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Method of Producing Vias in First and Second Level Circuit Boards

IP.com Disclosure Number: IPCOM000121192D
Original Publication Date: 1991-Jul-01
Included in the Prior Art Database: 2005-Apr-03
Document File: 1 page(s) / 57K

Publishing Venue

IBM

Related People

Bickford, HR: AUTHOR [+2]

Abstract

Described is a method of producing vias, called laservias, in first and second level circuit boards between layers of conductors separated by an insulating layer. By utilizing laser technology, rugged vias are produced without the need for chemicals, which may contaminate the product.

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This is the abbreviated version, containing approximately 67% of the total text.

Method of Producing Vias in First and Second Level Circuit Boards

      Described is a method of producing vias, called laservias, in
first and second level circuit boards between layers of conductors
separated by an insulating layer.  By utilizing laser technology,
rugged vias are produced without the need for chemicals, which may
contaminate the product.

      Typically, vias for electrical conduction out of a common plane
are made by opening a hole in the insulating support film, depositing
a seed material, and subsequent plating of copper onto the walls of
the opening.  This multi-step process requires careful control of the
chemicals as well as process parameters for plating, such as
temperature, time, etc.  The resulting vias were difficult to inspect
for uniformity since only the destructive process if cross sectioning
of the material would provide data on the success of the operation.
Vias formed in this manner had their weakest point in the region
surrounding the edges of the hole.  This is because it was the most
difficult to provide uniform copper plating thickness at those
points.

      What is proposed is a method used to create laservias between
layers of conductors separated by an insulating layer utilizing laser
energy focussed on the ends of copper beams.  This can cause a
localized reflow of the beam into a ball structure.  A row or rows of
free-standing copper beams are subjected to a focussed laser in the
presence of forming gas.  Th...