When the board cools, the balls are reformed with the help of flux, which gives them back their elasticity.
oven bake detailed later in the instructable), which causes a temporary re-alignment of the cracked solder balls.
The guy does a great job of showing not only how to disassemble, but reassemble, the PS3. This paste transfers the heat from the chips to the heat sink, and if your Play Station's paste looked like mine did, it's obvious it wasn't doing its job. To get the edges of the chip, soak a Q-tip with Goo Gone and wipe them off.
To clean it, drip a little bit of Goo Gone onto the chip you're cleaning and let it sit for about 30 seconds. When it's clean, wipe it down with rubbing alcohol.
But, while I'm not saying that these AREN'T the cause of your particular case of YLOD, I will say that most likely, the cause of your issue are the solder balls underneath the RSX (basically the GPU, or Graphics Processing Unit) and Cell BE (basically the CPU, or Central Processing Unit) chips. This style of fastening the chips to the board is know as BGA, or Ball Grid Array.
What you really need to know though, is that under the chips their are hundreds of tiny balls of solder, which pass information from the chip to the motherboard.