Small-scale strain gauges test PCB reliability

The miniaturisation of consumer electronics 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 gauge measurement is the quickest, most accurate, and most cost-effective method for identifying strains on a PCB, and it can be used in developing loading fixtures and test plans to optimise the testing phase. 

The C2A-06-G1350-120 is a stacked rosette gauge with a compact 5mm diameter matrix and 3 metres of three-conductor cable to eliminate lead wire soldering after bonding. Micro-Measurements' Advanced Sensors strain gauge 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” and an overall matrix of 1.4x1.9mm. The device is suitable for installation on surface-mount components.

"Cracks in the PCB 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," said Bob Watson, Director of Research and Development, Micro-Measurements. "Strain measurements should be made after all design iterations of the PCB, including changes to on-board components, which may alter thermal stress loading. Combined with Micro-Measurements instrumentation and StrainSmart software, our strain gauges and accessories for PCB testing are IPC/JEDEC-9704-compliant and provide real-time data acquisition of board and component strains. This is especially useful when introducing new solder materials and processes, which may have a different stiffness and introduce a different soldering thermal profile."