Page 72 - Building A Succesful Board-Test Strategy

58 BUILDING A SUCCESSFUL BOARD-TEST STRATEGY

the pace of product change continues to accelerate. Meanwhile, competition con-
tinues to heat up and the time-to-market factor becomes ever more critical. A test
that might have sufficed for earlier product generations might now be too expen-
sive or delay product introduction intolerably.
The evolution of test has provided a plethora of methods, but none repre-
sents a panacea. Thoroughly understanding each approach, including advantages
and disadvantages, permits test managers to combine tactics to construct the best
strategy for each situation.

2.3 Test Options

There are two basic approaches to ensuring a high-quality electronic product.
First, a manufacturer can design and build products correctly the first time, mon-
itoring processes at every step. This technique, popular with managers because it
saves both time and money, includes design verification, extensive process and
product simulation, and statistical process control. The alternative is to build the
product, test it, and repair it. As Figure 2-2 shows, test-and-repair is more cost-
effective for simpler products, but its cost increases with product complexity faster
than testing the process does. At some point, process testing becomes less expen-
sive. The exact crossover point varies from product to product and from manu-
facturer to manufacturer.
Most companies today follow a strategy that falls somewhere between the
two extremes. Relying heavily on product test does not preclude being aware of
process problems, such as bad solder joints or vendor parts. Similarly, products
from even the most strictly controlled process require some testing to ensure that

Testing Processes vs. Testing Products

Product Complexity
Figure 2-2 Test-and-repair is cost-effective for simple products, but its cost increases
with product complexity faster than testing the process does.