Hi Jonathan,
Yes, embedding discrete components can be utilized as well. There are
advantage and disadvantages of using embedded discrete components. One of the
disadvantages is that you still have the high inductance of the discrete
component.
Regards, Joel
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On ;
Behalf Of Jonathan Riley
Sent: Thursday, July 21, 2016 2:45 AM
To: sanjeev@xxxxxxxxxxxxxxxxxxxxxxxxxx
Cc: asparky@xxxxxxxxxxxxxxxxxxxxxxxx; Istvan Novak <istvan.novak@xxxxxxxxxxx>;
james.f.peterson@xxxxxxxxxxxxx; si-list@xxxxxxxxxxxxx
Subject: [EXTERNAL] [SI-LIST] Re: embedded capacitance for decoupling
Hi
Getting embedded capacitance by using planes and cores/prepregs is great (and
generally free) but it is not the only way to embed capacitance in a PCB. Some
companies like Wurth can also embed physical components inside the laminate
which the becomes rather thicker than normal. One of the benefits of this is
that you can then use microvias directly on to the capacitors and so remove
some of the problem of the connecting wire inductance. Has anyone got any
measured data on how this approach can help PDN design?
Regards
Jonathan
On 21 July 2016 at 08:02, Sanjeev Gupta <sanjeev@xxxxxxxxxxxxxxxxxxxxxxxxxx>
wrote:
I think the objective of removing the 0.22uF capacitors & intention to
convert them into embedded type is not clear..
if miniaturisation of the overall PCB system is the final goal, there
are plenty of other methods...
regarding embedded caps in the PCB :
1) PCB manufacturer should be consulted about the availability of high
dielectric constant material. Normally they have material of
dielectric constant value ~10 in the stock. other high value
dielectric materials needs to be specially ordered and hence expensive.
2) converting 0.22uF cap into embedded type is not feasible. maximum
attainable value is 20nF/inch^2 using 3M C2006 material.
3) once someone decides to move to embedded type from discrete caps.
existing 0.22uF decap requirement may change to some other cap value.
This requires detailed PDN investigation and evaluate the required
decap number for embedded decap scenario.
Thanks
Sanjeev
On Thu, Jul 21, 2016 at 8:49 AM, Aubrey Sparkman <
asparky@xxxxxxxxxxxxxxxxxxxxxxxx> wrote:
Jim,of
Google "Steve Weir Interra" and you will get some excellent papers
and presentations on the how and why of the power of reducing the
inductance
your PDS.it
Aubrey
Sent from my iPhone
On Jul 20, 2016, at 8:59 PM, Istvan Novakwrote:
<istvan.novak@xxxxxxxxxxx>
Jim,
As usual, there is no single yes or no answer to this question,
because the correct answer depends on many factors.
But contrary to popular belief, my general answer is that yes, it
is possibly in a number of circumstances, maybe in a surprisingly
large percentage of all possible cases, to reduce the number of
discrete capacitors by using embedded capacitance (and below you
will see that
theis really about inductance, not capacitance). If we put aside
several other questions such as cost and focus only on the
electrical performance of the supply rail in question, we first
need to look at
fromexisting design. There are thirty pieces of 0.22uF capacitors,
called Hi-F, which I assume means they are small-size
surface-mount capacitors. Why do we have thirty of them???? For
their capacitance, which, without any DC or AC bias or any other
derating, gives us a mere 6.6uF nominal capacitance? If we need
6.6uF capacitance, we can get it today from a single small-size
ceramic capacitor, we dont need thirty pieces... Assuming that
the starting design is good and the design had thirty pieces for a
good reason, we can quickly convince ourselves that likely the
number of small capacitors is dictated by the total inductance we want to
achieve by them, not by their total capacitance.
Using very simplistic numbers and assuming that the loop
inductance
ofa single 0.22uF capacitor is 1nH, thirty of them will give us 33pH
cumulative inductance, which just happens to be the square
inductance
toa 1-mil (25um) laminate. So all thirty 0.22uF capacitors can be
left out and replaced by a 1-mil laminate. Of course the laminate
capacitance, dependent on its size, will be just a few nF or maybe
up
wea few hundred nFs for large laminates, so we will need to add
capacitance, but likely we can do it with much fewer components,
under some circumstances using just bulk capacitors.
Details of actual situations can vary a lot, and for a careful
design
itneed to look at the whole picture, all constraints and all
requirements. It is true that time-of-flight for available charge
will eventually matter, but this opens up another discussion: time
of flight matters more as the mismatch between PDN components is
increased, and
railmatters less, and eventually it does not matter at all, forstackup replace discrete decoupling capacitors?
matched structures. For largely mismatched structures it is easy
to show that the location of available charge, whether it is from
a laminate or from a capacitor, matters.
Regards,
Istvan Novak
Oracle
On 7/20/2016 2:48 PM, Peterson, James F (Chief Engineers) wrote:
Can the capacitance realized by embedding capacitance in the PCB
Let's say the discrete decoupling solution for a processor's
Vcore
has thirty 0.22 uf Hi-F caps. Is there a practical way to use an
embedded passives approach in the PCB stackup to achieve the needed
decoupling capacitance and thus remove these thirty discrete capacitors?
can't find anything substantial on replacing discrete ceramic
If so, are there any papers published around this? (I've searched
and
capacitors with embedded PCB capacitance.)
Thanks,
Jim Peterson
Honeywell Aero
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