As I understand it PCIe4 is running at 16 Gbps, so the comments about PCIe3
don't apply, since it's running at half that speed.
You need to consider the run length, of course, and consider simulating with
different loss tangents to get an idea of what your eyes can survive. FR408HR
isn't a bad material, but with Df~0.010 range, I'd say that it's more suited to
PCIe3 than 4. Without a repeater or pretty short run lengths, I would think
that you're looking at a more expensive material down in the Df~0.0045 range.
Megtron 6 or a Meg6 lookalike might be in order, although you'll be paying for
the lower loss.
You would also need to consider whether you're building in the US or in Asia,
as well. Availability is significantly different when you cross the pond.
P.S. Small caveat to the "NP-175" statement below. (NP=Nanya Plastics.) The
actual product name is "NP-175FM," and I wouldn't use it for PCIe3 or PCIe4, as
its Df is in the neigborhood of 0.0175.
Bill Hargin
Director of North American Sales and Marketing
Nan Ya Copper-Clad Laminates
billh@xxxxxxxxxxxxx ▪ 425-301-4425 ▪ Skype: bill.hargin
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On ;
Behalf Of Chuck Corley
Sent: Tuesday, February 21, 2017 10:31 PM
To: lists@xxxxxxxxxxxxxx
Cc: si-list@xxxxxxxxxxxxx; si-list-bounce@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: common PCB material for routing refclk in PCIe4 designs?
To be a bit more precise, I'd probably group them this way:
Medium speed / lowest cost:
370HR
NP175
Higher speed / moderately lower cost:
N4000-13
FR408HR
As someone else also mentioned, FR408HR would probably be an excellent choice.
Chuck Corley
National Instruments
On 2017-02-21 22:25, Chuck Corley wrote:
Many people who will be implementing PCIe 4.0 will be doing it for PCs
or for markets that want to minimize cost so I would suggest looking
at something on the less expensive end of the spectrum like FR408HR or
370HR or NP175. All 3 of these are moderately lower loss and less
expensive.
Chuck Corley
National Instruments
On 2017-02-21 17:11, Gary Giust wrote:
Hi, I'm designing a test board to evaluate reference clocks for PCIe
4.0 market. The standard calls for a 12" differential 100 Ohm trace,
but I don't think it specifies the PCB material (FR4, Rogers,
Tachyon, Nelco-13, Megtron-6, etc.) to use.
Since I have to pick a material, I'm looking for recommendations
which one would be realistic (although perhaps on the pessimistic
side) for actual PCIe 4 designs. I want to avoid picking a material
that is clearly too high loss, or too low loss, compared to what may
actually be used.
Any recommendations?
Best regards, Gary
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