Flexible printed conformed electronics. Domestic competencies and electronic components
The paper presents the result of the development and manufacture of electronic components created with the use of the flexible printed electronics technology, ultrafine thinning of chip crystals of active elements and 2D microassembly operations on a thin flexible medium for a unified touch-information platform of the Internet of things.
Flexible printed electronics and photonics are at the forefront of investments in a new, science-driven innovative ecosystem that harmoniously combines professional and social welfare of the personalized medium of human life activities. Within the frame of these tasks the integrating function belongs to the global information and communication system "Internet" in its diverse professional applications (Internet of things, Internet of people, industrial Internet), including the task to integrate the actual and virtual worlds. Components of the flexible printed conformed electronics are conformally, spatially/|geometrically and functionally integrated into the distributed touch-controlled and information and communication media thereby providing for a high design adaptability of engineering solutions.
high productivity by the area and printing speed on various substrates (wallpaper, clothes, paper, polymers, etc.);
flexibility and three-dimensionality of substrates;
wide range of the main consumables (metallic, dielectric, magnetic, optical and luminescent compositions);
achievement of a sufficiently high spatial resolution at InkJet process (to 1 μ) with a possibility to reject lithographic processes.
Along with the printing technologies the flexible printed electronics and photonics includes 2D and 3D processes of the precision assembly and use of thinned chips so as to preserve flexibility and conformance of the construction.
A Digital Factory, meaning a cluster of flexible printed electronics and photonics (Fig.1) developed on the basis of the functional modules (Fig.2) that have been integrated in the automated processing line, was earlier presented in our papers [1, 2] and incorporates a techno-chemical processing module, Ink-Jet modules backed with the integral thermal and local laser processing, a 3D-interconnected laser surface modification module (3D-MID), modules of super-precision 2D and 3D assembly characterized by the positioning accuracy to 0.5 μ, a module of automatic mechanical assembly (delta-robot) of dissimilar micro-components, conveyers and robotic loaders and the automated system that controls modules and product movement processes along the line. The cluster has its own local dedusting and product removal system. The modules function due to standard software editable to perform various processing tasks depending on the process parameters and the own software that ensures the system control of the cluster. The articles are designed within the frame of modified software applications.
The peculiar features of the new production and technological niche are as follows:
wide application in manufacturing articles made with the use of precision, additive, InkJet, particle and in-print technologies;
accomplishment of the processes on 2D and 3D substrates of various physical and chemical nature;
development of convergence technologies based on organic-inorganic and bio-inorganic hybridization.
Totality of the earlier indicated design and processing solutions defines efficient ways for the industry-wise orientation of the market aimed at development of the new generation products for the socially oriented businesses and technologies, including medical, food and pharmaceutical industries, agriculture and biotechnologies .
Examples of microengineering products based on flexible printed electronic and photonics are much needed by the socially important branches of the economy:
microanalytical systems of the laboratory-on-chip type applicable for the high-sensitive biomedical express-control, food product safety determination and biosphere monitoring;
ultrasmall information and communication modules easily integrated in food product packing in order to collect and transfer information on the conditions of storage, transportation and sale;
multifunctional sensor-actuating elements incorporated in clothes and placed on a human body for the needs of biomonitoring and management of the body condition;
low-budget distributed sensor fields to monitor agricultural parameters in the individual plots and in the industrial sectors of agriculture;
sensor-actuating ultrasmall modules for bionic robotic complexes and the system for replacing functional elements in a human body.
Saint Petersburg Electrotechnical University "LETI" (SPEU "LETI") has developed prototypes of the modules that are basic for the formation of the Internet of things, namely – a flexible super-thin intelligent sensory platform.
Assembly of modules with the use of the hybrid printed electronics technology and achievement of such important parameter as the flexibility of a device necessitates the technology for the creation of ultrathin integrated chips. SPEU "LETI" developed the thinning process for production of bare chips. The result of thinning is shown in the photograph (Fig.3). Thinning was made to 30–40 μ, however, the serviceability of the crystal was preserved. Potentially, the technology allows of thinning chips to 10–15 μ.
Application of the hybrid technology (ultrathin crystal technology and InkJet multilayer interconnecting layers technology) provided for manufacturing of the required basic blocks of the platform [4–6]:
Superflat flexible resistors (Fig.4) are made according to the InkJet technology (bubble-jet multilayer application) and have the following parameters:
thickness to 30 μ;
bend radius from 0.1 mm;
rating from 1 Ohm to 1 MOhm.
Superflat flexible inductor coils and microantennas (Fig.5) can also be used as the sensor elements of physical values; they are made with the use of InkJet technology (bubble-jet multilayer application) and have the following parameters:
bend radius from 1 cm;
rating from 10 nH to 1 mH;
thickness to 30 μ.
The wireless digital interface unit (Fig.6) is made with the use of the hybrid technology and InkJet technology (bubble-jet multilayer application) and has the following parameters:
protocol – NFC;
temperature sensor with the range from –20 to +60 °С;
thickness not more than 180 μ;
bend radius from 0.1 mm;
supply voltage – 1,8…3,6 V;
clock rate – 0.25…8 MHz;
working frequency of the RF unit – 13.56 MHz;
current drain in sleep mode not exceeding 10 μA;
temperature range from 20…+60 °С.
The microcontroller platform (Fig.7) is manufactured with the use of the hybrid technology and InkJet technology (bubble-jet multilayer application of interconnecting layers) and has the following parameters:
the entire unit thickness not exceeding 180 μ;
chip thinning from 325 to 35 μ;
bend radius from 0.1 mm;
CYPRESS CY8C20 microcontroller;
supply voltage – 1.71…5.5 V;
SRAM memory 16 kB; Flash NM – 256 K (32 kB);
I2C, USB, A-to-D converter 10 bit.
The memory unit (Fig.8) is manufactured with the use of hybrid technology and InkJet technology (bubble-jet multilayer application of interconnecting layers) and has the following parameters:
the entire unit thickness not exceeding 210 μ;
bend radius from 0.1 mm;
supply voltage – from 1.65 to 2.0 V;
current drain in standby mode not exceeding 180 μA;
current drain in the recording mode not exceeding 40 mA;
memory space – 512 Mb;
temperature range –40…+85 °С.
The developed technology makes it possible to manufacture chips on flexible ceramics or flexible glass which makes the device resistant to aggressive media while preserving their flexibility and minimum thickness.
The developed and produced functional chips (Figs.4–8) provided for the technological groundwork for manufacturing a flexible intelligent sensor platform (Fig.9).
The platform comprises: a processor module; a memory module; digital NFC interface; and temperature, pressure, humidity and gas-phase composition.
An example of the produced platform is presented by a prototype of the intelligent packaging (Fig.10). The prototype has the following parameters: NFC interface; measured acceleration ±2/4/8 g; measured temperature from –40 to +85 °C; and storage battery 15 mAh.
With a view of realizing the flexible printed electronic and photonics processes and developing the new generation technological clusters, an engineering centre was set up in SPEU "LETI" in 2016. This centre has opened a new in Russia segment of the engineering services that ensures the following advantages:
absence on the market of the Russian competitors that possess the required competency level;
restricted domestic access to this segment of the global market which develops dynamically;
availability of actual competency in the development of microsystems on a by-order basis with the university researchers;
unique personnel, intellectual, material and technical resources for establishing of the engineering centre and provision of engineering services. ■