3D Integration of ultra-thin functional devices inside standard multilayer flex laminates

Nowadays, more and more wearable electronic systems are being realized on flexible substrates. Main limiting factor for the mechanical flexibility of those wearable systems are typically the rigid components - especially the relatively large active components - mounted on top and bottom of the flex substrates. Integration of these active devices inside the flex multilayers will not only enable for a high degree of miniaturization but can also improve the total flexibility of the system. This paper now presents a technology for the 3D embedding of ultra-thin active components inside standard flex laminates. Active components are first thinned down to 20-25 mu m, and packaged as an Ultra-Thin Chip Pack-age (UTCP). These UTCP packages will serve as flexible interposer: all layers are so thin, that the whole package is even bendable. The limited total pack-age thickness of only 60 mu m makes them also suitable for lamination in between commercial flex panels, replacing for example the direct die integration. A fan-out metallization on the package facilitates easy testing before integration, solving the KGD issue, and can also relax the chip contact pitch, excluding the need for very precise placement and the use of expensive, fine-pitch flex substrates. The technology is successfully demonstrated for the 3D-integration of a Texas Instrument MSP430 low-power microcontroller, inside the conventional double sided flex laminate of a wireless ECG system. The microcontrollers are first thinned down and UTCP pack-aged These pack-ages are then laminated in between the large panels of the flex multilayer stack and finally connected to the different layers of the flex board by metallized through-hole interconnects. The thinning down, the UTCP pack-aging and the 3D-integration inside the commercial flex panels did not have any affect on the functionality of the TI microcontroller. Smaller SMD's were finally mounted on top and bottom of the integrated device

Analysis of TDMA scheduling by means of Egyptian fractions for real-time WSNs

Abstract In Wireless Sensor Networks (WSNs), Time Division Multiple Access (TDMA) is a well-studied subject. TDMA has, however, the reputation of being a rigid access method and many TDMA protocols have issues regarding the entering or leaving of sensors or have a predetermined upper limit on the number of nodes in the network. In this article, we present a flexible TDMA access method for passive sensors, that is, sensors that are constant bitrate sources. The presented protocol poses no bounds on the number of nodes, yet provides a stable framing that ensures proper operation, while it fosters that every sensor gets its data on time at the sink and this in a fair fashion. Even more, the latency of the transmission is deterministic and thereby enabling real-time communication. The protocol is developed, keeping in mind the practical limitations of actual hardware, limiting the memory usage and the communication overhead. The schedule that determines when a sensor can send can be encoded in a very small footprint and needs to be sent only once. As soon as the sensor has received its schedule, it can calculate for the rest of its lifetime when it is allowed to send.</p

Binary TDMA Schedule by Means of Egyptian Fractions for Real-time WSNs on TMotes

should not be bothered with configuring the network, depending on the kind of sensors that he/she is using. It should only be a matter of deploying the sensors and they should do the necessary effort to construct a network. Since most of these networks use low power devices, the energy consumption is vital. The most suited medium access method in order to waste as few energy as possible, is Time Division Multiple Access (TDMA). TDMA has however the reputation of being a rigid access method. In this paper, we present a TDMA access method for passive sensors, i.e. sensors are constant bitrate sources. The presented protocol does not only take into account the energy, but it also ensures that every sensor gets its data on time at the sink and this in a fair fashion. Even more, the latency of the transmission is deterministic. We could say that real-time communication is possible. The protocol is developed keeping in mind the practical limitations of actual hardware by limiting the memory usage and the communication overhead. The schedule that determines which sensor can send when, which can be encoded in a very small footprint, and needs to be sent only once. To prove our statement, we implemented our scheduling protocol on TMotes. I