[SI-LIST] AW: 4 Layer card with blind & buried via's
- From: "Havermann, Gert" <Gert.Havermann@xxxxxxxxxxx>
- To: "sunil_bharadwaz@xxxxxxxxx" <sunil_bharadwaz@xxxxxxxxx>, "SI LIST" <si-list@xxxxxxxxxxxxx>
- Date: Mon, 3 Dec 2012 14:57:22 +0000
Talk to your PCB vendor to see what he can recommend (in regards to cost and
technology).
Blind vias usually have a 1:1 aspect ratio, which makes them not too useful if
board space is precious (and 0.4mm BGA seems to go into that direction).
Buried vias don't have this limitation, but they (almost always) add impedance
variations to the inner layer due to the additional copper plating process.
Blind vias from 1-3 do work, but think about the aspect ratio first. Connecting
e.g. buried vias 1-2 with other layers doesn't work well, that means it is very
expensive as you have stack multiple blind vias and you have to plug them.
If no Mechanical reasons drive you to less layers, it is most often cheaper to
stick with traditional PCB and add Layer as you need them.
BR
Gert
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-----Ursprüngliche Nachricht-----
Von: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] Im
Auftrag von sunil bharadwaz
Gesendet: Montag, 3. Dezember 2012 15:22
An: SI LIST
Betreff: [SI-LIST] 4 Layer card with blind & buried via's
Hi All ,
I'am trying to do a board for a micro BGA with 0.4 mm pitch & 0.25 mm ball dia.
To cut down the cost , i want to use a 4-layer card instead of a 6-Layer card.
Layer -1 to Layer -2 & Layer -4 to Layer-3 would be blind Via's .
Can i also use a blind via directly from Layer -1 to Layer-3 or do i have to
use a blind Via from Layer-1 to Layer -2 & then have a buried Via from
Layer-2 to Layer-3 ?
Layer 1 & 4 - Signal.
Layer-2 - complete gnd plane.
Layer -3 Vcc & gnd plane.
I'am looking forward to hear the rules followed in designing such boards.
Thanks for all the help in advance !!
Regards
Sunil.B
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