Reliability of LTCC RF SiP Plate Antenna Solder Ball under Random Vibration Simulation

Active phased array radar (APAR) is equipped with a transmitting/receiving (T/R) component for each radiator, and the T/R component is interconnected with the PCB through solder balls. With the development of avionics equipment towards high-density integration, miniaturization and multi-function, the fatigue failure of interconnect solder balls caused by mechanical vibration has become one of the key problems restricting the long-life service of spaceborne active phased array antenna equipment. In the process of manufacturing, testing, transportation and service, the plate antenna will be subjected to mechanical vibration under complex working conditions. The vibration load causes the printed circuit board (PCB) to bend up and down and produce dynamic displacement, which leads to the displacement and deformation of the lead and solder ball on the PCB, and ultimately leads to the failure of the lead and solder ball. However, in the service process of the active phased array radar antenna, in addition to the vibration load, the assembly stress generated by the antenna and the heat dissipation cold plate will act on the cover plate of the plate antenna during the whole tooling process, resulting in the interconnection of the plate antenna. The solder ball is in a complex stress state, and the mismatch of the thermal expansion coefficients of various materials may cause warpage of the PCB after reflow soldering, which may affect the reliability of the active phased array radar antenna. Therefore, aiming at the application of low temperature co-fired ceramic (LTCC) RF system-level package (SiP) plate antenna in active phased array radar, this paper carries out random vibration simulation in the Z-direction frequency range of 10-2000 Hz, and analyzes the influence mechanism of assembly stress, PCB warpage and solder characteristics on the stress and strain evolution of T/R module interconnection solder ball. The results show that the existence of assembly stress and PCB warpage will inhibit the dynamic displacement of PCB, thus increasing the reliability of interconnection. However, under the coupling effect of assembly stress and random vibration load, the vibration resistance of low lead solder (Pb37Sn63) is worse than that of high lead solder (Pb90Sn10).