Tips for a Successful Reflow

Remove Chip Sealant

Most GPU Chipsets will have some sort of sealant or glue used on the edges of the chip to secure it to the motherboard (usually red, black, or clear) I have had many successful repairs without removing this sealant, though it is best to remove it prior to reflow to allow the flux and heat to enter.

Removal of the sealant should be done as part of the reflow process, the beginning of the process. You begin heating the GPU without the coin-stack, holding the tip of the heat gun roughly 3 inches away from the chip at a 45 degree angle and circling the chip while you heat it. You move around the chip in a circular motion aiming the heat between the chip and board. The best thing to do would be to get the Cone Tip (looks like a 3 tier cake) for the process. Use either the cone tip or an exact fit Square tip for reflowing.

Begin heating the chip and monitor the temperature with an Infrared Laser Guided Thermometer (if available) to a temperature of 145 degrees Celcius.

REMEMBER that you must insulate any parts or components that will melt or can be damaged from the extreme temperature… This would include any plastic plug ports, CPU Dock, RAM DIMM ports etc... Use tin sheets or Aluminum Foil or similar… No need to wrap the motherboard like a Present though, just the components in the immediate area. It is also a good idea to cover the CMOS battery with foil; or remove if the plug-in type.

Once you have reached 145 degrees celcius, you will use a mini flat head screwdriver to remove 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 ?dig?… 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 ?peel? 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 ?peel? 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 area?, 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.

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 don’t use the dropper and dip a Q-Tip into the flux bottle to apply the flux.

Fan Mod

Modification of the Laptops Fan Thermal Control Feature cannot be done on all fans. Matter of fact, there are few models that will allow this. The laptops CPU/GPU fan is thermal controlled, and certain fans using a fourth controller wire can allow you to disable the fan speed control and run the fan at full speed – full time.

Take for instance the fan used on the HP DV series (not all)(the TX,2000,6000,9000 models) use a white wire (4 wires total) as the thermal controller wire. If you remove this white wire, the fan will run at full speed the whole time it is powered on. If you attempt this on a different model and you go to power it on but the fan doesn’t spin at all… You will not be able to Mod that fan and will have to re-plug the wire back in… Doing this and having it not work will not harm the laptop or ?blow anything?.

To do the mod, you need your Micro-sized flat head screwdriver to pull the plug wire lock upward to release the wire from the plug tip. Look on the white plug tip of the fan, you will see thin locking tabs on only one side (the opposite side is the flat side). This is the tab you will be prying up to release the wire from its housing. You will take the wire that you removed and bend it upward securing it to the wire set using electrical tape or using heat shrink wire tubing (purchased in electronics or home improvement stores).

Why A Thermal Pad Is Used, Not Paste or Shims

Laptop components such as the GPU and CPU and integrated RAM will generate heat when in use. And the Laws of Science and Physics will tell you that any part that heats and cools will also expand and contract. Why do you think the heat-sinks on the CPU/GPU all have some sort of spring loaded mechanism to secure them, whether it is heat treated metal that will allow for flexing; or, screws on Riser posts that have metal springs attached to them.

The CPU does not generate as much heat as the GPU and is why using thermal paste is sufficient. Certain GPUs will generate more heat than others, and it is usually the GPUs that have the Southbridge chipset integrated into them making the chip both the GPU and Southbridge Chipset in one. It is imperative that a thermal pad is used. Again, why do you think the manufacturers use them; definitely not to ?cut costs?; they’re used for a reason.

Thermal Pads are used on the GPU to allow for the natural expansion and contraction of the Chip and the upper flip chip that is secured to all GPUs. You can’t physically see this occurrence, yet it does happen. Laptop motherboard repairing deals a lot with Science and Physics along with Electronics, so it is good to know a little of each of these categories of study, the more you understand of each… the better.

If you replace the pad with something like a Copper Shim, you run the risk of applying too much pressure to the upper ?flip? chip and damaging it or its BGA connection to the GPU chip. ?Yah?, you will find a lot of people on the internet telling you that you should use a shim to replace the pad… Yet If you replace the pad with something like a Copper Shim, you run the risk of applying too much pressure to the upper ?flip? chip and damaging it or its BGA connection to the GPU chip. ?Yah?, you will find a lot of people on the internet telling you that you should use a shim to replace the pad… Yet they have no clue what they’re talking about… they do not know how these components operate to educate anyone on the subject. A shim can be used on GPUs that do not generate massive amounts of heat, like some Intel GPUs or certain ATI GPUs but I neither condone; nor recommend you do this.

If you remove the thermal pad thinking you can just apply some ?fresh? silver paste to the GPU… you are wrong. There is a ?gap? between the heat-sink and the GPUs upper flip chip, so if you use only paste on the GPU, the heat-sink will not make contact with the surface of the GPU… the paste is not thick enough, and the heat-sink must sit on the surface to properly dissipate the heat.