Sheet Dielectric Defect-Location Probe
Original Publication Date: 1986-Aug-01
Included in the Prior Art Database: 2005-Mar-09
Sheet dielectrics, used in the construction of a laminated multilayer electrical printed circuit board (PCB), or the like, are commonly made of woven fiber glass cloth and an epoxy wetting agent. These dielectrics are often non-homogeneous after curing and contain defects caused by entrapped contaminants, or areas of voids (i.e., epoxy starvation sites that result in air gaps) which compromise the dielectric isolation integrity of the sheet. An electrical probe that locates these dielectric defects in epoxy/glass sheets is described below. As seen in Fig. 1, the probe 1 has a one-inch diameter circular copper plane 2 with an insulated reinforcement plate 3. An insulated handle 4 has a voltage jack terminal 5 to connect a voltage source, and handle 4 contains an indicator lamp 6 and current (leaking)-limiting resistor 7.