Broadcom Corp v. Tessera Inc

1. Case Identification

• Case #: IPR2017-01646
• Patent #: 6,218,215
• Filed: June 19, 2017
• Petitioner(s): Broadcom Corporation
• Patent Owner(s): Tessera, Inc.
• Challenged Claims: 1, 5, 6, 9-10, 12-13

2. Patent Overview

• Title: Methods of Encapsulating a Semiconductor Chip Using a Settable Encapsulant
• Brief Description: The ’215 patent relates to methods of making a semiconductor chip package by encapsulating a chip attached to a dielectric layer. The method involves using a pseudoplastic encapsulant with thixotropic properties, which is first sheared to reduce its viscosity for application between the chip and layer, and then cured to form a hardened encapsulant.

3. Grounds for Unpatentability

Ground 1: Obviousness over Kovac, as evidenced by Wang and DiStefano - Claims 1, 5, 6, 9-10, and 12-13 are obvious over Kovac in view of Wang and DiStefano.

• Prior Art Relied Upon: Kovac (International Publication No. WO 96/09746), Wang (Patent 5,817,545), and DiStefano (Patent 5,455,390).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner argued that Kovac teaches every element of the challenged claims. Kovac discloses a method for making a chip package by attaching a semiconductor chip (120) to a dielectric film substrate (100). It then dispenses a "compliant thixotropic material" (170) between the chip and substrate by forcing it through a nozzle (160), after which the material is cured. Petitioner contended this maps directly to the independent claim 1 steps of (A) attaching a microelectronic element to a dielectric layer, (B) shearing a thixotropic composition, (C) disposing the composition, and (D) curing it.
    • For step (B), Petitioner asserted that forcing a high-viscosity thixotropic material through Kovac's nozzle inherently constitutes shearing to reduce viscosity, a technique explicitly described in the ’215 patent itself.
    • For dependent claims, Petitioner argued Kovac teaches or renders obvious the additional limitations. Claims 5 and 6, requiring simultaneous or substantially simultaneous shearing and disposing, are met because forcing the material through Kovac’s nozzle accomplishes both actions at once. Claim 9 (flexible dielectric sheet) and claim 10 (polyimide sheet) are taught by Kovac’s disclosure of using a "flexible" dielectric film preferably made of a polymeric material like Kapton. DiStefano was cited as evidence that a person of ordinary skill in the art (POSITA) would have known Kapton is a polyimide film. Claims 12 (semiconductor chip) and 13 (wafer) are met by Kovac's explicit description of its process applying to both individual chips and entire semiconductor wafers.
  • Motivation for Modification/Interpretation: Petitioner did not assert a traditional combination, but rather that Wang and DiStefano provide evidence of what a POSITA would have understood from Kovac's disclosure. A POSITA reading Kovac’s reference to Kapton film would have consulted a reference like DiStefano (or possessed the knowledge it contains) to understand its composition as polyimide. Similarly, a POSITA would understand from references like Wang that the underfill process described by Kovac results in an "encapsulant." The motivation was not to combine disparate systems but to interpret Kovac’s teachings with the ordinary knowledge in the art at the time.
  • Expectation of Success: The expectation of success was inherent, as Petitioner argued Kovac already discloses a complete, functional process for encapsulating a semiconductor chip that meets all limitations of the challenged claims. The secondary references merely confirm the understanding of the terms and materials used.

4. Key Claim Construction Positions

• "a thixotropic composition": This term was central to Petitioner's invalidity argument. Petitioner argued that for the purposes of the proceeding, the term should be construed as "a material with a high initial viscosity at 25°C... and sufficient pseudoplastic properties when sheared to lower its viscosity enough to completely fill the area between the... microelectronic element and the dielectric layer, and which must regain viscosity approximating its initial viscosity when the shear force is removed so as to prevent any visible flow." This construction was based on the ’215 patent's specification, which describes the composition as being "sufficiently thixotropic to prevent flow-out" after a mold is removed. Petitioner contended that Kovac’s "compliant thixotropic material," which is used without a mold and does not flow out, necessarily meets this functional definition.

5. Arguments Regarding Discretionary Denial

• Petitioner argued that discretionary denial under 35 U.S.C. §325(d) would be inappropriate. While the U.S. patents corresponding to the Kovac and DiStefano references were listed on an Information Disclosure Statement during prosecution, Petitioner asserted there is no evidence the examiner substantively considered or applied their teachings against the claims. The petition presented a specific invalidity theory, supported by expert testimony, that was never before the examiner. Therefore, Petitioner contended the "same or substantially the same prior art or arguments" had not been previously presented to the Office.

6. Relief Requested

• Petitioner requests institution of an inter partes review and cancellation of claims 1, 5, 6, 9-10, and 12-13 of the ’215 patent as unpatentable.