I’ll also mention that calculating your maximum trace lengths and max
allowed signal path loss will also help you with deciding if you need to
be concerned about fiber weave trace delay effects in your design. If
your traces are fairly short then there isn’t much trace length for
fiber weave effects to accumulate.
Chuck
---
Chuck Corley
On 2021-06-07 11:36, Chuck Corley wrote:
Hi Ralph,------------------------------------------------------------------
There are quite a few good materials now, I would write you a list of
some of the good ones but I’m not at my desk right now And I don’t want
to slight any of the great manufacturers who make these good materials.
But I can say there are now less expensive materials that are lower
loss
than the one you mentioned.
Before you start shopping for materials though, as a first step you
should probably calculate the actual loss that you are willing to
tolerate for your communication links. Once you know what amount of
loss you can tolerate over the actual worst-case trace lengths your
design will have then that will enable you to choose the right material
at the best cost. For example, If your longest traces were actually
fairly short lengths, then you might be able to use a more lossy and
less expensive PCB material for your design and still meet your signal
loss targets. Many designs have short trace runs and may not need more
expensive low loss materials.
Chuck
---
Chuck Corley
On 2021-06-07 08:48, Ralph Wilson wrote:
It's been a few years since I've worked with any PCB fab house on------------------------------------------------------------------
stackups and materials for
high speed SERDES routing, so I've lost track of what is in vogue and
at
the knee of the curve
in terms of cost/performance. For the current product I'm looking at
we're "only" dealing with
PCIe-Gen 4 (16Gbps). In "the old days" Nelco-13-SI on a 1080/2116
glass
was a reasonably
priced, low loss, reasonably temperature stable, reasonably flat weave
product applicable
to the 2, 4 and 10G channels of the day. What has the industry moved
to
these days?
I fully expect some of yesterdays exotic materials may have become
mainstream and affordable.
What materials and glass weaves are at the knee of the
cost/performance
curve today that
provide a good environment for 16-25Gbps channels?
Thanks!
Ralph Wilson
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