Guenter, I believe the material (non woven) is Thermount which is a Dupont
trademark. Several U.S. prepreg manufacturers are currently producing the
material (Nelco and Arlon to name names). There are several options for this
material with regards to thickness and resin type but I would recommend that
you contact a material supplier directly rather than through DuPont. DuPont
sells the non woven fabric and not the finished laminate material.

I would be interested in your reliability testing and we could compare
notes. We are in the process of reliability assessment of this type of
material due to customer insistance of using this type of laminate.

Hope this Helps... HAPPY NEW YEAR

regards

Dave Rooke

Circo Craft - Pointe Claire



>Hi Bob
>
>I can't give you any advice concerning the scale factors for PCB's with
>woven Kevlar. But we made a lot of investigation about the reliability of
>SMT solder joints on this type of material.
>Be careful !! A PCB with Kevlar can have an anisotropic CTE. The Kevlar is
>not always symmetrically woven ( depends on the distributor ). This means
>there are not the same amount of Kevlar strings in both weaving directions.
>As a result, we observed a stunning crack growth rate in the solder joints
>of ceramic components that are in the direction with just a few strings. on
>the other hand, components with plastic packages show fast growing cracks
>in the solder joints if set in the direction with many strings. I got
>really angry reactions from DuPond when I published this results. The folks
>these explained me that no woven Kevlar is used anymore in PCB's ( due to
>the problems explained in my report ) but a fleece with an irregular
>distribution of the Keflar strings leading to a less pronounced anisotropy
>in the CTE ( hopefully ). However, DuPond never gave us examples of this
>material for testing when I offered them the possibility of performing a
>series of reliability tests. So I can't tell you anything about this
>material. Anyway, it seems as if woven material is still used.
>
>Guenter
>
>Federal Institute of Technology
>Reliability Laboratory
>Zurich
>Switzerland

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