mr. lomax:

thank you for your comments.  if a single board is unobtainable
or way too pricey, i will do like you say and sandwich two 63mil 
boards onto a core.  i've posted another email on why i'd like
to avoid this.

is the 1-to-3 relationship between via width and via depth the
same for a thruhole pad?  

thanks, miker


-----Original Message-----
From: Abd ul-Rahman Lomax [mailto:[EMAIL PROTECTED]]
Sent: Thursday, December 20, 2001 5:58 PM
To: Protel EDA Forum
Subject: Re: [PEDA] special board requirements ??


At 09:03 AM 12/20/01 -0500, Robison Michael R CNIN wrote:
>i need a 330mil thick board with 70mil taken off of mirrored sections on
>both sides.  i'm thinking a 100mil radius tolerance on the inside of the
>milled corners, and probably +/- 5 or 10 mil on the milled edges.  the
>size of the board is 12"x7".

That's not a printed circuit board, that is a brick.

Because you are far outside standard board production, it may be much more 
cost-effective to make two boards and sandwich them around some board or 
other material in the middle. Vias can be skewers (I've seen this done for 
space-flight boards). If you really want to plate holes through 330 mil of 
board thickness, know that the rule of thumb is that hole plating starts to 
get dicey at about one-third the board thickness. i.e., over 100 mils in 
your case, though the rule of thumb might not apply with such large holes.

The sandwich approach, if the outer boards are standard 062 material, will 
give you close to the 70 mil section removal. This, too, should save on 
processing.

To do the whole thing in PCB material, the inner boards could be, say .125 
board material or other standard size or sizes to make up what you need; to 
save money, I'd have the inner boards have no copper at all, they would 
just be routed board blanks, drilled where necessary for skewers, and I 
would glue the stack together. If the inner boards have copper pads, 
however, skewer wires, when soldered, could hold the stack together.
[EMAIL PROTECTED]
Abdulrahman Lomax
Easthampton, Massachusetts USA

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