In a December 22, 2011 opinion, the Federal Circuit denied patent-holding company ICHL LLC’s attempt to keep its patent suit against Sony Electronics, Inc. and Lenovo, Inc. alive. The asserted patent, U.S. Patent No. 4,884,631, covers a heat sink assembly for cooling electronic components such as microprocessors. The central dispute on appeal was whether the “top plate” and “fin structures,” recited in the asserted claims as separate elements, were necessarily structurally distinct, or whether they could be met by an integrally formed structure. The Federal Circuit affirmed the district court’s construction which required that the elements be structurally distinct. The parties had stipulated to noninfringement under such a construction. The court’s decision rested on three grounds. First, the district court’s construction was supported by the claims’ plain language. The claims recited the “top plate” and “fin structure” as separate elements, in which the top plate contains a surface “for receiving fin structures,” and in which the fin structures are “bonded to” the second surface of the top plate. In the court’s view: “[w]hen one structure is bonded to a second structure, those structures are plainly separate to begin with and are not integrally [formed].” Second, the specification disclosed that the patented heat sink assembly contains fin structures that are bonded to, affixed to, or mounted on a surface of the top plate. Finally, the specification disparaged prior art extruded heat sinks as being unable to achieve optimal parameters.
The problem that ICHL faced in this case can often be avoided by careful drafting when the integral / separate distinction is not a critical aspect of the invention. In such cases, patent drafters may want to note in the specification that structures disclosed as being separately formed can, in other embodiments, be integrally formed and vice versa. Similarly, when drafting claims, it may be desirable to avoid language (such as references to “bonding”) that implies that two claim elements are necessarily structurally distinct. The doctrine of claim differentiation can also be used to help prevent unintentional narrowing of claim scope, e.g., adding a dependent claim which recites that two elements are “integrally formed.”