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From: Clark on 21 Apr 2008 08:13
I have a motherboard which I believe has a bad connection on a chip and
I need to secure it if I can. I can't resolder it so I need another
option. It is a BGA type of chip and I was reading about some type of
epoxy that could be used to hold it down. I notice that the motherboard
already has a couple of chips with a red substance around the edges, so
I am assuming this is what I need to do. Anyone know what type of
material that is and where I might get it?

Thanks,
Clark
From: kony on 21 Apr 2008 09:58
On Mon, 21 Apr 2008 07:13:36 -0500, Clark <who(a)whoknows.com>
wrote:

>I have a motherboard which I believe has a bad connection on a chip and
>I need to secure it if I can. I can't resolder it so I need another
>option.

What makes you think it has a bad connection?

Securing it doesn't seem like an option, it would need
resoldered or whole board replaced.



>It is a BGA type of chip and I was reading about some type of
>epoxy that could be used to hold it down.

BGA is typically redone with a hot air station, if at all
(tricky once the rest of the board is populated with surface
mount parts). It would probably be as likely the whole
board has to be replaced, and if there was a bad solder
process or enough flexure to the board that this chip really
has broken solder joints, it could potentially be a problem
on other joints, other parts as well.

What type of epoxy were you reading about? It would be
easier to link to it, but generally chips are not epoxied
down to make connections, they are only held down with
adhesive to keep a chip where it's supposed to be prior to
the soldering step.



>I notice that the motherboard
>already has a couple of chips with a red substance around the edges, so
>I am assuming this is what I need to do. Anyone know what type of
>material that is and where I might get it?


See above, I don't think the red stuff is any use to you
now, but it is still unclear why you think a hidden BGA
joint must need resoldered. If there is physical evidence
the chip itself has pulled away from the PCB, it may not
even be the solder joint, it may have pulled the traces/pads
of the PCB right up with the chip which is, practically
speaking, not a reasonable repair for under a BGA chip even
if one was skilled at adding/repairing pads and traces.

Maybe I've got the situation wrong, maybe more details, even
a good hi-res. picture posted elsewhere and linked here
might help. Based on what I'm assuming the situation is
from your description, the board probably isn't reasonably
repairable and an RMA ought to be sought if it's under
warranty still, whole board replaced either way. I suppose
if it isn't under warranty and had to be replaced, there's
noting lost if a repair attempt didn't work, though I would
be very cautious about hooking certain good/valuable parts
up to such a motherboard in case of misconnections or
shorting, depending on what part(s) you're talking about.
From: Clark on 21 Apr 2008 10:25
kony wrote:
> On Mon, 21 Apr 2008 07:13:36 -0500, Clark <who(a)whoknows.com>
> wrote:
>
>> I have a motherboard which I believe has a bad connection on a chip and
>> I need to secure it if I can. I can't resolder it so I need another
>> option.
>
> What makes you think it has a bad connection?
>
> Securing it doesn't seem like an option, it would need
> resoldered or whole board replaced.
>
>
>
>> It is a BGA type of chip and I was reading about some type of
>> epoxy that could be used to hold it down.
>
> BGA is typically redone with a hot air station, if at all
> (tricky once the rest of the board is populated with surface
> mount parts). It would probably be as likely the whole
> board has to be replaced, and if there was a bad solder
> process or enough flexure to the board that this chip really
> has broken solder joints, it could potentially be a problem
> on other joints, other parts as well.
>
> What type of epoxy were you reading about? It would be
> easier to link to it, but generally chips are not epoxied
> down to make connections, they are only held down with
> adhesive to keep a chip where it's supposed to be prior to
> the soldering step.
>
>
>
>> I notice that the motherboard
>> already has a couple of chips with a red substance around the edges, so
>> I am assuming this is what I need to do. Anyone know what type of
>> material that is and where I might get it?
>
>
> See above, I don't think the red stuff is any use to you
> now, but it is still unclear why you think a hidden BGA
> joint must need resoldered. If there is physical evidence
> the chip itself has pulled away from the PCB, it may not
> even be the solder joint, it may have pulled the traces/pads
> of the PCB right up with the chip which is, practically
> speaking, not a reasonable repair for under a BGA chip even
> if one was skilled at adding/repairing pads and traces.
>
> Maybe I've got the situation wrong, maybe more details, even
> a good hi-res. picture posted elsewhere and linked here
> might help. Based on what I'm assuming the situation is
> from your description, the board probably isn't reasonably
> repairable and an RMA ought to be sought if it's under
> warranty still, whole board replaced either way. I suppose
> if it isn't under warranty and had to be replaced, there's
> noting lost if a repair attempt didn't work, though I would
> be very cautious about hooking certain good/valuable parts
> up to such a motherboard in case of misconnections or
> shorting, depending on what part(s) you're talking about.

This board is a replacement board from e-bay. I sent it back and the
seller insisted it ran fine for him--so I just basically ate it!

Now, the system just stops when I do something like play music. I have
been testing for the last several days and it seems when I put pressure
on one corner of the chip, the system resumes and works normally. If I
release the pressure, the system stops after a few seconds.

I realize the pressure might be causing a connection somewhere else to
move, so this is not an exact science, but I cannot seem to find another
place on the motherboard that takes less pressure to make it stop.

Also, the keyboard status lights blink on and off and do not respond to
the Caps Lock or Num Lock keys. Since the chip I am looking at is the
keyboard controller, it would seem to confirm my theory.

Anyway, if it is not really practical to glue the chip down and I don't
have a hot air station to resolder, I will have to send it out to have
it repaired. The pressure required to make the contact is so slight, I
was hoping I could do something else.

Thanks,
Clark
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