Vitronics Corporation v. Conceptronic, Inc.
90 F.3d 1576 (1996)
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Rule of Law:
In patent claim construction, courts must look first to the intrinsic evidence of record—the patent claims, specification, and prosecution history—which is the most significant source of meaning. A court may only resort to extrinsic evidence, such as expert testimony, if the intrinsic evidence is ambiguous, and extrinsic evidence may never be used to vary or contradict the clear meaning derived from the patent documents.
Facts:
- Vitronics Corporation held U.S. Patent No. 4,654,502 ('502 patent) for a method of reflow soldering electronic devices to printed circuit boards using a multi-zone oven.
- The patented method involves moving a circuit board through different heating zones to melt solder and form connections.
- Claim 1 of the patent requires heating the solder to a 'solder reflow temperature' while maintaining the temperature of the electronic devices 'below said solder reflow temperature.'
- The patent's specification describes a preferred embodiment where the solder reaches 210°C, while the devices reach 195°C.
- The specification also notes that the exemplary solders have a 'liquidus temperature' (where they begin to melt) of about 190°C and a 'peak reflow temperature' of about 210°-218°C.
- Conceptronic, Inc. manufactured and sold ovens (the HVC series) that also performed reflow soldering.
- The dispute between Vitronics and Conceptronic centered on the definition of 'solder reflow temperature': Vitronics argued it meant the peak temperature (e.g., 210°C), while Conceptronic argued it meant the lower liquidus temperature (e.g., 183°C or 190°C).
Procedural Posture:
- Vitronics Corporation sued Conceptronic, Inc. in the United States District Court for the District of New Hampshire for patent infringement.
- The parties stipulated before trial that Conceptronic's HVC ovens met all limitations of the patent claim at issue except the one defining 'solder reflow temperature'.
- At trial, the parties presented conflicting interpretations of the term 'solder reflow temperature', supported by evidence including the patent specification and expert testimony.
- After the close of testimony, the district court construed the disputed term in favor of Conceptronic, ruling it meant the lower 'liquidus temperature' (183°C).
- Based on the court's construction, Vitronics conceded it had not presented evidence of infringement.
- The district court entered a judgment as a matter of law in favor of Conceptronic, finding no infringement.
- Vitronics Corporation, as appellant, appealed the judgment to the U.S. Court of Appeals for the Federal Circuit.
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Issue:
Does a court properly construe a patent claim by relying on extrinsic evidence, such as expert testimony, when the intrinsic evidence, including the patent's claims and specification, provides an unambiguous meaning for the disputed term?
Opinions:
Majority - Michel, Circuit Judge.
No. A court may not properly rely on extrinsic evidence to construe a patent claim when the intrinsic evidence unambiguously determines the meaning of a disputed term. The specification of the '502 patent clearly shows that 'solder reflow temperature' refers to the peak reflow temperature, not the liquidus temperature. The patent's preferred embodiment describes a process where the devices are heated to 195°C, which is above the stated liquidus temperature of 190°C. For the claim requirement—that devices remain 'below said solder reflow temperature'—to be met in the preferred embodiment, the 'solder reflow temperature' must be the higher peak temperature (210°C). An interpretation where a patent's preferred embodiment does not fall within the scope of its own claims is rarely, if ever, correct. Because the intrinsic evidence was dispositive, the trial court erred by relying on extrinsic evidence like expert testimony that contradicted the clear meaning found within the patent documents themselves.
Analysis:
This case firmly establishes the hierarchy of evidence in patent claim construction, solidifying the primacy of intrinsic evidence (claims, specification, prosecution history) over extrinsic evidence (expert testimony, articles). By ruling that extrinsic evidence is improper when the patent's public record is clear, the court aimed to promote certainty and predictability, allowing competitors to rely on the patent documents to understand the scope of the invention and design around it. This decision significantly limits the role of the 'battle of the experts' in claim construction hearings, directing trial judges to focus their legal analysis on the patent's own text. The case serves as a foundational guide for how courts must approach the purely legal task of interpreting patent claims.
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