R. Hahn

Batteries and power supplies for wearable and ubiquitous computing

The paper discusses the energy storage requirements of wearable computer technology and identifies research topics for novel battery technologies. Three categories of devices with basically different battery requirements were defined. They comprise the wearable computer main unit, small devices which are distributed around the human body and active tags which enable situated and ubiquitous computing. There is a demand for small, high energy density rechargeable batteries which enable a flexible design and for very low cost thin primary batteries for smart label active lags. Prototypes of 120 /spl mu/m thick AgO-Zn batteries have been fabricated by a screen printing process. They can be directly integrated into plastic cards, smart labels and hybrid circuits.

High power multichip modules employing the planar embedding technique and microchannel water heat sinks

This paper describes a novel packaging technology for high power multi chip modules (MCMs). The work covers three areas: The fabrication of a multichip module which provides access to the die backside for heat removal, the development of high performance microchannel heat sinks with a CTE matched to the MCM-substrate as well as a low thermal resistivity assembling technology of the two components. The MCM is fabricated by means of the planar embedding technology. By planarizing the module backside a low thermal resistance between heat sink and dice can be accomplished simultaneously for all embedded components. While offering the same high interconnection density and the high speed performance benefit of flip chip and providing high reliability and very small size of the overall package, this alternative technology promises to eliminate crucial problems associated with backside cooling of flip chip devices.

Thermal management of portable micro fuel cell stacks

A prototype of a CamCorder with a PEM (polymer electrolyte membranes) fuel cell system consisting of a stack of fifteen bipolar plates was developed to deliver a maximum output power of 9 W. This system replaces the Li-ion battery pack normally used as an energy source for the camera. A thermal model for the fuel cell stack was developed and validated by thermal measurements. The model was used to study different cooling methods and the integration of fuel cells into portable electronic products. A new method of stack cooling was developed in which most of the heat is transferred by means of thermal conduction via the bipolar plates and then distributed to external cooling devices. In this way, system miniaturization was achieved and weight and costs were kept to a minimum by reducing the number of ancillary components.

Thermal Constraints of PEM Micro Fuel Cells for Portable Electronics

Despite increasingly efficient components and low-power technologies, the energy demands of portable electronic products will rise dramatically in the future due to their growing functionality. As improvements in battery technology have so far been limited to energy density increases of only a few percent per annum, over the past few years many R&D activities have concentrated on alternative forms of portable power supply. One of the most promising candidates is micro fuel cells (FCs) based on polymer electrolyte membranes (PEMs) [1–3]. But there are several of challenges concerning fuel cells as a battery replacement:

Foil Type Micro PEM Fuel Cell with Self-Breathing Cathode Side

Despite increasingly efficient components and low power technologies, the energy demands of portable electronic products such as next-generation mobile phones, wearable computers, autonomous sensors and microsystems will rise dramatically in the future due to their growing functionality. As improvements in battery technology have so far been limited to energy density increases of only a few percent per annum, over the past few years many R&D activities have concentrated on alternative forms of portable power supply. One of the most promising candidates is micro fuel cells (FCs) based on polymer electrolyte membranes (PEMs). They could be used as energy sources for applications in devices such as hearing aids, chip cards, wireless sensor networks and other small portable devices, thereby replacing Li-polymer batteries, button cells and zinc air batteries. Compared to batteries the environmental impact of fuel cells is much lower [1].