SPD Flash Tool – How to Flash Unisoc / Spreadtrum Firmware (.PAC)
Learn how to use RSD Lite to flash SBF firmware on older Motorola and Droid devices. This guide covers Motorola USB driver setup, SBF file loading, bootloader entry, and flash recovery — plus guidance on when to use RSD Lite versus Motorola Software Fix for newer devices.
Pre-Flight Checklist
Complete ALL items before proceeding. Skipping any step increases the risk of bricking your device.
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Backup all data before proceedingFlashing via SPD Flash Tool wipes your device completely. Back up contacts, photos, and files using a file manager or cloud backup before starting.
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Battery charged above 50%A low battery mid-flash can brick your device permanently.
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Correct Spreadtrum / Unisoc .pac firmware for your exact modelSPD Flash Tool uses <code>.pac</code> firmware files — a single package containing all partitions. Confirm the firmware matches your exact device model and region. Do not use firmware for a different model.
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SPD Flash Tool (SPD Upgrade Tool) downloadedThe current version is R27.25.4601, also known as SPD Upgrade Tool or FactoryDownload. It is Windows-only and compatible with Windows XP through Windows 11. Download from a trusted source and verify the file before running.
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Spreadtrum USB Drivers installedInstall the Spreadtrum SPRD USB drivers before connecting your device. Without them, SPD Flash Tool will not detect the phone.
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Antivirus temporarily disabledSecurity software often flags SPD Flash Tool. Disable it or add the tool folder as an exclusion before running.
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Running SPD Flash Tool as AdministratorRight-click the executable and select "Run as administrator". Required on Windows 10 and 11.
Guide Steps
Extract your downloaded firmware ZIP or RAR. You should find a single .pac file — this is the complete Spreadtrum/Unisoc firmware package containing all partitions.
.bin or individual .img partition files instead of a .pac file, it is intended for ResearchDownload Tool — not SPD Flash Tool. These are two different tools..pac file. The tool reads the internal header to identify the device and firmware version.Right-click SPD_Upgrade_Tool.exe (or FactoryDownload.exe depending on your version) and select "Run as administrator".
The main interface shows a port/status panel and the firmware load area. The status bar at the bottom shows Ready. Do NOT connect your device yet.
- Click the Load Packet button (folder icon). A file browser opens filtered for
Packet Files (*.pac). - Navigate to your firmware folder and select the
.pacfile. - SPD Flash Tool reads the packet header and populates the partition table automatically. You will see the firmware version and device info displayed.
- Verify the product name or model shown matches your device before proceeding.
In the options panel, select your flash mode:
- Erase + Download — Full wipe and reflash. Recommended for fixing bootloops, brick recovery, or a clean install.
- Download Only — Flashes firmware partitions without wiping user data. Less reliable for recovery — only use if you specifically need to preserve data.
Power off your device completely. Then connect it to the PC via USB:
- Simply plug in the USB cable with the device powered off — most Spreadtrum/Unisoc devices enter download mode automatically.
- On some models, hold Volume Down while connecting.
SPD Flash Tool detects the device and the port indicator turns green. You will see the COM port number appear in the status panel.
Click the Start Downloading button (green play arrow). The progress bar and partition statuses update in real time as each partition is written.
Flashing typically takes 3–8 minutes depending on firmware size and USB speed.
When complete, the tool shows PASSED in green and the device reboots automatically.
The device reboots after flashing. First boot may take several minutes as Android sets up. Do not interrupt or press any buttons during this time.
After booting, complete the setup wizard and verify the firmware version at Settings → About Phone → Build Number. It should match the firmware you flashed.
Congratulations! Flash Successful!
You've successfully completed all steps. Your device should now be running the new firmware. If it's booting normally — you're done! Check the troubleshooting section below if you encounter any issues.
Troubleshooting & FAQ
Common errors and their solutions. Read this before asking for help.
This is almost always a driver issue. Uninstall and reinstall the Spreadtrum SPRD USB drivers. Try a USB 2.0 port — USB 3.0 ports cause detection issues on some setups. Try connecting without holding any button, or try holding Volume Down. Confirm your device uses a Spreadtrum/Unisoc chipset — not MediaTek or Qualcomm, which require different tools.
The firmware is likely mismatched for the model or region. Check your exact model number in Settings → About Phone (if accessible) or on the label under the battery / in the SIM tray. Download firmware that matches exactly and re-flash using Erase + Download mode.
Both flash Spreadtrum/Unisoc devices but use different firmware formats. SPD Flash Tool (SPD Upgrade Tool) works with .pac packet files — a single file containing all partitions. ResearchDownload Tool works with individual .bin partition files (fdl1.bin, fdl2.bin, system.img, etc.) and gives more granular partition control. Always check which tool is bundled with or specified by your firmware package.
No — SPD Flash Tool is Windows-only (XP through Windows 11). There is no official macOS or Linux version. Running it in a Windows virtual machine with USB passthrough is the most reliable workaround for non-Windows users.
The latest version is R27.25.4601, which is compatible with most modern Unisoc chipsets. For older Spreadtrum devices (SC6xxx, older SC9xxx), an older version may be required — check the firmware package or device community for the recommended version. Using a version that is too new for an older chipset can cause connection failures.
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