Kovar Microwave Package J-Pin Impedance Matching
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Solution Overview
Problem
Existing surface mount packages for microwave circuits face challenges in achieving low cost, wideband operation up to 50 GHz with reliable hermetic sealing and minimal impedance matching issues, particularly due to discontinuities in electromagnetic field distributions and RF current configurations, which lead to signal reflections and losses.
Innovation Solution
A broadband surface mount package is designed with a J-shaped conductive element and hermetically sealed cylindrical holes, machined from a Kovar block, to provide a smooth transition for microwave signals and minimize impedance mismatch, using a glass substrate for sealing and Kovar for thermal expansion matching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional surface mount packages use glass-to-metal seals and multi-layer ceramic structures, then hermetic sealing reliability is improved, but manufacturing cost and device complexity increase
Solution Approach 1:
The patent extracts and eliminates the complex multi-layer ceramic structure and glass-to-metal seal components, replacing them with a simplified Kovar housing and laser-welded aluminum lid assembly. This extraction of unnecessary complex components directly reduces device complexity while maintaining hermetic sealing through the laser welding process.
Solution Approach 2:
The patent changes the sealing method from mechanical glass-to-metal sealing to laser welding parameter-based sealing. By using laser welding parameters (energy, duration, focal point) to create hermetic seals between the Kovar housing and aluminum lid, the system achieves reliable sealing with simpler structure and lower cost.
2Ease of manufacture
If packages use mechanical drilling of VIAs with tiny drill bits, then through-holes can be created, but manufacturing cost increases due to high rates of wear and breakage
Solution Approach 1:
The patent replaces the mechanical drilling system with a laser-based system. Instead of using tiny mechanical drill bits that suffer from wear and breakage, the invention uses laser energy to create through-holes and recesses in the Kovar housing, eliminating mechanical contact and associated manufacturing inefficiencies.
Solution Approach 2:
The patent introduces laser energy as an intermediary between the manufacturing process and the material. The laser acts as a mediator that transfers energy to melt and vaporize material for creating holes and recesses, avoiding the need for mechanical cutting tools and their associated wear and breakage problems.
3Ease of manufacture
If laser-drilled VIAs are used to achieve step-up transition, then through-holes can be created, but surface finish quality inside holes deteriorates
Solution Approach 1:
The patent applies preliminary action by first creating the rough laser-drilled hole, then performing a secondary machining operation to precision-machine the internal surfaces of the holes and recesses. This two-step process allows the laser to efficiently create the geometry while the subsequent machining restores surface finish quality for proper plating and sealing.
Solution Approach 2:
The patent segments the manufacturing process into distinct stages: laser drilling/ablation for bulk material removal, followed by precision machining for surface finish, then plating for electrical conductivity and corrosion resistance. This segmentation allows each process to optimize for its specific function without compromising overall quality.
4Adaptability or versatility
If packages are designed for broadband operation up to 50 GHz, then frequency range is improved, but impedance matching becomes more difficult due to stepped transitions
Solution Approach 1:
The patent uses another dimension by creating three-dimensional tapered transitions and stepped structures with optimized geometries. By carefully designing the dimensional progression of the transmission line structures and their interconnections in multiple dimensions, the patent achieves broadband impedance matching that minimizes reflections across the 0.1-50 GHz frequency range.
5Reliability
If expensive materials and thick gold plating are used, then reliability and corrosion resistance are improved, but manufacturing cost increases
Solution Approach 1:
The patent changes the material parameters by selecting Kovar (a cost-effective alloy) instead of expensive ceramics or stainless steels, and using copper or nickel plating instead of thick gold plating. These parameter changes in material composition and plating thickness achieve adequate corrosion resistance and electrical conductivity at lower cost.
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 solution achieves reliable hermetic sealing and minimal microwave signal losses, maintaining gain flatness within +/-2.5 dB across 0.5-50 GHz, suitable for various environments and applications, while being cost-effective and adaptable for surface mounting on printed circuit boards.
Implementation Method 1
A center conductor or pin is axially mounted within the bores of the drilled holes and these are encapsulated with in a glass substrate which are heated to provide a hermetic seal
Implementation Method 2
VIAs may be evaporated by lasers. Laser-drilled VIAs typically have an inferior surface finish inside the hole
Data Source
AI summary
A broadband surface mounting package includes a housing having a flat bottom wall forming parallel first and second surfaces. An integral wall forms, with the bottom wall, an enclosure having a top opening to provide access to an interior compartment or cavity to receive a microwave component. The second surface is arranged to contact a printed circuit board (PCB) for attachment to lands or pads on the PCB. Cylindrical holes in the enclosure each defines an axis parallel to the bottom wall, and has a dimension, generally transverse to the bottom wall, to extend from the second surface to at least the first surface, and has an axial length sufficient to provide a through hole in the wall and a gap within the bottom wall proximate to and inwardly from the wall. A J-shaped conductive element in the form of a pin is hermetically sealed within the hole and each generally extends along a direction parallel to the axis and has a contact surface coextensive with the second surface, and a connection surface exposed within the cavity to which an electrical connection can be made. A cover selectively closes and hermetically seals the top opening after the microwave component(s) has been secured within the compartment and internal connections have been made. The J-shaped conductive elements are configured to promote impedance matching and to reduce microwave signal losses when said enclosure is surface mounted on a PCB. A method of making the package is disclosed.