NVIDIA Chipset Problem #1

[bigbeark]

I have a few of these motherboards that were removed from ACER AM1640 mini-towers. The boards are made by MSI and are socket 775 with NVidia chipset. All boards either show no BIOS Codes or show D4.

On one board, I replaced a slightly bulging OST 6.3v 1000uf cap near the ram slots, and this was sufficient for the board to boot. The board would go into kernel panic as soon as it tried to access the hard disk. Similarly it would freeze if trying to read OS from a USB stick. This was after it had loaded the Ubuntu 10.4 OS using CDROM and IDE Drive.

I took another of these boards and replaced all the OST and Teapo caps with Panasonic and Nichicon and still no dice.

I am suspicious about the NVidia chipset.

Do these benefit from reflow, and if so do you use a heat sensor and thermometer to judge the heat coming from the heatgun? Do you apply the heat to the front or back of the chipset?

Suggestions welcome, thanks

[retiredcaps]

Re: NVIDIA Chipset Problem #1

I am suspicious about the NVidia chipset.

Do these benefit from reflow, and if so do you use a heat sensor and thermometer to judge the heat coming from the heatgun? Do you apply the heat to the front or back of the chipset?

Suggestions welcome, thanks

See my experience with it. YMMV. Mine is still working after almost 1 year. You apply heat on the front.

https://www.badcaps.net/forum/showthread.php?t=16609

[bigbeark]

Re: NVIDIA Chipset Problem #1

Did you remove any parts from the board or did you protect with foil or kapton tape?
In the video the guy appeard to have the heat gun 6 inches or so above the board.
I suspect if you have the heatgun closer you could "cook" for a shorter time.

What is the best technique?

[retiredcaps]

Re: NVIDIA Chipset Problem #1

At that time, I used aluminum foil. Now I have some kapton tape.

I held my heat gun about 2 to 3 inches away and used a circular motion.

I don't know if there is a "best" technique with these "crude" tools.

[Th3_uN1Qu3]

Re: NVIDIA Chipset Problem #1

I use the following method (thanks momaka!): Apply flux around the sides of the chip, then heat the chip from underneath until the flux flows inside. The top of the board should get to around 140C if you have a temp probe. Then heat it from the top, for around 3-4 minutes, to 230C. Let it cool down and that's all. I keep the heatgun around 2cm (~1 inch) above the chip, air set to 4 liters/minute, temperature 350-370C.

You need flux, otherwise it won't last long, or it'll cause the balls to stick together and you've ruined it.

[bigbeark]

Re: NVIDIA Chipset Problem #1

I use the following method (thanks momaka!): Apply flux around the sides of the chip, then heat the chip from underneath until the flux flows inside. The top of the board should get to around 140C if you have a temp probe. Then heat it from the top, for around 3-4 minutes, to 230C. Let it cool down and that's all. I keep the heatgun around 2cm (~1 inch) above the chip, air set to 4 liters/minute, temperature 350-370C.

You need flux, otherwise it won't last long, or it'll cause the balls to stick together and you've ruined it.

I have a 2-speed heat gun with no flow measurement. Settings are 250C and 450C. So I guess the 250C setting is the one to use. I don't have a temp probe, would consider getting one, recommendation? Finally the flux,
I have 3: a white water based paste in a tube, a plumbing paste that I suspect may be too acid, and a really hard Chinese one in a tub. I suspect you can recommend something better.

Thanks for everyone's help!

[Th3_uN1Qu3]

Re: NVIDIA Chipset Problem #1

250 may be too low, see what the temperature probe on your multimeter tells you. If your multimeter doesn't have a temperature probe, that's a good reason to get a cheapo 838 meter, it'll do. I'm sure you're going to find a lot of use for that probe. If 250C on the hot air gun does not bring the board to a high enough temperature, you can use the 450C setting, just keep the nozzle further away from the chip and cover the stuff around it with aluminum foil or kapton tape.

For the flux, buy a tube of Amtech flux. You can find it on ebay. There are a lot of fakes but they'll do just fine. I buy it locally and it's the fake stuff (obvious engrish on the label), and it does the job.

[momaka]

Re: NVIDIA Chipset Problem #1

If you have a temperature probe, place it on the top side next to the chip. If not... oh well - it's a dead board anyways (unless you feel that buying a temperature probe and meter is worthwhile - which IMO it is).

Start with the low 250C setting to preheat the board underneath the chip - that is, after applying flux around the chip, of course. Keep the heat gun about 20-25 cm away from the board. Do this for about 1 minute.
Then move ~10 cm closer to the board and heat for another minute. After that, have the heat gun at about 5-7 cm from the board and heat for another 2 minutes or more. This will depend on the heat gun, though. I say heat the board to about 200C at least. If you don't have a temperature probe, then you can look at signs from the flux to guesstimate the temperature. For example, I've used Kingbo flux and I know that around 170-180 it begins to smoke a bit. At 200C or more it smokes heavily. I also have a liquid flux that begins to boil at just 150C. It may be worthwhile to perform a small test with your flux on a junk PCB so see when it starts smoking/boiling and if the solder has melted at that point.
...
So, when the board temperature near the chip gets close to 200C or so, move your heat gun to the top side where the chip is and heat straight above the chip, about 5-7 cm away, for about 30 seconds. Then switch to the high 450C setting and pull the heat gun a bit further back so as not to damage the chip. Heat for about 10-20 seconds. Finally, turn off heat gun and let the board cool for about 10-20 minutes or until you can touch it without burning yourself.