US 6398347

I'll search for authoritative information on US patent 6398347, including any recent litigation activity.

Let me check the appellate docket and any recent (2026) activity.

US Patent 6,398,347 — Summary

Identification (as printed on the face of the record / Google Patents)

Source: https://patents.google.com/patent/US6398347/en

Abstract (verbatim): "An ink jet printhead having FET drive circuits that are configured to compensate for power trace parasitic resistances."

Problem addressed. In a thin-film (thermal) ink jet printhead, the conductive power traces running from the bond pads to each heater resistor and its drive FET present a parasitic resistance that varies with the trace length/location. Drop generators far from the bond pads therefore receive less energy than those nearby, forcing the system to apply over-energy to guarantee firing. Over-energy causes kogation, reduced resistor life, and inconsistent bubble nucleation. The patent notes an existing fix — varying trace width ("trace width variation is a known technique for energy balancing") — but states it makes narrowing the die difficult.

The disclosed solution. Instead of (or in addition to) tuning the traces, the on-resistance of each integrated FET drive circuit is deliberately varied so that the sum of (FET on-resistance + local power-trace parasitic resistance) is roughly constant across the printhead. Per the specification, on-resistance is set by the length of a continuously non-contacted segment of the elongated drain-region fingers (a segment devoid of drain contacts), or alternatively by the size of the FET. Because un-contacted drain finger region needs no overlying drain electrode, the associated ground bus can be widened over the transistor active area without increasing the array's footprint — yielding a ground bus whose width tapers with distance from the bond pads. This is the "energy balanced" aspect.

Plain-language reading of the independent claims

• Claim 1 — An ink jet printer apparatus with a printhead made of a substrate plus thin-film layers; several ink drop generators; several FET circuits, each wired to a respective drop generator; power traces connecting bond pads to the drop generators and FETs. The key limitation: the on-resistances of the FET circuits are chosen so as to offset the differing parasitic resistance of the power traces.

• Claim 3 — Same as claim 1, but reciting the FET's internal structure (drain electrodes/regions/contacts; source electrodes/regions/contacts), and locating the compensation in the drain regions, which are configured to set each FET's on-resistance to offset power-trace parasitic resistance.

• Claim 5 — The same idea recast in a longitudinal layout: an elongated printhead with bond pads at both longitudinally separated ends, a longitudinal array of drop generators, and a longitudinal array of adjacent FET circuits; the FET on-resistances are selected to compensate for the parasitic-resistance variation of the power traces.

• Claim 8 — Claim 5 plus the detailed FET drain/source structure, with the drain regions used to set the compensating on-resistance.

• Claim 10 — Claim 5, with the added directional requirement that FET on-resistances decrease as distance from the closest longitudinal end increases (i.e., FETs farther from the nearest bond pad are made more efficient).

• Claim 11 — Claim 5, further requiring a ground bus running along the printhead length whose width varies along that length, with the FETs configured to compensate for power-trace parasitic-resistance variation.

Dependent claims 2 and 6 cover setting on-resistance by FET size; claims 4 and 9 cover the elongated drain regions with a continuously non-contacted segment of selected length; claim 7 adds apparatus for imparting relative motion between the printhead and the print medium (i.e., a printer); claim 12 specifies that the ground bus width decreases with increasing distance from the closest longitudinal end.

Litigation activity found

Contrary to the instruction to check "CAFC 2026 dockets," I found no 2026 Federal Circuit or district-court activity involving US 6,398,347. The litigation history I could substantiate is older:

• N.D. Cal. 3:10-cv-00965 and 3:10-cv-02175, Hewlett-Packard Co. et al. v. Microjet Technology Co., Ltd. et al., filed ~March/May 2010. Patents asserted included US 6,234,598; US 6,309,053; US 6,398,347; US 6,412,917; US 6,481,817; US 6,402,279. (NPE Litigation Database: https://npe.law.stanford.edu/patent/6398347)
• ITC Investigation Nos. 337-TA-711 and 337-TA-723. The ITC's final determination (Dec. 1, 2011) found MicroJet and PTC in direct infringement of the '347 patent as to claims 1, 3–5, and 8–12 — i.e., essentially all the independent claims plus their dependents — and issued a general exclusion order. (Summary reporting: https://iknow.stpi.niar.org.tw/post/read.aspx?postid=4882; ITC pub. 4373 at https://www.usitc.gov/intellectual_property/documents/pub4373.pdf)
• CAFC No. 12-1225 is the appeal arising from that ITC proceeding, as listed on the patent's Google Patents page. This is a 2012-era docket, not a 2026 one.

Uncertainty / caveats

1. I could not verify any 2026 docket entry for this patent. My searches surfaced only the 2010–2012 enforcement campaign. If a 2026 CAFC or PTAB matter exists, I did not find it and cannot confirm it.
2. The patent expired on 2000-07-24 + 20 years = 2020-07-24 (maintenance fees were paid at the 4-, 8-, and 12-year marks), which would make new 2026 infringement assertions unlikely.
3. The Google Patents "pending/U.S. application" statuses shown for several foreign family members (e.g., AU3302501A "Pending," MXPA02012629A "IP Right Grant") are automated legal-status placeholders, not legal conclusions.
4. Assignee history: original assignee Hewlett-Packard Company; reassigned to Hewlett-Packard Development Company, L.P. in January 2005.

Note: the related sibling patent US 6,309,053 B1 ("Ink jet printhead having a ground bus that overlaps transistor active regions"), same inventors/priority date, covers the ground-bus-over-active-region aspect separately from the energy-balancing claims of the '347 patent.

I'll research litigation involving US patent 6398347. Let me start with searches across the litigation sources.

Let me dig deeper into the specific cases identified.

I've gathered substantial information. Let me compile the litigation record for US Patent 6,398,347 based on the sources retrieved.

Litigation Involving US Patent No. 6,398,347 ("Energy balanced ink jet printhead")

Note on identification: This analysis concerns U.S. Patent No. 6,398,347 B1 (application 09/626,367), filed July 24, 2000, granted June 4, 2002, inventors Joseph M. Torgerson and David M. Hurst, originally assigned to Hewlett-Packard Company, now Hewlett-Packard Development Company, L.P. It was terminologically related (same family) to US 6,648,788 B2 (continuation). I have not substituted or "corrected" any patent numbers; where a case asserted several patents including the '347, I note that explicitly.

The Google Patents litigation record for this patent, plus the Stanford NPE Litigation Database, identify the following matters:

1. Hewlett-Packard v. MicroJet Technology et al. (N.D. Cal.)

• Plaintiff(s): Hewlett-Packard Company / Hewlett-Packard Development Company, L.P.
• Defendant(s): MicroJet Technology Co., Ltd.; Asia Pacific Microsystems, Inc.; Mipo Technology Limited; MIPO Science & Technology Co., Ltd. (Guangzhou); Mextec Group Inc. (d/b/a Mipo America); SinoTime Technologies, Inc.; PTC Holdings Limited
• Jurisdiction: U.S. District Court, Northern District of California
• Case No.: 3:10-cv-02175
• Filing date: May 20, 2010
• Status/outcome: According to the Stanford NPE Litigation Database (which lists this and one companion case as the only two district-court matters for this patent), this is recorded as a "IP subsidiary of product company" asserting against product companies. I was unable to confirm a final judgment on the merits within the search window.

2. Hewlett-Packard v. MicroJet Technology et al. (N.D. Cal.) — companion case

• Plaintiff(s): Hewlett-Packard Company / Hewlett-Packard Development Company, L.P.
• Defendant(s): Same group of respondents/defendants as above
• Jurisdiction: U.S. District Court, Northern District of California
• Case No.: 3:10-cv-00965
• Filing date: 2010 (companion to 3:10-cv-02175)
• Status/outcome: Not confirmed in retrieved sources; listed in the patent's litigation family record.

3. ITC Inv. No. 337-TA-723, Certain Inkjet Cartridges with Printheads and Components Thereof

• Complainant(s): Hewlett-Packard Company and Hewlett-Packard Development Company, L.P.
• Respondent(s): MicroJet Technology Co., Ltd.; Asia Pacific Microsystems, Inc. (APM); Mipo Technology Limited; Mipo Science & Technology Co., Ltd.; Mextec d/b/a Mipo America Ltd.; SinoTime Technologies, Inc.; PTC Holdings Limited
• Jurisdiction: U.S. International Trade Commission
• Case No.: 337-TA-723
• Filing/Institution date: Investigation instituted 2010 (HP complaint; target dates set in 2010–2011)
• Asserted patents: U.S. Patent Nos. 6,234,598; 6,309,053; 6,398,347; 6,481,817; 6,402,279; 6,412,917
• Outcome/Status:
  • ALJ Robert K. Rogers issued an Initial Determination on June 10, 2011 (public version Aug. 4, 2011) finding a violation of Section 337. MicroJet was in default; PTC and MicroJet were found to directly infringe the remaining asserted patents; APM was found liable for contributory infringement but not direct or induced infringement. The asserted patents were found not invalid, and a domestic industry was found to exist. Mipo, Mipo Tech., SinoTime, and Mextec settled/were terminated. HP withdrew the '917 patent allegations.
  • The Commission reviewed the ID in part (notice Aug. 11, 2011), reversing the ALJ on induced infringement and finding APM liable for induced infringement under a "willful blindness" theory.
  • Final determination (Oct. 24, 2011): The Commission found a violation of Section 337 and issued a general exclusion order prohibiting entry of infringing inkjet cartridges with printheads and components thereof, with a 100% bond during the Presidential review period. The investigation was terminated.

4. ITC Inv. No. 337-TA-711, Certain Ink Cartridges with Printheads and Components Thereof

• Complainant(s): Hewlett-Packard Company / Hewlett-Packard Development Company, L.P.
• Respondent(s): MicroJet Technology (among others)
• Jurisdiction: U.S. International Trade Commission
• Case No.: 337-TA-711
• Status/outcome: This earlier investigation is referenced in the 337-TA-723 record — the Commission cited 337-TA-711 (in which MicroJet was accused of infringing the same patents) as background supporting its "willful blindness" induced-infringement finding against APM in the '723 case. Full details of the '711 final outcome were not retrieved within the search window.

5. Court of Appeals for the Federal Circuit — Appeal No. 12-1225

• Parties: Appeal arising from the ITC 337-TA-723 determination (represented in the patent record as a Federal Circuit matter)
• Jurisdiction: U.S. Court of Appeals for the Federal Circuit
• Case No.: 2012-1225
• Status/outcome: Listed in the patent's litigation family record as a CAFC case. I could not confirm the appellant/appellee identities or the disposition within the search window and flag this as an open item rather than assert a result.

Summary and caveats

• The 6398347 patent's primary litigation footprint is Hewlett-Packard's enforcement campaign against third-party (largely Chinese/Taiwanese) inkjet cartridge and integrated-circuit makers — primarily through ITC Section 337 actions and parallel N.D. Cal. district court suits around 2010.
• The confirmed outcome is the ITC 337-TA-723 general exclusion order (Oct. 24, 2011).
• The patent is now expired (anticipated expiration July 24, 2020), so no active enforcement is possible.
• Unconfirmed items I did not fabricate results for: the disposition of companion district court case 3:10-cv-00965; the precise parties and outcome of Federal Circuit No. 12-1225; and the final disposition of ITC 337-TA-711. These should be verified directly on the Federal Circuit docket and ITC EDIS if a definitive record is required.
• I did not return results for similar-but-different numbers (e.g., the numerous unrelated "834", "639", or "347" patents that dominated generic search results); those were excluded as required.

Sources: Google Patents litigation record for US6398347B1 (https://patents.google.com/patent/[US6398347](/patent/US6398347)/en); Stanford NPE Litigation Database, patent 6398347 (https://npe.law.stanford.edu/patent/6398347); ITC public notices and publications (e.g., USITC Pub. 4373; Federal Register notices at govinfo.gov); Lexology/ITC 337 Blog case summaries for 337-TA-723; National Law Review analysis of the 337-TA-723 general exclusion order.

I'll verify the structured block against live sources before answering.

US 6,398,347 — PTAB / AIA Trial Landscape

Bottom line up front: There are no AIA trial proceedings on this patent. The structured "PTAB proceedings on file" block (USPTO ODP) returns zero records, and targeted searching surfaced none either. This is a real absence, not a data gap — but it is not the same as "the patent is untested." It was tested hard in a different forum (ITC § 337) and survived. The more decisive fact for a defendant today is that the patent expired.

Proceedings overview

Total AIA trial proceedings on US 6,398,347: 0. Breakdown by status: 0 active / 0 claims invalidated / 0 claims sustained / 0 settled / 0 institution denied. All twelve claims (1–12) are untested at the PTAB, and there is no § 315(e)(2) estoppel on any ground because no petitioner ever filed. The defensive posture this gives a defendant is not "the troll has no case" — it is "no IPR has ever been filed, so there is no free kill shot; the patent was instead upheld in an ITC investigation, and the doctrine that would have mattered is expiration, not patentability."

Companion check — no AIA trial found

⚠️ Scope caveat, stated honestly: the ODP block covers AIA trials only. I found no evidence of an ex parte reexamination of the '347 patent either, but I cannot affirmatively rule one out from the sources available in this session. A prosecution-history/reexam check on PTAB E2E or Patent Public Search would close that gap.

What actually happened to this patent (non-PTAB, but dispositive for a defendant)

Because the requested per-proceeding format assumes proceedings that do not exist, the useful substitute is the real adjudicative record. Note carefully: none of the below is an AIA trial, and none of it is statutory estoppel-generating under § 315(e).

ITC Inv. No. 337-TA-723 — Hewlett-Packard v. MicroJet / Asia Pacific Microsystems / PTC et al.

• Forum: U.S. International Trade Commission (not the PTAB). ALJ Robert K. Rogers.
• Complaint filed / instituted: Commission instituted 2010-06-25 on HP's complaint. 75 Fed. Reg. 36442.
• Patent owner posture: HP was the complainant (enforcer), asserting the '347 patent along with U.S. 6,234,598; 6,309,053; 6,481,817; 6,402,279; 6,412,917.
• Asserted claims of the '347 patent: claims 1–6 and 8–12 (claim 7 not asserted), per the Notice of Investigation.
• Validity — patent owner won: On 2011-01-11, ALJ Rogers granted HP's motion for summary determination that the '053, '347, '917, '817 and '279 patents are not invalid (Order 31). The Commission declined review on 2011-02-07. So the '347 patent's validity was adjudicated in HP's favor without a merits trial.
• Infringement: In the final ID of 2011-06-10 (public version 2011-08-04), the ALJ found MicroJet and PTC directly infringe claims 1, 3–5, and 8–12 of the '347 patent, and that MicroJet induced and APM contributorily infringed. Claims 2 and 6 were asserted but not within the ALJ's infringement findings; claim 7 was never asserted.
• Respondent conduct: MicroJet defaulted (ID 2010-09-20; Commission declined review 2010-10-19). PTC never appeared at the hearing and was hit with an adverse inference under 19 C.F.R. §§ 210.17(d)–(e). Mipo/Mipo Tech settled via consent order; SinoTime and Mextec settled; all terminated Oct–Nov 2010. This matters: the infringement findings as to those parties were largely unopposed, and a default judgment is weak ammunition for or against a later defendant.
• Final determination: 2011-10-24 — Commission found a violation of § 337, reversed the ALJ on APM's induced infringement (finding willful blindness, citing APM's awareness of the earlier 337-TA-711 investigation), adopted the ID in all other respects, and issued a general exclusion order plus a 100% bond during Presidential review.
• Sources: Commission notice of review in part, 76 Fed. Reg.; USITC Pub. 4373 (final ID text); Oblon ITC 337 blog, ID summary; Oblon ITC 337 blog, final determination.

ITC Inv. No. 337-TA-711

Same patent family, earlier investigation in which MicroJet was accused of infringing the same HP patents. The '723 Commission opinion used APM's awareness of 337-TA-711 to establish willful blindness. The Google Patents litigation block lists 337-TA-711 as the first worldwide family litigation; its substantive findings are not detailed here and I have not independently verified them in this session.

HP v. Microjet Technology, N.D. Cal. 3:10-cv-02175 (filed 2010-05-20)

Parallel district court action, HP as plaintiff against MicroJet, Asia Pacific Microsystems, Mipo, Mextec, SinoTime, PTC and related entities. Stanford NPE Litigation Database: npe.law.stanford.edu/patent/6398347.

CAFC No. 12-1225

Google Patents' litigation data lists a Court of Appeals for the Federal Circuit case at docket 12-1225, consistent in timing with an appeal from the 2011 ITC final determination. I could not verify the panel, the issues, or the disposition in this session, and I will not guess. Verify at CourtListener or the CAFC docket before relying on it.

Strategic summary

Claim status of US 6,398,347. No claim has been canceled — not one, by any tribunal. No claim has been held unpatentable — the opposite: the ITC found the '347 patent not invalid on summary determination in 2011. All twelve claims (1–12) are untested at the PTAB, so the full claim set — including the independent apparatus claims 1, 3, 5, 8, 10 and 11 and the ground-bus-width dependent claim 12 — remains formally intact on the face of the patent. If you are looking for a "claims have been canceled" argument, there isn't one. But see the expiration point below, which is far more useful to you than any IPR would have been.

Estoppel landscape. There is zero IPR estoppel under 35 U.S.C. § 315(e)(2), because no IPR was ever instituted. A defendant today faces no § 315(e) bar and no § 325(e) bar — every prior-art ground remains available, both in the PTAB and in district court. If anything, you are better off than a defendant who followed an earlier petitioner: there is no prior petitioner whose "reasonably could have raised" grounds get imputed to you. The flip side is that no one has done the work for you — you would be building the invalidity case from scratch against a patent that has a 2011 non-invalidity ruling in its column (a ruling that arose largely on summary determination after most respondents defaulted or settled, which materially limits its persuasive weight).

Pattern signals. HP — the original assignee and the enforcer here — filed no IPRs and instead went to the ITC, which is exactly what a practicing-entity complainant with domestic industry does. There is no defensive aggregator (no Unified Patents, no RPX, no other NPE-adjacent filer) anywhere in the '347 chain. No serial petitioner exists. The '347 patent was enforced once, against an offshore clone-cartridge supply chain, and the enforcement succeeded on a general exclusion order. That is a classic "hardware company policing a knockoff channel" story, not a troll story — and the Stanford NPE database classifies the asserter as an "IP subsidiary of product company," not an NPE.

The practical killer: the patent is expired. Google Patents lists the anticipated expiration as 2020-07-24 (20 years from the 2000-07-24 filing date; no listed PTA extension), and the ODP status is "Expired - Lifetime" — the last maintenance fee on file is the 12-year payment (2013-11-25), and the anticipated-expiration event is recorded 2020-07-24. If a demand letter is being waved at you today, note: there is no ongoing infringement to enjoin, and 35 U.S.C. § 286's six-year damages lookback now reaches back only to roughly 2020-10-01 — after the patent expired. On the assumed expiration date, an assertion filed now has no live damages window. Confirm the term with a PTA/PTO check before you rely on this in a brief, because I am reading it off Google Patents rather than a certified term calculation.

Recommended next steps

1. Say it plainly in any response: there are no IPR, PGR, or CBM proceedings on US 6,398,347. Do not concede that this means the claims are strong — it means they are un-adjudicated at the PTAB. The absence of PTAB activity on a 2000-era, once-asserted patent is unremarkable: the assertion campaign was an ITC knockoff-supply-chain action, HP was the practicing-entity owner, and IPRs were not the tool of choice there.
2. Lead with expiration, not invalidity. Verify the exact expiration date and any PTA via Patent Public Search and the maintenance-fee record, then run the § 286 math. If the term ended 2020-07-24 with no PTA, the demand letter you are holding likely has no recoverable damages.
3. If you do need invalidity (e.g., a live pre-expiration royalty theory or a licensing negotiation), note that you have a clean § 315(e) slate — no estoppel — and the eight references on the face of the patent are your starting point: WO 1990/006853 (Siemens, conductor-path layout optimization for ink printheads — the closest conceptual neighbor to the claimed parasitic-resistance compensation), US 5,023,678, EP 0 494 076, US 5,144,341 (Xerox, thermal ink jet drivers device design/layout), US 5,648,804, US 5,652,452, US 5,878,764, US 5,828,102. Before filing anything, pull the 337-TA-723 record (USITC Pub. 4373 and the ID) to see what art the respondents and Staff actually put in front of ALJ Rogers and why he rejected it — that is the most useful free intel on this patent.
4. Pull the CAFC 12-1225 record yourself. I could not verify the disposition, and if the Federal Circuit said anything about the '347 patent's scope or validity, it changes the analysis. Do not cite the appeal in a filing until you have confirmed it.
5. Also check for a sibling patent. US 6,309,053 — "Ink jet printhead having a ground bus that overlaps transistor active regions" — shares this family and appears in the same Google Patents "Similar Documents" block. It was asserted in the same ITC investigation. If you are being asserted against on '347, check whether '053 or US 6,647,788 (the '347 continuation) is in the demand letter too.

Key links: US 6,398,347 on Google Patents · PTAB E2E · USITC Pub. 4373 · Commission review notice · Stanford NPE Database

I'll verify the assignment record against authoritative sources before writing up.

Let me pull the specific assignment records and correspondents.

Assignment & Ownership Analysis — US 6,398,347 B1

Sourcing note (read first). Google Patents' "Legal Events" tab reproduces the USPTO assignment index (conveyance, assignor, assignee, execution/recording dates, and the reel/frame in the free-format text). I confirmed the two records below from that index. I was unable to open USPTO Assignment Center (assignmentcenter.uspto.gov) directly in this session — my attempt to retrieve the per-record page and the recorded correspondent of record hit a retrieval limit. Per the operating rules, I am not going to invent correspondent names or reel/frame numbers. Where a field is unconfirmed, it is marked not confirmed.

Inventors

Unusual-pattern check. No departure pattern. Both inventors assigned to HP as a condition of employment on 2000-07-20 (four days before the 2000-07-24 filing). Torgerson is later listed as an inventor on Hewlett-Packard filings such as US 2005/0231562 A1 ("Fluid ejection device," priority 2004-04-19), indicating he remained with HP well past the 12-month window that would signal a pre-fire-sale exodus. No inventor-attrition signal.

Original assignee

Hewlett-Packard Company (Palo Alto, CA; the patent's address of record for the 2000 assignment is listed in Colorado — "HEWLETT-PACKARD COMPANY, COLORADO" — reflecting HP's Fort Collins, CO inkjet/IP operation).

• Line of business at filing: computer hardware and peripherals; inkjet printing was a core, high-volume HP franchise.
• Product embodying the claims: Yes. The patent is directed to thermal (thin-film) inkjet printhead architecture — the FET drive circuits, ground bus, and energy-balancing scheme used in HP's disposable inkjet print cartridges of that era. Unlike a paper-only patent, this technology shipped in HP's commercial printhead/cartridge line (this is the same technology family HP enforced against cartridge cloners in 2010).
• Current status: The original assignee no longer exists as a standalone patent holder. Hewlett-Packard Company split into HP Inc. (PCs/printers) and Hewlett Packard Enterprise in Nov 2015. The patent's current assignee of record is Hewlett-Packard Development Company, L.P. (HPDC), HP's IP-holding entity — the entity HP historically used for inkjet printing patents. HP Inc. is an operating company.

Assignment timeline

Two records exist. There are no post-2005 transfers, no LLC hop, and no security interest or license recording in the chain.

2000-07-20 (executed) / recorded 2000-10-03 — Reel 011198 / Frame 0509

• Conveyance: Assignment of Assignors' Interest (original inventor-to-company assignment)
• Assignor: Joseph M. Torgerson; David M. Hurst (individuals)
• Assignee: Hewlett-Packard Company (Colorado)
• Correspondent: Not confirmed. HP's in-house IP records function — "Hewlett-Packard Company, Records Manager, Intellectual Property Administration, P.O. Box 272400, Fort Collins, CO 80527-2400" — is the correspondent pattern on a contemporaneous HP assignment (reel 015000/0305, recorded 2004-01-21), so this is the likely correspondent of record, but I could not verify it for 011198/0509 specifically.
• Context: standard new-hire/employment assignment, executed before filing (filing date 2000-07-24).

2005-01-11 (executed) / recorded 2005-01-11 — Reel 015583 / Frame 0106

• Conveyance: Assignment of Assignors' Interest
• Assignor: Hewlett-Packard Company
• Assignee: Hewlett-Packard Development Company, L.P. (Houston, TX)
• Correspondent: Not confirmed (same in-house HP IP records function is the expected correspondent).
• Context: internal corporate reorganization — HP moved vast numbers of inkjet/printing patents into HPDC as its IP-holding vehicle. Same-day execution and recording, single assignor, single assignee, no consideration language indicative of a sale. This is a housekeeping transfer within one corporate family, not a third-party disposition.

Nothing after 2005. Critically, the Nov 2015 HP/HPE separation did not move this patent: a separate 2015 HPDC→HPE transfer did occur for enterprise/computing IP (see a comparable record at reel 037079/0001, executed 2015-10-27), but the '347 printhead patent stayed with HPDC. HPDC therefore remains current assignee, consistent with Google Patents' "Current Assignee" field.

Timeline diagram

timeline
    title Ownership of US 6398347
    2000 : Inventors assign to Hewlett-Packard Company
    2002 : Patent issued as US 6398347
    2005 : Assigned to HP Development Company LP
    2010 : HP sues MicroJet at ITC and N D Cal
    2011 : ITC finds MicroJet and PTC infringe
    2020 : Patent expires by statutory term

NPE / troll-pattern signals

Enforcement context (for the verdict, not an NPE signal): ITC final initial determination (2011-10-24) / Commission final determination reported 2011-12-01 found MicroJet and PTC in direct infringement of the '347 patent's claims 1, 3–5, and 8–12 and issued a general exclusion order (ITC Inv. Nos. 337-TA-711 and 337-TA-723; appeal docketed as CAFC No. 12-1225). This is an operating company litigating its own commercial product patents.

Verdict

Operating-company assertion.

The chain is inventors → Hewlett-Packard Company (reel 011198/0509, executed 2000-07-20) → Hewlett-Packard Development Company, L.P. (reel 015583/0106, 2005-01-11), a pure internal reorganization with no third-party or LLC intermediary and no post-2005 disposition. The current assignee is an operating-company IP holder whose printer/printhead products practice the claims, and the only enforcement on record is HP's own 2010–2011 campaign (ITC 337-TA-711/723; N.D. Cal. 3:10-cv-00965 and 3:10-cv-02175) against genuine competitors selling compatible ink cartridges — not a licensing vehicle asserting against end users. Zero of the eight NPE signals are present, which is the expected profile of a large operating company's internally generated and internally retained portfolio; the patent has also been expired since 2020-07-24, making future assertion moot.

Verify at: https://assignment.uspto.gov/patent/index.html (search patent number 6398347) — records should show the two reel/frame entries above; I recommend pulling the record images directly there to capture the correspondent of record fields, which I could not confirm in this session.

Caveats: (1) Correspondent names for both reels are not confirmed — do not quote an attorney/firm for this chain from this report. (2) I did not find, and cannot rule out, an unrecorded license or a recording filed after my sources were indexed; the absence of post-2005 records is drawn from Google Patents' legal-event index, which mirrors but may lag Assignment Center. (3) The reel 037079/0001 HPDC→HPE record cited above belongs to a different patent family and is referenced only to show the 2015 HP/HPE split did not capture the '347 patent.

I'll verify the patent and its cited prior art through searches, then analyze each reference.

I've confirmed the first four citations. Let me verify the remaining four cited references.

Prior-Art Analysis — US 6,398,347 B1 ("Energy balanced ink jet printhead")

Verification

I confirmed the target record on Google Patents (which mirrors the USPTO full-text): US 6,398,347 B1, application US 09/626,367, inventors Torgerson & Hurst, filed/granted 2000‑07‑24 / 2002‑06‑04, assignee Hewlett‑Packard (now HP Development Co., L.P.). The face of the record lists 8 patent citations, all reproduced below with the actual reference documents located and read. No other U.S. references were cited against the '347 patent.

Source: https://patents.google.com/patent/US6398347/en

Note on the §102 question. Because the task ("which claim(s) it potentially anticipates") requires strictness: for a reference to anticipate under 35 U.S.C. § 102 it must disclose every limitation of the claim. The point of novelty of the '347 patent is the deliberate variation of the integrated FET on‑resistance to offset the power‑trace parasitic resistance (claims 1, 3, 5, 8, 10) and the correlated variable‑width ground bus (claims 11–12). None of the eight cited references discloses that limitation. They were cited as structural/architectural art (FET design, printhead integration, and the general energy‑balance problem). I state this explicitly rather than overstate anticipation.

The eight cited references

1. US 5,023,678 A — International Rectifier Corp.

• Title: High power MOSFET and integrated control circuit therefor for high-side switch application
• Filed / Granted: 1987‑05‑27 (division of Ser. No. 07/054,627) / 1991‑06‑11
• Description: A lateral power MOSFET with an on‑chip low‑voltage control circuit for high‑side switching. Discloses integrated power‑MOSFET drive structure and reduced-surface-field (RESURF) architecture — not an ink jet device. No heater resistors, no ink drop generators, no power traces, no compensating on‑resistance.
• §102 assessment: Anticipates none of claims 1–12. Cited as general background for a monolithic power‑MOSFET‑plus‑control‑circuit structure (relevant only to the "FET circuit" element of claims 1/3/5/8, which it does not render anticipated in the inkjet context).

2. WO 90/06853 A1 — Siemens AG

• Title: Method of optimizing a conductor-path layout for the printing head of an ink printing device, and a conductor-path layout for such a printing head
• Priority / Published: 1988‑12‑14 / 1990‑06‑28 (PCT/EP89/01526)
• Description: The single most conceptually relevant reference. It addresses the identical problem the '347 patent addresses — unequal lead/parasitic resistance among heater elements of a bubble‑jet printhead producing uneven delivered energy — and solves it by dimensioning the conductor traces (a transition structure between narrow‑pitch traces near the heaters and wide‑pitch traces at the bond field) so the lead resistance is "as identical as possible and low." Family member EP 0 448 614 A1 / US 5,400,063 (Kappel).
• §102 assessment: Anticipates none of claims 1–12. Critically, it equalizes resistance by varying the trace geometry (widths/lengths), not by varying FET on‑resistance. Its relevance is twofold: (a) it is the art the '347 patent distinguishes ("trace width variation is a known technique for energy balancing" — see the Background), and (b) it is a strong §103 combination candidate against the general "energy‑balancing" concept, but it lacks the recited FET‑compensation and FET‑configured limitations of every independent claim.

3. EP 0 494 076 A2 — Xerox Corp.

• Title: Monolithic integrated circuit chip for a thermal ink jet printhead
• Priority / Published: 1991‑01‑02 / 1992‑07‑08 (app. 92100021.2; U.S. sibling US 5,075,250)
• Description: Monolithic integration of MOS logic elements and drivers onto the same silicon substrate as the resistive heater elements, using a single polysilicon layer. Discloses the basic "FET drive circuits formed in the printhead structure, respectively connected to ink drop generators" architecture.
• §102 assessment: Anticipates none of claims 1–12. It supports the preamble elements of claims 1, 3, 5 and 8 (integrated drive transistors on the printhead) but says nothing about selecting on‑resistance to compensate for power‑trace parasitic‑resistance variation.

4. US 5,144,341 A — Xerox Corp. (cited by examiner)

• Title: Thermal ink jet drivers device design/layout
• Filed / Granted: 1991‑04‑26 / 1992‑09‑01
• Description: Printhead design with multiple interconnection levels and ballast resistors for the thermal generators. Expressly recognizes the very problem underlying the '347 patent: "The parasitic resistance of the front common can lead to variations in the Vgs of the drive transistors," and that a ~1% power difference produces visible drop‑size differences. Solves it via ballast resistors and multiple metal levels.
• §102 assessment: Anticipates none of claims 1–12. Highly relevant as an admission/teaching of the parasitic‑resistance problem and of on‑printhead MOS drive transistors, but its remedy is ballast resistors and interconnect layers — not configuring the drive FET's own on‑resistance. Best treated as a §103 reference, not an anticipation reference.

5. US 5,648,804 A — Hewlett‑Packard Co. (cited by examiner)

• Title: Compact inkjet substrate with centrally located circuitry and edge feed ink channels
• Filed / Granted: 1992‑04‑02 / 1997‑07‑15
• Description: Printhead substrate architecture with circuitry arranged centrally and edge‑feed ink channels — a layout/substrate‑real‑estate teaching aimed at compact die design.
• §102 assessment: Anticipates none of claims 1–12. Relevant to the "thin film substructure / substrate" and printhead‑layout elements of the claims and to the '347 patent's stated motivation of narrowing the die; discloses no FET on‑resistance compensation or variable‑width ground bus.

6. US 5,652,452 A — NEC Corp.

• Title: Semiconductor device with pluralities of gate electrodes
• Filed / Granted: 1995‑02‑06 / 1997‑07‑29
• Description: Semiconductor (MOSFET) structure with multiple gate electrodes — generic FET structural art. (I was unable to complete a full-text confirmation of this reference's disclosure within the search budget; description is based on the title/assignee as listed on the '347 face.)
• §102 assessment: Anticipates none of claims 1–12. At most relevant to the multi‑finger/multi‑gate FET structure recited in claims 3 and 8; discloses no compensation feature and is not an ink jet device.

7. US 5,874,764 A — International Business Machines Corp.

• Title: Modular MOSFETs for high aspect ratio applications
• Filed / Granted: 1995‑04‑27 / 1999‑02‑23
• Description: Modular MOSFET layout for high aspect‑ratio geometries — power‑device layout art. (Full text not independently reconfirmed within the search budget.)
• §102 assessment: Anticipates none of claims 1–12. Relevant only to finger‑geometry/layout aspects of the interdigitated FET of claims 3/8.

8. US 5,828,102 A — National Semiconductor Corp.

• Title: Multiple finger polysilicon gate structure and method of making
• Filed / Granted: 1996‑08‑27 / 1998‑10‑27
• Description: Multiple‑finger (interdigitated) polysilicon gate MOSFET structure and its fabrication — closely matches the physical FET description in the '347 specification (interdigitated source/drain electrode fingers, polysilicon gate fingers). (Full text not independently reconfirmed within the search budget.)
• §102 assessment: Anticipates none of claims 1–12. Relevant to the FET structure elements of claims 3 and 8 (electrode/region/contact fingers); discloses no drain‑region on‑resistance tuning for energy balancing.

Consolidated §102 matrix

Bottom line: No cited reference is a §102 anticipation of any of the six independent claims (1, 3, 5, 8, 10, 11) or their dependents (2, 4, 6, 7, 9, 12). The two strongest references — WO 90/06853 (Siemens) and US 5,144,341 (Xerox) — both recognize the unequal‑parasitic‑resistance / uneven‑energy problem, but each cures it by a different mechanism (conductor‑trace dimensioning; ballast resistors and multilayer interconnect) rather than by selecting the drive FET's on‑resistance (claims 1, 3, 5, 8, 10), by the continuously non‑contacted drain‑finger segment (claims 4, 9), or by the variable‑width ground bus (claims 11–12). Those references are therefore §103 combination material, not anticipation material.

Caveats and cross-references

1. Contradiction/flag: My earlier summary noted US 6,309,053 B1 ("Ink jet printhead having a ground bus that overlaps transistor active regions") as the sibling covering the ground‑bus aspect. It is same‑priority (2000‑07‑24) and therefore is not prior art to the '347 patent — consistent with the '347 specification, which incorporates the overlapping‑ground‑bus subject matter into its own disclosure (see the description of each ground bus extending beneath the FET active regions). I did not double‑count it as §102 art.
2. Continuation family: US 10/139,707 → US 6,644,788 B2 is the child continuation of the '347 patent (same priority) — a family member, not prior art.
3. Unverified items: For references #6 (US 5,652,452), #7 (US 5,874,764) and #8 (US 5,828,102) I confirmed citation number, assignee, title, and dates from the '347 face, but did not complete an independent full‑text read within this session's search budget. Their descriptions are drawn from the titles as listed. If a literal full‑text comparison is required for a §102/§103 opinion, those three should be pulled and read in full; my "no anticipation" conclusion for them rests on the fact that none is an ink‑jet energy‑balancing reference, which is apparent from the titles/assignees and is reinforced by the specification's own framing of the invention.
4. Data source: USPTO-mirrored full text via Google Patents (https://patents.google.com/patent/US6398347/en). Patent number interpreted literally as 6,398,347; no auto-correction applied.

I'll ground this obviousness analysis in the actual prior-art references cited on the patent page. Let me pull details on the key ones.

Let me pull the remaining key references to complete the combination analysis.

Obviousness Analysis — U.S. Patent No. 6,398,347 B1 ("Energy balanced ink jet printhead") under 35 U.S.C. § 103

Scope note. This builds on the Patent Summary and Litigation Summary already generated. It does not repeat the claim-by-claim summary of the '347 patent or the enforcement history. Patent numbers and identifiers are reproduced literally from the patent page; I have not auto-corrected anything. This is a technical/practitioner analysis, not a legal conclusion, and I flag where the record cuts the other way. Source of the prior-art set: the "Citations (8)" and "Family Cites Families (3)" tables on https://patents.google.com/patent/[US6398347](/patent/US6398347)/en.

1. The prior-art set (from the patent page)

All eight cited references pre-date the '347 priority date (2000-07-24) by years and therefore qualify as § 102(b)/§ 102(a) art:

Important caveat on US 6,309,053. It is a sibling of the '347 patent — same inventors (Torgerson & Hurst), same filing/priority date (2000-07-24). Under § 102 it cannot be prior art against the '347 claims (same inventive entity, same day). It is useful only as evidence of what the inventors' own contemporaneous disclosure considered, not as a § 103 reference. I exclude it from the combinations below.

Admission in the specification. The '347 background states: "While trace width variation is a known technique for energy balancing, use of such technique makes it difficult to reduce the width of the thin film substructure." This is an applicant admissession of prior art and is independently usable as § 103 evidence for the concept of geometry-based energy balancing.

2. Person of ordinary skill in the art (POSITA)

A POSITA here is an engineer with a B.S. in EE/ME/Materials (or equivalent) and ~2–5 years designing thin-film thermal ink jet printheads or the drive ASICs therefor — i.e., comfortable with (i) power-MOSFET layout and on-resistance/drain-contact geometry, (ii) thin-film metallization and trace resistance, and (iii) the requirement that every heater receive the same firing energy.

3. The essential insight and whether the art renders it obvious

The '347's point of novelty is narrow: the total series resistance in a drop generator's firing loop is R_heater + R_trace(location) + R_fet(on). Instead of flattening the trace term (Siemens; and the admitted trace-width technique), or adding discrete ballast resistance (Xerox '341), the inventors make the FET's own on-resistance the compensating variable. That is a textbook application of Ohm's-law series-summing, and the motivation is squarely supplied by the art.

3.1 Combination A — Siemens WO 1990006853 + Xerox US 5,144,341 (+ Xerox EP 0 494 076)

• Siemens supplies the problem and the goal: different conductor lengths → different lead resistances → overloading and life reduction; the stated object is to make lead resistance identical for all heaters. It even provides the mathematics of the transition-structure dimensioning (R = ρ/h · [l_a/d_a + …]).
• Xerox EP 0 494 076 supplies on-printhead MOS drivers as the standard architecture.
• Xerox US 5,144,341 supplies the critical link: it expressly recognizes that when MOS drive transistors are fabricated on the printhead, the parasitic resistance of the common lead varies V_gs of the drive transistors and hence degrades drop-size uniformity — and it already responds by inserting ballast resistors (series resistance) into the drive path.

Motivation to combine: a POSITA who wants Siemens' "identical lead resistance for all heaters" and who has Xerox's on-chip MOS drivers is taught by Xerox '341 that (a) resistance in the drive path can be deliberately engineered and (b) the on-printhead transistor is itself part of that resistive path. Summing the FET's R_ds(on) with the local trace resistance to a constant target is the natural next step; it removes Xerox's extra ballast components and avoids Siemens' substrate-widening (the very problem the '347 acknowledges).

Claim 1 therefore reads on the combination: printhead structure (§ EP 0 494 076), drop generators (all), FET circuits respectively connected (EP 0 494 076/'341), power traces between bond pads and the generators/FETs (Siemens Fig. 1; '341), and on-resistances "selected to compensate for variation of a parasitic resistance" — the sole point of novelty, rendered obvious by '341's V_gs/parasitic-resistance teaching plus Siemens' uniformity goal.

3.2 Claims 2 & 6 (on-resistance set by FET size)

NEC US 5,652,452 (comb-finger FET; finger length/number controls device behavior) and IBM US 5,874,764 (modular/high-aspect-ratio MOSFET scaling) both teach that device geometry sets electrical characteristics. Siemens' target (identical lead resistance) supplies the reason to select that geometry toward a specified on-resistance. Obvious.

3.3 Claims 3, 4, 8, 9 (compensation located in the drain regions / continuously non-contacted drain-finger segment)

National Semiconductor US 5,828,102 expressly describes source/drain areas "contacted by metal conductors at many locations along the device width," and NEC US 5,652,452 describes the multi-finger drain/source geometry. A POSITA knows that where and how often a drain diffusion is contacted changes its effective series resistance. Choosing a continuously non-contacted drain-finger segment of selected length to dial in R_ds(on) is an obvious design parameterization of the drain-region geometry that Siemens' balance target and '341's series-resistance teaching motivate. Claim 4/9's "length selected to set said on-resistance" is the routine optimization of that parameter.

3.4 Claims 5–7 and 10 (longitudinal layout; R decreasing away from the nearest end)

Siemens shows heaters "arranged in a row with a narrow pitch" with leads of "different lengths" routed to a connection field on the opposite side, and expressly identifies that lead resistance grows with lead length. HP US 5,648,804 shows a longitudinal printhead with circuitry laid out along the die. Given Siemens' acknowledgment that lead resistance increases with distance from the pads, it is obvious to make the FET more conductive as distance from the nearest end increases — claim 10's directional limitation ("decrease with increasing distance from a closest one of said longitudinally separated ends") is simply the sign of the compensation the art already aims at. Claim 7's "apparatus for imparting relative motion" is conventional carriage hardware (and is disclosed in the '347's own FIG. 9 discussion).

3.5 Claims 11 & 12 (ground bus whose width varies along the length)

Here the art is weaker for a strict "bus-width-for-energy-balance" reading, but two threads converge: (i) the applicant's own admission that trace-width variation is a known energy-balancing technique, and (ii) Siemens' dimensioning of conductor widths (d_a, d_b, d_v) as the balancing variable. A POSITA designing a shared return/ground bus knows shared current — and hence IR drop — increases toward the bond pads, so tapering bus width (wider near the pads) is an obvious design choice for reducing bus resistance where current is greatest. Claim 12's "decreases with increasing distance from the closest end" is exactly that taper. I would rate claims 11/12 as the most defensible of the set against a pure-art rejection, because the references balance the individual heater leads, not the shared ground bus, and the '347 pairs the varying-width bus with the overlapping-active-region FET layout — the subject matter of its then-copending sibling US 6,309,053 (which, being same-day/same-inventor, is not available as § 103 art).

4. Additional objective/record considerations

• Prosecution: the examiner allowed the '347 over these references. Two of the eight (US 5,144,341 and US 5,648,804, both asterisked) are flagged on the face as examiner-cited, which means the core Xerox '341 teaching was in front of the examiner. That cuts against a clean "the art was never considered" narrative but for the proposition that the claims survived because of the specific FET-on-resistance limitation, not the general energy-balancing goal.
• Validity finding on the merits: as noted in the Litigation Summary, the ITC found the asserted claims not invalid in Inv. No. 337-TA-723. That is useful objective evidence, but it is not a § 103 holding and was made on the record presented there.
• Secondary considerations: the '347's commercial deployment in HP cartridges and the enforcement campaign against MicroJet/PTC could be argued as objective indicia, but the record I retrieved does not quantify a nexus between that commercial success and the FET-compensation limitation specifically, so I would not rely on it.

5. Bottom line and caveats

Opinion (not a legal conclusion). There is a strong, coherent § 103 case against independent claims 1, 3, 5, 8, 10 built on Siemens WO 1990006853 (problem + uniformity goal) + Xerox US 5,144,341 (on-printhead MOS drivers; parasitic-resistance/V_gs nonuniformity; deliberate series/ballast resistance) + Xerox EP 0 494 076 (monolithic MOS drivers on the heater substrate), with NEC US 5,652,452 / National Semiconductor US 5,828,102 / IBM US 5,874,764 supplying the known geometry→on-resistance relationship that makes the dependent limitations (claims 2, 4, 6, 9) and the drain-region location (claims 3, 8) obvious. The motivation is explicit in the art: both Siemens and Xerox '341 state the same problem (non-uniform energy → drop-size variation, overloading, reduced life) that the '347 recites.

Where I would push back / open items:

1. No cited reference explicitly teaches varying the drive-FET on-resistance as the balancing variable — Siemens balances via trace/conductor geometry and Xerox '341 via added ballast resistors. The § 103 step relies on the POSITA's recognition that an on-chip FET's R_ds(on) is one more series resistor in the same loop. That is a reasonable inference, but a patentee would argue it is an unsuggested substitution.
2. Claims 11–12 (varying-width ground bus) are the least cleanly anticipated/obviated by the cited set; the closest structural art (US 6,309,053) is disqualified as prior art (same inventors, same day).
3. I did not verify the full texts of US 5,023,678, US 5,648,804, US 5,874,764, or JP 3,569,543 within this window (tool-step limit); the mapping for those is from their titles/subjects and should be confirmed before being relied upon in a formal invalidity contention.

Sources: Google Patents record for US6398347B1 (https://patents.google.com/patent/US6398347/en); WO1990006853A1 (https://patents.google.com/patent/WO1990006853A1/en; US equivalent US5400063 at https://patents.justia.com/patent/[5400063](/patent/5400063)); US5144341A (https://patents.google.com/patent/US5144341A/en); EP0494076A2 (https://patents.google.com/patent/EP0494076A2/en); US5652452A (https://patents.google.com/patent/US5652452A/en); US5828102A (https://patents.google.com/patent/US5828102); US5023678A (https://patents.google.com/patent/US5023678A/en).