[SI-LIST] Re: 4 Layer card with blind & buried via's

  • From: Tayyab Rahimkhan Pathan <Tayyab_Pathan@xxxxxxxxxxx>
  • To: "sunil_bharadwaz@xxxxxxxxx" <sunil_bharadwaz@xxxxxxxxx>
  • Date: Tue, 4 Dec 2012 06:35:47 +0000

Use of Break out board which adapts WLCSP to any other easy to fab interconnect 
is possible?
Regards,
Tayyab

-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On 
Behalf Of sunil bharadwaz
Sent: Tuesday, December 04, 2012 11:57 AM
To: b.hargin@xxxxxxxxxx; Wolfgang.Maichen@xxxxxxxxxxxx; si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: 4 Layer card with blind & buried via's

Thanks to all who have replied to this mail .I cannot get away from using this 
particular chip ( 0.4 mm pitch & 0.25 mm bump dia ) . In fact this is a WLCSP & 
not a BGA . I guess the package name does not make any difference to the escape 
out .
We cannot even use a 6 mil / 10 mil Via for the escape out ( because there is 
not enough space with this aggressive ball pitch ) . Definitely struck with

Via on Pad & the HDI technology .


Even with the increase in no of Layers , we may ( rather will ) not be able to 
avoid the blink & buried Vias ( not Via's - thanks for the correction ).
I do not think , conventional technology would not work ..


Regards
Sunil.B



________________________________
 From: Bill Hargin (ICD) <b.hargin@xxxxxxxxxx>
To: Wolfgang.Maichen@xxxxxxxxxxxx; sunil_bharadwaz@xxxxxxxxx; 
si-list@xxxxxxxxxxxxx 
Sent: Monday, December 3, 2012 11:01 PM
Subject: [SI-LIST] Re: 4 Layer card with blind & buried via's
 
Hi Sunil:

<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 ?>

You can use a blind via from L1-L3 ... Wolfgang is correct, though I'll add
this:   buried vias would perhaps cost enough more to fabricate than going
with a 6-Layer design -- not to mention other issues that may come up if you
try to sqeeze too much into the two resulting signal layers.

We have a tool that helps with stackup tradeoffs ... There's an eval version
on http://www.icd.com.au/FX.html .

Bill Hargin
In-Circuit Design, USA
Software & SI Simulation for High-Speed PCB Design
(425) 301-4425 • b.hargin@xxxxxxxxxx • Skype: bill.hargin
Online:  www.icd.com.au 


-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
Behalf Of Wolfgang.Maichen@xxxxxxxxxxxx
Sent: Monday, December 03, 2012 6:37 AM
To: sunil_bharadwaz@xxxxxxxxx; si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: 4 Layer card with blind & buried via's

My guess is that adding blind vias to the design will cost way more than
going from 4 to 6 layers...

Regards,  Wolfgang

-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
Behalf Of sunil bharadwaz
Sent: Monday, December 03, 2012 3:22 PM
To: SI LIST
Subject: [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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