Air Cavity Plastic Package for High Frequency Optoelectronics
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Solution Overview
Problem
Conventional plastic packages for optoelectronic devices limit their performance to below 2.5GHz due to the use of silicon encapsulation, which is not Telcordia compliant and has inadequate electrical return loss, restricting higher bandwidth applications.
Innovation Solution
An air cavity plastic package design featuring upper and lower plastic housings with conductors and a support member, where the chip is secured within the lower housing and the housings are sealed to form an air cavity, eliminating the need for silicon encapsulation and allowing for higher frequency performance by using liquid crystal polymers and a getter to control moisture.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If silicon encapsulation is used in plastic packages to protect optoelectronic devices, then device protection from moisture is achieved, but performance is limited to below 2.5GHz with inadequate electrical return loss
Solution Approach 1:
The patent removes the silicon encapsulation layer from the package structure and replaces it with an air cavity environment. This extraction of the problematic silicon material eliminates the electrical performance limitations while maintaining device protection through alternative means (hermetic seal and conformal coating), thereby enabling operation at frequencies of 12.5GHz and above
Solution Approach 2:
The patent changes the dielectric environment surrounding the optoelectronic device from silicon (with its specific dielectric properties) to air (with different dielectric properties). This parameter change in the encapsulation material fundamentally improves the electrical return loss and enables higher frequency operation while maintaining protective functions through hermetic sealing
2Reliability
If hermetic metal or ceramic packages are used for optoelectronic devices, then device protection and electrical connections are achieved, but manufacturing cost increases significantly
Solution Approach 1:
The patent replaces expensive hermetic metal or ceramic packages with a plastic package structure that achieves hermetic protection through alternative methods (sealants, conformal coatings, and air cavity design). This substitution with cheaper materials maintains the necessary protection level while dramatically reducing manufacturing cost
Solution Approach 2:
The patent employs a composite package structure combining plastic housing, air cavity, and selective hermetic sealing elements. This composite approach achieves the protective functions of hermetic metal/ceramic packages while utilizing cost-effective plastic materials for the bulk structure, thereby reducing overall manufacturing cost
3Ease of manufacture
If conventional plastic packages with silicon encapsulation are used, then cost reduction is achieved, but electrical return loss and bandwidth performance are inadequate for high frequency applications
Solution Approach 1:
The patent removes silicon encapsulation from the conventional plastic package structure and replaces it with an air cavity environment. This extraction eliminates the electrical performance degradation caused by silicon while preserving the cost advantages of plastic packaging, enabling both economic and electrical performance goals to be met
Solution Approach 2:
The patent creates an air-filled inert environment within the plastic package to replace silicon encapsulation. This air cavity provides the necessary electrical performance characteristics (low dielectric loss, good return loss) for high frequency operation while maintaining the protective function through hermetic sealing, thus achieving both cost-effectiveness and electrical reliability
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 air cavity plastic package enables optoelectronic devices to operate at frequencies of at least 12.5GHz with improved electrical return loss and compliance with Telcordia standards, enhancing performance and reliability.
Implementation Method 1
The cavities form an enclosed air cavity between the housings
Implementation Method 2
using liquid crystal polymers and a getter to control moisture
Implementation Method 3
creating a seal between the upper housing and the lower housing
Implementation Method 4
The lower housing further comprises a support member to which is attached the upper end of each conductor and the conductors are bent inside the plastic material of the lower housing
Data Source
Figure 1
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AI summary
The present invention generally relates to an air cavity plastic package (100) for a high frequency optical device. In one aspect, a module package (100) for a high frequency optoelectronic device is provided. The module package includes an upper plastic housing (125) having an upper cavity (130) formed therein and a lower plastic housing (150) having a lower cavity (155) formed therein. The upper housing and the lower housing are configured to mate together such that the cavities form an enclosed air cavity between the housings. Additionally, upon creating a seal between the housings, an optical feed through is realized. The module package further includes a plurality of conductors (160,180) disposed in the lower housing, each conductor having an upper end (160B,180B) and a lower end (160A,180A), wherein the upper end is connectable to a chip (105) disposed in the air cavity and the lower end is connectable to a board. In another aspect, a method of packaging and assembling a high frequency optical device is provided. In yet another aspect, a package assembly for an electro-optical modulator is provided.