David

Not sure why Europe would want a high CTI rated laminate more so than
any other region.

There have been past posts on this subject but the gist of it is that
for circuits carrying high power, the higher the laminate CTI rating the
closer the etch spacings that regulatory agencies permit. I don't
believe this was ever mentioned in past posts but this is the primary
reason for even considering CTI ratings in the first place. Most
situations do not care about laminate CTI rating as the laminate vendors
correctly point out.

Other postings describe the CTI test methodology so I won't go into
that.

As for materials with high enough CTI ratings, most epoxy based
materials have relatively the same CTI ratings. The individual
differences are not significant enough.

Solely from my memory, which fails me every now and then, I remember
that the polyester based materials have higher CTI than epoxies.

I also remember that several years ago, Hitachi offered a laminate that
was made from a copper foil which had a thin ceramic layer blasted onto
the back ( i.e. tooth ) side. This material had phenomenal CTI values
due to the ceramic layer.

Good luck.

/Gerry


-----Original Message-----
From: Bay State Circuits, Inc. [mailto:[log in to unmask]]
Sent: Friday, April 16, 1999 9:47 AM
To: [log in to unmask]
Subject: [TN] Comparative Tracking Index (CTI) on Circuit Board Material


Dear Techntters

I have a customer that is looking for ciruit board material that has a
CTI rating of 400 and one of 600.
Most of the techs from the laminate manufacturers respond with Who cares
about CTI?
It seems my customer is getting this pressure from their customers in
Europe. Can anyone tell me why Europe is concerned with that high a CTI
and can anyone tell me where I can get material with that high a CTI
rating?
I have tried some of the well known manufacturers (Allied, GE, PolyClad)
with no luck.

Thank you
David

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