Charlie,

        Snapping of ceramic parts is one of them things where you never get
     it right, and every one is full of sound advice.  So saying, here is
     my uncertain tentative and definetly dodgy advice.

        The "standard" method for scoring cermic boards is to laser scribe
     'em prior to any assmebly route.  It was standard practice to scribe
     the back face at my old company, never got a good reason why, but I
     guess it looked better. You have not said what the ceramic is, but I
     guess its a benign one like Alumina or AlN, if its something like BeO
     you may have to look for a specific place willing to deal with it.
     25mil stuff is great to snap, and is often laser scribed 30% through
     thickness to give a good result.  As for techniques, I tend to support
     it on either side of the scribe line, with finger nails touching the
     back of the board below the scribe.  After that a simple snap should
     do.  Dont try and snap it like a ceramic wall tile, along the line all
     at the same time or it all goes to hell. start at the edge of the
     board and let the crack propigate across the scribe line.

        There Ive said my bit, now let all the alternatives come and have
     their say, Id be intersted in some of the novel opinions from over the
     pond where the lead roams free and safe.


                Good luck.

     Roger
     Motorola AIEG
     UK


______________________________ Reply Separator _________________________________
Subject: [TN] Ceramic Boards
Author:  "TechNet E-Mail Forum." <[log in to unmask]> at #email
Date:    02/02/99 17:32


We are faced with creating a "hybrid" made with an ASIC on one side and a
custon Ceramic device (abt 0.50" square) on the opposite side.  The ASIC
will be mounted up-side down to the ceramic "interboard." The "hybrid" will
then be attached to an FR-4 board in the conventional manner.

We will be building these in panel form. The ceramic between the two parts
after de-paneling will be .040" thick, and about .6" by .6" square.  There
will be .25" spacing between rows of parts. Each panel will be about 4"
square.

I am lookig for suggestions in a couple of areas:
1. What is the best way of "scoring" the ceramic so things don't get broken
and people don't get hurt when snapping the panels apart.
2. What would be the suggested elevation of temperatures in a seven-zone
oven to compensate for the ceramic as compared to an FR-4 board?

TIA for any input.

Charlie B.

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