Arduino Goes Hybrid, Flexible
Republished guest column from EETimes.
Flexible hybrid electronics are poised to enable the Maker movement with flexible Arduino microcontroller boards.
A new generation of products is emerging based on low cost printed electronics with embedded silicon ICs and sensors. By eliminating the need for rigid enclosures, flexible hybrid electronics (FHE) will reduce system footprints with devices that conform to most 3D surfaces so they can be mounted in difficult-to-access spaces.
FHE attaches bare die to a flexible substrate without the need, cost and size penalty of a standard package. Systems become bendable, using wafer and die thinning techniques already in volume production for 2.5D and 3D chip stacks.
Novel die-attach methods designed for use in conformal and flexible applications are now in development and showing promise. Conventional assembly methods, such as wire bonding and the many variants of solder bump attach, are well suited for rigid applications but are challenging to use in a flexible substrate system.
Compare for example at an open source and wildly popular Arduino Mini (inset at half size in the picture below) to its flexible, hybrid equivalent. The conventional 30x18mm double-sided board can be shrunk with FHE to a flexible 26x16mm, that uses single-side component placement.
An FHE version of an Arduino Mini with the original inset at a reduced size (Image: NextFlex)
The FHE layout above has not yet been optimized for printing and component placement which would further shrink its size. In this example, the same passive components are used as in the rigid board, and the difference in total size and height is significant. Future versions will have at least some of the passives printed directly onto the substrate.
Another example is a skin patch developed at the University of San Diego to detect alcohol levels in the wearer by measuring biomarkers in sweat. It initially uses tattoo-like printed sensors placed on the skin along with a flex board and packaged components. The FHE variant will provide the sensor interface board on the same substrate as the sensor.
The most commonly used substrate in FHE systems is polyethylene terephthalate (PET). It has a maximum process temperature of 140°C, below the requirements for typical board assembly and packaging processes. Although FHE also uses polyimide (PI) substrates, this material comes at a significant price premium compared to PET.
Low-cost, flexible and easy-to-deploy sensor platforms like these can bolster the growing Maker movement benefitting entrepreneurs and industrial giants alike. In this way FHE can enable the much hyped but as yet minimally realized growth in IoT sensing products.