1996 Electronics Industry Environmental Roadmap - Civil and ...

Emerging Technologies
Therefore, given larger wafers, the increased number of masks, greater number of metallization
layers, and an overall growth projection for the IC manufacturing industry, environmental issues
are unlikely to abate. Current environmental priorities include the identification of
environmentally benign solvents, cleaners, and photoresists, and improved processes for
recycling, recapture, regeneration, and reuse of process chemicals and solvents. Test wafers and
wafer reworks are a significant contributor to environmental waste and should be reduced.
Increased attention to dry and additive processes, for the environmental benefit as well as the
apparent benefits in decreasing contaminants, is also a priority. Overall reduction in energy
consumed per manufactured unit will also become a likely IC industry objective for economic
and environmental purposes.
6.2.2 Packaging
When wafer processing is complete, the individual ICs (“die”) are cut apart to be packaged and
assembled. They may be passed along to be encapsulated in a protective coating or housing
(“packaging”) or be processed as “bare die” for direct attachment to a substrate. Packaging
performs two important functions for ICs: electrical connection and protection of the
semiconductor device.
Most semiconductor packages have the same basic parts and are assembled using the same
general set of process steps. In most families of packaging technologies, a lead frame connects
the chip to the printed wiring board. The lead frame is connected to the chip using a very thin
wire welded to both the chip and the lead frame. There is also a material enclosing the chip,
wire, and part of the lead frame, which must protect the chip from the external environment.
During the process of assembly, the chip is attached to the lead frame, the wire is bonded to the
chip and then to the lead frame, and the whole structure, except for a small part of the lead frame,
is permanently encapsulated for protection.
There are a wide variety of packaging approaches, but generally speaking, the IC is encapsulated
either in a hermetically sealed ceramic or metal package or in non-hermetically-sealed packages,
usually made of plastic. Hermetically sealed packaging is particularly well-suited where high
performance and high reliability are key drivers and non-hermetically sealed packaging where
cost is a key driver. However, recent technological advancements have resulted in nonhermetically
sealed packaging options with performance and reliability nearly equivalent to
hermetics.
Increasingly powerful ICs will also require new technologies for packaging, interconnect, and assembly.
The trends in electronic packaging are toward higher I/O counts, lower operating voltages,
and faster switching speeds. Among the emerging technologies currently affecting packaging
is a shift from peripheral interconnection to area array connections, from two-dimensional to
three-dimensional packaging, and from single- to multi-chip packaging [32]. The driving force
in the evolution of packaging technology is the need to minimize the package size in order to
maximize the amount of active silicon attached to the circuit board or other substrate. As a
consequence, packaging approaches such as chip-scale packaging and ball grid arrays (BGAs) are
receiving substantial attention in the industry.
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