Page 19 - Building A Succesful Board-Test Strategy

6 BUILDING A SUCCESSFUL BOARD-TEST STRATEGY

suggest a better one. Which brings us to the following definition: A successful test
strategy represents the optimum blend of test methods and manufacturing
processes to produce the best-quality boards and systems in sufficient number at
the lowest possible cost.
Selling-price erosion among electronic products and electronic components
of larger products exerts ever-increasing pressure on manufacturing and test
operations to keep costs down. As they have for more than two decades, personal
computers (PCs) provide an excellent case in point. The price of a particular
level of PC technology declines by more than two-thirds every four years.
Looking at it another way, today's PCs are about 40 times as powerful as
machines of only five years ago, at about the same price. Bill Machrone, one of the
industry's leading analysts, describes this trend as what he calls "Machrone's Law":
The computer you want will always cost $5000. One could argue the magnitude of
the number, which depends partly on the choice of printers and other peripherals,
but the idea that a stable computer-equipment budget will yield increasingly capable
machines is indisputable. Machrone's reputation as an industry prognosticator
remains intact—especially when you consider that he coined the law in 1981!
Reasonably equipped PCs priced at under $1000 have become increasingly
common. Peripherals have reached commodity-pricing status. Even the micro-
processors themselves are experiencing price pressure. PCs based on new micro-
processors and other technologies rarely command a premium price for more than
a few months before competition forces prices into line. Meanwhile, product-gener-
ation half-lives have fallen to less than a year, less than 6 months for some critical
subsystems such as hard disk drives and CD-ROM readers and burners. Even flat-
panel liquid-crystal displays (LCDs), once exorbitantly expensive, are beginning to
replace conventional monitors—the last remaining tubes in common use.
Customers are forcing companies to cut manufacturing costs, while test costs
remain stable at best and rise dramatically at worst. Test costs today often occupy
one-third to one-half of the total manufacturing cost. Every dollar saved in testing
(assuming an equivalent quality level) translates directly to a company's bottom
line. For example, if manufacturing costs represent 40 percent of a product's selling
price (a reasonable number) and test costs represent one-third of that 40 percent,
then a strategy that reduces test costs by 25 percent reduces overall manufacturing
costs to 36.67 percent, a difference of 3.33 percent. If the company was making a
10 percent profit, its profit increases to 13.33 percent, a difference of one-third. No
wonder managers want to reduce test costs as much as possible!

1.3.2 Life Cycles

A successful test strategy is a by-product of overall life-cycle management. It
requires considering:

* Product development
* Manufacturing
* Test