[SI-LIST] Re: surface roughness
- From: Scott McMorrow <scott@xxxxxxxxxxxxx>
- To: colin_warwick@xxxxxxxxxxx
- Date: Tue, 22 Nov 2011 16:46:18 -0500
Colin
Not ganging up on you at all. Just ganging up on the fact that the
"Intel/Huray" approach of performing this level of microscopic detailed
modeling is gross overkill. I'd certainly love to see good complex
correlation of both magnitude and phase for the Huray model in a
simulator. But, it's just not necessary, having done hundreds of models
correlated with measurements using the Djordjevic-Sarkar model combined
with the Hammerstadt-Jensen model (or other macroscopic model).
Scott
Scott McMorrow
Teraspeed Consulting Group LLC
121 North River Drive
Narragansett, RI 02882
(401) 284-1827 Business
(401) 284-1840 Fax
http://www.teraspeed.com
Teraspeed® is the registered service mark of
Teraspeed Consulting Group LLC
On 11/22/2011 4:16 PM, colin_warwick@xxxxxxxxxxx wrote:
> Hi Scott, Todd,
>
> Ganging up on me, heh? :-)
>
> To be clear, SEM and AFM data aren't the only way to set the parameters of
> our model. The macroscopic fitting approach you mention works too. And that
> approach does indeed have the advantage that you can let the optimizer tune
> the Svensson-Djordevic dielectric model parameters at the same time. But the
> fact that direct microscopic measurement can be used to set the parameters
> correctly gives us confidence that the model has a physical basis and is
> something more than a polynomial fit.
>
> Best regards,
>
> -- Colin Warwick
>
> Product Manager for High Speed Digital
>
> Agilent EEsof EDA
>
> Blog: http://Signal-Integrity.TM.Agilent.com
>
>
>
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
> Behalf Of Scott McMorrow
> Sent: Monday, November 21, 2011 2:54 PM
> To: si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Re: surface roughness
>
> To pile on. The way I see it, copper surface modeling is not the problem.
> Rather, it is more important to determine how to holistically determine
> and model broadband dielectric constant, loss tangent and copper surface
> roughness, in order to determine a realistic model for PCB structures.
> Given the variability of copper foil and adhesion treatments across vendors
> and fabricators, I find it much more useful to characterize a particular
> dielectric material, foil and fabrication process with measurements. I
> don't care about the microscopic structure of the copper, whether it be
> small or large snowballs or golf balls. What I care about is the
> macroscopic behavior, as Yuriy describes, which can easily be modeled with
> something as simple as the Hammerstad equation for every high performance
> interconnect situation I've ever found.
>
> I've published quite a bit on the process that I use. Probably too much, to
> be frank.` Needless to say, the models I create have extremely low error
> from DC to our maximum measurement bandwidth of 50 GHz thus far. I am able
> to correctly model not only the attenuation behavior of an interconnect,
> but also the phase behavior across the complete broadband spectrum. This
> is necessary to correctly predict all interconnect resonances that will
> impair performance. The models are fully de-embedded and remove all
> measurement artifacts.
>
> We are currently working to extend our method across temperature and
> humidity, with results that are "quite enlightening", and will be
> presenting some of our data at DesignCon this coming year. I've simplified
> the process of Generalized Modal S-Parameter (GMS-Parameter) material
> identification, such that those of us that are not blessed with a
> laboratory with an SEM, and the equipment to determine what the exact
> material composition of the copper snowballs are, can still create scalable
> models that are deadly accurate.
>
> Oh, and at high enough frequencies, copper surface roughness in IC packages
> does make a huge difference, accounting for up to 25% of the loss budget.
>
> best regards,
>
> Scott
>
>>
>> On Mon, Nov 21, 2011 at 7:39 AM, Todd Westerhoff<twesterh@xxxxxxxxxx>wrote:
>>
>>> I'm with Yuriy and Jeff on this one. The physical details of copper
>>> roughness are complex and hard to measure; we can create simulation models
>>> that represent arbitrarily detailed physical features, but we rarely (if
>>> ever) get the measurement data from PCB manufacturers to plug into those
>>> models. What good is a detailed model if we have no data from the
>>> manufacturer to plug into it?
>>>
>>> We've found the process Yuriy describes to be very useful. Starting with
>>> measured data, we adjust the trace roughness factor to correlate to
>>> measured data. The process is incredibly valuable, as we gain great
>>> insight in the characteristics of the same board built by different
>>> suppliers (and even the manufacturing process control within the same fab
>>> run). Once the models are tuned in, automated interconnect extraction and
>>> simulation allows us to validate the behavior of all the links in a high
>>> speed system as a batch simulation process.
>>>
>>> Hope that helps,
>>>
>>> Todd.
>>> --
>>>
>>> Todd Westerhoff
>>> VP, Software Products
>>> SiSoft
>>> 6 Clock Tower Place, Suite 250
>>> Maynard, MA 01754
>>> (978) 461-0449 x24
>>> twesterh@xxxxxxxxxx
>>> www.sisoft.com
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