LONDON " Belgian interdisciplinary research group IMEC is extending its work in the bioelectronics area with a project that has already developed a miniature 1 cm3 3-dimensional stacked system-in-a-cube (SiC) for wireless communications systems.
IMEC says the low-power 3D SiC, which comprises a radio and digital signal processor, has application in a variety of wireless products, ranging from monitors for human-body information and other sensors to wireless multi-hop beacons.
The device is already being incorporated into a wearable, wireless electroencephalogram (EEG) for monitoring brain-wave activity developed by IMEC and the University Hospital Leuven, Belgium. Prototypes are already being tested and a commercial device should be available by October this year.
Using the cube patients can wear a comfortable device and maintain maximum mobility during the electroencephalogram, eliminating the hospital stay traditionally necessary for this procedure. The SiC was developed as part of IMEC's Human++ program, which is targeting similar SiCs as sensor nodes constituting a body area network. The program combines experience and expertise in wireless communications, packaging techniques, energy scavenging technologies and low-power design techniques.
The 3D-stack prototype integrates a commercial low-power 8Mips microcontroller and a 2.4 GHz wireless transceiver, crystals and other passive devices, as well as a custom-designed matched dipole antenna.
The level of integration necessary was achieved through Z-axis three-dimensional stacking of separate layers with different functionality. In this way each layer connects to its neighboring layers through a dual row of fine pitch solder balls.
The stacking technique allows any kind of module build-up; each layer can have dedicated functionality such as computing, wireless communication, sensing or power scavenging. The bottom layer has a BGA footprint, allowing standard techniques for module mounting.
The procedure allows integrating a specific sensor into a single layer, leading to application-specific cubic sensor modules.
IMEC says it is planning to reduce the size even further, and to integrate its low-power processing, wireless and power-scavenging technology into the cube.
Adding an extra stack layer with solar cells and energy-storage circuitry will offer a complete standalone solution.