GND is the main electrical ground connection between nRF9151 and the application board. It is also the main thermal dissipation path from nRF9151 and the main mechanical connection.
nRF9151 has ground pins (GND) which are also connected to a conformal shield. These are pins 1, 7, 13, 15, 20, 25, 30, 34, 36, 38–41, 43, 46, 51, 55, 60, 66, 71, 76, and 105–113.
Pins 15 and 40 are connected to nRF9151 ground through a conformal shield. Therefore, these pins do not provide as reliable an electrical connection as other GND pins and are not recommended to be used as a ground reference for any signal. For example, supply capacitors C3 and C4 near VDD pin 14 should not be grounded only through the nearby pin 15.
The connection between GND and the application board must be electrically, thermally, and mechanically strong. It is recommended that the application board PCB's ground planes around nRF9151 are as intact and as solid as possible. Use as many ground vias as possible between the top metal layer of the application board and the inner ground layers connected to nRF9151's GND pins. Typically, metal filled vias provide the best thermal conductivity.