## Facts

- Vitronics Corp. owned U.S. Patent No. 4,654,502, covering a method for reflow soldering surface-mounted devices onto printed circuit boards by moving boards on a conveyor through a multizone oven.
- The method heats solder paste so it melts and forms connections while keeping the devices themselves below the “solder reflow temperature,” using a temperature differential between solder and device.
- The patent specification described solder with a “liquidus temperature” (the temperature at which solder begins to melt) of about 190°C and a “peak reflow temperature” of about 210–218°C, and described heating the board and solder to about 210°C in a preferred embodiment.
- Vitronics sued Conceptronics, Inc. in the U.S. District Court for the District of New Hampshire, alleging that Conceptronics’ ovens infringed claim 1 of the ’502 patent.
- The case turned on the meaning of the claim term “solder reflow temperature.”
- The district court delayed claim construction until after testimony. At that point, Vitronics argued “solder reflow temperature” meant the peak reflow temperature described in the specification.
- Conceptronics argued the term meant the liquidus temperature, relying on a technical paper written by a former Vitronics employee and testimony from an expert witness.
- The district court construed “solder reflow temperature” as the liquidus temperature and did not clearly state what evidence drove that construction.
- Based on the court’s construction, Vitronics conceded that Conceptronics was entitled to judgment as a matter of law (JMOL) of noninfringement, and Vitronics appealed.

## Issues

1. What sources should control patent claim construction—claim language, specification, and prosecution history (intrinsic evidence) or materials such as expert testimony and technical articles (extrinsic evidence)?
2. Under the proper method of claim construction, does “solder reflow temperature” in claim 1 refer to the peak reflow temperature described in the patent or the solder’s liquidus temperature?
3. If the district court used an incorrect construction of “solder reflow temperature,” can the JMOL of noninfringement stand?

## Decision

- The Federal Circuit reversed the JMOL and remanded for further proceedings.
- The court held that claim construction should be based first on the intrinsic record: the claims, the specification, and (if in evidence) the prosecution history.
- The court concluded that the intrinsic record, especially the specification’s description of the invention and preferred embodiment, supported Vitronics’ construction of “solder reflow temperature” as a peak reflow temperature rather than merely the liquidus temperature.
- Because the patent record was clear on the point, the district court should not have relied on extrinsic materials to reach a conflicting meaning.
- Since the JMOL of noninfringement followed from the erroneous construction, it could not remain in place.

## Legal Principles

- Claim construction is a question of law for the court and is reviewed de novo on appeal.
- Courts should look first to intrinsic evidence of record: (1) the claim language, (2) the specification, and (3) the prosecution history when available.
- The specification is the best guide to the meaning of disputed terms and can define claim terms expressly or by implication.
- The prosecution history can inform the meaning of claim language by showing how the applicant and the Patent and Trademark Office addressed claim scope during examination.
- Extrinsic evidence (such as expert testimony, inventor testimony, dictionaries, and technical writings) is generally less reliable than the patent and its file history and may be used to help the court understand the technology, not to alter claim meaning.
- When the public patent record unambiguously sets out claim scope, reliance on extrinsic evidence to reach a different construction is improper.
- Claim construction should protect the public’s ability to rely on the patent’s public record rather than shifting claim scope based on materials outside that record.

## Conclusion

The Federal Circuit held that the district court erred by construing “solder reflow temperature” as the solder’s liquidus temperature based on extrinsic sources when the intrinsic record, particularly the specification, supported a peak reflow temperature meaning. Because the JMOL of noninfringement rested on that faulty construction, the court reversed and remanded.


Vitronics Corp. v. Conceptronics, Inc., 90 F.3d 1576 (1996)