Printed Circuit Assembly Strain Limits during Bed of Nails Testing
Bed-of-nails test fixtures demand empirical strain gauge verification to ensure dynamic microstrain levels stay below component limits and prevent latent pad cratering.
Microsection Failure Analysis
Destructive Verification
Visual inspection of a sliced and polished sample reveals internal defects deep within the copper structures of a circuit panel. A microsection failure analysis begins by embedding a targeted board slice in clear epoxy resin to provide structural support during the grinding sequence. This procedure is the standard for identifying cracks in buried vias or intermetallic inconsistencies in solder joints.
Sample Preparation
Technicians grind the sample through sequential abrasive steps until the specific target of interest is reached on a flat lateral plane. During microsection failure analysis, microscopic examination at magnifications up to one thousand times shows the grain structure of the solder and the thickness of plated walls. Accurate polishing is required to prevent the smearing of soft copper into the softer resin, which would obscure tiny cracks.
Digital imaging software measures specific widths such as copper thickness at the knee of a via or the depth of a laser-ablated hole. This factual data confirms whether the fabrication meets the minimum build requirements set by organizations like IPC. Because the sample is destroyed during the procedure, this method stays reserved for small percentages of a run or high value failure evaluations.
Structural Assessment
Evidence of thermal stress shows up as barrel cracking or corner fractures that are impossible to see with X-ray tools. Final results include measurements of every interface layer.