[SI-LIST] Re: 0.8mm BGA routing
- From: "Istvan NOVAK" <istvan.novak@xxxxxxxxxxxxxxxx>
- To: <prasadsa@xxxxxxxxxx>, <si-list@xxxxxxxxxxxxx>
- Date: Sat, 27 Dec 2003 11:43:39 -0500
Prasad,
The limitation comes from the plating: drilling itself would be possible
with laser through any number of layers. However, plating a deep
narrow pocket uniformly is not easy, and this poses the limitation
on the aspect ratio. For blind vias, it usually has to stay under
one to one.
This, by the way, all assumes conventional, cheap PCB processes.
With build-up processes or with sequential lamination, this
limitation does not apply in this form.
Regards,
Istvan Novak
SUN Microsystems
----- Original Message -----
From: "Prasad S A" <prasadsa@xxxxxxxxxx>
To: <si-list@xxxxxxxxxxxxx>
Sent: Saturday, December 27, 2003 4:17 AM
Subject: [SI-LIST] Re: 0.8mm BGA routing
> I have a Question on Laser VIA's
>
> I have read through many articles that says Laser VIA cannot pass through
> more than 2 layers.
> Why is this so?
>
> As i understand Fabrication process the drilling happens before plating
and
> stacking of layers.
> what makes it impossible for a Laser Via to end at the 2nd layer.
> or is it that Laser drilling is done after all layers are pressed
together.
>
> Prasad.S.A
>
>
> ----- Original Message -----
> From: "Lee Ritchey" <leeritchey@xxxxxxxxxxxxx>
> To: "Tayyab Jamil" <tayyab@xxxxxxxxxxxxxx>; <si-list@xxxxxxxxxxxxx>
> Sent: Wednesday, December 24, 2003 11:50 PM
> Subject: [SI-LIST] Re: 0.8mm BGA routing
>
>
> > Tayyab,
> >
> > Ther are two possible applications of this pitch part that come to mind.
> > The first is on tiny PCBs that are thin and the second is on multilayer
> > PCBs that are thick. Thin meaning less than 30 mils thick and thick
being
> > above that.
> >
> > For the thin PCBs, it is posible to drill 8 mil holes and plate them
> > successfully. This will allow a 3 mil trace to be routed, one between
> each
> > pin.
> >
> > If you are using this part on a thick PCB, it is not possible to drill
and
> > plate holes and at the same time maintain all of the clearances and
> > tolerances, even with no traces between pins. See my paper "Anatomy of
A
> > Drilled Hole" on my web site, www.speedingedge.com.
> >
> > Yes, there are people who will suggest that it is possible tor have
> through
> > holes and traces with this size package. It is not, when yields and
> > reliability are taken into account.
> >
> > When a .8 mm pitch part is used on a thick PCB, the vias are drilled
with
> a
> > laser and are blind, meaning they reach only to layer 2. Any leads that
> > must reach fartner, will require through holes. These through holes
will
> > need to be "fanned" out from under the part with traces on layer 1.
Then
> a
> > through hole can be drilled with proper clearances and tolerances.
> >
> > Hope this helps.
> >
> > Lee.
> >
> >
> >
> > > [Original Message]
> > > From: Tayyab Jamil <tayyab@xxxxxxxxxxxxxx>
> > > To: <si-list@xxxxxxxxxxxxx>
> > > Date: 12/24/2003 1:50:29 PM
> > > Subject: [SI-LIST] 0.8mm BGA routing
> > >
> > > Hello,
> > >
> > > I am currently working on a design where a 0.8 mm pitch BGA package is
> > used.
> > > Can any one suggest me the design configuration i.e trace width/spce
and
> > > specially the via size and via hole, which i should follow and
> > manufacturers
> > > can handle this.
> > >
> > >
> > >
> > > Regards
> > >
> > > Tayyab Jamil Qureshi
> > > Sr. Design Engineer
> > > CARE Pvt. Ltd.
> > >
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