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Spray Nozzle Configuration for Maximizing Develop/Etch Rate and Uniformity

IP.com Disclosure Number: IPCOM000115341D
Original Publication Date: 1995-Apr-01
Included in the Prior Art Database: 2005-Mar-30
Document File: 4 page(s) / 99K

Publishing Venue

IBM

Related People

Baldovin, TJ: AUTHOR [+4]

Abstract

Disclosed is a system to improve the uniformity of copper etching (or photoresist developing) with spray chamber processing. When a circuit board is processed horizontally through a spray chamber, a puddle of the sprayed solution will form on the up side of the board. The etch rate (or develop rate) underneath that puddle will be less than on other areas of the board resulting in non-uniform etching (developing) across the top surface of the board. This invention eliminates the formation of the puddle and increases the etch (develop) rate at the same time.

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Spray Nozzle Configuration for Maximizing Develop/Etch Rate and Uniformity

      Disclosed is a system to improve the uniformity of copper
etching (or photoresist developing) with spray chamber processing.
When a circuit board is processed horizontally through a spray
chamber, a puddle of the sprayed solution will form on the up side of
the board.  The etch rate (or develop rate) underneath that puddle
will be less than on other areas of the board resulting in
non-uniform etching (developing) across the top surface of the board.
This invention eliminates the formation of the puddle and increases
the etch (develop) rate at the same time.

      Typically, photoresist developing or copper etching of a
printed circuit board is accomplished by spraying the developing
medium or etchant onto the board surfaces; the spray is produced by
pumping the fluid through spray nozzles configured so that the spray
impingement pattern covers the board surface in the direction of
travel.  The board is transported by conveyor underneath the spray
nozzles.

      One of the inherent problems with this method is the puddle of
fluid that forms in the center of the top surface of the board.
Develop/etch rates are a function of the fluid velocity at the board
surface and the concentration of dissolved species local to the area
of dissolution.  The puddle causes a decrease in the fluid velocity
and a build-up of the dissolved species, both causing a decrease in
the dissolution rate underneath the puddle; this in turn causes
uneven dissolution across the board surface.

      This invention eliminates the formation of the puddle.  The
spray nozzle used has a elliptical spray impingement pattern with a
spray angle from 25 to 60 degrees (Fig. 1).  The key concept used to
eliminate the puddle is the positioning of the spray nozzle; the
spray nozzles are set at a compound angle so that a flow channel is
f...