chip swelling up and getting fried

Hi all,
I am stuck with this problem of a BGA chip getting fried within a
few seconds of powerup.The chip takes in 2 power supplies.1v for core
and a 3v3 for i/o's.There are no overshoots or undershoots that i can
see in the oscilloscopes.
The chip has worked on the same board for sometime but eventually gets
burned out or swelling in the package is seen.I have done the power
sequenceing as per the manufactures requirement but still having major
problems.
I have exhausted all the options i can look into......please help me
start looking for some thing that can lead me to the problem.
Can someone tell me where the likly problem can be?.
The CMOS chip works for a few seconds but goes on getting hot till
the swelling appears and then the chip is dead.It has a plastic
package.The chip has a PCI interface.will the overshoot on the signals
damage the chip so badly?


Regards
DJ

On 14 Jul 2004 04:48:08 -0700, (E-Mail Removed) (DJ) wrote:

>Hi all,
> I am stuck with this problem of a BGA chip getting fried within a
>few seconds of powerup.The chip takes in 2 power supplies.1v for core
>and a 3v3 for i/o's.There are no overshoots or undershoots that i can
>see in the oscilloscopes.
>The chip has worked on the same board for sometime but eventually gets
>burned out or swelling in the package is seen.I have done the power
>sequenceing as per the manufactures requirement but still having major
>problems.
>I have exhausted all the options i can look into......please help me
>start looking for some thing that can lead me to the problem.
>Can someone tell me where the likly problem can be?.
> The CMOS chip works for a few seconds but goes on getting hot till
>the swelling appears and then the chip is dead.It has a plastic
>package.The chip has a PCI interface.will the overshoot on the signals
>damage the chip so badly?
>
>
>Regards
>DJ

Don't use no name chips

--

Boris Mohar

DJ wrote...
>
> I am stuck with this problem of a BGA chip getting fried within a
> few seconds of powerup. ... The CMOS chip works for a few seconds
> but goes on getting hot till the swelling appears ...

Sounds like SCR latchup, wihch once triggered causes a high-current
capable turned-on SCR to appear across the supply rails. If you are
sequencing the power supplies correctly, then you may have an input
that exceeds one of the supplies and is injecting enough current
through the chip's static-protection diodes to initiate SCR latchup.

Thanks,
- Win

(email: use hill_at_rowland-dot-org for now)

"DJ" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed) om...
> Hi all,
> I am stuck with this problem of a BGA chip getting fried within a
> few seconds of powerup.The chip takes in 2 power supplies.1v for core
> and a 3v3 for i/o's.There are no overshoots or undershoots that i can
> see in the oscilloscopes.

Have you bothered to measure the current being drawn by this device? Take a
look at the data sheet and see what the expected power consumed by the
device should be then check to see how much power it is consuming in your
design. Remember, current measurements are made by connecting the DVM in a
serial connection.

What is the device? How many bumps does it have? Double check your
design/layout to ensure that all of the inputs/outputs are correctly pulled
up or pulled down according to the MFG's guidelines.

Is the chip 5 volt tolerant on PCI bus or are you using a 3.3V PCI
(relatively rare). Was chip definitely working?

Clive
"DJ" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed) om...
> Hi all,
> I am stuck with this problem of a BGA chip getting fried within a
> few seconds of powerup.The chip takes in 2 power supplies.1v for core
> and a 3v3 for i/o's.There are no overshoots or undershoots that i can
> see in the oscilloscopes.
> The chip has worked on the same board for sometime but eventually gets
> burned out or swelling in the package is seen.I have done the power
> sequenceing as per the manufactures requirement but still having major
> problems.
> I have exhausted all the options i can look into......please help me
> start looking for some thing that can lead me to the problem.
> Can someone tell me where the likly problem can be?.
> The CMOS chip works for a few seconds but goes on getting hot till
> the swelling appears and then the chip is dead.It has a plastic
> package.The chip has a PCI interface.will the overshoot on the signals
> damage the chip so badly?
>
>
> Regards
> DJ

On 14 Jul 2004 04:48:08 -0700, (E-Mail Removed) (DJ) wrote:

>Hi all,
> I am stuck with this problem of a BGA chip getting fried within a
>few seconds of powerup.The chip takes in 2 power supplies.1v for core
>and a 3v3 for i/o's.There are no overshoots or undershoots that i can
>see in the oscilloscopes.
>The chip has worked on the same board for sometime but eventually gets
>burned out or swelling in the package is seen.I have done the power
>sequenceing as per the manufactures requirement but still having major
>problems.
>I have exhausted all the options i can look into......please help me
>start looking for some thing that can lead me to the problem.
>Can someone tell me where the likly problem can be?.
> The CMOS chip works for a few seconds but goes on getting hot till
>the swelling appears and then the chip is dead.It has a plastic
>package.The chip has a PCI interface.will the overshoot on the signals
>damage the chip so badly?
>
>
>Regards
>DJ

If it's a ram-based FPGA, it could be a weird configuration file. It's
possible to program some of these parts to self-destruct.

Could the PCI bus be pulling the i/o's above 3.3?

John

"DJ" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed) om...
> Hi all,
> I am stuck with this problem of a BGA chip getting fried within a
> few seconds of powerup.The chip takes in 2 power supplies.1v for core
> and a 3v3 for i/o's.There are no overshoots or undershoots that i can
> see in the oscilloscopes.

Check the power sequencing. Does the chip require 3v3 to be up before the
1v?

What about inputs to the chip? Do they appear before the rails are up?
Perhaps you are "latching up" an unprotected input pin (perhaps an analog
I/O pin- they don't always have protection).

Are the clocks running? Some dynamic devices get a bit hot and bothered if
they aren't clocked.

Heatsinks not big enough? With some BGA you need to extract heat through the
PCB as well as from the top of. They need the correct PCB footprint and
weight of copper.

Reset not long enough to allow correct operation? Bit unlikely though.

On Wed, 14 Jul 2004 08:43:21 -0700, John Larkin wrote
(in article <(E-Mail Removed)>):

> If it's a ram-based FPGA, it could be a weird configuration file. It's
> possible to program some of these parts to self-destruct.

Recollection of Motorola's "CFBU" (catch fire and burn up :-) opcode. That
was that in the first 6502's, wasn't it?
--
DaveC
(E-Mail Removed)
This is an invalid return address
Please reply in the news group

On Wed, 14 Jul 2004 12:10:58 -0700, DaveC <(E-Mail Removed)> wrote:

>On Wed, 14 Jul 2004 08:43:21 -0700, John Larkin wrote
>(in article <(E-Mail Removed)>):
>
>> If it's a ram-based FPGA, it could be a weird configuration file. It's
>> possible to program some of these parts to self-destruct.
>
>Recollection of Motorola's "CFBU" (catch fire and burn up :-) opcode. That
>was that in the first 6502's, wasn't it?


S/360 had a bunch of reserved opcodes...

http://listserv.uark.edu/scripts/wa....&F=&S=&P=62319

My favorite is BKO Branch and kill operator


The PDP-11 had the (real) LandMine instruction,

MOV -(PC), -(PC)

which copied itself into all of memory.

John

> S/360 had a bunch of reserved opcodes...

I haven't hunted up details, but two favourites of mine (that were
real instructions) were named:

EBRS: Emit Burnt Resister Smell (on an early computer). Caused a
particular resister to overheat.

HCF: Halt and Catch Fire (caused such a tight loop in microcode that
part of the ucode ROM would melt, think this one was at Intel).

Clifford.