Triaxial Strain Rosette Signal Analysis for In-Circuit Test Fixture Qualification
Triaxial strain rosette signal analysis qualifies ICT fixtures by resolving multi-axis strain rates against IPC/JEDEC-9704 limits to prevent solder cracking.
Principal Strain Analysis
Vector Determination
The calculation of maximum and minimum normal stresses acting on a circuit board at a specific point during assembly or handling provides a clear picture of the risk to solder joints. Principal strain analysis uses data from three element strain gauge rosettes to find the magnitude and direction of the greatest stretching or compression. This method ignores the arbitrary orientation of the gauge and finds the absolute peak strain that the material experiences.
Failure Prediction
Comparing the calculated values against the known limits of the solder and laminate allows engineers to identify hazardous process steps. During principal strain analysis, the peak values are often found during the break off of the assembly from the panel or during the insertion of heavy connectors. High strain levels at these stages indicate a high probability of cracked components or torn pads.
Design Optimization
Adjusting the layout of the components or the placement of the support pins can lower the stresses identified during the testing phase. If the principal strain analysis shows that a sensitive ceramic capacitor is located in a high stress area, the component is moved to a neutral axis of the board. This iterative process ensures that the finished product can survive the mechanical shocks of the manufacturing environment.
Engineers use the resulting data to set hard limits for the manufacturing team to ensure every batch is processed within the safe operating window.