Ceramic Waveguide-Stripline Assembly for Low-Stress RF Filtering
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Solution Overview
Problem
Conventional ceramic waveguide (CWG) duplexer applications face issues with reliability due to thermal mismatch between CWG and RF PCB materials, and large distances between solder bumps leading to fatigue cracking and failure, while existing solutions like ceramic monoblock and surface acoustic wave filters are lossy and occupy significant PCB area.
Innovation Solution
A composite electronic device is created by bonding a ceramic waveguide (CWG) device with a ceramic stripline (CS) device, minimizing thermal stress through similar CTE materials and short solder connections, and using contact bumps for mechanical support and grounding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional CWG duplexer is mounted on RF PCB with large distance between solder bumps, then mechanical support is adequate, but thermal mismatch causes high stresses and reliability failure
Solution Approach 1:
The patent changes the CTE parameter by selecting a ceramic substrate with CTE of 7-9 ppm/°C that matches the CWG duplexer material, rather than using conventional RF PCB materials with 15 ppm/°C CTE. This parameter change reduces thermal mismatch stress and improves solder bump reliability
Solution Approach 2:
The patent uses a composite structure combining ceramic substrate with copper ground plane and solder bumps, where the ceramic material provides thermal expansion compatibility while the metal layers provide electrical connectivity and mechanical strength
2Loss of energy
If ceramic monoblock or SAW/BAW filters are used for lowpass filtering, then compact size is achieved, but insertion loss increases significantly
Solution Approach 1:
The patent merges the CWG duplexer and lowpass filter into a single integrated ceramic device, eliminating the need for separate filter components. This combination achieves low insertion loss while maintaining compact size, as the integrated structure reduces additional connection losses and component count
3Loss of energy
If CWG duplexer and LPF are manufactured as separate components, then manufacturing flexibility is maintained, but connection losses and PCB area increase
Solution Approach 1:
The patent combines the CWG duplexer and lowpass filter into a single integrated ceramic component with unified manufacturing process. This eliminates inter-component cabling and connection losses, while reducing the overall PCB footprint as both functions occupy the same device footprint
Solution Approach 2:
The integrated ceramic device performs multiple functions (duplexing and lowpass filtering) within a single component, making the system more versatile while reducing the number of discrete components needed and minimizing PCB area occupation
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 composite device achieves reduced thermal stress, improved reliability, and minimal space occupation on the PCB, while maintaining low loss connections.
Implementation Method 1
a ceramic stripline, CS, device comprising at least one stripline transmission path having at least two I/O ports
Implementation Method 2
For conventional CWG materials, the coefficient of thermal expansion (CTE) is about 5ppm/C or less. In contrast, commonly used RF PCBs (such as well known FR4, or Megatron 6) have a CTE of about 15ppm/C. Therefore, there is always a large thermal mismatch between the CWG filter/duplexer and the RF PCB
Data Source
Figure 1
Figure 2A~3B
Figure 4A~4E
AI summary
A composite electronic device comprises a ceramic waveguide, CWG, device having at least two input/output, I/O, ports; and a ceramic stripline, CS, device comprising at least one stripline transmission paths having at least two I/O ports. The CS device is affixed to the CWG device such that at least one of the I/O ports of the CWG device is electrically connected to a corresponding one I/O port of the CS device.