Spring-Loaded Rivet Clamping for Radar Waveguide PCBAs
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Solution Overview
Problem
Conventional fasteners such as screws and bolts used to secure waveguides to printed circuit board assemblies (PCBAs) in radar sensors fail to adequately accommodate thermal expansion, contraction, and creeping, leading to loss of clamping force and undesirable gaps that compromise the effectiveness of the connection.
Innovation Solution
A spring-loaded rivet with an elastic material section that provides a flexible clamping force, accommodating thermal expansion and contraction, and reduces creeping, ensuring a constant connection between the waveguide and PCBA.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional rigid fasteners (screws or bolts) are used to secure the PCBA and waveguide together, then the fastening strength is initially high, but the clamping force is lost over time due to creeping and thermal expansion/contraction
Solution Approach 1:
The patent replaces rigid fasteners with a spring-loaded rivet system where the spring element provides dynamic compliance. The spring continuously adjusts to thermal expansion and contraction while maintaining constant clamping force, preventing the creeping phenomenon that plagues rigid fasteners. The spring's elastic deformation absorbs dimensional changes without losing fastening effectiveness.
Solution Approach 2:
The invention changes the mechanical parameter of the fastener from rigid (zero compliance) to elastic (controlled compliance). The spring element's stiffness is specifically designed to accommodate the thermal expansion differences between the PCBA and waveguide while maintaining sufficient clamping force. This parameter change transforms the fastener from a static component to one that dynamically adapts to thermal and mechanical stresses.
2Strength
If the waveguide and PCBA are secured with conventional fasteners, then the initial connection is secure, but thermal expansion and contraction cause the fastener to work loose over time
Solution Approach 1:
The spring-loaded rivet provides continuous dynamic adjustment to maintain connection security. As the waveguide and PCBA expand and contract thermally, the spring compresses and extends accordingly, preventing the fastener from working loose. This dynamic mechanism ensures the connection remains secure throughout the entire service life of the assembly.
Solution Approach 2:
The spring element acts as a pre-configured cushion against thermal expansion and contraction. By designing the spring with appropriate initial compression and stiffness, the system is pre-prepared to absorb dimensional changes before they cause fastener loosening. This beforehand cushioning prevents the progressive loss of clamping force that occurs with conventional fasteners.
3Force
If rigid fasteners are used to secure the PCBA and waveguide, then the fastening force is initially high, but shear stresses from thermal expansion negatively affect fastener effectiveness
Solution Approach 1:
The invention changes the fastener's mechanical parameter from rigid to elastic, allowing it to accommodate shear stresses from thermal expansion. The spring element's compliance enables it to absorb dimensional changes without transmitting harmful shear forces to the PCBA or waveguide, while maintaining adequate fastening force throughout thermal cycles.
Solution Approach 2:
The spring element acts as an intermediary between the PCBA and waveguide, decoupling their thermal expansion behaviors. Instead of rigidly transmitting shear stresses between the two components, the spring absorbs these stresses through elastic deformation, protecting both components from thermal-induced shear damage while maintaining their mechanical connection.
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 spring-loaded rivet maintains a gapless connection, reduces electromagnetic interference, and enhances the reliability and longevity of the assembly by accommodating thermal changes and mechanical stresses.
Implementation Method 1
The spring element compresses during waveguide and PCBA expansion and elongates during waveguide and PCBA contraction to provide a constant rivet clamping force
Implementation Method 2
The mandrel shank is pulled through the rivet head, causing the mandrel head to deform the rivet tail toward the rivet head
Implementation Method 3
Thermal expansion and contraction also contribute to creeping and occurs where the waveguide, PCBA, and/or the fastener have different coefficients of thermal expansion (CTE)
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
A printed circuit board assembly (PCBA) waveguide assembly comprises a PCBA, a waveguide, and a spring-loaded rivet. The spring-loaded rivet comprises a rivet head, a rivet shank, a rivet tail, and a spring element and fastens the PBCA to the waveguide. The spring element provides flexibility in the clamping force of the rivet to accommodate thermal expansion and contraction, creeping and shear forces experienced by the PCBA and waveguide.