global Laptop and motherboard repair tutorial | Page 57

the sealant. Not a good idea to use a razor blade for doing this because if you accidentally dig into the
motherboard, you could rip or break one of the traces on the motherboard that run under the GPU
(there are Hundreds). Carefully hold the mini-screwdriver at a 45 degree angle and immediately after
taking the heat away from the chip, you want to begin scraping away the chip sealant. Nvidia chipsets
will mainly use the red glue, and the amount will vary. Some will apply it in dots around the chip,
some just at the 4 corners, and some will use the sealant the whole way around. Apply slight pressure
to start the scraping/peeling of the red epoxy… do not ―digǁ… you want the screwdriver as flat and
parallel to the chip/motherboard as you can get to help prevent scraping of the board or chip. If you
have reached the right temperature, removal should be easy, as it should ―peelǁ right off and away.
Do not dig under the chip as you can damage the connection or cause thermal spotting; especially if
you wedge any epoxy under it. You might need to heat the chip a couple times to completely remove
the sealant, if you notice it becoming harder to ―peelǁ the sealant you will need to apply more heat
(usually twice is sufficient).
Preheat the Underside of the Motherboard
Before the reflow process is started, yet, after the chip sealant has been removed, you can begin
to preheat the underside of the motherboard prior to reflowing the GPU Chipset.
This should be done without moving the motherboard during the reflow process. Meaning, you should
only be heating the underside of the board if you can set the motherboard up in such a way so that
after the underside is heated, you can quickly move to the top-side where the GPU is to begin heating
that immediately without moving the motherboard.
How This Is Done:
I work on a marble table, so heat is not a factor when worried about ruining the ―work areaǁ, and
I will place the motherboard over the edge of the table to expose the direct underside of the
motherboard. You are not heating the entire underside of the motherboard. Rather, you are heating just
the area directly opposite from the GPU (about a 2 inch by 2 inch area).
You will not do this if the underside of the board has plastic components placed near that area
because you will run the risk of melting or damaging these parts. You can also do this by using board
braces, whether you get yourself a professional PCB bracing system, or go to your local Home
Improvement store and make yourself one. You will need to have one with the capability of easily
flipping over or capable of flipping the board over without disconnecting it from the braces. Use a
cone tip on the heat gun if able to, heat the underside of the GPU and monitor the temperature using
your infrared thermal gun. You want to heat the area to around 180 degrees celcius, then as quickly as
possible, you will begin heating the GPU.
But wait…
Use Liquid Flux on GPU during Reflow
Right now is the perfect time to apply any liquid no residue flux to the outside of the GPU. You
can buy a Pen Applicator version of Liquid Flux, as opposed to a bottle with an eye dropper (more
common); I recommend you invest in the Pen style. To apply the pen style flux, you will shake the pen
for a few seconds to moisten the tip, dab the tip once to release flux into the tip, then carefully apply
the liquid flux around the chips edge where it meets the motherboard, the goal is that when the heat is
applied, the flux will flow under the chip to reach the BGA. You do not want to create Puddles under
the chip so do not use a lot of flux, you want enough so that you see it residing on the board, yet, not
so much that it starts to spread and flow without heating.
Is the pen is not available to you, and you are using a dropper to apply the flux, you should apply
1 drop to each side, or a half drop if able and spread it down the side using the tip of the dropper. Or