Browse Prior Art Database

Self Aligning Laser Seeding for Repairing Circuit Opens

IP.com Disclosure Number: IPCOM000108502D
Original Publication Date: 1992-Jun-01
Included in the Prior Art Database: 2005-Mar-22
Document File: 2 page(s) / 87K

Publishing Venue

IBM

Related People

Chen, CJ: AUTHOR [+2]

Abstract

Disclosed is a method to repair circuit opens on printed circuit boards or modules without physically locating the exact coordinates of the circuit open.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Self Aligning Laser Seeding for Repairing Circuit Opens

       Disclosed is a method to repair circuit opens on printed
circuit boards or modules without physically locating the exact
coordinates of the circuit open.

      Using the self-induced repair (SIR) method, the near-opens
(constrictions) in circuits can be self-healed without locating them
(1,2).  Because locating defects is an expensive operation, this
self-locating feature provides a significant cost advantage.  Also
disclosed in (1) is that with any method to form a conducting bridge
across a gap in the circuit, or a circuit open, no matter how poor
its conductance is, the SIR process will make it perfect.  A process
using conventional laser direct writing technique, starting with an
organometallic film, metal films can be made across the gap as the
initial conducting bridge (seeding) to start the SIR process (3,4).
However, the conventional method of generating seeding needs the
information of the coordinates of the gap, which, in turn, requires
an expensive optical inspection step.

      The new method of making seeding eliminates the requirement of
locating the gap and being able to seed the circuit open without
locating it.

      The scientific foundation of this method is the difference of
optical reflectivity as well as thermal conductivity of the
conducting line and the substrate.  It is well known that copper
reflects most of the visible light and is one of the best heat
conductors.  On the other hand, the dielectric substrate, for
example, polyimide, absorbs much of the light and conducts heat much
slower than copper. When a laser light hits a copper line, only a
small fraction of energy is absorbed, which is then dissipated
quickly through heat conduction in the copper line.  Therefore, the
heating effect is small.  On the other hand, when a laser light hits
the substrate, most of the energy is absorbed. Because of the poor
heat conduction, the temperature of the spot becomes very high.  If
there is an organometallic film on the entire substrate (for example,
palladium...