[HD2 General] motoi_bogdan:
@harrrysekhon

a ... laser gun? i guess he refers to the infrared soldering stations. They use some infrared beams instead of the usual hot air and are safer because there is no risk of blowing other small components with the jet of hot air. Also they are more precise because they direct heat in a more specific and accurate way.

However the principle behind resoldering and reballing is the same. You heat up the chip, solder points are melted, you remove the chip, clean the area, place new solder balls using special bga grid made for that specific chip, you align and resolder the chip using heat. Be it from a hot air station or infrared (laser or not).

The problem remains, what about that resin? it still melts at a higher thermal point then that of the solder joints. You have to overheat the chip in order to make that resin more flexible and to break the bond. I thought at first that there will be no problem with removing the resin, just preheat it at 120 degrees and remove it with a sharp tool (like it's done on some other boards and chips). Not this one, is very close to the chip's outside pins, to the smd resistors near and seems to be some other sort of resin, i haven't worked with this as of yet. I decided not to take the risk. If there is a service center that can do this repair... by all means, but as i understand the risk... they would need some pretty funky and expensive tools to work with this sort of chip and resin.

@jotekman pure copper is more thermal efficient then mica foil. However mica foil is electrically non conductive. Copper is the opposite. It's kind of dangerous to have a copper plate near a board that's about 4cm by 5cm and contain some good couple of hundred connections. I decided that i would approach the problem in a more conservative way and use copper or anodized aluminum in direct contact with the chip itself only if mica foil is unsatisfactory. I went on the safe side at least when working inside the small enclosure made by the metallic shield over the cpu area. Outside i used copper and aluminum.

The basic idea was:

CPU

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thermal grease

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mica pads

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thermal grease

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aluminum top shielding

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thermal grease

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thick copper foil

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yep... thermal grease once again

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anodized aluminum foil

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yeah.. more thermal grease please

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about 3-4 mm thick aluminum foil folded together in 8-10 layers with thermal grease (the whole thing is hard pressed together.. very hard pressed together...)

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thermal grease.. yeah baby..

display's back (that's also aluminum i think, anyway it's metallic, it will help)

all those things are being pressed altogether when the board is assembled back.

Now regarding the solder points and possible cracking. Yep, be sure of that. EVERY HD2 that has this problem has cracked solder points. If i didn't believed this, i would not take any risk trying to reheat the cpu and i will also never mentioned of reheating in this topic. Although i'm not sure of it's direct effect, i simply cannot dismiss heating the cpu as helpful in some way. However, in this guide, it's the single most risky thing that can be done to the chip itself. I give it some sort of 50-50 chances. If you fail -> cpu dies either by overheating or by bga short circuit or more open tracks or cracks. The cpu doesn't simply restart on it's own because some thermal sensor inside it, says 30 degrees are bad for it's health. The miniature cracks already there, react under excess heat, some dilatation is happening over there, somehow the problem appears. A combination of cooling systems and pressure seems the only way for now. The other one being a professional reballing of that chip. And the last one.. motherboard replacement.