Susan,

Sanmina does claim a patent on laminates with thinner dielectrics and licenses that technology to various laminate manufacturers. Here is a link to the Sanmina information about thin dielectric laminates. You will see that some of them are FR4 at .002" and .001" thicknesses. There are modified FR4s available that are thinner than that.

http://www.sanmina.com/Solutions/pdfs/Buried_Capacitance.pdf

Regards,
Glenn 

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----- Original Message ----- 
From: "Susan Mansilla" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Friday, July 23, 2004 1:43 PM
Subject: [DC] Dielectric limits


> This is the question I sent before - we really need your input so that what 
> we put into the board specifications is correct.  Please respond
> 
> Good Morning
> In the current rigid board spec 6012A and in 6012B, soon to be released, 
> there is a note in the Dielectric Thickness para that states: "Minimum dielectric 
> spacing may be specificed to be 30 um (0.00118"); however, low profile copper 
> foils should be used and the voltages employed should be taken into 
> consideration so as not to cause breakdown between layers....When the nominal 
> dielectric thickness on the drawing is less than 90 um (0.0035"), the minimum 
> dielectric spacing is 30 um (0.00118").
> 
> I have had advice from some that the thinner dielectric is for "special" 
> materials and not the routine epoxy and polyimide materials typically used.
> 
> Where is there guidance as to what materials can be taken down to 1 mil 
> between layers?
> 
> Thanks for any help you can provide.
> 
> Susan Mansilla
> Robisan Lab
> 
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