PTAB

IPR2018-01301

Nitto Denko Corp v. Hutchinson Technology Inc

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Petition
petition

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 discloses a printed circuit trace assembly for a hard disk drive head suspension. The technology aims to control the common mode and differential mode impedance of electrical traces by forming apertures and electrically isolated conductive islands within a conductive support layer positioned beneath the traces.

3. Grounds for Unpatentability

Ground 1: Anticipation of Claims 3-4 and 8-9 by Jurgenson

  • Prior Art Relied Upon: Jurgenson (Patent 5,808,834).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Jurgenson discloses every structural element of the challenged apparatus claims. Jurgenson describes an integrated electrical trace interconnect for a head suspension assembly fabricated from a laminate of at least three layers: a lower metal spring support layer, an intermediate insulating layer, and an upper layer of conductive traces. Critically, Petitioner asserted that Jurgenson’s figures show this lower support layer includes large apertures that contain multiple electrically isolated conductive islands, also made of steel, directly beneath the path of the electrical traces. This structure, Petitioner contended, meets all the structural limitations of independent claims 3 and 8, which require a trace assembly with a conductive ground plane layer having at least one aperture containing a conductive island. Dependent claims 4 and 9, which require a plurality of apertures and islands, were also alleged to be fully disclosed in Jurgenson’s figures.
    • Key Aspects: A central part of Petitioner’s argument was that the functional language in the claims, such as “for controlling the common mode impedance,” is a non-limiting statement of purpose that does not add a structural limitation to the apparatus claims. Petitioner argued that even if the language were considered limiting, Jurgenson’s disclosed structure of apertures and islands below parallel traces would inherently control the characteristic, common mode, and differential mode impedance of those traces, thus satisfying the limitation.

Ground 2: Obviousness of Claims 3-4 and 7-9 over Williams and Bennin

  • Prior Art Relied Upon: Williams (WO 98/14937) and Bennin (Patent 5,839,193).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Williams teaches a trace assembly for a head suspension with the same three-layer structure as the ’385 patent. Williams explicitly teaches creating openings, windows, or voids in the lower conductive layer for the express purpose of controlling the impedance of the overlying traces. However, Williams does not explicitly disclose placing conductive islands within these voids. Bennin was introduced to supply this missing element. Bennin discloses a similar laminate structure for head suspension assemblies and teaches using a plurality of small, electrically isolated conductive islands in the lower support layer to "give support and lateral stiffness to otherwise unsupported spans of traces" that cross over open areas.
    • Motivation to Combine: Petitioner contended a person of ordinary skill in the art (POSITA) would combine Bennin’s teachings with Williams’s design for predictable reasons. Williams’s design, which creates long voids under the traces to control impedance, results in unsupported spans of traces susceptible to mechanical instability. Bennin directly addresses this known problem by teaching the use of conductive islands for mechanical reinforcement. A POSITA would therefore have been motivated to incorporate Bennin's support islands into Williams’s impedance-controlling voids to improve the mechanical performance and robustness of the assembly while maintaining the desired electrical characteristics. The shared technical field and manufacturing methods (e.g., etching) of both references would have further prompted this combination.
    • Expectation of Success: A POSITA would have had a high expectation of success. The combination involved applying a known solution (Bennin's support islands) to a known problem (unsupported traces in Williams's design) to achieve the predictable benefits of improved mechanical stability. Williams already teaches tailoring the geometry of the ground plane openings to achieve desired impedance, and a POSITA would have understood how to incorporate the islands and adjust the surrounding void geometry to maintain the desired impedance control.

4. Key Claim Construction Positions

  • "Controlling...Impedance" / "Resulting in a Desired...Impedance": Petitioner argued that these phrases, found in the preambles and bodies of the independent claims, do not impose a separate limitation on the claimed apparatus. Citing federal circuit precedent, Petitioner asserted that statements of intended use or purpose in an apparatus claim are generally not limiting unless they impart a specific structural difference. Petitioner contended the claims recite a specific structure (a trace assembly with apertures and islands in a conductive layer) and that this structure inherently performs the function of affecting or "controlling" impedance. Therefore, the language merely states the intended purpose of the recited structure and does not require any specific degree of control or resulting impedance value that is not already inherent in the physical structure disclosed by the prior art. This construction was critical to the anticipation argument, as Jurgenson discloses the structure without explicitly stating this purpose.

5. Relief Requested

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