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Method of Producing Low Alpha-Emitting Encapsulant Using Sol-Gel- Derived Glass Fillers

IP.com Disclosure Number: IPCOM000120067D
Original Publication Date: 1991-Mar-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 2 page(s) / 69K

Publishing Venue

IBM

Related People

Mukherjee, SP: AUTHOR [+3]

Abstract

Disclosed is a method of making low alpha epoxy encapsulant material using high purity glass fillers derived from sol-gel technology. The use of glass-filled low thermal expansion epoxy encapsulant at the solder or C4 (controlled collapse chip connection) bonded flip-chip assemblies on substrates (e.g., ceramics or organics) are reported to yield dramatic improvement to the C4 fatigue life by a factor of 5 to 10 (1). Besides the C4 fatigue life enhancement, the encapsulant would also provide an alpha protection to the memory devices, if it were available in a low alpha form. The alpha activity is commonly present in most of the packaging materials (e.g., solder and ceramics) due to the presence of traceable radioactive elements (e.g., uranium and thorium).

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Method of Producing Low Alpha-Emitting Encapsulant Using Sol-Gel-
Derived Glass Fillers

      Disclosed is a method of making low alpha epoxy
encapsulant material using high purity glass fillers derived from
sol-gel technology.  The use of glass-filled low thermal expansion
epoxy encapsulant at the solder or C4 (controlled collapse chip
connection) bonded flip-chip assemblies on substrates (e.g., ceramics
or organics) are reported to yield dramatic improvement to the C4
fatigue life by a factor of 5 to 10 (1).  Besides the C4 fatigue life
enhancement, the encapsulant would also provide an alpha protection
to the memory devices, if it were available in a low alpha form.  The
alpha activity is commonly present in most of the packaging materials
(e.g., solder and ceramics) due to the presence of traceable
radioactive elements (e.g., uranium and thorium).  One of the
problems with the commercially available epoxy encapsulants is that
they are high alpha emitters.  The alpha activity in the encapsulants
is particularly attributed to the filler, since it is derived from
natural resources or produced by a non-synthetic route (1).

      This article describes a new filler system produced by a
synthetic route using sol-gel chemistry.  This process uses
polymerization of alkoxysilane solutions in aqueous media using
suitable catalysts to form viscoelastic gels that are sintered to
yield glass.  The residual organics and water from the sol-gel
powders are removed by firing in oxidizing atmosphere at 800oC
depending on the compositions. The powders are prepared directly fr...