[SI-LIST] Re: PC board materials
- From: "David Hoover" <dhoovy@xxxxxxxxxxxxx>
- To: <amp46@xxxxxxxxxxx>, "'SI Newsgroup'" <si-list@xxxxxxxxxxxxx>
- Date: Tue, 18 Nov 2003 18:03:43 -0800
Anand,
There are many things to consider when selecting a material for
a PCB. Some driving factors can be: Thermal resistance,
Low Er, Low loss, thermoset or thermoplastic (like flex circuits),
assembly requirements (like gold plating for chip and wire
connections or lead-free processing),...etc. The cost between
these materials can vary greatly, not to mention supplier availability.
With FR-4 as a baseline you can see as high as 10X or greater
for some exotic materials (such as PTFE based).
The best material selection cross reference guide I have seen so far
is at: http://www.datacircuits.com/pages/eng_mat.html
I strongly suggest you discuss your products specifications with
your fabricator to see if they can supply the proper material
applicable to your requirements.
Regards,
David Hoover
----- Original Message -----
From: "Anand Mohan Pappu" <amp46@xxxxxxxxxxx>
To: "'SI Newsgroup'" <si-list@xxxxxxxxxxxxx>
Sent: Tuesday, November 18, 2003 2:57 PM
Subject: [SI-LIST] PC board materials
> Hi,
> Could someone tell me the difference between different board materials
> (like FR4 and TMM3)? Is the only difference the permittivity (Er) of the
> board material or is there anything else?
> Or in other words, what does a better printed circuit board constitute?
> Is it just that lower permittivity leads to lower capacitive coupling
> between different traces? Or is there more to it in the frequency domain
> - are the rise times of signals somehow affected by the traces of the
> new (better) board? Does the resistance of the traces play a role?
>
> *ANY* light on the issue will be gratefully appreciated.
>
> Anand
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