Reball advice needed

[reaper57]

Ok, so I have this xbox 360 that failed and I want to swap the gpu. I have already done two reflows, and it looked like someone might have repaired it before me.
I decided to just swap the whole chip instead of reballing, but the thing is that if this works, it's going to be my first successful reball/chip replacement. Every time I tried it before I usually popcorned the gpu while soldering the new balls to it and/or lifted pads on the motherboard and gpu, while cleaning it.
My questions are:
What preheat temprature should I use and how long should I leave the board only on bottom heating?
What temperature should I heat the chip itself to and how long would I need to keep it there?
One of the most important questions are should I start cleaning the motherboard from the old solder right after I lift the chip or should I let it cool down first?
Another important question is what temperature should I set my soldering iron station to and how much time and heat does it normally take to lift a pad on the motherboard?
Thank you to everyone who tries to help me! Any advice is appreciated!

[stj]

Re: Reball advice needed

before you do any of that, know this.
there are a lot of gpu's you need to make sure the new one is the same as the old one.
they kept changing the core voltage among other things - put the wrong part in and either it wont run, or it will burn up.

[reaper57]

Re: Reball advice needed

before you do any of that, know this.
there are a lot of gpu's you need to make sure the new one is the same as the old one.
they kept changing the core voltage among other things - put the wrong part in and either it wont run, or it will burn up.

Thanks for the heads up, but I already got the correct one.

[Agent24]

Re: Reball advice needed

For lead free solder, maximum is about 245C - 260C
For leaded solder, 200C to 235C.

Search google for "BGA Reflow profiles" to get some idea, then just practice and practice until you get it right.

Popcorning is not just caused by too much heat, it can be that you are ramping the heat up too fast, or the chip has absorbed moisture and this trapped moisture expands rapidly during reflow causing the popcorning.

If the chip has been in the normal atmosphere for some time, you may need to heat it for a while at a low temperature to make sure it is dry first before you reflow. Look up MSL http://en.wikipedia.org/wiki/Moisture_sensitivity_level

[reaper57]

Re: Reball advice needed

For lead free solder, maximum is about 245C - 260C
For leaded solder, 200C to 235C.

Search google for "BGA Reflow profiles" to get some idea, then just practice and practice until you get it right.

Popcorning is not just caused by too much heat, it can be that you are ramping the heat up too fast, or the chip has absorbed moisture and this trapped moisture expands rapidly during reflow causing the popcorning.

If the chip has been in the normal atmosphere for some time, you may need to heat it for a while at a low temperature to make sure it is dry first before you reflow. Look up MSL http://en.wikipedia.org/wiki/Moisture_sensitivity_level

Thanks for the advice. So, should I let the mb cool down before I start cleaning the old solder and what temperature should I set my soldering iron to?

[Agent24]

Re: Reball advice needed

I'm not sure, but it may not matter either way, the main thing is to do the cleanup carefully.

A lot of videos show people 'scrubbing' the pads with solder wick. This is a BAD idea.
This is how you should do it: https://www.youtube.com/watch?v=l9eZFo7hQco

When you are skilled and can apply very little pressure to let the wick glide over the pads you may be able to get away with it, but it still carries more risk of lifting pads so it's not a good idea.

This is because when boards are heated, the glue holding the copper to the substrate actually loses about 80% of its strength. Because of this, any physical pressure on the copper can easily break the bond between it and the board substrate. Especially when you are talking about tiny little BGA pads!

[reaper57]

Re: Reball advice needed

Thanks for the advice. I usually mess the pads up while cleaning them with the solder wick. This time I'm planning on setting my iron to 350C or maybe even 400C, and going over the pads carefully, like in the video you sent me.

[xboxhaxorz]

Re: Reball advice needed

This goes into a bit more detail https://www.youtube.com/watch?v=s38vQxXv0GE

If you are using a new chip, simply bake it for say 48 hrs and if you still get popcorn than your profile is the issue