Ultra-thin chip package (UTCP) and elastic circuit technologies for compact or conformable sensor and electronics assemblies

This contribution provides an overview of CMST's technologies on flexible ultrathin chip packaging and elastic electronic and sensor circuit technologies and applications

Flexible and stretchable electronics

Conventionally electronics circuits are produced by assembly of packaged components on flat, rigid printed circuit boards. However there is a growing demand for 2.5 dimensional (2.5D free form surfaces) or even full 3D electronics. Applications for such circuits are found in a vast range of fields: such circuits are desirable for comfort and ergonomic reasons (e.g. in wearable or implantable circuits), to respond to design and aesthetics considerations (e.g. 2.5D or 3D light sources), for ecological reasons (more efficient materials usage, less CO2 emissions in automotive applications) etc. In this contribution we will present two technologies, under development at our laboratory, which open the way to industrial production of randomly deformable circuits. These technologies are : • The ultra-thin chip package (UTCP) technology, by which bare Si (or other anorganic semiconductor based) chips are thinned down to a thickness of 20-30µm, embedded in a stack of spin-on polyimide layers, and provided with a fan-out metallization, resulting in an extremely miniaturized, lightweight and flexible chip package with a total thickness below 100µm • A number of technologies for dynamically stretchable (i.e. elastic) circuits, which are based on the interconnection of individual components or component islands with meander shaped thin-film or Printed Circuit Board (PCB) based metal wirings and embedding in elastic polymers like PDMS (silicone rubbers) or PU (polyurethanes). Process flow details, reliability data and applications for these technologies will be presented

Flexible and stretchable circuit technologies for space applications

Flexible and stretchable circuit technologies offer reduced volume and weight, increased electrical performance, larger design freedom and improved interconnect reliability. All of these advantages are appealing for space applications. In this paper, two example technologies, the ultra-thin chip package (UTCP) and stretchable moulded interconnect (SMI), are described. The UTCP technology results in a 60 µm thick chip package, including the embedding of a 20 µm thick chip, laser or protolithic via definition to the chip contacts and application of fan out metallization. Imec’s stretchable interconnect technology is inspired by conventional rigid and flexible printed circuit board (PCB) technology. Stretchable interconnects are realized by copper meanders supported by a flexible material e.g. polyimide. Elastic materials, predominantly silicone rubbers, are used to embed the conductors and the components, thus serving as circuit carrier. The possible advantages of these technologies with respect to space applications are discussed

Hurdles in investigating UVB damage in the putative ancient asexual Darwinula stevensoni (Ostracoda, Crustacea)

Ostracoda or mussel-shrimps are small, bivalved Crustacea. Because of their excellent fossil record and their broad variety of reproductive modes, ostracods are of great interest as a model group in ecological and evolutionary research. Here, we investigated damage and repair of one of the most important biological mutagens, namely UVB radiation in the putative ancient asexual ostracod Darwinula stevensoni from Belgium. We applied three different methods: the Polymerase Inhibition (PI) assay, Enzyme-Linked Immuno Sorbent Assay (ELISA) and dot blot. All three techniques were unsuccessful in quantifying UVB damage in D. stevensoni. Previous experiments have revealed that the valves of D. stevensoni provide an average UVB protection of approximate 60%. Thus, UVB damage could be too little to make quantitative experiments work. Additional variation between individual ostracods due to season and age most likely contributed further to the failure of the three used experimental approaches. In a second experiment, we investigated the influence of temperature on survival of D. stevensoni during UVB exposure. The estimated lethal UVB dose at 4°C was with 50 kJ/m2 significantly lower than at room temperature with 130 kJ/m2. This could either indicate adaptation to low temperatures and/or the presence of metabolic processes against UVB damage in D. stevensoni. These results could also explain why the estimated lethal UVB dose of D. stevensoni is similar to that of other non-marine ostracods where valves provide around 80% protection, although the valves of D. stevensoni provide less protection. If such metabolic processes can repair UVB damage fast, they might be an alternative explanation why we could not quantify UVB damage in D. stevensoni

Highly efficient impulse-radio ultra-wideband cavity-backed slot antenna in stacked air-filled substrate integrated waveguide technology

An impulse-radio ultra-wideband (IR-UWB) cavity-backed slot antenna covering the [5.9803; 6.9989] GHz frequency band of the IEEE 802.15.4a-2011 standard is designed and implemented in an air-filled substrate integrated waveguide (AFSIW) technology for localization applications with an accuracy of at least 3 cm. By relying on both frequency and time-domain optimization, the antenna achieves excellent IR-UWB characteristics. In free-space conditions, an impedance bandwidth of 1.92 GHz (or 29.4%), a total efficiency higher than 89%, a front-to-back ratio of at least 12.1 dB, and a gain higher than 6.3 dBi are measured in the frequency domain. Furthermore, a system fidelity factor larger than 98% and a relative group delay smaller than 100 ps are measured in the time domain within the 3 dB beamwidth of the antenna. As a result, the measured time-of-arrival of a transmitted Gaussian pulse, for different angles of arrival, exhibits variations smaller than 100 ps, corresponding to a maximum distance estimation error of 3 cm. Additionally, the antenna is validated in a real-life worst-case deployment scenario, showing that its characteristics remain stable in a large variety of deployment scenarios. Finally, the difference in frequency-and time-domain performance is studied between the antenna implemented in AFSIW and in dielectric filled substrate integrated waveguide (DFSIW) technology. We conclude that DFSIW technology is less suitable for the envisaged precision IR-UWB localization application

Intermediary metabolism

Caenorhabditis elegans has orthologs for most of the key enzymes involved in eukaryotic intermediary metabolism, suggesting that the major metabolic pathways are probably present in this species. We discuss how metabolic patterns and activity change as the worm traverses development and ages, or responds to unfavorable external factors, such as temperature extremes or shortages in food or oxygen. Dauer diapause is marked by an enhanced resistance to oxidative stress and a shift toward microaerobic and anaplerotic metabolic pathways and hypometabolism, as indicated by the increased importance of the malate dismutation and glyoxylate pathways and the repression of citric acid cycle activity. These alterations promote prolonged survival of the dauer larva; some of these changes also accompany the extended lifespan of insulin/IGF-1 and several mitochondrial mutants. We also present a brief overview of the nutritional requirements, energy storage and waste products generated by C. elegans

High yield fabrication process for 3D-stacked ultra-thin chip packages using photo-definable polyimide and symmetry in packages

Getting output of multiple chips within the volume of a single chip is the driving force behind development of this novel 3D integration technology, which has a broad range of industrial and medical electronic applications. This goal is achieved in a two-step approach. At first thinned dies are embedded in a polyimide interposer with a fine-pitch metal fan-out resulting Ultra-Thin Chip Packages (UTCP), next these UTCPs are stacked by lamination. Step height at the chip edge of these UTCPs is the major reason of die cracking during the lamination. This paper contains an approach to solve this issue by introduction of an additional layer of interposer which makes it flat at the chip edge and thus the whole packages is named as “Flat-UTCP”. In addition to that, randomness in non-functional package positions per panel reduces the overall yield of the whole process up to certain extent. A detailed analysis on these two issues to improve the process yield is presented in this paper. 3D-stacked memory module composed of 4 EEPROM dies was processed and tested to demonstrate this new concept for enhancing the fabrication yield

Stretchable platform enabled with wireless power for smart contact lenses

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