After being dropped multiple times by a child, the Xiaomi 10 cannot boot and went completely dead, black screen, no vibration, no response. This guide walks through professional troubleshooting and CPU reballing that brought the device back to life. Nota: Advanced micro-soldering skills required.
Modello: Xiaomi 10
Annunciato: 2020, 13 febbraio
Fenomeno dei difetti
The Xiaomi 10 had been used as a toy by a child, suffering multiple consecutive drops onto hard surfaces. Eventually, the screen turned black, and the phone stopped booting entirely. No signs of life (no LED, no vibration, no display response). Initial assumption: severe physical shock caused internal component fractures or poor solder joints under the CPU or power management ICs.
Tools & Equipment Used
- Heating pad (preheater)
- Set di cacciaviti di precisione
- DC power supply (0-30V)
- Soldering station & hot air rework
- Solder wick / desoldering braid
- Tweezers (ESD safe)
- Solder balls (reballing stencil for SDM865)
- Multimetro
Troubleshooting & Initial Checks
Separate the display assembly
- Place the phone on heating pad to soften adhesive, carefully separate the screen.
- After separation, we confirmed the motherboard had no previous repair history or water damage.
- No prior repair marks — all seals original.
Battery voltage measurement
Quindi rimuovere la bobina di ricarica wireless e tutte le viti, quindi misurare il valore di tensione sulla batteria.
Battery voltage checked: nominal range (around 3.8-4.2V) — battery is healthy.
Despite normal battery voltage, the phone didn’t respond to power button. Next, we moved to motherboard-level diagnostics.
Power injection via DC supply
- Solder a wire to positive DC input for precise current monitoring.
- Connect motherboard to bench power supply & trigger boot.
The boot current peaked at only 50mA and then dropped back to 0 — a classic symptom of CPU not initializing or short on CPU core power rail. Based on experience, this points to CPU poor soldering or loose inductors around the PMIC.
Repair Process: From Inductor Check to CPU Reballing
Check for loose inductors (PMIC area)
- Check for any poorly soldered inductor.
- Push each inductor around PMIC with tweezers — all firmly attached, no loose components.
Remove power management shielding cover
Remove the shielding cover on the power supply chips, keeping it aside as it will be needed to solder back after the repair is complete.
Carefully desolder shielding cover & keep it for reassembly.
Inspect components under the shield: no visible cracks or burnt parts. Everything looked normal.
CPU shielding removal & reballing preparation
Il passo successivo consiste nel risaldare il chip della CPU per fare una prova e rimuovere prima il coperchio di schermatura.
- Remove the top layer of the CPU chip first.
- Upper layer (Samsung DRAM) detached successfully.
Upper (RAM) chip removal: Hot air rework station used to lift the upper layer (DRAM).
Lower layer (Qualcomm Snapdragon 865) removal:
Carefully remove the primary SoC.
Clean PCB pads & reball the CPU layers
Xiaomi Mi10’s CPU is not sealed with glue, making pad cleaning easier as you only need to use a solder wick to remove and flatten the tin pads.
Clean PCB pads thoroughly, apply flux, wick away residual solder.
Upper layer reballing (RAM):
Reball RAM chip using fine solder balls & stencil.
Evenly distribute solder balls on the SoC for reliable connection.
Solder CPU & RAM back to motherboard
We need to resolder the two layers of the CPU to the motherboard.
Align CPU precisely and reflow.
CPU & RAM fully soldered — tidy and clean.
Final Assembly & Power-On Test
After CPU reballing, we temporarily assembled the phone (display, battery connected) and powered it on. Success: the Xiaomi 10 booted normally to the Mi logo! All functions working.
Finally, solder back the shielding covers to ensure EMI protection and reassemble completely. Re-test Wi-Fi, cellular, display touch, cameras – all passed.
Shielding covers restored, motherboard ready for final placement.
Final result: Xiaomi 10 fully restored — everything working 🎉
Expert insight: Xiaomi Mi10 motherboard lacks CPU underfill glue, which makes desoldering easier but also means repeated drops can cause micro-cracks under the SoC. Reballing resolves intermittent connections. The 50mA boot current that drops to zero is a hallmark of CPU not responding — reballing revived the device.
Domande frequenti
Why does my Xiaomi 10 not turn on after dropping it?
Physical shock often dislodges CPU solder balls or cracks joints beneath the processor or PMIC. This interrupts power sequencing and booting. As in this case, reballing the CPU fixed the issue.
Can I fix a dead Xiaomi 10 myself (no boot) without soldering?
Basic checks (battery, charging port) can be performed by users. However, if current draw suggests CPU failure, professional micro-soldering equipment and experience are mandatory. Attempting reballing without training may permanently damage the motherboard.
What does 50mA boot current mean on a dead phone?
It typically indicates that the PMIC starts but the CPU does not respond (no proper core voltages or processor not executing code). This points to loose CPU soldering, damaged power rail, or bad SoC.
How to prevent drop damage on Xiaomi 10?
Use a rugged case and tempered glass screen protector. Avoid letting children use the device unsupervised. This phone has no official glue under CPU, so repeated shocks are risky.
Is CPU reballing a permanent repair?
When done correctly with high-quality solder balls and proper reflow profile, the repair can be very long-lasting. However, if the phone suffers another severe drop, the issue may reappear — always consider shock absorption.
Conclusione:
Continuous dropping caused the Xiaomi Mi 10 to stop booting. Diagnosis (battery voltage check, DC supply current analysis, inductor inspection) identified poor CPU soldering as the issue. Reballing, removing the RAM and Snapdragon 865, cleaning pads, applying new solder balls, and reflowing, restored the phone. It now boots reliably, passes all tests, and is ready for use.
Note: Reballing requires precision. Use proper ESD protection, flux, and a preheater to prevent board warping. This guide is for information; seek professional help if you lack the necessary skills.
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