Warpage Prediction of mmWave Antenna-Inpackage Modules During Solder Reflow

Millimeter-wave (mmWave) technology promises to revolutionize communication by delivering faster data rates, higher capacity, and lower latency, while also enabling innovative applications such as combined communication and radar-like sensing. The mmWave technology allows for compact antenna designs that can be integrated directly into the package. In this work, we explore a prototype that combines beamforming capabilities, antenna structures, and frequency conversion into a single module. The complex interconnect routing, low-loss RF dielectrics, and the large lateral dimensions relative to its thickness lead to significant intrinsic warpage of the module. To address this, we developed a sophisticated simulation model to predict the warpage and optimize the module's design and material selection. Through both simulation and experimental validation, we found that using a low-temperature solder alloy (BiSnAg) and strategically placing solder bumps allows the modules to be successfully soldered onto a printed circuit board at <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$200 \mu ~\mathrm{m}$</tex> component spacing.