Browse Prior Art Database

Precision Superposition Component Placement Tool for End Point Sensing

IP.com Disclosure Number: IPCOM000107687D
Original Publication Date: 1992-Mar-01
Included in the Prior Art Database: 2005-Mar-22
Document File: 3 page(s) / 90K

Publishing Venue

IBM

Related People

Beers, GE: AUTHOR [+2]

Abstract

Disclosed is an optical device that allows precision placement of high lead density quad flat pack (QFP) integrated circuit components on printed circuit boards. The optical nature of the device allows for image superposition of two images so that a computer camera can match leads with pads. The novel optical device used is a special beam splitter in conjunction with polarizers and analyzers.

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This is the abbreviated version, containing approximately 52% of the total text.

Precision Superposition Component Placement Tool for End Point Sensing

       Disclosed is an optical device that allows precision
placement of high lead density quad flat pack (QFP) integrated
circuit components on printed circuit boards. The optical nature of
the device allows for image superposition of two images so that a
computer camera can match leads with pads.  The novel optical device
used is a special beam splitter in conjunction with polarizers and
analyzers.

      This system provides simultaneous computer inspection of all
leads on the QFP and the component site, as well as operator visual
placement.  Most placement systems require two or more cameras for
inspection.  They are used for coordinate correction between the
component and printed circuit board (PCB) prior to placement, as well
as movement of the robot arm in x,y,z and theta during actual
placement. This technique requires only movement in the z plane.
This minimizes errors induced by the robot in x,y and theta.  An
additional benefit is that the number of required cameras is also
reduced from the typical three to one.

      A functional description of the invention is contained in the
following six sections:  Please refer to the figure for the following
description.
      1)  The robot arm with the QFP is positioned over the component
site on the printed circuit board.  The printed circuit board is
positioned by an x-y table.
      2)  The optical beam splitter is positioned by an air-operated
shuttle mechanism to a predetermined point between the QFP component
and the PCB.
      3)  The lin...