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Thousand Dot Per Inch Resistive Ribbon Thermal Print Head

IP.com Disclosure Number: IPCOM000109243D
Original Publication Date: 1992-Aug-01
Included in the Prior Art Database: 2005-Mar-23
Document File: 2 page(s) / 94K

Publishing Venue

IBM

Related People

John, RA: AUTHOR [+2]

Abstract

Disclosed is the process to etch, and fabricate a thermal print head, made from 25 mm thick tungsten and having 1000 electrodes per inch. Each electrode is 16 mm wide and on 25 mm centers.

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Thousand Dot Per Inch Resistive Ribbon Thermal Print Head

       Disclosed is the process to etch, and fabricate a thermal
print head, made from 25 mm thick tungsten and having 1000 electrodes
per inch.  Each electrode is 16 mm wide and on 25 mm centers.

      Wet chemical etching cannot be used to etch the fine strucures
required to form the electrodes.  Reactive ion etching (RIE) is the
process of choice.  A masking technique, a RIE process and a potting
process all had to be developed to fabricate the 1000 dot/inch print
head.  The following steps provide the basis for the fabricating
process for the high resolution print head.
      1)  Start with tungsten/KAPTON* lamination.
      2)  Clean the tungsten surface.
      3)  Deposit copper film which acts as a mask for the RIE of the
tungsten.
      4)  Photo lithography to define print head pattern prior to
theetching steps.
      5)  Sputter etch the copper film forming the mask for the RIE
step.
      6)  RIE the tungsten using 90% SF6 and 10% CHCL3.
      7)  Pot the fragile electrodes with a solution of silicone
rubber.
      8)  Mechanically dress the electrode tips to fit the curved
platen of the printer.

      The RIE of the tungsten puts stringent requirements on steps 3
through 5.  Keeping the copper mask thin minimizes the length of time
the photoresist is exposed to the sputter etch process.  The
photoresist film has to be thick enough to withstand both the sputter
etch step and the RIE step.  The gas mixture of SF6 and CHCL3 used to
RIE the tungsten was selected because of its high etch rate of the
tungsten.  This gas mixture has an etch rate of 20 mm/hr in the
region between the electrodes, and 25 mm/hr in the open areas of the
print head.  These rates are achieved at a power level of 1w/cm(2).
The use of CHCL3 as an inhibitor gas gives excellent side wall
protection to the narrow e...