Micromachined RF Filter Enclosure with Bonding Bumps for Ground Reference
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Solution Overview
Problem
Producing high-frequency filters with high Q and low insertion loss that are stable over temperature extremes and have repeatable performance characteristics is challenging, especially in manufacturing such filters to yield consistent performance.
Innovation Solution
A semiconductor technology-based filter design featuring a dielectric substrate with metal traces for frequency selective circuits and a top enclosure with metal bonding bumps that form a common reference ground, providing electromagnetic shielding and stable performance across temperature extremes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional materials and techniques are used to construct high-frequency filters, then manufacturing flexibility is maintained, but achieving high Q, low insertion loss, and temperature stability becomes challenging
Solution Approach 1:
The patent combines multiple functions into a single integrated enclosure structure: electromagnetic shielding, mechanical support, and thermal management are all achieved through the micromachined enclosure with metallized surfaces. This integration resolves the contradiction by providing reliable filter performance through combined functions while maintaining ease of manufacture through a single component rather than multiple separate elements.
Solution Approach 2:
The patent utilizes micromachining techniques to precisely control the geometric parameters of the enclosure, including wall thickness, recess dimensions, and surface flatness. By changing and precisely controlling these physical parameters through semiconductor fabrication processes, the patent achieves both high performance reliability and manufacturing repeatability that cannot be obtained through traditional machining methods.
2Manufacturing precision
If micromachined enclosures with metallized surfaces are used, then electromagnetic shielding and performance repeatability are improved, but manufacturing complexity increases
Solution Approach 1:
The micromachined enclosure serves multiple functions simultaneously: it provides electromagnetic shielding through metallized surfaces, mechanical support for the filter assembly, thermal management pathways, and precise dimensional references for component alignment. This multi-functionality reduces the need for separate components, thereby offsetting the increased fabrication complexity with reduced assembly complexity.
Solution Approach 2:
The patent replaces traditional mechanical machining operations with semiconductor micromachining and metallization processes. Instead of using mechanical mills and lathes to create the enclosure, the patent uses photolithography, etching, and vapor deposition techniques. This substitution enables superior dimensional consistency and surface quality while the standardized semiconductor fabrication processes actually reduce overall manufacturing complexity through automation and repeatability.
3Object-affected harmful factors
If bonding bumps are used to establish common reference ground, then electromagnetic shielding effectiveness is improved, but assembly complexity increases
Solution Approach 1:
The bonding bumps merge multiple functions: they provide mechanical attachment between the enclosure and substrate, establish electrical connectivity for the common reference ground, and ensure thermal contact. By combining these functions into a single bonding feature, the patent improves electromagnetic shielding effectiveness without proportionally increasing assembly complexity, as the same bonding process achieves all three objectives simultaneously.
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 high Q and low insertion loss with repeatable performance characteristics, effectively addressing the challenges of stability and manufacturability in high-frequency filters.
Implementation Method 1
all interior surfaces of the top enclosure including the substantially planar end area of the top enclosure and the at least one interior recess having a deposited metal coating... The at least one interior recess is dimensioned to enclose the frequency selective RF circuitry to provide electromagnetic shielding for the frequency selective RF circuitry
Implementation Method 2
A conductive bonding agent engages the first substantially planar end area and the aligned metal traces on the one major surface, the conductive bonding agent forming conductive bonds to establish a common reference ground between the deposited metal coating of the top enclosure and the other metal traces
Implementation Method 3
a plurality of metal bonding bumps extends outwardly from the projecting walls of the top enclosure. The bonding bumps on the top enclosure engages reference ground metal traces on respective surfaces of the substrate. As a result of applied pressure, the bonding bumps and respective reference ground metal traces form metal-to-metal conductive bonds
Data Source
AI summary
An exemplary semiconductor technology implemented microwave filter includes a dielectric substrate with metal traces on one surface that function as frequency selective circuits and reference ground. A top enclosure encloses the substrate have respective interior recesses with deposited continuous metal coatings. A plurality of metal bonding bumps or bonding wall extends outwardly from the projecting walls of the bottom and top enclosures. The bonding bumps on the top enclosure engage reference ground metal traces on respective surface of the substrate. As a result of applied pressure, the bonding bumps and respective reference ground metal traces together with the through-substrate vias form a metal-to-metal singly-connected ground reference structure for the entire circuitry.