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:
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