I've seen solder wick through vias causing bumps on the second side.
Martin
-----Original Message-----
From: Ray Klein [mailto:[log in to unmask]]
Sent: Monday, August 25, 2003 2:55 PM
To: [log in to unmask]
Subject: Re: [TN] FW: BGA question
David,
I'll trow my 2 cents in. In addition to stencil, thickness and other
problems we saw problems with the co-planarity of our PWB's that had HASL
tin/lead on the BGA patterns. We went to imersion silver and gold flash
plating on the bare copper and have had fewer BGA soldering problems. This
may not solve all problems but it's worked for us.
Good Luck
Ray Klein
JNI
-----Original Message-----
From: David Harman [mailto:[log in to unmask]]
Sent: Monday, August 25, 2003 2:05 PM
To: [log in to unmask]
Subject: [TN] FW: BGA question
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.
1. 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.
2. 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)
1. 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?
2. 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?
3. Question: Is it easy to identify a BGA that has been re-balled and
if so how?
4. Is it customary for distributors to re-ball BGA
5. What other test or inspections can be performed to capture BGA with
open contacts?
6. 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
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