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High Temperature Coating for Fiducial Protection

IP.com Disclosure Number: IPCOM000108099D
Original Publication Date: 1992-Apr-01
Included in the Prior Art Database: 2005-Mar-22
Document File: 1 page(s) / 54K

Publishing Venue

IBM

Related People

Gall, T: AUTHOR [+3]

Abstract

Fiducial marks and alignment slots built into PTFE (polytetrafluoroethylene) composite circuit panels have to be protected from damage in subsequent circuit manufacturing processes. The fiducial marks and slots are used for alignment operations many times during panel manufacturing, and have to have the polymer cleared away from them so that they can be located accurately. Covering the fiducials and slots with tape leaves a glue residue on the panel, and is not very effective during etching, and causes problems in the plating and plasma operations. The slots are often damaged when the tape is removed.

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High Temperature Coating for Fiducial Protection

       Fiducial marks and alignment slots built into PTFE
(polytetrafluoroethylene) composite circuit panels have to be
protected from damage in subsequent circuit manufacturing processes.
The fiducial marks and slots are used for alignment operations many
times during panel manufacturing, and have to have the polymer
cleared away from them so that they can be located accurately.
Covering the fiducials and slots with tape leaves a glue residue on
the panel, and is not very effective during etching, and causes
problems in the plating and plasma operations.  The slots are often
damaged when the tape is removed.

      Most polymers will degrade at the high temperatures used for
processing PTFE panels, and the porous nature of the filled PTFE
dielectric tends to absorb polymers and solvents.  If the absorbed
material decomposes at high temperatures it will cause blisters
during lamination. Until now there have not been any polymers that
could be used to coat the fiducials and slots.  Teflon AF* is a
fluoropolymer which is stable at temperatures up to 360~C and can be
dissolved in perfluoro alkane solvents such as FC77** and so can be
used as a paint to coat the fiducials and slots of a high temperature
circuit board.  The figure shows a schematic of a coated fiducial.
The coating is applied at room temperature and air dried for one
hour. After drying, the coating protects the features from process
chemical exposure....