PTAB

IPR2021-00168

Microchip Technology Inc v. Bell Semiconductor LLC

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Petition
petition

1. Case Identification

2. Patent Overview

  • Title: Method of Making Leadframe By Mechanical Processing
  • Brief Description: The ’007 patent describes methods for manufacturing surface-mount semiconductor devices. The disclosed invention involves a mechanical punch-and-stamp process to create leadframes and a two-stage cutting process using two cutters of different thicknesses for singulating (dicing) the packaged devices, which allegedly reduces the formation of metal burrs compared to prior art methods.

3. Grounds for Unpatentability

Ground 1: Anticipation of Claims 1, 3-4 by Matsuo

  • Prior Art Relied Upon: Matsuo (Japanese Publication 2001-77263)
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Matsuo, which predates the ’007 patent, discloses every element of claims 1, 3, and 4. Matsuo is directed to the same problem of preventing burrs during the singulation of resin-sealed semiconductor packages. It explicitly teaches a two-stage cutting method where a first rotary blade (thicker "second cutter") makes a shallow partial cut or groove, and then a second rotary blade (thinner "first cutter") makes a full cut at the same position to separate the device. Petitioner asserted this directly maps to the limitations of independent claim 1 regarding two cutters of different thicknesses performing partial and full cuts. The sequence taught by Matsuo—forming the partial groove first and then the full cut—was argued to anticipate dependent claim 3.
    • Key Aspects: Petitioner contended that Matsuo also discloses preparing the leadframe from an electroconductive material of uniform thickness, anticipating claim 4.

Ground 2: Obviousness of Claims 5-7 over Matsuo in view of Higuchi

  • Prior Art Relied Upon: Matsuo (Japanese Publication 2001-77263) and Higuchi (Japanese Publication JPH09-102573A)
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner asserted that Matsuo provides a base method for packaging chips on a leadframe and singulating them. Claims 5-7 add limitations related to the leadframe preparation itself: a three-step process of "first punching, stamping and second punching" to form the leadframe. Petitioner argued that Higuchi teaches this precise method for manufacturing high-density leadframes. Higuchi discloses first punching to create openings, then coining (stamping) to thin the tips of the inner leads, and finally a second punching step to remove a connecting piece used for stability during processing.
    • Motivation to Combine: A Person of Ordinary Skill in the Art (POSITA) would have been motivated to combine these references. Matsuo acknowledged a market demand for higher-density semiconductor devices. Higuchi taught a method to create such higher-density leadframes with precise, non-deformed inner leads. Therefore, a POSITA would logically apply Higuchi's superior leadframe fabrication method to produce a leadframe for use in Matsuo's packaging and cutting process to meet this known market need.
    • Expectation of Success: The combination was asserted to be predictable. Both references concern the fabrication of quad flat lead frames for semiconductor devices. Applying Higuchi's punch/stamp/punch process to create the leadframe used in Matsuo's process was presented as a straightforward application of a known technique to improve a similar device, well within the skill of a POSITA.

Ground 3: Obviousness of Claims 1-4 over Perez in view of Matsuo

  • Prior Art Relied Upon: Perez (Patent 6,965,157) and Matsuo (Japanese Publication 2001-77263)

  • Core Argument for this Ground:

    • Prior Art Mapping: Petitioner contended that Perez discloses a method of manufacturing a semiconductor package that meets most limitations of claim 1, including patterning a leadframe from a metal plate, mounting a die, and encapsulating the components in a plastic body. However, Perez teaches singulating the final package using conventional methods like die-stamping. Matsuo, as detailed in Ground 1, teaches an improved two-blade rotary cutting method (a thick blade for a partial cut, a thin blade for a full cut) specifically to overcome the known problems of resin chipping and burr formation associated with conventional cutting.
    • Motivation to Combine: A POSITA would have been motivated to replace the conventional singulation step in Perez with the improved cutting method from Matsuo. Matsuo explicitly addresses the deficiencies (e.g., resin chipping) of older cutting techniques like those used in Perez. A POSITA seeking to improve the yield and reliability of the final product in Perez would have looked to known solutions like Matsuo to achieve a cleaner cut with fewer defects.
    • Expectation of Success: Petitioner argued a POSITA would have had a high expectation of success. The combination represents the simple substitution of one known, albeit inferior, cutting technique with a documented, superior one to achieve the predictable result of reduced burrs and resin chipping.

  • Additional Grounds: Petitioner asserted additional challenges, including that claim 8 is anticipated by Higuchi and, separately, by Perez. Further obviousness grounds were argued for claim 8 over Higuchi in view of POSITA's knowledge, for claims 1-4 over Matsuo and POSITA's knowledge, and for claims 5-7 over a three-way combination of Perez, Matsuo, and Higuchi. These grounds relied on similar theories of substituting known mechanical processing techniques.

4. Arguments Regarding Discretionary Denial

  • Petitioner argued that discretionary denial under Fintiv would be unwarranted. The parallel district court case was in its infancy, with minimal investment by the parties and the court.
  • Petitioner further stipulated that it would not pursue in district court any invalidity ground raised or that could have been reasonably raised in this IPR, thereby avoiding duplicative efforts.
  • It was argued that the asserted grounds are strong and that the technical nature of the patent, involving semiconductor manufacturing processes, is better suited for resolution by the PTAB than by a jury of laypersons.

5. Relief Requested

  • Petitioner requests institution of an inter partes review and cancellation of claims 1-8 of the ’007 patent as unpatentable.