Abstract: Apparatus and methods are disclosed for inspecting unsintered single or multiple layer ceramic specimens containing or carrying metal paste patterns of the type commonly used to ultimately form laminated multilayer ceramic (MLC) carriers for large scale integrated (LSI) chips. A relatively large surface area of an unsintered ceramic specimen (large in comparison with the minimum feature size of the paste patterns) is temporarily electrically contacted with a conforming electrode. The conforming electrode makes non-damaging electrical contact to any metallic paste exposed at the contacted area. Electric charge is either collected or delivered by this electrode, depending upon the mode of operation.

Abstract: I have discovered that an electron beam emitted from an LaB.sub.6 single crystal cathode has higher brightness when a significant portion of the actual emitting surface of the LaB.sub.6 crystal comprises flat surfaces oblique to the electron beam axis and when these flat surfaces expose relatively low work function crystal planes. I have defined as a relatively low work function crystal plane those crystal planes having a lower work function than the average work function for sintered LaB.sub.6. My preferred geometry for a single crystal LaB.sub.6 electron emitting tip is a pyramid oriented such that the apex points in the electron beam emission direction and preferably also points in a direction perpendicular to a relatively low work function crystal plane. The pyramidal tip may have three, four, or more flat sides, all of which contribute electrons to the beam, from at least an area in the vicinity of the apex. The apex of the pyramid may be rounded or flat.

Abstract: The shape of an electron beam emitted from an LaB.sub.6 single crystal cathode can be controlled directly by shaping the cathode tip itself. The LaB.sub.6 cathode is provided with a flat top surface which is substantially perpendicular to the emitted beam direction and which corresponds in shape to the shape of the beam desired. For a square beam the flat top surface is square in shape. The size of the shaped top surface and operating conditions are arranged such that emission of electrons occurs over substantially the entire shaped top surface with minimum emission from side regions of the tip adjacent to this shaped surface. In order to maximize emission from the shaped top surface, a crystallographic orientation is selected such that the shaped top surface exposes a relatively low work function crystal plane. Emission from side regions of the tip adjacent to the shaped high emission surface may be reduced by orienting such side regions very obliquely to the emitted beam axis.

Abstract: The electron potential of an electron beam is switched between different values without moving the focal plane by effectively changing the axial position of the electron source at the same time that the electron potential is changed. The effective change in axial position of the electron source exactly compensates for the altered effectiveness which magnetic lenses have upon an electron beam of altered electron potential such that the final focal plane remains at the same position without adjusting the field strength of any magnetic lens.