Today, we're examining an intriguing case - a dead LG mobile that has overheated. This has been a common issue, especially since LG Electronics decided to shut down its mobile phone business worldwide. Despite promising to provide support and updates for existing models for a period, many devices like this one seem to fall into a category of planned obsolescence.
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As we begin the dissection of this LG phone, our first task is to measure the voltage at the battery connector using a tester or multimeter. We find no voltage there, yet we detect a voltage of 4.66 volts at the test points, indicating that current is indeed reaching the board from the charger. Intriguing, isn't it?
Upon removing the motherboard for visual inspection, we are met with a surprising find - solder balls on the SMD components due to overheating. This gives us clear evidence of extensive overheating, visible in many areas on the motherboard. This raises a red flag and supports our initial hypothesis of planned obsolescence by LG, given the vast amount of solder balls present across the motherboard.
Despite the daunting task, my curiosity prompts me to proceed. We remove the shields to uncover the extent of the damage. Under the microscope, the visual inspection reveals solder balls scattered everywhere. Upon measuring next to the PM7250B IC, we detect a short-circuit in the capacitors, and an unusually high consumption of 0.4 Amps or 400 milliamps when the charger is connected.
Using a thermal camera, we notice an abnormal heating area in the memory. The next step is to lift the memory. To do this, I use a hot air station at 400ºC, 40% air flow, and no nozzle, along with a flexible metal tool.
The short circuit on the motherboard vanishes once the memory is lifted. We proceed with reballing the memory after cleaning the integrated circuit and removing the old solder. To ensure a clean slate, we change the solder alloy using a low-temperature solder paste (138ºC), which facilitates the cleaning of the old solder.
Before soldering the memory back, we apply some flux to improve the soldering of the circuit. After the circuit settles itself at the optimal temperature, we clean the area with contact cleaner or isopropyl alcohol.
However, upon final inspection with the thermal camera, it seems the short circuit has returned, and the memory heats up in the same sector, indicating internal memory damage. It's an unfortunate confirmation that this LG mobile phone's days are numbered, a casualty of LG's decisions and the evident planned obsolescence.
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