Broadcom Corp v. Tessera Inc

1. Case Identification

• Case #: IPR2017-01645
• Patent #: 6,046,076
• Filed: June 19, 2017
• Petitioner(s): Broadcom Corporation
• Patent Owner(s): Tessera, Inc.
• Challenged Claims: 1-4, 6, 10, and 19

2. Patent Overview

• Title: Vacuum Dispense Method for Dispensing an Encapsulant and Machine Therefor
• Brief Description: The ’076 patent describes a method for encapsulating a microelectronic assembly to reduce voids. The method involves applying a flowable encapsulant to the assembly while it is maintained under a sub-atmospheric pressure, then bringing the assembly to a higher pressure and holding it there before curing the encapsulant.

3. Grounds for Unpatentability

Ground 1: Claims 1-4 and 19 are obvious over JP ’743 in view of JP ’634.

• Prior Art Relied Upon: JP ’743 (Japanese Unexamined Patent Application No. S62-273743) and JP ’634 (Japanese Patent Publication No. 62-226634).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner argued that JP ’743 discloses the core method of claim 1 by teaching a process for encapsulating a semiconductor chip on a substrate. This process involves melting a thermofusible epoxy resin onto the chip at a sub-atmospheric pressure (8 mmHg or less), then returning the assembly to atmospheric pressure before moving it to an oven for curing. Petitioner contended that this maps to the claim steps of applying encapsulant under sub-atmospheric pressure, bringing it to a higher pressure (atmospheric), and curing it after bringing it to the higher pressure. Dependent claims 3 (atmospheric pressure) and 19 (pressure less than 200 milliTorr, which 8 mmHg falls within) were also allegedly taught.
  • Motivation to Combine: Petitioner asserted that JP ’743 inherently or implicitly discloses the “holding” step, as some period of time at atmospheric pressure is necessary before and during curing to achieve the stated goal of void reduction. To the extent JP ’743 is viewed as not explicitly teaching the "holding" step, Petitioner argued a POSITA would have been motivated to incorporate the teachings of JP ’634. JP ’634 explains that increasing pressure from a reduced level to atmospheric pressure “causes the voids that formed in the epoxy resin...to be squeezed out and eliminated.” A POSITA would combine this explicit rationale with the process of JP ’743 to ensure sufficient time at the higher pressure to eliminate voids before curing.
  • Expectation of Success: Because both references describe using a pressure differential (low to high) to reduce voids in encapsulant, a POSITA would have had a high expectation of success in ensuring the assembly in JP ’743 was held at atmospheric pressure for a sufficient time, as taught by JP ’634, to achieve the desired void-free result.

Ground 2: Claims 1-4, 6, 10, and 19 are obvious over JP ’955 in view of JP ’634.

• Prior Art Relied Upon: JP ’955 (Japanese Unexamined Patent Application No. S63-241955) and JP ’634 (Japanese Patent Publication No. 62-226634).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner argued that an alternate embodiment in JP ’955 expressly discloses applying a liquid resin to an LSI flip-chip assembly “while maintaining a depressurized state,” which directly teaches a key limitation of claim 1. JP ’955 then teaches “restoring the ambient pressure” and subsequently curing the resin, mapping to the remaining steps of claim 1. The petition asserted that JP ’955 also explicitly discloses the limitations of dependent claim 6, which recites an underfill application for a flip-chip assembly defining a gap between a microelectronic element and a substrate. Further, JP ’955 allegedly teaches claim 10 by describing the use of a rigid alumina substrate and claim 19 by stating the depressurized state is “10 millitorr or lower.”
  • Motivation to Combine: While JP ’955 discloses all steps of claim 1, Petitioner again cited JP ’634 to supplement the rationale for the “holding” step. A POSITA reading JP ’955’s teaching of restoring ambient pressure before curing would be motivated to look to analogous art like JP ’634, which explains the underlying mechanism of holding at the higher pressure to squeeze out voids. This would confirm the benefit of holding the assembly at ambient pressure for a sufficient time before curing to ensure a void-free underfill, which was the explicit goal of JP ’955.
  • Expectation of Success: A POSITA would expect that applying the well-understood void-elimination principles from JP ’634 to the specific underfill process of JP ’955 would successfully produce a robust, void-free encapsulated assembly, as both references rely on the same physical principles.

4. Key Claim Construction Positions

• "applying a flowable encapsulant...while maintaining the assembly under a subatmospheric pressure" (claim 1): Petitioner argued this term’s plain language requires the assembly to be held at sub-atmospheric pressure while the encapsulant flows around it. This construction is consistent with the specification’s goal of removing air from around the assembly prior to dispensing encapsulant.
• "holding the microelectronic assembly at said higher pressure" (claim 1): Petitioner asserted that, based on amendments and arguments made during prosecution to overcome prior art, this step must occur after the encapsulant-applying step is completed. The plain language and prosecution history allegedly make clear that the assembly is brought to and held at a higher pressure only after the application of the encapsulant is finished.

5. Arguments Regarding Discretionary Denial

• Petitioner argued that the asserted grounds were not cumulative of grounds considered in a previous IPR on the ’076 patent (IPR2013-00242). The petition noted that the primary prior art references in the current petition, JP ’743 and JP ’634, were not before the PTO during prosecution or the prior IPR. It also contended that while JP ’955 was previously cited, it was presented in a new manner and was not cumulative because the prior denial was based on a failure to distinguish it from a different reference (Oldham) not used in this petition.

6. Relief Requested

• Petitioner requested institution of an inter partes review and cancellation of claims 1-4, 6, 10, and 19 of the ’076 patent as unpatentable.