Optical Module Solder Ball Bonding for High-Frequency Signal Integrity
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Solution Overview
Problem
High-frequency optical communication modules face impedance mismatching and electrical crosstalk issues due to high inductance in wire bonding, which deteriorates their performance at speeds above 50 Gbps.
Innovation Solution
The optical module employs a solder ball bonding structure with a flexible printed circuit board (PCB) that includes air holes and specific signal and ground wiring configurations to reduce capacitance and impedance mismatching, using solder balls to connect the optical transmission/reception unit, electronic IC, and carrier board directly, thereby minimizing electrical wiring and enhancing high-frequency characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wire bonding is used to form electrical connections between components, then electrical connections can be established, but high inductance between wires causes serious impedance mismatching and deteriorates high frequency characteristics
Solution Approach 1:
The patent extracts and removes the wire bonding structure from the electrical connection system. Instead of using wires to connect components, the invention directly bonds the optical transmission/reception unit and electronic IC to the flexible PCB through solder balls, eliminating the intermediate wire structure that causes high inductance and impedance mismatching.
Solution Approach 2:
The patent replaces the mechanical wire bonding system with a direct solder ball bonding system. The wire bonding mechanical structure is substituted by a more integrated approach where components are directly mounted and bonded to the PCB, reducing the physical distance and structural complexity of electrical connections.
2Reliability
If multiple wires are used for electrical connections, then electrical connectivity is achieved, but electrical crosstalk occurs between multiple wires making it hard to obtain excellent high frequency characteristics at 50 Gbps or higher
Solution Approach 1:
The patent extracts and eliminates the multiple wire structure from the electrical connection system. By using direct solder ball bonding between components and the flexible PCB, the invention removes the intermediate wiring that causes electrical crosstalk, thereby improving high frequency characteristics at 50 Gbps and above.
3Reliability
If conventional PCB structure without air holes is used, then manufacturing is simpler, but capacitance is higher causing impedance mismatching that deteriorates high frequency performance
Solution Approach 1:
The patent introduces air holes into the flexible PCB structure, creating a porous configuration. These air holes reduce the capacitance between signal lines and ground by removing dielectric material, thereby improving impedance matching and reducing signal loss for high frequency operations.
Solution Approach 2:
The patent changes the physical structure of the PCB by introducing air holes, which alters the electrical parameters (capacitance and impedance) of the signal paths. This parameter modification enables better impedance matching and reduced capacitance effects at high frequencies.
Data Source
AI summary
Provided is an optical module including an optical waveguide device through which multiple channel lightwaves are input and output, an optical transmission/reception unit disposed on one side of the optical waveguide device, an electronic IC disposed on one side of the optical transmission/reception unit and configured to drive the optical transmission/reception unit, a flexible printed circuit board (PCB) disposed on the optical transmission/reception unit and the electronic IC, a first solder ball between the optical transmission/reception unit and the flexible PCB and a second solder ball between the electronic IC and the flexible PCB.