Flexural Evaluation
Mechanical test configurations apply controlled bending moments to a specimen to determine its flexural strength and elastic modulus. Utilizing four-point bending distributes the load across two inner span points, which creates a region of uniform bending moment and zero shear force between those points. This uniform region makes the test highly effective for evaluating the structural integrity of surface-mounted components and their solder interconnects under board-level stress.
The absence of shear force in the evaluation zone simplifies strain analysis and improves repeatability.
Fixture Alignment
Support and loading anvils require precise alignment to prevent twisting or asymmetric load application to the circuit card. When configuring four-point bending, the span distances must be verified to ensure that the bending moment calculations remain valid across all tested boards. Friction at the contact points can introduce small measurement errors, which are minimized by using freely rotating rollers as supports.
Strain Monitoring
Electric resistance strain gauges mounted to the printed circuit board monitor the surface strain during loading. This feedback allows operators to adjust the crosshead speed of the test machine to match specific strain rates required by industrial standards.
Metrological Calibration
Load cells require periodic calibration against traceable reference weights to maintain force accuracy. This verification ensures that force data collected during bending matches national standards.
