[HD2 General] motoi_bogdan:
well once again i must issue a warning.

based on the nature of the problem NO AMOUNT OF HEAT DISSIPATION MATERIALS WILL HELP. PLEASE DON'T ATTEMPT THE GUIDE ON THE FIRST PAGE!!

The problem can ONLY be solved by resoldering the CPU using specialized tools. Even so, at this time i have a 50-50 success rate and without proper bga ball reforming tools, i cannot save a device that has failed because of improper reheating.

To put it step by step the problem looks like this:

1. you start using the phone, doing some intensive things on it.

2. phone starts to heat up, actually the snapdragon chip (mostly cpu + gpu) will heat up.

3. the solder points - about 180 small balls (ball grid array - BGA) will start to also heat up and ...well.. like all things that heat up.. will start to expand (dilatation).

4. the resin that fixes the chip itself to the motherboard will stay fixed, as it has a higher dilatation point then that of the solder balls.

5. as the balls underneath the cpu continue to heat up and expand, an increasing amount of pressure will form because of the outside resin keeping the chip unable to move along with the expanding balls underneath.

6. Over time the balls will start to crack - small fissures in their structure will appears - the balls are trying to expand in whatever direction possible. The solder points can also fail due to thermal/mechanical stress.

7. the small cracks will break the electric connection between the motherboard and the chip.. at witch point you get either a freeze or restart.

8. as the chip cools down - the solder points will contract and the cracks will be filled out, therefore the phone will work as the cpu operates normally.

9. over time, as more and more cracks occur in the bga matrix, the thermal point at witch the chip fails to work correctly will get lower and lower. Remember, it only needs one cracked connection (out of couple of hundreds) in order to stop working. You can get in a situation where the phone freezes at about 30 degrees celsius or lower.

Now let's say your phone does freeze at 30 degrees celsius. And let's say it's summer. There are 34 degrees outside. The phone is unusable. So in order to try to fix it, you dismantle it and attempt to fix it using my heat dissipation method. Well what you actually doing is sticking a piece of metal to the cpu chip. Does it address one of the 9 steps of the problem above? Well ... NO. That's because, when you assemble the phone back and try to use it, the piece of metal of sticked to the cpu will also get at room temperature along with other things there and the whole phone. So.. you will have a cpu at 34 degrees, a battery at 34 degrees and... a piece of metal at 34 degrees. The solder balls still have cracks and they expanded at 34 degrees, leaving the cpu to an unusable state (remember, my example stated you have a phone that freezes at anything above 30 degrees).

Simply put, if you simply place a piece of metal over the cpu, it won't solve the broken solder points and the original problem. In order to do this, the chip's solder point must be melted down to some degree, in order to fill out the existing cracks in the bga matrix. This is done using a smd heating station and it's very risky even in a service center. In fact some service center won't even attempt this - while faced with the real scenario where the cpu soldering melts in an ..unwanted fashion during the process (let's say 2 small balls melt and touch each other - a short circuit is formed underneath the chip).

I'm sorry but at this time this is the only real option. My first hd2 survived the procedure, so once done properly it seems that the fix effectively solves all the problems (i can use the phone at 50-60 degrees measured at the outer casing level - with absolutely no problem, freeze or restart). The second hd2 however died in the reheating process, most probably because of a short circuit in the BGA matrix.