Re: [SI-LIST] : micro BGA SI vrs PCB consideration

Roland F. Portman (portman@bitmicro.com)
Thu, 14 Oct 1999 12:02:51 -0700

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Ilan,

The problem with microVia (aka laser via) is it is only good from layer 1 to
2.
What do you do about power and ground???

We have been sucessful in using 8mil blind via in pad on a 10 layer board.
The fab house can only use a 8mil drill on a board thickness of 20 mil, thus
we opted for sequential lamination of Layers 1-5, 6-10 to give us the desired
board thickness.

This gives us the ability to get to power, ground and to three signal layers.

Another thing to look into is 10mil drill with 20mil pad thru hole vias in
pad. I don't know
if the 20 mil pads are too big for your microBGA. Our fab house can drill an
0.062" board
with 10 mil drills without much problem.

Good Luck,

Roland

Ilan Adar wrote:

> halloWe run into some problems when using micro BGA.We used PTH vias
> between the micro BGA pads and this leads us to low yield in the
> manufacturing .the PCB people tell us that we must use micro via technology,
> but this requires us to change the PCB stack to :CSSIGSIGGND........can I
> use such a stackup ? or is there a mother solution to micro BGA PCB
> layout.thanks very muchIlan AdarIlan.adar@seabridge.co.iltel
> 972-9-7751239Fax 972-9-7751212

--
Roland F. Portman
BiT Microsystems, Inc.
48499 Milmont Drive
Fremont, CA  94538

(510) 623-2341 Ext 129 (510) 623-2342 Fax (925) 328-7128 Pager

portman@bitmicro.com http://www.bitmicro.com

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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> Ilan,

The problem with microVia (aka laser via) is it is only good from layer 1 to 2.
What do you do about power and ground???

We have been sucessful in using 8mil blind via in pad on a 10 layer board.
The fab house can only use a 8mil drill on a board thickness of 20 mil, thus
we opted for sequential lamination of Layers 1-5, 6-10 to give us the desired
board thickness.

This gives us the ability to get to power, ground and to three signal layers.

Another thing to look into is 10mil drill with 20mil pad thru hole vias in pad. I don't know
if the 20 mil pads are too big for your microBGA.  Our fab house can drill an 0.062" board
with 10 mil drills without much problem.
 

Good Luck,

Roland
 
 

Ilan Adar wrote:

 halloWe run into some problems when using micro BGA.We used PTH vias between the micro BGA pads and this leads us to low yield  in the manufacturing .the PCB people tell us that we must use micro via technology, but this requires us to change the PCB stack to :CSSIGSIGGND........can I use such a stackup ? or is there a mother solution to micro BGA PCB layout.thanks very muchIlan AdarIlan.adar@seabridge.co.iltel         972-9-7751239Fax       972-9-7751212

--
Roland F. Portman
BiT Microsystems, Inc.
48499 Milmont Drive
Fremont, CA  94538

(510) 623-2341 Ext 129
(510) 623-2342 Fax
(925) 328-7128 Pager

portman@bitmicro.com
http://www.bitmicro.com
 

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