Continuous RF Flex Circuit for High-Speed Optical Package Assembly

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Solution Overview

Problem

Conventional RF signal paths in high-speed optical packages require soldered junctions, which are prone to tolerances and misalignments, leading to RF penalties and reliability issues, especially at high frequencies.

Innovation Solution

A continuous RF flexible printed circuit (FPC) is used to eliminate the need for soldered and wire bond-based RF transitions by integrating a flexible and rigid section, providing a direct interconnect between Tx ASIC and CDM, reducing RF losses and assembly complexity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If soldered junctions are used in RF signal paths, then electrical connection is achieved, but RF losses increase and reliability decreases at high frequencies

Engineering Contradiction:

ImproveRF signal path reliabilityVSAvoidRF losses

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The patent removes soldered junctions and wire bonds from the RF signal path, extracting the problematic intermediate connection elements. The FPC provides a direct continuous conductive path from the Tx ASIC to the CDM, eliminating the soldered transitions that cause RF losses and reliability issues at high frequencies

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent merges the flexible printed circuit with the RF signal path to create a continuous conductive structure. The FPC integrates the flexible section with the rigid section, combining multiple functions (signal transmission, mechanical flexibility, electrical connection) into a single continuous structure that eliminates intermediate junctions

Inventive Principle:

Principle #5Merging (Combining)

2Ease of manufacture

If soldered junctions and wire bonds are used for RF transitions, then electrical connection is established, but assembly complexity increases

Engineering Contradiction:

ImproveAssembly processVSAvoidRF transition structure

Core Design Contradiction:

Ease of manufactureVSDevice complexity

Solution Approach 1:

The patent extracts and removes the complex assembly steps involving soldered junctions and wire bonds. By eliminating these intermediate connection methods, the assembly process is simplified to direct mounting of the FPC, reducing both the number of assembly steps and the complexity of the RF transition structure

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The FPC serves multiple functions simultaneously: it provides mechanical flexibility, electrical connection, and RF signal transmission. This multi-functional integration eliminates the need for separate components (solder joints, wire bonds, RF carriers) and simplifies the overall assembly process

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS12520418B2High-speed optical package with continuous radio frequency (RF) flexible printed circuit

Publication Date: 2026.01.06 CIENA CORP

AI summary

Aspects of the subject disclosure may include, for example, a flexible printed circuit (FPC) for interconnecting an optical device and an application specific integrated circuit (ASIC), wherein the FPC includes a first section that is configured with a first plurality of electrically conductive traces and a second section over which one or more components are disposed, and wherein the second section is configured with a second plurality of electrically conductive traces that extend from the first plurality of electrically conductive traces to the one or more components. Other embodiments are disclosed.