growing demand for semiconductor packages like BGA's, CSP's, and SIP's
has led to an equally strong demand for substrates and interposers that
these packages employ.
that provide the package with mechanical base support and a
form of electrical interface that would allow the external world to
access the device housed within the package. An
intermediate layer often used for interconnection routing or as a
ground/power plane. Sometimes the terms 'substrate' and 'interposer' are
used to refer to the same thing.
are several types of package substrates, but the two major categories
substrates. As their names imply, these two categories differ with
respect to their mechanical properties. Rigid substrates have a
fixed shape and form, while tape substrates are thin and flexible. Early
rigid substrates were mostly made of ceramic, but today organic
substrates have become more widely deployed among various packages.
that are composed of a stack of thin layers or
are called 'laminate' substrates. There are several different materials
used for manufacturing laminate substrates. Two widely used materials
for laminate substrates are
a traditional epoxy-based laminate,
and the more advanced and higher-performing resin-based
from Mitsubishi Gas and Chemical.
has become the preferred laminate material for many manufacturers
of its high Tg, low dielectric constant and good insulation properties.
In fact, BT is now apparently the standard substrate material for BGA's,
and is also
being used in CSP laminates. New
laminate substrates emerging in the market, such as those introduced by
Hitachi Chemical, Nelco International, and Sumitomo Bakelite are
composed of advanced epoxies or epoxy blends. These are expected
to give BT laminates some good competition that may lead to more
reductions in substrate prices.
of high-strength and high-temperature polymer material such as
One major advantage of tape substrates
is quite obvious: it is compliant enough to be subjected to motion while
carrying the circuits built onto them, which is useful in 'moving'
applications such as disk drives and printers. Tape substrates are
also light-weight, less costly, and better than laminate substrates in achieving fine-line and microvia
features, a fact that CSP's took advantage of in pursuit of fine-pitched
wiring. The disadvantages of tape substrates include: 1) more difficult
handling during processing; 2) warpage issues; and 3) large differences
in CTE with other materials such solder masks.
from serving as a base for IC packages, substrates are also used to
the chip's I/O system to the application board's interconnection
features. Thus, substrates must somehow have within themselves
metal conductors that can accomplish this routing function. These are
usually in the form of traces etched from
foil that's bonded to one or more laminates of the substrate. The
copper layers of the substrate are commonly finished with a layer of
over a layer of electroless
The nickel prevents copper-solder interdiffusion while the gold inhibits
oxidation and enhances solderability.
laminate substrate may have several layers with metal planes or traces
that are interconnected to each other by through-hole plated
in much the same way as conventional PCB's. BT substrates often have an
even number of routing layers. In a 4-layer substrate, for instance, the
I/O routing planes are the ones at the top and bottom of the substrate,
while the inner layers are used as a ground and power plane.
include: ASE Material
Inc.; CMK Corporation (Nippon CMK); Compeq Manufacturing
Co., Ltd.; D. T. Circuit Technology Co., Ltd.; Eastern Co., Ltd.; Hitachi
Chemical Co., Ltd.; Japan Circuit Industrial Co., Ltd.; Kyocera
Corporation; Matsushita Electronic Components Co., Ltd.; Mitsubishi
Electric Corporation; NEC Toppan Circuit Solutions Inc.; NGK Spark Plug
Co., Ltd. (NTK); Phoenix Precision Technology Corporation; Shinko
Electric Industries Co., Ltd.; and WUS Printed Circuit Co., Ltd.
Compass Technology Co. Ltd.; Hitachi Cable, Ltd.; Mitsui Mining and
Smelting Co., Ltd.; NEC Toppan Circuit Solutions Inc.; Shindo Company,
Ltd.; Shinko Electric Industries Co., Ltd.; Sumitomo Metal Mining Co.,
Ltd; and WUS Printed Circuit Co., Ltd.
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