PTAB

IPR2015-01276

Asetek Danmark As v. Coolit Systems Inc

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1. Case Identification

2. Patent Overview

  • Title: Fluid Heat Exchanger Configured to Provide a Split Flow
  • Brief Description: The ’330 patent discloses a fluid heat exchanger designed for liquid cooling of electronic components. The invention centers on a split-flow arrangement where coolant enters a central region of a microchannel array, flows in two sub-flows toward opposite ends, and then exits. This configuration is intended to reduce the overall fluid pressure drop across the heat exchanger.

3. Grounds for Unpatentability

Ground 1: Obviousness over Kang and Bonde - Claims 1-8, 21, 24, and 26 are obvious over Kang in view of Bonde.

  • Prior Art Relied Upon: Kang (Application # 2006/0096738) and Bonde (Patent 5,099,311).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Kang discloses the fundamental elements of independent claim 1, including a heat spreader plate with fins, a housing, inlet and outlet headers, and a flow distributor plate that implements a split-flow design. To the extent Kang was deemed not to explicitly teach "microchannels," Petitioner asserted that Bonde remedies this by disclosing a heat sink with a plurality of parallel microchannels and an inlet manifold that opens into each microchannel.
    • Motivation to Combine: A person of ordinary skill in the art (POSITA) would combine the teachings because both Kang and Bonde relate to the same field of split-flow heat exchangers for cooling electronics. A POSITA would be motivated to incorporate the explicit microchannel structure from Bonde into Kang’s overall system to maximize heat transfer efficiency, a well-known design objective.
    • Expectation of Success: A POSITA would have a reasonable expectation of success in the combination. Kang already utilizes microfins and a flow distributor, making the modification to include Bonde's more defined microchannel and manifold design a predictable and straightforward improvement.

Ground 2: Obviousness over Kang/Bonde plus Philpott - Claims 9-11 are obvious over Kang and Bonde, in further view of Philpott.

  • Prior Art Relied Upon: Kang (Application # 2006/0096738), Bonde (Patent 5,099,311), and Philpott (Patent 6,827,128).
  • Core Argument for this Ground:
    • Prior Art Mapping: This ground targets dependent claims 9-11, which add limitations requiring varied microchannel lengths that result in a "scalloped edge" and larger outlet openings for central channels. Petitioner asserted that Philpott teaches these features, disclosing a microchannel heat exchanger with an "hourglass" shape where central microchannels are shorter than those at the edges. This design is explicitly taught by Philpott to create uniform flow and reduce pressure build-up.
    • Motivation to Combine: A POSITA, having already arrived at the Kang/Bonde combination, would be motivated to incorporate Philpott's teachings to further enhance performance. The specific motivation was to adopt Philpott's technique of varying channel lengths to further reduce pressure drop and flow resistance, a known problem in the art that Philpott was designed to solve.
    • Expectation of Success: The combination would yield predictable results. Modifying the outlet groove geometry of the base Kang/Bonde system to be "scalloped" as taught by Philpott was presented as a simple design modification to achieve a known benefit.

Ground 3: Obviousness over Kang and Bhatti - Claims 12, 14, 15, 18-20, 22, 23, 25, 27, and 28 are obvious over Kang in view of Bhatti.

  • Prior Art Relied Upon: Kang (Application # 2006/0096738) and Bhatti (Application # 2007/0163750).
  • Core Argument for this Ground:
    • Prior Art Mapping: This ground addresses a separate set of claims, including independent claims 12 and 14, which require inlet and outlet header regions to be on "opposite" sides of the fins. Petitioner argued that while Kang provides the basic heat exchanger structure, Bhatti explicitly teaches a heat sink with an inlet plenum and an outlet plenum positioned on opposite sides of the microchannels, directly mapping this key limitation.
    • Motivation to Combine: Petitioner contended that a POSITA would combine Kang and Bhatti as a matter of simple design choice. Since both references address split-flow heat exchangers, modifying the header arrangement in Kang to adopt the opposite-side configuration from Bhatti would have been an obvious and predictable way to arrange the components to achieve a desired flow path.
    • Expectation of Success: Success in combining the references would have been reasonably expected, as it merely involved incorporating a known header configuration from Bhatti into the similar system of Kang without requiring undue experimentation.
  • Additional Grounds: Petitioner asserted an additional obviousness challenge (Ground 4) for claims 13, 16, and 17 based on the combination of Kang, Bhatti, Bonde, and Philpott, relying on similar rationales to supply the "scalloped edge" limitation to the claims challenged in Ground 3.

4. Key Claim Construction Positions

  • Petitioner argued that the terms "fluid inlet opening," "aperture," and "inlet to the microchannels" used across independent claims 1, 12, and 14 should be construed synonymously to mean "one or more passages on the plate that provide fluid flow from the inlet header into the plurality of microchannels."
  • Likewise, Petitioner contended that "fluid outlet opening" and "outlet to the microchannels" should be construed to mean "one or more passages on the plate that provide fluid flow from the plurality of microchannels to the outlet header." These constructions, which Petitioner supported by citing the specification's explicit allowance for multiple openings, were foundational to mapping the teachings of the prior art references to the claims.

5. Key Technical Contentions (Beyond Claim Construction)

  • Petitioner’s obviousness arguments were premised on a core technical assertion about the state of the art at the time of the invention. It contended that by 2007, using split-flow arrangements to shorten fluid flow paths and employing microchannels to increase heat transfer surface area were well-known, conventional, and established techniques for improving thermal performance and reducing pressure drop in liquid cooling systems for electronics.

6. Relief Requested

  • Petitioner requested the institution of an inter partes review and the cancellation of claims 1-28 of Patent 8,746,330 as unpatentable.