FreeLists / si-list / [SI-LIST] Re: BGA routing

[steve weir <weirsp@xxxxxxxxxx>]

Darshan,

If you are asking about via-in-pad that technology exists.  Like anything 
else it has trade-offs, not the least of which is fabrication cost.  The 
issues that get addressed by people who do this successfully include:  1) 
Preventing the via from becoming a solder wick.  2) Ensuring the via does 
not create a coplanarity problem.  Blind LASER vias tend to address both 
issues rather nicely, but at considerable cost.

If you are interested, speak with your board fabrication and assembly shops 
about their capabilities.

Steve.

At 03:41 AM 11/11/2004 -0800, Darshan Mehta wrote:
>Hi All,
>
>
>
>I have one general question regarding BGA routing. I have seen many BGA 
>boards and nobody puts via exactly below the BGA pad. Most of the times, 
>we generate Fanout outside the BGA pad. Is there is a specific reason for 
>that? I think we can save lot of space if we put via exactly below BGA 
>pad. Is there will be any problem if we put via exactly below the pad of 
>BGA? Thanks.
>
>
>
>Best Regards,
>
>Darshan Mehta
>
>
>
>
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