[SI-LIST] Re: Impedance Controlled Board Production Vs Normal Board Production
- From: "Tom Dagostino" <tom@xxxxxxxxxxxxx>
- To: "'Rajan Hansa'" <all.si.list@xxxxxxxxx>, <si-list@xxxxxxxxxxxxx>
- Date: Fri, 6 Jan 2012 00:44:30 -0800
This is a job for Simulation Man.
One needs to look at the spec for any particular application and determine
through analysis what the tolerance can/should be. There is no rule of
thumb that works.
Tom Dagostino
Teraspeed Labs
9999 SW Wilshire St.
Suite 102
Portland, OR 97225
USA
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tom@xxxxxxxxxxxxx
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Teraspeed Consulting Group LLC
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-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
Behalf Of Rajan Hansa
Sent: Thursday, January 05, 2012 11:46 PM
To: si-list@xxxxxxxxxxxxx
Cc: David Siadat (dsiadat)
Subject: [SI-LIST] Re: Impedance Controlled Board Production Vs Normal Board
Production
guys don't you think that if impedance variation is under 10 % then we
shouldn't worry much about it.
My analogy is that for 10 % impedance variation return loss is more than
-20 db and effect of this return loss is less than 0.5 db on insertion loss
which is quite acceptable when we compare it with losses due to attenuation
on insertion loss.
Correct me if i am wrong or am I missing something ???
On Fri, Jan 6, 2012 at 3:51 AM, David Siadat (dsiadat)
<dsiadat@xxxxxxxxx>wrote:
> I agree with Aubrey's statement.
> If you do not specify Impedance Control design (possibly for each
> layer), then traces on the layer with not enough copper material will
> have more than +/-10% impedance variations even if you specified its
> characteristic impedance in your request!
>
> -David
>
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx
> [mailto:si-list-bounce@xxxxxxxxxxxxx]
> On Behalf Of Aubrey K Sparkman
> Sent: Thursday, January 05, 2012 11:49 AM
> To: Michael Greim
> Cc: Ken Cantrell; Mikhail Matusov; si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Re: Impedance Controlled Board Production Vs Normal
> Board Production
>
> Michael,
>
> A fab house only has to meet the specifications in the contract. I
> would say the company got what they specified.
>
> My point was that an impedance only specification is often inadequate.
>
>
> Aubrey
>
> On 1/5/12 1:16 PM, "Michael Greim" <mgreim001@xxxxxxxxx> wrote:
>
> >There needs to be an interlock between the fab house and design team.
> >If different construction methods are employed and they aren't
> >checked then offending engineer is really getting what they deserve.
> >Check twice, or more, and cut once is a lesson often learned quite
> >painfully.
> >-Michael
> >
> >On Thu, Jan 5, 2012 at 10:27 AM, Aubrey K Sparkman <
> >asparky@xxxxxxxxxxxxxxxxxxxxxxxx> wrote:
> >
> >> Ken,
> >>
> >> What you say is true. What hasn't been mentioned is the risk behind
> >> specifying only the impedance.
> >>
> >> Mikhail makes a good point about specifying the board stackup
> >> CONSTRUCTION. I have seen failures when impedance only was
> specified.
> >> The design went out as a dual stripline with 4 mil cores between
> >>the signals and their respective reference planes and a 12 mil
> >>prepreg between the two signal layers. The pcb house was given
> >>permission to use 5
> mil
> >> cores since they didn't have 4 mil cores in stock. For the 2nd
> build,
> >>the
> >> pcb house outsourced the design to another house which used 8 mil
> cores.
> >> Trace widths and prepreg thickness were adjusted appropriately so
> that
> >> both board thickness and impedance specifications were met.
> >>
> >> Any guesses about the performance of the boards in the 2nd build?
> >>
> >> Aubrey Sparkman
> >> SparkRight Solutions
> >>
> >> On 1/5/12 10:36 AM, "Ken Cantrell" <Ken.Cantrell@xxxxxxxxxxxxxxxx>
> >>wrote:
> >>
> >> >Mikhail,
> >> >I'm not disputing anything that you said, just pointing out that:
> >> >"If I, as a designer, know the process and materials used by the
> >> >particular manufacturer well enough" is a big If. That's a mature
> >> >designer talking. Not something a relative beginner would know or
> >> >even be able to accomplish.
> >> >
> >> >2cents
> >> >Ken
> >> >
> >> > -----Original Message-----
> >> >From: si-list-bounce@xxxxxxxxxxxxx
> >> >[mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Mikhail Matusov
> >> >Sent: Thursday, January 05, 2012 9:05 AM
> >> >To: si-list@xxxxxxxxxxxxx
> >> >Subject: [SI-LIST] Re: Impedance Controlled Board Production Vs
> Normal
> >> >Board Production
> >> >
> >> >
> >> >I don't think those who responded understood the question correctly.
> I
> >> >think
> >> >the OP was asking whether some degree of impedance control can be
> >>achieved
> >> >by precisely specifying the board's stackup, width of the traces,
> and
> >> >process tolerances without explicitly asking the manufacturer to
> >>control
> >> >impedance. For some applications it just boils down to the cost.
> >> >If
> I,
> >>as
> >> >a
> >> >designer, know the process and materials used by the particular
> >> >manufacturer well enough I should be able to specify the board in
> >> >such a way that
> >>the
> >> >impedance will end up in the right ballpark. In fact, I use this
> >>method
> >> >for
> >> >non-critical designs.
> >> >
> >> >=======================
> >> >Mikhail Matusov
> >> >Senior Hardware Design Engineer
> >> >Square Peg Communications
> >> >Tel.: +1 (613) 271-0044 ext.231
> >> >Fax: +1 (613) 271-3007
> >> >http://www.squarepeg.ca
> >> >
> >> >
> >> >
> >> >
> >> >
> >> >
> >> >----- Original Message -----
> >> >From: "Loyer, Jeff" <jeff.loyer@xxxxxxxxx>
> >> >To: <si-list@xxxxxxxxxxxxx>
> >> >Sent: Thursday, January 05, 2012 10:22 AM
> >> >Subject: [SI-LIST] Re: Impedance Controlled Board Production Vs
> Normal
> >> >Board
> >> >Production
> >> >
> >> >
> >> >> Perhaps I'm the only one who is finding it ironic that, on a
> "Signal
> >> >> Integrity" reflector list, "Impedance Controlled" isn't
> >> >> considered "Normal". I haven't had the luxury of not specifying
> >> >> impedance
> >>control
> >> >> since a small 33MHz PCI card design, many years ago.
> >> >>
> >> >> I'm afraid Jayasuryan that you won't find the answer you're
> looking
> >>for
> >> >>on
> >> >> an e-mail thread, or it is going to be a long, drawn out,
> >> >>painful affair.
> >> >> You have a lot of work to do to understand what impedance
> >> >>control
> is
> >>and
> >> >> how it relates to signal integrity. I would recommend starting
> with
> >>the
> >> >> books that have been listed many times on this list. You can
> >> >>also search the archives for "impedance control" to find
> >> >>discussions about
> >>different
> >> >> opinions on how much is enough.
> >> >>
> >> >> Good luck in the new year,
> >> >> Jeff Loyer
> >> >>
> >> >> -----Original Message-----
> >> >> From: si-list-bounce@xxxxxxxxxxxxx
> >>[mailto:si-list-bounce@xxxxxxxxxxxxx
> >> ]
> >> >> On Behalf Of steve weir
> >> >> Sent: Monday, January 02, 2012 6:23 AM
> >> >> To: si-list@xxxxxxxxxxxxx
> >> >> Subject: [SI-LIST] Re: Impedance Controlled Board Production Vs
> >>Normal
> >> >> Board Production
> >> >>
> >> >> Suppose as you like. Hope as you might. What you don't
> >> >> contract
> is
> >>not
> >> >> guaranteed.
> >> >>
> >> >> Steve.
> >> >> On 1/2/2012 5:56 AM, Jayasuryan KG wrote:
> >> >>> Dear Experts,
> >> >>>
> >> >>>
> >> >>>
> >> >>> Happy New Year!!
> >> >>>
> >> >>>
> >> >>>
> >> >>> I have question regarding the impedance controlled board
> production!
> >> >>> Is there any special process to produce impedance controlled
> board
> >> >>>
> >> >>> rather than the normal production?
> >> >>>
> >> >>>
> >> >>>
> >> >>> Suppose if I go with normal production for a impedance
> controlled
> >> >>>board
> >> >>> (the design has been done to meet the impedance) what are the
> >>possible
> >> >>> issues can happen?
> >> >>>
> >> >>>
> >> >>>
> >> >>> Looking for your immediate response. Thanks in advance.
> >> >>>
> >> >>>
> >> >>>
> >> >>> Best Regards,
> >> >>>
> >> >>> - Jayasuryan
> >> >>>
> >> >>>
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> >> >> Steve Weir
> >> >> IPBLOX, LLC
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> >
> >--
> >-Michael.
> >
> >We will either find a way or make one - Hannibal
> >
> >In the middle of every difficulty lies opportunity - Al Einstein
> >
> >If you think you can do something or you think
> >you can't, in both cases you are probably right - H Ford
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> >
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