[SI-LIST] Re: PDS Capacitor Mounting Details for Lowest Inductance?

The question was - has anyone tried plugged vias.

We have used plugged vias in ultra-fine-pitch BGA pads.  The process is 
manpower intensive, hence expensive.  After fab, and before Au/Ni plating, 
conductive silver resin is forced into the via holes.  Once set, the resin 
is burnished, then the board is plated.

This process has served us well; however, as mentioned above, it is 
expensive.  It also would not be suitable for most mil-spec assemblies.  I 
know of no studies concerning reliability of the pad.  Intuition suggests 
that the dissimilar materials bonded together will not do well in the long 
haul where stress and temperature cycling occurs.  We used it to quickly 
solve a problem in a limited, disposable, application.

There is another expensive process that can be used that is more 
stable.  Laser drilling to controlled depth can be used to produce micro 
vias in pads.  The laser is used to create a hole about 4mils diameter from 
the surface pad down one or two layers to a buried pad.  The resulting hole 
is then copper plated to create a blind via connecting the surface pad and 
the buried pad.  When the board is surface plated, the microvia fills in 
and becomes a barely perceptible dimple in the surface pad.

Both of the above are 'exotic' techniques not suited for mass production 
(unless you plan to charge a hefty price for the finished goods).


At 06:46 PM 2/21/03 -0800, you wrote:


>I haven't done it, but my understanding is that some fab houses can plug
>the vias then plate over them. The mounting pad then has the via hidden
>underneath it. This would certainly give the lowest inductance.
>
>see:
>http://www.protoengineering.com/pdf/viaplug.pdf
>
>
>http://www.methode.com/mdc/mdc5.htm
>
>Has anyone tried this?
>
>    -tom
snip

------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field

or to administer your membership from a web page, go to:
http://www.freelists.org/webpage/si-list

For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field

List archives are viewable at:     
                http://www.freelists.org/archives/si-list
or at our remote archives:
                http://groups.yahoo.com/group/si-list/messages 
Old (prior to June 6, 2001) list archives are viewable at:
                http://www.qsl.net/wb6tpu

Other related posts: