Jonas Jäger

Zusammenfassung

This paper investigates the utilization of digital printing technologies for the fabrication of low temperature co-fired ceramics (LTCC). LTCC offer great opportunities for applications such as antennas, sensors or actuators due to their outstanding properties like low dielectric loss, low permittivity, low coefficient of thermal expansion and at the same time high reliability in harsh environments (heat, humidity, and radiation). LTCC are multilayer circuits that are typically functionalized by screen-printing. This publication investigates the replacement of screen-printing by digital printing processes, such as inkjet and Aerosol Jet printing, to facilitate a more resource-friendly and customizable manufacturing of LTCC. The use of digital printing technologies not only streamlines small-scale productions and development processes but also offers the advantage of achieving miniaturization down to single-digit microns. In this publication, digital printing processes, filling of vias, lamination processes, co-firing at 850 °C and printing on fired LTCC were investigated. Three layers of nanoparticle silver ink were printed on green LTCC tape and 100% of the embedded printed structures were conductive after co-firing. Filling of vias with inkjet printing was investigated and the most important process parameters were found to be the clustering of vias, the amount of active nozzles and the substrate temperature. Printing on fired LTCC demonstrated high precision, and sintering at 600 °C achieved strong adhesion of printed structures to LTCC. These successful findings culminate in presenting a process chain for fully maskless structured, multilayer LTCC.

Zusammenfassung

Digitally printed conductive structures often need to be electrically connected to batteries, microcontrollers, or other devices. A consensus of industry and research is that such hybrid printed electronics will play a major part in the future of printed electronics. To promote the technology of hybrid printed electronics, surface mount technologies for electronic components using isotropic conductive adhesives (ICAs) and low melting tin bismuth solders on inkjet-printed silver structures on injection molded liquid crystal polymer (LCP) substrates were investigated in this publication. The special needs for inkjet-printed electronics were considered as well as the reliability of assembled surface mounted devices (SMDs) and their failure mechanisms. Connected 0603 and 1206 SMD components achieved a characteristic fatigue life of more than 3500 cycles during thermal cycling at +125 °C/−40 °C and withstood over 1000 h under a damp-heat atmosphere of +85 °C/85% RH. The coefficient of thermal expansion (CTE) of the substrate and the selection of solder have major impacts on the reliability of the assemblies.

Zusammenfassung

This paper describes the characterization of inkjet-printed resistive temperature sensors according to the international standard IEC 61928-2. The goal is to evaluate such sensors comprehensively, to identify important manufacturing processes, and to generate data for inkjet-printed temperature sensors according to the mentioned standard for the first time, which will enable future comparisons across different publications. Temperature sensors were printed with a silver nanoparticle ink on injection-molded parts. After printing, the sensors were sintered with different parameters to investigate their influences on the performance. Temperature sensors were characterized in a temperature range from 10 °C to 85 °C at 60% RH. It turned out that the highest tested sintering temperature of 200 °C, the longest dwell time of 24 h, and a coating with fluoropolymer resulted in the best sensor properties, which are a high temperature coefficient of resistance, low hysteresis, low non-repeatability, and low maximum error. The determined hysteresis, non-repeatability, and maximum error are below 1.4% of the full-scale output (FSO), and the temperature coefficient of resistance is 1.23–1.31 × 10−3 K−1. These results show that inkjet printing is a capable technology for the manufacturing of temperature sensors for applications up to 85 °C, such as lab-on-a-chip devices.

Zusammenfassung

Nowadays, digital printing technologies such as inkjet and aerosol jet printing are gaining more importance since they have proven to be suitable for the assembly of complex microsystems. This also applies to medical technology applications like hearing aids where patient-specific solutions are required. However, assembly is more challenging than with conventional printed circuit boards in terms of material compatibility between substrate, interconnect material and printed ink. This paper describes how aerosol jet printing of nano metal inks and subsequent assembly processes are utilized to connect electrical components on 3D substrates fabricated by Digital Light Processing (DLP). Conventional assembly technologies such as soldering and conductive adhesive bonding were investigated and characterized. For this purpose, curing methods and substrate pretreatments for different inks were optimized. Furthermore, the usage of electroless plating on printed metal tracks for improved solderability was investigated. Finally, a 3D ear mold substrate was used to build up a technology demonstrator by means of conductive adhesives.