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What Is a Test Strategy? 17

that products designated for sale in one country do not interfere with broadcast
and cellular-phone frequencies in another. Products must undergo strict compli-
ance testing and receive compliance engineering (CE) certification before they can
be sold in the target country.
Other trends that will complicate test-strategy decisions include a tendency
to pack ever more components onto a particular sized board, or (conversely)
to shrink board size without comparably reducing component count. In either
case, the resulting layouts offer much less space for test points and nodes for
bed-of-nails probing than before. Where companies are integrating more func-
tions onto ASICs and other complex devices, real estate is not an issue, and the
lower parts count reduces the complexity of board-level tests. At the same time,
however, this development pushes more test responsibility back to the device level,
burdening device designers and manufacturers with the need to ensure that only
good devices reach customers' hands. As in the past, manufacturers should not
assemble boards from other than known-good components. That rule brings its
own challenges.
In addition, the classic design-for-testability guideline that attempts to
mandate components on only one board side is often impractical. Complex hand-
held products such as cellular phones must not exceed a certain size. Designers
must therefore often get somewhat creative to cram sufficient functionality into the
small permissible space.
Not all products suffer from ever-shrinking footprint and declining nodal
access, however. As Figure 1 -4 shows, telephone company switches, aerospace elec-
tronics, and other products continue to enjoy through-hole access. At the other end
of the spectrum, wireless cell-phone handsets, many notebook PCs, and personal
digital assistants (PDAs—so-called "hand-held PCs") increasingly defy conven-
tional access, and consequently confound traditional test methods.

1.5 Concurrent Engineering is Not Going Away

An old industry adage states that there is never enough time to do a job right
but always enough time to do it again. In its purest form, concurrent engineering
is an attempt to put paid to that attitude by setting forth a set of principles that
maximize the likelihood that a job will be done right the first time. Sammy Shina,
in his Concurrent Engineering and Design for Manufacture of Electronic Compo-
nents (1991), defines the term as: "Integrating a company's knowledge, resources,
and experience into development, manufacturing, marketing, and sales activities
as early in the cycle as possible."
Companies that have adopted this philosophy have reaped substantial bene-
fits. In the early 1990s, for example, AT&T managed to reduce its development time
for new telephone products from two years to one. Hewlett-Packard printers that
once took 4 1/2 years from drawing board to production now get there in less than
half that time.
In many cases, the time from customer order to product shipment has fallen
even more dramatically. Concurrent engineering helped Motorola pagers to get out