[SI-LIST] Re: 0306 Capacitors
- From: "Ken Cantrell" <Ken.Cantrell@xxxxxxxxxxxxxxxx>
- To: <weirsp@xxxxxxxxxx>,"Istvan NOVAK" <istvan.novak@xxxxxxxxxxxxxxxx>,<leeritchey@xxxxxxxxxxxxx>, <Farah.Haddadin@xxxxxxxxx>,"Ken Patterson" <pattken@xxxxxxxxxxxxxxxxxx>, <si-list@xxxxxxxxxxxxx>
- Date: Fri, 12 Mar 2004 08:17:04 -0700
Steve,
Can you clarify something on statement 2:
2) Test each device with an attachment optimized for that particular part,
as was done for this report. For example, the raw ESL of a reverse
geometry 0508 is lower than that of an 0612, however once mounted, the best
attachment practices for an 0612 yield better results than the best
practices.
specifically - "the best attachment practices for an 0612 yield better
results than the best practices." - attachment practices vs best practices -
I'm not clear on what you're saying.
Ken
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of steve weir
Sent: Thursday, March 11, 2004 7:55 PM
To: Istvan NOVAK; leeritchey@xxxxxxxxxxxxx; Farah.Haddadin@xxxxxxxxx;
Ken Patterson; si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: 0306 Capacitors
Istvan, your point on capacitance in a given package versus inductance is
very important. It is a fact that you have often repeated, and is readily
demonstrated.
I did not test array capacitors because they do not perform as well as IDC
caps and are still a bit pricey even if they are cheaper than IDCs. I can
run those result, but it will not change the economics. Since they do not
perform as well as IDCs, and remain considerably more expensive than X2Ys,
economically they lose to X2Ys.
Given that we have multiple device geometries there are only two ways that
I know of to evaluate the parts:
1) Test each device in an ICM or microstrip type fixture such that only the
raw characteristics of the part are evident. This has been done, but draws
the justified criticism that it is not representative of what happens on a
real board.
2) Test each device with an attachment optimized for that particular part,
as was done for this report. For example, the raw ESL of a reverse
geometry 0508 is lower than that of an 0612, however once mounted, the best
attachment practices for an 0612 yield better results than the best
practices.
For the tests to be meaningful it is imperative that the via pattern for
each device really show the best possible performance. To that end, all
via patterns are off-grid so as to get the vias as close to the pads as
possible. The impact of moving vias away from the pads by even a few mils
can be very dramatic.
I have been careful to try and show each capacitor in the best possible
light. I have another via pattern for the 0612 IDC / array capacitor
types, but it is still out at fab. When the results are back they will be
published along with the rest of the data. The via issues that help with
IDCs / arrays are that they have lots of them, and they are closely
spaced. Lots reduces the attachment inductance, and closely spaced affords
some mutual L to reduce effective mounted inductance. The flip side of
that is that because they are closely spaced, the vias have narrow
diameters. I suspect that if someone were to manufacture a part in a 1014
package where 0.032 vias could be abutted right to each pad, a gain of 4dB
or better versus 0612 could be realized. An ordinary array capacitor in
such a form would then compete for mounted performance with the 0612 IDC on
four / six layer boards, but not on thin substrates.
There is absolutely no point in trying to skew results, as any such attempt
would be easily debunked and it would only serve to damage my reputation.
Yes, the X2Y geometry allows a short loop with fewer vias than array
capacitors, IDC or otherwise. Both geometries are high quality designs
with about 1/4th the raw inductance of a typical 0603 capacitor at 120pH
each. This fact is noted in the presentation. That level of reduction is
not going to come from the pad positions alone as is demonstrated by the
fact that as we go larger in X2Ys with pads further apart the inductance
goes down, not up.
Regards,
Steve
At 09:19 PM 3/11/2004 -0500, Istvan NOVAK wrote:
>Steve,
>
>Eight and 10-terminal capacitors are also available from multiple
>sources, not only from AVX. Also, similar to the IDC parts, there are
>capacitor arrays available in four and eight terminal packages, which offer
>inductances only slightly higher than IDC parts' inductances.
>
>You are correct that even if the capacitance was different, the
>important parameter is inductance. To Lee's point: these measured curves
>dont really show apples to apples comparison, because each via pattern
>is different. However, given the fact that the terminal geometry of these
>capacitors are also different, they cant even have the same via pattern.
>And this could show the strength of the X2Y capacitor in this application.
>The fact that one of the terminals is in the middle of the body, lends
>itself
>very well to via placements with small loop size. While the
>field-cancellation
>mechanism of the X2Y capacitor may be accessible mostly in
>differential connections, when hooked up to planes in single-ended manner,
>the terminal arrangement of the part appears to be its strength.
>
>Regards,
>
>Istvan
>
>
>
>----- Original Message -----
>From: "steve weir" <weirsp@xxxxxxxxxx>
>To: <leeritchey@xxxxxxxxxxxxx>; <Farah.Haddadin@xxxxxxxxx>; "Ken Patterson"
><pattken@xxxxxxxxxxxxxxxxxx>; <si-list@xxxxxxxxxxxxx>
>Sent: Thursday, March 11, 2004 8:18 PM
>Subject: [SI-LIST] Re: 0306 Capacitors
>
>
> > Lee, there is no sleight of hand here. First, a 56nF X2Y is really a
>112nF
> > part. X2Y parts are rated on the circuit one capacitance. A 56nF X2Y
has
> > two 56nF caps in it, so in a circuit two configuration the capacitance
is
> > 112nF. This is easily seen by the fact that the capacitive portion of
the
> > plots line up directly with the 100nF conventional capacitors.
> >
> > Second, inductance is determined by the capacitor body design, not the
> > capacitance. We can take virtually any 0603 capacitor and get the same
> > inductive line. Once we get significantly past the SRF the insertion
loss
> > is equal for all. Similarly for the X2Y, IDC etc. The IDC 0.47 is what
> > was available in stock. The device still demonstrates very good ESL,
but
> > it is impaired by the via pattern. I have a new via pattern that we are
> > testing that should improve it somewhat. Whether the pattern will pull
>the
> > IDC below the X2Y plot or not remains to be seen.
> >
> > These tests show the real behavior with the capacitors attached to a
plane
> > without using a plane so large that the anti-resonant peak interferes
with
> > measurements well beyond 100MHz. The tests correlate to models very,
very
> > well. The predicted performance of capacitors came out within 1dB of
> > models made before the tests were run. If we build a big board, there
is
> > not going to be any change in the relative results. If you disagree
with
> > this, please indicate the science that would support such an idea.
> >
> > X2Y's are licensed to five manufacturers at present. IDC's are an AVX
>only
> > option.
> >
> > No, I fundamentally disagree with your claim about capacitive SRF. What
> > matters is insertion loss. The SRF determines where that loss bottoms
>out,
> > and Q determines how steep the peak inflection is. Significantly above
>the
> > SRF, which will be well below 30MHz for any large capacitance versus
case
> > style we care to choose we will be well past the SRF, and impedance and
> > therefore insertion loss is determined by the mounted ESL. This is a
>point
> > you can find in your own book in the chapters written by John Zasio.
> >
> > If you prefer milliohms it is a simple translation of:
> >
> > 0 dB 25 ohms
> > -20dB 2.5 ohms
> > -40dB 0.25 ohms
> > -60dB 0.025 ohms
> >
> > Again this you will find in your own book. We reported dB because that
is
> > exactly what the tests report.
> >
> > Regards,
> >
> >
> > Steve.
> > At 08:51 AM 3/11/2004 -0800, Lee Ritchey wrote:
> > >Steve,
> > >
> > >Looked at the data from X2Y. Most of the tests use two different
values
>of
> > >capacitor, the value used for the X2Y making it look better. (IDC 470
>nF,
> > >X2Y 56 nF) (0612 100 nF, X2Y 56 nF) I could get the same results with
>the
> > >same skewed tests. Sadly, this is a common problem with vendor
furnished
> > >data. Remember Getek?
> > >
> > >I was really interested in tests you have personally made that
>demonstrate
> > >true A-B comparisons on a PCB that is representative of a real power
> > >subsystem, as we have done. What I mean by that is examine impedance
vs.
> > >frequency for a PCB with enough plane capacitance to support the
>switching
> > >transients seen when driving data buses, etc. When you do that, you
are
> > >going to come to the same conclusions that we did- not worth the extra
> > >resources and not worth forcing your manufacturer to use a single
sourced
> > >part.
> > >
> > > Remember, what counts is the frequency at which the capacitor is
>series
> > >resonant and that is a combination of the value of C and total ESL.
For
> > >all of the examples shown it is less than 30 MHz. Switching harmonics
> > >usually start abouve 100 MHz.
> > >
> > >Final comment on the data is the vertical scale is in db. It would be
of
> > >far greater value if it were in milliohms. Then we could tell more
about
> > >what these capacitors do for us in the power subsystem.
> > >
> > >Lee
> > >
> > >
> > > > [Original Message]
> > > > From: steve weir <weirsp@xxxxxxxxxx>
> > > > To: <leeritchey@xxxxxxxxxxxxx>; <Farah.Haddadin@xxxxxxxxx>; Ken
>Patterson
> > ><pattken@xxxxxxxxxxxxxxxxxx>; <si-list@xxxxxxxxxxxxx>
> > > > Date: 3/10/2004 3:17:18 PM
> > > > Subject: Re: [SI-LIST] Re: 0306 Capacitors
> > > >
> > > > Lee, the file is available on X2Y's web site, but I have attached it
>here
> > > > as well. I spoke with Dave Anthony, dave@xxxxxxx and he will be
happy
>to
> > > > supply you with one of the test boards if you like.
> > > >
> > > >
> > > > Regards,
> > > >
> > > >
> > > > Steve.
> > > > At 01:50 PM 3/10/2004 -0800, Lee Ritchey wrote:
> > > > >Steve,
> > > > >
> > > > >How about sharing the actual test results with us?
> > > > >
> > > > >Lee
> > > > >
> > > > >
> > > > > > [Original Message]
> > > > > > From: steve weir <weirsp@xxxxxxxxxx>
> > > > > > To: <leeritchey@xxxxxxxxxxxxx>; <Farah.Haddadin@xxxxxxxxx>; Ken
> > >Patterson
> > > > ><pattken@xxxxxxxxxxxxxxxxxx>; <si-list@xxxxxxxxxxxxx>
> > > > > > Date: 3/10/2004 10:44:23 AM
> > > > > > Subject: [SI-LIST] Re: 0306 Capacitors
> > > > > >
> > > > > > Lee, It is all in the coefficients. There is no magic here. I
>have
> > >the
> > > > > > data carefully taken at the planes themselves and it does show
> > >dramatic,
> > > > >as
> > > > > > in 3:1 improvement at the planes using X2Y versus 0603. All the
>data
> > >I
> > > > > > have, does in fact correlate well to what you have published.
>While
> > >that
> > > > > > may seem a contradiction, it is not.
> > > > > >
> > > > > > What we are dealing with is a simple 1/( M + N ) equation for
> > >admittance
> > > > > > where M is the ESL of the discrete device and N is the partial
> > >inductance
> > > > > > of the mounting structure and the planes themselves. As I
>suggested a
> > > > > > month or two ago, if we take a graphical view of this to gain
> > >intuition,
> > > > >we
> > > > > > can simply hold M or N constant and plot against the other. It
is
> > >easy
> > > > >to
> > > > > > confirm that if M >> N, then reductions to N offer little help
and
> > > > > > vice-versa. When dealing with ordinary capacitors with ESLs of
> > > > >450-500pH,
> > > > > > that means that reducing the attachment inductance from values
>much
> > >below
> > > > > > 1nH show rapidly diminishing returns. A good two via mount on
a
>four
> > > > > > layer 0.062 board yields total inductance of just about 1200pH.
>Here
> > >the
> > > > > > attachment inductance is not too much bigger than the ESL of the
> > >device,
> > > > > > and as you have experience with, dropping the attachment
>inductance
> > >by a
> > > > > > factor of two only improves the total inductance by less than
1/3
>to
> > > > >about
> > > > > > 850pH, while doubling the number of holes that we have to drill.
>So,
> > >we
> > > > > > are only able to exchange primarily parts placement costs
against
> > >drill
> > > > >holes.
> > > > > >
> > > > > > However, when we take an ESL on the order of 120pH, that picture
> > >changes
> > > > > > completely. Now, the mounting inductance of 700-750pH is very
> > >dominant,
> > > > > > and there are substantial gains to be had by reducing same. So,
>for
> > > > > > example by using a properly designed six via mount for the X2Y,
>the
> > >total
> > > > > > mounted inductance drops to 300-400pH depending on just how
>aggressive
> > > > >you
> > > > > > want to get with the vias. I have test boards you can measure
in
>your
> > > > >own
> > > > > > facilities with repeatable values under 300pH. That is a 75%
> > >reduction
> > > > >in
> > > > > > parts count, and a 25% reduction in total vias to achieve the
same
> > >high
> > > > > > frequency impedance AS SEEN AT THE PLANES.
> > > > > >
> > > > > > Regards,
> > > > > >
> > > > > >
> > > > > > Steve.
> > > > > >
> > > > > >
> > > > > >
> > > > > > At 09:01 AM 3/10/2004 -0800, Lee Ritchey wrote:
> > > > > > >Steve,
> > > > > > >
> > > > > > >I have similar tests that show the inductance reduction and I
>agree.
> > > > >What
> > > > > > >counts is the effect the mounted capacitor has on the impedance
>of
> > >the
> > > > > > >power system. When this test is done, the lowering of the
>overall
> > > > > > >inductance is visible as a shift to a higher frequency of the
>series
> > > > > > >resonance as well as the parallel resonance between the
capacitor
> > > > >parasitic
> > > > > > >inductance and the plane capacitance.. However, in almost all
>cases
> > >this
> > > > > > >shift is not large enough to warrant the extra cost of the vias
>or
> > >the
> > > > >more
> > > > > > >expensive capacitors.
> > > > > > >
> > > > > > >I hate to mention books, but we have published this data. I'll
>post
> > >it
> > > > >on
> > > > > > >my web site. UMR has done similar tests and published the
>results
> > >in the
> > > > > > >IEEE proceedings on EMC.
> > > > > > >
> > > > > > >Lee
> > > > > > >
> > > > > > >
> > > > > > > > [Original Message]
> > > > > > > > From: steve weir <weirsp@xxxxxxxxxx>
> > > > > > > > To: <leeritchey@xxxxxxxxxxxxx>; <Farah.Haddadin@xxxxxxxxx>;
>Ken
> > > > >Patterson
> > > > > > ><pattken@xxxxxxxxxxxxxxxxxx>; <si-list@xxxxxxxxxxxxx>
> > > > > > > > Date: 3/9/2004 10:00:18 AM
> > > > > > > > Subject: RE: [SI-LIST] Re: 0306 Capacitors
> > > > > > > >
> > > > > > > > Lee, I have a whole lot of test data that shows big
>differences
> > > > >between
> > > > > > > > normal 0603's, with 2 and four via patterns as well as
reverse
> > > > >geometry
> > > > > > > > caps versus X2Y's.
> > > > > > > >
> > > > > > > > On a four layer board where the differences will be the
least
>due
> > >to
> > > > >the
> > > > > > > > dominance of via inductance, we go from about 1200pH for an
>0603
> > >with
> > > > > > > > 0.050 spaced side mount via's, one per pad, to 850pH with
four
> > >vias
> > > > > > >total,
> > > > > > > > to under 300pH with X2Y 0603 and a optimized via pattern. A
>4:1
> > > > > > >reduction
> > > > > > > > in parts count saves a lot of money.
> > > > > > > >
> > > > > > > > Nothing is free, the via pattern isn't as friendly as that
> > >convenient
> > > > > > > > 0.050" spacing, but the total number of vias needed in the
>board
> > >to
> > > > >yield
> > > > > > > > an impedance at say 100MHz also comes down considerably
versus
> > >normal
> > > > >or
> > > > > > > > reverse geometry 0603s.
> > > > > > > >
> > > > > > > > Steve.
> > > > > > > >
> > > > > > > > At 09:29 AM 3/9/2004 -0800, Lee Ritchey wrote:
> > > > > > > > >Farah,
> > > > > > > > >
> > > > > > > > >By the time you add in the inductance of the mounting
>inductance
> > >for
> > > > >your
> > > > > > > > >PCB, the lower inductance you get with this uncommon shaped
> > > > >capacitor is
> > > > > > > > >not worth it. Stick with 0603 and use via mounting pads on
>the
> > > > >sides of
> > > > > > > > >the capacitor rather than the end and you get the best
>compromise
> > > > >between
> > > > > > > > >cost, PCB space and performance. Using multiple vias does
> > >reduce the
> > > > > > > > >mounting inductance some, but is not worth the cost in
terms
>of
> > >PCB
> > > > >space
> > > > > > > > >and drilling costs. We've made many controlled tests to
> > >establish
> > > > >this.
> > > > > > > > >
> > > > > > > > >Lee
> > > > > > > > >
> > > > > > > > >
> > > > > > > > > > [Original Message]
> > > > > > > > > > From: steve weir <weirsp@xxxxxxxxxx>
> > > > > > > > > > To: <Farah.Haddadin@xxxxxxxxx>; Ken Patterson
> > > > > > > > ><pattken@xxxxxxxxxxxxxxxxxx>; <si-list@xxxxxxxxxxxxx>
> > > > > > > > > > Date: 3/9/2004 6:27:44 AM
> > > > > > > > > > Subject: [SI-LIST] Re: 0306 Capacitors
> > > > > > > > > >
> > > > > > > > > > Farah,
> > > > > > > > > >
> > > > > > > > > > I believe Murata does make 0306's, but you will get
lower
> > > > >inductance
> > > > > > >at a
> > > > > > > > > > much lower price from an 0603 X2Y. The only caveat is
>that
> > >you
> > > > >are
> > > > > > > > > > presently limited to 200nF in the X2Y, whereas an 0306
in
>X5R
> > >can
> > > > > > >support
> > > > > > > > > > larger values. Unmounted an 0306 is about 190-200pH,
>whereas
> > >an
> > > > >0603
> > > > > > >X2Y
> > > > > > > > > > is about 120pH.
> > > > > > > > > >
> > > > > > > > > > Regards,
> > > > > > > > > >
> > > > > > > > > >
> > > > > > > > > > Steve.
> > > > > > > > > > At 08:16 AM 3/9/2004 -0600, Haddadin, Farah wrote:
> > > > > > > > > >
> > > > > > > > > > >I tried AVX... They don't make 0306 caps, although
their
>data
> > > > >sheets
> > > > > > > > > > >indicate that they do.
> > > > > > > > > > >
> > > > > > > > > > >Thanks,
> > > > > > > > > > >Farah
> > > > > > > > > > >
> > > > > > > > > > >-----Original Message-----
> > > > > > > > > > >From: Ken Patterson
>[mailto:pattken@xxxxxxxxxxxxxxxxxx]=20
> > > > > > > > > > >Sent: Tuesday, March 09, 2004 8:16 AM
> > > > > > > > > > >To: Haddadin, Farah; si-list@xxxxxxxxxxxxx
> > > > > > > > > > >Subject: RE: [SI-LIST] 0306 Capacitors
> > > > > > > > > > >
> > > > > > > > > > >
> > > > > > > > > > >Try AVX. They make a line of reverse aspect caps.
> > > > > > > > > > >
> > > > > > > > > > >Regards,
> > > > > > > > > > >
> > > > > > > > > > >Ken
> > > > > > > > > > >
> > > > > > > > > > >-----Original Message-----
> > > > > > > > > > >From: Haddadin, Farah [mailto:Farah.Haddadin@xxxxxxxxx]
> > > > > > > > > > >Sent: Tuesday, March 09, 2004 9:11 AM
> > > > > > > > > > >To: si-list@xxxxxxxxxxxxx
> > > > > > > > > > >Subject: [SI-LIST] 0306 Capacitors
> > > > > > > > > > >
> > > > > > > > > > >
> > > > > > > > > > >
> > > > > > > > > > >Experts,
> > > > > > > > > > >
> > > > > > > > > > >Does anybody know vendors that can produce 0306 ceramic
> > > > >capacitors?
> > > > > > > > > > >
> > > > > > > > > > >Thanks,
> > > > > > > > > > >Farah
> > > > > > > > > >
> > > > >
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> > > > > > > > > > //www.freelists.org/archives/si-list
> > > > > > > > > > or at our remote archives:
> > > > > > > > > >
>http://groups.yahoo.com/group/si-list/messages
> > > > > > > > > > Old (prior to June 6, 2001) list archives are viewable
at:
> > > > > > > > > > http://www.qsl.net/wb6tpu
> > > > > > > > > >
> > > > > > > >
> > > > > >
> > > > > >
> > > > >
> ------------------------------------------------------------------
> > > > > > To unsubscribe from si-list:
> > > > > > si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject
>field
> > > > > >
> > > > > > or to administer your membership from a web page, go to:
> > > > > > //www.freelists.org/webpage/si-list
> > > > > >
> > > > > > For help:
> > > > > > si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
> > > > > >
> > > > > > List technical documents are available at:
> > > > > > http://www.si-list.org
> > > > > >
> > > > > > List archives are viewable at:
> > > > > > //www.freelists.org/archives/si-list
> > > > > > or at our remote archives:
> > > > > > http://groups.yahoo.com/group/si-list/messages
> > > > > > Old (prior to June 6, 2001) list archives are viewable at:
> > > > > > http://www.qsl.net/wb6tpu
> > > > > >
> > > > >
> > > > >
> > > > >
> > > > >------------------------------------------------------------------
> > > > >To unsubscribe from si-list:
> > > > >si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject
field
> > > > >
> > > > >or to administer your membership from a web page, go to:
> > > > >//www.freelists.org/webpage/si-list
> > > > >
> > > > >For help:
> > > > >si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
> > > > >
> > > > >List technical documents are available at:
> > > > > http://www.si-list.org
> > > > >
> > > > >List archives are viewable at:
> > > > > //www.freelists.org/archives/si-list
> > > > >or at our remote archives:
> > > > > http://groups.yahoo.com/group/si-list/messages
> > > > >Old (prior to June 6, 2001) list archives are viewable at:
> > > > > http://www.qsl.net/wb6tpu
> > > > >
> >
> >
> > ------------------------------------------------------------------
> > To unsubscribe from si-list:
> > si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
> >
> > or to administer your membership from a web page, go to:
> > //www.freelists.org/webpage/si-list
> >
> > For help:
> > si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
> >
> > List technical documents are available at:
> > http://www.si-list.org
> >
> > List archives are viewable at:
> > //www.freelists.org/archives/si-list
> > or at our remote archives:
> > http://groups.yahoo.com/group/si-list/messages
> > Old (prior to June 6, 2001) list archives are viewable at:
> > http://www.qsl.net/wb6tpu
> >
> >
------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
or to administer your membership from a web page, go to:
//www.freelists.org/webpage/si-list
For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
List technical documents are available at:
http://www.si-list.org
List archives are viewable at:
//www.freelists.org/archives/si-list
or at our remote archives:
http://groups.yahoo.com/group/si-list/messages
Old (prior to June 6, 2001) list archives are viewable at:
http://www.qsl.net/wb6tpu
------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
or to administer your membership from a web page, go to:
//www.freelists.org/webpage/si-list
For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
List technical documents are available at:
http://www.si-list.org
List archives are viewable at:
//www.freelists.org/archives/si-list
or at our remote archives:
http://groups.yahoo.com/group/si-list/messages
Old (prior to June 6, 2001) list archives are viewable at:
http://www.qsl.net/wb6tpu
Other related posts:
