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Techniques for Measuring the Tilt Angle of Flip-Chips Surface-Mounted Technology Components

IP.com Disclosure Number: IPCOM000104520D
Original Publication Date: 1993-Apr-01
Included in the Prior Art Database: 2005-Mar-19
Document File: 1 page(s) / 40K

Publishing Venue

IBM

Related People

Rooks, SM: AUTHOR

Abstract

The angle of tilt of a chip or a component greatly affects the long-term relaibility of its solder joints, but it is very difficult to inspect automatically. Two possible techniques, using either X-ray imaging or laser triangulation, should provide the solution.

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Techniques for Measuring the Tilt Angle of Flip-Chips Surface-Mounted Technology Components

      The angle of tilt of a chip or a component greatly affects the
long-term relaibility of its solder joints, but it is very difficult
to inspect automatically.  Two possible techniques, using either
X-ray imaging or laser triangulation, should provide the solution.

      For fine-pitch surface-mount devices, like flip-chips or thin,
small-outline packages (TSOPs), the tilt angle of the device relative
to the printed-circuit board (PCB) surface greatly affects the
long-term reliability of its solder joints.  Tilting intensifies any
stresses or strains induced due to the Coefficient of
Thermal-Expansion mismatch between the device and the PCB during
power (on/off) cycling.  However, tilting is very difficult to
measure, especially visually.

      Two possible automated techniques are available to measure
tilting:  X-ray imaging and laser triangulation.  The thickness of
solder under each lead or bump of the device can be directly measured
by an X-ray system, either laminography or tomosynthesis, if another
device is positioned on the opposite side of the PCB, or
transmission, if nothing is positioned on the opposite side of the
PCB.  The gray-scale intensity in the resultant image is proportional
to the thickness of solder in the X-ray beam path.  The tilt angle of
the device can be calculated by measuring the solder thickness at the
four corner-joints.

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