The objective of this ongoing work is the development of a microlab on flexible tag, capable to monitor the quality of the food, during transport, storage and vending. The idea is to bring together different sensor technologies that will be integrated into a data communication environment for online food monitoring during the logistics chain.
The proposed solution is the concept of silicon chips and microcomponents assembled and integrated on top of a flexible substrate acting mainly as a passive interconnect structure.
Three technologies have been identified as necessary to get the final integration:
a) Substrate technology. This technology refers to the realisation of the flexible substrate with the metallic interconnections.
b) Assembly technology to integrate the discrete components on the flexible substrate. The conventional processes are wire bonding, flip chip, and adhesive bonding.
c) Encapsulation technology and windows opening over the gas sensitive areas.
The first flexible tag prototype integrates two different metal oxide sensor arrays with a commercial microprocessor. The dimensions are 43 mm long, 22 mm wide and about 2 mm thick and two metal levels are necessary for the interconnect. The strategy undertaken by the groups involved in this work, consists in the evaluation of different approaches, that combine diverse process sequences and materials, with the final aim of identifying the best solution.
Regarding the substrate technology, the approach realized using Pyralux copper-clad laminated composites, constructed of DuPont Kapton polyimide film with copper foil on both sides, as flexible substrate will be described in this paper. The cupper interconnections are generated by standard photolithography and wet etching and the vias definition in Kapton is performed by femtosecond laser ablation. On the other hand, the assembly technology based on the use of anisotropically conductive adhesives will be also illustrated.