Optical Transmitter Bump Interconnect for Lower Parasitic Inductance
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Solution Overview
Problem
The existing optical transmitters using EML chips face band deterioration due to increased parasitic inductance caused by the length of the bonding wire, which complicates the structure and production process.
Innovation Solution
An optical transmitter design where the EML chip is mounted on a carrier with integrated high-frequency wires, and a bump is formed on the signal line to connect the high-frequency signal directly to the chip, reducing the length of the bonding wire and thus minimizing parasitic inductance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a long bonding wire is used to connect the high frequency wire to the chip, then the connection is more flexible and easier to manufacture, but the parasitic inductance increases and the bandwidth deteriorates
Solution Approach 1:
The patent transitions from a planar bonding wire connection to a three-dimensional structure by forming a bump on the signal line that rises to the same height as the chip surface. This vertical dimensionality change allows the bonding wire to connect at a higher point, effectively reducing its length and parasitic inductance while maintaining manufacturing feasibility through established bump bonding techniques
Solution Approach 2:
The patent changes the physical parameters of the connection structure by forming a bump with specific dimensions (height matching the chip thickness) to reduce the bonding wire length. This parameter modification directly reduces parasitic inductance from typical values to below 0.5 pH, thereby improving bandwidth to 35 GHz or more while keeping the manufacturing process compatible with existing technologies
2Reliability
If the EML chip structure is integrated to optimize individual components, then the extinction ratio improves and individual optimization is achieved, but the structure becomes complicated and the production process becomes complicated
Solution Approach 1:
The patent segments the EML chip into functionally independent modules: a DFB laser section and an EA modulator section, each optimized for its specific function. The DFB laser generates continuous wave light while the EA modulator performs modulation, allowing independent optimization of each component while maintaining overall system integration. This modular segmentation simplifies the design and production process compared to fully integrated monolithic structures
Data Source
AI summary
Band deterioration due to parasitic inductance of a bonding wire is suppressed. Provided is an optical transmitter in which a chip to which a high frequency signal is applied is mounted on a carrier on which a high frequency wire is formed, and a high frequency signal is supplied to an electrode of the chip via a bump formed on a signal line of the high frequency wire and equal to a height of the chip.