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The compound used to form the alpha particle barrier can be varied to tailor-stiffness, and is cleanable to facilitate a rework of the module.
English (United States)
This text was extracted from a PDF file.
This is the abbreviated version, containing approximately
90% of the total text.
Page 1 of 1
Alpha Particle Barrier for Flip Chip Bonded Semiconductor Devices
The compound used to form the alpha particle barrier can be varied to tailor-
stiffness, and is cleanable to facilitate a rework of the module.
In the packaging of silicon chips wherein the chips are mounted on a ceramic
substrate, it is important to insure a good bond between the ceramic and the
chip. Also, as the circuitry on the chip becomes smaller and more closely
packed, it is necessary to insure maximum shielding of the chip from alpha
particle radiation. These alpha particles can cause false signals and
computational errors upon striking the chip. This is particularly pertinent in
charge-coupled devices for memory products. Sources of alpha particle radiation
are the ceramic material of the substrate supporting the chip and the solder
material forming the terminal bond. In forming the barrier it is necessary to
insure that any bonding material be essentially free of alpha particle emitters as
well as being a good shield against alpha particles emitted by the substrate and
This composition which can be used to form a barrier consists of (1) zero to
50 weight percent of a microcrystalline wax, (2) zero to 50 weight percent of
ultra-pure sulphur-free mineral oil, and (3) one per cent of a dye.
The compound is placed under the bonded chips while the substrate and
material are both warmed above the melting point of the wax. The placement of
the barrier is aided by capillary action in...