Small-Scale Strain Sensors Designed for PCB Reliability Testing

Cracks in the PCBs — brittle fractures in solder and even across components, particularly around BGAs — can be induced by in-circuit test fixtures and during assembly, burn-in and testing, system integration, and packaging and shipping. Strain measurements should be made after all design iterations of the PCB, including changes to on-board components, which may alter thermal stress loading. This is especially useful when introducing new solder materials and processes, which may have a different stiffness and introduce a different soldering thermal profile. The miniaturization of consumer electronics — and consequent increase in component density — results in larger thermal stresses, new requirements for surviving repeated loadings, and a greater need for impact stress survival. Meeting these specifications requires accurate knowledge of strains in the PCB and on-board components. Strain gage measurement is the quickest, most accurate, and most cost-effective method for identifying strains on a PCB, and can be used in developing loading fixtures and test plans to optimize the testing phase.

The solution is miniature-scale strain gage (gauge) sensors designed to meet the growing demand for precise, stable, and reliable stress analysis of PCBs, even in harsh environments. The C2A-06-G1350-120 rectangular rosette gage and C2A-06-015LW-120 uniaxial linear gage are designed to detect PCB surface strains at critical locations in consumer electronics.

The C2A-06-G1350-120 is a stacked rosette gage with a compact 5 mm diameter matrix and 3 meters of three-conductor cable to eliminate lead wire soldering after bonding. Micro-Measurements' Advanced Sensors strain gage technology makes even smaller planar rosettes possible for use in surface-mounting applications with restricted areas, as well as for intra-laminar strain measurement. The uniaxial linear C2A-06-015LW-120 is supplied with pre-attached cables and features an active grid length of just 0.015 in and an overall matrix of 1.4 mm by 1.9 mm. The device is ideal for installation on surface-mount components.

Please visit the datasheets for more information:

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Jim Weidner

Chief Applications Engineer