Ceramic RF Feedthrough Structure for Low-Loss Hermetic Sealing
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Solution Overview
Problem
Existing glass-to-metal RF feedthroughs in hermetically sealed electrical circuit packages are laborious and costly to manufacture, and suffer from poor RF conductivity and passive intermodulation (PIM) distortion due to the lossy nature of materials like nickel and Kovar, which attenuate RF signals and cause interference.
Innovation Solution
The use of non-ferrous conductors, such as silver or palladium, adhered to a ceramic body using thick-film or thin-film technology, with voids to accommodate thermal expansion, and a hermetic seal using non-leaching solder, to create ceramic RF feedthroughs with reduced RF attenuation and PIM distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If glass-to-metal feedthrough components are used, then hermetic sealing is achieved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent uses a composite structure combining ceramic insulator material with metal ferrule and pin materials. The ceramic body provides electrical insulation and hermetic sealing properties, while the metal components provide electrical conductivity and mechanical strength. This composite approach replaces the traditional glass-to-metal construction, simplifying manufacturing while maintaining hermetic sealing reliability.
2Reliability
If glass-to-metal feedthrough components are used, then hermetic sealing is achieved, but manufacturing cost increases
Solution Approach 1:
The patent employs composite materials including ceramic insulators, metal ferrules, and pin assemblies. The ceramic body with integrated conductive paths eliminates the need for separate glass bonding and plating operations required in traditional glass-to-metal feedthroughs. This reduces manufacturing steps, labor requirements, and overall production cost while maintaining hermetic sealing performance.
3Strength
If nickel and Kovar materials are used in feedthroughs, then structural integrity is maintained, but RF conductivity deteriorates
Solution Approach 1:
The patent changes the material parameters by replacing nickel and Kovar with copper or copper alloy materials for the ferrule and pin components. Copper provides superior electrical conductivity and lower RF signal attenuation while maintaining adequate mechanical strength. The ceramic insulator material parameters are also optimized to provide appropriate dielectric properties and mechanical support, achieving both structural integrity and improved RF performance.
4Reliability
If nickel plating is applied to Kovar, then corrosion resistance is improved, but RF signal loss increases
Solution Approach 1:
The patent eliminates the nickel plating layer by using copper or copper alloy materials that inherently provide both corrosion resistance and excellent electrical conductivity. The copper materials are selected with appropriate alloying elements to achieve the required corrosion resistance without requiring additional plating layers, thereby eliminating the RF signal loss associated with nickel plating while maintaining protective properties.
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
Ceramic RF feedthroughs offer improved RF conductivity and reduced manufacturing costs, with enhanced performance by minimizing signal loss and interference, making them suitable for hermetically sealed electrical circuit packages.
Implementation Method 1
A non-ferrous conductor is selectively adhered to an outer peripheral surface of a ceramic body and to an inner peripheral surface of an aperture through the ceramic body. A non-ferrous conductive lead is disposed through the aperture... with voids to accommodate thermal expansion
Implementation Method 2
The hermetic seal is necessary to prevent infiltration of fluids, particulates and other environmental contaminants... a hermetic seal using non-leaching solder
Data Source
AI summary
A radio frequency (RF) feedthrough component having an impedance greater than 20 ohms is disclosed. The feedthrough includes a ceramic body having a flexible non-ferrous conductor adhered to its outer peripheral surface and to an inner peripheral surface of an aperture through the ceramic body. A non-ferrous conductive lead is disposed through the aperture and protrudes from at least one side thereof. A non-ferrous hermetic seal is formed between a portion of the non-ferrous conductive lead disposed in the aperture and the non-ferrous conductor adhered to the surface of the aperture. The RF feedthrough can be assembled in an opening of a conductive housing to form an electromagnetically shielded package for an electrical circuit.