Method and apparatus for through hole substrate printing

Claim 1

A method not only of controllably forming coatings of a printing substance on through holes in insulative substrates but also of concurrently determining variations in quality of the coated substrate, comprising the steps of: placing a face of an insulative substrate having through-holes therein on a holder while leaving the opposite face of the substrate exposed to atmospheric air, said holder having a first vacuum area, that does not register with said through-holes and is used for hold-down of said insulative substrate on said holder, and a second vacuum area, for registration with said through-holes; drawing a vacuum in said first vacuum area to secure said insulative substrate to said holder; depositing a printing substrate over portions of the insulative substrate having said through-holes; producing a predetermined vacuum in a plenum of predetermined volume for exposure to the second vacuum area; terminating evacuation of said plenum after establishing said predetermined plenum vacuum; without resuming said plenum evacuation, exposing said second area to said predetermined plenum vacuum, effective to cause said printing substance to be pulled into said through-holes in a highly controlled manner, and thereby produce a highly controlled coating on substrate walls forming said through holes; measuring pressure in said plenum at one or more preselected times during a period immediately following exposure of the second vacuum area to the predetermined plenum vacuum; and comparing each such measured plenum pressure to a reference pressure, whereby potentially unsatisfactory coated insulative substrates are identified.

Claim 2

A method not only of controllably forming coatings of a printing substance on through holes in insulative substrates but also of concurrently determining variations in quality of the coated substrate, comprising the steps of: placing a face of an insulative substrate having through-holes therein on a holder while leaving the opposite face of the substrate exposed to atmospheric air, said holder having a first vacuum area, that does not register with said through-holes and is used for hold-down of said insulative substrate on said holder, and a second vacuum area, for registration with said through-holes; drawing a vacuum in said first vacuum area to secure said insulative substrate to said holder; depositing a printing substrate over portions of the insulative substrate having said through-holes; producing a predetermined vacuum in a plenum of predetermined volume for exposure to the second vacuum area; terminating evacuation of said plenum after establishing said predetermined plenum vacuum; without resuming said plenum evacuation, exposing said second area to said predetermined plenum vacuum, effective to cause said printing substance to be pulled into said through-holes in a highly controlled manner, and thereby produce a highly controlled coating on substrate walls forming said through holes; measuring pressure in said plenum at one or more preselected times during a period immediately following exposure of the second vacuum area to the predetermined plenum vacuum; and comparing each such measured plenum pressure to a reference pressure, whereby potentially unsatisfactory coated insulative substrates are identified.

Claim 3

A method not only of controllably printing coatings on walls forming through-holes in a ceramic substrate for an electrical circuit but also of concurrently determining variations in quality of the coated substrate, comprising the steps of: placing a flat ceramic substrate for an electrical circuit on a holder which defines a vacuum hold-down area adjacent one or more edges of the substrate, and further defines a second vacuum area spaced inwardly on said substrate from said edges and registering with through-holes in said ceramic substrate that are to receive a coating thereon; drawing a vacuum in said vacuum hold-down area of said holder while an opposite face of said substrate is exposed to atmospheric air, to secure said substrate to said holder; printing a paste over portions of said opposite face of said substrate having said through-holes; producing a predetermined vacuum in a plenum of predetermined volume for exposure to the second vacuum area; discontinuing evacuation of said plenum after establishing said predetermined plenum vacuum; thereafter exposing said second area of said holder to said predetermined plenum vacuum, to pull said paste into and through said through-holes in a highly controlled manner, and thereby produce a coating of highly controlled thickness on substrate walls forming said through-holes; monitoring pressure in said plenum at selected intervals during a time period immediately following exposure of the second vacuum area to the predetermined plenum vacuum, to produce a measured time-pressure profile; and comparing said measured time-pressure profile to a reference time-pressure profile, to identify substrates producing unacceptable deviations in said predetermined plenum vacuum from said reference time-pressure profile during said period immediately following exposure of said second vacuum area to said predetermined plenum volume.

Claim 4

A method not only of controllably printing coatings on walls forming through-holes in a ceramic substrate for an electrical circuit but also of concurrently determining variations in quality of the coated substrate, comprising the steps of: placing a flat ceramic substrate for an electrical circuit on a holder which defines a vacuum hold-down area adjacent one or more edges of the substrate, and further defines a second vacuum area spaced inwardly on said substrate from said edges and registering with through-holes in said ceramic substrate that are to receive a coating thereon; drawing a vacuum in said vacuum hold-down area of said holder while an opposite face of said substrate is exposed to atmospheric air, to secure said substrate to said holder; printing a paste over portions of said opposite face of said substrate having said through-holes; producing a predetermined vacuum in a plenum of predetermined volume for exposure to the second vacuum area; discontinuing evacuation of said plenum after establishing said predetermined plenum vacuum; thereafter exposing said second area of said holder to said predetermined plenum vacuum, to pull said paste into and through said through-holes in a highly controlled manner, and thereby produce a coating of highly controlled thickness on substrate walls forming said through-holes; monitoring pressure in said plenum at selected intervals during a time period immediately following exposure of the second vacuum area to the predetermined plenum vacuum, to produce a measured time-pressure profile; and comparing said measured time-pressure profile to a reference time-pressure profile, to identify substrates producing unacceptable deviations in said predetermined plenum vacuum from said reference time-pressure profile during said period immediately following exposure of said second vacuum area to said predetermined plenum volume.