Lucrezia Casulli, Dominic Michael Chalmers, Sarah Drakopoulou Dodd, Russell Matthews and Stoyan Stoyanov
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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Dinko Dinkov and Stoyan Stoyanov
The Cyprus conflict is a classical case of protracted ethnic conflict with very obvious and important international dimensions. It is one of the major unresolved inter national…
Abstract
The Cyprus conflict is a classical case of protracted ethnic conflict with very obvious and important international dimensions. It is one of the major unresolved inter national conflicts, which for decades attracts the attention of the international community. The involvement of many countries and international organizations in the Cyprus conflict demonstrates the importance and seriousness of the conflict. During the last decades the conflict has cost a lot both for the Greek Cypriots and for the Turkish Cypriots. It claimed a lot of lives and caused serious economic damages and psychological destruction. The conflict began in the 1950s, erupted violently with blood shed at the end of 1963,and culminated in 1974 with the interventions of Greece and Turkey that led to the island’s current de facto division as the Greek Cypriot South and Turkish Cypriot North. Over the past 40 years many states have came out with various initiatives and have proposed various approaches for final settlement of the conflict. It also has been addressed by dozens of UN Security Council resolutions but all these have proved to be futile so far.
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Stoyan Stoyanov, Tim Tilford, Farid Amalou, Scott Cargill, Chris Bailey and Marc Desmulliez
Nano‐imprint forming (NIF) is a manufacturing technology capable of achieving high resolution, low‐cost and high‐throughput fabrication of fine nano‐scale structures and patterns…
Abstract
Purpose
Nano‐imprint forming (NIF) is a manufacturing technology capable of achieving high resolution, low‐cost and high‐throughput fabrication of fine nano‐scale structures and patterns. The purpose of this paper is to use modelling technologies to simulate key process steps associated with the formation of patterns with sub‐micrometer dimensions and use the results to define design rules for optimal imprint forming process.
Design/methodology/approach
The effect of a number of process and pattern‐related parameters on the quality of the fabricated nano‐structures is studied using non‐linear finite element analysis. The deformation process of the formable material during the mould pressing step is modelled using contact analysis with large deformations and temperature dependent hyperelastic material behaviour. Finite element analysis with contact interfaces between the mould and the formable material is utilised to study the formation of mechanical, thermal and friction stresses in the pattern.
Findings
The imprint pressure, temperature and the aspect ratio of grooves which define the pattern have significant effect on the quality of the formed structures. The optimal imprint pressure for the studied PMMA is identified. It is found that the degree of the mould pattern fulfilment as function of the imprint pressure is non‐linear. Critical values for thermal mismatch difference in the CTE between the mould and the substrate causing thermally induced stresses during cooling stage are evaluated. Regions of high stresses in the pattern are also identified.
Originality/value
Design rules for minimising the risk of defects such as cracks and shape imperfections commonly observed in NIF‐fabricated nano‐structures are presented. The modelling approach can be used to provide insights into the optimal imprint process control. This can help to establish further the technology as a viable route for fabrication of nano‐scale structures and patterns.
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Andrew Richardson, Chris Bailey, Jean Marc Yanou, Norbert Dumas, Dongsheng Liu, Stoyan Stoyanov and Nadia Strusevich
To present key challenges associated with the evolution of system‐in‐package technologies and present technical work in reliability modeling and embedded test that contributes to…
Abstract
Purpose
To present key challenges associated with the evolution of system‐in‐package technologies and present technical work in reliability modeling and embedded test that contributes to these challenges.
Design/methodology/approach
Key challenges have been identified from the electronics and integrated MEMS industrial sectors. Solutions to optimising the reliability of a typical assembly process and reducing the cost of production test have been studied through simulation and modelling studies based on technology data released by NXP and in collaboration with EDA tool vendors Coventor and Flomerics.
Findings
Characterised models that deliver special and material dependent reliability data that can be used to optimize robustness of SiP assemblies together with results that indicate relative contributions of various structural variables. An initial analytical model for solder ball reliability and a solution for embedding a low cost test for a capacitive RF‐MEMS switch identified as an SiP component presenting a key test challenge.
Research limitations/implications
Results will contribute to the further development of NXP wafer level system‐in‐package technology. Limitations are that feedback on the implementation of recommendations and the physical characterisation of the embedded test solution.
Originality/value
Both the methodology and associated studies on the structural reliability of an industrial SiP technology are unique. The analytical model for solder ball life is new as is the embedded test solution for the RF‐MEMS switch.