Rework of laptop motherboards

[KEVSPIT]

Hello,

Need some information regarding pre heating/baking of laptop motherboard prior to removing and soldering large BGA chips like GPU and North bridge.

I am aware that the BGA themselves need to be heated for 105 - 110°C for at least 5 hours but need info on how to get rid of moisture from the PCB and therefore avoid and pop corning on the PCB itself.

1. Is it recommended to pre heat the motherboard to remove moisture from the PCB before removing a BGA?
2. If so, what is the recommended temperature and time for preheating/baking?
3. What equipment is required to perform such operation?

Thanks

[hopkok]

Re: Rework of laptop motherboards

1, YES
2, 100-110C for 24 hours, personally use 110C for 6-8 hours and never have any problem
3, I use clasic kitchen owen, preheating 6-8 boards at once (saving electric energy)

[passete]

Re: Rework of laptop motherboards

i never bake the mobo, just lift, clean mobo, clean bga, add new balls and solder it back.
No clean insat flux for lift, tacky flux for new balls and reatach.

[KEVSPIT]

Re: Rework of laptop motherboards

1, YES
2, 100-110C for 24 hours, personally use 110C for 6-8 hours and never have any problem
3, I use clasic kitchen owen, preheating 6-8 boards at once (saving electric energy)

Thanks for the advice. It looks like that I need to invest in a heat chamber.

[KEVSPIT]

Re: Rework of laptop motherboards

i never bake the mobo, just lift, clean mobo, clean bga, add new balls and solder it back.
No clean insat flux for lift, tacky flux for new balls and reatach.

It depends on the humidity level of one's current location. I've already had bad experience with pop corning on the PCBs so in my case preheating and removing moisture is a must.

Thanks

[Sushi1808]

Re: Rework of laptop motherboards

1. YES, absolutely, you don't know the environment and humidity to which these motherboards were exposed, prior to getting to your workshop.
2. I personally use 110C for around 4-5 hours and never have any popcorning or similar issues. I also prebake all new chips at 110C for around 4-5 hours. I wouldn't recommend any higher temperatures because of the sensitivity of some of the components. They can withstand much higher temperatures but only for a few minutes.
3. I also use classic kitchen oven and prebake around 4 boards at once, works great for this purpose. It has around 10C temperature deviation, if I set it to 100C it heats the motherboards to 110C (checked with IR and classic contact temperature meter).

[rookieme]

Re: Rework of laptop motherboards

I never bake boards that where in use during the previous month as they are ok with the temp during their working state.
If any of them is out of use for several months I'll consider baking it for the sake of the bga chip if I'm reworking with reballing, if I'm replacing it I don't care.
The is a rare state that the board could be out of use for some years, then you should bake it because it will go pop corn not only the chipset but the main pcb itself.
I always bake new chips even the 2016+ for 24h at 125C - I 've red that it is the proper temp. After I store them sealed at airtight parts bags.