Miniature Planar Rosette Strain Gage Pattern Introduced For PCB Testing

The Micro-Measurements brand of Vishay Precision Group, experts in the design, development, and manufacture of resistive-foil sensors for high-precision strain measurements, has announced the introduction of its S5198, a miniature rectangular planar rosette strain gage pattern for Printed Circuit Board (PCB) testing, incorporating Advanced Sensors Technology.

PCB’s remain among the most essential components of today’s automotive, aerospace, and consumer electronic products.

Industry trends continue toward the adoption of RoHS compliant assembly technologies, including lead-free soldering techniques. At the same time, next-gen manufacturing processes are calling for thinner board designs and newer laminate material types. Both trends have increased PCB failure risks, due to added potential for over-flexure in the manufacturing process.

With many PCB assemblers operating under customer specified strain levels, any over-flexure can lead to interconnection damage, premature field failures and product returns. As a result, manufacturers are increasing supply chain requirements for PCB mechanical stability testing.

Offered in two strain gage designations (C5K-XX-S5198-350/33F and C5K-XX-S5198-350/39F), the Micro-Measurements S5198 pattern provides precise strain detection with minimized non-uniform PCA strain gradient effects, along with reliable operation to +200°C.

A resistance specification of 350Ω, as compared to the 120Ω typical industry standard, reduces the unwanted self-heating and heat dissipation effects commonly found among substrates with poor heat conductivity, such as PCB’s.

A reduced overall footprint, with grid length of just 0.36mm, facilitates ease of target board placement and integration. The S5198 pattern is further supported by pre-attached high-performance Teflon insulated flexible thin cables, consisting of three twisted wires per grid. The wires are color coded, stripped and tinned for ease of PCB wire routing and connection to data acquisition systems.

In addition to PCB testing, the pattern is suitable for Ball Grid Array (BGA) component testing, spherical bend testing, mechanical shock testing, PCB flexures, and In-Circuit Testing (ICT). The S5198 is RoHS compliant and is utilized in accordance with IPC–JEDEC 9702, IPC–JEDEC 9704, and JEDEC JESD22-B111 standards.

The Micro-Measurements Advanced Sensors Technology portfolio includes linear, shear and circular strain gages, in individual, half- and full-bridge configurations and in ranges from 350-20kΩ, with added flexibility in mounting options.

Application of this VPG proprietary technology improves grid-to-grid tolerances and matching over traditional strain gage manufacturing techniques, enabling better sensor performance.

In the case of full-bridge gage configurations, all intra-bridge connections are integrated directly into the pattern itself, eliminating the need for traditional intra-bridge soldering.

The addition of gold-plated solder pads improves solder-joint reliability, while reducing the risks of solder pad oxidation prior to lead wire attachment.

These processes further ensure the close matching of grid-to-grid thermal characteristics and bridge circuit thermal output cancellation specifications, both of which are essential to strain gage measurement accuracy.