New generations of robots are designed to support humans with a variety of partially or fully automated services. Such flexible and mobile service robots cooperate with humans or even act completely independent. To achieve this, it is necessary to significantly improve their capabilities in terms of environment perception, data processing and movement. At the same time, they must meet the highest standards of reliability and safety. Innovative electronics enable the necessary improvements and thus appropriate robot behavior. The aim of the Bionic RoboSkin project is to enhance the possibilities of a robot platform that is capable of autonomously navigating its respective environment by means of a flexible bionic sensor skin. The sensor platform is an autonomous underwater vehicle [AUV] that is based on the bionic principles of a Manta Ray [1, 2, 3]. The newly developed sensor skin consists of a textile composite as a carrier for sensor elements and provides moisture-resistant electrical connections for energy supply and communication. The integrated sensor modules enable both the detection of touch and approach and the exploration of the environment. The functionality of the sensor skin is targeting two service robotics applications: autonomous surveying of underwater structures (e.g. inspection of pipelines) and semi-autonomous geo-exploration in difficult-to-access areas (e.g. monitoring in tunnel construction). As a result, the paper presents the concept of a modular packaging platform for the use in a harsh marine environment. The technologies used for the miniaturization of the sensor module by PCB embedding and for outer housing development will be discussed in detail and a strong focus is put on packaging material properties in sub-marine conditions.

Autonomous robots for survey and control tasks are increasingly used in environments which can not or not easily be explored by humans. The autonomy of such platforms is based on representation or mappings of the local environment into which the robot is immersed. Advanced autonomous systems in natural environments typically record, evaluate and finally use a multitude of sensor data, e.g. for navigation or sample retrieval. Depending on the type of parameter a single sensor may be sufficient, but more often arrays of the same sensor type are distributed over the robot in order to provide the necessary data. As an example of a distributed sensor network we describe in the present paper the skin of an autonomous underwater vehicle. The vehicle is inspired by a manta ray: size and locomotion are the bionic copy of a ray. The skin of the vehicle is a textile which is permeable for water and spanned over the internal skeleton of the vehicle. The aim of the project “Roboskin” is to equip that skin with an array of sensor nodes to detect touch, nine axis-orientation, and pressure. The touch sensors, three on each wing, form the human machine interfaces [HMI] for the control of the vehicle by a diver. Orientation sensors are used for the self-representation of the robot movement and pressure sensors do monitor pressure distribution inside the vehicle while moving. Additional large area coils around the circumference of both wings are used for the detection of metals, which are related to the use case of the robot. The skin is equipped with a four wire bus structure stitched onto the skin of the robot. Two wires are for data (controller area network (CAN)-bus) and two for energy transmission. Touch sensors and metal detectors are likewise realized by stitching respective coils onto the skin. At defined positions “sensor housings” are joined up in the bus structure by plug connectors and mechanically fixed to the skin. They contain a connector structure for the miniaturized sensor nodes which are mounted into the housing and subsequently encapsulated with a lid. In order to realize as small as possible and highly robust sensor nodes, the electronic build up was realized using embedding technology of components into a printed circuit board. This allows the highest possible miniaturization of a heterogeneous system (i.e. non-monolithic), a high flexibility for design/fabrication modifications and an optimized protection of the electronic components. The resulting sensor node can easily be integrated into the housing, which is finally flooded with a protective grease to prevent water do diffuse into the electronics. The system specification of the device requires high density routing in a four layer printed circuit board build-up. Layer interconnects therein are a mixture of µ-vias and plated through holes. A single embedded layer contains more than 20 passive components with various package types and a number of active components like µ-controller, orientation sensors, and CAN-transceivers. All components are soldered onto the core prior to embedding into the printed circuit board by lamination. The embedded components were positioned with smallest possible spacing and are thus packed very densely. A particular challenge therefore is the configuration of the prepreg stack around the components, having different heights depending on component type, prior to the embedding. After lamination through holes and blind vias are drilled and plated, followed by photolithographic structuring of the copper. Finally onto the top side of the embedded module the pressure sensor is mounted as a single component on the outside of the embedded module. The yield of a typical fabrication run of the embedded sensor nodes is after ramp up above 90 %. Summarized this paper shows the potential of embedding technology towards maximum miniaturization and high robustness for a highly challenging application. Design rules for highest integration are provided and a brief description of target application including sensor data gained is given.

The technology to embed electrical components into build-up layers of printed circuit boards has considerably evolved during the past 20 years. Although the basic concept has been first described already in 1969, only 30 years later serious developments took place some of which have now reached full industrial maturity. At present there is not only a single embedding technology, but different approaches are used to embed components. Bare die embedding is nowadays industrialized and used as a packaging technology for a variety of different products. On the other hand, the embedding of surface mount devices into the build-up of the printed circuit board allows a high degree of miniaturization and improved robustness of more complex electronic systems. Although the principle is rather simple, it is far from being an established technology in a typical printed circuit board house. The focus of this presentation will be on the design, the types of components and processes for the surface mount devices embedding. The results of a representative variety of projects, which have been conducted at Fraunhofer IZM and TU Berlin during the past five years will be presented. In these projects highly integrated multi-component packages were fabricated in flexible and yet robust manner. It ranges from energy autonomous sensor node to record environmental data, which are transmitted wireless into an IoT data cloud. This module is equipped with a helix antenna, holds replaceable battery, and for the environmental data acquisition is equipped with a sensor that has an ambient access. Another example is an encapsulated sensor and control node integrated into the surface of an autonomous under water vehicle. In this module a single embedded layers contains about twenty passive components in various package types and a variety of active components like u-controller, orientation sensors, and CAN-transceivers (power and data transmission). As a third example an approach for embedded modules with a hermetic sealing which are used in harsh environments will be presented. The sealing of such modules realized by the integration of a ceramic platelet with electrical feedthroughs on top surface of the module, while all other surfaces of the module are fully covered with plated Cu. The ceramic platelet is connected to the wiring structure of the embedded build-up. Since the packing density of the embedded surface mount devices is typically very high, a tight and void-free encapsulation of the components with epoxy resin is critical during embedding process. In order to determine the appropriate prepreg stack for the build-up, detailed tests with respect to resin filling and the adhesion of resin and the surface mount devices were carried out. In some cases, surface treatments (wet cleaning, plasma, laser roughening) were used to improve the interface integrity. After initial fabrication runs to adjust process parameters and conduct first functional tests, typical production yields are in the range of 95 percent and higher, depending on the complexity of the embedded system.

Technologies and building blocks for the realization of reliable electronic systems for the use in harsh environments are attracting increasing intention. Harsh environments are for instance high temperature, pressure, mechanical stress and/or submerge into corrosive liquids, or the combination thereof. In the first place electronic components like integrated circuits or passive components which constitute the electronic system need to be operational under harsh conditions. On system level also the interconnections and package materials need to withstand the loading conditions. Printed circuit board embedding technology is a highly promising approach to realize this kind of electronic systems. Embedded semiconductors and passive components are mechanically protected from the environmental stresses by the epoxy/glass fibre compound into which they are encapsulated. Furthermore, novel types of high temperature laminate materials are commercially available since a few years. In an electroless plating process a fully hermetic metallic encapsulation can be added to the modules. This encapsulation acts as a protective barrier when they are immersed into corrosive liquids or gases. The external electrical connections out of the package are realized by ceramics with metallic feed throughs. They are assembled onto the modules (prior to the metallic encapsulation) using sinter-lamination-technology, i.e. the simultaneous build-up lamination and a sintering process. Two application demonstrators were realized in order to show the general viability of the encapsulation process. All used materials are commercially available. Industrial process equipment was used throughout the manufacturing. Subsequent reliability tests provide evidence for the general robustness and functionality of the modules under harsh environmental conditions. This work was part of the Fraunhofer lighthouse project “eHarsh” which was funded by the Fraunhofer Society.

Sensors are key elements for capturing environmental properties and are today indispensable in the industry for monitoring and control of industrial processes. Many applications are demanding for highly integrated intelligent sensors to meet the requirements on safety, clean, and energy-efficient operation, or to gain process information in the context of industry 4.0. While in many everyday objects highly integrated sensor systems are already state of the art, the situation in an industrial environment is clearly different. Frequently, the use of sensor systems is impossible due to the fact that the extreme ambient conditions of industrial processes like high operating temperatures or strong mechanical loads do not allow a reliable operation of sensitive electronic components. Eight Fraunhofer Institutes have bundled their competencies and have run the Fraunhofer Lighthouse Project “eHarsh” to overcome this situation. The project goal was to realize sensor systems for extremely harsh environments, whereby sensor systems are more than pure sensors, rather these are containing one or multiple sensing elements and integrated readout electronics. Various technologies, which are necessary for the realization of such sensor systems, have been identified, developed, and finally bundled in a technology platform. These technologies are, e.g., MEMS and ceramic-based sensors, SOI-CMOS-based integrated electronics, board assembly and laser-based joining technologies. All these developments have been accompanied by comprehensive tests, material characterization, and reliability simulations. Based on the platform, a pressure sensor for turbine applications has been realized to prove the performance of the eHarsh technology platform.

Sensors are key elements for capturing environmental properties and are increasingly important in the industry for the intelligent control of industrial processes. While in many everyday objects highly integrated sensor systems are already state of the art, the situation in an industrial environment is clearly different. Frequently the use of sensor systems is impossible, because the extreme ambient conditions of industrial processes like high operating temperatures or strong mechanical load do not allow a reliable operation of sensitive electronic components. Fraunhofer is running the Lighthouse Project ‘eHarsh’ to overcome this hurdle. In the course of the project an integrated sensor readout electronic has been realized based on a set of three chips. A dedicated sensor frontend provides the analog sensor interface for resistive sensors typically arranged in a Wheatstone configuration. Furthermore, the chipset includes a 32-bit microcontroller for signal conditioning and sensor control. Finally, it comprises an interface chip including a bus transceiver and voltage regulators. The chipset has been realized in a high temperature 0.35 micron SOI-CMOS technology focusing operating temperatures up to 300 °C. The chipset is assembled on a multilayer ceramic LTCC-board using flip chip technology. The ceramic board consists of 4 layers with a total thickness of approx. 0.9 mm. The internal wiring is based on silver paste while external contacts were alternatively manufactured in silver (sintering/soldering) or in gold-alloys (wire bonding). As interconnection technology, silver sintering has been applied. It has already been shown that a significant increase in lifetime can be reached by using silver sintering for die attach applications. Using silver sintering for flip chip technology is a new and challenging approach. By adjusting the process parameter geared to the chipset design and the design of the ceramic board high quality flip chip interconnects can be generated.

Efficient soft X-ray spectroscopy in the laboratory is still a challenging task. Here, we report on new toroidal multilayer optics designed and applied with the laser-produced plasma (LPP) source of the Berlin Laboratory for innovative X-ray technologies. The optics are described and characterized, and the application of the updated source to scanning-free grazing emission X-ray fluorescence is demonstrated on thermoelectric gold-doped copper oxide nanofilms. The comparison with synchrotron measurements allows estimating a flux on the sample of approximately 7.5 × 109 photons/s in the 1 keV range on a 100 µm × 100 µm spot, emphasizing the suitability of the updated LPP source for the application in photon hungry experiments.