Packages based on the Antenna-in-Package approach and designed for mmWave applications are large in area size, e.g. due to size of patch antennas and their pitch in an array. High frequency-able package materials that have comparably high Young's modulus and low coefficient of thermal expansion are needed to match the electrical performance. Both geometry and materials influence the warpage behavior of the package during fabrication as well as under use case conditions. In this work, a comparative study on warpage throughout the fabrication process is carried out and focuses on two different FR4-materials being used. In addition, warpage effects on occurring solder joint shapes and package robustness during temperature cycling test done at -55 °C to +150 °C for up to 750 cycles are assessed at board level. To reveal package and solder joint robustness cross sectioning was done.