[SI-LIST] Re: PCB Insertion loss prediction
- From: steve weir <weirsi@xxxxxxxxxx>
- To: si-list@xxxxxxxxxxxxx
- Date: Wed, 31 Oct 2012 20:14:41 -0700
Jeff, given that the only two responses were Scott and mine, I am
surprised that you are disappointed with both.
In a fabrication market filled with intense competition it is up to
individual players to keep up with the technology requirements of the
market or get left behind. The task is not simple. Depending on how far
up the frequency range one needs to go, dialing in cost effective
process requires substantial skills, time, effort and serious money. It
represents competitive advantage to OEMs and their partner pcb fab
houses alike. Neither who have invested are likely to hand over that
kind of advantage especially when it is so costly to obtain.
I don't mind that Terry is looking for a solution on the cheap or free.
If one could obtain such a sweet deal, one would be foolish not to take
it. I am troubled that in this day in age, his organization hopes to
address a sophisticated issue before his technical staff has a grip on
the basics. I fail to understand what you find inappropriate about
that concern. I would rather yell at someone headed for a cliff to stop
than smile and wave.
Best Regards,
Steve.
On 10/31/2012 2:33 PM, Loyer, Jeff wrote:
> I'm surprised at the tone of the responses to this posting (but perhaps I
> shouldn't be, unfortunately); I don't see anything untoward in it. I would
> like to provide some context (with some assumptions on my part) for the
> message lest other innocent postings meet with similar fates. I'll also
> (eventually) provide my answer to the question, as I understand it.
>
>
> There is a significant portion (majority?) of the industry which is extremely
> cost constrained. For instance, to them rotating a design 10 degrees is
> impractical, much less 22 or 45 degrees. Thus, they find other
> cost-effective yet effective means of solving problems (such as zig-zag
> routing), even though those don't appear efficient to others to whom cost is
> not an issue.
>
>
>
> There are new pressures being applied to this segment - designers are now not
> only requiring impedance control, but are also insisting on insertion loss
> control. This is a HUGE paradigm shift, very similar to what we encountered
> when traceable impedance control was first introduced. That was a very
> challenging evolution, and this will be also.
>
>
>
> As an example, PCB vendors are now being advised to smooth their copper,
> after years of purposely roughening it for best mechanical integrity. It
> should come as no surprise that this is not a trivial change, considering the
> effort that has gone into ensuring mechanically robust designs.
>
>
>
> Likewise, many other basic assumptions that we've been able to apply for
> years are now being drawn into question, and PCB vendors are looking for help
> to intelligently and cost-effectively explore options - "How much effect does
> rougher copper have on insertion loss?". I believe Terry is highlighting
> the fact that, while there are many tools available for impedance prediction,
> insertion loss modeling is much less accessible. I don't think it is
> inappropriate to ask if there are cost-effective, reliable tools available to
> predict insertion loss based on a proposed stackup.
>
>
>
> Unfortunately, I believe the answer to the question is that there are no
> reliable, cheap (~free) modelers available to predict insertion loss. And,
> the ones that are available require a great deal more knowledge about the
> stackup than impedance modeling does, and that information is not easily
> obtained. There are some of us working with a vendor to test their modeler
> against a variety of stackups and we'll present results at DesignCon. My
> personal goal is not so much to test a specific modeler but to judge how
> effective a modeler can be given information that can reasonably be gleaned
> prior to building with various materials, copper types, etc.
>
>
>
> In the absence of a modeling tool, or in addition to one, I believe empirical
> data is the best predictor of insertion loss. To do this, however, you have
> to build a stackup representing the final design, and it's not clear at this
> point how broadly you can extrapolate those results to other stackups. But,
> I know many material vendors and PCB shops are engaged in similar efforts.
>
>
>
> I think this is very similar to what we went through with impedance control -
> the shops which most quickly were able to predict and control that
> characteristic had an advantage. I think successful PCB vendors will need
> reliable modeling software and empirical data on insertion loss for their
> particular choices of materials, etc. - they will be able to find the most
> cost effective solution.
>
>
>
> Bottom line: I doubt a reliable modeling tool is going to be cheap, but is
> going to be necessary, and you'll want to compare any tool you do purchase
> against empirical data before you trust it.
>
>
>
> I hope this helps,
>
> Jeff Loyer
>
>
>
> -----Original Message-----
>
> From: si-list-bounce@xxxxxxxxxxxxx<mailto:si-list-bounce@xxxxxxxxxxxxx>
> [mailto:si-list-bounce@xxxxxxxxxxxxx]<mailto:[mailto:si-list-bounce@xxxxxxxxxxxxx]>
> On Behalf Of Terry Ho
>
> Sent: Monday, October 29, 2012 5:52 PM
>
> To: si-list@xxxxxxxxxxxxx<mailto:si-list@xxxxxxxxxxxxx>
>
> Subject: [SI-LIST] PCB Insertion loss prediction
>
>
>
> Hello experts,
>
> I'm from PCB house. Recently we have producted some insertion loss test
> boards(16L, SET2DIL coupon, IS415/IT150DA/I-Speed Mid/low loss material with
> RTF copper foil). We found that the multiply core and high resin PP will
> result a lower loss result. It's a trouble to MI engineer. I would like to
> know how to predict the loss base on stackup. Please help to suggest (papers,
> script, free software etc ). Thanks a lot!
>
>
>
> Best regards,
>
> Terry Ho
>
>
>
>
>
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--
Steve Weir
IPBLOX, LLC
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