Efficient method for determining substrate parameters of additive manufactured spatial circuit carriers

Electronic devices are taking on an increasingly important function in industrial and private areas. Over the last 40 years, electronics have evolved rapidly, driven by Moore's Law. Now we have reached a point where further downsizing of semiconductors is no longer practicable. Thus, the third dimension is being used to drive integration spatially. This trend is now more and more evident for circuit carriers as well. Technologies such as Molded Interconnect Devices (MID) are being increasingly used in industrial and consumer applications, such as smartphones, tablets, sensors, etc. This technology combines the functions of the Printed Circuit Board (PCB) and the housing in one device. The substrate is usually based on plastic. Depending on the manufacturing process, a wide variety of plastics and coatings are used. The electrical properties of these materials must be precisely determined in order to correctly dimension for example microstrips, resonators or antennas with regard to their electrical behaviour. These parameters are often not available for the required frequency range. Thus, the circuit designer has to determine these necessary material parameters by himself. For the electrical characterisation of materials, a wide variety of measurement methods exist. Depending on the frequency range, an impedance analyser or a network analyser is required as well as a special fixture for the material specimen. These fixtures in particular are high-precision appliances that are not always available to the designer or are very expensive to purchase. In the following article, a method is presented which enables the characterisation of dielectric material samples without these sophisticated fixtures.