Browse Prior Art Database

Laser Soldering of a Tube for Ease of Engineering Changes on Circuit Boards

IP.com Disclosure Number: IPCOM000103351D
Original Publication Date: 1990-Oct-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 1 page(s) / 37K

Publishing Venue

IBM

Related People

Johnson, RA: AUTHOR [+4]

Abstract

Disclosed is a design embodying a tool and a process for making engineering changes and repairing pins in solder filled, plated through holes (PTHs) in circuit boards, without disturbing the device to which the pins are attached.

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Laser Soldering of a Tube for Ease of Engineering Changes on Circuit Boards

      Disclosed is a design embodying a tool and a process for making
engineering changes and repairing pins in solder filled, plated
through holes (PTHs) in circuit boards, without disturbing the device
to which the pins are attached.

      The disclosed design utilizes a tube having an inner
solderable, optically reflective and electrically conductive layer
surrounded by an electrically insulating layer.  One example of such
a tube is a copper tube clad on the outside with a layer of aluminum
that is anodized to provide an outer insulating layer of aluminum
oxide.

      The PTH being reworked is drilled out from the board's backside
(the side opposite the device entry) to a predetermined depth
sufficient to ensure a break in electrical continuity between the PTH
and a predetermined board signal plane.  The drilling debris in the
hole is removed and the tube, with a tiny self-fluxed solder preform
perched on its tip, is inserted into the blind hole.  When the tube
end presses the solder preform against the hole bottom, a laser is
directed into the tube to reflow the solder.  Epoxy is then applied
between the tube and the board where the tube exits the board to
provide strain relief.  The tube end sticking out of the hole is now
ready for conventional back-board wiring.

      Disclosed anonymously.