Nitto Denko Corp. v. Hutchinson Technology Incorporated

1. Case Identification

• Case #: IPR2018-00955
• Patent #: 6,965,499
• Filed: May 21, 2018
• Petitioner(s): Nitto Denko Corp.
• Patent Owner(s): Hutchinson Technology Inc.
• Challenged Claims: 1-23 and 25

2. Patent Overview

• Title: Head Suspension Configured for Improved Thermal Performance During Solder Ball Bonding to Head Slider
• Brief Description: The ’499 patent discloses a head suspension for a hard disk drive. The invention addresses the problem of thermal distortion in the suspension's flexible component ("flexure") caused by the heat of solder ball bonding, which connects the head slider to the flexure’s electrical traces. The proposed solution is to form apertures in the flexure’s metal support layer directly beneath cantilevered bonding pads, which allegedly isolates the pads from the rest of the structure and reduces warping.

3. Grounds for Unpatentability

Ground 1: Anticipation of Claims 1, 7-8, 11-12, 14, 19, and 23 by Tsuchiya

• Prior Art Relied Upon: Tsuchiya (Japanese Application # 2001-43647).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner argued that Tsuchiya discloses every limitation of the challenged independent claims (1, 12, 19) and several dependent claims. Tsuchiya describes a hard drive suspension for solder ball bonding that includes a multi-layer flexure with a lower stainless steel layer, an intermediate insulating layer, and upper conductive traces. Critically, Tsuchiya teaches forming "open holes" in its stainless steel layer directly beneath the bonding pads, which "float" or are cantilevered over these holes. Tsuchiya explicitly states this configuration is to absorb distortion caused by compression and temperature changes during solder joining, directly teaching the purported invention of the ’499 patent.

Ground 2: Obviousness of Claims 4 and 17 over Tsuchiya in view of Albrecht

• Prior Art Relied Upon: Tsuchiya (Application # 2001-43647) and Albrecht (Patent 5,821,494).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner asserted Tsuchiya teaches the base suspension structure, as detailed in Ground 1. Claims 4 and 17 add the limitation of a "support structure tongue" formed by U-shaped slits, upon which the bonding pads are located. Petitioner contended this feature is expressly taught by Albrecht, which discloses a stainless steel layer with tongue-like components created by U-shaped apertures to support bonding pads.
  • Motivation to Combine: A Person of Ordinary Skill in the Art (POSITA) would combine these references to solve a known problem. Petitioner argued that while Tsuchiya's fully cantilevered pads address thermal warping, they could be susceptible to alignment issues. Albrecht teaches that its support tongues improve the reliability of the electrical joint by preventing misalignment of solder bumps. A POSITA would have been motivated to add Albrecht’s support tongues to Tsuchiya’s design to gain the benefits of both thermal stability and improved alignment reliability.
  • Expectation of Success: A POSITA would have a reasonable expectation of success because both references address the same technical field (solder-bonded head suspensions) and use similar components. Combining the support structure from Albrecht with the overall design of Tsuchiya was presented as a straightforward application of known design principles to achieve predictable results.

Ground 3: Obviousness of Claims 1-3, 7-16, 19-23, and 25 over Zeng

• Prior Art Relied Upon: Zeng (Patent 6,697,216), in view of the general knowledge of a POSITA.

• Core Argument for this Ground:

  • Prior Art Mapping: Petitioner argued that Zeng, by itself, renders nearly all claims obvious. Zeng discloses a hard drive suspension with a flexure having apertures in its lower layer located directly below cantilevered bonding pads for solder ball bonding. Petitioner contended that even if Zeng does not explicitly state the lower layer is "spring metal" (e.g., stainless steel), a POSITA would have found it obvious to use stainless steel as it was the standard, primary material for this component. Zeng also discloses "serpentine" trace paths adjacent to the bonding region and over an opening, which Petitioner argued meets the "strain relief" limitations of claims 2, 3, 15, and 16.
  • Motivation to Combine (Implicit): The argument centered on what a POSITA would have understood from Zeng's disclosure. Although Zeng does not explicitly state the purpose of its apertures is to "reduce mechanical and thermal effects," Petitioner argued this function was inherent and would have been immediately recognized by a POSITA. The problem of thermal warping from solder bonding was well-known, and using apertures below bonding pads was a known solution (as evidenced by Tsuchiya). Therefore, a POSITA reading Zeng would understand its structure provided this known benefit for the known problem, making the claimed invention obvious.
  • Expectation of Success: Given the structural similarity between Zeng and other prior art suspensions designed to manage solder bonding effects, a POSITA would have had a high expectation of success in using Zeng’s design for the purposes claimed in the ’499 patent.

• Additional Grounds: Petitioner asserted that claims 9, 10, and 20-22 are obvious over Tsuchiya in view of Arya (Patent 5,889,636), which teaches specific dielectric layer support configurations to absorb positional errors. Petitioner also challenged claims 5, 6, and 18 as obvious over the three-way combination of Tsuchiya, Albrecht, and Arya.

4. Key Claim Construction Positions

• "reduce mechanical and thermal effects": Petitioner argued this language, found in claims 1 and 12, is a non-limiting statement of intended use or purpose for an apparatus claim. The argument was that the patentability of the apparatus rests on its structure, not its intended function. The language merely elaborates on the purpose of the claimed structure (apertures under the pads) and does not impose a separate, patentable limitation.
• Claim 9 Indefiniteness/Construction: Petitioner argued that dependent claim 9, which recites "...when the is configured not to extend beneath the bonding region," is indefinite due to the missing antecedent for "the". If the Board were to correct the error, Petitioner proposed it should be construed to mean the spring metal is configured not to extend beneath the bonding region, but argued the claim is unpatentable regardless of its construction.

5. Relief Requested

• Petitioner requested institution of an inter partes review (IPR) and cancellation of claims 1-23 and 25 of the ’499 patent as unpatentable.