Experimental studies of: Laminate composition, drill bit wear out, and chloride ion concentration as factors affecting CAF formation rate

In industrial, aerospace, medical and other mission critical electronics employing high density interconnection PCBs, high DC voltage gradient and adverse environmental conditions facilitate Conductive Anodic Filament (CAF) formation. To prevent catastrophic failures caused by CAF short circuits, monitoring of manufacturing process and proper laminate selection is essential. The purpose of presented work was to evaluate CAF resistance level of FR4, low CTE, CAF resistant and BT/epoxy-based laminates. Test coupons comprising 90 potential hole-hole failure points with 250 μm spacing were fabricated and subjected to accelerated CAF test for 600 h in 85 °C, 87% RH. Surface insulation resistance measurements were performed to monitor coupons' condition. Time to failure of examined samples, microscopic inspection results and failure root-cause analysis are presented.