Packaging
is rapidly becoming an area of microelectronics technology, which can
limit the operating speed on an integrated circuit. To address this
concern, much research and development attention now focuses on
packaging in an effort to prevent it from impeding the speed of
electronic system.
Electronic packaging is defined as the electronic discipline of
designing a protective enclosure for an electronic circuit so that it
will both survive and perform under all environmental conditions. In the
past, the term “electronic packaging” referred to a small
number of formats for encasing electronic components, including
integrated circuits, so they could readily and reliably be installed in
electronic end-products. The principal packaging types was through hole,
surface mount, tape automated bonding, and single-chip.
Production of high quality, low-cost consumer electronics product is
dependent on proficiency in electronic packaging technologies.
Continuous improvement of packaging and related technologies has
provided the impetus for development of new and improved consumer
product; likewise, consumer demand for new and improved electronic
products at reasonable prices has provided the impetus for development
of increasingly sophisticated electronic packaging. Packaging is
important for signal and power transmission, heat dissipation,
electromagnetic interference shielding and protection from environmental
factors such as moisture, contamination, hostile chemicals and
radiation.
Levels of Packaging
Typical electronic package consists of a hierarchy of interconnections
that can be divided up into levels ranging from 0 to 6. The first level
package is the most important of all levels because it contains only a
single die. The first level package consists of lead frame, die, die
attach, wire bond, and encapsulant. The lead frame includes both the
lead paddle and lead finger. The lead paddle is used to mechanically
support the die before encapsulation while the lead finger allows for
electrical contact between the package and circuit board. The die attach
material permits heat conduction while assuring mechanical stability of
the die. The encapsulant is either a polymer or ceramic, depending on
cost and the environment in which the package is used.
The package family selected for an electronic application is dependent
on the chip power, size and weight requirements of the system,
electrical performance, and lead count requirements.
| Package Family |
Characteristics |
Package Type |
| In- Line |
Leads on one or two sides of package |
SID, PDIP, CERDIP |
| Small Outline |
Leads on two or four sides, small body |
SOJ, SOP, TSOP |
| Quad Surface Mount |
Leads on four sides package
Larger package dimension
High lead counts |
PLCC, PQFP, LDCC, CERQUAD |
| Grid Array |
Pin or ball array placed on package body
Very high lead count |
PPGA, PLGA, PBGA |
System Type
Three principal system types have been identified, each of which
appears to make different demands on packaging: low-end digital,
high-end digital, and high speed.
Low-end digital
systems typically use silicon MOS circuits packaged separately, with
printed wiring boards for chip interconnection.
High-end
digital systems typically use silicon bipolar technology, often with
packages in modules that carry many chips. The advent of bipolar
complementary technology blurs the distinction between the two digital
system types.
High-speed circuits typically use
gallium arsenide chips.
Packaging Approaches
The two main approaches currently used to achieve high-density
electronic packaging are the
printed wiring board (PWB)
approach and the
thick-film multichip module (MCB)
approach. In the PWB approach, single chip modules, the first packaging
level, are assembled on a printed wiring board. The second packaging
level is the individual packages by either through hole or surface
mounting using soft solder joints. In the thick film MCM approach,
multichip modules contain multiple bare chips jointly packaged in a
ceramic package that is constructed by multilayering thick film
conductor layers and ceramic dielectric layers.
Applications
The electronic packaging is commonly defined as “all parts of an
electronic system with the exception of the integrated devices”.
The electronic system itself may be a personal computer, laptop, server
or a workstation. Systems also include many consumer electronics,
appliances, automobiles, weapon systems, airplanes, medical diagnostic
and surgical instruments and bio-medical devices. Typical hardware that
would be considered a part of the electronic package includes printed
circuit boards, chip carriers, connectors, cables, power supplies, fans
and blowers and the system box or chassis among many others. The
packaging not only includes the hardware and software used in the
electronic system but also includes the manufacturing and assembly
processes for the components and the system.
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