In Circuit Test Nodal Access Layout Rules for Assembly Verification
Ensuring complete bottom-side nodal access with standard pad pitch and strain-mitigated fixturing locks in fault coverage and prevents field defect escapes.
Strain Gauge Testing
Mechanical Analysis
Analytical procedure used to measure the physical deformation of a printed circuit board during assembly, shipping, installation or thermal cycling. Conducting strain gauge testing involves bonding small resistive sensors to the board surface and monitoring their change in resistance as the board flexes. This method quantifies the stress placed on sensitive components like ball grid arrays and ceramic capacitors.
Assembly Process
High stress events often occur during depanelization, connector insertion, press-fit application or the mounting of heavy heat sinks. By performing strain gauge testing, engineers identify which steps in the manufacturing line exceed the allowable limits for the solder joints. The sensors are usually placed near the corners of large components where the strain is most concentrated.
Real time data capture allows the production team to adjust the support fixtures or the speed of the routing bit.
Compliance Requirement
Industry standards like IPC/JEDEC-9704 provide the threshold values and methodologies for these measurements. Verification through strain gauge testing ensures that the board design and the manufacturing process together produce a reliable product. Passing these tests reduces the risk of latent defects such as pad cratering or trace fractures that might only appear after the product is in use.
Results are typically reported as microstrain.