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February 1999

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From:
Jeff Hempton <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Wed, 3 Feb 1999 07:49:28 -0500
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     Hey Charlie,
       Boy, that sounds like fun. Takes me back to my microelectronic days.
     We used .040" thick ceramic for a few projects, and the best method
     for scoring is to have a laser house laser scribe the bare substrate
     before you start processing. There is a science to this, as a bad
     scribe job can introduce microcracks and cause snapping where you
     don't want it, but a good scribe job will make the snapping smooth and
     a real pleasure (I am obviously entertained easily). So choose someone
     who has been scribing ceramic, such as laserage (rep. Larry Woodling
     ph:317-844-7365) or Laser-Precise (talk to Ken Barks, Knoxville,
     Tenn., sorry no phone #). We were processing snapstrates (now you are
     armed with the highly technical term for scribed ceramic multiple-ups,
     grin) at .040" thick in a 3.75" x 4.5" size, I would recommend you not
     go over 6" square. The larger you go, the more difficult it is to get
     flat ceramic.

     As for zone temps, that will require some playing on your part (got
     the KIC auto-prediction software???) but a good rule of thumb is if
     your profiles can be kept to 1.5 deg. c/second or less rise and fall
     times you should be okay. Ceramic is such a good heat sink you will
     need a SLOOOOWWWWW profile in todays standards..........DON'T RUSH IT!
     Feel free to contact me if I can help. Good Luck Charlie!

     Jeff Hempton
     United Technology Electronic Controls
     [log in to unmask]


______________________________ Forward Header __________________________________
Subject: [TN] Ceramic Boards
Author:  "<Charles Barker>" <[log in to unmask]> at Internet
Date:    2/2/99 5:32 PM


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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