[SI-LIST] Re: 0.8mm BGA routing
- From: Michael_Greim@xxxxxxxx
- To: leeritchey@xxxxxxxxxxxxx, prasadsa@xxxxxxxxxx,si-list@xxxxxxxxxxxxx
- Date: Tue, 30 Dec 2003 12:32:44 -0600
Using a sequential lamination scheme to implement
your blind vias can eliminate this depth to width
restriction but there are cost impacts to this
approach (process steps, fallout,etc,etc). However,
depending on your need, this may be a way to go.
If enough folks don't know what sequential lamination
blind vias are, I can expound if need be.
best regards,
Michael Greim
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Lee Ritchey
Sent: Tuesday, December 30, 2003 12:13 PM
To: Prasad S A; si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: 0.8mm BGA routing
Laser drilling happens after lamination and before final plating. A laser
drill can drill all the way through a PCB. That is not the limitation on
how far into a PCB one can drill a blind via. The limitation is the
ability to plate copper into deep blind holes. The usual limitation is
hole cannot be deeper than they are in diameter for successful plating.
Many fabricators require the hole diameter to be 1.5 times its depth
Lee.
> [Original Message]
> From: Prasad S A <prasadsa@xxxxxxxxxx>
> To: <si-list@xxxxxxxxxxxxx>
> Date: 12/27/2003 11:53:03 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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