Hi Ed,
The thickness of pressed pre-preg depends on a number of factors, (well you
didn't expect it to be simple did you?).
1080 glass itself is 0.0025" thick
2 plies of 1080 pre-preg would press to between 0.005" and 0.006".
If the 1080 is between ground planes it would be thicker than if it was
pressed between tracking layers.

Thickness is determined by the amount of resin flow at board lamination.
Some factors which can affect resin flow are-

Pressure used at bonding        - higher pressure - thinner pre-preg
Heat up rate at bonding                 - slow heat up -less flow - thicker
pre-preg
Gel time of pre-preg            - higher gel - more flow - thinner pre-preg
Melt viscosity of pre-preg      -lower viscosity - more flow - thinner
pre-preg
Board design                     - vent patterns restricting flow - thicker
pre-preg

I guess most laminate manufacturers control their pre-preg in manufacture by
use of gel time and melt viscosity measurements. They also measure resin
flow & resin content.
Thats all I can think off the top of my head, If you've got any specific
questions I'll try and answer.
For the different styles of pre-preg try  www.lamar-uk.co.uk then go into
laminates then pre-pregs, or try the laminate manufacturers web sites, sorry
I haven't got their addresses but try searches for Isola, Nelco, Allied
Signal etc

hope this helps
geoff layhe
www.lamar-uk.co.uk
> ----------
> From:         Brunker Ed[SMTP:[log in to unmask]]
> Reply To:     TechNet E-Mail Forum.;Brunker Ed
> Sent:         10 February 2000 14:46
> To:   [log in to unmask]
> Subject:      [TN] PREPREG AGAIN
>
> Sorry guys,
> I'm still wrestling with this one.
> Can you give me the thickness of 1080 X 2 after pressing.
> Can we work through the reasons for two suppliers giving different results
> for the same prepreg bearing in mind that not all manufacturers are in the
> western world.
> Does the pressing process have much impact on finished thickness?
> Are there any standards with which to control prepreg production?
> Regards
> Edward Brunker
>
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