Browse Prior Art Database

Selectively Removing Dielectric Materials

IP.com Disclosure Number: IPCOM000090157D
Original Publication Date: 1969-Feb-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Smith, JF: AUTHOR [+3]

Abstract

In the fabrication of multilayer devices such as printed circuit boards and capacitive memories, a laser is employed to produce tabs for making connections to selected planes of the devices.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 97% of the total text.

Page 1 of 1

Selectively Removing Dielectric Materials

In the fabrication of multilayer devices such as printed circuit boards and capacitive memories, a laser is employed to produce tabs for making connections to selected planes of the devices.

In one process involving a copper-dielectric-copper sandwich structure, portions of the copper are etched away in a conventional manner leaving strips of copper and exposed dielectric in windows. The exposed dielectric must be removed to produce the tabs. A method of removing this exposed dielectric is to dissolve the dielectric by immersing it in a solution such as sulfuric acid. This process is time-consuming as it involves additional steps such as masking portions of the copper layers for protection from the acid bath, removing the mask after dissolving the dielectric, and then rinsing and cleaning the sandwich structure. Another undesirable aspect of this processing operation is that the tabs are often damaged or broken by the handling involved during processing.

By the laser process, the number of steps is reduced, and excessive handling is eliminated thus substantially overcoming the broken tab problem. The laser process involves focusing a CO(2) laser beam on the windows and moving the sandwich structure so that the laser beam traverses the portions of dielectric to be removed. The dielectric absorbs the laser beam at the selected operating wavelength and is thus vaporized. The copper strips reflect and are undamaged by the las...