The silence must be deafening... I'm sorry, Susan.

I hear there is ongoing debate over the validity of the copyright for thin
dielectric construction capacitance planes in boards, and the Hadco/Sanmina
patent is really at the center of that controversy. I also know that the
difficulties they have in creating the materials are related to shorts
between the planes through the dielectric.... and the techniques used to
overcome them. That's about the extent of my knowledge on that subject at
this time... although I am interested and would like to learn more about
what is happening there.

This might be a better topic for TechNet and their collection of guru's...
I'm not sure if the DC has any members on that committee. If we do,
hopefully they can expound on this subject more.

Thanks for bringing it to the DC list server. Maybe there will be more
discussion on the subject.

Bill Brooks 
PCB Design Engineer , C.I.D., C.I.I.
Tel: (760)597-1500 Ext 3772 Fax: (760)597-1510
http://pcbwizards.com


-----Original Message-----
From: Susan Mansilla [mailto:[log in to unmask]] 
Sent: Friday, July 23, 2004 10:43 AM
To: [log in to unmask]
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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