Embedded PCB Strain Gauges for Accurate Monitoring
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Solution Overview
Problem
Existing strain gauges for monitoring strain in printed circuits face challenges in gathering accurate data due to adherence issues and inability to alert users about excessive strain, leading to potential reliability problems in electronic devices.
Innovation Solution
Embedding strain gauges formed from metal traces on polymer substrates within recesses of printed circuit boards, integrated into a bridge circuit, allows for accurate strain measurements and real-time monitoring of solder ball joints, enhancing data accuracy and alerting mechanisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If strain gauges are mounted on the surface of the printed circuit board, then strain data can be gathered, but the measurements are influenced by adherence issues and other variables that reduce accuracy
Solution Approach 1:
The strain gauge is merged with the printed circuit board by embedding it within recesses in the PCB layers. The polymer substrate of the strain gauge is mounted within recesses in the first rigid printed circuit layer, and additional rigid printed circuit layers are laminated over the strain gauge, integrating it into the PCB structure itself rather than mounting it separately on the surface.
Solution Approach 2:
The polymer substrate acts as an intermediary between the strain gauge resistor and the rigid printed circuit layers. The strain gauge is mounted on the polymer substrate, which is then embedded in recesses of the PCB, providing a stable mounting surface that isolates the strain gauge from direct contact with the rigid PCB material while maintaining mechanical coupling for accurate strain measurement.
2Loss of information
If external strain gauges are used to monitor strain, then strain data can be collected, but the system cannot alert users about excessive strain in real-time
Solution Approach 1:
The strain gauge is integrated into the electronic device with connection to a processor that receives strain data and can provide feedback alerts to the user. The system includes a processor configured to receive strain data from the embedded strain gauge and output an alert when the strain data indicates that a component is experiencing excessive strain, enabling real-time monitoring and warning capabilities.
3Measurement precision
If strain gauges are embedded within printed circuit layers, then measurement accuracy improves, but manufacturing complexity increases
Solution Approach 1:
Recesses for the strain gauge are formed in the rigid printed circuit layer before the strain gauge is mounted. The polymer substrate with the strain gauge is then placed into the pre-formed recesses, and additional PCB layers are laminated over it. This preliminary preparation of recesses simplifies the embedding process compared to attempting to create recesses after assembly.
Solution Approach 2:
The strain gauge structure is nested within the printed circuit board layers. The polymer substrate containing the strain gauge resistor is embedded within recesses in the first rigid printed circuit layer, and additional rigid printed circuit layers are laminated between which the strain gauge is embedded, creating a nested configuration that protects the strain gauge while maintaining access to its terminals.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution provides improved strain data accuracy and real-time monitoring capabilities, enabling better design enhancements and reliability improvements for electronic devices by embedding strain gauges within printed circuit boards, reducing the risk of damage from excessive strain.
Implementation Method 1
The metal trace may form a variable strain gauge resistor that may be incorporated into a bridge circuit for the strain gauge
Data Source
AI summary
A printed circuit board may have embedded strain gauges. A strain gauge may be formed from a metal trace on a polymer substrate. The metal trace may form a variable strain gauge resistor that is incorporated into a bridge circuit for a strain gauge. The printed circuit may have a rigid printed circuit layer with a recess that receives the polymer substrate. Metal pads on the polymer substrate may be coupled to respective ends of the variable strain gauge resistor. The rigid printed circuit substrate with the recess may be laminated between additional rigid printed circuit layers. Vias may be formed through the additional rigid printed circuit layers to contact the metal pads. Embedded strain gauges may be used in gathering strain data when strain is imparted to a printed circuit during use of the printed circuit in an electronic device or during testing.