Visual artifactA charred hole is found at a high current (High ≥ 1 A) connector location.
EvaluationIn order to entirely burn away PCB base material a very intense arcing environment for ~1 min is required. For a 1.574 mm thick FR4 laminate this can occur with 39 J for 9 s to ignite and 47 J to sustain a flame for 11 s. This flame is capable of carbonizing the material that can fall out and leave a hole. For a 1.574 mm thick CEM-1 laminate this can occur with 27 J for 6 s to ignite and 157 J to sustain a flame for 35 s that is capable of carbonizing the material that can fall out an leave a hole. See experiments #5, #9a and #9b of Chap. 14 for comparative details.