Bridge, David Richard (1986) Aspects of electronic device packaging. PhD thesis, University of Warwick.

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Abstract

For this work cordierite has been investigated as a
possible substitute substrate material for alumina, with
particular emphasis on its role in multilayer device packaging.
By limiting the processing temperatures to below 1000oC, copper
could be used as the conductor material. Milled glass powder was
made into thin sheet form by a doctor blading technique and, once
dried, the copper screen printed on top. After lamination and
firing, the conductor was completely encapsulated by the cordierite
matrix. Copper diffusion occ~red with metallic copper precipitating
out although a small denuded zone was evident around the periphery
of the conductor. This was due to compositional changes occurring
there.
Experiment showed that the effects of glass particle shape,
average size and size distribution lead to deviation in the
shrinking of compacts from the theoretical sintering curves. An
unstable ~ phase was the first to appear on the glass particle
surfaces although another, unidentifiable phase, was also found to
exist during the very early stages of crystallization. This was
followed shortly after by bulk crystallization of ~ cordierite
in the remaining glass, possibly being aided by a prior phase
separation. Further heat treatment lead to the transformation
to a cordie rite and the formation of enstatite, the exact
transformation temperature depending upon the minor oxide additives
in the glass. At temperatures above ~10500C protoenstatite formed
and lead to a general degradation in material properties.
The benefit from having a cordie rite as the principal phase
is a low dielectric constant (5.35) and loss angle (5 x 10-4),
reasonable strength (130 MPa) and high resistivity (~1015 Qcm).
This makes it a suitable replacement for alumina although its low
thermal conductivity (~2 Wm-lK-l) is a drawback. By adjusting the
MgO/A1203 ratio, the material could be expansion matched to that
of silicon.

Item Type:	Thesis (PhD)
Subjects:	Q Science > QC Physics T Technology > TK Electrical engineering. Electronics Nuclear engineering
Library of Congress Subject Headings (LCSH):	Electronic packaging -- Research, Cordierite, Phase transformations (Statistical physics), Glass -- Thermal properties
Official Date:	December 1986
Institution:	University of Warwick
Theses Department:	Department of Physics
Thesis Type:	PhD
Publication Status:	Unpublished
Supervisor(s)/Advisor:	McMillan, P. (Peter); Holland, Diane
Sponsors:	Science and Engineering Research Council (Great Britain) (SERC)
Extent:	[14], 196 leaves.
Language:	eng

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