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Hardening of an X-Ray Beam by a Tungsten Filter to Improve the Contrast in a Laminographic X-Ray Image of Solder-Ball Connect Joints

IP.com Disclosure Number: IPCOM000104519D
Original Publication Date: 1993-Apr-01
Included in the Prior Art Database: 2005-Mar-19
Document File: 1 page(s) / 34K

Publishing Venue

IBM

Related People

Rooks, SM: AUTHOR

Abstract

The contrast within a laminographic X-ray image of the eutectic-solder fillet of a Solder-Ball Connect (SBC) joint is significantly increased by the use of a tungsten sheet, which hardens or filters the X-ray beam, improving the accuracy of the analysis of the solder fillet.

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Hardening of an X-Ray Beam by a Tungsten Filter to Improve the Contrast in a Laminographic X-Ray Image of Solder-Ball Connect Joints

      The contrast within a laminographic X-ray image of the
eutectic-solder fillet of a Solder-Ball Connect (SBC) joint is
significantly increased by the use of a tungsten sheet, which hardens
or filters the X-ray beam, improving the accuracy of the analysis of
the solder fillet.

      The signal of the eutectic-solder fillet of a Solder-Ball
Connect joint within a laminographic X-ray image is greatly reduced
due to the presence of the high-lead-content solder-ball.  Before the
X-ray beam can pass through the eutectic fillet, it must first pass
through the solder-ball.  Low-energy photons of the X-ray beam are
scattered by the dense solder-ball, which reduces the contrast within
the resultant X-ray image, making it difficult to distinguish
eutectic fillets with low volume from those with sufficient volume.

      If a tungsten sheet is placed in the path of the X-ray beam,
the tungsten will filter out the low-energy photons, thereby
increasing the mean energy of the X-ray beam and making it more
penetrating.  Increasing the mean energy of the X-ray beam reduces
the scatter of the low-energy photons and, therefore, increases the
overall contrast of the image.  Using the tungsten sheet when
inspecting SBC joints with an X-ray laminography system significantly
increases the signal of the eutectic-solder fillet relative to the
si...