Hi Joe,
Only one corner has a slight warp downward. I had
bridging at three corner, so I am not sure how much
did the warpage contribute to the bridging. There is
soldermask damage on the board, but not at the
location where bridgings occured. As I mentioned
before, the same board with the same chip going
through reflow oven has no bridging. To avoid out
gasing, I had the board and chip baked before doing
the rework, and it didn't seem to help at all.
I agree. Without paste, the standoff height is lower.
Since the unit that I am working on is for R&D only,
I am not worried about long term reliability.
Ted
--- "Macko, Joe @ IEC" <[log in to unmask]> wrote:
> Ted,
>
> Is the package warping slightly and the corners
> turning downward? Is the
> solder mask damaged at the corners due to the
> cleaning process? Also,
> sometimes I have noticed that BGA replacement using
> a hot air rework station
> results in a lower package stand off distance if
> solder paste is not used
> (and possibly due to the slight downward hot air
> pressure pushing the
> package down).
>
> joe
>
> -----Original Message-----
> From: Ted Kong [mailto:[log in to unmask]]
> Sent: Monday, August 11, 2003 2:54 PM
> To: [log in to unmask]
> Subject: [TN] BGA bridging on corner pins only
>
>
> Hi All at Technet Land,
>
> Can someone explan why do I see bridgings only on
> the
> corner pins during rework? The package is a 1517
> Pin
> BGA and the rework was done on the SRT rework
> station
> with only flux (No paste). When I run the same
> board
> and component through the reflow oven, I see no
> bridging. I tried lower the air flow and increase
> the
> spacing between the board and the chimney, but
> neither
> helped. Any input is greatly appreciated.
>
> Thanks all in advance.
>
> Ted Kong
>
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