Electronics Packaging
by Dennis L. Feucht
Innovatia Laboratories
Electronics packaging is not central to electronic design, but it has a
disproportionate effect on the technology. The overall trend is toward shrinking
volume and this has its relative merits. Several consequences are explored
here, beginning with the engineering design and expanding to the problems
that engineering design is intended to solve.
IC Packages
The driving factor in the reduction of electronics packaging is the reduction of IC packages, both in size and number. Size reduction is, in part, due to shrinking silicon area, allowing the chips to be put into smaller packages. IC shrinkage has several circuit consequences: as transistor and other circuit component dimensions are reduced, parasitic elements are also reduced in value. Smaller junction capacitances and terminal inductances allow transistors to have a higher fT, resulting in higher amplifier bandwidths. Shorter interconnections of components reduce wiring inductance and wire-to-substrate capacitance.
In the 1970s, the leading companies in wideband amplifier design were
mostly the test and measurement (T&M) instrument companies such as Tektronix
and Hewlett-Packard. Tek led H-P in oscilloscope bandwidth with the introduction
of a vertical plug-in accompanying the new 7904 mainframe. Combined, the
vertical system achieved a 500-MHz bandwidth -- quite a feat at the time.
Tek's vice-president of engineering, Bill Walker, had pushed for Tek to
set up an in-house IC fab facility which, by this time, was an obviously
good idea. (Walker later became president of Tek.) Tek had the fastest commercial
transistors on the planet, with an fT of 7 GHz.
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