Cree, Inc.

Patent Trials and Appeals Board

Feb 24, 2022

2021003288 (P.T.A.B. Feb. 24, 2022)

UNITED STATES PATENT AND TRADEMARK OFFICE UNITED STATES DEPARTMENT OF COMMERCE United States Patent and Trademark Office Address: COMMISSIONER FOR PATENTS P.O. Box 1450 Alexandria, Virginia 22313-1450 www.uspto.gov APPLICATION NO. FILING DATE FIRST NAMED INVENTOR ATTORNEY DOCKET NO. CONFIRMATION NO. 15/673,734 08/10/2017 David Seebacher 1259-001US01/P2836US1 4931 28863 7590 02/24/2022 SHUMAKER & SIEFFERT, P. A. 1625 RADIO DRIVE SUITE 100 WOODBURY, MN 55125 EXAMINER LIU, XIAOMING ART UNIT PAPER NUMBER 2812 NOTIFICATION DATE DELIVERY MODE 02/24/2022 ELECTRONIC Please find below and/or attached an Office communication concerning this application or proceeding. The time period for reply, if any, is set in the attached communication. Notice of the Office communication was sent electronically on above-indicated "Notification Date" to the following e-mail address(es): pairdocketing@ssiplaw.com PTOL-90A (Rev. 04/07) UNITED STATES PATENT AND TRADEMARK OFFICE BEFORE THE PATENT TRIAL AND APPEAL BOARD Ex parte DAVID SEEBACHER, CHRISTIAN SCHUBERTH, PETER SINGERL, and ALEXANDER KOMPOSCH Appeal 2021-003288 Application 15/673,734 Technology Center 2800 Before BRIAN D. RANGE, LILAN REN, and SHELDON M. MCGEE, Administrative Patent Judges. MCGEE, Administrative Patent Judge. DECISION ON APPEAL Pursuant to 35 U.S.C. § 134(a), Appellant1 appeals from the Examiner’s decision to reject claims 1-11, 13, 15, 16, and 18-23. We have jurisdiction. 35 U.S.C. § 6(b). We reverse. 1 Appellant” refers to “applicant” as defined in 37 C.F.R. § 1.42. Appellant identifies the real party in interest as Cree, Inc. Appeal Br. 3. Appeal 2021-003288 Application 15/673,734 2 CLAIMED SUBJECT MATTER The subject matter on appeal “relates to fabrication and manufacture of devices such as electronic devices.” Spec. ¶ 1. According to the Specification, a die may be attached to a flange, e.g., a heat-sink, using die- attach material such as solder. Id. ¶ 2. When the die and the flange are heated, these components may expand in different amounts if their respective coefficients of thermal expansion differ, resulting in mechanical stress in the device. Id. The Specification teaches that pre-stressing the flange prior to attaching a die may compensate for its thermal expansion, and thus, “[b]y pre-stressing the flange, the device may experience lower stresses when the device is cooled to a lower temperature.” Spec. ¶¶ 3, 4. Such pre-stressing can be carried out by using a clamp or fixture. Id. ¶ 31, Figs. 5, 6. Claim 1 is illustrative of the claimed subject matter and is reproduced below: 1. A method comprising: pre-stressing a flange that is not attached to any die; heating the flange to a die-attach temperature; and attaching a die to the pre-stressed flange at the die-attach temperature using a die-attach material, wherein the pre- stressing of the flange is maintained during attaching the die to the pre-stressed flange. Appeal 2021-003288 Application 15/673,734 3 REJECTIONS Claims 1-11, 13, 15, 16, and 18-23 are rejected under 35 U.S.C. § 103 over Sri-Jayantha2 in view of Seddon,3 either with or without additional prior art.4 Final Act. 4-11. OPINION The dispositive issue on appeal is whether the Examiner has established by a preponderance of the evidence that the skilled artisan would have found it obvious to modify Sri-Jayantha’s cure process--which includes pre-stressing a flange that is attached to a die--to pre-stress the flange before a die is attached as claimed. Because the Examiner failed to do so on this record, we do not sustain the rejections. Each independent claim on appeal requires “pre-stressing a flange that is not attached to any die.” Claims 1, 11, 18. Appeal Br. 25, 27, 28 (Claims App.). Therefore, we focus our discussion on claim 1. The Examiner finds that Sri-Jayantha teaches a method which includes the step of pre-stressing a flange but does not expressly disclose pre-stressing a flange that is not attached to any die as required by claim 1. Final Act. 5. The Examiner finds, however, that Seddon teaches flange preheating steps p1 and p2 when the die is not attached “to burn off impurities and avoid damaging the board.” Id. (citing Seddon ¶ 26). The Examiner reasons that the skilled artisan would have found it obvious to modify Sri-Jayantha’s method to preheat flange 1 (with 5) before attaching 2 US 2011/0174443 A1, published July 21, 2011. 3 US 2017/0018542 A1, published January 19, 2017. 4 US 2010/0193943 A1, published August 5, 2010, or US 2016/0161550 A1, published June 9, 2016. Appeal 2021-003288 Application 15/673,734 4 die 2 with material 3 in order to burn off impurities. Id. Sri-Jayantha’s Figure 3a is illustrative of the apparatus pre-cure: Sri-Jayantha’s Figure 3a depicts substrate 1 which is mapped to the claimed “flange,” die 2, and underfill material 3, to be situated in tub-like tray 5 at room temperature before a cure process cycle. Sri-Jayantha ¶¶ 44, 52-54. Appellant argues, inter alia, that Sri-Jayantha’s method includes an underfill process that would be unsatisfactory without a die that is already attached. Appeal Br. 7-8. Specifically, Appellant points to paragraphs 16 and 43 of Sri-Jayantha and argues that the silicon die is required to be attached to the substrate prior to the underfill process. Id. According to Appellant, Sri-Jayantha’s “underfill process could not occur because there would be no space in which to inject the liquid underfill material,” thus rendering that underfill process unsatisfactory for its intended purpose. Id. at 8. The Examiner fails to respond to this argument in the Answer. See Ans. 3-5 (addressing Appellant’s arguments with respect to Group 1, of which claim 1 is a part, but failing to address this particular argument). This is significant because the Examiner relies on Sri-Jayantha’s underfill 3 as the claimed “die-attach material.” Final Act. 5. Appellant appears to be correct that Sri-Jayantha’s underfill process requires attachment of the die to a Appeal 2021-003288 Application 15/673,734 5 substrate before the underfill is applied. See Sri-Jayantha ¶ 22 (“the die is first attached to a substrate (e.g., an organic substrate) prior to an underfill operation”) ¶ 43 (“Substrate 1 and die (chip) 2 that have already been joined through a reflow[5] process, are injected with an underfill 3”). We recognize that Sri-Jayantha also states that “[a] liquid underfill material is typically injected into the space between the die and the substrate, and a cure process is initiated.” Sri-Jayantha ¶ 16 (emphasis added). One possible interpretation of this disclosure is that the liquid underfill material can be injected in some other manner, e.g., without a space between the die and substrate. In the absence of a responsive technical explanation to Appellant’s argument regarding the underfill process, however, it is unclear whether the prior art underfill process could have been carried out with a reasonable expectation of success without such attachment of the die to the substrate. Therefore, on this record, Appellant persuades us that the Examiner has not established that the proposed modification of Sri-Jayantha would have been obvious. For this reason, we do not sustain the Examiner’s rejections. CONCLUSION The Examiner’s rejections are reversed. 5 “A silicon die is first attached to an electronic (e.g., organic or ceramic) substrate through a reflow process where the solder bumps are melted and allowed to form a link between the two parts.” Sri-Jayantha ¶ 16. Appeal 2021-003288 Application 15/673,734 6 DECISION SUMMARY Claims Rejected 35 U.S.C. § Reference(s)/Basis Affirmed Reversed 1-6, 8- 11, 13, 16, 18-21 103 Sri-Jayantha, Seddon 1-6, 8-11, 13, 16, 18- 21 7, 15 103 Sri-Jayantha, Seddon, Crowder 7, 15 22, 23 103 Sri-Jayantha, Seddon, Yeric 22, 23 Overall Outcome 1-11, 13, 15, 16, 18- 23 REVERSED