Metal-Supported RF Filter Assembly for Thermal Stress Relief
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Solution Overview
Problem
Conventional RF filter assemblies for antennas suffer from solder cracks due to thermal expansion differences between the FR4 board and ceramic filters, leading to electrical shorts and performance deterioration.
Innovation Solution
An RF filter assembly with a metal filter support member that separates ceramic waveguide filters from the main board, minimizing solder area and using a metal material to reduce thermal stress, ensuring uniform and precise arrangement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If solder cream is thickly formed to prevent short failure, then electrical short prevention is improved, but solder crack occurrence increases due to thermal expansion difference
Solution Approach 1:
A metal support member is introduced as an intermediary component between the RF filter and the main board. This mediator has a coefficient of thermal expansion that matches the RF filter, thereby preventing solder cracks while maintaining electrical short prevention functionality.
Solution Approach 2:
The coefficient of thermal expansion parameter is changed by replacing the FR4 board material with a metal support member whose thermal expansion coefficient matches that of the RF filter (8.2 ppm/°C), eliminating the thermal stress that causes solder cracks.
2Ease of manufacture
If FR4 board material is used for main board, then manufacturing ease is improved, but solder crack occurs due to coefficient of expansion mismatch
Solution Approach 1:
The metal support member serves as an intermediary between the RF filter and the FR4 board, isolating the RF filter from the thermally incompatible board material while maintaining assembly feasibility.
Solution Approach 2:
The assembly uses a composite structure combining FR4 board with a metal support member, leveraging the manufacturing ease of FR4 while adding the thermal compatibility of metal to prevent solder cracks.
3Device complexity
If multiple RF filters are mounted directly on main board, then device complexity is reduced, but electrical short risk increases due to direct contact
Solution Approach 1:
The metal support member acts as a mediator that provides both mechanical support and electrical isolation, preventing direct contact between RF filters and the main board while maintaining a relatively simple overall structure.
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
Minimizes solder cracks, prevents electrical shorts, and enhances reliability by maintaining stable signal flow and uniform filter arrangement.
Implementation Method 1
a crack occurs at a predetermined portion of the solder cream 30 that is disposed between the board for fixing 5 and the RF filter 20 due to the generation of system heat within an antenna housing body (not illustrated) in which the RF filter assembly 1 for an antenna according to a conventional technology is installed, because of a difference in the coefficient of expansion (e.g., the coefficient of expansion of the board for fixing 5 is 17 ppm/° C., and the coefficient of expansion of the RF filter that is the ceramic material is 8.2 ppm/° C.)
Data Source
AI summary
The present invention relates to an RF filter assembly for an antenna. Particularly, the RF filter assembly for an antenna comprises: a main board on which a plurality of electronic components are mounted; a plurality of RF filters which are installed on one surface of the main board; and a filter support member which is disposed between the main board and the plurality of RF filters, is made of a metal material, and separates each of the plurality of RF filters in the direction of the one surface of the main board. Thereby, the present invention provides advantages of preventing the occurrence of cracks in solder cream caused by differences in thermal expansion coefficients between the main board and each RF filter, and also, enabling a more precise RF filter arrangement, and improving product reliability.