I've recently started doing this and have found it to be
pretty easy. You have to learn the in's and outs of reflowing first
along with your tools. Using the same approach as above for
reflowing, when the gpu get's to the 220-230 mark and the gentle tap
shows it's floating, I turn on the suction for the chip removal pen
and pull the gpu off the board. Turn the heat off and let the board
cool. That's to remove the gpu. Once removed you need to take the
old spheres off the gpu and clean the board. Using a cheap non-clean
flux, put a generous amount on the gpu and board. You then tin the
tip of your solder iron with leaded solder and slowly move over the
old spheres while creating a growing blob of solder. Next take a good
solder wick and remove the old left over solder. Be sure to move
slowly and without applying any pressure to the board as you don't
want to pull any pads. Next clean the residue off with alcohol. I
recommend using these foam triangle wedges that they use for applying
makeup. I've found them to do the job of cleaning up the residue
without hurting or ripping away any of the pads. Now you have to
reball the gpu! ugh! I highly recommend getting the Honton HT-90
reballing unit. You can get these for about 30-50 dollars now. You
want to get the 90x90mm unit and then will need to use the 90x90
stencils. You can find kits now that will come with a ton of the more
common chips. Average is about 2-4 per piece for the stencil. You
will also need leaded solder spheres (63/37) and the most common size
is .50mm and .60mm. Also you will want to get a good flux to use and
I just started using Amtech Gel NC-559-V2. Put a small amount on the
gpu and wipe it around with your finger. You want it to look "wet"
and just a small thin layer. Using the reballing unit/stencil put in
the required balls and after emptying out the extra balls back into a
container, carefully lift the stencil. Inspect that all the spheres/
balls have found thier new home on thier pad and using a toothpick
move or put in any missing or mis-aligned ones. Once they look good
and are in place I turn on my hot air gun to 420c, air setting at 10
which is the lowest on mine and starting at about 6 inches over the
gpu, I slowly start moving it in a circluar motion while moving slowly
closer to the gpu. After about a minute and moving the wand slowly
around the gpu at a height of a half inch or so you'll see the spheres
pop into place and melt on thier pad. After all of them have melted
turn off the heat and inspect. If you have had any join together or
"bridge", you'll need to heat those and redo the bad ones. Once it's
all good, give it a little alcholol bath and prep it for mounting on
the board. Apply the Amtech flux on the board and mount the gpu and
align it by looking at the outline. You can also look at aligning the
chip while looking around the outside and seeing that the spheres
align over thier pad on the board. Once it's good, run your profile
on the station and heat the chip till around 190c. This is the
melting temp for the new leaded spheres. Once you see the chip get
pulled down and all the spheres are liquid, turn off the heat and let
it cool. If the gpu is good and all the spheres melted in the right
spot and you have no bridges, (yes alot of "if's) then when you turn
the board on you should be greeted with the usual bios/logo.
To do the reflowing and reballing and your just wanting to get
started, all you need really is a hot air wand/station and iron. You
can use a griddle for the bottom heater until you have the money to
get a good pre-heater. However you need to remember when doing the
rework most of the heat generated comes from the bottom with only the
last part coming from the top or area being reworked.
I hope that the above will help someone out.
)