting point of 225°C, and Sn42Bi58, with low a melting point of 138°C. Design/methodology/approach Capaci...

Hyperfine interactions in tin-base alloys Sn-x%Ag-y%Cu (x = 0, 0.3, 3; y ∈ 0 ÷ 3) were studied using ¹¹⁹Sn Mössbauer spectroscopy in order to detect the conditions that promote α-Sn phase formation in metallic tin (β-Sn). In many engineering applications, so-called grey tin or tin pest (α-Sn) is a parasitic phase that weakens the mechanical propert...

Purpose The vacuum vapour phase soldering method was investigated by numerical simulations. The purpose of this study was to examine the temperature changes of the solder joints during the vapour suctioning process. A low pressure is used to enhance the outgassing of the trapped gas within the solder joints, which otherwise could form voids. Howev...

Purpose The attack angle of stencil printing squeegees with different geometries was analysed using finite element modelling. Design/methodology/approach A finite element model (FEM) was developed to determine the attack angle during the stencil printing. The material properties of the squeegee were included in the model according to the paramet...

The heat and mass transport processes were investigated with numerical simulations in a vacuum vapour phase soldering system during the vapour suctioning process. Low vapour pressure/concentration is applied during vacuum soldering to decrease the number of gas voids in the solder joints. Three-dimensional numerical flow model was developed which b...

In this paper, the allotropic transition of ß to α-Sn (so called “tin pest”) was identified with electrical resistance measurements. Samples were prepared from SnCu1 alloy using mechanical treatment of two different sample sizes, artificially inoculated with InSb and stored at −18°C for 9 weeks. The electrical resistance measurement showed that in...