Browse Prior Art Database

Plasma Treatment to Improve Resist Adhesion

IP.com Disclosure Number: IPCOM000109023D
Original Publication Date: 1992-Jul-01
Included in the Prior Art Database: 2005-Mar-23
Document File: 2 page(s) / 82K

Publishing Venue

IBM

Related People

Andrejack, J: AUTHOR [+3]

Abstract

In the fabrication of printed circuit panels, poor photoresist adhesion to the panel results in metal plating under the photoresist which leads to short circuits in the finished panel. The previous approach to improving resist adhesion was to roughen the surface by laminating the panel to a roughened copper layer, then etching away the copper (see Fig. 1A). The scale of roughness practical for reliability transferring from treated copper to a printed circuit board surface is about 25 microns. The 25 micron roughness works well to improve resist adhesion for circuit lines larger than 50 microns, but is too rough for the finer circuit lines required for future products. Plating features less than 50 microns wide on a very rough surface leads to pitted circuit lines with a very uneven cross section.

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Plasma Treatment to Improve Resist Adhesion

       In the fabrication of printed circuit panels, poor
photoresist adhesion to the panel results in metal plating under the
photoresist which leads to short circuits in the finished panel.  The
previous approach to improving resist adhesion was to roughen the
surface by laminating the panel to a roughened copper layer, then
etching away the copper (see Fig. 1A).  The scale of roughness
practical for reliability transferring from treated copper to a
printed circuit board surface is about 25 microns.  The 25 micron
roughness works well to improve resist adhesion for circuit lines
larger than 50 microns, but is too rough for the finer circuit lines
required for future products.  Plating features less than 50 microns
wide on a very rough surface leads to pitted circuit lines with a
very uneven cross section. The electrical characteristics of such a
rough copper deposit are very poor.

      For circuit panels which use a particle filled polymer rather
than a woven glass filler, a new method has been found to improve the
photoresist adhesion.  The new process starts with a smooth surface
and plasma etches the polymer to expose filler particles.  The filler
particles have an average diameter of 10 microns, so the roughness
imparted by partially exposing the filler is on the order of 5
microns, or about 1/5 the scale of the roughness of the previous
process (see Fig. 1B).

      Etching of PTFE in silica-filled PTFE sheets of a practical
size (e.g., 10" x 15") has been demonstrated in two different plasma
reactors to show the...