Stability of Embedded Polymer Thick-film Resistors in 3D Printed Structures Compared to FR4-based PCBs

The article focuses on the stability of Polymer Thick Film (PTF) resistor (ED7500 paste) deposited on the surface as well as embedded in 3D printed modules based on ABS (Acrylonitrile Butadiene Styrene) and evaluates their behavior during accelerated aging. The deposition of PTF layers is performed using screen printing, and 3D printing is carried out using the Fused Filament Fabrication (FFF) process. For the integration of PTF resistors into the 3D structure, different embedding methods were used - bonding the bottom part with screen-printed PTF layers (ED7500 and ED3000) and the top part using heat and acetone. The aging results are compared with PTF resistors applied on the surface and embedded in PCBs based on FR4 material. The main evaluated parameter is the change in the electrical resistance of the resistors and the shrinkage of 3D printed structures during exposure of the samples to thermal cycling ($125^{\circ} \mathrm{C} /-45^{\circ} \mathrm{C}$) and temperaturehumidity test $\left(85^{\circ} \mathrm{C} / 85 \% \mathrm{RH}\right)$. The paper highlights the influence of materials and technological processes on the stability of resistors.