Obviousness

Obviousness Analysis under 35 U.S.C. § 103 for US Patent 11177887

This analysis identifies combinations of prior art references that would render the claims of US patent 11177887 obvious to a person having ordinary skill in the art (PHOSITA). The primary motivation for the claimed invention is to reduce the length and improve the angle of electrical interconnections (wire bonds) between a Transmitter Optical Subassembly (TOSA) module and the main substrate, thereby improving signal integrity for high-speed optical transceivers. The patent achieves this through a substrate with a "stepped profile" that includes a recessed TOSA mounting surface and a vertical surface acting as a mechanical stop.

Key Features of US11177887

The independent claims (Claim 1 and Claim 10) of US11177887 describe:

1. A substrate with an electrical coupling end and an optical coupling end.
2. A first mounting region at the electrical coupling end with a component mounting surface.
3. A second mounting region at the optical coupling end with a recessed TOSA mounting surface offset from the component mounting surface by a first offset distance (OD1), forming a stepped profile.
4. A vertical surface adjoining the recessed TOSA mounting surface and the component mounting surface.
5. The vertical surface acts as a mechanical stop to engage a surface of the TOSA module and limit its travel along one or more axes.
6. The second mounting region is configured to edge mount the at least one TOSA module.
7. For Claim 10, an additional receiver optical subassembly (ROSA) arrangement is coupled to the transceiver substrate.
8. Dependent claims specify reduced wire bond lengths (less than 500 microns, preferably less than 400 microns) and angles (less than or equal to 45 degrees) resulting from this stepped configuration.

Combinations of Prior Art References

Combination 1: US10044445B2 in view of FIG. 8 of US11177887 and US10698168B1 (or general knowledge of mechanical alignment)

Primary Reference: US10044445B2 (Applied Optoelectronics, Inc.)

• Title: Techniques for reducing electrical interconnection losses between a transmitter optical subassembly (TOSA) and associated driver circuitry and an optical transceiver system using the same.
• Relevance: This patent, from the same assignee as US11177887, directly addresses the problem of reducing electrical interconnection losses, which is the core motivation for the stepped profile in US11177887. US10044445B2 explicitly discloses an optical subassembly module with a substrate featuring "a plurality of first pads at a first height to couple to an optical component; a plurality of second pads at a second height to couple to a driver circuit; and a plurality of third pads at a third height to couple to a bias control circuit, wherein the first, second, and third heights are different." This directly teaches the concept of a "stepped profile" on a substrate and a "recessed TOSA mounting surface" by virtue of providing components (like optical components and driver circuitry, which are part of a TOSA module) at different vertical offsets. The objective is to bring these components closer to their respective electrical terminals to minimize interconnection losses.

Secondary Reference: FIG. 8 of US11177887 (Admitted Prior Art)

• Relevance: FIG. 8 of US11177887 illustrates an "example approach to mounting and electrical coupling of transmitter optical subassemblies (TOSA) modules on a transceiver substrate" where the substrate "edge-mounts to a plurality of TOSA modules." This clearly demonstrates that edge mounting of TOSA modules was a known technique in the prior art. Therefore, applying edge mounting to the stepped substrate configuration of US10044445B2 would be a straightforward design choice for a PHOSITA.

Tertiary Reference: US10698168B1 (Similar Document)

• Title: Printed circuit board assembly (PCBA) with integrated mounting structure to align and couple to transmitter optical assembly (TOSA) modules.
• Relevance: This patent teaches an "integrated mounting structure to align and couple to transmitter optical assembly (TOSA) modules." Such mounting structures inherently include mechanical features, like stops or guides, to facilitate precise alignment and placement of optical components. The provision of mechanical stops to aid in the precise mounting and alignment of components, especially in optical assemblies requiring tight tolerances, is a well-established engineering practice. US11177887 itself highlights the benefit of the vertical surface acting as an "alignment guide by providing mechanical stops/limits to limit travel along at least one axis," indicating this is a known desirable function.

Motivation for Combination:
A PHOSITA would be motivated to combine the teachings of US10044445B2 with the known practice of edge mounting (from FIG. 8) and the use of mechanical stops (from US10698168B1 or general engineering knowledge) to achieve improved manufacturability, alignment, and signal integrity in optical transceiver modules. US10044445B2 provides the core concept of a stepped substrate to reduce electrical interconnection lengths and losses. Integrating edge mounting into this design offers a compact and efficient way to physically attach the TOSA modules. Furthermore, incorporating mechanical stops into the stepped profile (i.e., having the vertical surface function as a stop) would be an obvious design choice to simplify and enhance the precision of TOSA module placement and alignment, which is critical for effective optical coupling and realizing the benefits of shortened electrical interconnects. The resulting shortened and angled wire bonds, claimed in dependent claims, are a direct and expected outcome of successfully implementing the stepped and recessed mounting approach to bring the LDD and RF terminals closer together.

Combination 2: Combination 1 + US10884201B2 (for Claim 10)

Additional Reference: US10884201B2 (Applied Optoelectronics, Inc.)

• Title: Receptacle configuration to support on-board receiver optical subassembly (ROSA).
• Relevance: This patent explicitly teaches an "on-board receiver optical subassembly (ROSA)." Optical transceivers, by definition, include both transmitter and receiver functionalities. US11177887 itself describes an optical transceiver module including a "multi-channel receiver optical subassembly (ROSA) arrangement 108" (FIG. 1).

Motivation for Combination:
For Claim 10, which describes an optical transceiver including a ROSA arrangement, a PHOSITA would find it obvious to integrate a known ROSA arrangement (as taught by US10884201B2 or general transceiver design principles) with the combined TOSA subassembly module of Combination 1. This merely represents the standard practice of combining well-known transmitter and receiver components onto a single substrate to form a complete optical transceiver, while applying the benefits of the stepped TOSA mounting for the transmit path.