Hey dude, thanks for sharing the process! 👍
What heat are you using on the cards and is there an advantage in reballing instead of reflowing (adding only flux and hoping for solder connections to reform)?

I'm no expert on this topic, but I understand that non-wetting is caused from oxidation. If there is oxidation on the pad, solder will not stick on if only heated. Purpose of this reballing is to scap off oxidation layers so that solder will stick on the pad with a much higher probability.

I used something like 400+ °C temperature in hot air blower.

Unfortunately, there's a good chance that the chips themselves are fried, but I guess it's a nice project anyway. 😀 Looking forward to seeing the cards working again... hopefully 😀

fool wrote on 2020-10-26, 17:27:

I'm no expert on this topic, but I understand that non-wetting is caused from oxidation. If there is oxidation on the pad, solder will not stick on if only heated. Purpose of this reballing is to scap off oxidation layers so that solder will stick on the pad with a much higher probability.

I used something like 400+ °C temperature in hot air blower.

Ok, thanks for explaining!
I have two cards that I hope I can fix by reflowing so fingers crossed there is no corrosion on their pads!

I don't want to be a party pooper, but if you had heated those BGA chips above 250*C for a prolonged period of time (let alone 400*C !), it can be safely assumed that they are both dead 🙁

Read this doc., melting temperature for leaded alloy is 183*C and for lead free it's 222*C. In general, you should avoid going above 235*C when soldering or reflowing any chip.

Using 400°C air temp to unsolder does not equal heating the part to 400°C though.
It is common to use a heat setting much higher than solder melt temperature to reduce heating time.

Yep, I think he meant 400°C for the heatgun/pen temp not the board or chip temp. By the time the air reaches the chip it's quite a bit cooler.

Preheating to say 100°C+ on the board does help then you can do a quick blast at close range for the chip.
My crude attempt fixed a GF4

Re: Fixing geforce cards

Hoping for successful resurrections 👍

Preheating is important with such repairs. You could try using electric cooking stove (don't put the card directly on top of it, raise it few cm) and a temperature sensor on the board... BGA replacement is kind-of doable with primitive tools when you are dealing with leaded solder (I only reballed memory chip, not GPU), but with lead-free it's very difficult and I failed miserably with that (ended up popcorning the GPU, even though I preheated it).

how do you know its not the memory the issue?

Wow! That's impressive and way way above my pay grade. I really hope you can get those cards working again.

Very nice and clean work so far, nearby SMDs look untouched, hopefully you'll have a good result! And after seeing this I feel encouraged to try my luck with some similar operations 😉

In general, you should avoid going above 235*C when soldering or reflowing any chip.

With that temperature you won't get any BGA's removed, especially aged lead-free things. PCB this size will absorb a lot of heat energy. Actually I can't remember causing IC-damage with excessive temperature, more likely reasons are moisture in PCB->popcorning, and too fast temperature rise. I was a bit amazed there was no popcorning taking into account the time and temperature I had to use. Proper reflow would require right size nozzle and controlled air flow.

Unfortunately, there's a good chance that the chips themselves are fried, but I guess it's a nice project anyway.

Yes, that is very likely as I remelted these once before removing. This is more like a practise event that I have wanted to attempt for a long time.

You could try using electric cooking stove (don't put the card directly on top of it, raise it few cm) and a temperature sensor on the board...

Actually a very good suggestion. I have planned to build one from high power wirewound or PTC resistors.

how do you know its not the memory the issue?

- I dont, I just hope it's not. These memory chips are not BGA chips, so solder faults are easy to find - also not so probable. Finding electrical fault + replacing memory chips does sound very time consuming and frustrating process what I'n not going to perform.

fool wrote on 2020-10-27, 16:33:

how do you know its not the memory the issue?

- I dont, I just hope it's not. These memory chips are not BGA chips, so solder faults are easy to find - also not so probable. Finding electrical fault + replacing memory chips does sound very time consuming and frustrating process what I'n not going to perform.

In my experience a card with bad memory will still "work". Sure, the screen will be full of rubbish and will crash on driver load, but the computer will at least attempt to boot and not beep 2long 3short