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The purpose of this paper is to present results from the EC funded project SHIFT (Smart High Integration Flex Technologies) on the embedding in and the assembly on flex substrates of ultrathin chips.

Methods to embed chips in flex include flip‐chip assembly and subsequent lamination, or the construction of a separate ultra‐thin chip package (UTCP) using spin‐on polyimides and thin‐film metallisation technology. Thinning and separation of the chips is done using a “dicing‐by‐thinning” method.

The feasibility of both chip embedding methods has been demonstrated, as well as that of the chip thinning method. Lamination of four layers of flex with ultrathin chips could be achieved without chip breakage. The UTCP technology results in a 60 μm package where also the 20 μm thick chip is bendable.

Further development work includes reliability testing, embedding of the UTCP in conventional flex, and construction of functional demonstrators using the developed technologies.

Thinning down silicon chips to thicknesses of 25 μm and lower is an innovative technology, as well as assembly and embedding of these chips in flexible substrates.

The purpose of this paper is to present an update on the progress of the design and reliability of stretchable interconnections for electronic circuits.

Finite element modelling (FEM) is used to analyse the physical behaviour of stretchable interconnects under different loading conditions. The fatigue life of a copper interconnect embedded into a silicone matrix has been evaluated using the Coffin‐Manson relation and FEM.

The mechanical properties of the substrate and the design of the metal interconnection play an important role on the fatigue lifetime of circuit. In the case of copper embedded into a PDMS Sylgard 186, more than 2,500 tensile cycles have been observed for a periodic deformation of 10 per cent.

Reliability results are limited and need further work to create a more accurate empirical model to estimate the lifetime of stretchable interconnections.

The combined use of FEM and experimental analysis enable a more reliable design of the stretchable metal interconnections. The proposed horseshoe design offers the benefit of reduced permanent damage during elongation.

The purpose of this paper is to investigate the various factors that influence the dissolution of copper in molten solder, paying particular attention to important parameters: temperature, solder composition and flow rate.

To determine the dissolution rate of copper in lead‐free solders, a simple and automated technique is developed. This methodology provides repeatable measurements that allow the various experimental parameters to be isolated. Factors that greatly affect the dissolution rate of copper, such as soldering temperature, flow rate and solder composition, are taken into account. Particular attention is paid to the flow rate of the molten solder. In fact, different alloys at the same temperature can have considerably different flow rates, owing to their different viscosities at that temperature. The dissolution rates of copper in seven lead‐free alloys and the Sn‐Pb alloy are compared at 255, 275 and 300°C.

It is observed that generally the samples with a thicker intermetallic layer are those that exhibit a longer dissolution time.

The transition from tin‐lead to lead‐free increases the tendency for copper dissolution in molten solders, clearly representing a serious risk to circuit reliability. This paper presents the many advantages of a method for comparing the dissolution rate of copper with different solder alloys.

The purpose of this paper is to investigate the effect of carbon nanotube (CNT) addition on microstructure, interfacial intermetallic compound (IMC) layer and micromechanical properties of Sn-3.0Ag-0.5Cu (SAC305)/CNT/Cu solder joint under blast wave condition. This work is an extension from the previous study of microstructural evolution and hardness properties of Sn-Ag-Cu (SAC) solder under blast wave condition.

SAC/CNT solder pastes were manufactured by mixing of SAC solder powder, fluxes and CNT with 0.02 and 0.04 by weight percentage (Wt.%) separately. This solder paste then printed on the printed circuit board (PCB) with the copper surface finish. Printed samples underwent reflow soldering to form the solder joint. Soldered samples then exposed to the open field air blast test with different weight charges of explosives. Microstructure, interfacial IMC layer and micromechanical behavior of SAC/CNT solder joints after blast test were observed and analyzed via optical microscope, field emission scanning microscope and nanoindentation.

Exposure to the blast wave induced the microstructure instability of SAC305/Cu and SAC/CNT/Cu solder joint. Interfacial IMC layer thickness and hardness properties increases with increase in explosive weight. The existence of CNT in the SAC305 solder system is increasing the resistance of solder joint to the blast wave.

Response of micromechanical properties of SAC305/CNT/Cu solder joint has been identified and provided a fundamental understanding of reliability solder joint, especially in extreme conditions such as for military applications.

In the past 15 years stretchable electronic circuits have emerged as a new technology in the domain of assembly, interconnections and sensor circuits and assembly technologies. In the meantime a wide variety of processes with the use of many different materials have been explored in this new field. The purpose of the current contribution is for the authors to present an approach for stretchable circuits which is inspired by conventional rigid and flexible printed circuit board (PCB) technology. Two variants of this technology are presented: stretchable circuit board (SCB) and stretchable mould interconnect (SMI).

Similarly as in PCB 17 or 35 μm thick sheets of electrodeposited or rolled‐annealed Cu are structured to form the conductive tracks, and off‐the‐shelf, standard packaged, rigid components are assembled on the Cu contact pads using lead‐free solder materials and reflow processes. Stretchability is obtained by shaping the Cu tracks not as straight lines, like in normal PCB design, but as horseshoe shaped meanders. Instead of rigid or flexible board materials, elastic materials, predominantly PDMS (polydimethylsiloxane), are used to embed the conductors and the components, thus serving as circuit carrier. The authors include some mechanical modeling and design considerations, aimed at the optimization of the build‐up and combination of elastic, flexible and rigid materials towards minimal stress and maximum mechanical reliability in the structures. Furthermore, details on the two production processes are given, reliability findings are summarised, and a number of functional demonstrators, realized with the technologies, are described.

Key conclusions of the work are that: supporting the metal meanders with a flexible carrier prior to embedding in an elastic substrate substantially increases the reliability under mechanical stress (cyclic uniaxial stretching) of the stretchable interconnect and the transition areas between rigid components and stretchable interconnects are the zones which are most sensitive to failure under mechanical stress. Careful design and technology implementation is necessary, providing a gradual transition from rigid to flexible to stretchable parts of the circuit.

Technologies for stretchable circuits, with the same level of similarity to standard PCB manufacturing and assembly, and thus with the same high potential for transfer to an industrial environment and for mass production, have not been shown before.

The purpose of this paper is to investigate the benefit of pre-emptive disruption management measures for assembly systems towards the target dimension adherence to delivery times.

The research was conducted by creating simulation models for typical assembly systems and measuring its varying throughput times due to changes in their disruption profiles. Due to the variability of assembly systems, key influence factors were investigated and used as a foundation for the simulation setup. Additionally, a disruption profile for each simulated process was developed, using the established disruption categories material, information and capacity. The categories are described by statistical distributions, defining the interval between the disruptions and the disruption duration. By a statistical experiment plan, the effect of a reduced disruption potential onto the throughput time was investigated.

Pre-emptive disruption management is beneficial, but its benefit depends on the operated assembly system and its organisation form, such as line or group assembly. Measures have on average a higher beneficial impact on group assemblies than on line assemblies. Furthermore, it was proven that the benefit, in form of better adherence to delivery times, per reduced disruption potential has a declining character and approximates a distinct maximum.

Characterising the benefit of pre-emptive disruption management measures enables managers to use this concept in their daily production to minimise overall costs. Despite the hardly predictable influence of pre-emptive disruption measures, these research results can be implemented into a heuristic for efficiently choosing these measures.

The purpose of this paper is to show that cafeteria style grading actually provides a course structure which encourages students to go beyond expectations.

Three instructors offered a total of 13 sections of a general education science class called “Fundamentals of Technology” from January 2012 to December 2013 using a cafeteria-style grading method. This means students get to choose to do those assignments, quizzes or tests that appeal to their own learning interests or styles and do not need to complete all the assignments to get an A grade. Rather, they complete those assignments desired in order to earn the applicable points. This paper researches the combined results of over 400 students to assess the success of cafeteria style grading.

These instructors found that half the students overall obtain an A grade and 9 percent of all students actually go above and beyond the requirements of an A grade by at least 5 percent. Actually, about 4 percent of students complete more than is required by an additional 10 percent or more.

Cafeteria style grading is a little researched methodology for student assessment. The research shows that cafeteria style grading actually provides a course structure which encourages students to go beyond expectations.