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. > > > > ------------------------------------------------------------------ > > 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: > > //www.freelists.org/webpage/si-list > > > > For help: > > si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field > > > > List technical documents are available at: > > http://www.si-list.org > > > > List archives are viewable at: > > //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 > > > > > > ------------------------------------------------------------------ > 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: > //www.freelists.org/webpage/si-list > > For help: > si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field > > List technical documents are available at: > http://www.si-list.org > > List archives are viewable at: > //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 > > ------------------------------------------------------------------ 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: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List technical documents are available at: http://www.si-list.org List archives are viewable at: //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