Characterization and Benchmark of a Novel Capacitive and Fluidic Inclination Sensor

In this paper, a fluidic capacitive inclination sensor is presented and compared to three types of silicon-based microelectromechanical system (MEMS) accelerometers. MEMS accelerometers are commonly used for tilt measurement. They can only be manufactured by large companies with clean-room technology due to the high requirements during assembly. In contrast, the fluidic sensor can be produced by small- and medium-sized enterprises (SMEs) as well, since only surface mount technologies (SMT) are required. Three different variants of the fluidic sensor were investigated. Two variants using stacked printed circuit boards (PCBs) and one variant with 3D-molded interconnect devices (MIDs) to form the sensor element are presented. Allan deviation, non-repeatability, hysteresis, and offset temperature stability were measured to compare the sensors. Within the fluidic sensors, the PCB variant with two sensor cavities performed best regarding all the measurement results except non-repeatability. Regarding bias stability, white noise, which was determined from the Allan deviation, and hysteresis, the fluidic sensors outperformed the MEMS-based sensors. The accelerometer Analog Devices ADXL355 offers slightly better results regarding offset temperature stability and non-repeatability. The MEMS sensors Bosch BMA280 and TDK InvenSense MPU6500 do not match the performance of fluidic sensors in any category. Their advantages are the favorable price and the smaller package. From the investigations, it can be concluded that the fluidic sensor is competitive in the targeted price range, especially for applications with extended requirements regarding bias stability, noise, and hysteresis.

Feasibility Study of Soft Tooling Inserts for Injection Molding with Integrated Automated Slides

The production of injection-molding prototypes, e.g., molded interconnect devices (MID) prototypes, can be costly and time-consuming due to the process-specific inability to replace durable steel tooling with quicker fabricated aluminum tooling. Instead, additively manufactured soft tooling is a solution for the production of small quantities and prototypes, but producing complex parts with, e.g., undercuts, is avoided due to the necessity of additional soft tooling components. The integration of automated soft slides into soft tooling has not yet been investigated and poses a challenge for the design and endurance of the tooling. The presented study covers the design and injection-molding trial of soft tooling with integrated automated slides for the production of a complex MID prototype. The design further addresses issues like the alignment of the mold components and the sealing of the complex parting plane. The soft tooling was additively manufactured via digital light processing from a silica-filled photopolymer, and 10 proper parts were injection-molded from a laser-direct structurable glass fiber-filled PET+PBT material before the first damage on the tooling occurred. Although improvements are suggested to enhance the soft tooling durability, the designed features worked as intended and are generally transferable to other part geometries.

Development and Validation of a Novel Setup for LEDs Lifetime Estimation on Molded Interconnect Devices

Higher energy efficiency, more compact design, and longer lifetime of light-emitting diodes (LEDs) have resulted in increasing their market share in the lighting industry, especially in the industries of consumer electronics, automotive, and general lighting. Due to their robustness and reliability, LEDs have replaced conventional light sources, such as fluorescent lamps. Many studies are examining the reliability of LEDs as such or investigating their long-term behavior on standard printed circuit boards (PCB). However, the thermal performance of LEDs mounted on nonconventional substrates is still not explored enough. An interesting example for this is the molded interconnect devices (MID), which are well known for the great design freedom and the great potential for functional integration. These characteristics not only underline the main abilities of the MID technology, but also present some challenges concerning thermal management. The long-term behavior of LEDs on MID is still quite untapped and this prevents this technology from consolidating its existence. In this context, this work highlights a developed test setup aimed at investigating LEDs, mounted on molded interconnect devices, under combined stress conditions. The results of the reliability study, as well as the resulting lifetime model, are also illustrated and discussed.