Optical Semiconductor Package Impedance Matching via Sealing Glass Bubbles
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Solution Overview
Problem
In high-speed optical communication, the characteristic impedance of signal wires in optical semiconductor element packages deviates from 50 Ω, leading to reduced signal transmission efficiency, and existing methods to match impedance, such as increasing hole diameter or decreasing wire diameter, compromise airtight and wire bonding properties.
Innovation Solution
Adjusting the dielectric constant of sealing glass by controlling the amount of bubbles within the glass to match the characteristic impedance to 50 Ω, while maintaining airtight and wire bonding properties, by setting the hole diameter to 1.2 mm, wire diameter to 0.21 mm, and dielectric constant to 4.4, ensuring proper signal transmission and airtightness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the hole diameter D of the sealing hole is increased to match the characteristic impedance to 50 Ω, then the characteristic impedance is improved, but the area where the optical semiconductor element is arranged is reduced
Solution Approach 1:
The patent changes the dielectric constant parameter of the sealing glass by controlling the bubble content. By adjusting the dielectric constant from its conventional value to a lower value, the characteristic impedance can be matched to 50 Ω without increasing the hole diameter, thus preserving the arrangement area of the optical semiconductor element.
2Manufacturing precision
If the wire diameter of the lead pin is decreased to match the characteristic impedance to 50 Ω, then the characteristic impedance is improved, but the wire bonding property deteriorates
Solution Approach 1:
Instead of changing the wire diameter, the patent changes the dielectric constant of the sealing glass. This alternative parameter change achieves the same impedance matching effect without compromising the wire bonding properties of the lead pin.
3Manufacturing precision
If glass with a low dielectric constant is used as sealing glass to match the characteristic impedance to 50 Ω, then the characteristic impedance is improved, but the sealing property and airtight property deteriorate
Solution Approach 1:
The patent intentionally introduces bubbles (porosity) into the sealing glass to reduce its dielectric constant. The controlled porosity achieves the desired dielectric constant for impedance matching while the glass matrix maintains the sealing and airtight properties.
Solution Approach 2:
The sealing glass becomes a composite material consisting of glass matrix and embedded bubbles. This composite structure allows tuning of the dielectric constant through bubble content control while maintaining the fundamental sealing properties of the glass material.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method effectively sets the characteristic impedance to 50 Ω, enhancing signal transmission properties for high-speed communication while maintaining excellent airtight and wire bonding properties, as demonstrated by experimental results showing no significant waveform deformation and sustained airtightness over time.
Implementation Method 1
the dielectric constant Er of the sealing glass is set by controlling an amount of bubble contained in the sealing glass
Data Source
Figure 1
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AI summary
A package for an optical semiconductor element is provided. The package includes: a stem body (10) having a sealing hole therein; and a lead pin (12) having a glass sealing portion which is sealed with sealing glass (13) in the sealing hole. Characteristic impedance of the glass sealing portion is adjusted to a given value. The characteristic impedance Zo is given by: Zo = (138/Er1/2)×log(D/d), where a hole diameter of the sealing hole is D, a wire diameter of the lead pin (12) is d, and a dielectric constant of the sealing glass (13) is Er, and the dielectric constant Er of the sealing glass is set by controlling an amount of bubble contained in the sealing glass (13).