Motherboard died

[rob77]

Here's a repair I did on a motherboard with the same problem: http://fubar.gr/successful-gigabyte-ga-h55m-s2-motherboard-repair/

I only heatsinked the replaced mosfets and soon after the mosfets from another phase blew up. So make sure to heatsink them all.

gluing a heatsink to the plastic body of the mosfet is useless - you can achieve much better results via proper airflow around the board - the PCB is the mosfet's only heatsink because the heat is dissipated through the metal back of the mosfet (not the plastic part).

Gaming mobos are factory equipped with heatsinks like this.

Heatsinks on plastic are not very efficient, but it is a stretch to call them useless.

heatsink on a plastic body of a memory chip makes sense because it's better than nothing and there is no other way to heatsink a memory chip , but it's really useless to place a heatsink to a plastic part of a mosfet...  thermal resistance is pretty much like any other resistance ..... it's like placing a 1megohm resistor in paralel with a 1kiloohm resistor and expecting a resistance significantly  lower than 1 k
gaming mobos might have heatsinks  like that on mosfets because it sells better

[jitter]

Agreed, heatsinking through the plastic part isn't going to be very effective, hence the reason why for serious heatsinking these SMDs, it must be done through the copper of the board, like this:



Of course, that will only be possible if the board has the requisite pads and space around the component (as indicated here by the silkscreen):

[technix]

Were you running the CPU at near 100% load? It could just be bad thermal connection to the heatsink causing the MOSFET to overheat.

I never ran the CPU at 100% or near to. I did however replaced my E5700 processor with a Q9550 which get warmer/hotter.

This is probably the culprit - the mobo never intend to power the quad-core chip which have significantly higher power draw.

[amyk]

If you're going to replace one MOSFET, might as well upgrade all the others too... you can find ones with lower Rds(on) and similar gate charge, like this one:

http://www.mouser.com/ProductDetail/Infineon/IPB042N03L-G/

Lower Rds(on) will make them run cooler.

[Tomvv]

Today I received my hot air soldering station in the mail.

Next step is to order the replacement MOSFETS.

From what I understand the IPB042N03L-G is a suitable replacement correct ( since the qc = close to 15nc and the VDS 30V )?

[Marco]

Of course, that will only be possible if the board has the requisite pads and space around the component (as indicated here by the silkscreen)

You could solder to the exposed part of the metal back.

[JoeN]

Hot air and possibly preheating to get that off (and on).

Chipquick can be very helpful - it melts at a lower temp and mixes with the solder lowering the overall melting point.  Not 100% sure if it would be helpful where there is a huge joint like on the heatsink but it would help with the pins for sure.

[paulhm81]

This is a known problem and you should not classify a mb as poorly designed because of this. You should replace all mosfets in that area as they were subject to the same thermal stress. You can buy some sticky heatsinks like this ones - http://www.aliexpress.com/store/product/100pcs-lot-GDT-X8-Blue-Aluminium-Heatsink-For-Motherboard-DDR-VGA-RAM-Memory-IC-Chipset-Cooling/515717_32393551662.html

Your PSU is probably ok but the paperclip is not really a test. It can work with the paperclip because it has no load and still fail connected to the mb. Add a 2-3 old hdd-s while you test it.