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Double Sided Via Capping Method in MLC Thick Film Technology

IP.com Disclosure Number: IPCOM000122332D
Original Publication Date: 1991-Nov-01
Included in the Prior Art Database: 2005-Apr-04
Document File: 1 page(s) / 43K

Publishing Venue

IBM

Related People

Aoude, F: AUTHOR [+4]

Abstract

Disclosed is a process for capping vias on both sides of a green sheet, such that screening defects are reduced. With more requirements placed on the layers it becomes more difficult to ensure defect-free vias by utilizing the present screening procedures.

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Double Sided Via Capping Method in MLC Thick Film Technology

      Disclosed is a process for capping vias on both sides of a
green sheet, such that screening defects are reduced.  With more
requirements placed on the layers it becomes more difficult to ensure
defect-free vias by utilizing the present screening procedures.

      The procedure developed for double-sided capping requires
different screening masks than what is normally used.  The screening
mask for the top of punched sheets has etched holes 1.2 times the via
size.  The screening mask for dull side has etched holes 88% the size
of the via.

      First screening step starts on the bottom side of punched
sheet, unlike conventional screening where the top side of the sheet
is screened.  The bottom side is screened with two passes at a
pressure of 80 + or - 3 psi.  The green sheet is left in the
screener for 5 minutes before proceeding to the next step.  The paste
by now will partially diffuse into the sheet and cupping is formed.
To cap the cupped via, screen bottom side again with 50 + or - 3
psi, 1 pass only.  Remove sheet from the screener and place in a
conventional oven to partially dry.  The sheet remains in the oven
for 10 minutes at 75      2 degrees C.

      Next screen the top side of the sheet at 50 + or - 3
psi, for 1 pass.  This will cap top side.  Then the sheet is dried
completely for 30 minutes at 75 + or - 2 degrees C.

      The time used for drying the sheet...