A (Spreadtrun Update Package) is the proprietary firmware format used by Spreadtrum/Unisoc chipsets. It contains all the necessary partitions (boot, kernel, system, user data, etc.) in a compressed, checksum-verified package. You cannot use standard *.bin or *.img files directly; the flash tool requires a single .pac file.
Use the SPD Flash Tool (ResearchDownload) or specialized boxes like Avenger Spreadtrum Module . nokia ta-1174 spd flash file pac
TA-1174_SW_UPDATE_Vx.xx_User_PAC.zip Nokia_2.2_SC9863A_Android_10_PAC A (Spreadtrun Update Package) is the proprietary firmware