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Method of Removing Discretionary Interconnections and Producing an Electric Circuit Open by Electric-Arc of unwanted Metallization

IP.com Disclosure Number: IPCOM000113303D
Original Publication Date: 1994-Aug-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 2 page(s) / 82K

Publishing Venue

IBM

Related People

Decain, DM: AUTHOR [+3]

Abstract

For high performance computer application, it is common to mount the integrated circuits on a multilayer substrate package. This allows the signal lines between chips to be mounted in a manner which optimizes the performance of the computer. The multilayer package can be made of a number of different types of materials which may include various types of ceramics. Depending on the size of the packaging substrate, the number of integrated circuits mounted may vary from just a few to a few hundreds.

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Method of Removing Discretionary Interconnections and Producing an
Electric Circuit Open by Electric-Arc of unwanted Metallization

      For high performance computer application, it is common to
mount the integrated circuits on a multilayer substrate package.
This allows the signal lines between chips to be mounted in a manner
which optimizes the performance of the computer.  The multilayer
package can be made of a number of different types of materials which
may include various types of ceramics.  Depending on the size of the
packaging substrate, the number of integrated circuits mounted may
vary from just a few to a few hundreds.

      Due to the complexity of the multilayer packages, it is often
difficult to manufacture a complete packaging substrate with
electrical connections that are entirely perfect.  Because of this
fact and because engineering changes may be required at final
assembly, the top layer of the substrate package is often built with
extra "discretionary" connections so that defects can be bypassed,
and/or engineering changes made during final testing and assembly.
Defect correction and engineering changes on the packaging network
require creating an electric-circuit open at specified locations on
the surface electrical line network.

      One technique that is commonly used for this purpose is to use
a laser to vaporize away a portion of a metal line to create the
desired condition of a circuit open.  However, in order for this
method to be successful, it is necessary to impose limits on the
width and thickness of the "discretionary" links.  This requirement
is often necessary to prevent damage to an underlying thin film
structure by excessive laser heating.  Electrical lines that are
periodically and systematically reduc...