Optimizing PCB Testing with the Latest 3-Element Stacked Rosette Strain Gauge Technology

Optimizing PCB Testing with the Latest 3-Element Stacked Rosette Strain Gauge Technology

As the demand for thinner, smaller, and more densely populated PCBs increases, Micro-Measurements' new G1350A perfectly fits the bill for evaluating PCBs' stress. Thanks to the flex circuit and pre-attached lead wires, it features a compact design and significantly simplifies the installation process.

A stacked rosette strain gauge is a particular strain gauge designed to measure the typical strains along different directions at a single point. A regular strain gauge measures the deformation or strain of a material in one direction. In contrast, a rosette strain gauge, composed of multiple strain gauges, can measure strain in multiple directions. A stacked rosette strain gauge consists of several individual strain gauges stacked on each other, each oriented in a different direction to measure the strains in various directions at a single point. The stacked rosette configuration allows for a more compact design compared to a planar rosette, where the gauges are arranged next to each other.

Usage on Printed Circuit Boards (PCBs):
  • Quality Control: During the manufacturing of PCBs, there may be internal stresses generated due to various processes such as lamination, soldering, etc. These stresses may lead to the PCB's warping, bending, or even cracking. Stacked rosette strain gauges can measure these internal strains at critical points on the PCB to ensure they are within the permissible limits.
  • Design Validation: During the design phase of PCBs, engineers use finite element analysis to model and predict the strains and stresses that the PCB will be subjected to during its operation. By attaching stacked rosette strain gauges to the prototype PCBs and subjecting them to real-world operating conditions, engineers can measure the actual strains experienced by the PCB and compare them with the predicted values from the model, helping in validating the design and making any necessary modifications before mass production.
  • Failure Analysis: When a PCB fails during operation, it is essential to understand the cause of the failure to make necessary design modifications and prevent similar failures in the future. Stacked rosette strain gauges can be attached to the PCB at locations suspected of experiencing high stresses or strains. By subjecting the PCB to the operating conditions that led to the failure, engineers can measure the strains at these critical points and determine if they were the cause of the failure.
  • Thermal Expansion Measurement: PCBs often have components that generate heat during operation, which can cause thermal expansion of the material. This thermal expansion can lead to mechanical stresses and strains on the PCB and its components. Stacked rosette strain gauges can measure these strains accurately and help design PCBs that can withstand these thermal expansions without failure.

Micro-Measurements' G1350A Features:

  • Round shaped to facilitate spot installation.
  • Minimal form factor of 5.1mm diameter.
  • Readily available resistance values: 120 ohm (C4A) + 350 ohm (C4K).
  • Flex circuit connection for the most flexible and comfortable gage installation (50mm and 300mm).
  • Pre-attached lead wires: 1m or 3m length, 2 or 3 wire configuration.
  • Highly compatible with StrainSmart® software for PCB testing application features.
AP Corp.
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