PTAB

IPR2019-01100

Volvo Cars Of North America LLC v. WatLow Electric Mfg Co

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Key Events
Petition

1. Case Identification

2. Patent Overview

  • Title: Method for the Production of an Electrically Conductive Resistive Layer and Heating and/or Cooling Device
  • Brief Description: The ’869 patent discloses a layered resistive heater for application to a complex shaped substrate, such as a tube. The method involves depositing an electrically conductive resistive layer via a particle deposition process (e.g., plasma spraying) and then using a laser to trim a pattern into the layer to achieve a desired electrical resistance.

3. Grounds for Unpatentability

Ground 1: Claims 1 and 8 are obvious over Toyota in view of Imaoka.

  • Prior Art Relied Upon: Toyota (Patent 6,096,995) and Imaoka (Japanese Patent Application Publication No. S57-172702).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Toyota disclosed all key limitations of independent claims 1 and 8. Toyota taught a cylindrical heater for pipes (“complex shaped substrate”) with a nonconductive insulating layer and an electrically conductive resistive layer formed by applying a paste of metallic particles. Petitioner asserted Toyota’s disclosure of forming the layer via paste application, screen printing, or metallizing inherently involved a process of forming a material from particles. Toyota also explicitly taught using a laser to trim slots into the resistive layer to adjust resistance, forming complex patterns and creating a desired resistance. Petitioner contended that the claimed "micro-welding" would inherently occur during Toyota’s laser trimming (heating and resolidifying particles) or its calcination step. The final limitation, introducing "local oxides" to "fine tune" resistance, was allegedly rendered obvious by Imaoka, which taught a method of simultaneously laser trimming and performing a forced oxidation treatment to tune and stabilize the resistance value of a thin film resistor.
    • Motivation to Combine: A POSA would combine Toyota with Imaoka to improve the stability of the final resistor. Toyota’s laser trimming would create a heat-affected zone with unstable resistance, an issue directly addressed by Imaoka’s method of blowing oxygen during trimming to form a stabilizing oxide passivation film. This combination would reduce manufacturing steps and costs.
    • Expectation of Success: A POSA would have a reasonable expectation of success because Imaoka’s process was applicable to various common resistive materials, including those disclosed by Toyota, and addressed a known problem of resistance instability after laser trimming.

Ground 2: Claims 1 and 8 are obvious over Brook-Levinson in view of Imaoka.

  • Prior Art Relied Upon: Brook-Levinson (WO 00/70915) and Imaoka (Japanese Patent Application Publication No. S57-172702).

  • Core Argument for this Ground:

    • Prior Art Mapping: Petitioner argued that Brook-Levinson, a reference describing electrical heating elements, disclosed the claimed structural characteristics. Brook-Levinson taught a heater for a pipe ("complex shaped substrate") with an insulating layer and a resistive layer formed by plasma or flame spraying boron-containing particles. A complex contour pattern (e.g., helical) was formed by spraying through a mask. Petitioner contended this structure met the product limitations of the claims. While Brook-Levinson used a mask instead of a laser, Petitioner argued that for these product-by-process claims, the final product structure is what matters. Alternatively, Petitioner argued it would be obvious to substitute Brook-Levinson’s mask with the well-known process of laser trimming, as taught by Imaoka, to achieve more precise patterns and better resistance control. Petitioner asserted that micro-welding was inherent in Brook-Levinson's plasma spray process, where particles "adhere to each other." Finally, the "local oxides" limitation was met by combining with Imaoka’s laser trimming and oxidation process.
    • Motivation to Combine: A POSA would be motivated to replace Brook-Levinson’s masking process with Imaoka’s laser trimming and oxidation process to gain precision, flexibility, and efficiency. Laser trimming allows for more intricate patterns than masking and simultaneously tunes and stabilizes resistance, reducing manufacturing costs and improving the final product’s stability.
    • Expectation of Success: The combination was expected to succeed as laser trimming was an established, indispensable process for manufacturing high-precision resistors, and its application to the types of resistive layers disclosed in Brook-Levinson was straightforward.

  • Additional Grounds: Petitioner asserted additional obviousness challenges for dependent claims 2-4 and 9-11. These grounds added Macher (Patent 6,717,109) for its teaching of a protective sealing layer over a heating element, and Juliano (Patent 5,973,296) for its disclosure of heaters with multiple, alternating stacked dielectric and resistive layers to achieve better temperature profiles and redundancy.

4. Key Claim Construction Positions

  • "micro-welded": Petitioner argued that while the ’869 patent specification only described micro-welding as resulting from the initial deposition process, the claims required it to result from the subsequent laser trimming step. Citing the patent owner’s infringement contentions, Petitioner contended that laser trimming inherently causes micro-welding as particles at the edge of the laser cut melt and resolidify, joining together.
  • "local oxides are brought into the pattern to fine tune an electrical resistance": Petitioner argued this limitation requires oxidation that adjusts resistance toward a prescribed value. Petitioner asserted that patent owner’s position that laser trimming in open air necessarily causes sufficient oxidation to meet this limitation was overly broad. However, Petitioner also argued that even under this broad interpretation, the claims were obvious because the prior art calcination or laser trimming processes would inherently cause such oxidation.

5. Key Technical Contentions

  • Product-by-Process Claims: A central contention was that the challenged claims are product-by-process claims. Therefore, for validity analysis, the focus must be on the structure of the final product, not the specific manufacturing process recited. This allowed Petitioner to argue that prior art disclosing the claimed final heater structure was invalidating, even if that prior art used a different manufacturing process (e.g., using a mask for patterning instead of a laser).

6. Relief Requested

  • Petitioner requested the institution of an inter partes review and the cancellation of claims 1-4 and 8-11 of the ’869 patent as unpatentable under 35 U.S.C. §103.