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Sheet Dielectric Defect-Location Probe

IP.com Disclosure Number: IPCOM000061442D
Original Publication Date: 1986-Aug-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 2 page(s) / 30K

Publishing Venue

IBM

Related People

Malack, JA: AUTHOR

Abstract

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.

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Sheet Dielectric Defect-Location Probe

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. Handle top 8 is made of transparent material and is removable to observe the lamp 6 "on/off" condition and allow change/removal of resistor 7. Depending upon the application, the current-limiting resistor 7 is designed for a fixed value of operating voltage or it has a multi-value capability for a range of voltages using a set of selectable resistors on a multi-position switch mounted on probe 1. A dielectric sheet 9 (Fig. 2) is placed over a copper ground plane 10 of area/size equal to or greater than the sheet. The probe 1 is placed on top of sheet 9 and a DC power supply (+VDC) is connected to terminal 5 a...