Ingemar,

TMM materials are thermoset resin/ceramic filled laminates for
RF/microwave circuit applications. The resin system does have a natural
change of color when exposed to high temperatures (in an oxygen
environment) that does not have an effect on material properties. This
type of color change is also observed on epoxy/glass (FR4), but since
these circuits have soldermask, it is not observed. Rogers has a report
that discusses this subject more in detail, if you would like to receive
a copy please let me know. Thank you.

Art Aguayo, Technical Support Manager
[log in to unmask]
http://www.rogers-corp.com
Rogers Corporation
Microwave Materials Division
602 961-1382, Fax: 602 961-4533

[log in to unmask] wrote:
>
> To knowers of RF-materials.
>
> "Is it acceptable with discoloration of TMM after 1h in +150Celcius? The
> TMM has a thick brass backside. TMM is inert to most normal solvents and
> etchants and Tg is more than 400Celcius. After 1h it has changed from
> Tefon-grey to Budweisser yellow. Someone who is familiar with this?"
>
>                                     Ingemar Hernefjord
>                                  Ericsson Microwave Systems
>
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