[SI-LIST] Re: PCB STACKUP
- From: Chris Landrum x311 <clandrum@xxxxxxxxx>
- To: 'Vinu Arumugham' <vinu@xxxxxxxxx>,"'Nosovitski, Alexander (Contr)'" <alexander.nosovitski@xxxxxxx>
- Date: Thu, 22 Jan 2004 09:29:15 -0500
I see no advantage...
-----Original Message-----
From: Vinu Arumugham [mailto:vinu@xxxxxxxxx]
Sent: Wednesday, January 21, 2004 5:44 PM
To: 'Nosovitski, Alexander (Contr)'
Cc: clandrum@xxxxxxxxx; 'si-list@xxxxxxxxxxxxx'
Subject: Re: [SI-LIST] Re: PCB STACKUP
What's the advantage (other than layer count) of routing DIFF_SIGNAL
referenced to AGND and POWER_ANALOG instead of using a single stripline
referenced to two GND or AGND planes?
Thanks,
Vinu
Chris Landrum x311 wrote:
Alexander,
I would be inclined to say you do not need the AGND planes. Without knowing
the intricate parts of your design, I would say that tying AGND and GND
together at a backplane will be a BAD idea. With the information at hand, I
would assume you are using the AGND to somehow "benefit" the Gb/s signals.
I would argue, that if this is the case, and you tie the AGND to GND
together at the backplane, you could easily hurt the design especially from
an EMI perspective, as you may induce loop currents.
On another note, tt looks like you have good inner-planar capacitance built
into the design....which is good. I would suggest that you make sure you
have built this capacitance for all the power supplies in your design.
Also, I notice that there are many PWR/GND plane pairs towards the center of
the board. If you intend these structures (the ones toward the middle
layers) to provide inner planar capacitance, I might argue that the
inductance of the vias used to attach the planes may be great enough to
offset the benefit of the inner-planar capacitor. As such, you may be able
to get rid of some of the internal planes to save cost. Now, if you have
current or voltage requirements that require this many planes, then by all
means, what you have designed is correct.
Just my thoughts...for what they are worth.
-----Original Message-----
From: Nosovitski, Alexander (Contr)
[ mailto:alexander.nosovitski@xxxxxxx <mailto:alexander.nosovitski@xxxxxxx>
]
Sent: Wednesday, January 21, 2004 4:44 PM
To: 'Chris Landrum x311'
Subject: RE: [SI-LIST] PCB STACKUP
Hi Chris,
Yes, AGND and GND will be tied together.
I am not sure yet if it is going to be at the backplane or
at the board.
Regards,
Alexander
-----Original Message-----
From: Chris Landrum x311 [ mailto:clandrum@xxxxxxxxx
<mailto:clandrum@xxxxxxxxx> ]
Sent: Wednesday, January 21, 2004 4:18 PM
To: Nosovitski, Alexander (Contr); si-list@xxxxxxxxxxxxx
<mailto:si-list@xxxxxxxxxxxxx>
Subject: RE: [SI-LIST] PCB STACKUP
The first thing that pops out to me is whether or not the AGND and GND
layers will all be tied together. If not, then what is the purpose of the
AGND layers?
-----Original Message-----
From: Nosovitski, Alexander (Contr)
[ mailto:alexander.nosovitski@xxxxxxx <mailto:alexander.nosovitski@xxxxxxx>
]
Sent: Wednesday, January 21, 2004 4:03 PM
To: si-list@xxxxxxxxxxxxx <mailto:si-list@xxxxxxxxxxxxx>
Subject: [SI-LIST] PCB STACKUP
Hello si-list,
The design I am working on has a dense placement.
The proposed stack up looks as follow:
TOP
POWER_ANALOG
DIFF_SIGNAL (Gb/s signals)
AGND
GND
POWER
S
S
GND
POWER
S
S
GND
SPLIT_POWER
GND
S
S
POWER
GND
S
S
GND
AGND
DIFF_SIGNAL_ANALOG (Gb/s signals)
POWER ANALOG
BOTTOM
All signal layers are 0.5 Oz copper and
All planes are solid ( except one in the middle) with 0.5 Oz copper.
The diff. signals are running at 2.5Gb/s.
There are different opinions about analog plane location.
Could the arrangement above cause a problem?
What else should I be concern about?
Any help or suggestion is appreciated!
Regards,
Alexander Nosovitski
-----Original Message-----
From: Salkow, Steven [ mailto:steven.salkow@xxxxxxxx
<mailto:steven.salkow@xxxxxxxx> ]
Sent: Wednesday, January 21, 2004 1:57 PM
To: weirsp@xxxxxxxxxx <mailto:weirsp@xxxxxxxxxx> ; fred@xxxxxxxxxxxxx
<mailto:fred@xxxxxxxxxxxxx> ; kar_thik_v1@xxxxxxxxx
<mailto:kar_thik_v1@xxxxxxxxx>
Cc: si-list@xxxxxxxxxxxxx <mailto:si-list@xxxxxxxxxxxxx>
Subject: [SI-LIST] Re: Looking for thin dielectric tape
4 mil prepreg (pcb laminate) is generally available from anyone doing
multilayer PCB. You may also get samples from laminate vendors (dupont,
Norplex) (sprayed with Scotch 444 adhesive for cold adhesion to copper
foils)
3M (tape division) have exactly what your looking for up to 36" wide
slit to any width but they have minimum qtys
see
http://products3.3m.com/catalog/us/en001/utilities_telecom/oem_electrica
<http://products3.3m.com/catalog/us/en001/utilities_telecom/oem_electrica>
l/node_R5MTBSFVGPbe/root_GST1T4S9TCgv/vroot_GSHBRQT7DVge/gvel_BBGZX3B1QG
gl/theme_us_oemeletrical_3_0/command_AbcPageHandler/output_html
Catalog on the above page for download
Steve Salkow
Lockheed Martin
3200 Zanker Road
San Jose, CA 95134
(408) 473-4058 (san Jose)
(408) 742-4162 (Sunnyvale)
steven.salkow@xxxxxxxx <mailto:steven.salkow@xxxxxxxx>
salkow@xxxxxxxxxxxx <mailto:salkow@xxxxxxxxxxxx>
(925) 462-1075 Home
(925-) 487-5946 Cell
(408) 468-7271 Numeric Pager
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx <mailto:si-list-bounce@xxxxxxxxxxxxx>
[ mailto:si-list-bounce@xxxxxxxxxxxxx <mailto:si-list-bounce@xxxxxxxxxxxxx>
]On Behalf Of steve weir
Sent: Tuesday, January 20, 2004 11:17 PM
To: fred@xxxxxxxxxxxxx <mailto:fred@xxxxxxxxxxxxx> ; kar_thik_v1@xxxxxxxxx
<mailto:kar_thik_v1@xxxxxxxxx>
Cc: si-list@xxxxxxxxxxxxx <mailto:si-list@xxxxxxxxxxxxx>
Subject: [SI-LIST] Re: Looking for thin dielectric tape
If you want to lay out a board, onesy, twosy, Express PCB is not a bad
way
to go. www.expresspcb.com <http://www.expresspcb.com> It sure beats the
Bishop Graphics adhesive
backed Cu tape, or a bathroom full of ferric chloride.
Steve.
At 01:44 PM 1/20/2004 -0800, Fred Townsend wrote:
The last time I check you could still get mylar sheeting at most
drafting and staionary stores. You would to apply your own adhesive.
Comes in 4 and 7 mil thicknesses. You can also get polyester sheeting
frosted one side and adhesive on the other for making labels. Failing
that how about 3M's double sticky magic tape?
Fred Townsend
Karthik V wrote:
Hello,
I am a student at the State University of New York. I am
looking for a double sided sticky dielectric tape (more like a sheet )
of
thickness about 4mils (0.1mm) and with a dielectric constant of
around 4, to use between copper sheets - to make a "temporary board".
I
tried things like epoxy, but it's almost impossible to get it so thin
and
still provide infinite DC resistance.
Could anyone point me to places where I could look for this
kind of stuff. Is there anything else I could try to get the
dielectric
(with Dk around 4) so thin ( apart from elaborate processes ) .
thanks in advance,
Karthik,
---------------------------------
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