Parametrical study of miniature generators for large motion applications

Designing a generator for large amplitude motion has lead to an energy-consistent model that also considers the finite dimensions of the device. Using SPICE software we have studied the influence of several design parameters on the output of the generator, including the limited motion of the seismic mass imposed by small system dimensions. Three different types of load circuits are presented, as well as their optimization towards output voltage and power

Power extraction from ambient vibration

Autonomous devices such as sensors for personal area networks need a long battery lifetime in a small volume. The battery size can be reduced by incorporating micro-power generators based on ambient energy. This paper describes a new approach to the conversion of mechanical to electrical energy, based on charge transportation between two parallel capacitors. The polarization of the device is handled by an electret. A largesignal model was developed, allowing simulations of the behavior of any circuit based on this generator for any mechanical input signal. A small-signal model was derived in order to quantify the output power as a function of the design parameters. A layout was made based on a standard SOI-technology, available in a MPW. With this layout it is possible to generate 100 mW at 1200 Hz

A new power MEMS component with variable capacitance

Autonomous devices such as wireless sensors and sensor networks need a long battery lifetime in a small volume. Incorporating micro-power generators based on ambient energy increases the lifetime of these systems while reducing the volume. This paper describes a new approach to the conversion of mechanical energy, available in vibrations, to electrical energy. The conversion principle is based on charge transportation between two parallel capacitors. An electret is used to polarize the device. A large-signal model was developed, allowing simulations of the behavior of the generator. A small-signal model was then derived in order to quantify the output power as a function of the design parameters. These models show the possibility of generating up to 40 muW with a device of 10 mm 2. A layout was made based on a standard SOI-technology, available in an MPW. With this design a power of 1 muW at 1020 Hz is expected

Ultra-Thin Chip Package (UTCP) and stretchable circuit technologies for wearable ECG system

A comfortable, wearable wireless ECG monitoring system is proposed. The device is realized using the combination of two proprietary advanced technologies for electronic packaging and interconnection : the UTCP (Ultra-Thin Chip Package) technology and the SMI (Stretchable Mould Interconnect) technology for elastic and stretchable circuits. Introduction of these technologies results in small fully functional devices, exhibiting a significant increase in user comfort compared to devices fabricated with more conventional packaging and interconnection technologies

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

Development of a thin-film stretchable electrical interconnection technology for biocompatible applications

Stretchable electronics technologies have gained a lot of interest for reasons such as user comfort and reliability. Key aspect in these technologies is the fabrication of stretchable electrical interconnections. These are realized by patterning an intrinsic, non-stretchable gold film into a sequence of horseshoe shapes, acting as "2D" springs when embedded into PDMS. Polyimide is used as a supporting material, successfully enhancing reliability during mechanical loading. This was illustrated by application of various cyclic uni-axial strains to test structures which were fabricated in this technology. A lifetime over 130'000 and 500'000 cycles has been shown at strains of respectively 20% and 10%

Low power wireless sensor network for structural health monitoring of buildings using MEMS strain sensors and accelerometers

Within the MEMSCON project, a wireless sensor network was developed for structural health monitoring of buildings to assess earthquake damage. The sensor modules use custom-developed capacitive MEMS strain and 3D acceleration sensors and a low power readout application-specific integrated circuit (ASIC). A low power network architecture was implemented on top of an 802.15.4 media access control (MAC) layer in the 900MHz band. A custom patch antenna was designed in this frequency for optimal integration into the sensor modules. The strain sensor modules measure periodically or on-demand from the base station and obtain a battery lifetime of 12 years. The accelerometer modules record during an earthquake event, which is detected using a combination of the local acceleration data and remote triggering from the base station, based on the acceleration data from multiple sensors across the building. They obtain a battery lifetime of 2 years. The MEMS strain sensor and its readout ASIC were packaged in a custom package suitable for mounting onto a reinforcing bar inside the concrete and without constraining the moving parts of the MEMS strain sensor. The wireless modules, including battery and antenna, were packaged in a robust housing compatible with mounting in a building and accessible for maintenance such as battery replacement

Adhesion test for UTCP structure in humid environment

Ultra-Thin Chip Packaging (UTCP) technology enables the integration of off-the-shelf integrated circuits into thin substrates such as different kinds of circuit boards. This technology has been created at CMST during many years of intensive study. In this technology the thinned chip is embedded into polyimide and a copper fan-out is created to form the connections between the chip and the circuit board. This technology is compatible with standard circuit board manufacturing technology, which makes it an attractive solution to create miniaturized packages for electronics. In this paper the reliability of UTCP structure was studied using adhesion peel testing. The different solutions for constructing the material layers inside a UTCP were compared for their adhesion. Special test structures were manufactured for testing. The tested material layers consisted of polyimide, benzocyclobutene (BCB) and adhesion promoter for BCB. Altogether four different constructions were tested and the peel testing was done to half of the samples right after manufacturing and to the other half after exposure in 85/85 –environment for 500h. The results show difference in adhesion after exposure to humidity. Test structures with BCB suffer from loss of adhesion in PI – BCB interface after exposure to moisture. This result addresses that the structure is more reliable when the amount of different materials and interfaces is decreased

Development and washing reliability testing of a stretchable circuit on knit fabric

The smart textiles and wearable technology markets are expanding tirelessly, looking for efficient solutions to create long-lasting products. The research towards novel integration methods and increasing reliability of wearables and electronic textiles (e-textiles) is expanding. One obstacle to be tackled is the washability and the endurance to mechanical stresses in the washing machine. In this article, different layering of thermoplastic polyurethane (TPU) films and knit fabrics are used to integrate three different designs of stretchable copper-based meander tracks with printed circuit boards. The various combinations are washed according to the ISO 6330-2012 standard to analyze their endurance. Results suggest that one meander design withstands more washing cycles and indicate that the well-selected layer compositions increase the reliability. Higher stretchability together with greater durability is accomplished by adding an extra meander-shaped TPU film layer