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Air Squeegee Screening Process for Coating Via Holes in Printed Circuit Boards

IP.com Disclosure Number: IPCOM000101792D
Original Publication Date: 1990-Sep-01
Included in the Prior Art Database: 2005-Mar-16
Document File: 1 page(s) / 41K

Publishing Venue

IBM

Related People

Bowling, JA: AUTHOR [+3]

Abstract

A new method is disclosed for coating through holes and vias with polymer thick film inks in the manufacture of circuit boards.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 100% of the total text.

Air Squeegee Screening Process for Coating Via Holes in Printed Circuit Boards

       A new method is disclosed for coating through holes and
vias with polymer thick film inks in the manufacture of circuit
boards.

      Polymer thick film inks are commonly used for screen printing
of circuit traces onto the surfaces of a substrate. Typically, vacuum
has been used to draw the ink through the holes on thinner substrates
such as those used for membrane switches.  With a thicker substrate
and a large number of holes, it becomes difficult to pull enough ink
through to coat the sidewalls and ensure clear holes with vacuum
alone.

      The process disclosed here utilizes a modified squeegee to push
the ink into the holes in a printed circuit card (as shown in the
drawing).  The modification of the squeegee consists of an air knife
embedded in the blade or attached to the trailing edge of the blade.
Air pressure is used to force the ink through the holes in the
substrate, coating the sidewalls and clearing excess ink from the
hole.  The air pressure can be varied to take into account different
ink viscosities.

      The air squeegee can also be used in conjunction with vacuum
assist when screening viscous inks that are difficult to get into the
holes.  The combination of air pressure and vacuum can also minimize
spatter of the ink on the backside of the substrate.