Development and characterisation of ultra thin autonomous modules for ambient system applications using 3D packaging techniques

The work presented in this paper represents two strands of the work of the ambient system team at NMRC to produce ultra-miniature sensor modules [1]. These modules with an ultimate target size of < 1mm³ are needed for the implementation of future ad-hoc networks for ambient systems. Ambient systems stem from convergence of three key technologies: Ubiquitous Computing, Ubiquitous Communication and Intelligent user friendly Interfaces. On convergence, humans will be surrounded by intelligent interfaces, supported by computing and networking technology which is everywhere, embedded in everyday objects such as furniture, clothes, vehicles, and smart materials. [2] The work done for the realisation of the 1mm³ autonomous sensor module is following a technology roadmap developed by NMRC as is shown in Figure 1. The work is carried out in different phases: in the first phase a 25mm cube fabricated as 3D stackable modular PCB is being reported. [3,4] The current module is a 1cm cube, combining a microcontroller, PLD, accelerometer, light dependant resistors and coloured LED's with the aim of creating modular wireless computational unit[5]. This paper will detail the assembly, characterisation and reliability issues of this module while work done to realise a very thin multi layer flexible substrate for a 5mm cube will be presented.