PTAB

IPR2018-01301

Nitto Denko Corp. v. Hutchinson Technology Incorporated

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1. Case Identification

2. Patent Overview

  • Title: Apparatus and Method for Controlling Common Mode Impedance in Disk Drive Head Suspensions
  • Brief Description: The ’385 patent relates to a printed circuit electrical trace assembly for a hard disk drive head suspension. The invention purports to control common mode and differential impedance by forming specific patterns of apertures and electrically isolated conductive islands within the lower conductive ground plane layer, which is positioned beneath the electrical traces.

3. Grounds for Unpatentability

Ground 1: Anticipation - Claims 3-4 and 8-9 are anticipated by Jurgenson under 35 U.S.C. §102.

  • Prior Art Relied Upon: Jurgenson (Patent 5,808,834).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Jurgenson, which was not considered during the original prosecution, discloses every structural element of the challenged claims. Jurgenson described an integrated electrical trace interconnect for a head suspension assembly fabricated from a three-layer laminate: a lower metal spring material layer (ground plane), an intermediate insulating layer, and an upper layer of electrical traces. Critically, Petitioner asserted that Jurgenson’s figures depict this ground plane layer as having large apertures that contain multiple, smaller, electrically isolated conductive islands made of the same steel material, with the traces passing over both the apertures and the islands.
    • Key Aspects: The core of this argument rested on the claim construction position that functional language in the apparatus claims, such as "for controlling the common mode impedance," is a non-limiting statement of purpose. Petitioner contended this language describes the inherent result of the claimed structure but adds no patentable weight. Therefore, because Jurgenson disclosed an identical structure, it anticipated the claims. Alternatively, Petitioner argued that even if the language were limiting, Jurgenson's structure of apertures and islands below the traces would inherently and necessarily control the trace impedance, thus satisfying the limitation.

Ground 2: Obviousness - Claims 3-4 and 7-9 are obvious over Williams in view of Bennin under 35 U.S.C. §103.

  • Prior Art Relied Upon: Williams (WO 98/14937) and Bennin (Patent 5,839,193).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner asserted that Williams teaches a head suspension assembly with a nearly identical three-layer structure and expressly discloses creating openings or "voids" in the lower steel ground plane directly beneath the traces for the specific purpose of controlling impedance. Williams, however, does not explicitly disclose placing conductive islands within these voids, which leaves long spans of traces unsupported. To supply this missing element, Petitioner turned to Bennin, which addresses mechanical performance in similar head suspension assemblies. Bennin taught using a plurality of small, electrically isolated conductive "support islands" in the lower steel layer to provide mechanical support and lateral stiffness for traces spanning open gaps.
    • Motivation to Combine: A Person of Ordinary Skill in the Art (POSITA) would have been motivated to combine the teachings of Williams and Bennin. Williams taught creating voids to achieve a desired electrical performance (impedance control) but created a potential mechanical problem (unsupported traces). Bennin taught a solution to this exact mechanical problem using conductive islands. A POSITA would combine Bennin’s islands with Williams’s voids to gain the impedance control benefits of Williams while simultaneously improving the mechanical support and structural integrity of the assembly, a known trade-off in the art. Williams itself noted the objective of balancing electrical performance with mechanical performance.
    • Expectation of Success: A POSITA would have had a reasonable expectation of success in making this combination. Both references are from the same technical field of disk drive head suspensions, use similar laminate structures, and address interrelated problems of electrical and mechanical performance. Applying Bennin's support islands into the voids of Williams was presented as a predictable design choice, not an inventive leap.

4. Key Claim Construction Positions

  • Petitioner dedicated significant argument to the construction of functional language in the apparatus claims (3, 7, and 8).
  • For terms such as "controlling the common mode impedance," "resulting in a desired differential mode impedance," and "resulting in a desired common mode impedance," Petitioner argued they should be treated as non-limiting statements of intended use or purpose. The argument was that these phrases describe the function or result of the claimed apparatus but do not impose any additional structural limitations on the apparatus itself. This construction was central to the anticipation argument, as it allowed Petitioner to argue that Jurgenson’s disclosure of the physical structure was sufficient for anticipation, regardless of whether Jurgenson explicitly stated that the structure was for impedance control.

5. Relief Requested

  • Petitioner requested institution of an inter partes review (IPR) and cancellation of claims 3-4 and 7-9 of the ’385 patent as unpatentable.