Laptop thermal paste question

[Samastrike]

I don't know if this should go here or in the CPUs section but let's try here first.
I'm about to put a new CPU in my laptop (i7 2620m) and was wondering if it would be better to apply thermal paste in a rice grain and let the heatsink spread it, or if I should spread it myself.
Advice will be appreciated.

 

[paul878]

Spread it yourself!
The heat sink is not going to spread it for you evenly.

 

[dma0991]

It depends on the shape of the die. Typically mobile CPUs are bare die and pea method wouldn't work if the die is more of a rectangle than a square. It isn't necessary to spread it. Just lay out a thin line of TIM parallel to the longest section(assuming its a rectangle) or do the X method. The mounting pressure should allow the TIM to spread naturally sideways, giving sufficient coverage over the entire length of the die.

 

[paul878]

It depends on the shape of the die. Typically mobile CPUs are bare die and pea method wouldn't work if the die is more of a rectangle than a square. It isn't necessary to spread it. Just lay out a thin line of TIM parallel to the longest section(assuming its a rectangle) or do the X method. The mounting pressure should allow the TIM to spread naturally sideways, giving sufficient coverage over the entire length of the die.

OEM don't use line or X for a reason, they always come spread.

 

[dma0991]

OEM don't use line or X for a reason, they always come spread.

Depending on the manufacturing practice, they might or might not spread. Most of the time they just apply a gobsmacked amount of TIM and hope for the best. Too much TIM is a bad thing and causes overheating issues(1, 2, 3). Spreading is an optional step, which can be skipped as it introduces air pockets in the TIM, reducing thermal conductivity.

I've done TIM replacement on an Acer and Dell laptops, both have excessive amount of TIM that spills to the sides of the die. You won't get that much of overspill if it was actually using spread method.

 

[taq8ojh]

They often don't even use a paste, but rather those super stupidly useless thermal pads, which don't work for sh...

 

[paul878]

Depending on the manufacturing practice, they might or might not spread. Most of the time they just apply a gobsmacked amount of TIM and hope for the best. Too much TIM is a bad thing and causes overheating issues(1, 2, 3). Spreading is an optional step, which can be skipped as it introduces air pockets in the TIM, reducing thermal conductivity.

I've done TIM replacement on an Acer and Dell laptops, both have excessive amount of TIM that spills to the sides of the die. You won't get that much of overspill if it was actually using spread method.

Overspill to the side is no big deal, it has no affect on overall temperature.
All new heatsink (laptop and desktop) comes with TIM already spread.

From my experiences overspill from the factory is limited, the problem comes from untrained tech.

 

[dma0991]

Overspill to the side is no big deal, it has no affect on overall temperature.
All new heatsink (laptop and desktop) comes with TIM already spread.

From my experiences overspill from the factory is limited, the problem comes from untrained tech.

Overspill has some effect on the temperature as the excessive TIM will act like an insulator. You're referring to pre-applied TIM that has a consistency of thermal pad. Unlike off the shelf tubed TIM that you apply, pre-applied TIM on stock heatsinks do not smear like a paste.

Spreading takes more time and with the fast pace of the assembly line, controlling the amount of TIM with an easier, pea or rice grain method will be the better choice as the difference between spreading and not spreading is negligible.

 

[redyouch]

Spread with razor-blade or other flat tool.

 

[Samastrike]

I did it 3 days ago so too late for advice now.
Anyway, some results: I'm pretty sure I used a bit too much paste and I ended up just screwing the heatsink down to spread it for me instead of spreading it by hand. With the GPU (525M overclocked to 540M speeds) it's resulted in 15C cooler temps when running furmark, it only reached 74C after a few hours so I'd consider that a success.
The CPU I'm less sure about, I swapped an i3 2310m for an i7 2620m so obviously turbo boost is affecting the temps where it wasn't before so it's much harder to be sure how well it went. It easily reaches 80C, however it can remain at 3.2GHz pretty much indefinitely when plugged in from what I've seen so I guess that the paste is working well there too.
So even if I didn't do a particularly good job of applying the paste I'm very happy with how it's turned out. Thanks for the advice from the first few people who commented!

 

[PliotronX]

I've personally given up on the whole spreading an even layer kick. Pressure does better to occupy the air gaps and some pastes are just too damn thick to work with. On bare die it folds up on itself and it just takes too long and the temps never seem to be very good (don't doubt my spreading skills either). Dots or lines do the trick; excess is squeezed out anyway and through thermal cycling, optimal mating is reached.

 

[taq8ojh]

Just pressure works IF both surfaces are perfectly flat. That's not always the case, though.

 

[BrightSideSC]

I'm inclined to agree with everyone who has said pressure will spread it for you. It will, and it works just fine.