Chapter 22 Materials Selection and Design Considerations

W134 • Chapter 22 / Materials Selection and Design Considerations
for this steel alloy, and that ty � 0.6sy. Note: heat treatment of the 4340 steel is
discussed in Section 10.8.
Materials for Integrated Circuit Packages
22.D11 You have been asked to select a metal alloy
to be used as leadframe plate in an integrated
circuit package that is to house a
silicon chip.
(a) Using the database in Appendix B list
those materials that are electrically conductive
have linear
coefficients of thermal expansion of
between and 10 � 10
and thermal conductivities of greater than
100 W/m-K. On the bases of properties and
cost, would you consider any of these
materials in preference to those listed in
Table 22.6? Why or why not?
�6 (�C) �1 2 � 10 ,
�6
[s 7 10 � 106 (�-m) �1 ]
(b) Repeat this procedure for potential insulating
leadframe plate materials that
must have electrical conductivities less
than as well as coefficients
of thermal expansion between 2 � 10�6 10�10 (�-m) �1 ,
and 10 � 10 and thermal con-
�6 (�C) �1 ,
ductivities of greater than 30 W/m-K. On
the bases of properties and cost (Appendix
C), would you consider any of the materials
listed in Appendix B in preference
to aluminum oxide? Why or why not?
Design Questions
22.D12 Perform a case study on material usage
for the compact disc, after the manner of
those studies described in this chapter.
Begin with a brief description of the
mechanism by which sounds are stored
and then reproduced. Then, cite all of the
requisite material properties for this application;
finally, note which material is
most commonly utilized, and the rationale
for its use.
22.D13 One of the critical components of our
modern video cassette recorders (VCRs)
is the magnetic recording/playback head.
Write an essay in which you address the
following issues: (1) the mechanism by
which the head records and plays back
video/audio signals; (2) the requisite properties
for the material from which the head
is manufactured; then (3) present at least
three likely candidate materials, and the
property values for each that make it a
viable candidate.
22.D14 The transdermal patch has recently become
popular as a mechanism for delivering
drugs into the human body.
(a) Cite at least one advantage of this
drug-delivery system over oral administration
using pills and caplets.
(b) Note the limitations on drugs that are
administered by transdermal patches.
(c) Make a list of the characteristics required
of materials (other than the delivery
drug) that are incorporated in the
transdermal patch.