Note that parts like this are more easily replaced using a hot air station than a soldering iron.
Looks like the audio amp fed by the MOSFET is a Realtek ALC1304, which I can't find any data on, but searching for the pin names finds that it could be a clone/compatible to the TI TPA3131D2/TPA3132D2. This part has a power limiter, but if the Realtek one is configured the same way, then as implemented in the laptop, it has no power limit.
It is very likely that the reason the transistor failed was because of poor cooling, as it is a low cost, high-resistance transistor that is running near its design limits.
The MOSFET that blew up is rated for 2A continuous, and it's in the ~19-20V VIN circuit, so it begs the question of just how loud he was playing his music when it happened!
That said, not the first time laptops have come with sub-par audio circuitry:
Straight from the horse's mouth (mosfet datasheet):
Note: Using continuously under heavy loads (e.g. the application of high temperature/current/voltage and the
significant change in temperature, etc.) may cause this product to decrease in the reliability significantly even
if the operating conditions (i.e. operating temperature/current/voltage, etc.) are within the absolute maximum
ratings.
Please design the appropriate reliability upon reviewing the Toshiba Semiconductor Reliability Handbook
("Handling Precautions"/"Derating Concept and Methods") and individual reliability data (i.e. reliability test
report and estimated failure rate, etc).
Something like the SiA471DJ comes in the same pinout and package, has almost 1/10th the on-resistance, and over 10x the current rating. Moreover, its datasheet does not have such a lengthy disclaimer about its abilities:
If I were in the same situation I'd choose that part for a replacement --- sources online show it's basically the same price, and why replace it with the same failure-prone part just to risk it doing the same thing again? This isn't even a high-frequency application, it's just a power switch.
All mosfets are like that.
The marketing folksbL at Toshiba just were not able get it removed, or they have had one too many complaint from folks running them near the absolute max while not cooling them properly.
All datasheets for all parts contain a clause like this.
Have you ever wondered how manufacturers get lifetime estimates? They use an accelerated aging process which basically just means they run the part very hot and back-compute how long it would take to fail at normal temperatures. This is an industry standard practice that is (supposedly, I haven't verified) well backed by science. Running a part at elevated temperatures is somehow physically equivalent to running them longer at lower temperatures.
Heat and stress degrade silicon junctions. It's just physics. There's nothing particularly sketchy or unreliable about this specific part on its own. Probably whoever designed the amp circuit just made a mistake and under-spec'd this part.
>Note that parts like this are more easily replaced using a hot air station than a soldering iron.
Not to get into a soldering skills contest, but I'd rather use hot tweezers - hot air is the only viable option for components like QFNs and BGAs, but using it always carries the risk of accidentally disturbing neighbouring components, particularly if you're inexperienced. Affordable hot tweezers such as the Sequre HT140 are now readily available from China and make removing small SMD components almost effortless.
Looks like the audio amp fed by the MOSFET is a Realtek ALC1304, which I can't find any data on, but searching for the pin names finds that it could be a clone/compatible to the TI TPA3131D2/TPA3132D2. This part has a power limiter, but if the Realtek one is configured the same way, then as implemented in the laptop, it has no power limit.
It is very likely that the reason the transistor failed was because of poor cooling, as it is a low cost, high-resistance transistor that is running near its design limits.
The MOSFET that blew up is rated for 2A continuous, and it's in the ~19-20V VIN circuit, so it begs the question of just how loud he was playing his music when it happened!
That said, not the first time laptops have come with sub-par audio circuitry:
https://news.ycombinator.com/item?id=7205759
https://marcin.juszkiewicz.com.pl/2012/12/10/how-to-fry-spea...
https://apple.stackexchange.com/questions/100530/can-volume-...