In Ex parte Zhang (Appeal No. 2021-005022), the Patent Trial and Appeal Board (“Board”) rejected an Examiner’s finding of obviousness that was premised on an unappreciated ratio being a result-effective variable.
The independent claim on appeal read:
1. A sinterable conductive composition comprising:
a metal component having an average particle diameter of greater than about 150 nm to about 100 μm…;
a sintering agent; and
an emulsion comprising water, and
at least one particulate polymer having an average particle diameter
wherein a ratio of average metal component particle diameter to average particulate polymer particle diameter is between 1:1 and 10:1.
The Examiner rejected claim 1 over a primary reference that disclosed a metal component having an overlapping average particle diameter and a secondary reference disclosing metal particles, a sintering promoter, and an emulsion containing resin fine particles. Equating “fine particles” with nano-sized particles, the Examiner found the claimed ratio obvious (i.e., using the overlapping metal component diameter from the primary reference and the nano-sized particulate polymer diameter from the secondary reference).
In the alternative, the Examiner argued it would have been obvious to optimize the “fine particle” size to sufficiently disperse the polymer particles in the emulsion.
The Board rejected both of the Examiner’s positions. The Board first emphasized that claim 1 required a specific ratio particle size of the metal component and the polymer particle, and “not merely a size range for the polymer particle.” The primary reference did not disclose a particulate polymer so it could not possibly recognize a relationship between the metal component and the polymer particle.
As for the secondary reference, the diameter of the polymer relied on by the Examiner was for a precursor – not the final product – and nowhere did it suggest a relationship between the polymer particle size and metal particle size.
In the Board’s own words:
Missing from the record is any evidence of an interdependent relationship between the diameter sizes of the metal component and the polymer particle. In addition, nothing in the combined references suggests or recognizes that the claimed ratio relationship is a result effective variable.
We cannot accept general conclusions about what is ‘basic knowledge’ or ‘common sense’ as a replacement for documentary evidence for core factual findings in a determination of patentability.
Takeaway: Sometimes patentability resides in a relationship between properties that are seemingly obvious when considered individually. As shown in In re Zhang, when a reference relied on by the Examiner is missing the claimed property, it cannot possibly recognize a relationship involving that property. And even where a reference has the individual properties needed to arrive at the claimed relationship, the relationship will not obvious unless there is an overlap or a recognition of an interdependent relationship between the properties involved in the relationship.
Judges: C. Timm, D. Dennett, M. Cashion, Jr.