In re Short

This appeal from the decision of the Patent Office Board of Appeals involves the rejection of claims 1-10 in appellant’s patent application1 relating to silver-containing metalizing compositions useful in the production of conductors and capacitor electrodes. The examiner rejected all claims over prior art under 35 USC 103 and the board affirmed.

The application describes a composition said to inhibit migration of deposited silver used as a conductor in many electrical and electronic applications, e.g., printed circuits. It appears, particularly under conditions of high humidity, that silver deposited on a ceramic substrate in closely adjacent conductor paths of different polarity migrates from an anodic conductor (in the form of silver hydroxide.) to a cathodic conductor (where it is deposited as metallic silver). A “bridge” gradually forms between the adjacent conductor paths which results in circuit failure because of a shorting out of the paths. To solve that problem, appellant includes platinum particles and, optionally, palladium particles in his silver composition in what he terms critical proportions, whereby silver migration is prevented or lessened.

The board found that the claimed subject matter would have been obvious to one of ordinary skill in view of Martin2 or Janakirama-*1025Rao3 considered with. Weller 4 or Short.5 Martin discloses a metalizing paint for use in making microcircuits which comprises “the noble metals, i.e. silver, gold, the platinium group metals and mixtures thereof.” Janakirama-Rao discloses an enamel resistance composition containing (1) silver, 'gold or copper in the ionic state, (2) finely divided particles of platinum, palladium or rhodium or mixtures thereof and (3) finely divided particles of other noble metals, such as silver or gold. Weller relates to a method for installing terminal leads in composite electrical components, and states that migration of silver lead material on the ceramic body may be avoided “by alloying, coating, or plating the surface of the lead with a material which inhibits silver migration.” Finally, Short discusses the very problem of silver migration between silver conductors or electrodes printed on dielectric elements which is of concern here, and solves that problem “by interposing on a dielectric between silver conductors of opposite polarity a barrier composed of a precious metal from the group consisting of gold, platinum and palladium.”

The board was on solid ground when it concluded that the claims were unpatentable under § 103:

* * * Short states that a surface coating of Pt or Pd will inhibit migration of silver conductors in a moist atmosphere. Weller says that silver migration can be avoided by alloying, coating or plating the surface of the silver with a material which inhibits silver migration, i.e., the inhibitor may be a surface coating or it may be distributed throughout the body of the silver. In our opinion, it is then obvious to workers of ordinary skill in this art to alloy or mix Pt and/or Pd with a silver conductor, for the purpose of inhibiting migration of silver. Determination of optimum proportions of the three metals is a routine matter, based on relative costs of the metals and degree of inhibition desired.

In our view, the nuances between the claimed subject matter and the prior art are such that appellant’s compositions would surely have been obvious to the person or ordinary skill in the art. The decision is therefore affirmed.