Ji Li, Tom Monaghan, Robert Kay, Ross James Friel and Russell Harris
This paper aims to explore the potential of ultrasonic additive manufacturing (UAM) to incorporate the direct printing of electrical materials and arrangements (conductors and…
Abstract
Purpose
This paper aims to explore the potential of ultrasonic additive manufacturing (UAM) to incorporate the direct printing of electrical materials and arrangements (conductors and insulators) at the interlaminar interface of parts during manufacture to allow the integration of functional and optimal electrical circuitries inside dense metallic objects without detrimental effect on the overall mechanical integrity. This holds promise to release transformative device functionality and applications of smart metallic devices and products.
Design/methodology/approach
To ensure the proper electrical insulation between the printed conductors and metal matrices, an insulation layer with sufficient thickness is required to accommodate the rough interlaminar surface which is inherent to the UAM process. This in turn increases the total thickness of printed circuitries and thereby adversely affects the integrity of the UAM part. A specific solution is proposed to optimise the rough interlaminar surface through deforming the UAM substrates via sonotrode rolling or UAM processing.
Findings
The surface roughness (Sa) could be reduced from 4.5 to 4.1 µm by sonotrode rolling and from 4.5 to 0.8 µm by ultrasonic deformation. Peel testing demonstrated that sonotrode-rolled substrates could maintain their mechanical strength, while the performance of UAM-deformed substrates degraded under same welding conditions ( approximately 12 per cent reduction compared with undeformed substrates). This was attributed to the work hardening of deformation process which was identified via dual-beam focussed ion beam–scanning electron microscope investigation.
Originality/value
The sonotrode rolling was identified as a viable methodology in allowing printed electrical circuitries in UAM. It enabled a decrease in the thickness of printed electrical circuitries by ca. 25 per cent.
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Jack Hinton, Dejan Basu, Maria Mirgkizoudi, David Flynn, Russell Harris and Robert Kay
The purpose of this paper is to develop a hybrid additive/subtractive manufacturing platform for the production of high density ceramic components.
Abstract
Purpose
The purpose of this paper is to develop a hybrid additive/subtractive manufacturing platform for the production of high density ceramic components.
Design/methodology/approach
Fabrication of near-net shape components is achieved using 96 per cent Al3O2 ceramic paste extrusion and a planarizing machining operations. Sacrificial polymer support can be used to aid the creation of overhanging or internal features. Post-processing using a variety of machining operations improves tolerances and fidelity between the component and CAD model while reducing defects.
Findings
This resultant three-dimensional monolithic ceramic components demonstrated post sintering tolerances of ±100 µm, surface roughness’s of ∼1 µm Ra, densities in excess of 99.7 per cent and three-point bending strength of 221 MPa.
Originality/value
This method represents a novel approach for the digital fabrication of ceramic components, which provides improved manufacturing tolerances, part quality and capability over existing additive manufacturing approaches.
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Robert W. Kay, Gerard Cummins, Thomas Krebs, Richard Lathrop, Eitan Abraham and Marc Desmulliez
Wafer-level stencil printing of a type-6 Pb-free SAC solder paste was statistically evaluated at 200 and 150 μm pitch using three different stencil manufacturing technologies…
Abstract
Purpose
Wafer-level stencil printing of a type-6 Pb-free SAC solder paste was statistically evaluated at 200 and 150 μm pitch using three different stencil manufacturing technologies: laser cutting, DC electroforming and micro-engineered electroforming. This investigation looks at stencil differences in printability, pitch resolution, maximum achievable bump height, print co-planarity, paste release efficiency, and cleaning frequency. The paper aims to discuss these issues.
Design/methodology/approach
In this paper, the authors present a statistical evaluation of the impact of stencil technology on type-6 tin-silver-copper paste printing. The authors concentrate on performances at 200 and 150 μm pitch of full array patterns. Key evaluated criteria include achievable reflowed bump heights, deposit co-planarity, paste release efficiency, and frequency of stencil cleaning. Box plots were used to graphically view print performance over a range of aperture sizes for the three stencil types.
Findings
Fabrication technologies significantly affect print performance where the micro-engineered electroformed stencil produced the highest bump deposits and the lowest bump height deviation. Second in performance was the conventional electroformed, followed by the laser-cut stencil. Comparisons between the first and fifth consecutive print demonstrated no need for stencil cleaning in the case for the micro-engineered stencil for all but the smallest spacings between apertures. High paste transfer efficiencies, i.e. above 85 per cent, were achieved with the micro-engineered stencil using low aperture area ratios of 0.5.
Originality/value
Stencil technology influences the maximum reflowed solder bump heights achievable, and bump co-planarity. To date, no statistical analysis comparing the impact of stencil technology for wafer-level bumping has been carried out for pitches of 200 μm and below. This paper gives new insight into how stencil technology impacts the print performance for fine pitch stencil printing. The volume of data collected for this investigation enabled detailed insight into the limitations of the printing process and as a result for suitable design guidelines to be developed. The finding also shows that the accepted industry guidelines on stencil design developed by the surface mount industry can be broken if the correct stencil technology is selected, thereby increasing the potential application areas of stencil printing.
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Ji Li, Thomas Wasley, Duong Ta, John Shephard, Jonathan Stringer, Patrick J. Smith, Emre Esenturk, Colm Connaughton, Russell Harris and Robert Kay
This paper aims to demonstrate the improved functionality of additive manufacturing technology provided by combining multiple processes for the fabrication of packaged electronics.
Abstract
Purpose
This paper aims to demonstrate the improved functionality of additive manufacturing technology provided by combining multiple processes for the fabrication of packaged electronics.
Design/methodology/approach
This research is focused on the improvement in resolution of conductor deposition methods through experimentation with build parameters. Material dispensing with two different low temperature curing isotropic conductive adhesive materials was characterised for their application in printing each of three different conductor designs, traces, z-axis connections and fine pitch flip chip interconnects. Once optimised, demonstrator size can be minimised within the limitations of the chosen processes and materials.
Findings
The proposed method of printing z-axis through layer connections was successful with pillars 2 mm in height and 550 µm in width produced. Dispensing characterisation also resulted in tracks 134 µm in width and 38 µm in height allowing surface mount assembly of 0603 components and thin-shrink small outline packaged integrated circuits. Small 149-µm flip chip interconnects deposited at a 457-µm pitch have also been used for packaging silicon bare die.
Originality/value
This paper presents an improved multifunctional additive manufacturing method to produce fully packaged multilayer electronic systems. It discusses the development of new 3D printed, through layer z-axis connections and the use of a single electrically conductive adhesive material to produce all conductors. This facilitates the surface mount assembly of components directly onto these conductors before stereolithography is used to fully package multiple layers of circuitry in a photopolymer.
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Stoyan Stoyanov, Chris Bailey and Marc Desmulliez
This paper aims to present an integrated optimisation‐modelling computational approach for virtual prototyping that helps design engineers to improve the reliability and…
Abstract
Purpose
This paper aims to present an integrated optimisation‐modelling computational approach for virtual prototyping that helps design engineers to improve the reliability and performance of electronic components and systems through design optimisation at the early product development stage. The design methodology is used to identify the optimal design of lead‐free (Sn3.9Ag0.6Cu) solder joints in fine‐pitch copper column bumped flip‐chip electronic packages.
Design/methodology/approach
The design methodology is generic and comprises numerical techniques for computational modelling (finite element analysis) coupled with numerical methods for statistical analysis and optimisation. In this study, the integrated optimisation‐modelling design strategy is adopted to prototype virtually a fine‐pitch flip‐chip package at the solder interconnect level, so that the thermal fatigue reliability of the lead‐free solder joints is improved and important design rules to minimise the creep in the solder material, exposed to thermal cycling regimes, are formulated. The whole prototyping process is executed in an automated way once the initial design task is formulated and the conditions and the settings for the numerical analysis used to evaluate the flip‐chip package behaviour are specified. Different software modules that incorporate the required numerical techniques are used to identify the solution of the design optimisation problem related to solder joints reliability optimisation.
Findings
For fine‐pitch flip‐chip packages with copper column bumped die, it is found that higher solder joint volume and height of the copper column combined with lower copper column radius and solder wetting around copper column have a positive effect on the thermo‐mechanical reliability.
Originality/value
The findings of this research provide design rules for more reliable lead‐free solder joints for copper column bumped flip‐chip packages and help to establish further the technology as one of the viable routes for flip‐chip packaging.
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Sharad Asthana and Rachana Kalelkar
This paper's purpose was to examine the impact of geomagnetic activity (GMA) on the timing and valuation of earnings information disclosed by firms every quarter.
Abstract
Purpose
This paper's purpose was to examine the impact of geomagnetic activity (GMA) on the timing and valuation of earnings information disclosed by firms every quarter.
Design/methodology/approach
The authors start the analyses with a sample of 112,669 client firms from 1989 to 2018. To analyze the impact of GMA on the earnings response coefficient (ERC), the authors use the three-day cumulative abnormal returns and cumulative abnormal returns for the extended post-earnings announcement window [2, 75] as the dependent variables. The authors interact unexpected earnings (UE) with the C9 Index, an index commonly used to measure GMA and study how GMA affects the pricing of new public information. To examine the effect of GMA on the timing of disclosure of earnings news, the authors regress a variant of the GMA index on the propensity to disclose bad earnings news.
Findings
The authors find significantly lower earnings response coefficients during periods of high GMA. This effect is permanent and stock prices do not correctly incorporate the implications of earnings information over time. The authors also show that managerial behavior is affected by GMA as well and the managers are more (less) likely to release bad (good) news during periods of higher activity. Finally, the authors also find that in situations where stakeholders are likely to rely on modern technology that depends minimally on humans, the adverse impact of GMA on the pricing of earnings information is mitigated.
Originality/value
The literature on the effect of GMA on the capital market is very limited and focuses primarily on stock returns, while the behavioral finance literature focuses on circumstances like weather, temperature and sporting outcome to study how the investors' mood affects their capital market behavior. The authors add to both the literature by investigating how GMA influences investors' and managers' behaviors in the capital market.
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Robert Kay and Marc Desmulliez
The purpose of this paper is to present a detailed overview of the current stencil printing process for microelectronic packaging.
Abstract
Purpose
The purpose of this paper is to present a detailed overview of the current stencil printing process for microelectronic packaging.
Design/methodology/approach
This paper gives a thorough review of stencil printing for electronic packaging including the current state of the art.
Findings
This article explains the different stencil technologies and printing materials. It then examines the various factors that determine the outcome of a successful printing process, including printing parameters, materials, apparatus and squeegees. Relevant technical innovations in the art of stencil printing for microelectronics packaging are examined as each part of the printing process is explained.
Originality/value
Stencil printing is currently the cheapest and highest throughput technique to create the mechanical and electrically conductive connections between substrates, bare die, packaged chips and discrete components. As a result, this process is used extensively in the electronic packaging industry and therefore such a review paper should be of interest to a large selection of the electronics interconnect and assembly community.
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Amar Kanekar, Janea Snyder and Bennie Prince
Recent decades have shown a great increase in online and blended learning and teaching practices in higher education. The purpose of this book chapter is to explore and assess the…
Abstract
Recent decades have shown a great increase in online and blended learning and teaching practices in higher education. The purpose of this book chapter is to explore and assess the existing literature on best practices in online and hybrid teaching and learning in the field of health education/promotion. Additionally, emerging practices Post-COVID-19 related to online and hybrid teaching as applicable to the field of health education/promotion were also explored.
In order to collect the materials for the study, a Boolean search of CINAHL, MEDLINE, and ERIC, Education Research Complete databases was carried out using the terms and headings such as “online teaching,” “hybrid teaching,” “health education,” “health promotion,” and “public health” for the time period 2010–2020. The criteria for inclusion of the studies were: (1) publication in English language, (2) full-text peer-reviewed publications between 2010 and 2020, and (3) location of studies anywhere in the world Exclusion criteria were publications in languages other than English and studies published prior to 2010. Using the key terms “online teaching” and “public health” yielded 10 results and “online teaching” and “health education” yielded 19 results. This review highlighted the scant published literature (as gauged by studies published in the last decade) on efficacy and application of online and hybrid teaching and learning in the field of health education/promotion.
We encourage health education professionals to conduct experimental and quasi-experimental studies for assessing efficacy of online and hybrid teaching and learning particularly using evidence-based frameworks such as Quality Matters (QM) or Online Learning Consortium (OLC) quality scorecard as mentioned earlier.
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G.J. Jackson, M.W. Hendriksen, R.W. Kay, M. Desmulliez, R.K. Durairaj and N.N. Ekere
The study investigates the sub process behaviour in stencil printing of type‐6 and type‐7 particle size distribution (PSD) Pb‐free solder pastes to assess their printing limits.
Abstract
Purpose
The study investigates the sub process behaviour in stencil printing of type‐6 and type‐7 particle size distribution (PSD) Pb‐free solder pastes to assess their printing limits.
Design/methodology/approach
Two solder pastes were used in a design of experiments approach to find optimal printing parameters
Findings
Solder paste printing has been achieved to ultimately produce 30 μm deposits at 60 μm pitch for full area array patterns using a type‐7 Pb‐free solder paste. For a type‐6 PSD solder paste, full area array printing was limited to 50 μm deposits at 110 μm pitch. However, for peripheral printing patterns, 50 μm deposits at 90 μm pitch were obtained. The disparities in the behaviour of the two paste types at different geometries can be attributed to differences in the sub‐processes of the stencil printing. The paste release of the type‐6 paste from the stencil apertures at fine pitch was superior to the type‐7 paste, which may be attributed to the finer particle paste producing an increased drag force along the stencil aperture walls. However, the type‐7 paste was able to fill the smallest aperture openings, ultimately to 30 μm, thus producing full array printing patterns at uniquely small pitches.
Practical implications
This advancement in the stencil printing process has been made possible by refinements to both solder paste design and stencil manufacturing technology. Adjustments in the solder paste rheology have enabled successful printing at ultra fine pitch geometries. This, together with selecting appropriate printing parameters such as printing speed, pressure, print gap and separation speed, allows a practical printing process window. Moreover, advancements in stencil fabrication methods have produced “state‐of‐the‐art” stencils exhibiting very precisely defined aperture shapes, with smooth walls at very fine pitch, thus allowing for improved solder paste release at very small dimensions.
Originality/value
The results can be used to present a low cost solution for Pb‐free flip chip wafer bumping. Furthermore, the results indicate that type‐6 and type‐7 solder pastes should be applied to/selected for specific application geometries.
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Yacheng Wang, Peibo Li, Yuegang Liu, Yize Sun and Liuyuan Su
In 3D additive screen printing with constant snap-off, the inhomogeneous screen counterforce will influence the printing force and reduce the printing quality. The purpose of this…
Abstract
Purpose
In 3D additive screen printing with constant snap-off, the inhomogeneous screen counterforce will influence the printing force and reduce the printing quality. The purpose of this paper is to study the relationship between scraper position, snap-off and screen counterforce and develop a variable snap-off curve for 3D additive screen printing to improve the printing quality.
Design/methodology/approach
An experiment was carried out; genetic algorithm (GA) optimization theoretical model, backpropagation neural network regression model and least square support vector machine regression model were established to study the relationship between scraper position, snap-off and screen counterforce. The absolute errors of counterforce of three models with the experiment results were less than 1.5 N, which was tolerated and the three models were considered valid. The comparison results showed that GA optimization theoretical model performed best.
Findings
The results suggest that GA optimization theoretical model performed best to represent the relationship, and it was used to develop a variable snap-off curve. With the variable snap-off curve in 3D additive screen printing, the inhomogeneous screen counterforce was weakened and the printing quality was improved.
Originality/value
In printing production, the variable snap-off curve in 3D additive screen printing helps improve the printing quality; this study is of prime importance to the 3D additive screen printing.