[SI-LIST] Re: Voids in Solder Joints

I have had similar experience with my first board which had BGAs on it.

For testing, JTAG was invaluable. To check connectivity, I used to rattle
each pin hi/low, and measure some place I had access to the signal.
I use proprietary tools running on a proprietary platform (i.e. I have control
over everything outside the chip packages) so I don't know how viable this
would be with other tools.

Also, I discovered that the balls come not at all well soldered to the BGA.
I had a via in the centre of each pad and sometimes the ball would just detach 
from
the BGA and flow through the board to make a bullbe at the bottom ... 
My obvious solution was to fry once the BGA belly (balls) up with some
flux prior to soldering it to the board - this works perfectly well.

Dimiter

--------------------------------------------------------------------
Dimiter Popoff
Transgalactic Instruments, Gourko Str. 25 b, 1000 Sofia, Bulgaria
http://transgalactic.freeyellow.com
Email: tgi@xxxxxx
Phone: 00359/2/9923340



-----Original Message-----
From: Gupta, Deepali [mailto:Deepali.Gupta@xxxxxxxxx]
Sent: Wednesday, September 24, 2003 3:44 PM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Voids in Solder Joints


Hi,

I have been troubleshooting a board related issue. I have a BGA device
soldered on the board which is giving me functional failures. After running
x-rays on the device I found some voids in the solder jointon most of the
solder balls. 

I am not sure what kind of problems arise due to voids. Voids does not mean
that there is an open joint. I have curve traced al the pins and they give
me the correct characeristics so I guess it is making contact. But what
would a void do when passing a signal is what I am not sure about.

If anyone has dealt with similar issue your feedback would be very helpful.

Thanks

Regards,
Deepali


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