Re: gEDA-user: Blind and buried vias?

[Bill Gatliff <bgat@xxxxxxxxxxxxxxx>]

Kai-Martin Knaak wrote:
> On Tue, 29 Sep 2009 17:01:23 +0000, Michael Sokolov wrote:
>
>   
>>> I'm told that the OMAP3430's Package-on-Package configuration requires
>>> at least six layers to get all the signals out.  Ugh.
>>>       
>> OK, that explains the need for a lot of layers.  But how does the need
>> for blind/buried vias arise?
>>     
>
> The balls of the BGA occupy most of the real estate available on top 
> layer. If all vias penetrate the hole stack, this occupation maps to all 
> other layers too.
>   

... and then you've covered all the area that would otherwise be 
available to run traces through.  With a blind via, you can drop down to 
the next layer and get a little room to navigate.

I haven't come across a situation that required a buried via, so I can't 
comment on that.  Can't even guess, actually.


b.g.

-- 
Bill Gatliff
bgat@xxxxxxxxxxxxxxx



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