Daniel Straubinger, István Bozsóki, David Bušek, Balázs Illés and Attila Géczy
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…
Abstract
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 modelling.
Design/methodology/approach
Different substrates were considered: classic FR4 and polyimide, ceramics (BeO, Al2O3) and novel biodegradables (polylactic-acid [PLA] and cellulose acetate [CA]). The board thicknesses were given in 0.25 mm steps. Results are calculated for heat transfer coefficients of convection and vapour phase (condensation) soldering. Even heat transfer is assumed on both PCB sides.
Findings
It was found that temperature distributions along PCB thicknesses are mostly negligible from solder joint formation aspects, and most of the materials can be used in explicit reflow profile modelling. However PLA shows significant temperature differences, pointing to possible modelling imprecisions. It was also shown, that while the difference between midplane and surface temperatures mainly depend on thermal diffusivity, the time to reach solder alloy melting point on the surface depends on volumetric heat capacity.
Originality/value
Results validate the applicability of explicit heat transfer modelling of PCBs during reflow for different heat transfer methods. The results can be incorporated into more complex simulations and profile predicting algorithms for industrial ovens controlled in the wake of Industry 4.0 directives for better temperature control and ultimately higher soldering quality.
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Daniel Straubinger, Attila Toth, Viktor Kerek, Zsolt Czeczei, Andras Szabo and Attila Geczy
The purpose of this paper is to study the solder beading phenomenon (referring to larger-sized solder balls) of surface-mounted electrolytic capacitors. Solder beading could…
Abstract
Purpose
The purpose of this paper is to study the solder beading phenomenon (referring to larger-sized solder balls) of surface-mounted electrolytic capacitors. Solder beading could induce failures by violating the minimal electrical clearance on the printed circuit board (PCB). In modern lead-free reflow soldering, especially in high-reliability industries, such as automotive, aeroplane and aerospace, detecting and preventing such defects is essential in reliable and cost-effective manufacturing.
Design/methodology/approach
The large size of the involved components may block the view of automatic optical inspection; therefore, X-ray inspection is necessary. To detect the failure mode, X-ray imaging, cross-section grinding, optical microscopy and Fourier transformed infrared spectroscopy were used. High-resolution noncontact profilometry and optical microscopy were used to analyse component designs. The surface mounting process steps were also analysed to reveal their dependence on the issue. Test methods were designed and performed to reveal the behaviour of the solder paste (SP) during the reflow soldering process and to emphasise the component design relevance.
Findings
It was found that the reduction of SP volume only reduces the failure rate but does not solve the problem. Results show that excessive component placement pressure could induce solder beading. Statistical analysis revealed that differences between distinct components had the highest effect on the solder beading rate. Design aspects of solder beading-prone components were identified and discussed as the primary source of the problem.
Practical implications
The findings can be applied in surface-mount technology production, where the total failure count and resulting failure costs could be reduced according to the findings.
Originality/value
This paper shows that component design aspects such as the low distance between the underside of the component and the PCB and blocked proper outgassing of volatile compounds of the SP can be root causes of solder beading under surface-mounted electrolytic capacitors.
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Dániel Straubinger, Attila Géczy, András Sipos, András Kiss, Dániel Gyarmati, Oliver Krammer, Dániel Rigler, David Bušek and Gábor Harsányi
This paper aims to present a novel approach on investigating critical current densities in the solder joints of chip-size surface-mounted components or device (SMD) components and…
Abstract
Purpose
This paper aims to present a novel approach on investigating critical current densities in the solder joints of chip-size surface-mounted components or device (SMD) components and ball grid array (BGA) lead-free solder joints with the focus of via-in-pad geometries. The investigation involves a numerical approach and a physical validation with selected geometry configurations and high current loads to reveal possible failure sources. The work is a continuation of a previous study.
Design/methodology/approach
Current density was investigated using finite element modeling on BGA joints. Dummy BGA components, 0402 and 0603 zero ohm jumper resistors, were used, both in daisy chain setups on standard FR4 printed circuit boards (PCBs). Respective physical loading experiments were set to find effects of elevated current density at hot zones of the joints. Cross-section analysis, scanning electron microscopy and shear force tests were used to analyze the joints.
Findings
The findings reveal alterations in the joints, while the current loading is not directly affecting the structure. The modeling reveals the current density map in the selected formations with increased current crowding zones. Overall, the degradation does not reach the level of electromigration (EM)-induced voiding due to the limiting factor of the FR4 substrate.
Practical implications
The heavy current load affects joint reliability, but there are limitations of EM-induced failures on PCB-based assemblies due to the thermomechanical weakness of the FR4 material.
Originality/value
The experiments investigate current density from a novel aspect on frequently used BGA surface mounted components with modeling configurations focusing on possible effects of via-in-pad structure.
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Daniel Straubinger, István Bozsóki, Balazs Illes, Oliver Krammer, David Bušek and Attila Geczy
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…
Abstract
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.
Design/methodology/approach
For the investigations, flame retardant grade 4 (FR4) PCB plates and sealed plate–based boxes were immersed into saturated vapour of an experimental oven. The temperature and resulting heat transfer coefficients were analysed according to the sample boxes and the surface orientations. In addition, the boxes’ vapour consumption was investigated with pressure measurements.
Findings
The horizontal top- and bottom-side heating shows very similar results. In addition, the sides of a box were heated in a manner similar to the top and the bottom sides, but there was a slight increase in the heat transfer coefficient because of the vertical wall alignment. The pressure measurements reveal the dynamic changes in vapour after immersion of the boxes.
Practical implications
The findings may help to show differences on different surface orientations, pointing to more precise, explicit and multiphysics simulation results.
Originality/value
The experiments present an aspect of heat transfer coefficient differences in VPS ovens, also highlighting the effect of initial pressure drop inside the workspace of an oven.
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Attila Geczy, Daniel Straubinger, Andras Kovacs, Oliver Krammer, Pavel Mach and Gábor Harsányi
The purpose of this paper is to present a novel approach on investigating critical current densities in the solder joints of chip-size surface mounted device (SMD) components. The…
Abstract
Purpose
The purpose of this paper is to present a novel approach on investigating critical current densities in the solder joints of chip-size surface mounted device (SMD) components. The investigation involves a numerical approach and a physical validation with selected track-to-pad connections and high current loads (CXs).
Design/methodology/approach
During the investigations, shape of solder fillets was calculated in Surface Evolver, and then the current densities were calculated accordingly in the given geometry. For the verification, CX tests were performed on joints at elevated temperatures. The joints were qualified with X-ray microscopy, cross-section analysis and shear tests.
Findings
This study ascertained that the inhomogeneity in current density depends on the track-to-pad structure of the joint. Also this study found that the heavy CX decreases the mechanical strength, but the degradation does not reach the level of electromigration (EM)-induced voiding.
Practical implications
The heavy CX significantly affects joint reliability and the results point out to EM-induced failure-limitations on printed circuit board (PCB)-based assemblies due to the thermomechanical weakness of the FR4 material.
Originality/value
The experiments investigate current density from a novel aspect on more frequently used small-scale components with different track-to-pad configurations – pointing out possible failure sources.
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The primary driver of future aviation has recently been sustainability. The rapid development of radically new, disruptive technologies and solutions should be regularly evaluated…
Abstract
Purpose
The primary driver of future aviation has recently been sustainability. The rapid development of radically new, disruptive technologies and solutions should be regularly evaluated to maintain the desired trends in sustainable aviation. The purpose of this research can be listed as follows: (i) to propose a sustainable performance index and methodology (ii) to evaluate the new technologies and solutions, and (iii) apply them to evaluate the effect of technologies and solutions under development.
Design/methodology/approach
This paper introduces a total sustainable performance index for evaluating the sustainability; demonstrates its applicability to future development processes; recognizes the supporting new technologies and solutions by implementing their identification, evaluation and selection processes; and defines the major trends and drivers maintaining the sustainability of the future aviation.
Findings
This study has resulted in a proposed new “total sustainable performance index,” and methodology of identifying key drivers that allow defining the technology and solution-driven trends, and defines the major trends and listed technologies and solutions that may have a determining role in given trends.
Research limitations/implications
There are dilemmas on taking into account the positive effects of aviation on the economy and society that may overwrite the costs and limited information about the foresight on new technologies and solutions.
Practical implications
It depends on access to required inputs.
Social implications
Two-way effects of solid expectations of society on the possible greening of aviation can be listed as the social implication of this research.
Originality/value
The proposed “total sustainability performance index” totally evaluates sustainability, including a penalty, considering the policy (regulation) and interest of future generations.