-----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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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
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