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Agitation System for Small Diameter Plated-Through Holes

IP.com Disclosure Number: IPCOM000099900D
Original Publication Date: 1990-Feb-01
Included in the Prior Art Database: 2005-Mar-15
Document File: 2 page(s) / 72K

Publishing Venue

IBM

Related People

McHatton, RC: AUTHOR [+3]

Abstract

In an electroless copper-plating process, solution movement through drilled holes is important to insure the proper thickness and distribution of metal deposition. Generally, printed circuit boards are agitated in the horizontal plane (and sometimes additionally in the vertical plane) to accomplish the required solution movement. Decreasing the plated-through hole (PTH) diameter or increasing the ratio of board thickness to PTH diameter raises the probability that solution will not move through the holes.

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Agitation System for Small Diameter Plated-Through Holes

       In an electroless copper-plating process, solution
movement through drilled holes is important to insure the proper
thickness and distribution of metal deposition.  Generally, printed
circuit boards are agitated in the horizontal plane (and sometimes
additionally in the vertical plane) to accomplish the required
solution movement.  Decreasing the plated-through hole (PTH) diameter
or increasing the ratio of board thickness to PTH diameter raises the
probability that solution will not move through the holes.

      The proposed system would rapidly agitate the boards within the
plating basket.  The system is significantly different from vibration
systems in which the entire basket is rapidly vibrated.  This new
approach to agitation uses an external magnetic source connected to
small electromagnets mounted between the boards.  Agitation is
accomplished by rapidly changing the polarity of these magnets.  In
addition, the whole basket containing the parts is still traversed in
the horizontal plane, but at a reduced speed.

      The agitation method provides a superior means of moving the
plating solution through the PTHs.  As the polarity of the magnets
changes, adjacent panels are forced apart and then back together.  In
a discreet time interval for a polarity change, half the boards
(every other one) will move in one direction, the remainder in the
other direction.  The opposite movements ...