Characterization of RF Micro-Coaxial Cable Insertion Loss Degradation
RF micro-coaxial insertion loss escalates through skin-depth resistance, dielectric loss tangent shifts, mechanical flex displacement, and atmospheric oxidation.
Dynamic Flex Fatigue
Meaning
Mechanical degradation occurs when conductive traces or cable cores experience repeated bending during operation. In a cable assembly or flexible circuit, dynamic flex fatigue identifies the cumulative damage that leads to cracks in conductors or insulation. It marks the limit where the physical integrity of the copper yields to mechanical work.
This process ends in an open circuit or a rise in resistance that prevents signal transmission.
Stress Cycle
Bending stresses the outer radius of a curve while compressing the inner radius. When dynamic flex fatigue occurs, the grain structure of the metal changes under these alternating loads. Small fractures appear at the surface and move inward over thousands of movements.
Failure Mechanism
Material hardening often precedes the final break. As the conductor work hardens, it becomes more brittle and less able to absorb the kinetic energy of the bend. Designers specify the number of cycles a part survives before the electrical performance drops below a threshold.
In robotic or hinged applications, the rate of motion determines the speed at which the metal reaches its fatigue limit.
Endurance Qualification
Continuous testing on a rolling mandrel or a weighted oscillating arm confirms the durability of the assembly. A specification for dynamic flex fatigue allows engineers to predict the service life of an interconnect in a moving joint. If the test results show early cracking, the design requires a change in material or a larger bend radius to lower the strain on the metallic atoms.
This qualification is a mandatory step for devices with folding screens or internal hinges that operate thousands of times.