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August 2007

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Subject:
From:
John Burke <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, John Burke <[log in to unmask]>
Date:
Fri, 31 Aug 2007 14:36:03 -0700
Content-Type:
text/plain
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text/plain (131 lines)
I have had to solve this issue on a number of occasions. The way I do it is
to cut a stencil 2 mils thick for the via in pad BGA areas and then stencil
down solder paste with a water soluble flux base and reflow, this acts as
"spackle" and fills up the via in pad.

Then clean the board and  assemble normally.

John

 
 
John Burke
 
(408) 515 4992

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Joe Macko
Sent: Friday, August 31, 2007 9:53 AM
To: [log in to unmask]
Subject: Re: [TN] vOID IN Micro BGA

I will 2nd that. I have experienced a lot of voiding issues when there
are VIPs on uBGAs as well as other BGAs. Often the VIPs are the same
size whether they are located in a uBGA pad or a larger say 25 mil BGA
pad and consequently, its impact is significant. I am trying to get the
design group to always plug and cap all VIPs so this does not become an
issue.

One work around is to use a 2 mil stencil and paste/reflow the side of
the board with this issue prior to populating any side of the board! The
2 mils of paste helps fill the VIPs as long as they are not too big.
Adding an additional reflow to a non-populated board should not be an
issue but needs to be verified.

Good luck,
- Joe

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Vladimir Igoshev
Sent: Friday, August 31, 2007 9:04 AM
To: [log in to unmask]
Subject: Re: [TN] vOID IN Micro BGA

The presence of vias in the pads causes it. Mind, though, that even such
large voids might not affect a long time reliability of the joints.

Regards,

Vladimir

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of shankar rao
Sent: Friday, August 31, 2007 11:49 AM
To: [log in to unmask]
Subject: [TN] vOID IN Micro BGA

Dear All,
   
  We are getting Large voids  in Micro BGA  on someof the pads having
PTH/via  (greater than 40% in dia) after reflow soldering in one of our
multi layer PCB. We are using ROHS paste and ROHS component.  Can I know
what may be the reason for  these voids
   
  Regards
   
  SHANKAR 


K. Shankar Rao
       
---------------------------------
 Unlimited freedom, unlimited storage. Get it now

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