Mark,

I believe the material was FR4 with various Tgs.
Bev Christian at: [log in to unmask]  is the chairman of this committee.

You can contact him for more info (it has become very complicated!).

David A. Douthit
Manager
LoCan LLC

Mark Mazzoli wrote:

>  Thanks for the info David.  I wasn't aware that CAF could form in
> that short amount of time.  We've made numerous attempts to locate the
> actual shorts but they don't show themselves.  Clearly, if we could
> find one it would make decision making much easier.Thermount is billed
> as an anti CAF material due to the randomness of the fiber.  Since it
> does not contain woven strands for channeling CAF, some believe it to
> be resistant to that effect.  Our concern is its enthusiasm for water
> absorption.  I can see how the absence of fiber "channels" would
> inhibit filament growth but it seems like the accelerated water
> absorption would create a fine growing environment for conductive
> incubation.Are you aware of the materials used in the IPC testing?
>
>      -----Original Message-----
>      From: David Douthit [mailto:[log in to unmask]]
>      Sent: Friday, December 20, 2002 8:58 AM
>      To: TechNet E-Mail Forum.; Mark Mazzoli
>      Subject: Re: [TN] Thermount for Burn In boards
>
>      Mark,
>
>      Some round robin testing being done by the IPC committee on
>      CAF indicates that there is a "damage" ring around drilled
>      holes/vias of up to .020 inches.
>      CAF will form there very quickly (hours!) in high >80%
>      humidity and mild temperatures (>5 degrees C and < 45
>      degrees C).
>      This damage area would most likely include edge routing and
>      scoring.
>
>      You need to do some cross section work ups before you start
>      "guessing"!
>
>      David A. Douthit
>      Manager
>      LoCan LLC
>
>      Mark Mazzoli wrote:
>
>     >
>     >
>     > For those of you designing or building burn in boards, are
>     > any of you building them on Thermount material?  One of
>     > our customers has shown an interest in this material for
>     > their burn in boards and we're trying to decide if that's
>     > a wise move or not.  Most of their boards use 0.8mm and
>     > 0.5mm BGA's and have traditionally been built on
>     > Polyimide.  The problem is that some percentage of them
>     > develop low voltage shorts in the field.  Hole to internal
>     > traces may be as low as 3 mils when drill wander and
>     > material movement are at their worst but normally it's
>     > maintained at 6-mils or better.  The boards are tested at
>     > 40 volts prior to shipping and all pass but some number of
>     > them will develop the field problem.  CAF is suspected but
>     > I'm not so sure.  The field failures develop in days or
>     > weeks rather than months.  I suspect rather than CAF it
>     > may be due to the resin system itself.  I understand that
>     > most Poly manufacturers use a common Poly resin from Ciba
>     > and that it has been suspected of developing this low
>     > voltage shorting issue (sulfur content I believe).
>     >
>     > Anyone out there have any comments about the situation
>     > itself or comments regarding Thermount (85RT and 55ST)?
>     >
>     > Thanks,
>     >
>     > Mark Mazzoli
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