This should go without saying but...You are voiding your warranty by doing this. You also risk causing permanent damage to your motherboard.
If your laptop is still under warranty you shouldn't even be contemplating this. Send the laptop to Lenovo to get the motherboard replaced.
What are some symptoms of a bad solder connection? Well...
-If your display freezes when you move or bump your Thinkpad
-If you start up the laptop but there is no display at all but if you try starting it up while applying pressure on the GPU and it works
I have a bad solder connection between my GPU and my motherboard and I am currently using a wad of paper between the GPU and keyboard to make it work. The problem with this is that not only does it contribute to the existing problem, my system will only last about an hour before it freezes. Let's see if reflowing the solder connections will help...
This is a relatively short guide but make sure to read it carefully and make sure you have all the equipment you will need.
Items you will need:
Small phillips screw driver (thankfully all the screws are the same size)
Infrared thermometer (these can be had for $40 or less on eBay, and yes you NEED
it. DO NOT ATTEMPT WITHOUT THIS
1500w heat gun ($20-$30 on eBay)
Organizational scheme for screws
Let me talk briefly about your choice in infrared thermometer: make sure the maximum range is above 230c since this is the temperature we need to reach for a proper reflow.
Ok, I am not going to go into detail about how to take each piece off of the laptop. You are going to have to take every part of the laptop out, so just follow the hardware maintenance manual
Start by removing the simple stuff - keyboard, palmrest, cpu fan, memory, etc.
The next thing you should take off the laptop is the LCD screen. This will make taking everything else out easier. After removing the LCD you will be able to remove just about everything else easily. After taking out the LCD screen and the keyboard bezel remove the metal cages that hold the ultrabay drive and hard drive (you should have taken the hard drive out already). Also remove the PCMCIA ports while you are at it.
By now you will see why its a good idea to have a great organizational scheme for all the screws. There are quite a bit. We are now starting to get down to the motherboard.
Don't forget to take out the screw by the USB ports than connects the motherboard to the chassis. After you take out the remaining parts connected to the motherboard and chassis the board will slide out with relative easy.DO NOT FORGET TO REMOVE THE CMOS BATTERY!
I had a minor incident though, I left the CMOS backup battery connected. Despite it was hidden and inside the alunimum wrapping, it exploded during the reflow, causing a loud noise and smoke. There was no damage done to the board, I was lucky.
The next item on the list is to cover the board in the aluminium foil. Use two layers of foil and don't press it flat against the board. This will take away from the insulating properties of having a layer of air between the foil. However, you are going to want to crimp the ends that surround the GPU a little bit. This will help keep the foil together and the heat out. If you wrap the board correctly you won't have to worry about any of the plastic connectors - even the ones right next to the GPU.
So what's the next step? Add heat!
Now if you'll notice, I am holding the heat gun a distance away from the board. This brings me to one of the most important parts - you want to heat the GPU SLOWLY. Not like 1c and hour, but you don't want to blast it with the heat. About 10c a minute is a good rate until you get to 150c, then you can speed it up a little bit to 20c a minute.
Keep checking the temperature with the infrared thermometer. Doing a reflow is very hard if you don't know the temperature!
Once you see a temperature of 245c on the thermometer maintain this for a short period of time (10-20 seconds). You do not want to go above 260c. After maintaining 245c start cooling the GPU down. Just like how we heated the GPU up slowly, we are going to cool it down slowly too. Dropping the temperature by 15c a minute is a good rate. Once you get the temperature down to 150c you can turn off the heat gun and just let the board cool itself from there.
Now just play the waiting game. Wait until the GPU gets down to 38c before you even think about moving it. Do not get impatient! If the solder has not cooled down enough and you move it you WILL break it!
"But does it work?" you ask. Well, I will let my laptop speak for itself...
There are a couple of things I want to note. After you turn the computer back on you will need to reset the time and date and if you used the no 1802 bootable iso to allow a non-ibm wireless card you will need to use it again. When you remove the CMOS battery the BIOS resets itself.To the those who have ended up with non-working boards:
Do not attempt a second reflow. You should just buy a replacement motherboard. You might also want to have a look at this thread