Hi David!
Pressing down on the package causes it to pass huh? You're not alone. A while
back, a former Technetter, Earl Moon, ran into exactly this same issue. His
cure was to take a C-clamp and two blocks of wood, and then apply pressure to
the device...everything worked fine then. I might even still have that picture
somewhere. I'm not sure, but I don't think the end customer wants the board
shipped with a C-clamp attached to the board...hehehe.
What he learned, was that there was a problem with the device. I don't want
to name names, but their initials start with a T, and end with a I. What I
remember, he was able to work with the OEM to correct the issue.
In the meantime, I found a good link that talks about BGA warping and how
package design may contribute to the problem. Go to:
http://www.cooksonsemi.com/tech_art/pdfs/Controlling%20Warpage.pdf
Another thing is moisture, do you/have you baked these devices? From what
I've read on Technet and elsewhere, BGA's will tend to have the corners warp
downward when moisture has been absorbed, this explain why the center balls are
open.
From the experiences of others that I remember, what they've run into is
bridging on the corners of the BGA...and that's been eutectic balls...maybe a
lesser degree of moisture induced warpage? Just enough to lift the center balls
up, and not bridge the corners?
I'll admit, I haven't run into this issue yet...as he knocks on wood...
Can you describe the BGA a bit more? How big, contruction, eutectic or high
temp balls?
-Steve Gregory-
Hello,
I have seen an increase in problems with electrical testing and it has been
traced to BGAs.
I have a few questions regarding BGA and processes. I am trying to
understand if the problem is process related (SMT) or do I have a vendor issue with BGA.
Open contact between the ball and the package. This is verified by pressing
onto the package while testing. Pressing the package down causes the board to
pass.
Visual inspection reveals the ball not touching the PCBA. (You may have a
ball in the middle not touching and the balls on each side are)
Question: With on ball in the middle not touching and the balls next to it
are, is this indicative to SMT process issues or BGA package issues?
Question: What type of inspection can be performed on BGAs prior to SMT to
capture Bad BGA?
i. Is the
industry standard 100% or Sample inspection for out going quality inspection?
Question: Is it easy to identify a BGA that has been re-balled and if so how?
Is it customary for distributors to re-ball BGA
What other test or inspections can be performed to capture BGA with open
contacts?
As indicated above, pressing down the package causes the board to pass, how
do I detect micro cracking of the solder joint? And what would cause micro
cracking?
I am lost at this point and am looking for additional suggestions and
assistance in educating me on BGA.
David Harman
---------------------------------------------------
Technet Mail List provided as a free service by IPC using LISTSERV 1.8e
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315
-----------------------------------------------------