Contract analysis

1. Specification (including Title, Cross-Reference to Related Applications, Background, Summary, Brief Description of the Drawings, and Detailed Description of the Preferred Embodiments)

2. Claims (20 total: 3 independent, 17 dependent)

3. Abstract of the Disclosure

4. Drawings (10 Figures: FIG. 1 through FIG. 10, with FIGS. 3A–3B and FIGS. 7A–7B)

5. Inventor Declaration / Oath (37 C.F.R. § 1.63)

8. Application Data Sheet (ADS)

9. Fee Transmittal (Small Entity) SPECIFICATION THERMALLY-ENHANCED FLIP-CHIP PACKAGING ARCHITECTURE FOR MULTI-CHANNEL SILICON-PHOTONIC MACH-ZEHNDER MODULATOR ARRAYS CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Provisional Application No. 63/297,841, filed January 10, 2022 (expired January 10, 2023), titled "Multi-Channel Silicon-Photonic Mach-Zehnder Modulator with Segmented Tra

1. Tapered Impedance-Matching Bump Array. The packaging architecture employs a spatially-graded array of conductive bumps positioned along the traveling-wave electrode feed lines of each modulator channel. The conductive bumps, which are preferably copper pillar bumps, have controlled diameter variation from approximately 25 µm at the RF input end to approximately 45 µm at the modulator electrode connection end. This

2. Embedded Micro-Channel Heat Sink in Package Substrate. The interposer substrate incorporates a network of micro-fluidic or micro-convective channels fabricated directly beneath the modulator active regions of the PIC die. The channels have cross-sectional dimensions of 50–200 µm in width and 100–400 µm in depth, and are designed to provide a thermal resistance below 0.5 K/W from the modulator junction to the coola

3. Passive-Alignment Optical Coupling Structures. Lithographically-defined V-groove and pedestal alignment features are formed on the interposer substrate surface, enabling sub-micron alignment of optical fiber arrays to the PIC edge couplers or grating couplers during the flip-chip bonding and assembly process. These passive alignment structures eliminate the need for active optical alignment during manufacturing, e

4. Differential Thermal Expansion Compensation Layer. An intermediate compliant layer, such as a polymer underfill with an engineered coefficient of thermal expansion (CTE) of 8–12 ppm/°C, is positioned between the PIC die and the interposer substrate. This compensation layer accommodates the CTE mismatch between the silicon PIC die (CTE approximately 2.6 ppm/°C) and the ceramic or organic interposer substrate (CTE t

1. Overview of the Package Architecture. Referring now to FIGS. 1 and 2, the thermally-enhanced flip-chip package assembly 100 according to a preferred embodiment of the present invention will be described. The package assembly 100 comprises a photonic integrated circuit (PIC) die 110, an interposer substrate 120, a tapered impedance-matching bump array 130, an embedded micro-channel heat sink structure 140, passive

2. Tapered Impedance-Matching Bump Array. Referring now to FIGS. 3A and 3B, the tapered impedance-matching bump array 130 according to a preferred embodiment of the present invention will be described in detail. The bump array 130 comprises a plurality of conductive bumps 132 arranged in a linear or quasi-linear pattern along each MZM RF feed line on the PIC die 110. For an 8-channel MZM array, there are eight indepe

3. Embedded Micro-Channel Heat Sink. Referring now to FIG. 4, the embedded micro-channel heat sink structure 140 according to a preferred embodiment of the present invention will be described in detail. The micro-channel heat sink structure 140 comprises a plurality of micro-channels 142 fabricated within the body of the interposer substrate 120, positioned directly beneath the modulator active regions of the PIC die

4. Passive-Alignment Optical Coupling Structures. Referring now to FIG. 5, the passive-alignment optical coupling structures 150 according to a preferred embodiment of the present invention will be described in detail. The passive-alignment optical coupling structures 150 are formed on the upper surface of the interposer substrate 120, in a region adjacent to the PIC die mounting area and aligned with the optical inp

5. Differential Thermal Expansion Compensation Layer. Referring now to FIG. 10, the differential thermal expansion compensation layer 160 according to a preferred embodiment of the present invention will be described in detail. The compensation layer 160 is a compliant underfill material that is applied to fill the gap between the PIC die 110 and the interposer substrate 120 after the flip-chip bonding operation. The

6. RF Redistribution and Signal Routing. The interposer substrate 120 includes a multi-layer RF redistribution network that connects the tapered impedance-matching bump array 130 to the package-level input/output pads that interface with the transceiver PCB. The RF redistribution traces are designed as controlled-impedance transmission lines, implemented in either stripline (traces sandwiched between two ground plane

7. Fabrication and Assembly Process. Referring now to FIG. 8, the fabrication and assembly process for the thermally-enhanced flip-chip package according to a preferred embodiment of the present invention will be described. The process comprises the following sequential steps: Step 1: Interposer Substrate Fabrication. The interposer substrate 120 is fabricated from a silicon wafer (for a silicon interposer embodiment