Appeal No. 96-1249
Application 08/270,215
contact point is determined in the same way, i.e., by applying
voltage V across top layer 11 and measuring the voltage VIN OUT
on the bottom layer, which is left floating for this
measurement (Spec. at 6, lines 26-30). When the resistive
transparent layers are formed of indium tin oxide (ITO) or tin
oxide, which are semiconductive ceramic materials, the
electrical contact resistance has been observed to increase
significantly after many cycles of operation (i.e., switch
closures), which can cause problems with switch reliability
(Spec. at 2, lines 2-15).
Referring to Figure 5, appellants solve this problem by
applying a thin noncontinuous palladium film (26, 27) to the
contact surfaces of one or both of ITO layers 22 and 24 (Spec.
at 8, lines 10-17). The palladium films may be in the range
of about 5D to about 70D thick, preferably from about 10D to
about 30D (id.). "At this thickness, the metal film probably
forms islands 27a, as shown in Figs. 6 and 7, rather than a
continuous film. Therefore, sheet resistance is still
controlled by the ITO layers 22, 24." (Spec. at 8, lines 17-
20.) The "about 5D to about 70D" range is recited in
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Last modified: November 3, 2007