Introduction
A Moto G45 5G was recently received from a customer with an intermittent problem. While using the device, the phone would sometimes freeze completely and restart automatically.
The problem was not limited to random restarts. At certain times, the mobile network signal would disappear, while on other occasions the phone would become stuck on the Motorola logo during boot.
Because the phone could work normally at times and then suddenly develop these symptoms, a proper motherboard-level diagnosis was required.
During diagnosis, I found that the CPU was heating abnormally while using certain features of the device. Based on the combination of symptoms and my experience with similar motherboard faults, I suspected a CPU dry soldering / BGA contact issue.
The CPU was subsequently reballed and refixed, and after the repair, the Moto G45 5G started working normally.
Moto G45 5G Customer Complaint
The phone was received with the following complaints:
- Phone freezes while being used
- Phone randomly restarts
- Mobile network signal sometimes disappears
- Phone sometimes gets stuck on the Motorola logo
- Problem occurs intermittently
- Device may work normally for some time before the issue appears
These symptoms can sometimes lead technicians to suspect a software problem. However, the intermittent nature of the fault required further hardware diagnosis.
Initial Diagnosis
When diagnosing a phone with freezing and restarting problems, several areas can potentially be responsible.
Possible causes include:
- Software corruption
- Storage-related problems
- PMIC or power supply instability
- CPU-related faults
- Network/baseband problems
- Overheating
- BGA soldering/contact issues
- Other motherboard-level faults
Instead of immediately replacing or reworking a major IC, I focused on identifying where the abnormal behavior was coming from.
CPU Heating Abnormally
During testing, I noticed that the CPU was heating abnormally while the phone was being used.
The abnormal thermal behavior was an important clue because the original complaint was also related to instability under normal usage.
The phone could:
Work → CPU heats abnormally → phone freezes → restart
In some situations, the device could also lose network signal or become stuck at the logo.
This combination made the CPU area a major point of investigation.
Suspecting CPU Dry Soldering
Based on my repair experience with similar cases, I suspected a CPU dry soldering / BGA contact issue.
The CPU is mounted to the motherboard using a BGA connection. The solder balls underneath the CPU provide the electrical connections between the processor and motherboard.
If these connections develop poor contact, the phone may not necessarily become completely dead. Instead, it can produce intermittent problems such as:
- Random freezing
- Unexpected restarting
- Boot problems
- Logo hanging
- Network abnormalities
- System instability
- Problems appearing after the device becomes warm
This type of fault can therefore be challenging to diagnose because the phone may appear completely normal during some tests.
Why the Symptoms Were Intermittent
One of the important characteristics of this Moto G45 5G fault was that it was not permanently present.
The phone could boot and operate normally, but after some usage the problem could appear.
This type of intermittent behavior can occur with a poor BGA connection because electrical contact may be affected by factors such as temperature and mechanical conditions.
As the motherboard and CPU area heat up during operation, a marginal connection can become unstable and cause the device to freeze, restart, lose communication, or fail during boot.
Therefore, a phone that boots normally should not automatically be considered free from a motherboard fault.
CPU Reballing and Refixing
After completing the diagnosis and based on the suspected CPU BGA contact problem, the CPU was removed from the motherboard.
The CPU BGA area was then properly prepared for rework.
The repair process involved:
- CPU removal
- Cleaning and preparation of the BGA area
- CPU reballing
- Inspection of the solder balls and pads
- Proper CPU alignment
- CPU refixing onto the motherboard
- Post-repair testing
The objective was to restore reliable electrical contact between the CPU and the motherboard.
Repair Result
After CPU reballing and refixing, the Moto G45 5G was powered on and tested.
The phone returned to normal operation.
The original problems were checked, including:
- Freezing during use
- Random restarting
- Network/signal loss
- Logo hanging
- Abnormal behavior during operation
After the CPU reballing and refixing, the phone was working fine and the reported intermittent problems were no longer occurring during testing.
This confirmed that the CPU/BGA area was the source of the fault in this repair case.
Before and After Diagnosis
Before Repair
The phone showed:
Freeze → Restart → Signal Loss → Logo Stuck
along with abnormal CPU heating during use.
After Repair
After CPU reballing and refixing:
Boot Normal → Stable Operation → Network Working → No Freezing → No Random Restart
The device was successfully restored to working condition.
Important Lesson for Mobile Repair Technicians
A phone that freezes and restarts should not always be treated as a software problem.
When symptoms include:
- Random freezing
- Random restarting
- Network signal disappearing
- Logo hanging
- Abnormal CPU heating
it is worth investigating the motherboard carefully.
In this particular case, the combination of the symptoms and abnormal CPU heating led to the diagnosis of a CPU dry soldering/BGA contact issue.
However, CPU rework should not be performed solely from these symptoms. Other possible causes such as storage faults, software problems, power-rail instability, and related circuitry should be considered and ruled out where appropriate.
Moto G45 5G Repair Diagnosis Flow
Moto G45 5G received
↓
Freezing while using the phone
↓
Random restart
↓
Sometimes network signal disappears
↓
Sometimes stuck on Motorola logo
↓
Motherboard-level diagnosis
↓
CPU found heating abnormally
↓
CPU dry solder/BGA contact suspected
↓
CPU removed and reballed
↓
CPU refixed
↓
Full testing
↓
Phone working fine
Conclusion
This Moto G45 5G repair was an interesting example of an intermittent motherboard-level fault.
The customer initially reported freezing and restarting during use. The phone would also sometimes lose network signal and become stuck on the Motorola logo.
During diagnosis, the CPU was found to be heating abnormally while using certain features. Based on these observations and previous repair experience, a CPU dry soldering/BGA contact issue was suspected.
The CPU was reballed and refixed, after which the phone was tested again.
The Moto G45 5G is now working fine, with the original freezing, restarting, signal-loss, and logo-stuck problems resolved during testing.
This case demonstrates the importance of combining customer symptoms, thermal behavior, practical repair experience, and systematic motherboard diagnosis when troubleshooting intermittent smartphone faults.
Repair Case Summary
| Parameter | Details |
|---|---|
| Device | Moto G45 5G |
| Complaint | Freezing and random restarting |
| Additional Symptoms | Signal loss and logo stuck |
| Main Diagnostic Finding | Abnormal CPU heating |
| Suspected Fault | CPU dry solder / BGA contact issue |
| Repair Performed | CPU reballing and refixing |
| Final Result | Working fine |
| Repair Status | Successful |
