Optical Module Structure Using Through-Hole Electrodes
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Solution Overview
Problem
High-speed optical modules face challenges in transmitting data at speeds of 50 Gbs or more due to increased transmission loss and degradation of high-frequency signals caused by bonding wires, particularly in systems using 4-level pulse amplitude modulation, which requires shorter paths and reduced module size.
Innovation Solution
The optical module structure incorporates a laminated configuration with an interposer substrate, communication LSIs, an Si bench substrate, and IC elements connected via protruding electrodes and lateral-surface terminals, reducing the length of signal paths and optimizing the layout to minimize signal degradation and module size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If bonding wires are used to connect chips in conventional optical modules, then electrical signals can be transmitted between components, but the inductance components of the bonding wires cause impedance mismatch and signal reflection that degrades high-frequency signals at transmission speeds of 10 Gbs or more
Solution Approach 1:
The invention extracts and eliminates the bonding wires from the system by implementing direct chip-to-substrate mounting. The light-emitting element chip and light-receiving element chip are mounted directly on the substrate without bonding wires, removing the source of inductance and impedance mismatch that causes signal degradation at high transmission speeds.
Solution Approach 2:
The invention introduces a substrate with through-hole electrodes as an intermediary structure. The through-hole electrodes extend from the front surface to the back surface of the substrate, providing direct electrical connection paths between the light-emitting element chip, light-receiving element chip, and external terminals without requiring bonding wires as mediators.
2Productivity
If multiple wirings are arranged in parallel for multi-channelizing, then multiple electrical signals can be transmitted simultaneously, but crosstalk as mutual interference between wirings increases
Solution Approach 1:
The invention extracts and eliminates the parallel wiring structure that causes crosstalk. By removing bonding wires and implementing direct mounting of multiple element chips on the substrate with through-hole electrodes, the system achieves multi-channel transmission without the capacitive coupling between parallel wires that generates crosstalk.
3Object-generated harmful factors
If the wiring interval is increased to reduce crosstalk, then mutual interference between electrical signals decreases, but the optical module size increases
Solution Approach 1:
The invention extracts and eliminates the need for increased wiring intervals by removing the bonding wire structure entirely. The direct chip mounting on the substrate with through-hole electrodes enables compact multi-channel configuration without requiring large spacing between signal paths, thus reducing module size while avoiding crosstalk.
4Speed
If bonding wire length is shortened to reduce inductance and improve high-speed transmission, then signal degradation is reduced, but the complexity of chip mounting and connection increases
Solution Approach 1:
The invention extracts and eliminates the bonding wires entirely, replacing them with direct chip mounting on the substrate. This removes the need to optimize bonding wire length and simplifies the connection structure, as the through-hole electrodes in the substrate provide direct electrical pathways without requiring wire bonding processes.
Solution Approach 2:
The invention replaces the mechanical bonding wire connection system with a direct electrical connection system through through-hole electrodes. The light-emitting element chip and light-receiving element chip are electrically connected to external terminals through the substrate's through-hole electrodes without mechanical wire bonding, simplifying the mounting process and reducing inductance.
Data Source
AI summary
An optical module structure includes a main substrate, an interposer substrate electrically connected to the main substrate via a first protruding electrode, a first communication LSI electrically connected to the interposer substrate via a second protruding electrode, an IC element electrically connected to the interposer substrate via a lateral-surface connection terminal of the interposer substrate and via a third protruding electrode, an Si bench substrate electrically connected to the IC element via a fourth protruding electrode and via a lateral-surface connection terminal of the Si bench substrate, an optical element electrically connected to the Si bench substrate via a fifth protruding electrode, and an optical fiber optically connected via an optical waveguide formed on the Si bench substrate.