Anybody here know about BGA/Reballing stuff?

spleenharvester · 14 Jan 2011 at 19:41

Hey,

Basically I have a mate's laptop, the 8200M chipset needs a reball. Gonna try the heat gun on it first but I doubt it'll hold for long.

There are replacements on ebay for ~£23 with balls pre-attached, could I remove the old chip and heatgun this one onto it?

Cheers

Tefal · 14 Jan 2011 at 19:53

out of curiosity how do you know when they need reballing?

PhillyDee · 14 Jan 2011 at 19:54

Ideally you want it to be temperature controlled.

spleenharvester · 14 Jan 2011 at 19:59

Tefal said:
out of curiosity how do you know when they need reballing?

One/more of the solder joints in the chip give out, and you get sporadic problems like no boot/no post/graphics failure depending on the chip that's died.

PhillyDee said:
Ideally you want it to be temperature controlled.

Hmm, only has two heat settings - 300*c and 600*c, a guy on youtube with the same heatgun said to use it on low on the back for 40 seconds then high on the frontside of the chip about a fists' length from the board for roughly the same amount of time. Could this be an issue?

PhillyDee · 14 Jan 2011 at 20:00

As long as it tops out at 300 degrees, that should be ok. If you get the datasheet for the chip, it should tell you the maximum temperature and length of time required to solder them.

Tefal · 14 Jan 2011 at 20:02

spleenharvester said:
One/more of the solder joints in the chip give out, and you get sporadic problems like no boot/no post/graphics failure depending on the chip that's died.

How do you narrow it down to the right chip?

even then how can you tell?

neodude · 14 Jan 2011 at 20:10

It won't need reballing. The balls on a BGA, contrary to popular belief, are not actually made from solder, they are tin. The balls themselves do not reflow during soldering they are merely there to provide an electrical connection much the same way as the leads on a QFP.

They are soldered the same way as standard SMT components by printing solder paste on to the board and then running through a reflow oven.

Reballing would only be required if the BGA had suffered mechanical damage and some of the balls had become damaged or broken off. More likely that the solder joints connecting the balls to the board have dried or cracked. Best way to remedy is to squirt liquid flux under the BGA and heat with a danotherm/heatgun for about 30 seconds. 300-400 degress should do nice (standard solder reflows at 273), obviously a reflow oven would be the preferred way.

spleenharvester · 14 Jan 2011 at 20:29

neodude said:
It won't need reballing. The balls on a BGA, contrary to popular belief, are not actually made from solder, they are tin. The balls themselves do not reflow during soldering they are merely there to provide an electrical connection much the same way as the leads on a QFP.

They are soldered the same way as standard SMT components by printing solder paste on to the board and then running through a reflow oven.

Reballing would only be required if the BGA had suffered mechanical damage and some of the balls had become damaged or broken off. More likely that the solder joints connecting the balls to the board have dried or cracked. Best way to remedy is to squirt liquid flux under the BGA and heat with a danotherm/heatgun for about 30 seconds. 300-400 degress should do nice (standard solder reflows at 273), obviously a reflow oven would be the preferred way.

Great, thanks for the information

That was the plan I was going for, was just about to ask about the flux as I'm not sure. Does it evaporate with heat or do I have to mop it up myself to stop it shorting connections?

PhillyDee said:
As long as it tops out at 300 degrees, that should be ok. If you get the datasheet for the chip, it should tell you the maximum temperature and length of time required to solder them.

Didn't think of that, cheers

the chip already had a slight... erm... chip on the one corner so I'm being extremely careful not to make it any worse.

Tefal said:
How do you narrow it down to the right chip?

even then how can you tell?

Pressing on the chip will briefly reconnect the damaged joint. I tracked this laptop down to the 8200M chipset as pressing on its heatsink made the laptop boot up fine and work for a few hours before dying.

PhillyDee · 14 Jan 2011 at 20:31

As long as you use a flux meant for SMT work, usually its no-clean. I think all fluxes are non conductive (Just covering myself there

).

neodude · 14 Jan 2011 at 20:33

Yep. no-clean flux. You can get it in a pen format, like a felt tip. Just dab loads around the edge of the chip and let it run underneath. It does leave a residue, but it is electrically insulating.

spleenharvester · 14 Jan 2011 at 21:13

Okay, cheers, I bought some from this guy that did them for YLOD fixes so I presume it'll be fine.

Oh yeah speaking of the edges of the chip, there's some sort of black epoxy, not much of it, but would that need to be removed? I can't get it off :S

neodude · 14 Jan 2011 at 22:23

Yeah, you won't be able to get that off. It's probably sealing the chip all the way around. If you can't get in with the flux just try heating it without. tbh I would suspect a fault on the board itself rather than the chip, have you tried reflowing the decoupling caps? (they will probably be mounted on the opposite side of the board directly under the BGA).