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Laser Process for Conditioning Hole Walls Drilled Into Fluoropolymer Composites

IP.com Disclosure Number: IPCOM000100964D
Original Publication Date: 1990-Jun-01
Included in the Prior Art Database: 2005-Mar-16
Document File: 2 page(s) / 48K

Publishing Venue

IBM

Related People

Bui, V: AUTHOR [+5]

Abstract

This article describes a method for removing fiber-like stringers caused by mechanically drilling through regions of fluoropolymers. The method also modifies the fluoropolymer surface to make it more receptive to seed and copper plate.

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This is the abbreviated version, containing approximately 81% of the total text.

Laser Process for Conditioning Hole Walls Drilled Into Fluoropolymer Composites

       This article describes a method for removing fiber-like
stringers caused by mechanically drilling through regions of
fluoropolymers.  The method also modifies the fluoropolymer surface
to make it more receptive to seed and copper plate.

      New high-speed circuit boards require low dielectric constant
materials.  Fluoropolymers have the lowest Er and are being
incorporated into circuit boards in numerous ways, such as films,
woven fabrics, porous mattes, fillers and coatings.  When
mechanically drilled, the fluoropolymer does not cut clean and leaves
stringers, which protrude into the drilled hole.  These stringers can
restrict transport of processing solutions into the holes or can act
as obstructions to the insertion of pins once plated.

      The disclosure utilizes a CO2 laser focused at the surface of
each hole to shrink, singe, or vaporize these stringers.  The process
is 75% effective in removing stringers, and the carbonaceous surface
produced makes the fluoropolymer more receptive to seed and plate.

      The process flow is to first do conventional hole clean to
release all the fibers into the PTH.  A copper mask, with the same
hole pattern, is then positioned over the board surface for
protection.  The CO2 laser is focused on surface of the board and
pulsed.  Optimum results were obtained using a 1000W, CO2 laser, a 5"
focal length, 10 pulses of 50...