Greenthread LLC v. Semiconductor Components Industries, LLC, d/b/a Onsemi et al.

This Inter Partes Review (IPR) proceeding, IPR2024-00264, involves patent owner Greenthread LLC and petitioner Semiconductor Components Industries, LLC, operating as Onsemi. Greenthread LLC is identified as a patent assertion entity (PAE) or Non-Practicing Entity (NPE) that focuses on semiconductor intellectual property, asserting patents derived from fundamental device architecture innovations against established chipmakers. Its portfolio is linked to inventor G.R. Mohan Rao, who is also a director and founder of Greenthread. On the other side, Onsemi is a global leader in intelligent power and sensing technologies, providing semiconductor solutions for automotive, industrial, and cloud infrastructure markets, with a product range including power MOSFETs, IGBTs, silicon carbide devices, and image sensors. Onsemi is a publicly traded operating company that emerged as a spin-out from Motorola's semiconductor components business.

The IPR targets US Patent 10,734,481, which is part of a family of patents generally related to CMOS semiconductor devices featuring "graded dopant regions". These patents describe semiconductor devices utilizing graded dopants and well regions to create electric fields. These fields are designed to aid or limit the movement of charge carriers from the semiconductor surface to the substrate, thereby enhancing device performance. The challenged patent stems from an underlying district court patent infringement lawsuit, Greenthread, LLC v. ON Semiconductor Corporation, Case No. 1:23-cv-00443, filed in the U.S. District Court for the District of Delaware. In that litigation, Greenthread accused Onsemi's semiconductor devices, particularly those with graded dopant regions, including the AR0820AT, a ½” Format, 8.3 MP, 2.1 micrometer Pixel Pitch, Stacked Back-illuminated CMOS Image Sensor, of infringement.

This IPR was filed at the Patent Trial and Appeal Board (PTAB) on December 11, 2023, by Onsemi to challenge the validity of Patent 10,734,481, and it has since reached a Final Written Decision. The district court litigation in Delaware was administratively closed and stayed pending the outcome of this and related IPR proceedings, demonstrating the strategic importance of the PTAB as a venue for challenging patent validity and suspending costly district court litigation. The case is notable as it exemplifies the ongoing trend of patent assertion entities targeting major semiconductor manufacturers with foundational intellectual property, often leading to multiple IPR challenges by defendants seeking to invalidate patents that impact broad product categories. A favorable outcome for Onsemi in this IPR, particularly the cancellation of claims, could provide significant freedom-to-operate relief within the semiconductor industry, given the fundamental nature of the technology involved.

This analysis details the key legal developments and outcome for IPR2024-00264, Greenthread LLC v. Semiconductor Components Industries, LLC, d/b/a Onsemi et al., concerning U.S. Patent 10,734,481.

Key Legal Developments and Outcome:

• Filing of Inter Partes Review (IPR) Petition (2023-12-11): Semiconductor Components Industries, LLC, d/b/a Onsemi, and On Semiconductor Corporation filed a petition for Inter Partes Review (IPR2024-00264) challenging the patentability of U.S. Patent 10,734,481. The IPR was filed against patent owner Greenthread LLC. The prompt provides a filing date of December 11, 2023. A public database lists a "Filing Date" of October 12, 2023, for IPR2024-00264, but for consistency with the provided case metadata, the December 11, 2023 date is used.

• Parallel District Court Litigation and Stay (2023-05-02 & 2024-04-23): U.S. Patent 10,734,481 was also at issue in a district court patent infringement case, Greenthread, LLC v. Monolithic Power Systems, Case No. 1:23-cv-00579, filed in the District of Delaware on May 2, 2023. The Delaware District Court subsequently stayed this case on April 23, 2024, pending the resolution of IPR proceedings challenging the validity of the asserted patents, including 10,734,481. This stay was intended to allow the Patent Trial and Appeal Board (PTAB) to resolve patent validity issues, which could simplify or eliminate claims in the district court litigation.

• Institution Decision (2024-10-11): The Patent Trial and Appeal Board (PTAB) instituted IPR2024-00264 on October 11, 2024, deciding to proceed with a review of the challenged claims of U.S. Patent 10,734,481.

• Final Written Decision (2025-04-29): The PTAB issued a Final Written Decision for IPR2024-00264 on April 29, 2025. The publicly available information does not explicitly state the detailed outcome of this decision (i.e., which specific claims of U.S. Patent 10,734,481 were found unpatentable or patentable).

• Related IPRs and Director Review (April-May 2025): While not directly related to U.S. Patent 10,734,481, Semiconductor Components Industries, LLC (Onsemi) also challenged other Greenthread patents (U.S. Patent Nos. 11,121,222 and 10,510,842) in parallel IPRs (IPR2023-01242, IPR2023-01243, IPR2023-01244). In April and May 2025, the USPTO Director vacated and remanded the Final Written Decisions in these related IPRs back to the PTAB. The Director found that the PTAB had erred by denying Greenthread's requests for discovery into potential privity relationships between Onsemi and Intel, which was relevant to time-bar arguments, and also faulted the Board for improperly excluding district court claim construction rulings and rejecting some of Greenthread's claim construction responses as untimely. These vacaturs and remands require further proceedings, including allowing for appropriate discovery.

• Current Posture: The IPR2024-00264 proceeding reached a Final Written Decision on April 29, 2025. The specific outcome of that decision regarding the patentability of claims of U.S. Patent 10,734,481 is not publicly detailed in the available search results. Any subsequent appeal to the Federal Circuit would typically occur after such a decision, but no information on an appeal for IPR2024-00264 has been found in the provided sources. The related district court case, Greenthread, LLC v. Monolithic Power Systems, remains stayed pending the resolution of the IPRs.

Greenthread LLC is represented by McKool Smith, P.C. in IPR2024-00264.

The following attorneys are identified as counsel of record for Greenthread LLC:

• Alan L. Whitehurst

  • Role: Lead Counsel
  • Firm: McKool Smith, P.C., Washington, D.C.
  • Experience Note: Alan Whitehurst is a principal and trial lawyer specializing in intellectual property and unfair competition cases, with deep expertise in complex technologies, including semiconductors, and has successfully argued numerous inter partes reviews (IPRs). He has recovered over $85 million for Greenthread and Vervain, companies founded by inventor Dr. Mohan Rao.

• Arvind Jairam

  • Role: Counsel
  • Firm: McKool Smith, P.C., Washington, D.C.
  • Experience Note: While the searches confirm his appearance as counsel for Greenthread in this and related IPRs, specific details about his individual patent litigation experience or notable past cases are not explicitly available in the provided snippets.

Based on the available search results, Michael J. Flibbert and Jeffrey W. Gluck do not appear to be representing Greenthread LLC in this IPR. Michael J. Flibbert is a partner at Finnegan, with extensive patent litigation and IPR experience for other clients. Jeffrey S. Gluck (with a different middle initial) is associated with Gluck Law Firm, handling other types of intellectual property matters. While Farnan LLP was identified as Delaware local counsel for Greenthread in a related district court case, they are not specifically listed as counsel for Greenthread in IPR2024-00264.

I'll research the petitioner's counsel of record. In this IPR, the "defendant" side is the petitioner, Semiconductor Components Industries, LLC d/b/a Onsemi (and ON Semiconductor Corporation).

Strong results. Let me verify the specific counsel list for IPR2024-00264 and gather firm/experience details.

Let me verify firm affiliations and check the parallel district court defense counsel plus the appeal.

Counsel of Record — Defense/Petitioner Side

Posture note: IPR2024-00264 is a PTAB trial, so there is no "defendant" in the district‑court sense. The adverse party to Patent Owner Greenthread is the Petitioner, Semiconductor Components Industries, LLC d/b/a onsemi (with ON Semiconductor Corporation). Consistent with the prior sections (which treated Greenthread as the "plaintiff" side), the counsel below are the petitioner/defense-side team of record in IPR2024-00264.

The single most reliable source is the Board's joint order of May 28, 2025 (IPR2024‑00263 Paper 58; IPR2024‑00264 Paper 59; IPR2024‑00265 Paper 60; IPR2024‑00266 Paper 60, Conduct of Proceeding, 37 C.F.R. § 42.5), which lists the full petitioner team across all four sister IPRs — docketalarm.com PDF. The same team is listed in Petitioner's Updated Mandatory Notices served April 29, 2025 and in the Director‑Review/Rehearing filings.

Baker Botts L.L.P. (principal counsel)

Additional/outside backup counsel

In-house counsel (client representatives, not counsel of record)

• Josh Engel (also rendered "Josh Engle") — onsemi in‑house counsel; identified in the record as an onsemi in‑house attorney and appeared as a client representative at the oral hearing/conference call (PTACTS transcript).
• Rob Tuttle — Chief IP Counsel, onsemi; listed as a client representative on the same call.

Notable caveats / discrepancies flagged

1. Name transcription artifacts. The oral‑argument transcript renders backup counsel as "Mark Spiegel" and "Elliott Williams"; the Board's own orders and the mandatory notices use "Mark Speegle" and "Eliot D. Williams." I treat the Board orders/mandatory notices as authoritative.
2. Delaware local counsel for the defendants not confirmed. The D. Del. docket reflects Baker Botts' Mark Speegle admitted pro hac vice for ON Semiconductor Corporation and Semiconductor Components Industries, LLC, and Law.com Radar's April 24, 2023 entry stated "counsel have not yet appeared for the defendant." I did not find a confirmed Delaware local‑counsel firm for the defendants in the sources reviewed, so I am not naming one. (Farnan LLP, which appears in that docket/Radar entry, is Greenthread's local counsel, not the defendants'.)
3. Status conflict. Case metadata says "Final Written Decision," while the IPVerse PTAB tracker lists IPR2024‑00264 as "Final Written Decision – Appealed" with a termination date of Jan. 28, 2026. If accurate, a Federal Circuit appeal exists; the appeal briefs would ordinarily be handled by the same Baker Botts team, but I could not verify Federal Circuit counsel of record from the sources reviewed. Treat the appeal‑counsel point as unconfirmed.
4. Sealing. Several petitioner/patent‑owner papers in the -0026x family were subject to motions to seal (e.g., "names of potential privies"), but the counsel identifications themselves are public in the Board's orders and mandatory notices — no sealing issue affects the roster above.