Title
Bottom terminated component (BTC) technology follows growing market demand for lower profile packaging
Joe Fjelstad
Bottom terminated component (BTC)
technology follows growing market
demand for lower profile packaging
IC packaging is an area of technology that
seems to offer an endless stream of innova-
“Instead of using copper lead frames, which
tion for the electronic product or system
designer. One area of increasing interest in
would be a difficult fit for such applications,
recent years is the family of bottom-leaded
components whose representatives include
the increasingly common quad flat no-lead
Mirror Semiconductor is using 200 µm
(QFN) devices and land grid arrays (LGA).
These devices are especially attractive for
(8 mil) thick rigid substrates.”
cost and performance reasons, and for the
low profile they offer in an electronic as-
guidance going forward. The document for the semiconductor market, and they
sembly, but they also represent a significant
IPC-7093, titled “Design and Assembly are finding demand from a number of
challenge to the assembly process due to
Process Implementation for Bottom Termi- different areas.
their lack of stand-off height. Presently, the
nation SMT Components,” is in working While the structures in finished
IPC is in the process of developing a stan-
draft form and is expected to be out for form appear to be QFN type, they are
dard to address these issues and provide
review later this year or early next. actually different in their construction,
Relative to the referenced innovations which makes them stand apart from
in the BTC packaging arena, a package their “siblings.” That is, instead of using
offering that is getting increased attention copper lead frames, which would be a
in recent months is being developed and difficult fit for such applications, Mirror
marketed by Mirror Semiconductor in Semiconductor is using 200 µm (8 mil)
Irvine, CA (www.mirrorsemi.com). The thick rigid substrates. Both Mitsubishi BT
company has been developing a family and Rogers RO4003C substrates are being
of open cavity QFN packages used at present for standard and high
frequency applications, and the company
indicates that other substrate materials
will be considered in the future. The open
cavity QFN (see Figure 1) is a wire bonded
structure and to assure that good wire
bonding is achieved, the cavity side of the
substrate is plated with ~1.25 µm (~50
microinches) of wire-bondable gold.
Presently the cavity is formed by
dispensing in a process similar to that
used for chip-on-board applications in the
creation of dams for encapsulant. This is
 
very simple and easily modified as there
are no physical parts to assemble or tooling
Figure 1. Bottom terminal components such as QFNs and LGAs are among the most rapidly growing package
required, but it does have some limitations
types in terms of use. Above are shown opposing side views of an air cavity bottom terminated package concept
being produced and offered by Mirror Semiconductor in Irvine, CA .
when it comes to use of a lid because the
rim of the cavity is rounded rather than
4 – Global SMT & Packaging – October 2009 www.globalsmt.net
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